JP6921591B2 - Sensor output processing device and sensor output processing method - Google Patents

Description

The present invention relates to a sensor output processing device and a sensor output processing method.

Conventionally, there is known an infrared measuring device that adjusts the drift of an infrared detector by changing the integration time of the infrared detector according to the temperature (for example, Patent Document 1). In a human sensor using infrared rays, there is known a technique for increasing the detection sensitivity by adjusting the amplification factor and the threshold value according to the temperature (for example, Patent Document 2).
[Patent Document]
[Patent Document 1] International Publication No. 2009/089897 [Patent Document 2] Japanese Unexamined Patent Publication No. 2009-244158

In a sensor output processing device that processes the output of a sensor that detects infrared rays, it is desirable to reduce the current consumption.

In the first aspect of the present invention, there is a sensor output processing device that processes the output of a sensor that detects infrared rays, in which an integrating unit that integrates a signal corresponding to the intensity of infrared rays detected by the sensor and a sensor location. Provided is a sensor output processing device including an integration time control unit that acquires information about the temperature and controls the integration time by the integration unit to be shorter as the temperature of the place is lower.

A second aspect of the present invention is a sensor output processing method for processing the output of a sensor that detects infrared rays, in which a step of integrating a signal corresponding to the intensity of infrared rays detected by the sensor and a temperature at the location of the sensor. Provided is a sensor output processing method comprising a step of acquiring information about the above and controlling the lower the temperature of the place to shorten the integration time per unit time in the integration stage.

The outline of the above invention does not list all the necessary features of the present invention. Sub-combinations of these feature groups can also be inventions.

The outline of the infrared detection apparatus 10 of one Embodiment of this invention is shown. An example of the configuration of the infrared detection device 10 is shown. An example of the configuration of the integrating unit 110 and the sample holding unit 120 is shown. An example of the output signal waveform of the integrating unit 110 is shown. An example of controlling the integration time based on temperature is shown. Another example of temperature-based integration time control is shown. The relationship between integration time, noise, and current consumption is shown. The relationship between temperature and sensor output signal is shown. The relationship between noise and the target signal is shown. An example of temperature-based threshold control is shown. An example of noise, output, S / N ratio, and current consumption in the processing apparatus 100 according to the embodiment of the present invention is shown. An example of the configuration of the infrared detection device 11 in the comparative example is shown. An example of noise, output, S / N ratio, and current consumption in the processing device 200 of the comparative example is shown. An example of the processing content by the infrared detection device 10 according to the embodiment of the present invention is shown.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the inventions that fall within the scope of the claims. Also, not all combinations of features described in the embodiments are essential to the means of solving the invention.

FIG. 1 shows an outline of the infrared detection device 10 according to the embodiment of the present invention. The infrared detection device 10 detects infrared rays. The infrared detection device 10 may be a motion sensor for detecting infrared rays emitted from the human body and determining whether or not the human body is present in the detection region.

The infrared detection device 10 includes an infrared sensor 20 and a processing device 100. The infrared sensor 20 is a sensor that detects infrared rays. The processing device 100 is a sensor output processing device that processes the output of the infrared sensor 20. The processing device 100 may be an integrated circuit formed on one semiconductor chip. The infrared sensor 20 and the processing device 100 may be incorporated in one package. The infrared detection device 10 of this example adopts the form of a surface mount type package, and has a plurality of external terminals 12a to 12f. However, the configuration of the infrared detection device 10 is not limited to this case. The infrared sensor 20 and the processing device 100 may be built in different packages.

FIG. 2 shows an example of the configuration of the infrared detection device 10. The infrared sensor 20 includes a sensor element 22. The sensor element 22 may be a photodiode or a phototransistor. In this example, the sensor element 22 is a photodiode. The sensor element 22 may be formed of a compound semiconductor such as InSb. The infrared sensor 20 generates a signal according to the intensity of infrared rays. Specifically, the sensor element 22 generates a photocurrent I according to the intensity of infrared rays. The equivalent circuit of the sensor element 22 may be represented as a circuit in which a constant current source and a resistor are connected in parallel. The infrared sensor 20 may be configured to carry an electric current due to the difference between the temperature of the background and the temperature of the object.

