JP2016211881A - Light flight time measurement device and optical range-finding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light flight time measurement device that can measure a delay time on a light reception side.SOLUTION: In a radar device, a pixel 52, which is arrayed in a light reception element receiving reflection light having irradiation light reflected upon an object, includes: a delay measurement circuit 18 that outputs a delay measurement signal in response to an input of a delay measurement start signal; and a delay measurement FB circuit 56 that outputs a delay measurement FB signal feeding back the input of the delay measurement start signal to the delay measurement circuit 18. The radar device is configured to use the delay measurement signal to measure a delay time from the pixel 52 to a time measurement unit; use the delay measurement FB signal to measure a delay time of the delay measurement signal; and measure a delay time on a light reception side.SELECTED DRAWING: Figure 19

Description

  The present invention relates to an optical time-of-flight measuring device and an optical distance measuring device.

  Conventionally, a light receiving unit including a pixel having a light receiving element that outputs a light reception signal in response to light reception, and a time for measuring a time corresponding to a timing at which the light reception signal is input from the pixel as a light flight time (TOF time) An optical time-of-flight measuring device provided with a measuring unit is provided. In the configuration in which the light emitted from the light emitting unit outputs a light reception signal in response to the reception of the reflected light reflected by the object (target), as shown in FIG. 30, the light emitting unit irradiates from the timing when the start signal is output. The time difference from the timing when the light is emitted becomes the delay time on the light emission side, and the time difference from the timing when the pixel receives the reflected light to the timing when the time measurement unit inputs the light reception signal is the delay time on the light reception side (from the pixel to the time measurement unit) Delay time). Therefore, in the configuration in which the time including the delay time is measured as the optical flight time, there is a problem that the accuracy of the optical flight time is not sufficient. In particular, when the area of the light receiving portion is increased, the influence is great. On the other hand, Patent Literature 1 discloses a technique for inputting a signal to a pixel and diagnosing the failure of the pixel.

A 0.18μm CMOS SoC for a 100m-Range 10-Frame / s 200x96-Pixel Time-of-Flight Depth Sensor Cristiano Niclass et.al.

  However, the technique disclosed in Patent Document 1 is a technique for diagnosing a failure of a pixel, and does not measure the delay time on the light receiving side described above. Under such circumstances, a configuration capable of measuring the delay time on the light receiving side is desired.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to measure a time difference from a timing at which a pixel receives light to a timing at which a time measurement unit inputs a light reception signal as a delay time on the light receiving side. It is an object of the present invention to provide an optical time-of-flight measuring device and an optical distance measuring device.

  According to the first aspect of the present invention, the light receiving unit includes a pixel having a light receiving element that outputs a light reception signal in response to light reception. The time measuring unit measures the time corresponding to the timing when the light reception signal is input from the pixel as the optical flight time. Here, the delay measurement circuit outputs a delay measurement signal that can specify the time difference from the timing when the pixel receives light to the timing when the time measurement unit inputs the light reception signal as the delay time on the light reception side.

  In other words, a delay measurement circuit that outputs a delay measurement signal that can specify the time difference from the timing at which the pixel receives light to the timing at which the time measurement unit inputs the light reception signal as a delay time on the light receiving side is provided. By using the delay measurement signal output from, the time difference from the timing when the pixel receives light to the timing when the time measurement unit inputs the light reception signal can be measured as the delay time on the light receiving side.

The functional block diagram which shows the 1st Embodiment of this invention and shows the whole structure Diagram showing irradiation light path The figure which shows the scanning range of irradiation light Diagram showing scanning cycle of irradiation light Diagram showing signal flow in ranging operation mode Flow chart showing distance measurement operation processing Diagram showing signal flow in delay measurement operation mode Flow chart showing delay measurement operation processing A diagram showing the configuration of the light receiving unit and the surrounding area Functional block diagram showing pixel configuration Electrical circuit diagram showing pixel configuration Pixel timing chart Electrical circuit diagram showing pixel configuration Pixel timing chart Functional block diagram showing the configuration of the time measurement unit Timing chart of time measurement unit The figure which shows the 2nd Embodiment of this invention and shows the relationship between the delay time from a pixel to a time measurement part, and the delay time of a delay measurement signal. A diagram showing the configuration of the light receiving unit and the surrounding area Functional block diagram showing pixel configuration Electrical circuit diagram showing pixel configuration Pixel timing chart Electrical circuit diagram showing pixel configuration Pixel timing chart Functional block diagram showing the configuration of the time measurement unit Timing chart of time measurement unit The figure which shows the 3rd Embodiment of this invention and shows the arrangement | sequence of a pixel Diagram showing pixel array Diagram showing pixel array Diagram showing the relationship between pixel column number and delay time Timing chart

(First embodiment)
A first embodiment in which the present invention is applied to a radar device that can be mounted on a vehicle will be described below with reference to FIGS. A radar device (corresponding to an optical time-of-flight measuring device and an optical distance measuring device) measures a distance (ranging) from the device itself to an object (target) around the vehicle while mounted on the vehicle. Any mode may be sufficient as a mode with which a radar apparatus is mounted in a vehicle. For example, in a mode in which the radar device is mounted on the front portion of the vehicle, the front side of the vehicle is an object detection area, and in a mode in which the radar device is mounted on the rear side of the vehicle, the rear side of the vehicle is an object detection area. Objects around the vehicle are, for example, pedestrians, preceding vehicles, succeeding vehicles, walls, and the like.

  As shown in FIG. 1, the radar apparatus 1 includes a control unit 2, a distance measurement unit 3, a delay measurement unit 4, a time measurement unit 5, a light emitting unit 6, and a light receiving unit 7. The distance measuring unit 3, the delay measuring unit 4, the time measuring unit 5 and the light receiving unit 7 can be formed on the same substrate by a CMOS (Complementary Metal Oxide Semiconductor) process.

