LIGHT DETECTION DEVICE, LIGHT DETECTION METHOD AND OPTICAL DISTANCE SENSOR

Abstract

A light detection device for detecting incident light according to a detection start time, the light detection device comprising: a plurality of photosensors configured to receive light to generate output signals, each indicating the results of the light detection; a signal combination circuit configured to sum the plurality of output signals from the respective photosensors to generate a combined signal; a detection circuit configured to detect a time at which the combined signal is maximized after the detection start time, in order to generate a detection signal indicating the detected time as a time at which the combined signal is maximized;and at least one timing circuit configured to measure a counting period between the detection start time and the detected time as the time at which the combined signal is maximized, based on the detection signal.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a light detection device, a light detection method and an optical distance sensor including the light detection device. TECHNICAL BACKGROUND

[0002] An optical distance sensor is known that utilizes the time-of-flight (TOF) of light. The optical distance sensor illuminates an object with light and detects the light reflected from the object, thereby measuring a distance corresponding to the time it takes for the light to travel back and forth to the object. A technique is proposed for the optical distance sensor that uses a single-photon avalanche photodiode (SPAD) for light detection (e.g., patent documents 1 and 2).

[0003] Patent document 1 discloses a distance measuring device with several SPADs in a receiver unit. The distance measuring device of patent document 1 determines that a measuring pulse is detected when a sum signal, which indicates the sum of the electrical pulses emitted by the several SPADs, exceeds a predetermined threshold value and a rising edge of the sum signal exceeds a predetermined edge threshold value.

[0004] Patent document 2 discloses a light detector with multiple SPADs in an optical distance measuring device. The light detector of patent document 2 sums rectangular pulses emitted by the plurality of SPADs, compares a summed output value with a predetermined reference value, and outputs a trigger signal according to the comparison result. CITATION LIST Patent document Patent document 1: US 2015 / 0177369 A1 Patent Document 2: JP 5644294 B SUMMARY Technical Problem

[0005] The SPAD also responds to only a single photon, but the response is stochastic. Therefore, the rise of the summed signal is steeper when the number of received photons increases and gentler when the number of received photons decreases. Accordingly, the distance measuring device of patent document 1 et al. cannot detect light with a small number of photons at a higher slope threshold and falsely detects stray light at a lower slope threshold. Therefore, it is difficult to accurately perform light detection in the optical distance sensor in the relevant field.

[0006] One objective of the present disclosure is to provide a light detection device, a light detection method and an optical distance sensor that are capable of performing accurate light detection in an optical distance sensor. Solution to the problem

[0007] A light detection device according to the present disclosure detects incident light after a detection start time. The light detection device comprises a plurality of photosensors, a signal combining circuit, a detection circuit, and at least one timing circuit. The plurality of photosensors receive light to generate output signals, each indicating the results of the light reception. The signal combining circuit sums a plurality of output signals from the respective photosensors to generate a combined signal. The detection circuit detects a time at which the combined signal is maximized after the detection start time to generate a detection signal indicating the detected time. The timing circuit measures a counting period between the detection start time and the detected time based on the detection signal.

[0008] A light detection method according to the present disclosure provides a method in which a light detection device detects incident light according to a detection start time.

[0009] An optical distance sensor according to the present disclosure comprises a light projector that projects light and a light detection device. The timing circuit in the light detection device measures the counting period using a time at which the light projector projects light as the detection start time. Beneficial effect

[0010] According to the present disclosure, it is possible to accurately perform light detection in the optical distance sensor using the light detection device, the light detection method and the optical distance sensor. List of characters Fig. Figure 1 is a view describing an application example for a light detection device according to the present disclosure. Fig. Figure 2 is a block diagram illustrating a configuration of an optical distance sensor according to a first embodiment. Fig. Figure 3 is a block diagram illustrating a configuration of a light detection device according to the first embodiment. Fig. Figure 4 is a circuit diagram showing a configuration example for a maximum value hold circuit in the light detection device. Fig. 5A to Fig. 5D are timing diagrams used to describe a method for combining a combined signal in the light detection device. Fig. 6A to Fig. Figure 6D are timing diagrams illustrating the operation of the light detection device according to the first embodiment. Fig. Figure 7 is a block diagram illustrating a configuration of a light detection device according to a second embodiment. Fig. 8A to Fig. Figure 8D are timing diagrams illustrating the operation of the light detection device according to the second embodiment. Fig. Figure 9 is a block diagram illustrating a configuration of a light detection device according to a third embodiment. Fig. 10A to Fig. Figure 10D are timing diagrams illustrating the operation of the light detection device according to the third embodiment. Fig. Figure 11 is a circuit diagram illustrating a modification of a detection circuit in the light detection device. DETAILED DESCRIPTION

[0011] Exemplary embodiments of a light detection device, a light detection method, and an optical distance sensor according to the present disclosure are described below with reference to the accompanying drawings. It should be noted that the same components are designated by the same reference numerals in each of the following exemplary embodiments. (Application example)

[0012] An example to which a light detection device according to the present disclosure can be applied is given with reference to Fig. 1 described. Fig. Figure 1 is a view describing an application example for a light detection device. 1 according to the present disclosure.

[0013] The light detection device 1 According to the present disclosure, an optical distance sensor is used. 2 of the TOF type. The optical distance sensor 2contains a light projector or light emitter 20 , which projects pulsed light outwards, as is the case, for example, in Fig. Figure 1 shows the light detection device. 1 represents a receiver unit that is integrated into the optical distance sensor 2 It receives light from outside.

[0014] The optical distance sensor 2 According to the present disclosure, it can, for example, be based on a photoelectric sensor for applications in industrial automation. The optical distance sensor 2 detects reflected light from the pulsed light emitted by the light projector 20 is projected using the light detection device 1 to measure the distance to an object that reflects light based on the light's travel time. The optical distance sensor 2 It can detect whether the object is located in a specific position.

