Optical sensor and calibration method thereof

Abstract

The present invention provides a light sensor and a correction method thereof. The light sensor includes a light source, a sensing sub-pixel and a control circuit. The light source emits sensing light. The sensing sub-pixel includes a diode, a cut-off resistor and a time-to-digital converter. The diode has a first end coupled to an operating voltage. The cut-off resistor is coupled between the second end of the diode and a ground terminal voltage. The time-to-digital converter is coupled to the second end of the diode. The control circuit is coupled to the sensing sub-pixel and corrects the sensing sensitivity of the sensing sub-pixel based on at least one of the photon detection rate, the internal gain value, and the resistance value of the cut-off resistor of the diode corresponding to the sensing sub-pixel, so that the sensing sub-pixel generates a single-photon collapse diode sensing signal only when the sensing light is received. The light sensor and the correction method thereof of the present invention can realize a single-photon collapse diode sensing function with high reliability.

Description

Technical Field

[0001] The present invention relates to a sensing technology, and in particular to a light sensor and a calibration method thereof. Background Art

[0002] At present, high-sensitivity distance measurement sensors are in great demand in various application fields such as the medical field or the automotive field. In particular, optical sensors that can be used to sense extremely weak light are one of the main sensor design directions at present. In view of this, how to realize an optical sensor that can effectively sense extremely weak light and has the characteristics of high accuracy and reliability, the following will propose several embodiments of the solution. Summary of the invention

[0003] The present invention is directed to a light sensor and a correction method thereof, which can correct relevant setting parameters of sensing sub-pixels of the light sensor so that the light sensor can realize a single-photon collapse diode sensing function with high reliability.

[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 light source is used to emit sensing light. The sensing sub-pixel includes a diode, a cut-off resistor and a time-to-digital converter. The diode has a first end coupled to an operating voltage. The cut-off resistor is coupled between the second end of the diode and a ground voltage. The time-to-digital converter is coupled to the second end of the diode. The control circuit is coupled to the sensing sub-pixel and is used to correct the sensing sensitivity of the sensing sub-pixel based on at least one of the photon detection rate, the internal gain value, and the resistance value of the cut-off resistor of the diode corresponding to the sensing sub-pixel, so that the sensing sub-pixel generates a single-photon collapse diode sensing signal only when the sensing light is received.

[0005] According to an embodiment of the present invention, the correction method of the present invention is applicable to a light sensor. The light sensor includes a light source, a sensing sub-pixel and a control circuit. The sensing sub-pixel includes a diode, a cut-off resistor and a time-to-digital converter. The correction method includes the following steps: turning off the light source through the control circuit; adjusting the sensing sensitivity of each sensing sub-pixel to the highest through the control circuit, operating the sensing sub-pixel for sensing through the control circuit, and judging whether the sensing sub-pixel generates a single-photon collapse diode sensing signal; when the sensing sub-pixel generates a single-photon collapse diode sensing signal, correcting the sensing sensitivity of the sensing sub-pixel according to at least one of the photon detection rate, internal gain value and resistance value of the cut-off resistor of the diode corresponding to the sensing sub-pixel; turning on the light source through the control circuit; and operating the sensing sub-pixel for sensing through the control circuit, and judging whether the sensing sub-pixel generates a single-photon collapse diode sensing signal.

[0006] Based on the above, the optical sensor and the correction method thereof of the present invention can effectively correct the sensing sub-pixel so that the sensing sub-pixel will only generate a single-photon collapse diode sensing signal when receiving the sensing light emitted by the light source, thereby realizing a single-photon collapse diode sensing function with high reliability.

[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 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 calibration method according to an embodiment of the present invention;

[0013] Fig. 6A is a schematic diagram of a signal waveform curve of a sensing signal according to an embodiment of the present invention;

[0014] Figure 6B is a schematic diagram of a reference signal waveform curve according to an embodiment of the present invention;

[0015] Figure 6C is a schematic diagram of a signal waveform curve after correction according to an embodiment of the present invention;

[0016] Fig.6D is a schematic diagram of a signal waveform curve of a sensing signal according to another embodiment of the present invention;

[0017] Figure 7 FIG. 4 is an operation timing diagram of a light sensor according to an embodiment of the present invention.