The processing device 100 of this example includes an integration unit 110, a sample hold unit 120, an ADC unit 130, a logical operation unit 140, a temperature measurement unit 150, an integration time control unit 160, and a threshold control unit 170. Further, the processing device 100 may include a comparison unit 180. However, the processing device 100 does not include the comparison unit 180, and as shown in FIG. 2, the comparison unit 180 may be provided outside the processing device 100. Further, the processing device 100 itself may include an infrared sensor 20.

The integrating unit 110 may have a current-voltage conversion circuit that converts the photocurrent I into a voltage. The integrating unit 110 integrates the photocurrent I, which is a signal output from the infrared sensor 20. The integration unit 110 may repeat the integration and the reset of the integrated value a plurality of times within the data update period. The sample hold unit 120 sample-holds the integration signal obtained by the integration unit 110. However, the sample hold unit 120 is not an essential component and may be omitted.

The ADC unit 130 is an analog-to-digital converter that converts an analog signal into a digital signal. The ADC unit 130 may convert the integrated signal sample-held by the sample-hold unit 120 into a digital signal. When the sample hold unit 120 is omitted, the ADC unit 130 converts the integrated signal obtained by the integrating unit 110 into analog-digital conversion.

The ADC unit 130 may be an incremental delta-sigma type AD converter. The delta-sigma AD converter samples an analog signal at a frequency higher than the original sampling frequency. The delta-sigma AD converter takes a difference between the sampled signal and the signal obtained by converting the output signal of the AD converter into a digital analog signal, integrates the differences, and compares them with a comparator. The output signal of the AD converter is processed by a digital filter.

However, the ADC unit 130 is not limited to the incremental ΔΣ type AD converter. The ADC unit 130 may be a SAR type (sequential comparison type) AD converter including a sequential comparison register (Successive Approximation Register). Alternatively, the ADC unit 130 may be a flash type AD converter. The logical operation unit 140 may be a signal processing logic circuit. For example, the logical operation unit 140 includes the above digital filter. The logical operation unit 140 may have a function of calculating the average of the integrated values by using the data obtained by digitizing the integrated values acquired a plurality of times.

The temperature measuring unit 150 measures the temperature at the location of the infrared sensor 20. The temperature measuring unit 150 is, for example, a resistance temperature detector, a thermistor, a thermocouple, or an IC temperature sensor. The temperature measuring unit 150 may measure a physical quantity as information related to temperature. Resistance temperature detectors and thermistors measure resistance values that change with temperature. Thermocouples measure thermoelectromotive forces that change with temperature. The temperature measuring unit 150 may be arranged adjacent to the sensor element 22.

In this example, the processing device 100 has a built-in temperature measuring unit 150. However, the temperature measuring unit 150 may be provided outside the processing device 100. In this case, the processing device 100 acquires information about the temperature at the location of the infrared sensor 20 from the external temperature measuring unit 150.

The integration time control unit 160 acquires information about the temperature at the location of the infrared sensor 20. The integration time control unit 160 controls the integration time in the integration unit 110 based on the acquired information about the temperature. The integration time may be the operating time during which the integration unit 110 is executing the integration process. The integration time control unit 160 may acquire information about the temperature from the temperature measurement unit 150. The integration time control unit 160 controls the integration unit 110 so that the lower the temperature at the location of the infrared sensor 20, the shorter the integration time per unit time by the integration unit 110. When the integrating unit 110 repeatedly integrates the signal and resets the integrated value a plurality of times per unit time, the integration time per unit time may mean the total time of the intervals of the plurality of integrations. The integration time control unit 160 may be realized by a control logic circuit, a microcomputer, or the like.

The comparison unit 180 compares the target signal with the threshold value. The target signal is a signal obtained from the output from the integrating unit 110. In this example, the target signal is a digital signal obtained by converting the integrated signal output from the integrating unit 110 through the sample hold unit 120 and the ADC unit 130. Further, when the integrating unit 110 repeatedly integrates the signal according to the intensity of infrared rays and resets the integrated value a plurality of times within a predetermined data update period, the target signal is a plurality of integrated signals. May be the average of the digitized signals. However, the target signal is not limited to these cases. The target signal may be a signal obtained from the integration signal that is the output of the integration unit 110. The comparison unit 180 may determine that the human body exists in the detection region when the target signal is equal to or greater than the threshold value.

