JP2012083174A - Optical detection device and electronic apparatus with such optical detection device mounted thereon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an optical detection device which attains high accuracy and is realized at low cost giving less load on an electronic apparatus, and to achieve the electronic apparatus with the optical detection device mounted thereon.SOLUTION: An optical detection device 100 includes: a light to digital conversion circuit 102 which converts a current 110 obtained upon receipt of light at a light receiving element 101 to a first digital signal 111 and outputs it; a floating-point conversion circuit 107 which compresses the first digital signal 111 to floating-point data and outputs it as a second digital signal 112; a floating-point arithmetic circuit 108 which performs predetermined arithmetic on the second digital signal 112; and a floating-point to integer data conversion circuit 109 which converts a signal 113 indicating a result of arithmetic to a third digital signal 114 being integer digital data and outputs it.

Description

  The present invention relates to a digital output type photodetector.

  In electronic devices with display screens such as liquid crystal displays, such as mobile phones, smartphones, digital cameras, and tablet-type or stationary computers, the brightness of the display is adjusted according to the ambient brightness. A process for making the display screen easy to see and reducing the user's discomfort is performed. For such applications, the electronic device uses an illuminance sensor to detect ambient brightness in accordance with human visibility characteristics.

  In particular, in portable electronic devices such as mobile phones, smartphones, and digital cameras, various controls are performed based on the result of detecting the proximity of a human body to the electronic device. For example, in cell phones and smartphones, the display also serves as an information input function as a touch panel, and the information input function is turned off when an object comes close to the touch panel, such as during a call or when an electronic device is inserted into a pocket. Therefore, it is possible to control to prevent malfunction.

  In the digital camera, when the user moves his / her line of sight from the liquid crystal screen to the viewfinder, control is performed to automatically reduce the brightness of the liquid crystal screen.

  For such an application, the electronic device uses a proximity sensor that emits light by itself and detects reflected light from the object to determine the proximity of the object.

  There is a need for a digital output type photodetection device that can be easily controlled from the electronic device side for consumer electronic devices (consumer devices). In particular, in consumer products, the design is important, so that a housing window having an extremely low spectral transmittance in the visible light region is used so that the light detection device is hardly visible from the outside of the housing. Therefore, the photodetection device is required to be low in cost and high in sensitivity at the same time.

  Examples of conventional techniques related to a digital output type photodetection device disclosed with consideration of such applications include the techniques disclosed in Patent Document 1 and Non-Patent Document 1.

  As a configuration of the internal circuit of the photodetection device, for example, a so-called Light-to-Digital Converter that operates at a low speed as disclosed in Patent Document 1 can be used. In addition, as an example of realizing a low-cost illuminance sensor using the circuit technology disclosed in Patent Document 1, a technique disclosed in Non-Patent Document 1 can be given. In this document, without using an optical filter, the output currents of two types of photodiodes are digitized and output separately to the outside of the photodetection device, and these outputs are output on the side of the electronic device on which the photodetection device is mounted. Illuminance information is obtained by performing arithmetic processing on.

  Further, in an illuminance sensor whose main objective is to reproduce visibility well, an optical filter is usually integrated as a part of a light detection device. Also in this case, the circuit technique disclosed in Patent Document 1 can be used, and other circuit techniques can also be used.

US Pat. No. 6,635,5859 (published August 21, 2003)

TSL2771 LIGHT-TO-DIGITAL CONVERTER with PROXIMITY SENSING, TAOS Inc. (OCTOBER.2009)

  However, as in the technique disclosed in Non-Patent Document 1, if the use of an optical filter is avoided, there is a problem that the burden on the electronic device side that controls the photodetection device increases. In other words, in the case of the method disclosed in Non-Patent Document 1, since the output as illuminance is obtained after the arithmetic processing on the electronic device side, an interrupt output is generated from the light detection device side. It is difficult to notify the host system or the like that the desired illuminance level is obtained. For this reason, it is necessary for the electronic device to carry out the notification, which increases the burden on the electronic device. Further, if the spectral characteristic of the casing window of the electronic device is changed, it is necessary to re-optimize the arithmetic processing formula accordingly, resulting in a problem that the cost of the electronic device increases.

  Alternatively, when pursuing the accuracy of spectral characteristics using an optical filter, cost increases due to the optical filter are inevitable.

  The present invention has been made in view of the above problems, and its object is to provide a photodetection device and an electronic device equipped with the photodetection device that are highly accurate, low-cost, and less burdensome on electronic equipment. To provide equipment.

  In order to solve the above problems, the photodetection device of the present invention converts a light receiving element and a signal obtained by receiving the light into a digital signal, and outputs the first digital signal as a first digital signal. A digital signal output means; a second digital signal output means for compressing the first digital signal into floating point data having a bit width smaller than that of the first digital signal and outputting as a second digital signal; Arithmetic means for performing a calculation for correcting a relative error of the digital signal with respect to an ideal value; and a third digital signal output means for converting the result of the calculation into integer type digital data and outputting it as a third digital signal. It is characterized by providing.

  According to the above configuration, since the output value of the illuminance that can be referred to only by bit shift calculation (shift calculation) at most can be obtained as the third digital signal in the electronic apparatus that controls the light detection device, the electronic apparatus Can be reduced.

  In addition, according to the above configuration, the first digital signal output means has a minimum resolution depending on the accuracy, and the relative error of the output value of the illuminance with respect to the value of the output signal of the light receiving element (error expressed as a ratio) ) Can be maintained at a constant level over the entire dynamic range, and the increase in the scale of the calculation means can be suppressed and the cost can be reduced.

  In addition, by generating an interrupt signal from the light detection device at an arbitrary illuminance level, it is possible to achieve display brightness adjustment at a desired illuminance level of an electronic device equipped with the light detection device. Can be reduced. In addition, by realizing the arithmetic processing inside the light detection device, it is possible to easily correct the spectral characteristics of the light receiving element, the characteristics of the first digital signal output means, and the spectral characteristics of the housing window of the electronic device. it can.

  Furthermore, according to the above configuration, the second digital signal can be easily generated by converting the first digital signal into floating point data and performing compression.

  In the photodetector of the present invention, the bit width of the third digital signal is not less than the bit width of the second digital signal and not more than the bit width of the first digital signal.

  According to the above-described configuration, it is possible to suppress an increase in the arithmetic circuit of the light detection device, and thus the overall circuit scale.

  Further, the value of the third digital signal of the photodetecting device of the present invention is a value indicating the illuminance of the light received by the light receiving element or a value indicating the illuminance of the light received by the light receiving element by a shift calculation. Is a value that can be obtained.

  According to the above configuration, it is easy to obtain the illuminance of the light received by the light receiving element from the third digital signal. Therefore, the burden on the electronic device that controls the light detection device can be reduced.

  In the photodetector of the present invention, the light receiving elements are a plurality of photodiodes having different spectral characteristics, and the first digital signal output means is provided in the same number as the number of the plurality of photodiodes. It is characterized by being.

  According to the above configuration, it is possible to realize the photodetection device of the present invention without using an optical filter, and thus the cost of the photodetection device can be further reduced.

  In addition, the calculation means of the photodetecting device of the present invention performs a calculation for correcting a relative error of the second digital signal generated due to a variation in spectral characteristics of the light receiving element as the calculation. It is characterized by.

  In addition, the calculation means of the photodetection device of the present invention may be configured to calculate, as the calculation, a relative error of the second digital signal that occurs due to variations in characteristics of the first digital signal output means. It is characterized by performing.

  According to each of the above-described configurations, the calculation means can easily correct the relative error of the illuminance output value with respect to the output signal of the light receiving element.

  The photodetector of the present invention further includes a trimming correction circuit that selects a desired correction coefficient from a plurality of correction coefficients according to variations in spectral characteristics of the light receiving element by fuse trimming, and the calculation means includes As the calculation, a product of the second digital signal and the selected correction coefficient is calculated.

  The photodetection device of the present invention further includes a trimming correction circuit that selects a desired correction coefficient from a plurality of correction coefficients according to variations in characteristics of the first digital signal output means by fuse trimming, The calculating means calculates the product of the second digital signal and the selected correction coefficient as the calculation.

  According to each configuration described above, each trimming correction circuit can correct the relative error of the output value of the illuminance with respect to the output signal of the light receiving element by general fuse trimming, so that the correction can be performed very easily. Can do.

  The photodetecting device according to the present invention further includes a first trimming correction for selecting a desired first correction coefficient from a plurality of first correction coefficients determined according to variations in spectral characteristics of the light receiving element by fuse trimming. A circuit and a second trimming correction circuit that selects a desired second correction coefficient from a plurality of second correction coefficients determined according to variations in characteristics of the first digital signal output means by fuse trimming. The calculation means performs a calculation for correcting a relative error of the second digital signal generated due to a variation in spectral characteristics of the light receiving element as the calculation, and the first digital signal output means. Performing an operation for correcting a relative error of the second digital signal, which is caused by variation in characteristics of the second digital signal, and the selected digital signal A product of the first correction coefficient and the selected second correction coefficient is calculated, and the product of the first correction coefficient and the second correction coefficient is calculated in advance before calculating the product for the second digital signal. Is calculated.

  According to the above configuration, the member (table or the like) that stores the first correction coefficient by calculating the product of the first correction coefficient and the second correction coefficient and multiplying the product with the second digital signal. In addition, it is possible to integrate the members that store the second correction coefficient, and it is possible to easily mount these storage members on the integrated circuit of the photodetector.

  In addition, the light detection apparatus of the present invention includes a communication unit that performs communication with the outside, and a storage unit that holds digital data received via the communication unit, and the calculation unit includes the light receiving unit as the calculation. Correction coefficient determined in accordance with the variation of the spectral characteristics of the second digital signal and the light receiving element in order to correct the relative error of the second digital signal caused by the variation of the spectral characteristics of the element And a register correction unit that selects a desired correction coefficient from a plurality of correction coefficients based on digital data stored in the storage unit.