[0015] In the present application example, the sensitivity of light detection or similar is improved in the optical distance sensor. 2 A SPAD is used as a sensor element, i.e., a photosensor in the light detection device. 1 The SPAD is highly sensitive enough to react to the incident photon. This also makes the SPAD sensitive to ambient light. In the present application example, the signal processing of the SPAD's output signal in the light detection device... 1 a highly accurate and robust light detection system against stray light is implemented, and the accuracy of the distance measurement of the optical distance sensor is improved. 2 improved. (Configuration example)

[0016] The following are configuration examples of the light detection device. 1 and the optical distance sensor 2 described. (First embodiment)

[0017] In the first embodiment, the light detection device 1 and the optical distance sensor 2 described, which detect a point in time at which the number of SPADs that have detected photons reaches a maximum. configuration

[0018] The following describes the configurations of the optical distance sensor. 2 and the light detection device 1 as described in the first embodiment. 1-1. Configuration of the optical distance sensor

[0019] The configuration of the optical distance sensor 2 According to the present embodiment, with reference to Fig. 2 described. Fig. Figure 2 is a block diagram showing the configuration of the optical distance sensor. 2 illustrated.

[0020] The optical distance sensor 2 This includes, for example, the light projector. 20, a controller 25 and the light detection device 1 , as in Fig. 2 shown. The light projector 20 contains, for example, a light source 21 and a light source driver 22 .

[0021] In the light projector 20 the light source 21 For example, an LD (laser diode) or an LED. The light source 21 It emits light, such as visible light and near-infrared light. The light source driver 22 is a circuit that controls the light emission of the light source 21 controls. The light source driver 22 causes the light source to 21 Light in the form of a pulse, i.e., pulsed light, to a control 25 or the controller 25 emits pulses at controlled intervals. The pulsed light has a pulse width of, for example, a few nanoseconds up to several tens of nanoseconds.

[0022] The controller25 It includes, for example, a CPU, RAM, ROM, and similar components, and controls each one. For example, the controller generates 25 various control signals to control the entire operation of the optical distance sensor 2 to control.

[0023] As in Fig. The light detection device shown in Figure 2 includes... 1 e.g. a SPAD array 10 , a signal processor 11 and a distance meter 12 The light detection device 1 This includes, for example, an amplifier that amplifies an electrical signal generated by the SPAD in response to incident light, a driver circuit for the SPAD, and similar components in the SPAD arrangement. 10 or the signal processor 11 .

[0024] The SPAD array 10 It is configured by arranging a large number of SPADs in an array form. Each SPAD in the SPAD array 10is implemented by operating an avalanche photodiode (APD) in Geiger mode.

[0025] The signal processor 11 performs signal processing to generate a result based on the output signal of the SPAD array. 10 to determine a time at which light is present as the detection target of the light detection device 1 arrives. The distance measuring device 12 calculated based on a signal processing result from the signal processor 11 A distance value that indicates a distance corresponding to the time of flight of light. Details of the light detection device configuration. 1 are described below. 1-2. Configuration of the light detection device

[0026] A configuration example of the light detection device 1 According to the first embodiment, with reference to Fig. 3 described. Fig. 3 is a block diagram showing the configuration of the light curtains 1 as shown in the present version.

[0027] As in Fig. Figure 3 shows the light detection device. 1 The present version contains a large number of SPADs. 10a until 10c , which the SPAD array 10 form, as well as a signal combination circuit 13 and a detection circuit 3 , which includes a signal processor 11 form. In addition, the light detection device contains 1 for example a TDC (time-to-digital converter) 4 and a computer 5 , which the distance measuring device 12 form.

[0028] The SPADs 10a until 10c are examples of photosensors that respond stochastically to photons entering the light detection device 1 The following is an example where the number of SPADs10a until 10c in the SPAD arrangement 10 three.

[0029] Each of the SPADs 10a , 10b and 10c receives light and generates the output signals. Sa , Sb and Sc , each indicating a result of the light reception. For example, a waveform shaping circuit that shapes the signal waveforms of the output signals. Sa until Sc the SPADs 10a until 10c forms rectangular pulse shapes, in a suitable manner into the light detection device 1 integrated. The respective output signals Sa until Sc the SPAD matrix 10 are integrated into the signal combination circuit 13 of the signal processor 11 entered.

[0030] The signal combination circuit 13 sums the multitude of output signals Sa until Sc , which are entered into them to create a combined signal S1to generate. The signal combination circuit 13 The combined signal thus generated gives S1 to the detection circuit 3 off. The signal combination circuit 13 can be configured by applying a known technique (see e.g. patent document 2).

[0031] Based on the combined signal S1 from the signal combination circuit 13 The detection circuit recognizes 3 the time of the light that serves as the detection target of the light detection device 1 is obtained to generate a detection signal S2 to generate a signal that indicates a detection result. In the present embodiment, the detection circuit contains 3 a maximum value hold circuit 6 , a delay circuit 31 and a comparison circuit 32 , as in Fig. 3 shown.

[0032] The maximum value hold circuit 6maintains the maximum values ​​of the combined input signal S1 one after the other, to obtain a maximum value signal S10 to generate the maximum value signal. S10 shows a preliminary maximum value of the combined input signal S1 in the present embodiment, the maximum value hold circuit indicates 6 the maximum value signal S10 to the delay circuit 31 and the comparison circuit 32 An example configuration for the maximum value hold circuit. 6 will be described later.

[0033] The delay circuit 31 In the present embodiment, the maximum value signal is delayed. S10 to a predetermined delay period, to a delay signal S11 to generate. The delay circuit 31 gives the delay signal S11 to the comparison circuit 32 out of.