The threshold control unit 170 acquires information about the temperature at the location of the infrared sensor 20 and controls the threshold value input to the comparison unit 180 based on the acquired information. The threshold value may be a human sensation threshold value for determining whether or not a human body exists in the detection region. The threshold control unit 170 may acquire information about the temperature from the temperature measurement unit 150. The threshold value control unit 170 may control the threshold value to be higher as the temperature at the location of the infrared sensor 20 is lower. The threshold voltage controlled according to the temperature is input to the input end of the comparison unit 180. The threshold control unit 170 may be realized by a control logic circuit, a microcomputer, or the like.

FIG. 3 shows an example of the configuration of the integrating unit 110 and the sample holding unit 120. The integrating unit 110 of this example includes an operational amplifier 112, a capacitor 113, a capacitor 114, and an input terminal 115. A capacitor 113 and a capacitor 114 may be electrically connected between the input end and the output end of the operational amplifier 112. Both ends of the sensor element 22 of the infrared sensor 20 may be electrically connected to the input end of the operational amplifier 112. Further resistors may be connected to both ends of the sensor element 22 and the input end of the operational amplifier 112. The operational amplifier 112 and the capacitors 113 and 114 of this example function as a transimpedance amplifier.

A switch for resetting the integral may be provided between the input end and the output end of the operational amplifier 112 in parallel with the capacitor 113 (or the capacitor 114). The switch for resetting the integration is closed when the command of the integration time control unit 160 is received, and the integration value is reset. Specifically, the reset switch discharges the electric charge accumulated in the capacitors 113 and 114.

The sample hold unit 120 of this example includes an operational amplifier 122, capacitors 123 and 124, a first switch 125, a grounding capacitor 126, and a second switch 127. A capacitor 123 and a capacitor 124 may be electrically connected between the input end and the output end of the operational amplifier 122. In this example, the first switch 125 and the second switch 127 are connected in series to the input end of the operational amplifier 122. The connection point between the first switch 125 and the second switch 127 may be grounded via the grounding capacitor 126.

During the sampling operation, the first switch 125 is closed and the capacitors 123 and 124 are charged. During the hold operation, the first switch 125 is in the open state. As a result, the charged voltage is maintained regardless of the fluctuation of the integrated signal of the integrating unit 110. The ADC unit 130 may convert the integrated signal sample-held by the sample-hold unit 120 into a digital signal. The configuration of the integrating unit 110 and the sample holding unit 120 described above is an example, and other configurations may be adopted.

FIG. 4 shows an example of the output voltage waveform of the integrating unit 110. The vertical axis represents voltage V and the horizontal axis represents time. The voltage corresponds to the integrated value. As shown in FIG. 4, the processing device 100 of this example executes a chopper operation. However, the processing device 100 is not limited to the one that executes the chopper operation. The integration unit 110 is controlled by a command from the integration time control unit 160, and repeats integration in the integration interval and resetting of the integration value a plurality of times.

In the integration interval, the integration signal 31 changes as a linear function of time. Then, the voltage is reset by the reset operation. The voltage value 32 at the apex of the integration signal 31 may be sample-held by the sample-hold unit 120. The sample hold unit 120 and the ADC unit 130 may operate at a time when the integration signal 31 which is the output of the integration unit 110 is near the apex.

The sensor output processing device 100 of this example configured as described above controls the integration time in the integration unit 110 based on the acquired information about the temperature. FIG. 5 shows an example of controlling the integration time based on temperature. When the integrating unit 110 is executing the integrating operation, the ADC unit 130 may be stopped (powered off). On the other hand, when the ADC unit 130 AD-converts the integration signal 31, the integration unit 110 is being reset.

In the example shown in FIG. 5, the data update period is 100 msec. The time for each integration operation and AD conversion operation may be set to a time of 1 msec or less. In this example, during the data update period, the integrating unit 110 repeats the integration and the resetting of the integrated value a predetermined number of times. The integration time control unit 160 controls so that the lower the temperature of the location of the infrared sensor 20, the smaller the number of times of repeating the integration and the reset of the integrated value per data update period. Since the integration interval for each time is the same, as the number of repetitions decreases, the integration time, which is the sum of the intervals for a plurality of integrations per unit time (for example, the data update period), becomes shorter.

