JP2009236650A - Light emitting device and spatial information detector using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve high stability in a wide control range in performing the feedback control of emission timing in a light emitting device which is used for a distance image sensor or the like and emits a modulated optical signal. <P>SOLUTION: The light emitting device 10 in the distance image sensor 30 emits modulated infrared rays from a light emitting element 14, receives the reflected light from an object under measurement 21 by a light receiving element 22 in a plurality of divided periods, determines the time difference between the light emission signal and the light reception signal from the amount of light received in each period by an evaluation arithmetic circuit 23, and measures the three-dimensional shape of the object under measurement 21 including its depth. The phases of a feedback signal from the light emitting element 14 and a light emission control signal from a timing signal generating circuit 11 are compared to each other by a phase comparison circuit 15. In performing the feedback control of a delay time adjustment circuit 12, the light emission control signal is input to the phase comparison circuit 15 through a fixed delay circuit 16, and the fixed delay amount (a DC component) of the loop is removed, thereby allowing only an AC component which changes with temperature to be subjected to phase comparison. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light emitting device suitably used for a spatial information detecting device realized as a distance image sensor and the like, and the distance image sensor using the light emitting device.

  The distance image sensor emits modulated infrared light from a light emitting element such as an LED array, and the reflected light from the measurement object is received by the light receiving element such as a CCD array sensor divided into a plurality of periods. Is a device for obtaining a time difference (Time of Flight) between a light emission signal and a light reception signal from the received light amount and measuring a three-dimensional shape including the depth of the measurement object. Is shown in

  In the distance image sensor, if the delay time from when the light emission signal is generated until the light emitting element actually emits light is not constant, accurate distance measurement cannot be performed. Therefore, conventionally, the light emitting device is configured as shown in FIG. First, the light emission control signal created by the timing signal generation circuit 1 is input to the delay time adjustment circuit 2, the delay time is adjusted as will be described later, and further the power is amplified by the drive circuit 3 to obtain the actual drive signal. The light emitting element 4 is turned on and driven.

A feedback signal is generated by the light emission of the light emitting element 4, and the phase of the feedback signal is compared with the light emission control signal from the timing signal generation circuit 1 in the phase comparison circuit 5, and the delay is generated with an error signal corresponding to the comparison result. The delay time of the time adjustment circuit 2 is adjusted, and the phase delay between the light emitting device and the light receiving device is controlled to coincide. That is, from the output of the light emission control signal, the light emission timing of the light emitting element 4 in response thereto is controlled to have a certain delay time. Note that the feedback signal from the light emitting element 4 may be extracted by using the drive signal from the drive circuit 3, and the signal actually emitted by the light emitting element 4 is shown in FIG. It may be performed by converting into an electric signal by a photoelectric conversion element that does not.
JP 2004-45304 A

  By performing the feedback control as described above, the characteristics of the circuit elements (element variations, characteristic fluctuations due to environmental changes (temperature, humidity, etc.), parasitic elements) in the feedback loop change, and the delay amount Even if changes, the delay amount can be kept constant. However, such feedback control is possible as long as the control range is not exceeded. Therefore, in the actual design, the range of the delay control amount (feedback amount) that can be controlled by the loop is set in consideration of the element variation in the loop. However, in general, in the DLL (PLL), the control range and the stability are in a trade-off relationship. If the control range is widened, the stability is lowered, and when trying to obtain high stability, the control range is narrowed. Considering delay control and distance measurement performance in the distance image sensor, if the stability decreases, clock jitter increases and distance measurement characteristics deteriorate.

  Here, in the case of the light emitting device, the delay element is a wiring delay in addition to the element delay of the drive circuit 3 and the light emitting element 4. Among them, the wiring delay is the shortest way to minimize the control amount in the feedback loop control, that is, to improve the stability, by making it as small as possible. However, if the wiring from the drive circuit 3 to the light emitting element 4 is shortened, there is a problem that the degree of freedom in design is narrowed because the layout of parts is restricted. In addition, since the light emitting element 4 used for the distance image sensor has a strong light emission power and a large amount of heat generation, if the wiring is shortened and approaches a block of the control circuit or other circuits 1 to 3, A new problem of changing the temperature characteristic also occurs.