[0034] The comparison circuit32 performs the determination by using the maximum value signal S10 with the delay signal S11 compares and, according to a determination result, the recognition signal S2 generated. The comparison circuit 32 In the present embodiment, the detection signal is generated S2 as a result of determining whether the maximum value signal S10 greater than the delay signal S11 is or isn't.

[0035] The detection signal S2 from the detection circuit 3 will be in the TDC 4 a signal is fed in. Additionally, a detection start clock signal is supplied. S0 from the controller 25 in the TDC 4 fed in. The detection start clock signal. S0 is an example of a control signal that determines the start time of the TDC's time measurement 4 displays.

[0036] The TDC 4This is an example of a timing circuit that generates time information as a digital value (time-to-digital conversion) for time measurement purposes. The TDC 4 measures a counting period that is determined by the detection start clock signal S0 displayed time until the detection signal S2 The displayed time is sufficient, based on the detection start clock signal. S0 and the detection signal S2 , and generates a time information D1 , which displays the counting period as a measurement result.

[0037] The computer 5 It contains, for example, a CPU that, in conjunction with software, performs various arithmetic processes, RAM, ROM, and similar components. The computer 5 works as a distance measuring device 12 together with the TDC 4 Specifically, the computer records 5 from TDC 4 the time information D1, which specifies the measured counting period, and performs a process to calculate a distance depending on the light travel time.

[0038] It should be noted that hardware resources, such as the CPU, which power the computer 5 forms, from the controller 25 of the optical distance sensor 2 can be shared or provided separately. Furthermore, the computer 5 , the controller 25 and the like can be configured through various hardware circuits, such as an ASIC and an FPGA. 1-2-1. Maximum value hold circuit

[0039] A configuration example of the maximum value hold circuit 6 in the light detection device 1 will be with reference to Fig. 4 described. Fig. Figure 4 is a circuit diagram showing a configuration example of the maximum value hold circuit. 6 illustrated.

[0040] As in Fig. As shown in section 4, the maximum value hold circuit includes 6 e.g. a comparator 61 and two multiplexers 60 and 62 The maximum value hold circuit 6 maintains the maximum value of the combined input signal S1 and gives the sustained maximum value signal S10 out of.

[0041] The combined signal S1 from the signal combination circuit 13 is entered into the comparator 61 and the multiplexer 62 in the maximum value hold circuit 6 entered. The multiplexer 60 gives an initial value signal Si of the maximum value or the maximum value signal S10 to the comparator 61 and the multiplexer 62 out of.

[0042] The comparator 61 compares the combined signal S1 with the initial value signal Si or the maximum value signal S10 , that from the multiplexer 60is output. The comparator 61 sends a signal indicating a comparison result to a control port of the multiplexer. 62 out of.

[0043] The multiplexer 62 switches on at an input port of the multiplexer 60 signal to be output between the combined signal S1 and the initial value signal Si or the maximum value signal S10 , that from the multiplexer 60 The output is determined according to the comparison result of the comparator. 61 um.

[0044] The multiplexer 60 initializes the maximum value signal S10 e.g. corresponding to a reset signal Sr input from the controller 25 ( Fig. 2).

[0045] According to the maximum value hold circuit 6 In the configuration example above, the maximum value signal can be S10 be updated each time the maximum value in the combined signal is reached. S1will be updated. Operation

[0046] How the optical distance sensor works 2 and the light detection device configured as described above 1 will be described below.

[0047] In the optical distance sensor 2 The controller controls 25 ( Fig. 2) the light source driver 22 of the light projector 20 so that the light source 21 For example, it emits pulsed light at predetermined time intervals. If the projected pulsed light is reflected by an object that serves as a distance measurement target for the optical distance sensor. 2 If so, the projected pulsed light can be reflected as light onto the optical distance sensor. 2 hit.

[0048] At the time of controlling the light projector 20 The controller generates 25 the detection start clock signal S0, which indicates the time for the light projection, and gives the detection start clock signal S0 to the TDC 4 ( Fig. ) of the rangefinder 12 out of.

[0049] In synchronization with the light projection or light emission of the light projector 20 The light detection device 1 in the optical distance sensor 2 A light detection system is used to detect the reflected light of the pulsed light during a predetermined light reception period from the moment of light projection. The light reception period is set to a period shorter than, for example, the time interval of the pulsed light, and can be adjusted with respect to the light travel time according to an upper limit of the distance to be measured (e.g., a light reception period of 200 ns for a distance limit of 30 m). For example, the controller can 25Immediately before the light projection or similar, the reset signal Sr is sent to the maximum value hold circuit. 6 output to set a maximum value as the initial value (see Fig. 4).

[0050] During light detection of the light detection device 1 receives the SPAD array 10 Light, and the signal processor 11 performs signal processing on a signal resulting from light reception and thereby generates the recognition signal. S2 , which indicates the time at which the reflected light arrives. Based on the detection signal S2 The distance measuring device measures 12 the transit time, the time until the projected pulsed light is reflected by the object and received by the TDC 4 passes, as a counting period. The distance meter 12can calculate a distance value by, for example, multiplying half of the measured counting period by the speed of light.

[0051] By using SPADs 10a until 10c in the light detection device 1 in the optical distance sensor above 2 It is possible to increase the sensitivity of light detection and improve the accuracy of distance measurement. Since the SPADs 10a until 10c However, since both are highly sensitive and react to background light, an influence on the noise caused by the background light is conceivable. Here, the reflected light of the pulsed light is simultaneously received as a detection target. It is therefore to be expected that the number of photons at this point in time is greater than the number of photons from the background light alone at other times.