In the example shown in FIG. 5, when the temperature at the location of the infrared sensor 20 is as high as 30 ° C. or higher, the number of repetitions of integration and resetting of the integrated value is N times. The integration time control unit 160 reduces the number of repetitions as the temperature at the location of the infrared sensor 20 decreases. As a result, as the temperature at the location of the infrared sensor 20 decreases, the time during which the integrating unit 110 pauses can be lengthened. Therefore, the integration time control unit 160 can reduce the current consumption in the integration unit 110.

In FIG. 5, the rest time is collectively displayed in the final period of the data update period. However, the control by the integration time control unit 160 is not limited to this case, and a pause time may be provided each time the integration and the reset of the integrated value are repeated.

FIG. 6 shows another example of controlling the integration time based on temperature. In this example, the lower the temperature at the location of the infrared sensor 20, the shorter the time of the integration interval per integration. The number of times the integration and the reset of the integration value are repeated per data update period does not change. However, since the time of the integration interval is shortened, the voltage value 32 at the apex of the integration signal 31 becomes smaller. Therefore, it is necessary to reduce the threshold value used in the comparison unit 180 in conjunction with the shortening of the integration interval time. The relationship between the time of the integration interval and the threshold value may be stored in advance in the storage unit as a lookup table or a conversion formula. The threshold value control unit 170 may determine the threshold value by referring to a look-up table or the like so that the threshold value becomes smaller in conjunction with the shortening of the integration interval time. Alternatively, instead of determining the threshold value so that the threshold value becomes smaller in conjunction with the shortening of the integration interval time, the logical operation unit 140 in the logical operation unit 140 interlocks with the shortening of the integration interval time so that the final output gain becomes constant. The signal may be amplified.

The control shown in FIG. 6 can also shorten the integration time, which is the sum of the intervals of a plurality of integrations per unit time (for example, a data update period) as the temperature decreases. When the integration time is shortened, the time during which the integration unit 110 pauses can be lengthened. Therefore, the current consumption in the integrating unit 110 can be reduced.

FIG. 7 shows the relationship between integration time, noise, and current consumption. The horizontal axis of FIG. 7 indicates the integration time, which is the sum of the intervals of a plurality of integrations per unit time. The noise in this example is frequency-independent noise. The noise may be thermal noise (thermal noise) or the like. Noise is inversely proportional to the positive square root of the integration time. The current consumption is proportional to the integration time. As the integration time increases, the noise decreases while the current consumption increases. As the integration time becomes shorter, the noise increases while the current consumption decreases. Therefore, there is a trade-off between current consumption and noise.

When the output signal of the infrared sensor 20 is buried in noise, the infrared detection device 10 cannot detect the human body in the detection region. That is, when the signal-to-noise ratio (S / N ratio: signal (S) / noise (N)) becomes small, the infrared detection device 10 cannot detect the human body in the detection region. Therefore, the processing device 100 needs to suppress the noise to a level that can be distinguished from the output of the infrared sensor 20. Specifically, the processing device 100 of this example lengthens the integration time to reduce noise. When the output signal of the infrared sensor 20 becomes large, the condition of a desired signal-to-noise ratio is satisfied without necessarily increasing the integration time.

As the output signal of the infrared sensor 20 becomes larger, the permissible noise specifications (noise specifications) can be increased. If the allowable noise specification is Nspec and the noise when the predetermined integration interval (integration time) is executed once is N1, the frequency dependence of the flicker noise due to the case where the flicker noise can be ignored or the chopper operation or the like. If can be ignored, the minimum number of integrations required to satisfy the noise specification Nspec is given by the following equation. In this example, it is assumed that N1 is constant regardless of temperature.

FIG. 8 shows the relationship between the temperature and the sensor output signal. The horizontal axis indicates the temperature at the location of the infrared sensor 20. The vertical axis shows the output signal of the infrared sensor 20. FIG. 8 shows a case where infrared rays from the human body are detected. In the infrared sensor 20, the larger the temperature difference between the temperature of the infrared sensor 20 itself and the temperature of the object to be detected, the larger the output signal. When the object is a homeothermic animal such as the human body, the temperature of the object is less dependent on the temperature of the place than other objects.