  An object of the present invention is to provide a light emitting device capable of obtaining high stability even when a wiring delay to the light emitting element is increased, and a spatial information detecting device using the light emitting device.

  A light-emitting device of the present invention includes a light-emitting element that emits light in response to a drive signal, a timing signal generation circuit that generates a light-emission control signal that indicates the emission timing of the light-emitting element, and a response to the light-emission control signal. A drive circuit that generates the drive signal; a phase comparison circuit that compares phases of a feedback signal from the light emitting element and the light emission control signal and outputs an error signal corresponding to the comparison result; and the timing signal generation circuit And a delay time adjusting circuit that adjusts the timing of the light emission control signal in response to the error signal, and is interposed between the timing signal generating circuit and the phase comparison circuit. And a fixed delay circuit that delays the control signal by a predetermined fixed time and inputs the delayed control signal to the phase comparison circuit.

  According to the above configuration, a light emitting element such as an LED array that is used in a distance image sensor and emits light whose emission timing is defined in response to a drive signal, and light emission control that indicates the emission timing of the light emitting element A timing signal generation circuit for generating a signal, a drive circuit for generating the drive signal by, for example, amplifying the light emission control signal, and comparing the phase of the feedback signal from the light emitting element and the light emission control signal, A phase comparison circuit that outputs an error signal corresponding to the comparison result, and a delay time adjustment that is interposed between the timing signal generation circuit and the drive circuit and adjusts the timing of the light emission control signal in response to the error signal And a feedback control for keeping the emission timing of the light emitting element with respect to the light emission control signal within a predetermined control range. In the light emitting device that performs, between the timing signal generating circuit and a phase comparator circuit, the light emission control signal by delaying previously determined fixed time providing a fixed delay circuit for input to the phase comparator.

  Therefore, in the phase comparison between the light emission control signal and the feedback signal in the phase comparison circuit, an invariable delay time typified by wiring delay is added to the light emission control signal as a DC component (with a clogged footwear). Therefore, it is equivalent to subtracting from the feedback signal, and the actual control range amount by feedback is only about AC that varies depending on temperature, humidity, and the like. Thereby, even if the light emitting element is arranged at a remote place from other circuits, the wiring delay due to this increases, and even if the range of the delay control amount (feedback amount) to be loop-controlled increases, the delay control amount (feedback) The actual variation (AC component) in (quantity) can be reduced, and high stability can be obtained.

  In the light emitting device of the present invention, the fixed delay circuit includes a CR integration circuit.

According to the above configuration, the temperature characteristic of a general carbon-based resistor is +350 to −150 ppm, whereas the temperature characteristic of a metal foil resistor made using a nickel-chrome metal is 0. .5ppm or less, and such a low temperature characteristic resistance element is combined with a low temperature characteristic capacitance element such as a ceramic capacitor using titanium oxide (TiO ₂ ) as a main material and added with metal oxide. By creating the delay circuit, the fixed delay circuit can be configured with only passive elements without using active elements, and integration is easy.

  Furthermore, in the light emitting device of the present invention, the timing signal generation circuit includes an oscillation circuit and a frequency dividing circuit that divides the oscillation signal to generate the light emission control signal, and the fixed delay circuit includes: And an active element that takes in the oscillation signal and delays it by a predetermined fixed time and inputs it as the light emission control signal to the phase comparison circuit.

  According to the above configuration, the CR integration circuit of the passive element has a temperature characteristic and does not strictly have a fixed delay. Therefore, when the timing signal generation circuit is configured to include an oscillation circuit and a frequency dividing circuit that divides the oscillation signal to generate the light emission control signal, the fixed delay circuit is connected to a flip-flop or a latch. It is constituted by an active element such as a circuit and a register constituted by these. Then, these active elements take in the oscillation signal, synchronize with the oscillation signal (with the oscillation signal as a clock signal), delay the signal for a predetermined fixed time, and input it as the light emission control signal to the phase comparison circuit To do.