[0052] Therefore, the light detection device recognizes 1The present version specifies the time at which the combined signal S1 the output signals Sa until Sc from the SPADs 10a until 10c A maximum is reached, and the detected time is used as the time at which the reflected light arrives. The following describes the operation of the light detection device. 1 The present embodiment is described in detail. 2-1. Operation of the light detection device

[0053] Details of how the light detection device works 1 According to the present embodiment, with reference to Fig. 5 and Fig. 6 described.

[0054] Fig. 5A to Fig. 5D diagrams are time diagrams used to describe a method for combining the combined signal. S1 in the light detection device 1 . Fig. 6A to Fig. 6D are timing diagrams that describe the operation of the light detection device. 1 illustrate.

[0055] In the light detection device 1 ( Fig. 3) of the present embodiment, the SPADs receive 10a until 10c Light is used in the respective stochastic operations and generates the output signals. Sa , Sb or Sc The signal waveforms of the output signals Sa , Sb and Sc are in Fig. 5A, Fig. 5B or Fig. 5C is shown.

[0056] In the example of Fig. 5A to Fig. 5C is each of the output signals Sa until Sc a rectangular pulse P1 with a predefined pulse width. Each of the SPADs 10a until 10c reacts stochastically to incident photons, so that the rectangular momentum P1 in each of the output signals Sa until Sc is generated.

[0057] In the example of Fig. 5A to Fig. The output signal increases at 5C Sa the first SPAD 10a at the time t1 on ( Fig. 5A) and the output signal Sb of the second SPAD 10b rises at that time t3 after the time t1 on ( Fig. 5B). Furthermore, the output signal increases Sa the third SPAD 10a at the time t2 between the time t1 and the time t3 on ( Fig. 5C).

[0058] The signal combination circuit 13 sums the output signals Sa until Sc from the SPADs 10a until 10c , to combine the signal S1 to generate the combined signal. S1 based on the output signals Sa until Sc in Fig. 5A to Fig. 5C and is in Fig. Illustrated in 5D.

[0059] The in Fig. 5D represented combined signal S1 is the sum of the three output signals Sa until Sc ( Fig. 5A to Fig. 5C) at the same time. For example, the sum of the combined signal corresponds to S1 the output signal Sa out of Fig. 5A from the time t1 until the time t2 .

[0060] Additionally, the combined signal increases. S1 in the example of Fig. 5D at the time t2 from "1" to "2" by the sum of the two rectangular pulses P1 ( Fig. 5A and Fig. 5C). The combined signal S1 increases further from "1" to "3" at the time t3 by the sum of the three rectangular pulses P1 ( Fig. 5A to Fig. 5C). In this way, one signal level of the combined signal changes. S1 according to the number of SPADs 10a until 10cwith the received light. A time graph of the combined signal. S1 , if the SPADs 10a until 10c are affected by stray light, is in Fig. 6A is shown.

[0061] The combined signal S1 in the example of Fig. 6A contains a peak P10 a reflected light component as a detection target and two peaks P11 and P12 of interference light components. The peak P10 The reflected light component is larger than the peaks P11 and P12 each interference light component and appears at a time between the two peaks. P11 and P12 .

[0062] The following is an example where the light projector 20 Light at the time t10 projected and the light detection device 1 light detection during a light reception period T1 from that point on t10carries out as in Fig. 6A to Fig. Illustrated in 6D.

[0063] In the detection circuit 3 ( Fig. 3) The maximum value hold circuit 6 the maximum value of the combined signal S1 based on the combined signal S1 from the signal combination circuit 13 and generates the maximum value signal S10 The combined signal S1 in the example of Fig. 6A-based maximum value signal S10 is in Fig. 6B is shown.

[0064] The in Fig. Maximum value signal shown in 6B S10 is increased each time the maximum value is reached after the time t10 in the combined signal S1 from Fig. 6A at the times t11 , t12 and t13 is updated one after the other.

[0065] For example, the combined signal S1 from Fig. 6A after the time t12 from, since there is a peak P11 what happened, but the maximum value signal S10 maintains a signal level of the peak P11 , as in Fig. 6B is shown. Since the combined signal S1 at the time t13 the maximum level P10 The peak signal is reached and held. S10 after the time t13 a signal level of the same level P10 .

[0066] For example, if the peak signal S10 out of Fig. When 6B is entered, the delay circuit is activated. 31 the delay signal S11 , as in Fig. 6C is shown. The delay signal S11 of the present embodiment is in contrast to the maximum value signal S10 to allow for a delay period T2 delayed.

[0067] The comparison circuit 32 leads to the above comparison and the determination between the maximum value signal S10and the delay signal S11 through to the recognition signal S2 to generate the detection signal. S2 based on the maximum value signal S10 out of Fig. 6B and the delay signal S11 out of Fig. 6C is in Fig. Illustrated in 6D.

[0068] After the comparison and determination of the comparison circuit 32 In the present embodiment, the detection signal is formed S2 a rectangular pulse P2 (hereinafter referred to as the "detection pulse"), when the maximum value signal S10 and the delay signal S11 do not agree, as in Fig. 6B to Fig. 6D representation. In the example of Fig. 6. Three rectangular pulses rise P2 at those times t11 , t12 and t13 in the present embodiment, each of the recognition pulses P2a pulse width corresponding to the delay period T2 the delay circuit 31 corresponds to the detection signal. S2 will be in the TDC 4 entered or supplied.

[0069] Based on the detection start time signal S0 from the controller 25 and each of the detection pulses P2 of the detection signal S2 The TDC measures (i.e., performs a time / digital conversion). 4 a period from the time t10 , which is determined by the detection start time signal S0 displayed until any time t11 , t12 and t13 , in which each of the detection pulses P2 increases sequentially. For example, the TDC holds 4 The new measurement result is only recorded when the period measurement is repeated. In this case, the TDC measures 4 most recently a period T3 from time t10 up to the present time t13and contains information that covers the period T3 Specify as the counting period, in the example of Fig. 6D.