  As shown in FIG. 2, the light emitting unit 6 includes a light source 8 and a one-dimensional scanner 9, and also includes a scanning control unit (not shown). The light source 8 is composed of, for example, a semiconductor laser diode, and emits (irradiates) pulsed laser light as irradiation light. As shown in FIG. 3, the irradiation light emitted from the light source 8 is formed in a rectangular shape whose longitudinal direction is the longitudinal direction with respect to the scanning direction SD1 (scanning light SL). The irradiation light emitted from the light source 8 has, for example, a pulse width of 4 ns and a light emission period of 4 μs.

  The one-dimensional scanner 9 includes a MEMS (Micro Electro Mechanical System) scanner and a scanner control circuit that controls driving of the MEMS scanner. When a drive instruction signal is input from a drive source (not shown), the one-dimensional scanner 9 vibrates the mirror 11 about the rotation shaft 10 as a vibration center, and performs one-dimensional scanning of irradiation light emitted from the light source 8 by a predetermined scan. This is performed in the angle range R1. Note that the scanning angle range R1 in the one-dimensional scanner 9 is, for example, −27 ° to + 27 ° as shown in FIG. The scanning cycle is, for example, 50 ms, scanning from −27 ° to + 27 ° in a time of 40 ms, and returning from + 27 ° to −27 ° in a time of 10 ms.

  Irradiation light emitted from the light source 8 passes through the collimating lens 12 and reaches the one-dimensional scanner 9 (light L1). The irradiation light that has reached the one-dimensional scanner 9 is reflected by the mirror 11, is irradiated in the direction according to the scanning angle of the mirror 11 (light L2), and when it reaches an object around the vehicle, it is reflected by the object. The irradiation light reflected by the object passes through the light receiving lens 13 as reflected light (signal light reflected by the object) and reaches the light receiving unit 7 (light L3). Since the irradiation light is shaped in a rectangular shape as described above, the reflected light shaped in a rectangular shape whose longitudinal direction is the longitudinal direction with respect to the scanning direction SD2 of the reflected light arrives at the light receiving unit 7. (Reflected light RL). In addition, the length of the reflected light formed in the rectangular shape in the longitudinal direction is longer than the length in the short direction of the light receiving surface RP formed in the rectangular shape. The length in the longitudinal direction is set.

  The scanning control unit detects the scanning angle of the one-dimensional scanner 9, controls the emission of irradiation light from the light source 8 based on the detected scanning angle, and controls the scanning of irradiation light by the one-dimensional scanner 9. Further, the scanning control unit inputs a vehicle speed signal (vehicle speed pulse) indicating the traveling speed (vehicle speed) of the vehicle on which the radar device 1 is mounted from a vehicle speed sensor, and a light source according to the vehicle speed specified by the input vehicle speed signal. 8 and the one-dimensional scanner 9 are controlled.

  Specifically, the scanning control unit changes the light emission intensity from the light source 8 according to the vehicle speed, relatively reduces the light emission intensity when the vehicle speed is relatively slow, and changes the light emission intensity when the vehicle speed is relatively fast. Increase relatively. In addition, the scanning control unit changes the scanning angle range R1 of the one-dimensional scanner 9 according to the vehicle speed, and when the vehicle speed is relatively slow, sets the scanning angle range R1 relatively wide so that the vehicle speed is relatively high. When the speed is high, the scan angle range R1 is set relatively narrow. If the vehicle speed is relatively slow, there is a high possibility that there are pedestrians around the vehicle, and it is necessary to consider the presence of pedestrians in the vicinity. At this time, by relatively reducing the emission intensity, it is possible to avoid irradiating the pedestrian with irradiation light having high intensity, and by setting the scanning angle range R1 relatively wide, Presence can be detected quickly. On the other hand, if the vehicle speed is relatively high, it is necessary to consider the presence of a preceding vehicle. At this time, it is possible to detect a distant preceding vehicle by relatively increasing the emission intensity, and by setting the scanning angle range R1 to be relatively narrow, it is highly possible that the preceding vehicle does not exist. Can be excluded from the scanning range, and a distant preceding vehicle can be detected quickly.

  Now, in this type of radar device 1, as described in [Problems to be Solved by the Invention], the time measuring unit 5 receives the light reception signal from the timing when each pixel constituting the light receiving unit 7 receives light. It is desired to measure the time difference from the input timing as the delay time on the light receiving side (delay time from the pixel to the time measuring unit 5). In view of such circumstances, the radar device 1 is configured as follows.

  The control unit 2 includes a microcomputer, and controls the operation of the radar device 1 by executing a control program stored in advance. The control unit 2 selectively switches between the ranging operation mode and the delay measurement operation mode as the operation mode of the radar device 1. The control unit 2 operates the radar apparatus 1 in the distance measurement operation mode by selecting the distance measurement operation mode, and operates the radar apparatus 1 in the delay measurement operation mode by selecting the delay measurement operation mode.

  When the ranging operation mode is selected, the control unit 2 outputs a ranging instruction signal to the distance measuring unit 3 as shown in FIG. When the distance measuring unit 3 receives a ranging instruction signal from the control unit 2, the distance measuring unit 3 outputs a ranging start signal to the light emitting unit 6, the light receiving unit 7, and the time measuring unit 5, and the light emitting unit 6, the light receiving unit 7, and the time measuring unit. 5 to control the distance measuring operation.

  When receiving the distance measurement start signal from the distance measuring unit 3, the light emitting unit 6 emits (irradiates) irradiation light. When receiving the distance measurement start signal from the distance measuring unit 3, the light receiving unit 7 waits for light reception (incident) and receives reflected light reflected by the object or disturbance light such as sunlight (background). When light reception is detected, a light reception signal corresponding to the light reception intensity (light reception level) is output to the time measurement unit 5. When the time measurement unit 5 inputs a distance measurement start signal from the distance measurement unit 3, the time measurement unit 5 waits for input of the light reception signal from the light reception unit 7, and when the light reception signal is input from the light reception unit 7, timing when the distance measurement start signal is input. The optical flight time (TOF time) is measured based on the time difference from when the received light signal is input to the time when the received light signal is input, and the measured TOF time is output to the distance measuring unit 3. Then, when the TOF time is input from the time measuring unit 5, the distance measuring unit 3 calculates distance information based on the input TOF time, and outputs the calculated distance information to the control unit 2.