[0018] Description of Reference Numerals

[0019] 100: light sensor;

[0020] 110: control circuit;

[0021] 120: sensor array;

[0022] 121_1-121_N, 121_A, 121_B, 121_C, 121_D, 300: sensing sub-pixels;

[0023] 122: sensing pixel;

[0024] 130: light source;

[0025] 310: diode;

[0026] 320: amplifier;

[0027] 330: time to digital converter;

[0028] 401: characteristic curve;

[0029] 701-704: signal waveform curve;

[0030] S510, S511, S512, S520, S530, S540: steps;

[0031] V_SPAD、V BD : Breakdown voltage;

[0032] V_APD: avalanche voltage;

[0033] VE, V EB :Excess bias;

[0034] V OP : Working voltage;

[0035] I: current;

[0036] V: voltage;

[0037] V A : Node voltage;

[0038] V OUT :sensing signal;

[0039] M1~M4: voltage range;

[0040] Rq: cut-off resistance;

[0041] ta, t0~t6: time;

[0042] P1~P4: sensing light signal;

[0043] T1~T4: exposure period;

[0044] Td: delay time;

[0045] EP1~EP4: exposure operation timing;

[0046] PH1~PH4: Emission timing of sensing light. DETAILED DESCRIPTION

[0047] 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.

[0048] 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.

[0049] 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 collapse diode (SPAD) state of the Geiger mode or the avalanche linear mode to sense the sensing light emitted by the light source 130, thereby realizing a ranging sensing function with low light quantity and high sensing sensitivity characteristics.

[0050] 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 the plurality of transistors. The control circuit 110 may control the light source 130 to emit sensing 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.

[0051] Figure 3 FIG. 1 is a schematic diagram of a circuit of a sensing sub-pixel according to an embodiment of the present invention. Figure 3 The sensing sub-pixel 300 of this embodiment can be applied to the sensing sub-pixel described in various embodiments of the present invention. In this embodiment, the sensing sub-pixel 300 includes a diode 310 and a cut-off resistor Rq, and the control circuit of the light sensor can be (eg Figure 1 The control circuit 110 includes an amplifier 320 and a time-to-digital converter 330. The time-to-digital converter 330 includes a counting circuit. In this embodiment, the first end of the diode 310 is coupled to the working voltage V OP (V OP =V BD +V EB ), where V BD is the breakdown voltage (Breakdownvoltage), and V EB The cut-off resistor Rq is coupled between the second end of the diode 310 and the ground voltage. A node voltage V A The input terminal of the amplifier 320 is coupled to the second terminal of the diode 310. The output terminal of the amplifier 320 is coupled to the time-to-digital converter 330. In this embodiment, the control circuit (eg 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 V after the signal is amplified. OUT to the time-to-digital converter 330, wherein the amplified sensing signal V OUT It may be a square wave pulse signal, for example. In this embodiment, the control circuit (eg 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 1 The sensing light emitted by the light source 130).

[0052] Figure 4 FIG. 4 is a characteristic curve diagram of a diode according to an embodiment of the present invention. Figure 5 is a flow chart of a calibration method according to an embodiment of the present invention. Figure 1 , Figure 2 , Figure 4 as well as Figure 5 , Figure 1 The optical sensor 100 may perform the following steps S510-S540 to calibrate the sensing sub-pixels 121_1-121_N. It should be noted that the diodes of the sub-sensing pixels described in this embodiment may have the following features: Figure 4 Characteristic curve 401 is shown. Figure 4 The horizontal axis is the diode bias voltage V, and the vertical axis is the diode current I under the corresponding bias voltage. When the diode bias voltage V 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 4 The diode can operate in the photodiode mode when the bias voltage V of the diode is between the avalanche 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 the voltage range M4 shown, the diode can be operated in Geiger mode.