On the other hand, the temperature of the infrared sensor 20 is the same as the temperature of the place of the infrared sensor 20. Therefore, the output signal (S) from the infrared sensor 20 becomes smaller as the air temperature rises and approaches the temperature of the human body. The assumed operating temperature (recommended temperature) of the infrared sensor 20 when used as a motion sensor may be 0 ° C. or higher and 35 ° C. or lower.

As the temperature at the location of the infrared sensor 20 decreases, the output signal (S) of the infrared sensor 20 increases, so that the permissible noise specification Nspec can be increased. The temperature and the noise specification Nspec may have a proportional relationship. In the above equation 1, as the noise specification Nspec increases, the minimum number of integrations required to satisfy the noise specification Nspec, that is, the number of repetitions of the integration and the reset of the integrated value per data update period should be reduced. Can be done. Therefore, the integration time control unit 160 shortens the integration time, which is the sum of the intervals of a plurality of integrations per unit time (for example, the data update period) by the integration unit 110, as the temperature at the location of the infrared sensor 20 becomes lower. Control. As described with reference to FIG. 7, as the integration time becomes shorter, the current consumption of the integration unit 110 can be reduced.

According to this example, it is allowed that the noise increases as the temperature at the location of the infrared sensor 20 decreases. The current consumption can be reduced by allowing the noise to increase. When the temperature of the place of the infrared sensor 20 becomes low, even if the noise becomes large, the output signal (S) of the infrared sensor 20 also becomes large. Therefore, the S / N ratio should be maintained within a predetermined range. Can be done.

FIG. 9 shows the relationship between noise and the target signal. The target signal is a signal obtained from the output from the integrating unit 110. FIG. 9 shows a target signal when changing from a non-detection state in which the human body does not exist in the detection region to a detection state in which the human body exists. As described above, as the temperature at the location of the infrared sensor 20 decreases, the output signal (S) of the infrared sensor 20 increases due to the characteristics of the infrared sensor 20 of this example, and the target signal also increases. Further, in this example, the integration time control unit 160 controls so that the integration time becomes shorter as the temperature at the location of the infrared sensor 20 becomes lower. Therefore, the processing device 100 of this example allows the noise to increase as the temperature decreases.

The processing device 100 of this example prevents the occurrence of false positives due to allowing the noise to increase as the temperature decreases. False positives can occur when the target signal exceeds a threshold even though there is no human body in the detection area. In this respect, the threshold value control unit 170 of this example controls so that the lower the temperature at the location of the infrared sensor 20, the higher the threshold value, in order to prevent erroneous detection.

FIG. 10 shows an example of temperature-based threshold control. If a constant threshold is used regardless of the temperature at the location of the infrared sensor 20, the target signal may exceed the threshold when the temperature drops, even though there is no human body in the detection area. .. On the other hand, in the processing device 100 of this example, the threshold value control unit 170 controls so that the lower the temperature at the location of the infrared sensor 20, the higher the threshold value. As a result, it is possible to reduce the influence caused by the increase in noise as the temperature decreases. Further, as the temperature decreases, the target signal also increases, so that the human body can be sufficiently detected even if the threshold value is increased.

FIG. 11 shows an example of noise (N), output (S), S / N ratio, and current consumption in the processing apparatus 100 according to the embodiment of the present invention. In this example, as shown in the upper left column of FIG. 11, the output signal (S) of the infrared sensor 20 increases as the temperature at the location of the infrared sensor 20 decreases. As shown in the upper right column of FIG. 11, as the temperature at the location of the infrared sensor 20 decreases, the output signal (S) of the infrared sensor 20 increases, so that the integration time control unit 160 increases noise. Tolerate. In the processing apparatus 100 according to the embodiment of the present invention, it is not always necessary to change the final output gain.

