Optical sensor and distance measuring method

Abstract

The present invention provides a light sensor and a distance measurement method. The light sensor includes a light source, a sensing sub-pixel and a control circuit. The sensing sub-pixel includes a diode. The control circuit operates the diode in a Geiger mode or an avalanche linear mode. The control circuit includes a time-to-digital converter, and the time-to-digital converter includes a counting circuit. The counting circuit includes a plurality of counting units. When the time-to-digital converter receives a sensing signal provided by the sensing sub-pixel, the control circuit generates a plurality of counting values ​​according to the sensing signal through the plurality of counting units of the counting circuit, wherein the plurality of counting values ​​are histogram data corresponding to the distance sensing result. The light sensor and the distance measurement method of the present invention can provide a high-precision distance measurement result.

Description

Technical Field

[0001] The present invention relates to a sensing technology, and in particular to an optical sensor and a distance measurement method. Background Art

[0002] At present, high-sensitivity distance measuring sensors are in great demand in various application fields such as the medical field or the automotive field. In particular, light sensors that can be used to sense extremely weak light are one of the main sensor design directions at present. However, the distance measurement results of current distance measuring sensors are limited by the counting resolution (bin resolution, or grid resolution) of the digital converter 330, and cannot provide distance measurement results with higher accuracy. In view of this, how to effectively sense extremely weak light with high accuracy of light sensor, the following will propose several embodiments of the solution. Summary of the invention

[0003] The present invention is directed to an optical sensor and a distance measurement method, which can provide a high-precision distance measurement result.

[0004] According to an embodiment of the present invention, the optical sensor of the present invention includes a light source, a sensing sub-pixel and a control circuit. The sensing sub-pixel includes a diode. The control circuit is coupled to the light source and the sensing sub-pixel, and is used to operate the diode in a Geiger mode or an avalanche linear mode. The control circuit includes a time-to-digital converter. The time-to-digital converter includes a counting circuit. The time-to-digital converter is coupled to the diode. The counting circuit is coupled to the time-to-digital converter and includes a plurality of counting units. When the time-to-digital converter receives a sensing signal provided by the sensing sub-pixel, the control circuit generates a plurality of counting values ​​according to the sensing signal through a plurality of counting units of the counting circuit, wherein the plurality of counting values ​​are histogram data corresponding to the distance sensing result.

[0005] According to an embodiment of the present invention, the distance measurement method of the present invention includes the following steps: operating the diode of the sensing sub-pixel in Geiger mode or avalanche linear mode; emitting distance measurement light through a light source; sensing the reflected light corresponding to the distance measurement light through the sensing sub-pixel; and when the time-to-digital converter receives the sensing signal provided by the sensing sub-pixel, generating multiple counting values ​​according to the sensing signal through multiple counting units of the counting circuit, wherein the multiple counting values ​​are histogram data corresponding to the distance sensing result.

[0006] Based on the above, the optical sensor and the distance measurement method of the present invention can directly store the sensing data output by the time-to-digital converter as histogram data corresponding to the distance sensing result, so as to effectively save the storage space.

[0007] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic diagram of the structure of a light sensor according to an embodiment of the present invention;

[0009] Figure 2 is a schematic diagram of a sensor array according to an embodiment of the present invention;

[0010] Figure 3 is a circuit diagram of a sensing sub-pixel and a control circuit according to an embodiment of the present invention;

[0011] Figure 4 is a characteristic curve diagram of a diode according to an embodiment of the present invention;

[0012] Figure 5 is a flow chart of a distance measurement method according to an embodiment of the present invention;

[0013] Figure 6 is a circuit diagram of a time-to-digital converter according to an embodiment of the present invention;

[0014] Figure 7 is a signal timing diagram of a plurality of second switching signals and a sensing signal according to an embodiment of the present invention;

[0015] Figure 8 is a histogram of distance sensing results according to an embodiment of the present invention;

[0016] Fig. 9 is a circuit diagram of a time-to-digital converter according to another embodiment of the present invention;

[0017] Fig.10 is a signal timing diagram of a plurality of second switching signals and a sensing signal according to another embodiment of the present invention;

[0018] Fig.11 FIG. 4 is an operation timing diagram of a light sensor according to another embodiment of the present invention.