[0053] In this embodiment, the control circuit 110 controls the bias voltages of multiple diodes of the sensing sub-pixels 121_1 to 121_N so that the multiple diodes operate in a Geiger mode or a collapse linear mode to receive the sensing light emitted by the light source 130. In step S510, the control circuit 110 turns off the light source 130. In step S511, the control circuit 110 adjusts the sensing sensitivity of each sensing sub-pixel 121_1 to 121_N to the highest. In step S512, the control circuit 110 operates each sensing sub-pixel 121_1 to 121_N for sensing. In step S520, the control circuit 110 determines whether each sensing sub-pixel 121_1 to 121_N generates a single-photon collapse diode sensing signal. If not, in step S540, the control circuit 110 ends the calibration. If yes, in step S530, the control circuit 110 calibrates the sensing sensitivity of each sensing sub-pixel. In this regard, the control circuit 110 can calibrate the sensing sensitivity of each sensing sub-pixel 121_1~121_N based on at least one of the photon detection rate of the diode corresponding to each sensing sub-pixel 121_1~121_N, the internal gain value, and the resistance value of the cut-off resistor. In addition, the control circuit 110 executes steps S520 and S530 in a loop. Until in step S520, when the control circuit 110 determines that each sensing sub-pixel 121_1~121_N does not generate a single-photon collapse diode sensing signal, the control circuit 110 ends the calibration. In other words, the control circuit 110 of the present invention can first determine whether each sensing sub-pixel 121_1~121_N has a misjudgment when the light source 130 does not emit sensing light, so as to decide whether to calibrate the sensing sensitivity of each sensing sub-pixel.

[0054] Specifically, the following combination Figure 3 To illustrate the sensing sub-pixel 300, the single-photon collapse diode sensing mechanism of the diode 310 of the present embodiment can be pre-designed so that when the diode 310 receives one photon of sensing light reflected by the sensing object, the diode 310 can generate a large current, thereby triggering a quenching circuit, and inputting the sensing signal to the time-to-digital converter 330, so that the time-to-digital converter 330 outputs a corresponding sensing time calculation. Therefore, the control circuit 110 can calculate according to the emission time of the sensing light and the above-mentioned sensing time information to obtain the time-of-flight ranging sensing result. However, the diode 310 may generate a misjudged sensing signal due to receiving multiple photons of background light or ambient light when the light source 130 does not emit sensing light. Therefore, the control circuit 110 can correct the error by executing at least one of the following correction means: Figure 2It is worth noting that the sensing sensitivities of the sensing sub-pixels 121_1 to 121_N may vary due to process variations, and therefore need to be calibrated individually.

[0055] In the first calibration method (applicable to the case where the diode 310 operates in the Geiger mode), the control circuit 110 can adjust the excess bias (excess bias, Vex) VE of the diode 310 of the sensing sub-pixel 300 operating in the Geiger mode to change the photon detection probability (PDP) of the diode 310 of the sensing sub-pixel 300, that is, the probability of a photon being received, so as to calibrate the sensing sensitivity of the light sensor 100. Figure 4 As shown, the excess bias voltage VE represents a voltage range M4 (operating range) less than the breakdown voltage V_SPAD. The control circuit 110 can reduce the excess bias voltage VE to reduce the photon detection rate of the diode 310. In other words, after the photon detection rate of the diode 310 is reduced, the diode 310 needs to receive more than N photons (for example, if the ambient light has an intensity corresponding to five photons, then N=5) to be turned on to generate a sensing signal, where N is a positive integer. For example, after the photon detection rate of the diode 310 is reduced, the diode 310 can receive one photon for every six photons, thereby triggering the cutoff circuit and inputting the sensing signal to the time-to-digital converter 330. In this regard, the control circuit 110 can, for example, perform the step-by-step adjustment mechanism of the above steps S520 and S530 to gradually adjust the excess bias voltage VE (gradually adjust the operating range of the diode 310) according to a preset adjustment voltage value (for example, adjusting 0.1V at a time). Therefore, the sensing sensitivity of the sensing sub-pixel 300 can be effectively reduced, and the diode 310 of the sensing sub-pixel 300 can be prevented from generating a misjudged sensing signal when the light source 130 does not emit sensing light.