The integration time control unit 160 controls so that the lower the temperature at the location of the infrared sensor 20, the shorter the integration time. The shorter the integration time, the larger the noise. The integration time control unit 160 may suppress noise so that the S / N ratio falls within a predetermined range. For example, the integration time control unit 160 controls the integration time so that the S / N ratio becomes constant. Since the integration time control unit 160 controls so that the integration time becomes shorter as the temperature at the location of the infrared sensor 20 becomes lower, the current consumption in the integration unit 110 decreases.

FIG. 12 shows an example of the configuration of the infrared detection device 11 in the comparative example. The infrared detection device 11 includes an infrared sensor 20 and a processing device 200. The processing device 200 is a sensor output processing device that processes the output of the infrared sensor 20. The processing device 200 may include an integration unit 210, a sample hold unit 220, an ADC unit 230, a logical operation unit 240, an integration time control unit 260, and a threshold control unit 270. In the processing device 200, the integration time of the integration unit 210 does not change depending on the temperature at the location of the infrared sensor 20. Further, the threshold value does not change according to the temperature of the location of the infrared sensor 20. Except for the above points, the processing device 200 of the comparative example is the same as the processing device 100 of the above embodiment. Therefore, the repetitive description will be omitted.

FIG. 13 shows an example of noise (N), output (S), S / N ratio, and current consumption in the processing device 200 of the comparative example. As shown in the upper left column of FIG. 13, the output signal (S) of the infrared sensor 20 increases as the temperature at the location of the infrared sensor 20 decreases. However, in the comparative example, the integration time control unit 260 does not change the integration time according to the temperature at the location of the infrared sensor 20. Since the integration time does not change, the noise does not increase even when the temperature decreases. That is, the integration time control unit 260 does not allow the noise to increase as the temperature at the location of the infrared sensor 20 decreases.

In the processing device 200 of the comparative example, in the above equation 1, the permissible noise spec (noise specification) Nspec is determined from the output signal (S) of the infrared sensor 20 at a specific temperature. For example, the noise specification Nspec is uniformly determined by the output signal of the infrared sensor 20 when the human body is detected at 30 ° C. The processing device 200 of the comparative example does not change the noise specification Nspec according to the temperature. The processing device 200 keeps the noise constant without shortening the integration time even if the temperature becomes low and the signal (S) which is the output of the infrared sensor 20 becomes large. Therefore, as the temperature decreases, the S / N ratio increases. However, even if the temperature is lowered, the current consumption is not reduced because the integration time is not shortened.

Unlike the processing device 200 of the comparative example, the processing device 100 of the embodiment of the present invention varies the integration time for integrating the signal corresponding to the intensity of infrared rays detected by the infrared sensor 20 according to the temperature. Therefore, as compared with the processing device 200 of the comparative example, the infrared sensor is compared with a configuration in which the integration time is determined based on the signal output of the infrared sensor 20 at a temperature of 30 ° C. and the integration time is not changed according to the temperature. As the temperature of the 20 places becomes lower, the effect of reducing the current consumption can be obtained. In particular, the current consumption is reduced in the temperature region where the infrared detection device 10 is frequently used.

According to the processing apparatus 100 of one embodiment of the present invention, the S / N ratio is maintained within a predetermined range. Further, even when applied to a motion sensor, the threshold control unit 170 controls so that the lower the temperature at the location of the infrared sensor 20, the higher the threshold value, so that the frequency of false detections can be reduced.

FIG. 14 shows an example of processing contents by the infrared detection device 10 according to the embodiment of the present invention. FIG. 14 describes a sensor output processing method for processing the output of a sensor that detects infrared rays. The infrared sensor 20 detects infrared rays. A photocurrent I is generated according to the intensity of infrared rays (step S101). The infrared sensor 20 may be configured to carry an electric current due to the difference between the temperature of the background and the temperature of the object.

The integration time control unit 160 acquires an initial value of the number of repetitions in the integration unit 110 (step S102). The number of repetitions is the number of repetitions of integration and reset of the integrated value during the data update period. The initial value of the number of repetitions may be stored in advance in a storage unit such as a memory. Further, the integration time control unit 160 may determine the initial value of the number of repetitions based on the information about the temperature at the location of the infrared sensor 20.