[0019] Description of Reference Numerals

[0020] 100: light sensor;

[0021] 110: control circuit;

[0022] 120: sensor array;

[0023] 121_1~121_N, 121_A, 121_B, 121_C, 121_D: sensing sub-pixels;

[0024] 122: sensor pixels;

[0025] 130: light source;

[0026] 310: diode;

[0027] 320: amplifier;

[0028] 330, 630: time to digital converter;

[0029] 331, 631, 931: counting circuit;

[0030] 401: characteristic curve;

[0031] 631_1~631_M, 931_1~931_M: counting unit;

[0032] 633: Controller;

[0033] 903: reference voltage;

[0034] SS: first switch;

[0035] S1_1~S1_M, S2_1~S2_a, S3_1~S2_b~SP_1~SP_2: second switch;

[0036] EN_1~EN_M, EN_1'~EN_M': switching signal;

[0037] S1, S2: single photon sensing signals;

[0038] SP1, SP2: pulse;

[0039] VOUT, 601, 901_1, 901_2: sensing signal;

[0040] VA, VOP, VBD, VEB, V, V_SPAD, V_APD: voltage;

[0041] Rq: cut-off resistance;

[0042] S510, S520, S530, S540: steps;

[0043] I: current;

[0044] M1~M4: voltage range;

[0045] ta~tg, t0~tM, t0'~t(M+4)', TA, TB: time;

[0046] P1~P4: sensing light signal;

[0047] T1~T4: exposure period;

[0048] EP1~EP4: exposure operation timing;

[0049] PH1~PH4: the emission timing of the sensing light;

[0050] Td: delay time. DETAILED DESCRIPTION

[0051] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0052] Figure 1 FIG. 4 is a schematic diagram of the structure of a light sensor according to an embodiment of the present invention. Figure 2 FIG. 1 is a schematic diagram of a sensor array according to an embodiment of the present invention. Figure 1 and Figure 2 , the light sensor 100 includes a control circuit 110, a sensor array 120 and a light source 130. The control circuit 110 is coupled to the sensor array 120 and the light source 130. The sensor array 120 includes a plurality of sensor sub-pixels 121_1 to 121_N, where N is a positive integer. Each of the sensor sub-pixels 121_1 to 121_N includes at least one diode (photodiode). The diode may be a pn junction diode. In the present embodiment, the control circuit 110 may control the sensor array 120 to operate the diodes in the sensor sub-pixels 121_1 to 121_N in a Geiger mode or an avalanche linear mode to perform a light sensing operation.

[0053] In this embodiment, the light source 130 may be an infrared laser light source, but the present invention is not limited thereto. In other embodiments of the present invention, the light source 130 may be a visible light source or an invisible light source. In this embodiment, the control circuit 110 may respectively operate the multiple diodes of the sensing sub-pixels 121_1 to 121_N in the single-photon avalanche diode (SPAD) state of the Geiger mode or the avalanche linear mode to measure the distance light (pulse light) emitted by the light source 130, thereby realizing a distance sensing function with low light quantity and high sensing sensitivity characteristics.

[0054] In this embodiment, the control circuit 110 may be, for example, an internal circuit or chip of the light sensor, and include digital circuit elements and / or analog circuit elements. The control circuit 110 may control the operation mode of the diodes in the sensing sub-pixels 121_1 to 121_N and / or the operation mode of the sensing sub-pixels 121_1 to 121_N by changing the bias voltage of the diodes in the sensing sub-pixels 121_1 to 121_N and / or the control voltage of multiple transistors. The control circuit 110 may control the light source 130 to emit ranging light, and may perform relevant signal processing and sensing data calculation on the sensing signals output by the sensing sub-pixels 121_1 to 121_N. In other embodiments of the present invention, the control circuit 110 may also be, for example, an external circuit or chip of the light sensor, such as a central processing unit (CPU), a microprocessor (MCU) or a field programmable gate array (FPGA) of a terminal device, or other such processing circuit or control circuit, but the present invention is not limited thereto.