[0070] The computer 5 receives the time information D1 , which the counting period T3 indicates, from the TDC 4 e.g. after the light reception period has ended T1 As a distance measuring device 12 The calculator calculates 5 the distance value by performing an operation such as multiplying the counting period T3 performs the operation with a given coefficient.

[0071] According to the above operating principle of the light detection device 1 The detection circuit recognizes 3 the time t13 , where the combined signal S1 based on the combined signal S1 , which is achieved by summing the output signals Sa until Sc the SPADs 10a until 10cThe value obtained is maximized. Consequently, even if the peaks are not reached, it is still possible to maximize the value obtained. P11 and P12 of the interference light components before and after the peak P10 The reflected light component is present as a detection target, making it possible to determine the time (time point). t13 ) as a detection target. This makes it possible to measure the counting period. T3 through the TDC 4 to be carried out precisely. Summary

[0072] As described above, the light detection device detects 1 According to the present embodiment, incident light corresponds to the time (light projection time) determined by the detection start time signal. S0 is displayed. The light detection device 1 encompasses the multitude of SPADs 10a until 10c , the signal combination circuit 13 , the detection circuit 3 and the TDC 4 Each of the SPADs10a until 10c receives light and generates each of the output signals. Sa until Sc , which display the results of the light reception. The signal combination circuit 13 sums the multitude of output signals Sa until Sc from the SPADs 10a until 10c , to combine the signal S1 to generate. The detection circuit 3 detects the time at which the combined signal S1 is maximized after the light projection time to increase the detection signal S2 to generate a time that indicates the detected time. The TDC 4 measures the counting period T3 , which represents a period between the time of light projection and the time on the detection signal S2 based on the detected time.

[0073] According to the aforementioned light detection device 1 is it by recording the time at which the number of SPADs10a until 10c , which simultaneously received light, is maximized, making it possible to detect the light of the detection target, such as the reflected light of the pulsed light from the light projector. 20 , even in a situation affected by stray light, to carry out the procedure accurately.

[0074] In the present embodiment, the photosensors of the light detection device 1 the SPADs 10a until 10c , which react stochastically to the incident photons. Even if each of the SPADs 10a until 10c reacting to the interfering light, it is possible to use the maximum value of the combined signal for light detection. S1 to be carried out precisely.

[0075] In the present embodiment, the detection circuit includes 3 the maximum value hold circuit 6 , which is the maximum value signal S10generated that maintains the maximum value, which is updated each time the combined signal S1 The maximum value is updated. S10 the maximum value hold circuit 6 Is it possible to identify the point in time at which the maximum value in the combined signal occurs? S1 will be updated.

[0076] In the present embodiment, the detection circuit comprises 3 furthermore, the delay circuit 31 and the comparison circuit 32 The delay circuit 31 delays the maximum value signal S10 to the specified delay period T2 , to the delay signal S11 to generate. The comparison circuit 32 compares the maximum value signal S10 and the delay signal S11 together to obtain the detection signal S2 to output in order to indicate the time at which the maximum value signalS10 the delay signal S11 exceeds. With the simple circuit configuration of the detection circuit 3 As described above, it is possible to determine the maximum value time in the combined signal. S1 to detect.

[0077] Furthermore, the optical distance sensor includes 2 according to the present embodiment, the light projector 20 , which projects or emits light, and the light detection device 1 The TDC 4 the light detection device 1 measures the counting period T3 using the time at which the light projector 20 Light is projected to indicate the start of detection. This is done using an optical distance sensor. 2 With the present design, it is possible to perform light detection in the light detection device. 1 to carry out the measurement accurately and to improve the accuracy of the distance measurement.

[0078] Furthermore, the light detection method according to the present embodiment is a method in which the light detection device 1 Incident light is detected according to the detection start time. The present method comprises: Receiving light with a multitude of SPADs. 10a until 10c , to process each of the output signals Sa until Sc to generate signals that indicate the result of light reception; and summing the multitude of output signals. Sa until Sc , to combine the signal S1 to generate. Furthermore, the present method comprises: recording the time at which the combined signal S1 is maximized after the start of the acquisition time to maximize the acquisition signal S2 to generate a time that indicates the recorded time; and to measure the counting period. T3 between the detection start time and the recorded time based on the detection signalS2 . According to the present method, it is possible to carry out precise light detection.

[0079] The above description described the example in which the number of SAPDs 10a until 10c , which are in the light detection device 1 The number of SAPDs is three. 10a until 10c , which are in the light detection device 1 The number included can be four or more, or two. (Second example)

[0080] In the first embodiment, the light detection device 1 described, which the delay signal S11 of the maximum value signal S10 used to determine the time at which the combined signal S1 is maximized. In a second embodiment, a light detection device is used, which provides a delay signal of the combined signal. S1used, with reference to Fig. 7 and Fig. 8 described.

[0081] Fig. Figure 7 is a block diagram showing a configuration of a light detection device. 1A as illustrated in the second embodiment. The light detection device 1A According to the present explanation, changing the configuration of a detection circuit 3A , as in Fig. Figure 7 shows a configuration similar to that of the light detection device. 1 ( Fig. 3) of the first version.

[0082] As in Fig. The detection circuit shown in figure 7 indicates 3A The combined signal in the present version S1 into a delay circuit 31A one, to combine the signal S1 to delay. The delay circuit 31A generates a delay signal S11A of the combined signal S1and gives the delay signal S11A to a comparison circuit 32A out. The comparison circuit 32A The present version compares the delay signal S11A with the maximum value signal S10 and generates as a result of determining whether the delay signal S11A equal to or greater than the maximum value signal S10 is or is not a detection signal S2A .