  In addition, the light detection apparatus of the present invention includes a communication unit that performs communication with the outside, and a storage unit that holds digital data received via the communication unit, and the calculation unit includes a plurality of photodiodes. For each of the calculations, the second digital signal and the spectral characteristics of the photodiode are corrected in order to correct the relative error of the second digital signal, which is caused by variations in the spectral characteristics of the photodiode. The product of the correction coefficient determined according to the variation is calculated, and the desired correction coefficient is selected from the plurality of correction coefficients for each of the plurality of photodiodes based on the digital data stored in the storage unit. And a register correction unit.

  According to each of the above-described configurations, it is possible to carry out calibration with respect to the absolute value of the sensitivity of the light receiving element as part of the initial setting when starting the light detection device from the outside. In particular, by configuring the arithmetic processing circuit so that calibration can be performed for each of the plurality of photodiodes, it is possible to absorb a large difference in spectral sensitivity characteristics in the infrared region.

  In the light detection device of the present invention, the illuminance of the light received by the light receiving element is a desired value based on a result of comparing the third digital signal with a first threshold set with illuminance as a unit. It is possible to determine whether or not it exists and to output the result of the determination to the outside.

  According to the above-described configuration, interrupt processing is dramatically simplified, and various unstable behaviors or malfunctions of an electronic device that are likely to occur due to a detection error of an interrupt signal or a delay in interrupt processing are reliably avoided. It is possible.

  Further, the first threshold value of the photodetecting device of the present invention is a value set from the outside and indicating a plurality of illuminances.

  The light detection device of the present invention includes a plurality of illuminance tables, each of the plurality of illuminance tables has a value indicating a plurality of illuminances as an element, and the first threshold is the plurality of illuminance tables. Among the illuminance tables, a part or all of the values constituting the elements of the illuminance table designated from the outside are characterized.

  According to the above configuration, it is possible to easily set the first threshold from the outside using an illuminance table or the like.

  The light detection device of the present invention further includes a light emitting element, and the light receiving element receives light obtained by reflecting light emitted from the light emitting element by an external reflector. Yes.

  The light detection device of the present invention is capable of detecting a distance to the reflecting object based on a result of comparing the determination result with a second threshold value set from the outside. It is said.

  According to the said structure, it becomes possible to comprise the proximity sensor which detects the distance to a reflective body using the photon detection apparatus of this invention.

  In addition, the light detection device of the present invention outputs the result of the determination to the outside when the result of the determination changes, and the result of the detection when the result of detecting the distance to the reflecting object changes. An output means for outputting to the outside is provided.

  According to the above configuration, by generating an interrupt signal from the light detection device at an arbitrary illuminance level, it is possible to adjust the display brightness of the electronic device including the light detection device at a desired illuminance level. Thus, the burden on the electronic device can be reduced.

  The light detection apparatus of the present invention further includes a first output means for outputting the determination result to the outside, and a second output means for outputting the result of detecting the distance to the reflector to the outside. It is characterized by.

  According to the above configuration, the first output means can be used exclusively for interrupt output as an illuminance sensor, and the second output means can be selectively used for output as a proximity sensor. Therefore, the output of the second output means includes either a proximity or non-proximity determination result or an interrupt output based on the determination result (that is, a state transition timing from proximity to non-proximity or from non-proximity to proximity). Can be output. Therefore, the delay time due to complicated interrupt processing fluctuates under various operating conditions in which the object moves closer and away while the surrounding brightness changes, and the detection distance of the proximity sensor apparently fluctuates. Unstable and undesired behavior can be reliably avoided.

  In addition, the electronic apparatus of the present invention includes the photodetection device of the present invention, thereby producing the same effect as the photodetection device.

  The electronic device of the present invention includes the light detection device of the present invention and a housing of the light detection device, and the housing is spectrally transmitted when at least one of visible light and near infrared light is incident. A window having a variable rate, and the arithmetic means of the light detection device corrects a relative error of the second digital signal, which is caused by a variation in spectral transmittance of the window, as the calculation. A product of the second digital signal and a correction coefficient determined in accordance with a variation in spectral transmittance of the window is calculated, and a register correction unit of the light detection device is held in a storage unit of the light detection device. The desired correction coefficient is selected from a plurality of correction coefficients based on the digital data.

  According to the above configuration, when the spectral transmittance of the optical window provided in the electronic device does not have a large wavelength dependency, the arithmetic processing for correcting the average transmittance from the outside can be easily executed at the initial setting of the operation. Therefore, even when the light detection device of the present invention is mounted on an electronic device having a housing design that is difficult to visually recognize from the outside through a black window having no color, the outside of the casing, that is, around the electronic device. The illuminance in real space can be obtained directly as the digital output of the photodetection device.

  As described above, the light detection device of the present invention includes a light receiving element, and a first digital signal output unit that converts a signal obtained by receiving the light into the digital signal and outputs the digital signal as a first digital signal. A second digital signal output means for compressing the first digital signal into floating point data having a bit width smaller than that of the first digital signal and outputting the compressed data as a second digital signal; and an ideal of the second digital signal. Computation means for performing a computation for correcting a relative error with respect to the value, and third digital signal output means for converting the result of the computation into integer digital data and outputting the result as a third digital signal.

  Therefore, the present invention has an effect of high accuracy, low cost, and small burden on the electronic device.

It is a circuit block diagram which shows the structure of the photon detection apparatus based on one embodiment of this invention. FIG. 2A is a diagram simply showing a known single-precision floating-point data format, and FIG. 2B is a diagram simply showing the format of the second digital signal as floating-point data. FIG. It is a circuit block diagram which shows the structure for performing the calculation by a floating point arithmetic circuit. It is a circuit block diagram which shows the specific structure of an arithmetic processing circuit. It is a circuit block diagram which shows the structure of the photon detection apparatus based on another embodiment of this invention. FIG. 6A is a graph showing the relationship between the wavelength of incident light and sensitivity in each photodiode, and FIG. 6B is an example of a pn junction for realizing each photodiode. FIG. It is a circuit block diagram which shows the structure of another optical detection apparatus based on another embodiment of this invention. FIG. 8A shows the spectral characteristic case (i) shown in FIG. 6A, and outputs from a plurality of photodiodes when the light sources having various different spectral spectra are standardized to give a constant illuminance. FIG. 8B is a graph showing the same relationship using the reciprocal of Ivis ′ and Ivis in the graph shown in FIG. 8A. It is a figure which shows an example of the illumination intensity threshold value table used in a photon detection apparatus. It is a circuit block diagram which shows the structure of the photon detection apparatus based on another embodiment of this invention.

  The form for implementing this invention is demonstrated below with reference to FIGS.

  However, the present invention is not limited to the following description, and it is easy for those skilled in the art to change the form and details in various ways without departing from the spirit and scope of the present invention. To be understood. Therefore, it should be understood that the present invention should not be construed as being limited to the description of each embodiment described below.

  In addition, in the structure of this invention demonstrated below, about the member which has the same function, it has shown using the same code | symbol, and detailed description of the member which has the same part or the same function is abbreviate | omitted.

[Embodiment 1]
A basic configuration of the photodetection device 100 according to the present embodiment will be described with reference to FIG.

  The light detection apparatus 100 includes a light receiving element 101, a light-digital conversion circuit (first digital signal output means) 102, and an arithmetic processing circuit 103. The light-digital conversion circuit 102 includes an integrator 104, a comparator 105, and a counter 106. The arithmetic processing circuit 103 includes a floating-point conversion circuit (second digital signal output means) 107, a floating-point arithmetic circuit (arithmetic means) 108, and a floating-point-integer type data conversion circuit (third digital signal output means) 109. It has.

  First, light whose intensity is to be detected (light from the periphery of the light detection device 100 or light obtained by reflecting light on an object, etc.) enters the light detection device 100 and is received by the light receiving element 101.

  The light receiving element 101 is composed of, for example, a photodiode, and performs photoelectric conversion on the received light to generate a current (a signal obtained by receiving the light received by the light receiving element) 110, thereby producing an optical-digital signal. Output to the conversion circuit 102.

  The current 110 input to the optical-digital conversion circuit 102 is subjected to a general waveform integration operation by the integrator 104, and compared with a threshold value (predetermined reference voltage) by the comparator 105. The result of this comparison In response to this, it is converted into a binary signal in which the logic of the high level and the low level is switched. Further, the binary signal is converted into a count value defined by the counter 106 in proportion to the value of the current 110 and output from the light-digital conversion circuit 102. The output of the light-digital conversion circuit 102 is a first digital signal 111 obtained by converting the current 110 into a digital signal (that is, known light-digital conversion).

  Note that as the configuration of the light-digital conversion circuit 102, any circuit capable of performing known light-digital conversion on the current 110 is applicable. The integration time for integrating the current 110 by the integrator 104 is a method of counting a clock signal generated inside the photodetector 100 or a clock signal input from the outside, or a timing signal input from the outside. It can be determined by the method used (not shown).

  Further, the first digital signal 111 is input to the arithmetic processing circuit 103, and a series of arithmetic processing described below is performed.

  First, the floating-point conversion circuit 107 converts the first digital signal 111 into a second digital signal 112 which is digital data in a floating-point format (floating-point data).

  Here, the data in the floating point format is a data format as defined in, for example, the IEEE754 standard.

  FIG. 2A shows a known single-precision floating point data format defined by the IEEE 754 standard (see member number 220).

  In the data format indicated by the member number 220, a total of 32 bits are used in the order of 1 bit as the sign bit 201, 8 bits as the exponent part 202, and 23 bits as the mantissa part 203 in order from the upper bit. Further, in the data format, details such as a method of adding an extra 3 bits and rounding the operation result are defined in order to maintain the accuracy of the operation.