[0055] Figure 3 FIG. 1 is a schematic diagram of a sensing sub-pixel and a control circuit according to an embodiment of the present invention. Figure 3 , Figure 3 A sensing sub-pixel is taken as an example, and the sensing sub-pixel and control circuit of this embodiment can be applied to a part of the internal components or circuits of the sensing sub-pixel and control circuit described in each embodiment of the present invention. The sensing sub-pixel includes a diode 310 and a cut-off resistor Rq. The control circuit includes an amplifier 320 and a time-to-digital converter 330. The time-to-digital converter 330 includes a counting circuit 331. In this embodiment, the first end of the diode 310 is coupled to an operating voltage VOP (VOP=VBD+VEB), where VBD is a breakdown voltage (Breakdown voltage), and VEB is an excess bias voltage (Excess bias voltage). The cut-off resistor Rq is coupled between the second end of the diode 310 and the ground voltage. There is a node voltage VA between the cut-off resistor Rq and the second end of the diode 310. The input end of the amplifier 320 is coupled to the second end of the diode 310. The output end of the amplifier 320 is coupled to the time-to-digital converter 330. In this embodiment, the control circuit (for example Figure 1 The control circuit 110 can control the bias voltage of the diode 310 so that the diode 310 operates in the Geiger mode or the avalanche linear mode to receive the light emitted by a specific light source (e.g. Figure 1In this regard, when the diode 310 senses a single photon or a few photons (micro photons) of the ranging light, the input end of the amplifier 320 can receive a sensing signal provided by the diode 310, wherein the sensing signal can be a single photon sensing signal. Furthermore, the output end of the amplifier 320 can output a sensing signal VOUT after signal amplification to the time-to-digital converter 330, wherein the sensing signal VOUT after signal amplification can be, for example, a square wave pulse signal.

[0056] In the present embodiment, the time-to-digital converter 330 can directly transmit the square wave pulse signal to the multiple counting units in the counting circuit 331, and the multiple counting values ​​of the counting circuit 331 are the histogram data corresponding to the distance sensing result. In other words, the time-to-digital converter 330 of the present embodiment does not need to first store the data of the multiple distance digital values ​​of the distance sensing result, and after generating the histogram data according to the data of the multiple distance digital values ​​(DN value), the histogram data is then stored (ie two steps). The time-to-digital converter 330 of the present embodiment can directly generate the histogram data of the distance sensing result (ie one step), so the time-to-digital converter 330 of the present embodiment can effectively save the storage space in the data processing process of generating the histogram data. The counting circuit 331 can be directly used as a storage unit to store the histogram data. From another perspective, the time-to-digital converter 330 of the present embodiment only needs a smaller data storage space, which can effectively reduce the hardware cost of the internal storage.

[0057] Figure 4 FIG. 4 is a characteristic curve diagram of a diode according to an embodiment of the present invention. Figure 5 FIG. 1 is a flow chart of a calibration method according to an embodiment of the present invention. Figure 1 , Figure 2 as well as Figure 4 The diode of the sub-sensing pixel described in this embodiment may have the following Figure 4 Characteristic curve 401 is shown. Figure 4 The horizontal axis is the bias voltage V of the diode, and the vertical axis is the current I that the diode can generate due to photoelectric conversion under the corresponding bias. When the bias voltage V of the diode is greater than 0 (such as Figure 4 The diode can operate in solar cell mode when the bias voltage V of the diode is between 0 and the avalanche voltage V_APD (e.g. Figure 4The diode can be operated in the photodiode mode when the bias voltage V of the diode is between the avalanche breakdown voltage V_APD and the collapse voltage V_SPAD (e.g. Figure 4 The voltage range M3 shown in the figure shows that the diode can operate in the avalanche linear mode. When the bias voltage V of the diode is less than the breakdown voltage V_SPAD (such as Figure 4 In this embodiment, the control circuit 110 controls the bias voltages of the multiple diodes of the sensing sub-pixels 121_1 to 121_N so that the multiple diodes operate in the Geiger mode or the avalanche linear mode to receive the ranging light emitted by the light source 130.