  When the radar apparatus 1 is operating in the ranging operation mode, as shown in FIG. 6, the radar apparatus 1 performs a ranging operation process. When the radar apparatus 1 starts the operation in the distance measurement operation mode, the radar apparatus 1 starts standby of the distance measurement operation (pre-processing necessary for performing the distance measurement operation) (S1). When the radar apparatus 1 normally finishes the standby of the distance measuring operation, the radar apparatus 1 emits the irradiation light from the light emitting unit 6 (S2). When the light receiving signal is input from the light receiving unit 7 to the time measuring unit 5 in response to light reception, the radar device 1 measures the TOF time by the time measuring unit 5 (S3), and the measured TOF time is timed. When input from the measuring unit 5 to the distance measuring unit 3, the distance measuring unit 3 accumulates the number of outputs per TOF time (S4). The radar apparatus 1 determines whether or not a predetermined time (light receiving operation time) specified in advance has elapsed (S5), and determines that the specified time has not elapsed (S5: NO). Then, the process returns to the above-described step S3, and step S3 and subsequent steps are repeated.

  When the radar device 1 determines that the specified time has elapsed (S5: YES), the control unit 2 determines whether or not the predetermined number of repetitions (repetition of the light receiving operation) has been completed (S6). If it is determined that the specified number of repetitions has not been completed (S6: NO), the process returns to step S2 described above, and steps S2 and after are repeated. When the radar device 1 determines that the repetition of the specified number of times has been completed (S6: YES), the distance measurement unit 3 calculates the distance information based on the accumulated result of the number of outputs for each TOF time (S7), and the measurement is performed. The operation in the distance operation mode is terminated.

  On the other hand, as shown in FIG. 7, the control unit 2 outputs a delay measurement instruction signal to the delay measurement unit 4 when the delay measurement operation mode is selected. When the delay measurement instruction signal is input from the control unit 2, the delay measurement unit 4 outputs a delay measurement start signal to the light receiving unit 7 and the time measuring unit 5, and controls the delay measurement operation by the light receiving unit 7 and the time measuring unit 5. . When the delay measuring unit 4 inputs a delay time (delay time from the pixel to the time measuring unit 5) from the time measuring unit 5, the delay measuring unit 4 calculates delay correction information based on the input delay time, and calculates the calculated delay. The correction information is output to the control unit 2.

  When the radar apparatus 1 is operating in the delay measurement operation mode, the radar apparatus 1 performs a delay measurement operation process as shown in FIG. When the radar apparatus 1 starts the operation in the delay measurement operation mode, the radar apparatus 1 starts standby of the delay measurement operation (pre-processing necessary for performing the delay measurement operation) (S11). When the radar apparatus 1 normally ends standby for the delay measurement operation and a delay measurement signal is input from the light receiving unit 7 to the time measurement unit 5, the radar device 1 measures the delay time by the time measurement unit 5 (S12). When the delay time is input from the time measurement unit 5 to the delay measurement unit 4, the delay correction information is calculated by the delay measurement unit 4 (S13), and the operation in the delay measurement operation mode is terminated.

  In this way, the control unit 2 receives the distance information input from the distance measurement unit 3 when the distance measurement operation mode is selected and the delay input from the delay measurement unit 4 when the delay measurement operation mode is selected. Based on the correction information, the distance from the device to an object around the vehicle is measured.

  Hereinafter, a configuration in which the radar apparatus 1 performs switching between the operation in the ranging operation mode and the operation in the delay measurement operation mode will be described. As shown in FIG. 9, the light receiving unit 7 includes one or more pixels 14 arranged in the horizontal direction and the vertical direction, and a plurality of pixels 14 arranged in a two-dimensional matrix (6 × 4 in the example of FIG. 9). Has been configured.

  The plurality of pixels 14 are connected to the delay measurement unit 4 via the selection control line 15 for each column. The delay measurement unit 4 outputs the operation select signal to each pixel 14 via the selection control line 15 to switch the operation of each pixel 14 between the distance measurement operation and the delay measurement operation, and to generate a delay measurement start signal. Delay measurement is performed by outputting to each pixel 14 via the selection control line 15. The delay measurement unit 4 outputs the delay measurement start signal and the operation select signal to the time measurement unit 5 in response to outputting the delay measurement start signal and the operation select signal to each pixel 14.

  The plurality of pixels 14 are connected to the time measuring unit 5 via signal output lines 16 for each row. When the radar device 1 is operating in the distance measurement operation mode, the time measurement unit 5 inputs a light reception signal as a pixel output signal from each pixel 14 via the signal output line 16, and the radar device 1 is in the delay measurement operation mode. When the operation is performed, a delay measurement signal is input through the signal output line 16 as a pixel output signal from each pixel 14.

  As shown in FIG. 10, each pixel 14 includes a SPAD (Single Photon Avalanche Diode) 17 as a light receiving element that responds to light reception, a delay measurement circuit 18 that inputs a delay measurement start signal from the delay measurement unit 4, An operation selector 19 that selectively switches and outputs a signal input from the SPAD 17 and a signal input from the delay measurement circuit 18, and a readout circuit 20 that outputs the signal input from the operation selector 19 as a pixel output signal.

The SPAD 17 is an avalanche photodiode that operates in a Geiger mode by applying a reverse bias voltage equal to or higher than a breakdown voltage (breakdown voltage) V _BR between its anode and cathode, and can detect light reception of a single photon. . In the example of FIG. 10, one pixel 14 has one SPAD 17, but one pixel 14 may have a plurality of (for example, four) SPADs 17. In that case, a configuration in which a plurality of (same as the number of SPAD 17) delay measurement circuits 18 are individually provided for the plurality of SPADs 17 or a configuration in which one delay measurement circuit 18 is provided in common for the plurality of SPADs 17 is possible. But it ’s okay. As described above, in a configuration in which one pixel 14 has a plurality of SPADs 17, a detection method is adopted in which reflected light is simultaneously received by some SPADs 17 among the plurality of SPADs 17. can do. That is, by adopting such a detection method, the possibility that a plurality of SPADs 17 erroneously detect at the same time becomes extremely low, and the erroneous detection of the pixels 14 can be reduced.