  However, the photodetection device 100 is not limited to the above-mentioned regulations, and uses floating-point numbers (floating-point data) only as internal variables, as will be described below. Therefore, floating-point data of an arbitrary format can be used as the second digital signal 112, and the advantage of separating the output value, which is a digital signal, into an exponent part and a mantissa part, that is, accuracy and circuit scale. Use floating point numbers to balance.

  More specifically, various correction operations in the photodetecting device 100 refer to actual characteristics of each component of the photodetecting device 100 with respect to a design value or a typical value (ideal value) in the second digital signal 112. It is to calculate a product for correcting the deviation (that is, characteristic variation). Further, it is often necessary to repeat this product operation.

  Here, for example, when the first digital signal 111 output from the optical-digital conversion circuit 102 is 16-bit integer type data, in order to maintain the same accuracy when obtaining a product with a 16-bit constant, , 32 bits of data must be retained. In this case, the total circuit scale of the data path portion including the arithmetic circuit and the register of the light detection device 100 becomes very large with respect to the originally required accuracy, and as a result, the cost of the light detection device 100 increases.

  Here, as an example, the light detection device 100 is an illuminance sensor, and the illuminance sensor covers 0.01 Lux (Lux: SI unit of illuminance) to 100,000 Lux as the specification of the range of the input light level. think of. In this case, the fluctuation range of the input light level is at most 7 digits. Therefore, the number of digits of the input light level itself can be expressed in the order of binary 3 bits.

  The LSB (least significant bit) of the light-digital conversion circuit 102 corresponds to the resolution of the light-digital conversion circuit 102, but the resolution corresponds to detection of an input level of 0.01 Lux. What is important as the sensitivity specification of the illuminance sensor is the relative accuracy over the entire range that can be taken as the input light level.

  In other words, the sensitivity specification of the illuminance sensor is from 0.01 × 10 ^ −2 to 1.0 × 10 ^ 5, for example, from −10% to + 10% over the entire range of 0.01 Lux to 100,000 Lux. It is sufficient that the measurement can be performed with an accuracy of 0.01 lux, and an accuracy of 0.01 Lux is not necessary in the entire range. The above agrees well with the concept of floating point numbers.

  As described above, in the photodetecting device 100, the floating-point conversion circuit 107 converts the minimum necessary bits into the exponent part (digit number) and the mantissa part for the first digital signal 111 given by the bit width of the counter 106. Assign to (Accuracy). Then, the floating-point conversion circuit 107 compresses the bit width of the first digital signal 111, generates digital data to be arithmetically processed (that is, the second digital signal 112), and outputs it.

  Here, the bit width allocated to the mantissa is a required specification of the relative error of the output value of the illuminance with respect to the value of the current 110 (for example, the allowable error of the final illuminance output when any variation factor is considered is -10% + 10% range). In addition, the bit width allocated to the mantissa part needs to have a margin (allocating a bit width of the mantissa part larger) in consideration of the accumulation of errors that occurs every time the floating-point arithmetic processing is repeated.

  The minimum sensitivity or resolution as the illuminance sensor is determined by the LSB unit corresponding to the first digital signal 111, that is, the configuration of the light-digital conversion circuit 102. As long as the relative error is controlled as described above, the minimum sensitivity or resolution as the illuminance sensor does not depend on whether the data format of the second digital signal 112 is integer type data or floating point data.

  FIG. 2B shows an example of the format of the second digital signal 112 in the photodetection device 100 as floating point data determined in consideration of the above (see member number 210).

  The first digital signal 111 does not become a negative value due to the characteristics of the light-digital conversion circuit 102. Therefore, the bit indicating the sign in the second digital signal 112 is unnecessary.

  As an example, a dynamic range of 0.01 Lux to 100,000 Lux and an error within a range of −10% to + 10% after a maximum of two correction operations (details will be described later) are allowed as a relative error. In order to ensure a certain degree of accuracy, the second digital signal 112 has a bit width of 14 bits in total, that is, a 6-bit exponent part 212 and an 8-bit mantissa part 213.

  That is, according to the configuration of FIG. 1, the first digital signal 111 that is 16-bit integer data is converted by the floating-point conversion circuit 107 into the second digital signal 112 that is 14-bit floating point data. . As a result, the circuit scale of the floating-point arithmetic circuit occupying most of the arithmetic processing circuit 103 is compressed from 16-bit data (first digital signal 111) to 14-bit data (second digital signal 112). Only a limited bit width is suppressed.

  On the other hand, when the mantissa part 213 is 8 bits, the rounding error of the minimum digit in the second digital signal 112 is 1 / (2 ＾ 8), that is, 1/256 = approximately 0.4%. Therefore, in the second digital signal 112, a calculation error of about 0.8% at the maximum is expected by the two correction calculations.

  Actually, a measurement error (for example, within a range of −3% to + 3%) for determining a correction value in the correction calculation, or a quantization error of the correction value itself (for example, −5% to + 5%). Are corrected using the same correction value). From this, it is desired that the accumulated error of the calculation itself is sufficiently smaller than these various other errors, so that 8 bits are selected as the bit width of the mantissa part 213 as described above.

  Further, the second digital signal 112 obtained as described above is input to the floating point arithmetic circuit 108. The floating-point arithmetic circuit 108 calculates a product (predetermined calculation) for the second digital signal 112 to correct a deviation in actual characteristics with respect to a design value or a typical value of each component of the light detection device 100. And a signal 113 indicating the result of the calculation is output. Details of the calculation by the floating point arithmetic circuit 108 will be described later.

  The signal 113 indicating the calculation result is input to the floating-point-integer type data conversion circuit 109. The floating-point-integer type data conversion circuit 109 converts the signal 113 into integer type digital data again and outputs it as a third digital signal 114 for output to the outside of the photodetection device 100.

  The purpose of using the third digital signal 114 as integer type digital data is as follows. That is, there are cases where floating-point data is not supported in an electronic device for consumer, which is a host system of a device (for example, an illuminance sensor or a proximity sensor) mainly targeted for the light detection device 100. Even if it is supported, a single-precision or double-precision data format that complies with the highly versatile IEEE 754 standard considerably compresses the resources of the host system. For this reason, the third digital signal 114 is strongly desired to be integer type digital data.

  Next, the relationship of the bit width (unit bit width) between the first digital signal 111 and the third digital signal 114 will be described.

  For example, the bit width of the first digital signal 111 is 16 bits, and the bit width of the second digital signal 112 is 14 bits (exponential part 6 bits and mantissa part 8 bits).

  As described above, the pure error (error not including the measurement error and the quantization error of the correction value) included in the signal 113 indicating the calculation result of the second digital signal 112 is the total number of operations N × 1 / (2 ^ 8).

  In other words, when N = 2, log 10 ((2 ^ 8) / N) to 2.1. At this time, at least two significant digits are always secured in decimal notation for the signal 113. However, the maximum number of elements that can be expressed is 2 ^ 14.

  Assuming that the bit width of the third digital signal 114 is 16 bits, similar to the bit width of the first digital signal 111, 2 ^ 14 elements that can be output as the signal 113 are represented in the third digital signal 114. It will be redistributed into 2 ^ 16 bit spaces. As a result, the same data is degenerated in a certain range of bit space.

  However, the quantization error resulting from the redistribution is about N × 1 / (2 ＾ 8) at the maximum, and the number of significant digits is retained. As is apparent from the above description, the upper limit of this error is reduced by reducing the bit width of the third digital signal 114 to be equal to the total bit width of the second digital signal 112 (14 bits in this example). Is also maintained.

  Note that reducing the bit width of the third digital signal 114 requires a rounding process of digits, which is different from the calculation process by the floating-point arithmetic circuit 108, and is therefore large from the viewpoint of the overall circuit scale. There is no merit.

  As described above, it is desirable that the unit bit width of the third digital signal 114 is any one of the unit bit width of the second digital signal 112 and the unit bit width of the first digital signal 111. More preferably, the unit bit width of the third digital signal 114 is equal to the bit width of the first digital signal 111.

  As described above, the basic configuration of the photodetector 100 shown in FIG. 1 has the minimum resolution based on the accuracy of the light-digital conversion circuit 102, and the relative error of the output value of illuminance with respect to the value of the current 110. Is maintained at a constant level over the entire dynamic range, and an increase in the arithmetic circuit of the photodetecting device 100 and thus the overall circuit scale can be suppressed.

  Here, the optical-digital conversion circuit 102 can be designed in more detail as follows.

  For example, the light-digital conversion circuit 102 integrates a current 110 corresponding to 1 Lux of incident light with a constant integration time (eg, 100 ms), and then the output value (count) of the counter 106 is a power of 2 (eg, (2 ^ 4 = 16 counts), various analog circuit constants of the integrator 104 and the comparator 105, each of which is a known configuration, may be set.

  Of course, the count value is various factors, such as variations in sensitivity of the light receiving element 101, capacitance values of the integration circuit constituting the integrator 104 or variations in parasitic capacitance, gain error of the amplifier in the integrator 104, or comparator. It may vary due to variations in the threshold value of 105 or the like. However, these characteristic fluctuation factors are corrected so that desired precision can be obtained by configuring the floating-point arithmetic circuit 108 as shown in FIG. 3, for example, in the configuration of the photodetector 100 shown in FIG. However, it can be easily realized. This will be easily understood by those skilled in the art from the above description and the following description.

  With respect to the light receiving element 101, the relative value of the sensitivity of the light receiving element 101 with respect to a typical design value of the light receiving element having the same configuration can be measured in the wafer manufacturing process of the integrated circuit for realizing the light detection device 100. . On the other hand, it is not easy to measure the absolute value of the sensitivity of the light receiving element 101.