[0058] Figure 5 is a flow chart of a distance measurement method according to an embodiment of the present invention. Figure 1 , Figure 3 and Figure 5 , the optical sensor 100 of the present invention can perform the following steps S510 to S550 to perform distance measurement. In step S510, the control circuit 110 can operate the diode 310 of the sensing sub-pixel to operate in the Geiger mode or the avalanche linear mode. In step S520, the control circuit 110 can emit distance measurement light through the light source 130. In step S530, the control circuit 110 can sense the reflected light corresponding to the distance measurement light through the diode 310 of the sensing sub-pixel. In step S540, when the time-to-digital converter 330 receives the sensing signal provided by the diode 310 of the sensing sub-pixel, the time-to-digital converter 330 can generate a plurality of count values ​​according to the sensing signal through a plurality of counting units of the counting circuit 331, wherein the plurality of count values ​​are histogram data corresponding to the distance sensing result. That is, the plurality of counting units of the counting circuit 331 simultaneously serve as a time-to-digital conversion (TDC) unit and a storage unit. Therefore, the distance measurement method of this embodiment can effectively save storage space in the data processing process of the time-to-digital converter 330 generating histogram data.

[0059] Figure 6 FIG. 1 is a circuit diagram of a time-to-digital converter according to an embodiment of the present invention. Figure 6 , the above Figure 5 Step S540 of the embodiment may be performed by Figure 6 The circuit architecture shown is implemented, and Figure 3 The time-to-digital converter 330 may further include Figure 6The architecture of the time-to-digital converter 630 is shown in the figure. The following description takes the sensing result of a sensing sub-pixel as an example, so the overall sensing result of the sensing array can be deduced by analogy as described below. In the present embodiment, the time-to-digital converter 630 includes a controller 633, a first switch SS, a plurality of second switches S1_1~S1_M, S2_1~S2_a, S3_1~S2_b, SP_1, SP_2 and a counting circuit 631, wherein M, a, b, and P are positive integers. In the present embodiment, the second switches S1_1~S1_M, S2_1~S2_a, S3_1~S2_b~SP_1~SP_2 can be coupled to form a Figure 6 The tree structure shown in FIG. 1 is a tree structure, but the present invention is not limited thereto. The first end of the first switch SS is coupled to the sensing sub-pixel (eg, coupled to Figure 3 The second end of the first switch SS is coupled to the first end of the second switches SP_1-SP_2, and the second ends of the second switches S1_1-S1_M are coupled to the plurality of counting units 631_1-631_M of the counting circuit 631. The counting units 631_1-631_M may be up-counters (up_counters), respectively.

[0060] In this embodiment, the counting circuit 631 can output a first switching signal to the first switch SS to turn on the first switch SS to start the counting operation, and when the counting circuit 631 completes the counting result of a sensor signal, the counting circuit 631 turns off the first switch SS to stop counting and output the histogram data. In addition, the controller 633 can output a plurality of second switching signals to control at least one of the second switches S1_1 to S1_M, S2_1 to S2_a, S3_1 to S2_b, SP_1, and SP_2 to be turned on, so that the sensor signal 601 is written into one of the counting units 631_1 to 631_M, wherein the sensor signal 601 described in this embodiment can refer to the single photon sensor signal or the square wave pulse signal as described above.

[0061] Matching reference Figure 7 , Figure 7 6 is a signal timing diagram of a plurality of second switching signals and a sensing signal according to an embodiment of the present invention. Taking a single photon sensing signal as an example, the controller 633 of the time-to-digital converter 630 can output a plurality of second switching signals to the second switches S1_1 to S1_M, S2_1 to S2_a, S3_1 to S2_b, SP_1, and SP_2, wherein the second switches S1_1 to S1_M can receive the following signals: Figure 7The second switching signals EN_1 to EN_M shown. In this way, in conjunction with the actuation of other second switches, the plurality of signal transmission paths between the counting units 631_1 to 631_M and the first switch SS can be turned on in sequence during different periods. For example, the signal transmission path between the counting unit 631_1 and the first switch SS can be turned on during the period from time t0 to time t1. The signal transmission path between the counting unit 631_2 and the first switch SS can be turned on during the period from time t1 to time t2. Similarly, the signal transmission path between the counting unit 631_M and the first switch SS can be turned on during the period from time t(M-1) to time tM. The time intervals between each adjacent time from time t0 to time tM are equal. In this regard, when the first switch SS receives the sensing signal SP1 provided by the diode of the sensing sub-pixel during the period from time t1 to time t2. The counting unit 631_2 can increase the count value (count value + 1) according to the pulse SP1 of the single-photon sensing signal S1.