  Therefore, by adjusting the number of stages of the active elements using a high-speed oscillation signal (reference clock signal) from the oscillation circuit, a delay close to the predetermined fixed delay time can be performed. In addition, variations in delay time due to the temperature characteristics can be suppressed.

  Further, in the light emitting device of the present invention, the active element is formed by cascading a plurality of stages, and a selection circuit that takes out the output from any one of the extraction units provided in an arbitrary stage and gives it to the phase comparison circuit Is further provided.

  According to the above configuration, by switching the extraction unit by the selection circuit, delay times different in stages can be obtained from the outputs of the active elements in a plurality of stages.

  Therefore, it is possible to cope with variations in the fixed time due to the apparatus.

  Furthermore, the light emitting device of the present invention further includes a waveform shaping circuit that shapes the drive signal from the drive circuit and applies the waveform to the light emitting element.

  According to said structure, when the wiring to the said light emitting element becomes long and when a connector etc. are interposed in between, a propagation characteristic will deteriorate by reflection etc. and a distortion will arise in a waveform. As a result, in the phase comparison circuit, it is difficult to normally perform phase comparison at the rise and fall of the waveform, and delay control may become impossible. Therefore, a waveform shaping circuit (clock buffer) that performs waveform shaping is provided on the drive signal line from the drive circuit in the feedback loop, preferably also on the feedback signal line, and the long wiring section and connector section are waveform shaped. The signal is transmitted while performing.

  Therefore, it is possible to reduce the AC component of the delay due to the long wiring section and connector section to the light emitting element. Although the delay offset (DC component) due to the waveform shaping circuit increases, there is a concern that the AC component may increase due to temperature characteristics or the like, but these can be removed by the delay time adjusting circuit by feedback.

  In addition, a spatial information detection device according to the present invention is characterized by using the light emitting device.

  According to the above configuration, even when the light emitting element is disposed at a remote place from another circuit, the wiring delay due to this increases, and the delay control amount (feedback amount) to be loop-controlled increases, the delay is increased. It is possible to realize a spatial information detection device that can reduce the actual variation (AC component) in the control amount (feedback amount) and obtain high stability.

  As described above, the light-emitting device of the present invention is used in a distance image sensor or the like, and emits light whose emission timing is defined in response to a drive signal, and the emission timing of the light-emitting element. A timing signal generation circuit for generating a light emission control signal for instructing, a drive circuit for generating the drive signal by power amplification of the light emission control signal, a feedback signal from the light emitting element, and the light emission control signal A phase comparison circuit that compares phases and outputs an error signal corresponding to the comparison result, and is interposed between the timing signal generation circuit and the drive circuit, and in response to the error signal, adjusts the timing of the light emission control signal. A delay time adjusting circuit for adjusting, and a timing for accommodating the emission timing of the light emitting element with respect to the light emission control signal within a predetermined control range. In the light emitting device that performs readback control, between the timing signal generating circuit and a phase comparator circuit, the light emission control signal by delaying previously determined fixed time providing a fixed delay circuit for input to the phase comparator.

  Therefore, in the phase comparison between the light emission control signal and the feedback signal in the phase comparison circuit, an invariable delay time typified by wiring delay is added to the light emission control signal as a DC component, and therefore the feedback signal This is equivalent to subtracting from the control range, and the actual control range amount by feedback is only about AC that varies with temperature, humidity, and the like. Thereby, even when the light emitting element is arranged at a remote place from other circuits, high stability can be obtained.

In the light emitting device of the present invention, as described above, the fixed delay circuit is composed of a metal foil resistor made of nickel chrome metal and titanium oxide (TiO ₂ ) as main raw materials. It is composed of a CR integration circuit with a ceramic capacitor to which is added.

  Therefore, the fixed delay circuit can be configured with only passive elements without using active elements, and integration is easy.

  Furthermore, as described above, the light emitting device of the present invention is configured such that the timing signal generation circuit includes an oscillation circuit and a frequency dividing circuit that divides the oscillation signal to generate the light emission control signal. In this case, the fixed delay circuit is constituted by an active element such as a flip-flop or a latch circuit and a register constituted by these.