Next, the electrical configuration of the pixel 14 will be described. here,
(1) Configuration in which operation selector 19 switches output in conjunction with input of operation select signal (2) Configuration in which operation selector 19 switches output in conjunction with input of delay measurement start signal will be described.

FIG. 11 is an electric circuit diagram of the pixel 14 adopting a configuration in which the operation selector 19 switches the output in conjunction with the input of the operation select signal. The delay measurement circuit 18 includes an inverter 21. The cathode of SPAD 17 is connected to power supply voltage V _DD2 , and the anode of SPAD 17 is grounded via quench resistor 22. The quench resistor 22 generates an avalanche current when a photon is incident while a reverse bias voltage V _SPAD equal to or higher than the breakdown voltage V _BR is applied between the anode and the cathode of the _SPAD 17, and once this avalanche current is generated. Since it continues to flow, the reverse bias voltage V _SPAD is lowered to the breakdown voltage V _BR or less to act to stop the avalanche current. A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) may be used instead of the resistor. A connection point between the anode of the SPAD 17 and the quench resistor 22 is connected to the first input terminal of the operation selector 19 via the inverter 23.

The output terminal of the inverter 21 constituting the delay measurement circuit 18 is connected to the second input terminal of the operation selector 19. The read circuit 20 includes a P-channel MOSFET (P-type transistor) 26 and an N-channel MOSFET (N-type transistor) 27. The drain of the P-type transistor 26 is connected to the power supply voltage V _DD1 and the source thereof is connected to the drain of the N-type transistor 27. The N-type transistor 27 has its drain connected to the source of the P-type transistor 26 and its source grounded. The output terminal of the operation selector 19 is connected to a connection point between the gate of the P-type transistor 26 and the gate of the N-type transistor 27. A connection point between the source of the P-type transistor 26 and the drain of the N-type transistor 27 is an output terminal of the pixel 14.

The pixel 14 configured as described above operates as shown in FIG. The operation selector 19 is in a state capable of outputting a signal input to the first input terminal when the operation select signal (V _EN ) is at a low level, and the signal (V _S1 ) is output to the first signal according to the response of the SPAD 17. When input to the input terminal, the input signal (V _S1 ) is output to the reading circuit 20. As a result, the pixel 14 outputs a light reception signal corresponding to the response of the SPAD 17 as a pixel output signal (V _OUT ) from the readout circuit 20 (see t1 in FIG. 12). On the other hand, the operation selector 19 is in a state capable of outputting a signal input to the second input terminal when the operation select signal (V _EN ) is at a high level, and uses the delay measurement start signal (V _TEST ) as a pulse signal. When input to the second input terminal, the input delay measurement start signal (V _TEST ) is output to the readout circuit 20. As a result, the pixel 14 outputs a signal similar to the light reception signal corresponding to the response of the SPAD 17 from the readout circuit 20 as the pixel output signal (V _OUT ) (see t2 in FIG. 12).

FIG. 13 shows an electric circuit diagram of the pixel 14 adopting a configuration in which the operation selector 19 switches the output in conjunction with the input of the delay measurement start signal. The delay measurement circuit 18 includes a first delay measurement circuit 31 in which a first signal delay time (td1) is set, and a second delay circuit 32 in which a second signal delay time (td2) is set. And an inverter 33 and a D-type flip-flop circuit 34. The first signal delay time (td1) is set longer than the second signal delay time (td2). The output terminal of the second delay circuit 32 is connected to the second input terminal of the operation selector 19 via the inverter 33. The D-type flip-flop circuit 34 has its input terminal D connected to the power supply voltage V _DD1 , its output terminal Q connected to the operation selector 19, and connected to its own reset terminal via the first delay circuit 31. Has been. That is, the delay measurement circuit 18 causes the operation selector 19 to input the operation select signal (V _EN ) in response to the input of the delay measurement start signal (V _TEST ).

The pixel 14 having the above-described configuration operates as shown in FIG. The operation selector 19 is in a state capable of outputting a signal input to the first input terminal when the operation select signal (V _EN ) is at a low level, and the signal (V _S1 ) is output to the first signal according to the response of the SPAD 17. When input to the input terminal, the input signal (V _S1 ) is output to the reading circuit 20. As a result, the pixel 14 outputs a light reception signal (V _OUT ) corresponding to the response of the SPAD 17 as a pixel output signal (V _OUT ) from the readout circuit 20 (see t11 in FIG. 14). On the other hand, when the operation select signal (V _EN ) is low level and the delay measurement start signal (V _TEST ) is input to the delay measurement circuit 18, the operation selector 19 changes the operation select signal (V _EN ) from low level to high level. By changing to, the signal input to the second input terminal can be output, and when the delay measurement start signal is input to the second input terminal as a pulse signal, the input delay measurement signal (V _TEST ) To the readout circuit 20. As a result, the pixel 14 outputs a signal similar to the light reception signal corresponding to the response of the SPAD 17 from the readout circuit 20 as the pixel output signal (V _OUT ) (see t12 in FIG. 14). Thereafter, when a certain time (the signal delay time (td1) of the first delay circuit 31) elapses after the operation select signal (V _EN ) changes from the low level to the high level, the operation select signal (V _EN ) becomes the high level. Changes to the low level and returns to the state before the delay measurement start signal (V _TEST ) is input to the delay measurement circuit 18 (see t13 in FIG. 14). In the configuration in which the operation selector 19 switches the output in conjunction with the input of the delay measurement start signal, the wiring for propagating the operation select signal is different from the configuration in which the operation selector 19 switches the output in conjunction with the input of the operation select signal. Therefore, a large light receiving area (aperture ratio) in the pixel 14 can be secured.