  As an example of measuring the relative value of sensitivity of the light receiving element 101, when the light receiving element 101 is irradiated with test light calibrated to a constant light amount level, the measured value of the current 110 is the design value of the light receiving element 101 or a large number of values. Consider a case where the average value (typical value) measured with a typical light receiving element has decreased to 80%. In this case, the correction of the relative error occurring in the output value of the illuminance due to the characteristics of the light receiving element 101 is equivalent to increasing the current 110 by 25% (that is, 1 / 0.8 = 1.25). This is done by designing the integrated circuit to calculate the product with the second digital signal 112 in FIG. 1 using the correction coefficient (first correction coefficient) to be used.

  Here, the expression “using a correction coefficient corresponding to...” Is intended to use a uniform correction coefficient within a certain range of relative sensitivity. This is a very general technique when performing fuse trimming using the.

  Specifically, for example, when the measured value of the current 110 is in the range of 70% to 90% with respect to the typical value, a correction factor that is 1.25 times uniform is used for the measured value. To do. Further, when the measured value is in the range of 110% to 130% with respect to the typical value, a correction coefficient of 1 / 1.2 = 0.83 times is uniformly used for the measured value. I will decide. When the measured value is in the range of 90% to 110% with respect to the typical value, the correction coefficient is set to 1, that is, the measured value is not corrected. This is a configuration example of the simplest correction coefficient table when a maximum variation width (−3σ to + 3σ) of −30% to + 30% is expected as a relative error in the current 110. The corrected sensitivity of the light receiving element 101 falls within a range of −10% to + 10% with respect to the typical value.

  The trimming correction circuit (first trimming correction circuit) 115 of the light receiving element 101 shown in FIG. 3 includes a sensitivity trimming unit 115a of the light receiving element 101 and a correction coefficient table 115c used for sensitivity trimming of the light receiving element 101. Although not shown, the sensitivity trimming unit 115a includes at least three (1.6 bits) trimming fuses, a sense circuit that senses (measures) whether or not each trimming fuse is cut, and a trimming that indicates a sense result. A decoding circuit for decoding the bit information.

  Correction of any of {1.25, 1, 0.83} in an example (described above) using each element of the correction coefficient table 115c, that is, the correction coefficient, according to the decoding result (see member number 115b) by the decoding circuit A coefficient is selected. Then, the selected correction coefficient is supplied to the floating point arithmetic circuit 108 as a signal 115 d indicating the correction coefficient, and is used for the product operation in the floating point arithmetic circuit 108.

  In addition, the relative error generated in the output value of illuminance due to the characteristics of the light-digital conversion circuit 102 can be corrected in exactly the same manner.

  That is, as an example for correcting the characteristic of the light-digital conversion circuit 102, in a step different from the correction related to the sensitivity of the light receiving element 101 in the wafer manufacturing process of the integrated circuit for realizing the photodetector 100, By designing the integrated circuit so that a constant test current can be applied to the integrator 104 from the outside instead of the current 110 in a state where the light receiving element 101 is not irradiated with the test light (dark state). Is called. Alternatively, the test current may be obtained by trimming a current separately generated inside the light detection device 100.

  The test current calibrated to a certain level as described above is integrated into the integrator 104 with the same integration time as that in the actual operation as the test-dedicated operation mode of the light detection apparatus 100, and converted into a count value by the counter 106. Thus, it is very easy for those skilled in the art to generate a digital signal. For example, if the test-dedicated operation mode is designed so that the output of the counter 106 at this time can be read from the outside of the light detection apparatus 100, the characteristics of the light-digital conversion circuit 102 can be compared with typical design values. The misalignment can be easily known.

  The trimming correction circuit (second trimming correction circuit) 116 illustrated in FIG. 3 includes a trimming unit 116a and a correction coefficient table 116c. Although not shown, the trimming unit 116a includes a trimming fuse, a sense circuit that senses whether or not the trimming fuse is cut, and a decode circuit that decodes trimming bit information indicating the sense result.

  It is assumed that 2-bit trimming using two trimming fuses is performed in the same manner as in the case of correcting the sensitivity of the light receiving element 101. In this case, for example, if the measurement value (sensitivity) of the output of the light-digital conversion circuit 102 is within a range of 70% to 90% with respect to a typical design value, trimming associated with the measurement result is performed. The fuse is blown. Then, based on the decoding result (see member number 116b) obtained with this cutting, {1.25}, that is, a correction factor of 1.25 times (second correction) from the correction factor table 116c of the optical-digital conversion circuit 102. Coefficient) is selected. During actual operation of the photodetection device 100, a correction factor of 1.25 times is supplied to the floating point arithmetic circuit 108 as a signal 116d indicating the correction factor as a correction value corresponding to the characteristics of the light-digital conversion circuit 102. And used for product operation in the floating point arithmetic circuit 108.

  As described above, the meaning of the trimming bit is that the correction coefficient for correcting the deviation of the actual characteristic of the member constituting the photodetecting device 100 from the design value or the typical value in the second digital signal 112 is the same. This is equivalent to selecting each correction coefficient corresponding to the member from the stored correction coefficient table. The number of trimming bits and the correction coefficient table can be arbitrarily designed and integrated in an integrated circuit for realizing the photodetector 100.

  Further, as is clear from the above description, the calculation for correcting the light receiving element 101 and the calculation for correcting the light-digital conversion circuit 102 can be performed simultaneously.

  That is, in the wafer manufacturing process of the integrated circuit for realizing the photodetector 100, the relative sensitivity of each of the light receiving element 101 and the light-digital conversion circuit 102 (that is, the ratio of the measured output value to the typical design value). ) And then the product of their relative sensitivities. Then, it is possible to use trimming bit information and a correction coefficient table that are integrated in advance so that calculations for correction can be performed collectively using this product.

  Further, during the actual operation of the light detection apparatus 100, one correction coefficient is used as a value for correcting the sensitivity of the light receiving element 101 and the light-digital conversion circuit 102 (that is, all at once in one calculation cycle). The integrated circuit can be designed so that a correction operation is performed.

  Of course, the integrated correction coefficient table is larger than the correction coefficient table 115c or 116c before the integration. However, the integrated correction coefficient table is almost the same as the total circuit scale of the correction coefficient tables 115c and 116c before the integration, and the integrated correction coefficient table is better unless the number of coefficient elements is very large. The mounting on the integrated circuit is easy.

  All the correction coefficients are shown in decimal notation with three significant digits. However, in an actual integrated circuit, the nearest neighbor expressed in binary floating-point number in accordance with the format of FIG. 2B. Needless to say, it should be implemented as a value.

  Furthermore, another useful calculation method will be described with reference to FIG.

  In the digital output type illuminance sensor, in general, the integration time by the integrator, the sensitivity (or gain) of the comparator, and / or the maximum illuminance range can be set by a register from the outside of the illuminance sensor. Is often done. Usually, a host device equipped with such a light detection device that is an illuminance sensor reads an output (count value) of a digital signal from the light detection device (illuminance sensor), and then performs an operation in consideration of the various settings ( By performing multiplication or division for scaling, or addition and subtraction if necessary, the output needs to be converted into a value indicating illuminance.

  On the other hand, as is apparent from the description so far, the photodetecting device 100 determines its own operating conditions from the host system according to the contents set in the register. The photodetection device 100 is configured to internally execute calculations according to the various settings and output the calculation results to the outside.

  Specifically, a well-known serial interface such as an I2C bus communication path can be used as the external communication means 117 shown in FIG.

  The control unit (storage unit) 118 of the communication unit 117 includes a control circuit for communication itself by the communication unit 117. In addition, the control unit 118 can be written (received) at least from the outside, can be referred to from the inside of the light detection device 100, and can be read from the outside, and can be written from the inside of the light detection device 100. And.

  The communication means 117 and its control unit 118 can be realized by a well-known conventional technique.

  In this manner, the output such as the gain and integration time of the integrator 104 set from the outside (host system) is linearly scaled to change the sensitivity and dynamic range. Regarding the setting for the change, the control unit 118 can generate a signal 118b corresponding to the decode signal at the time of the fuse trimming and select an appropriate scaling factor from the scaling factor table 118c.

  Note that FIG. 3 shows an example in which the scaling is performed together with the generation of the third digital signal 114 in the floating point-integer type data conversion circuit 109. As described above, for example, after integrating the current 110 corresponding to 1 Lux of incident light for a certain period of time, the various values of the integrator 104 and the comparator 105 are set so that the output value of the counter 106 becomes a power of 2. This is because analog circuit constants can be designed. Further, the deviation from the design value or the typical value can be corrected with sufficient accuracy by the other correction calculation described with reference to FIG.

  That is, in the photodetection device 100, it is desirable to design the register settings for changing the sensitivity and dynamic range so that the values can be changed by a power of two. With such a configuration, all the scaling for setting the operating condition can be easily realized in the floating-point-integer type data conversion circuit 109 as a bit shift operation (shift operation) on a binary integer value.

  FIG. 4 shows an example of a block diagram of the entire arithmetic processing circuit 103 for realizing the arithmetic processing described above.

  The first digital signal 111 is input to the floating-point conversion circuit 107, that is, the integer-floating-point conversion circuit via a selector (shown in a trapezoidal form) not shown in FIG. 1, and is shown in FIG. Floating point data, ie, the second digital signal 112.

  In the description of the embodiments so far, the selector in the previous stage of the floating-point conversion circuit 107 does not play any role, but switches between two systems of first digital signals (first digital signals 111A and 111B described later). And used for inputting to the floating-point conversion circuit 107 (dotted arrow). Details will be described later in [Embodiment 2].

  Next, the second digital signal 112 is input to the data register group 401 again via another selector.

  The example of the arithmetic processing circuit 103 shown in FIG. 4 is an example in which the various product operations described above are executed serially in order to reduce the circuit scale.

  In order to load the input second digital signal 112 and store each calculation result for that, for example, when there are two systems of first digital signals, the data register group 401 has two systems × 2 That is, a total of four data registers having the same bit width as the second digital signal 112 are provided.