[0056] In the second correction method (applicable to the case where the diode 310 operates in the Geiger mode or the avalanche linear mode), the control circuit 110 can change the internal gain value of the diode 310 of the sensing sub-pixel 300 by adjusting the excess bias voltage VE when the diode 310 of the sensing sub-pixel 300 operates in the Geiger mode or the bias voltage when the diode 310 operates in the avalanche linear mode, so as to correct the sensing sensitivity of the light sensor 100. In this regard, since the internal gain value of the diode 310 is increased as the bias voltage increases and is decreased as the bias voltage decreases, the control circuit 110 can reduce the internal gain value by reducing the excess bias voltage VE or the bias voltage when the diode 310 operates in the avalanche linear mode. If the internal gain value of the diode 310 is reduced, the current generated by one photon in the diode 310 is reduced. In other words, after the internal gain value of the diode 310 is reduced, the diode 310 needs to receive more than N photons (for example, if the ambient light has an intensity corresponding to five photons, then N=5) to generate a sufficiently large current, thereby triggering the cutoff circuit and inputting the sensing signal to the time-to-digital converter 330 to generate the sensing signal. For example, after the internal gain value of the diode 310 is reduced, when the diode 310 receives six photons of the sensing light, the diode 310 can generate a sufficiently large current, thereby triggering the cutoff circuit and inputting the sensing signal to the time-to-digital converter. In this regard, the control circuit 110 can, for example, perform the step-by-step adjustment mechanism of the above steps S520 and S530 to gradually adjust the excess bias voltage VE or the bias voltage operating in the avalanche linear mode (gradually adjust the operating range of the diode 310) according to a preset adjustment voltage value (for example, adjusting 0.1V at a time). Therefore, the sensing sensitivity of the sensing sub-pixel 300 can be effectively reduced, and the diode 310 of the sensing sub-pixel 300 can be prevented from generating a misjudged sensing signal when the light source 130 does not emit sensing light.

[0057] In the third calibration method (applicable to the diode 310 operating in the Geiger mode or the avalanche linear mode), the control circuit 110 can calibrate the sensing sensitivity of the light sensor 100 by adjusting the resistance value of the cut-off resistor Rq (the cut-off resistor Rq can be a variable resistor) of the sensing sub-pixel 300. In this regard, if the resistance value of the cut-off resistor Rq is reduced, the node voltage V generated by one photon received by the diode 310 A (V=IR) will also be reduced. In other words, after the resistance value of the cut-off resistor Rq is reduced, the diode 310 needs to receive more than N photons (for example, if the ambient light intensity is corresponding to five photons, then N=5) to trigger the cut-off circuit and input the sensing signal to the time-to-digital converter 330 to generate the sensing signal. For example, after the resistance value of the cut-off resistor Rq is reduced, when the diode 310 receives six photons of the sensing light, the node voltage V generated by the diode 310 according to the six photons is AThe cut-off resistor Rq is large enough to trigger the cut-off circuit and input the sensing signal to the time-to-digital converter 330. In this regard, the control circuit 110 may, for example, perform the step-by-step adjustment mechanism of steps S520 and S530 to gradually reduce the resistance value of the cut-off resistor Rq according to the preset adjustment resistance value. Therefore, the sensing sensitivity of the sensing sub-pixel 300 can be effectively reduced, and the diode 310 of the sensing sub-pixel 300 can be prevented from generating a misjudged sensing signal when the light source 130 does not emit sensing light.

[0058] In the fourth correction means (applicable to the diode 310 operating in the Geiger mode or the avalanche linear mode), in the above step S530, alternatively, the control circuit 110 may adjust the number of co-incidience operations of the sensing sub-pixel 300 and at least another sensing sub-pixel to correspondingly correct the overall sensing sensitivity of the light sensor 100. In this regard, it is first explained that the control circuit 110 may determine whether the sensing sub-pixel 300 and the multiple diodes of the at least another sensing sub-pixel synchronously generate multiple sensing currents during the exposure time interval to confirm whether the sensing sub-pixel 300 and the multiple diodes of the at least another sensing sub-pixel sense light. In other words, the control circuit 110 may, for example, set each of the multiple sensing sub-pixels 121_1 to 121_N of the present embodiment as a sensing pixel (or macro-pixel). For example, refer to Figure 2 , 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 use the distance sensing results (time difference or distance value) of the sensing sub-pixels 121_A to 121_D as a pixel sensing result. Therefore, since the sensing sub-pixels 121_A to 121_D of the sensing pixel 122 need to each receive a photon of sensing light, the control circuit 110 will use the multiple sensing currents of the sensing sub-pixels 121_A to 121_D as a pixel sensing result. In other words, the sensing pixel 122 needs to receive four photons to generate a pixel sensing result. Therefore, the overall sensing sensitivity of the optical sensor 100 can be effectively reduced, and the generation of erroneous sensing signals when the light source 130 does not emit sensing light can be avoided.