  Next, the configuration of the time measuring unit 5 will be described. The time measurement unit 5 outputs a time difference between the input timings of the two signals as a digital signal, and performs a distance measurement operation and a delay measurement operation with a substantially common circuit. The time measuring unit 5 switches the output destination of the measurement result between the distance measuring unit 3 and the delay measuring unit 4 by inputting the operation control signal. As shown in FIG. 15, the time measuring unit 5 includes a PLL (Phase Locked Loop) 41, a TDC (Time to Digital Converter) 42, and a measurement control circuit 43. The PLL 41 generates a time reference clock and outputs the generated time reference clock to the TDC 42. The TDC 42 uses the time reference clock input from the PLL 41 and outputs the time difference between the input timings of the two signals to the measurement control circuit 43 as a digital signal.

  When the radar apparatus 1 is operating in the ranging operation mode, the measurement control circuit 43 receives the pixel output signal (light reception signal) from the timing at which the ranging start signal is input, as shown in FIG. The time difference until the timing (t21 to t22 in FIG. 16) is measured as the TOF time, and the measured TOF time is output to the distance measuring unit 3. On the other hand, when the radar apparatus 1 is operating in the delay measurement operation mode, the measurement control circuit 43 receives the pixel output signal (delay measurement signal) from the timing when the delay measurement start signal is input, as shown in FIG. 16 is measured as a delay time from the pixel 14 to the time measuring unit 5, and the measured delay time is output to the delay measuring unit 4.

  As described above, according to the first embodiment, the following operational effects can be obtained. Since the radar apparatus 1 includes the delay measurement circuit 18 that outputs the delay measurement signal in response to the input of the delay measurement start signal, the pixel 14 emits light by using the delay measurement signal output from the delay measurement circuit 18. The time difference from the timing of receiving light to the timing at which the time measuring unit 5 inputs the light receiving signal can be measured as the delay time on the light receiving side. For example, by correcting the distance information based on the delay time on the light receiving side, it is possible to improve the accuracy of distance measurement from the own device to an object around the vehicle. For example, if a reference time serving as a failure determination criterion is set in advance, the occurrence of a failure can be specified by determining that the delay time on the light receiving side is longer than the reference time.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, description is abbreviate | omitted about the same part as above-mentioned 1st Embodiment, and a different part is demonstrated. The delay time from the pixel 14 to the time measurement unit 5 measured according to the first embodiment includes the delay time of the delay measurement signal propagated from the delay measurement unit 4 to each pixel 14 as shown in FIG. In this regard, the second embodiment differs from the first embodiment in that the pixel outputs a delay measurement feedback (FB) signal to eliminate the influence of the delay time of the delay measurement signal.

  In the second embodiment, as shown in FIG. 18, a light receiving unit 51 is provided instead of the light receiving unit 7 described in the first embodiment. The light receiving unit 51 includes one or more pixels 52 arranged in the horizontal direction and the vertical direction, and a plurality of pixels 52 arranged in a two-dimensional matrix. The plurality of pixels 52 are connected to the delay measurement unit 4 via the selection control line 53 for each column. The delay measurement unit 4 outputs the operation select signal to each pixel 52 via the selection control line 53, thereby switching the operation of each pixel 52 between the distance measurement operation and the delay measurement operation, and a delay measurement start signal. Delay measurement is performed by outputting to each pixel 52 via the selection control line 53. The plurality of pixels 52 are connected to the delay measuring unit 4 via the FB signal output line 54 for each column. In response to outputting the delay measurement start signal and the operation select signal to each pixel 52, the delay measurement unit 4 outputs the delay measurement start signal and the operation select signal to the time measurement unit 5 and outputs the delay measurement FB from each pixel 52. In response to inputting a signal, the delay measurement FB signal is output to the time measurement unit 5.

  The plurality of pixels 52 are connected to the time measuring unit 5 via signal output lines 55 for each row. When the radar device 1 is operating in the ranging operation mode, the time measuring unit 5 inputs a light reception signal as a pixel output signal from each pixel 52 via the signal output line 55, and the radar device 1 is in the delay measurement operation mode. When the operation is performed, a delay measurement signal is input via the signal output line 55 as a pixel output signal from each pixel 52.

  As illustrated in FIG. 19, the pixel 52 includes the SPAD 17 described in the first embodiment, the delay measurement circuit 18, the operation selector 19, and the readout circuit 20, and also includes a delay measurement FB circuit 56. In the pixel 52 having the delay measurement FB circuit 56, the delay time until the delay measurement start signal is output from the delay measurement unit 4 and input to each pixel 52, and the delay measurement FB signal is output from each pixel 52 and delayed. It is desirable to design (lay out) the time difference from the delay time until it is input to the measurement unit 4 to be a predetermined value or less. In the pixel 52, the delay time from when the delay measurement start signal is output from the delay measurement unit 4 to when it is input to the time measurement unit 5, the delay measurement start signal is output from the delay measurement unit 4 to each pixel 52. The delay time until input and the delay measurement FB signal are designed to be equal to or shorter than at least one of the delay times from the output from each pixel 52 to the time measurement unit 5 ( Layout) is desirable.

Next, the electrical configuration of the pixel 52 will be described. here,
(1) Configuration in which delay measurement start signal and delay measurement FB signal are separate wirings (2) Configuration in which delay measurement start signal and delay measurement FB signal are the same wiring will be described.

(1) Configuration in which Delay Measurement Start Signal and Delay Measurement FB Signal are Separated Wirings FIG. 20 is an electric circuit diagram of the pixel 51 having a configuration in which the delay measurement start signal and the delay measurement FB signal are separately wired. Show. The delay measurement FB circuit 56 includes an inverter 61. The input terminal of the inverter 61 is connected to the output terminal of the inverter 25 of the delay measurement circuit 18.