  In the second digital signal 112, the product calculation (correction calculation) itself for correcting the deviation of the actual characteristic of each component of the light detection device 100 with respect to the design value or the typical value is performed by the floating-point multiplier 402. The result is stored in one of the data registers of the data register group 401 for each product operation. This series of operations (arithmetic processing) is continued until all product operations are completed.

  Note that the input / output data of the floating-point multiplier 402 does not necessarily need to be stored in a specific data register with the input / output distinguished when stored in the data register group 401.

  When a series of arithmetic processing is completed while using the four data registers properly, the data is selected by the selector as shown in the figure from the data register storing the data 113 indicating the final operation result. , And output to the floating-point-integer type data conversion circuit 109.

  A specific example of the arithmetic processing thereafter will be described in [Embodiment 2].

  Further, whether or not it is necessary to generate any interrupt output or alert to the outside of the light detection device 100 with respect to the final calculation result (or the result obtained by converting it to the third digital signal 114), Judgment is made by a floating-point subtracter / determination unit 403.

  The floating-point subtracter / determination unit 403 calculates the difference between the specific threshold value 404a selected from the threshold value table 404 including the correction coefficient tables 115c and 116c shown in FIG. 3 and the final calculation result 405 as a floating-point number. Obtained by subtractor. Then, the floating-point subtracter / determination unit 403 determines whether the final calculation result 405 is data to be output to the outside as the third digital signal 114 based on the magnitude relationship of the subtraction results. A determination result 406 is output from the determination device. At the same time, in the floating-point-integer type data conversion circuit 109, the floating-point-integer value conversion already described, or bit shift as necessary, immediately before the output of the interrupt from the light detection device 100 to the outside. It is desirable that the calculation has been completed.

  Details of the interrupt output will be described in [Embodiment 3].

  As described above in detail with reference to FIGS. 1 to 4, the basic configuration of the light detection device 100 has the minimum resolution according to the accuracy of the light-digital conversion circuit 102, and the illuminance with respect to the value of the current 110. While maintaining the relative error of the output value at a constant level over the entire dynamic range, it is possible to suppress an increase in the arithmetic circuit of the photodetecting device 100 and thus the overall circuit scale.

  Further, since various characteristics correction and scaling according to the operating condition setting are realized inside the apparatus, a physically meaningful digital output value (that is, an illuminance output value) is finally obtained outside the light detection apparatus 100. Can be obtained directly or only by a bit shift operation.

  This has an extremely excellent effect that an illuminance value in units of Lux can be obtained directly without performing a complicated calculation, particularly in an illuminance sensor.

  More specific examples relating to this will be described in detail in the following [Embodiment 2].

[Embodiment 2]
In the present embodiment, a configuration of a photodetection device 200, which is another configuration example of the photodetection device 100, will be described with reference to FIG.

  The main difference between the light detection device 200 and the light detection device 100 is that a plurality of photodiodes having different spectral sensitivity characteristics are used as the light receiving element 101. Here, two types of photodiodes (light receiving elements) 101 </ b> A and photodiode 101 </ b> B are used as the light receiving elements 101.

  Corresponding to the difference, the light-digital conversion circuit 102 includes two integrators 104, a comparator 105, and a counter 106, respectively, that is, two systems of light-digital conversion circuits, that is, light-digital conversion. Circuits 102A and 102B are used. The light-digital conversion circuit 102A outputs the first digital signal 111A. The light-digital conversion circuit 102B outputs the first digital signal 111B.

  The purpose of the configuration shown in FIG. 5 is to realize a light detection device that uses the optical filter-less light receiving element 101, which is a well-known cost reduction measure, as described above, while greatly reducing the burden on the host system. is there.

  Here, first, spectral sensitivity characteristics to be imparted to the plurality of photodiodes will be described with reference to FIGS. 6 (a) and 6 (b).

  Photodetection devices such as illuminance sensors and proximity sensors are required to have high sensitivity over the visible light wavelength band or near-infrared light wavelength band.

  In particular, using an inexpensive Si (silicon) photodiode, the human visual sensitivity characteristics are approximately reproduced, so that a photodiode having a peak sensitivity to visible light and a sensitivity to near infrared light A technique using a photodiode having a structure having a peak is known. The Si photodiode typically has a sensitivity peak in the vicinity of a wavelength of 900 nm, and has a sensitivity over a wavelength range of approximately 300 nm to 1100 nm. The human visibility characteristic generally has a sensitivity peak at a wavelength of 555 nm, and has a sensitivity from a wavelength of 400 nm to a wavelength of 700 nm. In the above technique, correction is performed in consideration of the originally broad infrared spectral response characteristics of Si using the sum, difference, or ratio of the output currents of both photodiodes, and the spectral characteristics of the photodetection device are changed to the visibility characteristics. Move closer to. This technique is well known from the technique disclosed in Non-Patent Document 1.

  Further, in a general CMOS (Complementary Metal Oxide Semiconductor) manufacturing process, pn junctions of various depths can be used. As shown in FIG. The spectral characteristics of each photodiode can be realized by using pn junctions having different depths.

  FIG. 6A is a graph showing the relationship between the wavelength (horizontal axis) of incident light and sensitivity (vertical axis: indicated by current / power) in the photodiodes 101A and 101B. FIG. 6B is a diagram illustrating an example of a pn junction for realizing the photodiodes 101A and 101B.

  However, in a high-sensitivity photodetector in which the output current of the light receiving element 101 is on the order of pA, a bias voltage other than 0 V is applied to the pn junction portion of the light receiving element 101 in either the forward direction or the reverse direction. In this case, a leak current (dark current) on the order of nA may be generated. For this reason, the structure of the pn junction that can be used, that is, the spectral characteristics of the light receiving element 101 and the circuit configuration of the integrator 104 are limited.

  For example, FIG. 6B shows two pn junctions 604 formed by P + 601 which is a region having a high concentration of p-type impurities, NW602 which is an n-type well, and Psub 603 which is a p-type substrate. This is an example using 605.

  The photodiode 101B is formed using only the junction 605 between the NW 602 and the Psub 603, which is the deeper one of the junctions 604 and 605. In this case, the photodiode 101B has a spectral sensitivity characteristic (dotted line) having a peak in the vicinity of a wavelength of 900 nm. Normally, the potential of Psub 603 is fixed at the lowest potential, and the junction 604 between P + 601 and NW 602, which is the shallower one of the junctions 604 and 605, is invalidated by short-circuiting between both terminals. Therefore, the output current of the photodiode 101B is a sink current from the NW 602 (see case (i) 101B in FIG. 6A).

  On the other hand, it is ideal that the photodiode 101A is originally formed using only the shallow junction 604 and has a spectral sensitivity characteristic (dashed line) having a peak near a wavelength of 550 nm. However, if the NW 602 is fixed at the lowest potential similar to that of the Psub 603 so that the deeper junction 605 does not contribute to the shallower junction 604, the output current of the photodiode 101A is the same as the sink current of the photodiode 101B. Then you can not take it out. In this case, as the output current of the photodiode 101A, the source current from P + 601 is taken out (see case (i) 101A in FIG. 6A).

  Therefore, depending on the design of the integrator 104, the circuit configurations of the integrators 104A and 104B may need to be different from each other in accordance with the photodiodes 101A and 101B.

  In order to avoid such a limitation, the two pn junctions 604 and 605 shown in FIG. 6B can be used as follows.

  That is, the photodiode 101A sinks the sum of the currents from the two pn junctions 604 and 605. On the other hand, the photodiode 101B uses only the sink current from the junction 605 as in the case (i) (see the case (ii) 101B in FIG. 6A) (the case (in FIG. 6A) ii) See 101A).

  In this case, the same circuit configuration can be used for the integrators 104A and 104B. As will be apparent from the following detailed description, as described above, the light receiving element 101 having a structure capable of providing different spectral characteristics without using an optical filter is of course changed to a normal CMOS process or For the light receiving element 101 to which a relatively low-cost optical filter is added, which can be integrated by providing an additional process, or for the integrator 104 of any circuit configuration, the above-mentioned considerations are also possible. Thus, the light detection device 200 works effectively.

  By the way, the inventors of the present application know that the lowest-cost spectral calculation method is applied to the configuration of the photodetecting device 100 described with reference to FIGS. So far, no suggestions or disclosures have been made.

  This is a high-sensitivity realization capable of measuring, for example, 0.1 Lux or less and a high resolution of handling 16-bit digital data in a consumer photodetection device that is always required to be low-cost. This is because it is incompatible with the implementation depending on the built-in arithmetic processing. In particular, floating point arithmetic has always been avoided from the viewpoint of circuit scale. As a result, calculation processing and interrupt processing on the host side must be allowed to be complicated, or an increase in cost due to integration of optical filters must be approved.

  As described in detail in [Embodiment 1] with respect to the arithmetic processing required for the optical filter-less operation, it is only possible to configure the entire photodetection device optimally according to the application and / or specifications. The configuration of the photodetection device 200 shown in FIG. 5 is practical, and the following special effects can be obtained.

  The spectral sensitivity characteristic as shown in FIG. 6A is a so-called typical value, and is not applied to all the photodiodes included in each photodetection device. In addition, it is rare that the spectral characteristics assumed in the design stage of the photodetector are completely coincident with the spectral characteristics obtained most stably when mass-producing the photodetector. Further, consider a case where correction is performed in consideration of the spectral response characteristic of Si, which is originally broad, and the visibility characteristic, that is, the response to visible light is controlled. In this case, the spectral characteristics of infrared light that penetrates deeper in the thickness direction of the Si wafer greatly depend on the impurity concentration contained in the Si wafer, heat treatment for segregating impurities, heat treatment in a normal manufacturing process, or the like. Needs to be addressed.

  That is, in practice, it is difficult to reliably deal with such a problem only by the arithmetic processing for correcting the relative variation error distributed around the typical value as described in the first embodiment. It is.

  As means for solving the above problem, a floating point arithmetic circuit 108 can be configured as shown in FIG. It should be noted that FIG. 7 and the following description are described for the signal channel on one side in FIG. 5 (that is, one of the currents 110A and 110B) for simplicity.