[0062] Matching reference Figure 8 , Figure 8 The time-to-digital converter 630 can perform the above-mentioned processing on the multiple sensing signals corresponding to a distance measuring light, each having a single photon or a plurality of photons (micro photons), received in sequence. Figure 7 When the counting circuit 631 determines that any counting unit reaches a preset value or the counting time length reaches a preset time length, the counting circuit 631 can turn off the first switch SS and directly store the counting results of the counting units 631_1 to 631_M as, for example, Figure 8 The histogram data shown corresponds to the distance sensing results. Figure 8 The histogram shown may be the counting result of the counting circuit 631 during a counting time length of time 0 to TA, and the histogram has the highest count value at time TB. The light sensor can convert the distance value of the current sensing object according to time TB. For another example, the number of counting units 631_1 to 631_M can be 256, so the time-to-digital converter 630 of this embodiment can generate high counting resolution histogram data with a time accuracy of 8 bits (the period of time 0 to TA can correspond to counts 0 to 255).

[0063] Fig. 9 FIG. 1 is a circuit diagram of a counting circuit according to another embodiment of the present invention. Figure 6 and Fig. 9 , the above Figure 5 Step S540 of the embodiment may be performed by Fig. 9 The circuit architecture shown is implemented, and Figure 3 and Figure 6The counting circuit 331 and the counting circuit 631 may further include: Fig. 9 The structure of the counting circuit 931 is shown. The following description takes the sensing result of a sensing sub-pixel as an example, so the overall sensing result of the sensing array can be deduced by analogy as described below. In this embodiment, the counting circuit 931 may include a plurality of delay units 902_1 to 902_M, a plurality of flip-flops 904_1 to 904_M, a plurality of inverters 905_1 to 905_M, a plurality of first AND gates 906_1 to 906_M, a second AND gate 907_1 to 907_M, and a plurality of counting units 931_1 to 931_M. The plurality of first terminals of the delay units 902_1 to 902_M may be coupled to Figure 6 The plurality of clock signal input terminals of the flip-flops 904_1 to 904_M are coupled to the second terminals of the second switches S1_1 to S1_M, and the plurality of data input terminals of the flip-flops 904_1 to 904_M are coupled to the reference voltage 903. The flip-flops 904_1 to 904_M may be D-type flip-flops. The plurality of first input terminals of the first AND gates 906_1 to 906_M are coupled to the plurality of data output terminals of the flip-flops 904_1 to 904_M. The plurality of input terminals of the inverters 905_1 to 905_M are respectively coupled to the data output terminals of the next stage inverters, and the plurality of output terminals of the inverters 905_1 to 905_M are coupled to the plurality of second input terminals of the first AND gates 906_1 to 906_M. The first input terminals of the second AND gates 907_1-907_M are coupled to the data output terminals of the first AND gates 906_1-906_M, the second input terminals of the second AND gates 907_1-907_M are coupled to the second terminals of the delay units 902_1-902_M, and the output terminals of the second AND gates 907_1-907_M are coupled to the counting units 931_1-931_M.

[0064] Matching reference Fig.10 , Fig.10 FIG. 1 is a signal timing diagram of a plurality of second switching signals and a sensing signal according to another embodiment of the present invention. In this embodiment, the second switches S1_1 to S1_M can receive the following signals: Fig.10The second switching signals EN_1'-EN_M' shown in the figure, wherein at least a portion of the multiple conduction periods of the second switching signals EN_1'-EN_M' partially overlap. In this way, in conjunction with the actuation of other second switches, the multiple signal transmission paths between the counting units 931_1-931_M and the first switch SS can be sequentially turned on during different periods, and a number of adjacent transmission paths can have partially overlapping conduction periods. For example, the signal transmission path between the counting unit 931_1 and the first switch SS can be turned on during the period from time t0' to time t4'. The signal transmission path between the counting unit 931_2 and the first switch SS can be turned on during the period from time t1' to time t5'. Similarly, the signal transmission path between the counting unit 931_M and the first switch SS can be turned on during the period from time t(M-1)' to time t(M+4)'.