The threshold control unit 170 acquires the initial value of the threshold value input to the comparison unit 180 (step S103). The initial value of the threshold value may be stored in advance in a storage unit such as a memory. Further, the threshold value control unit 170 may determine the initial value of the threshold value based on the temperature information of the location of the infrared sensor 20. The order of steps S102 and S103 is not limited to this case. The processes of step S102 and step S103 may be executed in parallel.

The integrating unit 110 integrates the photocurrent I, which is a signal output from the infrared sensor 20 (step S104). Step S104 corresponds to an integration step of integrating a signal according to the intensity of infrared rays detected by the infrared sensor 20. The integrator 110 converts the input photocurrent I into a voltage and outputs the integrator signal 31. The sample hold unit 120 samples the voltage value 32 at the apex of the integration signal 31 (step S105). The ADC unit 130 may convert the integrated signal 31 sample-held by the sample-hold unit 120 into a digital signal (step S106). However, the process of step S105 may be omitted.

The integration unit 110 repeats the integration and the reset of the integrated value during the data update period over the number of repetitions determined by the integration time control unit 160. Specifically, if the number of times the integration and the reset of the integrated value are executed has not reached the number of repetitions (step S107: NO), the process returns to step S104. When the integrating unit 110 executes the integration and the reset of the integrated value over the number of repetitions (step S107: YES), the logical operation unit 140 may calculate the average of the integrated values executed over the number of repetitions (step S108). The processing device 100 of this example uses the calculated average as the target signal. However, the target signal is not limited to the calculated average. The target signal may be a signal obtained from the integration signal 31 which is the output of the integration unit 110.

The comparison unit 180 compares the target signal with the threshold value. When the target signal is equal to or greater than the threshold value (step S109: YES), the comparison unit 180 may determine that the human body exists in the detection region (step S110). If the target signal is less than the threshold value (step S109: NO), it is not determined that the human body exists in the detection region.

The temperature measuring unit 150 measures the temperature at the location of the infrared sensor 20 (step S111). The integration time control unit 160 determines a new number of times the integration and the reset of the integration value are repeated by the integration unit 110 within the next data update period based on the information about the temperature measured by the temperature measurement unit 150. (Step S112). The integration time control unit 160 may reduce the number of repetitions as the temperature at the location of the infrared sensor 20 is lower. As the number of repetitions decreases, the integration time, which is the sum of a plurality of integration intervals per unit time (for example, a data update period), becomes shorter. The process of step S112 corresponds to a step of acquiring information about the temperature at the location of the infrared sensor 20 and controlling so that the lower the temperature, the shorter the integration time per unit time in the integration step (step S104).

The threshold control unit 170 determines a new threshold value to be used by the comparison unit within the next data update period based on the information about the temperature measured by the temperature measurement unit 150 (step S113). The process of step S113 corresponds to a step of acquiring information about the temperature at the location of the infrared sensor 20 and controlling the threshold value to be higher as the temperature is lower. The temperature measurement step (step S111), the number of repetitions determination step (step S112), and the threshold value determination step (step S113) are prior to the step of repeating the integration and the reset of the integrated value (steps S104 to S106). It may be executed or may be executed in parallel.

The process returns to step S104, and the next data update period begins. The processing apparatus 100 executes the processing of step S104 or less by using the number of repetitions and the threshold value determined by the integration time control unit 160 and the threshold value control unit 170 based on the information about the temperature measured by the temperature measurement unit 150. .. In step S104, the integration time by the integration unit 110 becomes shorter as the temperature at the location of the infrared sensor 20 becomes lower. The threshold value that the comparison unit 180 compares with the target signal in step S109 becomes higher as the temperature at the location of the infrared sensor 20 is lower.

Therefore, according to this example, the lower the temperature at the location of the infrared sensor 20, the shorter the integration time in the integration stage. Therefore, the current consumption can be reduced. When the temperature of the place of the infrared sensor 20 becomes low, even if the noise becomes large, the output signal (S) of the infrared sensor 20 also becomes large. Therefore, the S / N ratio should be maintained within a predetermined range. Can be done.

In the above description, the case where the threshold value control unit 170 controls the threshold value input to the comparison unit 180 has been described, but the processing device 100 is not limited to this case. Depending on the relationship between the noise and the threshold value, it may not be necessary for the threshold value control unit 170 to control the threshold value. In this case, the threshold control unit 170 is omitted.