  Therefore, a delay of a time close to the predetermined fixed delay time can be performed by adjusting the number of stages of the active elements using a high-speed oscillation signal (reference clock signal) from the oscillation circuit. In addition, variations in delay time due to the temperature characteristics can be suppressed.

  Further, as described above, the light emitting device of the present invention is configured by cascading the active elements in a plurality of stages, and the output from any one of the extraction units provided in any stage is extracted by the selection circuit. To the phase comparison circuit.

  Therefore, it is possible to cope with variations in the fixed time due to the apparatus.

  Furthermore, in the light emitting device of the present invention, as described above, when the wiring to the light emitting element becomes long and when a connector or the like is interposed therebetween, the propagation characteristics deteriorate due to reflection or the like, and the waveform is distorted. Therefore, a waveform shaping circuit (clock buffer) that performs waveform shaping is provided in the drive signal line from the drive circuit in the feedback loop, preferably also in the feedback signal line, and the long wiring section and connector section are Transmits signals while performing waveform shaping.

  Therefore, it is possible to reduce the AC component of the delay due to the long wiring section and connector section to the light emitting element.

  Moreover, the spatial information detection apparatus of this invention uses the said light-emitting device as mentioned above.

  Therefore, it is possible to realize a spatial information detection device that can obtain high stability even if the light emitting element is arranged at a remote place from other circuits.

[Embodiment 1]
FIG. 1 is a block diagram showing an electrical configuration of a distance image sensor 30 which is a spatial information detection device using the light emitting device 10 according to the first embodiment of the present invention. The light emitting device 10 is used as a pair with the light receiving device 20 and has a feedback loop as shown below in order to obtain phase synchronization with the light receiving device 20. First, the light emission control signal created by the timing signal generation circuit 11 is input to the delay time adjustment circuit 12, the delay time is adjusted as described later, and further the power is amplified by the drive circuit 13 to obtain the actual drive signal. The light emitting element 14 such as an LED array is driven to light.

  A feedback signal is generated by the light emission of the light emitting element 14, the phase of the feedback signal is compared with the light emission control signal from the timing signal generation circuit 11 in the phase comparison circuit 15, and the delay is generated with an error signal corresponding to the comparison result. The delay time of the time adjustment circuit 12 is adjusted, and the phase delay between the light emitting device 10 and the light receiving device 20 is controlled to coincide with each other as described above. That is, from the output of the light emission control signal, the light emission timing of the light emitting element 14 in response thereto is controlled so as to have a certain delay time. The above configuration is the same as that of the light emitting device of FIG.

  The extraction of the feedback signal from the light emitting element 14 may be performed by converting a signal actually emitted by the light emitting element 14 into an electric signal by a photoelectric conversion element (not shown) as shown in FIG. The driving signal from the driving circuit 13 may be used. 2 and 3 show specific configurations of the drive circuits 13a and 13b in that case.

  The drive circuit 13a of FIG. 2 includes a switching element Q1 made of a MOSFET or the like and a resistor R1, and the resistor R1, the light emitting element 14 and the switching element Q1 are connected in series between a power supply VDD and GND. The light emission control signal SG from the delay time adjusting circuit 12 is input to the switching element Q1, and when the MOSFET is n-type as shown in FIG. 2, the light emission control signal SG is supplied to the gate of the switching element Q1. The light emitting element 14 emits light in response to the high level. At this time, the feedback signal FB1 taken out from the anode side of the light emitting element 14 composed of a light emitting diode becomes a low level when the light emitting element 14 is turned on and is in a phase opposite to the light emission control signal SG, and the feedback signal taken out from the cathode side. FB1 ′ is in phase with the light emission control signal SG, and both reflect the current flowing through the light emitting element 14, that is, the luminance.