[0083] Fig. 8A to Fig. 8D are timing diagrams that describe the operation of the light detection device. 1A Illustrate according to the second embodiment. Fig. 8A is an example of a time diagram of the combined signal. S1 . Fig. 8B illustrates the maximum value signal S10 based on the combined signal S1 from Fig. 8A. Fig. Figure 8C illustrates the delay signal S11A based on the combined signalS1 out of Fig. 8A. Fig. Figure 8D illustrates the detection signal S2A based on the peak signal S10 from Fig. 8B and the delay signal S11A from Fig. 8C.

[0084] In the example of Fig. 8A to Fig. 8D will be the maximum value of the combined signal. S1 at those times t21 and t22 after the time t10 the detection start time is continuously updated ( Fig. 8A and Fig. 8B). As in Fig. As shown in 8C, the delay signal S11A The present embodiment exhibits a delay that corresponds to a delay period. T2A compared to the combined signal S1 corresponds (e.g. T2A (several nanoseconds to several tens of nanoseconds).

[0085] In the light detection device 1Aaccording to the present embodiment, based on the comparison and determination of the comparison circuit described above 32A , increases in the recognition signal S2A a recognition impulse P2A on, as in Fig. 8D displayed when the delay signal S11A with the maximum value signal S10 This is consistent. Furthermore, the pulse width of the detection pulse changes. P2A of the present embodiment corresponding to a period in which the delay signal S11A with the maximum value signal S10 agrees.

[0086] As in the first embodiment, the TDC uses 4 To measure the period, the rise time of the detection pulse is used. P2A in the detection signal S2A For example, the TDC measures 4 the counting period T3 from time t10 up to the present time t23 , where the last detection pulse P2A increases. Time t23 will be adjusted to account for the delay period T2A from that point on t22 delayed, in which the combined signal S1 the maximum peak P10 achieved. In the distance meter 12 In the present embodiment, the computer corrects 5 etc. the counting period T3 , which are due to the time information D1 from the TDC 4 displayed to indicate the delay period T2A , to calculate a distance value based on the calculation of a runtime T4 based on light.

[0087] According to the light detection device 1A In the present embodiment, for example, the combined signal increases sharply. S1 as at those times t21 and t22 in the examples of Fig. 8A to Fig. 8D the detection pulse P2A at a point in time (time) t23after the delay period has expired T2A ), which at that time t22 corresponds to the point at which the signal reaches a higher signal level, as in Fig. 8D representation. In this way, the accuracy of the detection of the maximum time by the light detection device can be verified. 1A can be improved.

[0088] As described above, the delay circuit delays 31A the detection circuit 3A in the light detection device 1A according to the present embodiment, the combined signal S1 about the predetermined delay period T2A , to the delay signal S11A to generate. The comparison circuit 32A compares the maximum value signal S10 and the delay signal S11A together to obtain the detection signal S2A to output in order to indicate the time at which the delay signal S11A the maximum value signal S10achieved. The light detection device described above. 1A It also enables highly accurate light detection with robustness against stray light. (Third embodiment)

[0089] Regarding light detection devices 1 and 1A In the first and second embodiments, the time at which the combined signal S1 a maximum is reached and used for distance measurement. In a third embodiment, a light detection device that uses a multitude of time points from the upper range or upper values ​​of the light detection for distance measurement is used with reference to Fig. 9 and Fig. 10 described.

[0090] Fig. Figure 9 is a block diagram showing a configuration of a light detection device. 1B as illustrated in the third embodiment. The light detection device 1BAccording to the present embodiment, a plurality of TDCs comprises 4A and 4B , as in Fig. 9 shown, in a configuration that is, for example, the configuration of the light detection device 1A is similar to the second embodiment (see Fig. 7) Furthermore, the light detection device contains 1B The present version includes a selection circuit 7 , which is one of the many TDCs 4A and 4B selects.

[0091] The following is a configuration example where the number of TDCs is... 4A until 4B in the light detection device 1B two. Each of the TDCs 4A and 4B is configured similarly to the TDC 4 of the first and second embodiments. The TDCs 4A and 4B Each contains the time information D11 and D12, each indicating a counting period.

[0092] As in Fig. The selection circuit shown in 9 contains the selection circuit 7 e.g. a counter 70 and a multiplexer 71 The selection circuit 7 It then selects a TDC to measure a period from the multitude of TDCs. 4A and 4B for each detection pulse P2A of the detection signal S2A out of.

[0093] The counter 70 counts the number of detection pulses P2A in the recognition signal S2A For example, the counter 70 in the configuration example of the two TDCs 4A and 4B A 1-bit counter. The counter 70 The counting result is a signal, for example indicating "0" or "1", sent to a control unit of the multiplexer. 71 out of.

[0094] The multiplexer 71 switches the TDC to output the detection signal S2A selectively between the multiple TDCs 4A and 4B um, based on the signal from the counter 70 For example, the multiplexer selects 71 a TDC 4A in the event that the signal indicating the count result "0" is received by the counter 70 is entered, and selects the other TDC 4B in the event that the signal indicating the count result "1" is entered.

[0095] In the light detection device 1B The present embodiment contains a computer 5A for example a statistics processor 5a , which performs statistical processing based on time information D11 and D12 from the multitude of TDCs 4A and 4B executes the distance measurement using statistical processing. For example, the statistics processor calculates... 5a of the computer 5Aan average of the counting periods or the corresponding distances based on the time information D11 , D12 , which are the measurement results of the multitude of TDCs 4A and 4B indicates the one-time projection and reception of light.

[0096] Furthermore, the statistics processor can 5a to create a histogram by using the time information D11 and D12 The samples obtained by repeatedly projecting or emitting and receiving light in a RAM or similar device are accumulated and can, for example, calculate a distance value corresponding to a peak position in the histogram. The number of histogram samples can be increased by using the multitude of TDCs. 4A and 4B will be increased.