[0059] In the fifth calibration means (applicable to the diode 310 operating in the Geiger mode or the avalanche linear mode), in the above step S530, alternatively, the control circuit 110 may operate the light source 130 to emit sensing light corresponding to a specific pulse code, and the control circuit 110 may determine whether the sensing signal output by the time-to-digital converter 330 of the sensing sub-pixel 300 corresponds to the specific pulse code, so as to generate a confirmed sensing result. In other words, the control circuit 110 may control the light source 130 to emit sensing light of a specific pulse code or a specific pattern, and determine whether the sensing signal generated by the sensing sub-pixels 121_1 to 121_N of the sensing array 120 has the corresponding sensing result of the specific pulse code or the specific pattern, so as to effectively prevent the light sensor 100 from generating a misjudged sensing signal when the light source 130 does not emit sensing light.

[0060] In the sixth correction means (applicable to the case where the diode 310 operates in the Geiger mode or the avalanche linear mode), in the above step S530, alternatively, the control circuit 110 may adjust the fill factor of the sensing array 120 to correct the overall sensing sensitivity of the light sensor 100. The control circuit 110 may reduce the fill factor of the sensing array 120 so that the overall sensing sensitivity of the light sensor 100 is reduced accordingly to effectively avoid the light sensor 100 from generating a misjudged sensing signal when the light source 130 does not emit sensing light. In this embodiment, the control circuit 110 adjusts the fill factor by disabling a portion of the plurality of sub-pixels in each of the plurality of macro pixels of the light sensor 100 during the sensing period to reduce the sensing sensitivity. For example, the control circuit 110 disables Q of the P sub-pixels in each of the plurality of macro pixels of the light sensor 100 during the sensing period, where P and Q are positive integers and P is greater than Q.

[0061] Fig. 6A FIG. 4 is a schematic diagram of a signal waveform curve of a sensing signal according to an embodiment of the present invention. Figure 6B is a schematic diagram of a reference signal waveform curve according to an embodiment of the present invention. Figure 6C FIG. 1 is a schematic diagram of a signal waveform curve after correction according to an embodiment of the present invention. Figure 1 , Figure 2 , FIG. 6A to FIG. 6C In this embodiment, the control circuit 110 can calibrate the sensing signal of each of the sensing sub-pixels 121_1 to 121_N. When the diodes of the sensing sub-pixels 121_1 to 121_N are operated in the Geiger mode or the avalanche linear mode, the control circuit 110 can establish the following respectively according to the sensing signals provided by the plurality of diodes of the sensing sub-pixels 121_1 to 121_N during the sensing period: Fig. 6A It is worth noting that the signal waveform curve of this embodiment can also be presented in the form of histogram data.

[0062] For example, since the diode operates in the Geiger mode or the avalanche linear mode, the signal waveform curve 701 of the sensing signal may have a corresponding sensing result corresponding to the number of photons of the sensing light at time ta. However, since the diode is easily affected by the ambient light or background light when operating in the Geiger mode or the avalanche linear mode, if the control circuit 110 determines whether the sensing light is received based on the sensing result of whether the signal waveform curve 701 exceeds 3 photons, the influence of the ambient light or background light on the signal curve 701 is higher than or equal to 3 photons (corresponding to the signal strength of the ambient light or background light, for example, up to 10 photons). In this regard, the control circuit 110 may establish another sensing signal based on another sensing period of the sensing light not emitted by the light source 130 provided by each of the multiple diodes. Figure 6B The reference signal waveform curve 702 is shown. The control circuit 110 can compare Fig. 6A The signal waveform curve 701 and Figure 6B The control circuit 110 can perform numerical subtraction on the signal waveform curve 701 and the reference signal waveform curve 702 to generate Figure 6C The signal waveform curve 703 after correction is shown. Therefore, the control circuit 110 can analyze the signal waveform curve 703 to determine whether the sensing light is received by judging that the signal waveform curve 703 has a curve change of the sensing result greater than or equal to 3 photons at the time ta. Therefore, since the sensing sub-pixels 121_1 to 121_N can each perform the correction processing of the signal waveform, the optical sensor 100 of this embodiment can effectively confirm whether the plurality of diodes each sense the sensing light emitted by the light source 130.