  On the other hand, the drive circuit 13b of FIG. 3 includes an inverter IN1 and a resistor R1 that are logic circuits, and an output from the inverter IN1 is given to the series circuit of the light emitting element 14 and the switching element Q1. The light emission control signal SG from the delay time adjusting circuit 12 is inverted by the inverter IN1, and the light emitting element 14 is driven to light. At this time, the feedback signal FB2 taken out from the anode side of the light emitting element 14 composed of the light emitting diode becomes high level when the light emitting element 14 is turned on, and is in a phase opposite to the light emission control signal SG, and the feedback signal taken out from the cathode side. FB2 'is in phase with the light emission control signal SG, and both reflect the current flowing through the light emitting element 14, that is, the luminance. When the logic circuit is an open collector type, the circuit is substantially the same as the drive circuit 13a of FIG. By such drive circuits 13a and 13b, it is possible to feed back the actual blinking state of the light emitting element 14 instead of the light emission control signal SG.

  On the other hand, in the light receiving device 20, the reflected light from the measurement object 21 of the rectangular wave pulse light having a constant frequency radiated from the light emitting element 14 is divided into a plurality of periods by the light receiving element 22 such as a CCD array sensor. Then, the evaluation calculation circuit 23 obtains a time difference (Time of Flight) between the light emission signal and the light reception signal from the amount of light received in each period, and measures the three-dimensional shape including the depth of the measurement object 21. For the setting of the light reception period, for example, rise and fall timings of the drive signal and the like are used, and the light reception control signal created by the timing signal generation circuit 24 and the drive signal are compared by the timing adjustment circuit 25. As described above, a drive signal of the light receiving element 22 controlled so that the phase delays of the light emitting device 10 and the light receiving device 20 coincide with each other is created, and the drive circuit 26 amplifies the power and applies it to the light receiving element 22.

  It should be noted that in the light emitting device 10 of the present embodiment, the phase comparison is performed by interposing between the timing signal generating circuit 11 and the phase comparison circuit 15 and delaying the light emission control signal by a predetermined fixed time. The fixed delay circuit 16 to be input to the circuit 15 is provided. In the present embodiment, the fixed delay circuit 16 includes a CR integration circuit including a resistor 17 and a capacitor 18. Therefore, an edge detection circuit for extracting an edge from a waveform dulled by integration is provided at least at the input terminal of the phase comparison circuit 15 from the fixed delay circuit 16.

  The delay time by the fixed delay circuit 16 is set so as to correspond to a DC component (delay offset component) typified by a wiring delay that does not vary due to environmental fluctuations in the delay amount in the feedback loop. Therefore, the phase comparison circuit 15 originally compares only the AC component that fluctuates due to environmental fluctuations to be controlled by feedback control, minimizes the delay amount in the loop, and narrows the delay control range of the loop. be able to. In this way, the delay amount in the feedback loop is separated into a fixed amount and a fluctuation amount that varies depending on temperature, humidity, etc., and the fixed amount is canceled from the outside, so that the light emitting element 14 can be remotely located from other circuits. The delay control range of the DLL (delay fixed loop) can be narrowed even if the wiring delay due to the delay is increased, so that the stability of the delay characteristic can be improved, and as a result, good distance measurement performance can be obtained. Can do.

The fixed delay circuit 16 has a temperature characteristic of a metal foil resistor made of a nickel chrome metal, whereas a temperature characteristic of a general carbon resistor is +350 to -150 ppm. Then, there is one having a concentration of 0.5 ppm or less. Such a resistance element having a low temperature characteristic is used for the resistor 17, and the temperature characteristic of a ceramic capacitor or the like having a metal oxide added with titanium oxide (TiO ₂ ) as a main raw material. By using a low-capacitance element for the capacitor 18, the fixed delay circuit 16 can be configured with only passive elements without using active elements, and integration is easy.