[0097] Fig. 10A to Fig. 10D are timing diagrams that describe the operation of the light detection device. 1B Illustrate according to the third embodiment. Fig. 10A is an example of a time diagram of the combined signal. S1 . Fig. 10B illustrates the maximum value signal S10 based on the combined signal S1 from Fig. 10A. Fig. Figure 10C illustrates the delay signal S11A based on the combined signal S1 out of Fig. 10A. Fig. Figure 10D illustrates the recognition signal S2A based on the peak signal S10 from Fig. 10B and the delay signal S11A from Fig. 10C.

[0098] In the example of Fig. 10A to Fig. 10D rises at these times t31 , t32 and t33 after time t10 The detection pulse serves as the detection start time. P2A in response to the update of the maximum value in the combined signal S1 sequentially ( Fig. 10D).

[0099] In the light detection device 1B The selection circuit of the present configuration example 7 the recognition impulses P2A at those times t31 , t32 and t33 alternating between the two TDCs 4A and 4B one. The result is time information. D11 and D12 the two TDC 4A and TDC 4B the counting periods T31 and T32 , which correspond to the two upper time points t32 and t33 correspond to the maximum.

[0100] According to the time information D11 and D12 At the two highest time points recorded for each light projection time as described above, the accuracy of the distance measurement by the optical distance sensor can be determined. 2 This can be improved by performing statistical processing in such a way that, for example, stochastic operations on SPADs are used. 10auntil 10c The resulting detection fluctuations are suppressed.

[0101] The above description described the configuration example in which the number of TDCs 4A and 4B The number is two. The light detection device 1B The present embodiment can contain three or more TDCs. In this case, for example, a counter that can count the number of TDCs is used for the selection circuit. 7 It is used to sequentially switch the TDC (Time Data Coordinate) used to perform the measurement. As a result, the accuracy of the distance measurement can be improved using three or more time information points.

[0102] As described above, the light detection device contains 1B According to the present embodiment, the statistics processor is also included. 5a The statistics processor 5a captures the time information D11 and D12, which have a predetermined number of counting periods T31 and T32 from the end among the counting periods, which were measured several times for a light projection time measurement, in order to statistically process the captured time information D11 and D12 to carry out this procedure. As a result, it is possible to determine the detection fluctuations in the SPADs. 10a until 10c to suppress and improve the detection accuracy of the light detection.

[0103] In the present embodiment, the light detection device comprises 1B the majority of TDCs 4A until 4B and the selection circuit 7 The selection circuit 7 It switches the TDCs on one after the other to measure the counting periods. T31 and T32 from the multitude of TDCs 4A until 4B to each one through the detection signal S2A displayed time. As a result, it is possible to determine the time information by the number of TDCs. 4A until 4B to capture the higher order of the number of detected photons. It should be noted that a circuit configuration for capturing the multitude of higher-order temporal information is not limited to this and that various circuit configurations can be used. (Other examples)

[0104] In the third embodiment, the configuration example of the light detection device was 1B with the multitude of TDCs in a configuration similar to that of the light detection device 1A The second embodiment is described. The light detection device of the present embodiment is not limited to this and can, for example, accommodate a plurality of TDCs in a configuration similar to that of the light detection device. 1exhibit the first embodiment.

[0105] Although the configuration example of the detection circuit 3 or 3A As illustrated in each of the above embodiments, the detection circuit of the light detection device is not limited to the above configuration example, and various circuit configurations can be used. A modification of the detection circuit is described with reference to Fig. 11 described.

[0106] The light detection device of the present embodiment can, for example, replace the detection circuit. 3 or 3A from one of the above-mentioned embodiments, a detection circuit 3B according to a Fig. The modification shown in section 11 is included. The detection circuit 3B the present modification contains a configuration similar to the maximum value hold circuit 6 from Fig. 4, a delay circuit 31B to delay the output of a multiplexer 62 for output to the other multiplexer 60 Then the output of the comparator 61 as a detection signal S2 Output. The pulse width of a detection pulse in the detection signal. S2 is caused by a delay period of the delay circuit 31B adjusted. Also with the light detection device described above, including the detection circuit. 3B The light detection of a detection target can be carried out exactly as in each of the embodiments described above.

[0107] Furthermore, the configuration example, in which the photosensors of the light detection devices 1 until 1B the SPADs 10a until 10care described in each of the above embodiments. In the present embodiment, the photosensor of the light detection device is not necessarily the SPAD.

[0108] Furthermore, the application example of the optical distance sensor was described above. 2 Applications in industrial automation are shown. The applications of the optical distance sensor. 2 and the light detection devices 1 until 1B The applications described in this disclosure are not limited and may include, for example, applications in vehicles. The optical distance sensor 2 It could be, for example, a LiDAR or a distance imaging sensor. (Attachment)

[0109] As described above, various embodiments of the present disclosure have been described, but the present disclosure is not limited to the above-mentioned content, and various modifications can be made within a range where the technical idea is essentially the same. Several aspects of the present disclosure are further described below.

[0110] A first aspect according to the present disclosure is a light detection device ( 1 ) for detecting incident light after a detection start time. The light detection device comprises a variety of photosensors ( 10a until 10c) , a signal combination circuit ( 13 ), a detection circuit ( 3 ) and at least one timing circuit ( 4 The multiple photosensors receive light to generate output signals ( Sa until Sc ) to generate signals that each indicate the results of the light reception. The signal combination circuit sums a multitude of output signals from the respective photosensors to produce a combined signal ( S1 ) to generate. The detection circuit detects a time at which the combined signal is maximized after the detection start time in order to generate a detection signal ( S2 ) to generate a signal indicating the detected time. The timing circuit measures one counting period ( T3 ) between the detection start time and the detected time based on the detection signal.