The pixel 52 configured as described above operates as shown in FIG. The operation selector 19 is capable of outputting a signal input from the first input terminal when the operation select signal (V _EN ) is at a low level, and the signal (V _S1 ) is input to the first input according to the response of the SPAD 17. When input to the terminal, the input signal (V _S1 ) is output to the reading circuit 20. As a result, the pixel 52 outputs a light reception signal corresponding to the response of the SPAD 17 as a pixel output signal (V _OUT ) from the readout circuit 20 (see t41 in FIG. 21). On the other hand, when the operation select signal (V _EN ) is at a high level, the operation selector 19 can output a signal input from the second input terminal, and the delay measurement start signal (V _TEST ) is used as a pulse signal. When input to the input terminal 2, the input delay measurement start signal (V _TEST ) is output to the readout circuit 20. As a result, the pixel 52 outputs, as a pixel output signal (V _OUT ), a signal (V _OUT ) similar to the light reception signal corresponding to the response of the SPAD 17 from the readout circuit 20 (see t42 in FIG. 21). The delay measurement FB circuit 56 outputs a delay measurement FB signal (V _DLY ) in response to the delay measurement start signal (V _TEST ) being input from the delay measurement circuit 18 to the operation selector 19. That is, the delay of the round trip wiring influences the time difference from the timing when the delay measurement unit 4 outputs the delay measurement start signal (V _TEST ) to the timing when the delay measurement FB signal (V _DLY ) is input. The unit 4 measures the delay time of the delay measurement signal by measuring the time difference.

(2) Configuration in which delay measurement start signal and delay measurement FB signal are made the same wiring FIG. 22 is an electric circuit diagram of pixel 52 having a configuration in which the delay measurement start signal and the delay measurement FB signal are made the same wiring. Show. The delay measurement FB circuit 56 includes a delay circuit 71, an inverter 72, and a D-type flip-flop circuit 73. The D-type flip-flop circuit 73 has its input terminal D connected to the power supply voltage V _DD1 , its output terminal Q connected to the inverter 72, and connected to its own reset terminal via the delay circuit 71.

The pixel 52 configured as described above operates as shown in FIG. The operation selector 19 is capable of outputting a signal input from the first input terminal when the operation select signal (V _EN ) is at a low level, and the signal (V _S1 ) is input to the first input according to the response of the SPAD 17. When input to the terminal, the input signal (V _S1 ) is output to the reading circuit 20. As a result, the pixel 52 outputs a light receiving signal corresponding to the response of the SPAD 17 as a pixel output signal (V _OUT ) from the readout circuit 20 (see t51 in FIG. 23). On the other hand, when the operation select signal (V _EN ) is at a high level, the operation selector 19 can output a signal input from the second input terminal, and the second operation measurement signal (V _TEST ) is used as a pulse signal. The input delay measurement signal (V _TEST ) is output to the readout circuit 20. As a result, the pixel 52 outputs a signal similar to the light reception signal corresponding to the response of the SPAD 17 from the readout circuit 20 as the pixel output signal (V _OUT ) (see t52 in FIG. 23). Thereafter, the delay measurement FB circuit 56 outputs the delay measurement signal (V _TEST ) as a delay measurement FB signal (see t53 in FIG. 23). That is, the pixel 52 outputs the delay measurement signal and the delay measurement FB signal through the same wiring.

  Next, the configuration of the time measuring unit 5 will be described. As shown in FIG. 24, the time measurement unit 5 is different from the first embodiment in that a delay measurement FB signal is input. When the radar apparatus 1 is operating in the ranging operation mode, the measurement control circuit 43 performs ranging as in FIG. 15A described in the first embodiment, as shown in FIG. The time difference (t61 to t62 in FIG. 25) between the timing at which the start signal is input and the timing at which the pixel output signal (light reception signal) is input is measured as the TOF time, and the measured TOF time is output to the distance measuring unit 3. On the other hand, when the radar apparatus 1 is operating in the delay measurement operation mode, the measurement control circuit 43 receives the delay measurement FB signal from the timing when the delay measurement start signal is input, as shown in FIG. The timing corresponding to half of the time is specified, and the time difference (t71 to t72 in FIG. 25) from the timing when the delay measurement start signal is input to the specified timing is measured as the delay time of the delay measurement signal, and the specification is performed. The time difference (t72 to t73 in FIG. 25) from the timing when the pixel output signal (delay measurement signal) is input is measured as the delay time from the pixel 52 to the time measurement unit 5, and the measured delay time is measured as a delay. Output to part 4. The configuration in which the delay measurement instruction signal and the delay measurement FB signal are the same wiring has an advantage of reducing the wiring compared to the configuration in which the delay measurement instruction signal and the delay measurement FB signal are separate wirings. Accordingly, a large light receiving area (aperture ratio) in the pixel 52 can be secured.

  As described above, according to the second embodiment, the following operational effects can be obtained. Since the delay measurement FB circuit 56 for outputting the delay measurement FB signal for feeding back the input of the delay measurement start signal to the delay measurement circuit 18 is provided, the delay time of the delay measurement signal can be measured, and the time measurement from the pixel 52 is performed. By subtracting the delay time of the delay measurement signal from the delay time up to the unit 5, the delay time on the light receiving side can be measured more accurately.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS. In addition, description is abbreviate | omitted about the same part as above-mentioned 1st Embodiment, and a different part is demonstrated. In the first embodiment, all the pixels 14 constituting the light receiving unit 7 have the delay measurement circuit 18, but in the third embodiment, some of all the pixels constituting the light receiving unit are delayed. This embodiment is different from the first embodiment in that a dummy pixel having a measurement circuit or different from all the pixels constituting the light receiving unit has a delay measurement circuit.