The processing device 100 has an integrating unit 110 that integrates a signal according to the intensity of infrared rays detected by the infrared sensor 20, and the integration unit 110 shortens the integration time per unit time as the temperature at the location of the infrared sensor 20 is lower. As long as the integration time control unit 160 for controlling the infrared rays is provided, the configuration is not limited to the above-mentioned configuration, and various circuit configurations can be added or omitted. Further, as long as the integrating unit 110 integrates the signal from the infrared sensor 20, the circuit configuration is not limited.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that such modified or improved forms may also be included in the technical scope of the present invention.

The order of execution of each process such as operation, procedure, step, and step in the device, system, program, and method shown in the claims, specification, and drawings is particularly "before" and "prior to". It should be noted that it can be realized in any order unless the output of the previous process is used in the subsequent process. Even if the scope of claims, the specification, and the operation flow in the drawings are explained using "first", "next", etc. for convenience, it means that it is essential to carry out in this order. It's not a thing.

10 ... Infrared detector, 11 ... Infrared detector, 12 ... External terminal, 20 ... Infrared sensor, 22 ... Sensor element, 31 ... Integrated signal, 32 ... Voltage value, 100 ... Processing device, 110 ... Integrator, 112 ... Op amp, 113 ... Capacitor, 114 ... Capacitor, 115 ... Input terminal, 120 ... Sample hold, 122 ... Op amp, 123 ... Capacitor, 124 ... Capacitor, 125・ ・ 1st switch, 126 ・ ・ Capacitor for grounding 127 ・ ・ 2nd switch, 130 ・ ・ ADC unit, 140 ・ ・ Logic calculation unit, 150 ・ ・ Temperature measurement unit, 160 ・ ・ Integration time control unit, 170 ・ ・・ Threshold control unit, 180 ・ ・ Comparison unit, 200 ・ ・ Processing device, 210 ・ ・ Integration unit, 220 ・ ・ Sample hold unit, 230 ・ ・ ADC unit, 240 ・ ・ Logic calculation unit, 260 ・ ・ Integration time control unit 270 ... Threshold control unit

Claims (7)

A sensor output processing device that processes the output of a sensor that detects infrared rays.
An integrating unit that integrates a signal according to the intensity of the infrared rays detected by the sensor, and an integrating unit.
An integration time control unit that acquires information about the temperature at the location of the sensor and controls so that the lower the temperature at the location, the shorter the integration time per unit time by the integration unit.
A sensor output processing device comprising. A comparison unit that compares the target signal obtained from the output signal from the integration unit with the threshold value, and
The sensor output processing device according to claim 1, further comprising a threshold control unit that controls the threshold value to be raised as the temperature at the location is lower. A temperature measuring unit for measuring the temperature of the place is further provided.
The sensor output processing device according to claim 2. The sensor output processing device according to claim 2 or 3, wherein the comparison unit determines that a human body exists in the detection region when the target signal is equal to or higher than the threshold value. Within a predetermined data update period
The integrating unit repeatedly integrates the signal according to the intensity of the infrared rays and resets the value of the integration, and the target signal is obtained from the integration of the signal over the plurality of times.
The comparison unit compares the target signal with the threshold value and compares the target signal with the threshold value.
The temperature measuring unit measures the temperature at the place and
The integration time control unit resets the integration and the value of the integration by the integration unit within the next data update period based on the information about the temperature at the location measured by the temperature measurement unit. Determine a new number of times to repeat,
The third aspect of claim 3, wherein the threshold control unit determines a new threshold value to be used by the comparison unit within the next data update period based on the information about the temperature of the place measured by the temperature measurement unit. Sensor output processing device. The sensor output processing device according to any one of claims 1 to 5, further comprising the sensor for detecting infrared rays. It is a sensor output processing method that processes the output of a sensor that detects infrared rays.
The step of integrating the signal according to the intensity of the infrared ray detected by the sensor, and
A step of acquiring information about the temperature at the location of the sensor and controlling so that the lower the temperature at the location, the shorter the integration time per unit time in the integration step.
A sensor output processing method comprising.

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