[0111] As a second aspect in the light detection device of the first aspect, the photosensor is a single-photon avalanche photodiode (SPAD) configured by an avalanche photodiode operating in Geiger mode.

[0112] As a third aspect, the detection circuit in the light detection device of the first or second aspect includes a maximum value hold circuit ( 6 ), which generates a maximum value signal that is updated every time the combined signal updates to a maximum value.

[0113] As a fourth aspect, the detection circuit in the light detection device, according to the third aspect, also includes a delay circuit ( 31 ) and a comparison circuit ( 32 The delay circuit delays the maximum value signal by a predetermined delay period to produce a delay signal ( S11 ) to generate. The comparison circuit compares the maximum value signal and the delay signal to output the detection signal, which indicates the time at which the maximum value signal exceeds the delay signal.

[0114] As a fifth aspect, the detection circuit includes ( 3A)in the light detection device ( 1A) The third aspect also includes a delay circuit ( 31A) and a comparison circuit ( 32A) The delay circuit delays the combined signal by a predetermined delay period to produce a delay signal ( S11A ) to generate. The comparison circuit compares a maximum value signal and the delay signal to generate a detection signal ( S2A ) to output a time at which the delay signal reaches the maximum value signal.

[0115] As a sixth aspect, the device includes light detection ( 1B) in addition to one of the first to fifth aspects, a statistics processor ( 5a)The statistics processor captures information specifying a last predetermined number of counting periods in multiple counting periods measured for a detection start time in order to perform statistical processing of the captured information.

[0116] As a seventh aspect, the light detection device of the sixth aspect comprises a multitude of timing circuits. The light detection device further comprises a selection circuit ( 7 ), which successively select the timing circuit for measuring the counting period among the multitude of timing circuits ( 4A and 4B) switches at each time indicated by the recognition signal.

[0117] An eighth aspect is an optical distance sensor ( 2 ) with a light projector ( 20The light projector, which projects light, and the light detection device according to one of the first to seventh aspects. The timing circuit in the light detection device measures the counting period using a time at which the light projector projects light as the detection start time.

[0118] A ninth aspect is a light detection method in which a light detection device ( 1 ), which contain a variety of photosensors ( 10a until 10c) The present method comprises: receiving light at the plurality of photosensors to generate each of the output signals ( Sa until Sc ) to generate the light reception results; summing the multitude of output signals ( Sa until Sc ) from the respective photosensors to produce a combined signal ( S1) to generate. The present method comprises: capturing a time point at which the combined signal is maximized after the acquisition start time in order to generate an acquisition signal ( S2 ) to generate a time that displays the recorded time; and measuring a counting period ( T3 ) between the start time of data collection and the time recorded, based on the data collection signal. Reference symbol list 1, 1A, 1B Light detection device 10a to 10c SPAD 13 Signal logic circuit 2 optical distance sensors 20 light projector 3.3A Detection circuit 31, 31A Delay circuit 32, 32A comparison circuit 4, 4A, 4B TDC 5.5A calculator 5a Statistics processor 6 Maximum value hold circuit 7 Selection circuit QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 2015 / 0177369 A1

[0004] JP 5644294 B

[0004]

Claims

[1] A light detection device for detecting incident light according to a detection start time, the light detection device comprising: a multitude of photosensors configured to receive light in order to generate output signals, each indicating the results of the light detection; a signal combination circuit configured to sum the multitude of output signals from the respective photosensors to produce a combined signal; a detection circuit configured to capture a time point at which the combined signal is maximized after the capture start time to generate a detection signal indicating the captured time; and at least one timing circuit configured to measure a counting period between the detection start time and the detected time based on the detection signal. [2] Light detection device according to claim 1, wherein the photosensors are single-photon avalanche photodiodes, each configured by an avalanche photodiode operated in Geiger mode. [3] Light detection device according to claim 1 or 2, wherein the detection circuit comprises a maximum value hold circuit configured to generate a maximum value signal that is updated each time the combined signal updates a maximum value. [4] Light detection device according to claim 3, wherein the detection circuit further comprises: a delay circuit configured to delay the maximum value signal by a predetermined delay period in order to generate a delay signal; and a comparison circuit configured to compare the maximum value signal and the delay signal to output the detection signal, which indicates a time when the maximum value signal exceeds the delay signal. [5] Light detection device according to claim 3, wherein the detection circuit further comprises: a delay circuit configured to delay the combined signal by a predetermined delay period to generate a delay signal; and a comparison circuit configured to compare the maximum value signal and the delay signal to output the detection signal, which indicates a time when the delay signal reaches the maximum value signal. [6] Light detection device according to any one of claims 1 to 5, comprising a statistics processor configured to acquire information indicating a last predetermined number of counting periods in multiple counting periods measured for a detection start time in order to perform statistical processing of the acquired information. [7] Light detection device according to claim 6, comprising a plurality of timing circuits, and further comprising a selection circuit configured to successively switch a timing circuit for measuring the counting period from the plurality of timing circuits at each time point indicated by the detection signal. [8] An optical distance sensor consisting of: a light projector that emits light; and the light detection device according to one of claims 1 to 7, wherein the timing circuit in the light detection device is configured to measure the counting period using a time point at which the light projector emits light as the detection start time. [9] Light detection method with a light detection device comprising a plurality of photosensors for detecting incident light according to a detection start time, the method comprising: Receiving light at the multitude of photosensors to each generate an output signal indicating the result of the light reception; and Summing the multitude of output signals from the respective photosensors to generate a combined signal; Detection of a point in time at which the combined signal is maximized after the detection start time to generate a detection signal that indicates the detected time; and the measurement of a counting period between the detection start time and the detection time based on the detection signal.