  In the configuration shown in FIG. 26, in the light receiving unit 81, the pixel 82 belonging to the uppermost row among the plurality of pixels 82 and 83 arranged in a two-dimensional matrix is the same as the pixel 14 described in the first embodiment. The other pixels 83 are pixels that do not have the delay measurement circuit 18. When there are many pixels in the horizontal direction, the delay time in the vertical direction is assumed to be constant or set as a predetermined delay time, and only the horizontal delay time is measured, thereby reducing the amount of memory and measuring the delay time. Or save time. Further, as the wiring is reduced, a larger light receiving area (aperture ratio) at the light receiving portion 81 can be secured. The pixel 82 having the delay measurement circuit 18 is not limited to be arranged in the uppermost row, and the pixel 82 having the delay measurement circuit 18 may be arranged in the lowest row, or the uppermost row. It may be arranged in a line in the middle between and the lowest line.

  In the configuration shown in FIG. 27, in the light receiving unit 91, among the plurality of pixels 92 and 93 arranged in a two-dimensional matrix, the pixels 92 belonging to both the highest and lowest rows are pixels having delay measurement circuits. Other pixels 93 are pixels having no delay measurement circuit. In this case as well, it is possible to reduce the amount of memory and the time required for measuring the delay time, and to secure a large light receiving area (aperture ratio) in the light receiving portion 91 as the wiring is reduced. . In addition, since the delay time is measured in the pixels 92 belonging to the uppermost row and the lowermost row, the delay time in the vertical direction can be measured. Compared with the configuration shown in FIG. It can be measured more accurately.

  In the configuration shown in FIG. 28, a dummy pixel row is provided near the upper part of the light receiving unit 101 in the horizontal direction. The plurality of pixels 102 constituting the dummy pixel row are pixels having the delay measurement circuit 18, and the plurality of pixels 103 arranged in a two-dimensional matrix in the light receiving unit 101 are pixels having no delay measurement circuit. By providing the dummy pixel row outside the light receiving unit 101, the delay time in the vertical direction can be measured while maintaining the light receiving area (aperture ratio) in the light receiving unit 101. The dummy pixel row is not limited to the configuration in the vicinity of the upper part of the light receiving unit 101 in the horizontal direction, and the dummy pixel row may be configured in the vicinity of the lower part of the light receiving unit 101 in the horizontal direction. 101 may be provided in both the upper vicinity and the lower vicinity in the horizontal direction. Note that the delay measurement FB circuit 56 described in the second embodiment may also be provided in a part of all the pixels constituting the light receiving unit in the same manner as the delay measurement circuit 18. It may be provided in a dummy pixel row in the upper vicinity or the lower vicinity.

  Further, as shown in FIG. 29, the correspondence between the column number for each row and the delay time may be held as a linear function of the column number, and the delay time may be measured from the linear function. In the configuration in which the correspondence between the column number for each row and the delay time is held as a linear function of the column number, the amount of memory is reduced compared to the configuration in which the delay times for all the pixels constituting the light receiving unit are held. Can do. The correspondence between the row number, the column number, and the delay time may be held as a quadratic function of the row number and the column number, and the delay time may be measured from the quadratic function.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be modified or expanded as follows.
In this embodiment, although the structure which measures the distance from the radar apparatus mounted in the vehicle to the object around the vehicle was illustrated, you may apply to uses other than a vehicle.
In the first embodiment, the configuration in which the delay measurement circuit 18 and the operation selector 19 are arranged inside the pixel 14 is exemplified, but the configuration in which the delay measurement circuit 18 and the operation selector 19 are arranged outside the pixel 14 may be used. . In the second embodiment, the configuration in which the delay measurement circuit 18, the operation selector 19, and the delay measurement FB circuit 56 are arranged inside the pixel 52 is exemplified. However, the delay measurement circuit 18 and the delay measurement FB circuit 56 are pixels. The structure arrange | positioned inside 52 may be sufficient. With this configuration, wiring in the pixel can be reduced.

  In the third embodiment, the configuration in which the pixels belonging to some of the plurality of pixels arranged in a two-dimensional matrix are pixels having the delay measurement circuit 18 is exemplified. However, in the two-dimensional matrix, A configuration may be adopted in which pixels belonging to some of the plurality of arranged pixels are pixels having the delay measurement circuit 18. Further, a configuration may be adopted in which at least one pixel at four corners among the plurality of pixels arranged in a two-dimensional matrix is a pixel having the delay measurement circuit 18.

  In the drawing, 1 is a radar device (light time-of-flight measuring device, optical distance measuring device), 2 is a control unit, 3 is a distance measuring unit, 4 is a delay measuring unit, 5 is a time measuring unit, 6 is a light emitting unit, 7 Is a light receiving unit, 14 and 52 are pixels, 18 is a delay measurement circuit, and 56 is a delay measurement feedback circuit.

Claims (28)