  In the circuit shown in FIG. 7, the calculation itself for either the current 110A or 110B is performed in exactly the same way as the circuit described in [Embodiment 1]. The important point here is that, in the circuit shown in FIG. 7, typical spectral characteristics of a photodiode having a specific structure used as the light receiving element 101 fluctuate at the design stage of the light detection device 100. The fact that the absolute value of the sensitivity of the element 101 can deviate from the assumed value is taken into the correction processing process of the light detection apparatus 100 in advance.

  Specifically, in order to perform an operation for correcting the absolute value of the light receiving sensitivity of the light receiving element 101, the relative light receiving sensitivity trimming correction circuit 115 and the characteristic trimming correcting circuit 116 of the integrator 102 already described in FIG. In addition, a register correction unit 701 is newly provided. Actually, the trimming correction circuits 115 and 116 correspond to the light receiving elements 101A and 101B according to the configuration of FIG. 5 and the trimming correction circuits 115 and the light receiving elements 101A and 101B for the light receiving elements 101A and 101B, respectively. Note that a trimming correction circuit 116 is provided for each of them (not shown).

  The register correction unit 701 of the light receiving element 101 includes a trimming correction coefficient table 701c. Further, the register correction unit 701 uses a signal 701b to read from the correction coefficient table 701c based on data written from the outside to a register (not shown) that is a part of the control unit 118 by the communication means 117 with the outside. A desired correction factor is selected. The selected correction coefficient is supplied as a signal 701d to the floating point arithmetic circuit 108, and as a correction value by register setting of the light receiving element 101, separately from the trimming correction related to the characteristics of the light receiving element 101, the floating point arithmetic circuit 108. Used for product operations.

  Here, the correction related to the sensitivity of the light receiving element 101 by the above register setting is performed for each of the specific photodiodes having different structures having a plurality of (two types in this embodiment) spectral characteristics. It is desirable that it can be set independently. For this reason, FIG. 7 shows that the signal 701b for selecting the register correction coefficient and the signal 701d indicating the correction coefficient used in the floating point arithmetic circuit 108 are parallel data corresponding to the light receiving elements 101A and 101B. (Register correction unit 701 is shown as corresponding to two light receiving elements 101A and 101B).

  With such a configuration, the absolute value of the sensitivity of the light receiving element 101 can be calibrated as part of the initial setting when the photodetection device 100 is activated from the outside. In particular, the arithmetic processing circuit 103 can be configured so that calibration can be performed for each of a plurality of photodiodes having different structures, and the above-described large variation in spectral sensitivity peculiar to the infrared region can be absorbed and corrected correctly. become.

  In this way, the calculation for correcting the sensitivity of the light receiving element 101 in the second digital signal 112 can be controlled by setting the register from the outside. However, the control content is the same for all photodetectors 100 of the same design. Is sufficient as a uniform initial setting value. This is because, as described in [Embodiment 1], the relative error correction has already been measured and corrected at the shipping stage of the photodetecting device 100.

  Therefore, in the manufacturing process of the photodetecting device 100, sudden or extreme due to the fact that the correct typical value or the upper and lower limits of the fluctuation range (variation) of the characteristics of the light receiving element 101 could not be grasped at the design stage. The risk of a decrease in yield can be eliminated.

  As described above, according to the configuration of FIG. 5 or FIG. 7, the photodetector according to the present embodiment has the minimum resolution based on the accuracy of the light-digital conversion circuit 102 and has the current 110 (currents 110A and 110B). While the relative error of the output value of the illuminance with respect to the value is maintained at a constant level over the entire dynamic range, an increase in the arithmetic circuit of the photodetecting device 100, and hence the overall circuit scale, can be suppressed.

  Furthermore, various characteristic corrections and scaling can be easily realized, so that finally, outside the light detection device, a physically meaningful digital output value (that is, an illuminance output value) can be subjected to complex calculations. However, it can be obtained directly or only by a bit shift operation.

  In particular, according to the configuration of the photodetecting device according to the present embodiment, the variation in spectral sensitivity characteristics in the infrared region of the light receiving element 101, which is a problem in the illuminance sensor without an optical filter, is absorbed and corrected correctly, and Lux It is possible to directly obtain the illuminance value in units of. As a result, as will be described in detail in [Embodiment 3], a further effect of the photodetecting device regarding the threshold setting of the interrupt output is brought about.

  Next, the photodetection device 200 includes the arithmetic processing described with reference to FIGS. 1 to 4 using the photodiodes 101A and 101B having the configuration of FIG. 5, that is, two different spectral sensitivity characteristics. How to operate as a more accurate illumination sensor will be described.

  FIG. 8A shows the photodiodes 101A and 101B when the light source having various spectral spectra is normalized so as to give a constant illuminance in the spectral characteristic case (i) shown in FIG. 6A. The example of the electric current output from is shown.

  As a general light source, A, D50, D55, D65, D75, F1, and F12, which are standard lights defined by the CIE (Commission Internationale de I'Eclairage), should be considered at least. . For each light source having a relatively strong infrared component, such as A, D50, D55, D65, and D75, the spectrum in the infrared region not defined by the CIE is complemented in consideration of the color temperature. Considered as pseudo-standard light (ie, an approximate model of a regular light source). In FIGS. 8A and 8B, pseudo standard light is displayed with dots with white dots or white dots.

  The horizontal axis of FIG. 8A represents the ratio between the output current of the photodiode 101A (hereinafter referred to as Ivis) and the output current of the photodiode 101B (hereinafter referred to as Iir), that is, r (= Iir / Ivis). It is. An A light source (A ′ light source) having a low color temperature is located at the right end of the figure, and various F light sources not including an infrared component are located on the left side.

  Naturally, the output Iir of the photodiode 101B having a sensitivity peak in the infrared region (wavelength 900 nm) increases monotonously and rapidly as the ratio r increases.

  On the other hand, the output Ivis of the photodiode 101A having a sensitivity peak in the visible region (wavelength 550 nm) reflects the low sensitivity in the infrared region and increases very slowly in the region where r is large.

  In either Iir or Ivis, r = Iir / Ivis is small, reflecting the difference in color rendering properties of various F light sources (see F7 to F9) and the difference in spectral structure such as three-wavelength emission type F10 to F12. As a result, the output current also decreases. In addition, there is a region where Ivis hardly changes around r = 1.

  In consideration of the characteristics of the graph shown in FIG. 8A, the calculation for outputting the value corrected to the unit: Lux as the illuminance by canceling the dependence on the light source spectrum spectral characteristics will be described below. The knowledge described is obtained. Since the reciprocal 1 / Ivis of Ivis shown in FIG. 8B is an amount proportional to the correction coefficient in the calculation, it should be referred to simultaneously.

  The ratio r = Iir / Ivis can be used to distinguish the spectral characteristics of the light source (the relative content of the short wavelength components of the infrared and visible light components). The arithmetic expression to be used is switched depending on the value of r, and the correction expression used in each region can be expressed sufficiently by a linear expression at most.

  That is, the coefficients α and β of the correction equation Lux = α · Ivis−β · Iir = α · Ivis · (1−β / α · r) may be switched for each region distinguished by the r.

  In particular, as in the case (i) shown in FIG. 6A, when the spectral sensitivity peak (wavelength 550 nm) of the photodiode 101A substantially matches the peak of the visibility characteristic (wavelength 555 nm), r = The correction depending on the value of r may not be performed around 1 (for example, α = 1, β = 0 when 0.7 ≦ r ≦ 1.5). In FIG. 8B, each correction primary expression is illustrated by a broken line in three regions so that the correction coefficient switching by r can be easily understood.

  The arithmetic circuit using the correction formula extracted in this way is designed and implemented as the arithmetic processing circuit 103 shown in FIG.

  The actual operation of the photodetector 200 is that the output currents Ivis and Iir of the photodiodes 101A and 101B, that is, the currents 110A and 110B, are the first digital signals 111A and 111B, and further the second digital signal 112A that is a floating point. And 112B, and the area switching determination by r is to be performed.

  This can be executed by the floating-point arithmetic circuit 108 using, for example, the floating-point multiplier 402, the floating-point subtracter / determination unit 403, and the data register group 401 shown in FIG.

  In this way, by optimally designing the coefficient of the correction equation, the dependence of the output (illuminance value) on the various light source spectra can be kept within a range of −20% to + 20%.

  Further, when the spectral characteristics as in the case (ii) of FIG. 6A are given (when the peak of the spectral sensitivity characteristics of the plurality of photodiodes is out of the peak of the visibility characteristics), Using the ratio of the output current of the photodiode 101A (hereinafter referred to as Iall) to the output current of the photodiode 101B (hereinafter referred to as Iir), R = Iir / Iall (0 ≦ R ≦ 1) as an index, the above case ( In the same procedure as in i), a correction equation for Iall having a spectral characteristic closer to the visibility characteristic can be newly extracted, and light source dependency can be suppressed.

  Here, the coefficients α and β of the correction equation are actually relative to the light receiving element 101 described in FIGS. 1 to 4 with respect to each of the plurality of photodiodes 101A and 101B as the light receiving element 101. Includes all trimming correction (α1) related to sensitivity, trimming correction (α2) related to the light-digital conversion circuit 102 to which the light receiving element 101 is connected, and register correction (α3) related to the sensitivity of the light receiving element 101 described in FIG. Thus, a desired correction coefficient can be expressed in the form of product operation, such as α = α1, α2, α3, or β = β1, β2, β3. This series of product operations can be easily executed by the configuration of the arithmetic processing circuit 103 shown in FIG. 4 or FIG. 7. Finally, by calculating a difference of α · Ivis−β · Iir, A signal 113 which is a calculation result for the digital signal 112 is obtained.