[Embodiment 2]
FIG. 4 is a block diagram showing an electrical configuration of the light emitting device 40 according to the second embodiment of the present invention. The light emitting device 40 is similar to the light emitting device 10 described above, and corresponding portions are denoted by the same reference numerals, and description thereof is omitted. Further, the light receiving device 20 used in a pair can use the same configuration as the above-described distance image sensor 30, and is omitted in FIG. It should be noted that in the present embodiment, the timing signal generation circuit 41 includes an oscillation circuit 42, a frequency division circuit 43 that divides the oscillation signal, and a timing signal generation that generates the light emission control signal from the frequency division signal. Corresponding to the oscillation signal (using a high-speed oscillation signal as a clock signal), the light emission control signal is delayed by a predetermined fixed time. As a synchronous delay circuit 46 that is input to the phase comparison circuit 15. The synchronous delay circuit 46 includes a flip-flop, a latch circuit, and an active element such as a register constituted by these.

  Here, for example, the oscillation frequency of the oscillation circuit 42 is 160 MHz, the oscillation frequency of the frequency divider circuit 43 and the timing signal generation circuit 44 is 10 MHz, and the rising or falling timing (clock) of the oscillation signal (clock signal). 1 cycle), the timing of the light emission control signal can be adjusted with a resolution of 1/16 of the cycle, and the rise and fall timings of the oscillation signal (clock signal) (half cycle of the clock) ) Can be used to adjust the timing of the light emission control signal with a resolution of 1/32 of the cycle. Then, by adjusting the number of stages of the active elements with these resolutions, the light emission control signal can be delayed by an arbitrary time and a long time although it is stepwise. The number of stages of the active elements is adjusted at the time of shipment of the light emitting device 40, and thereafter may be fixed or variable.

  With this configuration, the delay amount is adjusted step by step in the oscillation signal (clock) in the timing signal generation circuit 41, but the fixed delay circuit 16 including the CR integration circuit which is a passive element. As a result, it is possible to suppress the delay time variation due to the temperature characteristics, and the synchronous delay circuit 46 can be easily created from the active element.

[Embodiment 3]
FIG. 5 is a block diagram showing an electrical configuration of a light emitting device 50 according to the third embodiment of the present invention. This light-emitting device 50 is similar to the above-described light-emitting device 40, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. It should be noted that in the present embodiment, a synchronous delay circuit 56 interposed between the timing signal generation circuit 41 and the phase comparison circuit 15 is an active element (three stages in FIG. 5) connected in cascade. And a selection circuit 54 that extracts the output from any one of the extraction units provided at the input / output of each stage and supplies the output to the phase comparison circuit 15. Is Rukoto. Each of the delay circuits 51 to 53 stores a signal input to the delay circuits 51 to 53 using the oscillation signal (clock) from the oscillation circuit 42 as a trigger. As the trigger, a rising edge, a falling edge, or both rising and falling edges of the oscillation signal (clock) can be used.

  Then, at the time of shipment adjustment of the distance image sensor, a fixed delay amount (DC component) of the feedback loop is measured, and the measurement result is input to a control circuit (not shown). A corresponding selection signal is supplied to the selection circuit 54, and a delay time corresponding to the fixed delay amount (DC component) is selected. Alternatively, a dip switch or the like connected to the selection circuit 54 is switched in accordance with the measurement result to obtain the selection signal. The fixed delay amount (DC component) is assumed to be unchanged, but calibration may be performed by appropriately switching with a selection signal according to aging.

  With this configuration, it is possible to cope with variations in the fixed delay amount (DC component) among apparatuses.

  It should also be noted that in this embodiment, the waveform shaping circuit (clock buffer) 57 that gives the light emitting element 14 the waveform of the driving signal from the driving circuit 13 and the feedback signal from the light emitting element 14 are the phase. A waveform shaping circuit (clock buffer) 58 provided to the comparison circuit 15 is further provided. Here, if the wiring to the light emitting element 14 becomes long as described above, and if a connector or the like is interposed therebetween, the propagation characteristics deteriorate due to reflection or the like, and the waveform is distorted. In the comparison circuit 15, it becomes difficult to perform phase comparison at the rising and falling edges of the waveform normally, and delay control may be disabled. Therefore, waveform shaping circuits (clock buffers) 57 and 58 for performing waveform shaping are provided on the drive signal line from the drive circuit 13 in the feedback loop, preferably also on the feedback signal line, and the long wiring section or connector is provided. By transmitting the signal while performing waveform shaping in the section, it is possible to reduce the AC component of the delay due to the long wiring section and connector section to the light emitting element 14. Although the delay offset (DC component) due to the waveform shaping circuits 57 and 58 increases, there is a concern that the AC component may increase due to temperature characteristics or the like, but these can be removed by the delay time adjustment circuit 12 by feedback. .