[0063] However, in other embodiments of the present invention, the control circuit 110 may also infer the reference signal waveform curve 702 corresponding to the background sensor signal portion in the sensor signal based on the numerical distribution of the individual signal waveform curves 701 of the plurality of diodes. It is worth noting that the aforementioned inference method may utilize the Poisson distribution. Specifically, since the waveform of the background sensor signal is a Poisson distribution, the control circuit 110 may infer the numerical distribution of the signal waveform curve 701 based on the Poisson distribution to obtain the reference signal waveform curve 702 corresponding to the background sensor signal portion in the sensor signal. Furthermore, the control circuit 110 may perform numerical subtraction between the signal waveform curve 701 and the reference signal waveform curve 702 inferred by the Poisson distribution to obtain the signal waveform curve 703.

[0064] Fig.6D FIG. 1 is a schematic diagram of a signal waveform curve of a sensing signal according to another embodiment of the present invention. Figure 1 , Figure 2 and Fig.6D In some other embodiments of the present invention, the sensing light emitted by the light source 130 may have a first polarization (e.g., vertical polarization or horizontal polarization). Each of the sensing sub-pixels 121_1 to 121_N may include a filter having a first polarization so that the plurality of diodes of the sensing sub-pixels 121_1 to 121_N can only receive light having the first polarization. Therefore, the control circuit 110 may sense the sensing signals provided by the plurality of diodes of the sensing sub-pixels 121_1 to 121_N during the sensing period to establish the signal waveform curve 704. In this regard, since the ambient light or background light has the characteristic of being unpolarized, the signal intensity of the sensing result corresponding to the background light or ambient light in the signal waveform curve 704 may be reduced (the signal intensity corresponding to the ambient light or background light is, for example, 5 photons). In this way, the signal intensity of the portion of the signal waveform curve 704 corresponding to the ambient light or background light is reduced. In contrast, the signal intensity of the signal waveform curve 704 corresponding to the sensing result at time ta is enhanced. Therefore, the signal waveform curve 704 can make it easier for the control circuit 110 to perform signal analysis, thereby effectively obtaining the sensing result at time ta.

[0065] Figure 7 FIG. 1 is an operation timing diagram of a light sensor according to an embodiment of the present invention. Figure 1 , Figure 2 and Figure 7 First, it should be explained that since the multiple diodes of the sensing sub-pixels 121_1 to 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 to 121_N must re-bias the multiple diodes respectively, so there will be a period of time when photons cannot be sensed (which can be called dead time). In this regard, in order to reduce the impact of the dead time, the control circuit 110 of this embodiment can set each of the multiple sensing sub-pixels in the sensing sub-pixels 121_1 to 121_N as a sensing pixel. For example, refer to Figure 1 , the four sensing sub-pixels 121_A to 121_D can serve as one sensing pixel 122 .

[0066] 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 from time t0 to time t6. Figure 7 In the sensor light emission timing PH1-PH4 shown, during the period from time t0 to time t6, for example, four sensor light signals (photons) P1-P4 are emitted to the sensor pixel 122. Figure 7 In the exposure operation timings EP1 to EP4 shown, when the sensing sub-pixel 121_1 receives the sensing light signal P1 at time t1 in the exposure period T1, the sensing sub-pixel 121_1 needs to undergo 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_2 to 121_4 are the same as the exposure period T1, the sensing sub-pixels 121_1 to 121_4 can only receive the sensing light signal P1, and the sensing light signals P2 to P4 cannot be sensed because the sensing sub-pixels 121_1 to 121_4 are in the dead time.