A light receiving section (7) including a pixel (14, 52) having a light receiving element (17) that outputs a light receiving signal in response to light reception;
A time measuring unit (5) that measures the time corresponding to the timing at which the light reception signal is input from the pixel as the optical flight time, and
When a delay measurement start signal is input, a delay measurement signal is output that can specify a time difference from the timing at which the pixel receives light to the timing at which the time measurement unit inputs the light reception signal as a delay time on the light receiving side. An optical time-of-flight measuring device (1) comprising a circuit (18). The optical time-of-flight measuring device according to claim 1,
An operation selector (19) that selectively switches between the output of the light reception signal from the pixel and the output of the delay measurement signal, and at least a part of the wiring through which the light reception signal propagates and the wiring through which the delay measurement signal propagates An optical time-of-flight measuring device, wherein at least a part of the optical time-of-flight is provided in common. The optical time-of-flight measuring device according to claim 2,
The optical time-of-flight measuring device, wherein the operation selector selectively switches between a state in which the output of the light reception signal is permitted and a state in which the output of the delay measurement signal is permitted according to an input of an operation select signal. The optical time-of-flight measuring device according to claim 3,
The delay measurement circuit inputs the operation select signal to the operation selector according to the input of the delay measurement start signal,
The optical time-of-flight measurement device, wherein the operation selector selectively switches between a state of permitting the output of the received light signal and a state of permitting the output of the delay measurement signal according to the input of the operation select signal. . In the optical time-of-flight measuring device according to any one of claims 1 to 4,
The time measuring unit measures a delay time from the pixel to the time measuring unit based on a time difference from a timing at which the delay measurement start signal is input to a timing at which the delay measurement signal is input. Time-of-flight measuring device. In the optical time-of-flight measuring device according to any one of claims 1 to 5,
An optical time-of-flight measurement apparatus comprising a delay measurement feedback circuit (56) for outputting a delay measurement feedback signal for feeding back an input of the delay measurement start signal to the delay measurement circuit. The optical time-of-flight measuring device according to claim 6,
An optical time-of-flight measurement apparatus, wherein at least a part of the wiring through which the delay measurement start signal propagates and at least a part of the wiring through which the delay measurement feedback signal propagates are provided in common. The optical time-of-flight measuring device according to claim 7,
An optical time-of-flight measurement characterized in that at least a part of the wiring through which the delay measurement start signal propagates and at least a part of the wiring through which the delay measurement feedback signal propagates are short-circuited in or near the pixel. apparatus. In the optical time-of-flight measuring device according to any one of claims 6 to 8,
The delay measurement feedback circuit starts to output the delay measurement feedback signal in response to an input of the delay measurement start signal to the delay measurement circuit. The optical time-of-flight measuring device according to any one of claims 6 to 9,
A time difference between a delay time until the delay measurement start signal is input to the delay measurement circuit and a delay time until the delay measurement feedback signal is output from the delay measurement feedback circuit and input to the time measurement unit. An optical time-of-flight measuring device designed to be less than or equal to a predetermined value. The optical time-of-flight measuring device according to any one of claims 6 to 10,
The delay time until the delay measurement start signal is input to the time measurement unit, the delay time until the delay measurement start signal is input to the delay measurement circuit, and the delay measurement feedback signal are the delay measurement feedback circuit. An optical time-of-flight measuring device designed to be equal to or shorter than at least one of the delay times from the output to the time measuring unit. The optical time-of-flight measuring device according to any one of claims 6 to 11,
The time measuring unit measures a delay time of the delay measurement signal based on a time difference from a timing at which the delay measurement start signal is input to a timing at which the delay measurement feedback signal is input. apparatus. In the optical time-of-flight measuring device according to any one of claims 1 to 12,
An optical time-of-flight measuring apparatus, wherein the light receiving element is an avalanche photodiode. The optical time-of-flight measuring device according to claim 13,
The optical time-of-flight measuring apparatus, wherein the light receiving element is a single photon avalanche photodiode operating in a Geiger mode. The optical time-of-flight measuring device according to claim 14,
The pixel includes a quench resistor (22) for quenching a single photon avalanche photodiode, and a readout circuit (20) for outputting the received light signal as a digital signal. . In the optical time-of-flight measuring device according to any one of claims 1 to 15,
The light receiving unit includes the pixel having the delay measurement circuit in one horizontal row or one vertical column of a two-dimensional array. In the optical time-of-flight measuring device according to any one of claims 1 to 15,
The light receiving unit includes the pixels having the delay measurement circuit in one row in both horizontal upper and lower rows or in one column on both right and left sides in a two-dimensional array. In the optical time-of-flight measuring device according to any one of claims 1 to 15,
The optical time-of-flight measuring apparatus, wherein the light receiving unit includes the pixel having the delay measuring circuit in at least one of four corners of a two-dimensional array. In the optical time-of-flight measuring device according to any one of claims 1 to 15,
An optical time-of-flight measurement apparatus comprising a pixel having the delay measurement circuit as a dummy pixel separately from the light receiving unit. The optical time-of-flight measuring device according to any one of claims 1 to 19,
The optical time-of-flight measuring apparatus, wherein the light receiving unit and the time measuring unit are formed on the same chip. In the optical time-of-flight measuring device according to any one of claims 1 to 20,
An optical time-of-flight measurement apparatus comprising a delay measurement unit (4) that calculates delay correction information based on a delay time from the pixel to the time measurement unit. The optical time-of-flight measuring device according to claim 21,
The optical time-of-flight measurement apparatus, wherein the delay measurement unit calculates the delay correction information based on a delay time from the pixel to the time measurement unit and a delay time of the delay measurement signal. The optical time-of-flight measuring device according to claim 21 or 22,
When the delay measurement instruction signal is input, the delay measurement unit outputs the delay measurement start signal to the light receiving unit and the time measurement unit. The optical time-of-flight measurement device according to any one of claims 20 to 23,
The delay time until the delay measurement start signal is output from the delay measurement unit and input to the delay measurement circuit, and the delay measurement feedback signal is output from the delay measurement feedback circuit and input to the time measurement unit. An optical time-of-flight measuring apparatus, which is designed so that a time difference from a delay time until a predetermined time is less than or equal to a predetermined value. In the optical time-of-flight measuring device according to any one of claims 20 to 24,
The delay time from when the delay measurement start signal is output from the delay measurement unit to the time measurement unit is input, and the delay measurement start signal is output from the delay measurement unit and input to the delay measurement circuit. Delay time until the delay measurement feedback signal is output from the delay measurement feedback circuit and input to the time measurement unit, the delay time is designed to be equal to or shorter than at least one of the delay times. An optical time-of-flight measuring device. In the optical time-of-flight measuring device according to any one of claims 20 to 25,
The optical time-of-flight measuring apparatus, wherein the light receiving unit, the time measuring unit, and the delay measuring unit are formed on the same chip. An optical time-of-flight measuring device according to any one of claims 1 to 26;
When a ranging start signal is input, a light emitting unit (6) that emits irradiation light;
A distance measuring unit (3) for calculating distance information based on the optical flight time;
A control unit (2) for measuring distance,
The time measurement unit measures the optical flight time based on a time difference from a timing at which the ranging start signal is input to a timing at which the light reception signal is input,
The control unit performs distance measurement based on the distance information and the delay correction information. The optical distance measuring device according to claim 27.
The optical distance measuring device, wherein the control unit performs delay measurement in a period in which emission of irradiation light from the light emitting unit is suspended.

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