[0065] In this regard, when the first switch SS receives a pulse SP2 of the single photon sensing signal S2 provided by the diode of the sensing sub-pixel during the period from time t1′ to time t2′, as shown in FIG. Fig. 9 , the second switch S1_1 outputs the sensing signal 901_1, and the second switch S1_2 outputs the sensing signal 901_2. The second switches S1_3 to S1_M do not output a signal. The delayed sensing signal is output to the second input terminal of the second AND gate 907_2 via the delay unit 9022. The flip-flop 904_2 outputs a digital value "1" to the first input terminal of the first AND gate 906_2. Since the flip-flop 904_3 outputs a digital value "0", the inverter 905_2 outputs a digital value "1" to the second input terminal of the first AND gate 906_2. The output terminal of the first AND gate 906_2 outputs a digital value "1" to the first input terminal of the first AND gate 907_2. Therefore, the counting unit 931_2 can receive the sensing signal and increase the count value (count value + 1) according to the sensing signal. From another perspective, the counting circuit 931 of this embodiment can automatically enable the corresponding counting unit to count correctly according to the second switch that outputs the sensing signal last among the second switches S1_1 - S1_M.

[0066] Compared to Figure 7 The second switching signals EN_1 to EN_M, Fig.10 The conduction period of each of the second switching signals EN_1′ to EN_M′ shown in FIG. Figure 7 In other words, based on the design of the counting circuit 931 of the present embodiment, the controller 633 of the time-to-digital converter 630 of the present embodiment can use a clock signal with a lower speed to generate the following Fig.10Therefore, the time-to-digital converter 630 of this embodiment can have a lower hardware cost (the clock signal accuracy can be lower), but can still achieve the same Figure 6 and Figure 7 The histogram data of the counting result with high counting resolution described in the embodiment. It is worth mentioning that since the clock signal is a relatively low-speed signal, the counting circuit 630 can be implemented using a low-speed circuit. In other words, this embodiment can significantly reduce the operating frequency of the time-to-digital converter circuit, and also reduce the difficulty of designing the time-to-digital converter circuit.

[0067] Fig.11 FIG. 1 is an operation timing diagram of a light sensor according to another embodiment of the present invention. Figure 1 , Figure 2 and Fig.11 First, it should be explained that since the multiple diodes of the sensing sub-pixels 121_1~121_N are respectively used as single-photon collapse diodes (operating in Geiger mode or abrupt linear mode), when the multiple diodes respectively sense photons and a collapse event occurs, the sensing sub-pixels 121_1~121_N must re-bias the multiple diodes respectively, so there will be a period during which the photons cannot be measured (which may be called dead time). In this regard, in order to reduce the impact of the dead time, the control circuit 110 of the present embodiment may, for example, set each of the multiple sensing sub-pixels in the sensing sub-pixels 121_1~121_N of the present embodiment as a sensing pixel (or macro-pixel). For example, refer to Figure 1 , the four sensing sub-pixels 121_A to 121_D can be used as a sensing pixel 122, where A to D are positive integers and are less than or equal to N. The control circuit 110 can determine whether the sensing sub-pixels 121_A to 121_D respectively sense one or more photons in the corresponding same exposure time interval and synchronously generate multiple sensing currents as a pixel sensing result. For example, the control circuit 110 can calculate the distance sensing results (time difference or distance value) of the sensing sub-pixels 121_A to 121_D as a pixel sensing result.

[0068] Specifically, when the four diodes of the sensing sub-pixels 121_A to 121_D are operated in the Geiger mode or the avalanche linear mode, the control circuit 110 may sequentially expose the sensing sub-pixels 121_A to 121_D belonging to the same pixel during a frame sensing period between time ta and time tg. Fig.11 In the emission timing PH1-PH4 of the ranging light shown, during the period from time ta to time tg, for example, four ranging light signals (photons) P1-P4 are emitted to the sensing pixel 122. Fig.11In the exposure operation timings EP1 to EP4 shown, when the sensing sub-pixel 121_1 receives the ranging light signal P1 at time ta in the exposure period T1, the sensing sub-pixel 121_1 needs to wait for a delay time Td before the next exposure operation can be performed. In this regard, if the exposure periods T2 to T4 of the sensing sub-pixels 121_B to 121_D are the same as the exposure period T1, the sensing sub-pixels 121_A to 121_D can only receive the ranging light signal P1, and the ranging light signals P2 to P4 cannot be sensed because the sensing sub-pixels 121_A to 121_D are in the dead time.