  Also, it will be apparent from the above description that a product operation of the scaling factor γ can be easily added to the calculation result, such as Lux = γ (α · Ivis−β · Iir).

  As a result, when the spectral transmittance of the optical window provided in the electronic device on which the photodetecting device 200 is mounted does not have a large wavelength dependency, arithmetic processing for correcting the average transmittance from the outside can be easily performed at the initial setting of the operation. Can be executed. Accordingly, even when the light detection device 200 is mounted on an electronic device having a housing design that is difficult to visually recognize from the outside through a black window having no color, the real space outside the housing, that is, around the electronic device. The illuminance at can be directly obtained as a digital output of the light detection device 200.

  Alternatively, an optical window provided in an electronic device on which the light detection device 200 is mounted may be colored according to the body color. Furthermore, in the light detection device 200 integrated as a proximity illuminance sensor, a so-called near infrared LED (Light Emitting Diode) having a peak output at a wavelength of about 830 nm to about 950 nm is used as a light emitting element of the proximity sensor. Often used.

  As a result, in the near-infrared wavelength range, the transmittance is high (for example, the transmittance is about 80% to 95%), and in the visible wavelength range, in order to add a color that matches the body color, A window material whose spectral transmittance changes abruptly in the wavelength range of visible light can be used.

  Also in this case, among the coefficients α, β, and γ of Lux = γ (α · Ivis−β · Iir), a relatively sensitive photodiode in the visible region (in the example of FIG. 5, the photodiode 101A). By optimizing the correction coefficient α3 selected by register setting among the correction coefficients α = α1, α2, and α3, and further correcting the correction coefficient that can be independently set for β or γ if necessary. The illuminance in the real space outside the housing, that is, around the electronic device can be adjusted so as to be obtained directly as the digital output of the light detection device 200.

  As described above, according to the configurations of FIGS. 5 to 8, the photodetector according to the present embodiment has the minimum resolution based on the accuracy of the light-digital conversion circuit 102 and the output value of illuminance with respect to the value of the current 110. Is maintained at a constant level over the entire dynamic range, and an increase in the arithmetic circuit of the photodetecting device 100 and thus the overall circuit scale can be suppressed.

  Furthermore, various characteristic corrections and scaling can be easily realized, so that finally, outside the light detection device, a physically meaningful digital output value (that is, an illuminance output value) can be subjected to complex calculations. Or can be obtained only by a bit shift operation.

  In particular, by optimizing the arithmetic processing circuit using multiple photodiodes with different spectral sensitivity characteristics as light receiving elements, high sensitivity and light source as an illuminance sensor based on inexpensive photodiodes without optical filters A photodetection device with reduced dependency could be realized at low cost. As a result, it is possible to increase the degree of freedom of the color arrangement design of the electronic device equipped with the photodetecting device according to the present embodiment, and realize an electronic device casing design that is extremely difficult to visually recognize the presence of the photodetecting device. Became possible.

[Embodiment 3]
Since the brightness of the display is digitally controlled according to the ambient brightness, the illuminance sensor that detects the ambient brightness according to the human visual sensitivity characteristics has a measurement result within the desired illuminance level range. It is desirable to have a function of determining whether or not to notify the host system of the determination result (interrupt output).

  On the other hand, instead of making the determination directly at the illuminance level, an interrupt is generated depending on whether the difference (change in the count value) between the previous measurement and the latest measurement exceeds a predetermined threshold value, or the immediately preceding measurement count There are also many digital output type illuminance sensors on the market that add a predetermined count to a value and set a threshold value for the next measurement.

  In any case, in the digital output type illuminance sensor, the range of the illuminance output value and / or the register setting of the sensitivity are updated as necessary for the measurement result once obtained, and in the next measurement, It is necessary to set a threshold value (two upper limit threshold values and two lower limit threshold values) corresponding to the illuminance range to be used for determining the necessity of interrupt output each time.

  On the other hand, when the digital output value is obtained as the illuminance value directly or only by the bit shift operation, as in the respective light detection devices (illuminance sensors) described in [Embodiment 1] and [Embodiment 2]. Can reduce the processing burden on the host system side when the operation continues as described above. However, when the bit width of the light-digital conversion circuit 102 is a high resolution such as 16 bits, the threshold values for determining whether or not interrupt output is necessary (upper limit illuminance threshold value and lower limit illuminance threshold value, that is, the first threshold value) are set. In many cases, a register is set with a 16-bit width from the outside of the photodetection device.

  In addition, when the illuminance sensor and proximity sensor are integrated and operated simultaneously or sequentially, the operation as a proximity sensor, that is, the reflector has transitioned from non-proximity to proximity or from proximity to non-proximity at a desired distance. Since it is also necessary to set each of the determination thresholds (upper limit threshold and lower limit threshold, which will be referred to as the second threshold hereinafter) required for determining the light detection device (proximity illuminance sensor). ) Increases the register size to be provided inside.

  As described in [Background Art], the proximity sensor is a device that determines the proximity or non-proximity of a reflective object based on the intensity level of light that the light detection device itself emits from the reflective object again. Yes, it can be realized by diverting most of the configuration of the photodetector (illuminance sensor) described here.

  More specifically, constituent elements further required as the proximity sensor include at least a light emitting element that emits light and a driving unit thereof. In addition, timing control for determining a light emission time as a proximity sensor or an integration time for measuring the intensity of reflected light, a second threshold value holding and setting means, a determination circuit, and the like are required.

  However, the details of these additional configurations can be realized by modifying each means for the correction calculation described above with respect to the illuminance sensor, and are only a design matter for those skilled in the art. Omit.

  Now, from here, the digital output illuminance sensor or proximity illuminance sensor by each of the photodetection devices described so far can output the illuminance value directly (that is, it can be obtained only by bit shift calculation at most). A technique for greatly simplifying the complicated register setting update procedure, which has been necessary for the host system on which the photodetector is mounted, is disclosed below.

  First, as shown in an example in FIG. 9, from the illuminance threshold value table 1 (illuminance table) in which illuminances of three values (each value), {10 Lux, 100 Lux, 1000 Lux} are described, in a range from 1 to 30000 Lux. A set of a plurality of (in this case, 8) illuminance threshold tables that can be selected in 3 bits, up to an illuminance threshold table 8 in which illuminance of 2 values per digit and a total of 10 values is described, is read (ROM). As a dedicated memory), it is integrated inside the photodetector.

  In the case of a table having N illuminances as elements, N + 1 illuminance ranges are defined. For example, the illuminance threshold value table 1 having three elements defines four illuminance ranges of {less than 10 Lux, less than 10 Lux, less than 100 Lux, more than 100 Lux, less than 1000 Lux, more than 1000 Lux} using some or all of these elements. Can do.

  Each of the illuminance threshold tables 1 to 8 shown in FIG. 9 is used as a reference for generating an interrupt output when an illuminance sensor is actually operated by selecting (designating) one of the illuminance threshold tables by an external register setting.

  Specifically, assuming that the result of the previous measurement of illuminance exists in a certain illuminance range, and the next measurement result transitions to another illuminance range, the light detection device interrupts the host system. Generate output.

  Naturally, like the photodetection device 300 shown in FIG. 10, the photodetection device includes an output unit (first output unit) 1001 dedicated to interruption, apart from the communication unit 117 that is an interface used for communication with the outside. It is necessary to be.

  In addition, the light detection apparatus 300 also requires a determination unit as to which illuminance range the previous illuminance measurement result corresponds to, and a determination unit as to whether the illuminance range is different from the illuminance range that holds the new illuminance measurement result. .

  Note that it is easy for those skilled in the art that the set of illuminance threshold tables and each of the necessary determination means described above can be realized by modifying the arithmetic processing circuit 103 shown in FIG. To do.

  With such a configuration, the illuminance threshold value table that matches the illuminance level that requires interrupt output as the host system is selected and set from the tables shown in FIG.

  Once the operation as an illuminance sensor is started, after an interrupt is generated from the interrupt-dedicated output unit 1001, the host reads the illuminance data from the communication unit 117, adjusts the brightness of the display, and interrupts the interrupt-dedicated output unit 1001. The display brightness adjustment operation can be continued simply by clearing the output.

  This is particularly true when the configuration of the photodetection device according to each embodiment is integrated as a proximity illuminance sensor and the interrupt output means is shared by the proximity sensor and the illuminance sensor. It means that it is possible to reliably avoid various unstable behaviors or malfunctions of electronic devices that are dramatically simplified and are likely to occur due to detection errors of interrupt signals or delays in interrupt processing.

  By the way, as described above, in an electronic device, it is necessary to design as many functional blocks that are shared between the proximity sensor and the illuminance sensor as much as possible, so the proximity sensor and the illuminance sensor are time-divisionally divided. It is desirable to operate sequentially.

  Here, the integration time of the illuminance sensor is generally an integral multiple of 100 ms, which is the reciprocal of these difference frequencies, in order to cancel noise of 50 Hz or 60 Hz, which is a commercial power supply frequency. That is, the shortest integration time is 100 ms or longer unless power noise resistance is sacrificed. On the other hand, since it is necessary for the proximity sensor to follow at least the movement of the human body, a response speed of about 1 ms to a maximum of 200 ms is generally required.

  As described above, when the photodetection device 300 is used as an illuminance sensor, the interrupt processing is greatly reduced as described above. The operation cycle for performing the illuminance measurement and the proximity or non-proximity determination once is required at least 100 ms or more. Therefore, in the proximity illuminance sensor that operates alternately, it is particularly important to perform quick interrupt processing for each of the illuminance sensor and the proximity sensor.

  Here, in addition to the communication means 117 with the outside in FIG. 10, when the means for outputting an interrupt is only one of the output means 1001 dedicated to interruption, each sensor function of proximity and illuminance is logically ORed (either Interrupts when the status changes). On the host system side, it is necessary to read information indicating which sensor is performing an interrupt output, or read all output data of both sensors, and interpret specific interrupt contents. If a new interrupt occurs during this series of interrupt processing, the probability of occurrence of a detection error and a significant processing delay increases. As a result, it is difficult to stably satisfy the response time required for the proximity sensor within about 100 ms.