  By the way, if the input signal to the DLL is divided and input to the phase comparator, the delay amount that can be generated as a fixed delay is a delay amount that can be adjusted by the pulse width of the input signal to the DLL. Since the minimum resolution is determined, it is impossible to finely adjust the fixed delay amount. Therefore, in the present invention, as a means for generating a fine fixed delay, a timing signal generation circuit is utilized by using the fact that the drive frequency is not changed, instead of using a signal obtained by dividing the timing signal as a fixed delay. A fixed delay is generated by using the clock signal of the oscillation circuit 42 provided in 41. The relationship between the timing signal generation circuit 41 and the oscillation circuit 42 will be supplemented. The clock period used in the timing signal generation circuit 41 is obtained by dividing the clock signal obtained from the oscillation circuit 42 as a clock. Yes. For example, the clock cycle of the oscillation circuit 42 divided by 4 is used as the timing generation circuit clock.

It is a block diagram which shows the electric constitution of the distance image sensor using the light-emitting device which concerns on the 1st Embodiment of this invention. It is an electric circuit diagram which shows an example of the drive circuit of the light emitting element in the said distance image sensor. It is an electric circuit diagram which shows the other example of the drive circuit of the light emitting element in the said distance image sensor. It is a block diagram which shows the electric constitution of the light-emitting device which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the electric constitution of the light-emitting device which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the electrical structure of the typical prior art light-emitting device.

Explanation of symbols

10, 40, 50 Light emitting device 11, 41 Timing signal generating circuit 12 Delay time adjusting circuit 13, 13a, 13b Drive circuit 14 Light emitting element 15 Phase comparison circuit 16 Fixed delay circuit 17 Resistor 18 Capacitor 20 Light receiving device 21 Measuring object 22 Light receiving Element 23 Evaluation operation circuit 24 Timing signal generation circuit 25 Timing adjustment circuit 26 Drive circuit 42 Oscillation circuit 43 Frequency division circuit 44 Timing signal generation circuits 46 and 56 Synchronous delay circuits 51 to 53 Delay circuit 54 Selection circuit

Claims (6)

A light emitting element that emits light in response to a drive signal;
A timing signal generation circuit that generates a light emission control signal that indicates the emission timing of the light emitting element;
A drive circuit for generating the drive signal in response to the light emission control signal;
A phase comparison circuit that compares the phase of the feedback signal from the light emitting element and the light emission control signal and outputs an error signal corresponding to the comparison result;
A delay time adjusting circuit that is interposed between the timing signal generating circuit and the driving circuit and adjusts the timing of the light emission control signal in response to the error signal;
A light emitting device comprising: a fixed delay circuit interposed between the timing signal generation circuit and the phase comparison circuit, which delays the light emission control signal by a predetermined fixed time and inputs the delayed light emission control signal to the phase comparison circuit. .   The light-emitting device according to claim 1, wherein the fixed delay circuit includes a CR integration circuit. The timing signal generation circuit comprises an oscillation circuit, and a frequency division circuit that divides the oscillation signal to generate the light emission control signal,
2. The light emitting device according to claim 1, wherein the fixed delay circuit includes an active element that takes in the oscillation signal and delays the oscillation signal by the predetermined fixed time and inputs the delayed signal as the light emission control signal to the phase comparison circuit. . The active element is formed by cascading multiple stages,
4. The light-emitting device according to claim 3, further comprising a selection circuit that extracts an output from any one of extraction units provided at an arbitrary stage and supplies the output to the phase comparison circuit.   5. The light-emitting device according to claim 1, further comprising a waveform shaping circuit that shapes a drive signal from the drive circuit and applies the waveform to the light-emitting element.   A spatial information detection device using the light-emitting device according to claim 1.

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