[0069] Therefore, in this embodiment, the exposure start time of the exposure periods T2 to T4 of the sensing sub-pixels 121_B to 121_D can be sequentially delayed to time tb to td, respectively, and the exposure periods T1 to T4 can be partially overlapped with each other. In this way, the sensing sub-pixel 121_B can receive the ranging light signal P2 between time tb and time te in the exposure period T2. The sensing sub-pixel 121_C can receive the ranging light signal P3 between time tc and time tf in the exposure period T3. The sensing sub-pixel 121_D can receive the ranging light signal P4 between time td and time tg in the exposure period T4. Therefore, the sensing sub-pixels 121_B to 121_D can effectively receive all the ranging light signals P1 to P4, thereby reducing the influence of the dead time and providing accurate sensing results.

[0070] In summary, the optical sensor and the distance measurement method of the present invention can effectively reduce the storage space requirement of the memory in the time-to-digital converter, and / or reduce the accuracy requirement of the clock signal, and / or reduce the operating frequency of the time-to-digital converter circuit, and / or reduce the design difficulty of the time-to-digital converter circuit. Therefore, the optical sensor and the distance measurement method of the present invention can use a relatively low-cost time-to-digital converter to realize the histogram data of the counting result with high counting resolution.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A light sensor, characterized in that: include: light source; a sensing sub-pixel, including a diode; as well as A control circuit is coupled to the light source and the sensing sub-pixel and is used to operate the diode in a Geiger mode or an avalanche linear mode, The control circuit includes a time-to-digital converter coupled to the sensing sub-pixel, and the time-to-digital converter includes: A counting circuit, coupled to the sensing sub-pixel and comprising a plurality of counting units; a controller, a first switch, and a plurality of second switches, When the time-to-digital converter receives the sensing signal provided by the sensing sub-pixel, the time-to-digital converter generates a plurality of counting values ​​according to the sensing signal through the plurality of counting units of the counting circuit, wherein the plurality of counting values ​​are histogram data corresponding to the distance sensing result, wherein a first end of the first switch is coupled to the sensing sub-pixel, a second end of the first switch is coupled to first ends of the plurality of second switches, and second ends of the plurality of second switches are coupled to the plurality of counting units, wherein the counting circuit outputs a first switching signal to the first switch, and the controller outputs a plurality of second switching signals to control the plurality of second switches, When the sensing sub-pixel provides the sensing signal, the first switch is turned on and at least one of the plurality of second switches is turned on, so that the sensing signal is written into one of the plurality of counting units. The sensing signal is a single-photon sensing signal.

2. The optical sensor according to claim 1, characterized in that The plurality of second switches are coupled to form a tree structure.

3. The optical sensor according to claim 1, characterized in that A plurality of signal transmission paths between the plurality of counting units and the first switch are sequentially turned on during different periods.

4. The optical sensor according to claim 1, characterized in that The plurality of counting units are respectively up-counting counters.

5. The optical sensor according to claim 1, characterized in that The plurality of counting units output the plurality of counting values ​​of counting results of the plurality of single photon sensing signals of the sensing signal during a sensing period, so that the time-to-digital converter generates the histogram data corresponding to the distance sensing result according to the plurality of counting values.

6. The optical sensor according to claim 1, characterized in that The counting circuit also includes: a plurality of delay units, wherein a plurality of first terminals of the plurality of delay units are coupled to the second terminals of the plurality of second switches; A plurality of flip-flops, wherein a plurality of clock signal input terminals of the plurality of flip-flops are coupled to the second terminals of the plurality of second switches, and a plurality of data input terminals of the plurality of flip-flops are coupled to a reference voltage; a plurality of first AND gates, wherein a plurality of first input terminals of the plurality of first AND gates are coupled to a plurality of data output terminals of the plurality of flip-flops; A plurality of inverters, wherein a plurality of input terminals of the plurality of inverters are respectively coupled to the data output terminal of the next stage inverter, and a plurality of output terminals of the plurality of inverters are coupled to a plurality of second input terminals of the plurality of first AND gates; and A plurality of second AND gates, wherein the plurality of first input terminals of the plurality of second AND gates are coupled to the plurality of data output terminals of the plurality of first AND gates, the plurality of second input terminals of the plurality of second AND gates are coupled to the plurality of second terminals of the plurality of delay units, and the plurality of output terminals of the plurality of second AND gates are coupled to the plurality of counting units.