[0067] Therefore, in this embodiment, the exposure start time of the exposure periods T2 to T4 of the sensing sub-pixels 121_2 to 121_4 can be sequentially delayed to time t2 to t4, and the exposure periods T1 to T4 can be partially overlapped. In this way, the sensing sub-pixel 121_2 can receive the sensing light signal P2 between time t1 and time t2 in the exposure period T2. The sensing sub-pixel 121_3 can receive the sensing light signal P3 between time t3 and time t4 in the exposure period T3. The sensing sub-pixel 121_4 can receive the sensing light signal P4 between time t5 and time t6 in the exposure period T4. Therefore, the sensing sub-pixels 121_2 to 121_4 can effectively receive all the sensing light signals P1 to P4 and provide accurate sensing results.

[0068] In summary, the optical sensor and the correction method thereof of the present invention can effectively correct the sensing sub-pixel and / or the sensing array so that the optical sensor will only generate a sensing signal when it receives the sensing light emitted by the light source. In addition, the optical sensor and the correction method thereof of the present invention can also correct the signal waveform curve of the sensing signal so that the corrected sensing signal can be easily analyzed by the control circuit. In addition, the optical sensor and the correction method thereof of the present invention can also effectively reduce the influence of the dead time of the sensing sub-pixel and provide accurate sensing results.

[0069] 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: A light source for emitting sensing light; Sensing sub-pixels, including: A diode having a first end coupled to an operating voltage; a cut-off resistor coupled between the second end of the diode and a ground voltage; and a time-to-digital converter coupled to the second end of the diode; and a control circuit coupled to the sensing sub-pixel and configured to calibrate the sensing sensitivity of the sensing sub-pixel according to at least one of a photon detection rate of the diode corresponding to the sensing sub-pixel, an internal gain value, and a resistance value of the cut-off resistor, so that the sensing sub-pixel generates a single-photon collapse diode sensing signal only when the sensing light is received, When the diode of the sensing sub-pixel is operated in the Geiger mode or the avalanche linear mode, the control circuit establishes a signal waveform curve according to the sensing signal provided by the sensing sub-pixel during the sensing period, and the control circuit compares the signal waveform curve with a reference signal waveform curve to confirm whether the sensing sub-pixel senses the sensing light emitted by the light source.

2. The optical sensor according to claim 1, characterized in that The control circuit changes the photon detection rate of the diode of the sensing sub-pixel by adjusting an excess bias voltage at which the diode of the sensing sub-pixel operates in a Geiger mode, so as to correct the sensing sensitivity of the sensing sub-pixel.

3. The optical sensor according to claim 1, characterized in that The control circuit changes the internal gain value of the diode of the sensing sub-pixel by adjusting an excess bias voltage when the diode of the sensing sub-pixel operates in a Geiger mode or a bias voltage when the diode operates in an avalanche linear mode to correct the sensing sensitivity of the sensing sub-pixel.

4. The optical sensor according to claim 1, characterized in that The control circuit further adjusts the number of cooperative operations of the sensing sub-pixel and at least another sensing sub-pixel to correspondingly correct the overall sensing sensitivity of the light sensor. The control circuit determines whether the multiple diodes of the sensing sub-pixel and the at least another sensing sub-pixel synchronously generate multiple sensing currents during an exposure time interval to confirm whether the multiple diodes of the sensing sub-pixel and the at least another sensing sub-pixel sense light.

5. The optical sensor according to claim 1, characterized in that The control circuit operates the light source to emit the sensing light corresponding to a specific pulse code, and the control circuit determines whether the sensing signal output by the time-to-digital converter of the sensing sub-pixel corresponds to the specific pulse code to generate a confirmed sensing result.

6. The optical sensor according to claim 1, characterized in that The control circuit disables a portion of the plurality of sensing sub-pixels of each of the plurality of macro-pixels of the light sensor to adjust a filling factor of the sensing sub-pixels and correct an overall sensing sensitivity of the light sensor.

7. The optical sensor according to claim 1, characterized in that The control circuit distributes the value of the signal waveform curve according to Poisson distribution to obtain the reference signal waveform curve corresponding to the background sensor signal part in the sensor signal.

8. The optical sensor according to claim 1, characterized in that The reference signal waveform curve is established by the control circuit according to another sensing signal provided by the diode of another sensing sub-pixel when the light source does not emit the sensing light.