  In order to solve this problem, the photodetector 300 shown in FIG. 10 includes a second output unit 1002 in addition to the output unit 1001 dedicated to interruption.

  As a result, the output unit 1001 dedicated to interrupt can be used exclusively for the interrupt output of the illuminance sensor, and the second output unit 1002 can be selectively used for the output of the proximity sensor. Accordingly, the output of the second output means 1002 is either a proximity or non-proximity determination result or an interrupt output based on the determination result (that is, a state transition timing from proximity to non-proximity or from non-proximity to proximity). Can be output.

  As a result of the operation of the proximity sensor, the arithmetic processing circuit 103 sends the determination result from the subtraction result between the second threshold value for the proximity sensor and the reflected light level, or the interrupt output 1003 based on the determination result to the control unit 118 of the communication unit 117. The second output means 1002 is driven.

  From the viewpoint of shortening the operation cycle as the proximity illuminance sensor, in the case of the configuration described above, the second output means 1002 sends the determination result of proximity or non-proximity itself to the low level in the binary signal or It is more desirable to output corresponding to the high level and thereby drive the display ON / OFF directly.

  The reason for this is that when the photodetector according to each embodiment is operated sequentially as a proximity illuminance sensor, the target of interrupt processing required on the host system side is only the illuminance sensor greatly simplified by the illuminance threshold table described above. This is because the continuous operation cycle can be stabilized without adding an extra delay to the response time of the proximity sensor.

  Since the proximity sensor is intended to measure a moving object, the above effect is equivalent to stabilizing the detection distance of the proximity sensor. Therefore, the delay time due to complicated interrupt processing fluctuates under various operating conditions in which the object moves closer and away while the surrounding brightness changes, and the detection distance of the proximity sensor apparently fluctuates. Unstable and undesired behavior can be reliably avoided.

  As described above, according to the configuration of the photodetecting device 300 described with reference to FIGS. 9 to 10, the electronic device in which the photodetecting device 300 is mounted is maintained while maintaining various effects as the illuminance sensor described above. Significantly reduces the load of a series of interrupt processing required on the side, especially by stabilizing the operation cycle when performing continuous operation as a proximity illuminance sensor, thereby determining the response speed as a proximity sensor and resulting from interrupt processing It was possible to eliminate the unstable behavior.

  The floating-point conversion circuit 107 according to each embodiment performs compression to the second digital signal by converting the first digital signal into floating-point data, but is not limited thereto. That is, the first digital signal may be compressed into the second digital signal by being converted into data other than the floating point data.

  Furthermore, by mounting any of the above-described light detection devices on an electronic device such as a mobile phone, a smart phone, a digital camera, or a tablet-type or stationary computer, the electronic device is equipped with a light detection device. The same effect as the device is achieved.

  Note that, for example, with respect to the light detection device according to each mounting form, important characteristics to be corrected by the second digital signal (color or transmittance of the casing window) other than correction of the spectral characteristics of the light receiving element included in each light detection device ) Need not be actually measured by the user, and should be established even when measured values provided by a window manufacturer described in a catalog or data sheet are used.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be used for a digital output type photodetection device and an electronic apparatus equipped with the photodetection device. Examples of the electronic device include a mobile phone, a smartphone, a digital camera, and a tablet or stationary computer.

100, 200, and 300 Photodetection device 1001 Output means dedicated to interrupt (first output means)
1002 Second output means 101 Light receiving elements 101A and 101B Photodiode (light receiving element)
102, 102A, and 102B Optical-to-digital conversion circuit (first digital signal output means)
107 Floating point conversion circuit (second digital signal output means)
108 Floating point arithmetic circuit (arithmetic means)
109 Floating point-integer type data conversion circuit (third digital signal output means)
110 Current 111, 111A, and 111B First digital signal 112, 112A, and 112B Second digital signal 114 Third digital signal 115 Trimming correction circuit (first trimming correction circuit)
116 Trimming correction circuit (second trimming correction circuit)
117 communication means (communication means with outside)
118 Control unit (storage unit)
701 Register correction unit

Claims (20)

A light receiving element;
First digital signal output means for converting a signal obtained by receiving the light receiving element into a digital signal and outputting it as a first digital signal;
Second digital signal output means for compressing the first digital signal into floating point data having a bit width smaller than that of the first digital signal and outputting the compressed data as a second digital signal;
A calculation means for performing a calculation for correcting a relative error of the second digital signal with respect to an ideal value;
And a third digital signal output means for converting the result of the calculation into integer digital data and outputting the result as a third digital signal.   2. The photodetection device according to claim 1, wherein a bit width of the third digital signal is equal to or larger than a bit width of the second digital signal and equal to or smaller than a bit width of the first digital signal.   The value of the third digital signal is a value indicating the illuminance of light received by the light receiving element or a value indicating a value indicating the illuminance of light received by the light receiving element by a shift operation. The photodetecting device according to claim 1 or 2. The light receiving element is a plurality of photodiodes having different spectral characteristics,
4. The photodetecting device according to claim 1, wherein the number of the first digital signal output units is the same as the number of the plurality of photodiodes. 5.   5. The calculation unit according to claim 1, wherein the calculation unit performs a calculation for correcting a relative error of the second digital signal generated due to a variation in spectral characteristics of the light receiving element. The photodetection device according to any one of the above. A trim correction circuit that selects a desired correction coefficient from a plurality of correction coefficients according to variations in spectral characteristics of the light receiving element by fuse trimming;
The light detection device according to claim 5, wherein the calculation unit calculates a product of the second digital signal and the selected correction coefficient as the calculation.   The calculation means, as the calculation, performs a calculation for correcting a relative error of the second digital signal that occurs due to a variation in characteristics of the first digital signal output means. The photodetection device according to any one of 1 to 4. A trim correction circuit that selects a desired correction coefficient from a plurality of correction coefficients according to variations in characteristics of the first digital signal output means by fuse trimming;
The light detection apparatus according to claim 7, wherein the calculation unit calculates a product of the second digital signal and the selected correction coefficient as the calculation. A first trimming correction circuit that selects a desired first correction coefficient from a plurality of first correction coefficients determined by fuse trimming according to variations in spectral characteristics of the light receiving element;
A second trimming correction circuit that selects a desired second correction coefficient from a plurality of second correction coefficients determined by fuse trimming according to variations in characteristics of the first digital signal output means;
The calculation means includes the calculation as follows:
Performs an operation for correcting the relative error of the second digital signal that occurs due to variations in spectral characteristics of the light receiving element, and also occurs due to variations in characteristics of the first digital signal output means. , Performing an operation for correcting a relative error of the second digital signal,
Calculating a product of the second digital signal, the selected first correction coefficient, and the selected second correction coefficient;
5. The product according to claim 1, wherein a product of the first correction coefficient and the second correction coefficient is calculated in advance before calculating a product for the second digital signal. Photodetector. A communication means for communicating with the outside;
A storage unit for holding digital data received via the communication means,
The calculation means, as the calculation, corrects the relative error of the second digital signal caused by the dispersion of the spectral characteristics of the light receiving element, and the spectrum of the second digital signal and the light receiving element. Calculate the product with the correction coefficient determined according to the variation in characteristics,
The light according to claim 1, further comprising a register correction unit that selects a desired correction coefficient from a plurality of the correction coefficients based on digital data held in the storage unit. Detection device. A communication means for communicating with the outside;
A storage unit for holding digital data received via the communication means,
The calculating means corrects a relative error of the second digital signal that occurs due to variation in spectral characteristics of the photodiode as the calculation for each of the plurality of photodiodes. Calculate the product of the digital signal and the correction coefficient determined according to the dispersion of the spectral characteristics of the photodiode,
5. The register correction unit for selecting a desired correction coefficient from a plurality of the correction coefficients for each of the plurality of photodiodes based on digital data held in the storage unit. Light detection device. Determining whether or not the illuminance of the light received by the light receiving element is a desired value based on a result of comparing the third digital signal with a first threshold set in units of illuminance;
The photodetection device according to claim 3, wherein the determination result can be output to the outside.   The light detection apparatus according to claim 12, wherein the first threshold value is a value indicating a plurality of illuminances set from the outside. With multiple illumination tables,
Each of the plurality of illuminance tables has a value indicating a plurality of illuminances as an element,
13. The light detection device according to claim 12, wherein the first threshold value is a part or all of each value constituting an element of an illuminance table designated from the outside among the plurality of illuminance tables. . A light emitting device,
The light detection device according to claim 12, wherein the light receiving element receives light obtained by reflecting light emitted from the light emitting element by an external reflector.   The light detection according to claim 15, wherein a distance to the reflecting object can be detected based on a result of comparing the determination result with a second threshold value set from the outside. apparatus.   Output means for outputting the result of the determination to the outside when the result of the determination is changed, and outputting the result of the detection to the outside when the result of detecting the distance to the reflecting object is changed. The photodetection device according to claim 16, wherein First output means for outputting the result of the determination to the outside;
The photodetecting device according to claim 16, further comprising: a second output unit that outputs a result of detecting a distance to the reflecting object to the outside.   An electronic apparatus comprising the photodetection device according to claim 1. The photodetection device according to claim 11;
A housing of the light detection device,
The housing includes a window whose spectral transmittance changes when at least one of visible light and near infrared light is incident thereon,
The calculation means of the photodetecting device, as the calculation, corrects the relative error of the second digital signal, which is caused by variation in spectral transmittance of the window, and the second digital signal, Calculate the product of the correction coefficient determined according to the dispersion of the spectral transmittance of the window,
An electronic apparatus, wherein the register correction unit of the light detection device selects a desired correction coefficient from a plurality of the correction coefficients based on digital data stored in a storage unit of the light detection device.

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