7. The optical sensor according to claim 6, characterized in that The on-time periods of at least a portion of the second switching signals partially overlap.

8. The optical sensor according to claim 1, characterized in that The invention also includes at least another sensing sub-pixel. The sensing sub-pixel and the at least another sensing sub-pixel belong to the same pixel, and the sensing sub-pixel and the at least another sensing sub-pixel are exposed sequentially during a sensing period.

9. The optical sensor according to claim 8, characterized in that The sensing sub-pixel and the at least another sensing sub-pixel partially overlap during a plurality of exposure periods in the sensing period.

10. A distance measurement method, characterized in that: include: operating the diode of the sensing sub-pixel in Geiger mode or avalanche mode; emitting ranging light through a light source; Sensing the reflected light corresponding to the ranging light through the sensing sub-pixel; as well as When the time-to-digital converter receives the sensing signal provided by the sensing sub-pixel, a plurality of counting units of the counting circuit generate a plurality of counting values ​​according to the sensing signal, wherein the plurality of counting values ​​are histogram data corresponding to the distance sensing result, The time-to-digital converter includes a controller, a first switch, and a plurality of second switches. wherein a first end of the first switch is coupled to the sensing sub-pixel, a second end of the first switch is coupled to first ends of the plurality of second switches, and second ends of the plurality of second switches are coupled to the plurality of counting units, wherein the counting circuit outputs a first switching signal to the first switch, and the controller outputs a plurality of second switching signals to control the plurality of second switches, When the sensing sub-pixel provides the sensing signal, the first switch is turned on and at least one of the plurality of second switches is turned on, so that the sensing signal is written into one of the plurality of counting units. The sensing signal is a single-photon sensing signal.

11. The distance measurement method according to claim 10, characterized in that: The plurality of second switches are coupled to form a tree structure.

12. The distance measurement method according to claim 10, characterized in that: A plurality of signal transmission paths between the plurality of counting units and the first switch are sequentially turned on during different periods.

13. The distance measurement method according to claim 10, characterized in that: The plurality of counting units are respectively up-counting counters.

14. The distance measurement method according to claim 10, characterized in that: The plurality of counting units output the plurality of counting values ​​of counting results of the plurality of single photon sensing signals of the sensing signal during a sensing period, so that the time-to-digital converter generates the histogram data corresponding to the distance sensing result according to the plurality of counting values.

15. The distance measurement method according to claim 10, characterized in that: The counting circuit also includes: a plurality of delay units, wherein a plurality of first terminals of the plurality of delay units are coupled to the second terminals of the plurality of second switches; A plurality of flip-flops, wherein a plurality of clock signal input terminals of the plurality of flip-flops are coupled to the second terminals of the plurality of second switches, and a plurality of data input terminals of the plurality of flip-flops are coupled to a reference voltage; a plurality of first AND gates, wherein a plurality of first input terminals of the plurality of first AND gates are coupled to a plurality of data output terminals of the plurality of flip-flops; A plurality of inverters, wherein a plurality of input terminals of the plurality of inverters are respectively coupled to the data output terminal of the next stage inverter, and a plurality of output terminals of the plurality of inverters are coupled to a plurality of second input terminals of the plurality of first AND gates; and A plurality of second AND gates, wherein the plurality of first input terminals of the plurality of second AND gates are coupled to the plurality of data output terminals of the plurality of first AND gates, the plurality of second input terminals of the plurality of second AND gates are coupled to the plurality of second terminals of the plurality of delay units, and the plurality of output terminals of the plurality of second AND gates are coupled to the plurality of counting units.

16. The distance measurement method according to claim 15, characterized in that: The on-time periods of at least a portion of the second switching signals partially overlap.

17. The distance measurement method according to claim 10, characterized in that: The invention also includes at least another sensing sub-pixel. The sensing sub-pixel and the at least another sensing sub-pixel belong to the same pixel, and the sensing sub-pixel and the at least another sensing sub-pixel are exposed sequentially during a sensing period.

18. The distance measurement method according to claim 17, characterized in that: The sensing sub-pixel and the at least another sensing sub-pixel partially overlap during a plurality of exposure periods in the sensing period.

Images