9. The optical sensor according to claim 1, characterized in that The sensing light emitted by the light source has a first polarization, The diode has the first polarized filter and is used for receiving reflected light corresponding to the sensing light.

10. The optical sensor according to claim 1, characterized in that When the plurality of diodes of the sensing sub-pixel and at least another sensing sub-pixel belonging to the same pixel are operated in a Geiger mode or an avalanche linear mode, the sensing sub-pixel and the at least another sensing sub-pixel are sequentially exposed during one frame sensing period.

11. The optical sensor according to claim 10, characterized in that The exposure periods of the sensing sub-pixel and at least another sensing sub-pixel partially overlap.

12. A calibration method, applicable to an optical sensor, characterized in that: The light sensor includes a light source, a sensing sub-pixel and a control circuit, and the sensing sub-pixel includes a diode, a cut-off resistor and a time-to-digital converter, wherein the correction method includes: Turning off the light source by the control circuit; Adjusting the sensing sensitivity of the sensing sub-pixel to the highest level through the control circuit; The control circuit operates the sensing sub-pixel to perform sensing, and determines whether the sensing sub-pixel generates a single photon collapse diode sensing signal; When the sensing sub-pixel generates the single-photon collapse diode sensing signal, the sensing sensitivity of the sensing sub-pixel is corrected according to at least one of a photon detection rate of the diode corresponding to the sensing sub-pixel, an internal gain value, and a resistance value of the cut-off resistor; When the diode of the sensing sub-pixel is operated in a Geiger mode or an avalanche linear mode, a signal waveform curve is established by the control circuit according to a sensing signal provided by the sensing sub-pixel during a sensing period; and The control circuit compares the signal waveform curve with a reference signal waveform curve to confirm whether the sensing sub-pixel senses the sensing light emitted by the light source.

13. The calibration method according to claim 12, characterized in that: The step of correcting the sensing sensitivity of the sensing sub-pixel comprises: The control circuit adjusts the excess bias voltage of the diode of the sensing sub-pixel when the diode operates in the Geiger mode to change the photon detection rate of the diode of the sensing sub-pixel to correct the sensing sensitivity of the sensing sub-pixel.

14. The calibration method according to claim 12, characterized in that: The step of correcting the sensing sensitivity of the sensing sub-pixel comprises: The control circuit adjusts the excess bias voltage of the diode of the sensing sub-pixel operating in the Geiger mode or the bias voltage operating in the avalanche linear mode to change the internal gain value of the diode of the sensing sub-pixel to correct the sensing sensitivity of the sensing sub-pixel.

15. The calibration method according to claim 12, characterized in that: The step of correcting the sensing sensitivity of the sensing sub-pixel comprises: The control circuit adjusts the cooperative working quantity of the sensing sub-pixel and at least another sensing sub-pixel to correspondingly correct the overall sensing sensitivity of the light sensor. The control circuit determines whether the multiple diodes of the sensing sub-pixel and the at least another sensing sub-pixel synchronously generate multiple sensing currents during an exposure time interval to confirm whether the multiple diodes of the sensing sub-pixel and the at least another sensing sub-pixel sense light.

16. The calibration method according to claim 12, characterized in that: The step of correcting the sensing sensitivity of the sensing sub-pixel comprises: Operating the light source to emit sensing light corresponding to a specific pulse code through the control circuit; and The control circuit determines whether the sensing signal output by the time-to-digital converter of the sensing sub-pixel corresponds to the specific pulse code to generate a confirmed sensing result.

17. The calibration method according to claim 12, characterized in that: The step of correcting the sensing sensitivity of the sensing sub-pixel comprises: The control circuit disables a portion of the plurality of sensing sub-pixels of each of the plurality of macro-pixels of the light sensor to adjust the filling factor of the sensing sub-pixels and correct the overall sensing sensitivity of the light sensor.

18. The calibration method according to claim 12, characterized in that: Also includes: When the plurality of diodes of the sensing sub-pixel and at least another sensing sub-pixel belonging to the same pixel are operated in Geiger mode or avalanche linear mode, the sensing sub-pixel and the at least another sensing sub-pixel are operated by the control circuit to sequentially expose during one frame sensing period.

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