Photosensitive pixel circuit, image sensor, and electronic device

Abstract

The present application belongs to the technical field of images. Disclosed are a photosensitive pixel circuit, an image sensor, and an electronic device. The photosensitive pixel circuit comprises a switch element, a single-photon avalanche diode, a sensitivity adjusting module and a counting module, wherein a first end of the switch element is used for being connected to a first voltage, a second end thereof is used for accessing a switch control signal, and a third end thereof is connected to a first end of the single-photon avalanche diode, and a second end of the single-photon avalanche diode is used for being connected to a second voltage; a first input end of the sensitivity adjusting module is connected to the first end of the single-photon avalanche diode, and a second input end of the sensitivity adjusting module is used for accessing a sensitivity control signal, the sensitivity control signal being used for controlling the sensitivity adjusting module to switch between a first operation state and a second operation state; and the photosensitive pixel circuit has a first light sensitivity in the first operation state and has a second light sensitivity in the second operation state, respectively, the first light sensitivity being greater than the second light sensitivity.

Description

Photosensitive pixel circuits, image sensors, and electronic devices

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on August 31, 2023, with application number 202311112717.0 and titled “Photosensitive pixel circuit, image sensor and electronic device,” the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application belongs to the field of image technology, and specifically relates to a photosensitive pixel circuit, an image sensor, and an electronic device. Background Art

[0004] Compared to the pinned photodiode (PPD) in conventional complementary metal-oxide semiconductor (CMOS) image sensors (CIS), single-photon avalanche diodes (SPADs) have extremely high sensitivity. Each photon that strikes the SPAD generates a corresponding electrical signal, which is rectified into a square wave pulse signal, which is then counted by a counter and output as a pixel signal. In recent years, researchers have begun exploring the use of SPADs as pixel sensors in CISs, replacing PPDs in conventional visible light RGB cameras. This approach leverages the SPAD's ultra-high single-photon sensitivity and enables imaging capabilities that surpass the human eye in polar night scenes.

[0005] However, existing SPAD-based CISs have the problem shown in Figure 1. In low-light environments, due to the low number of photons in the environment, the sensed photons can be accurately recorded. In high-light environments, due to the large number of photons in the environment, a large number of photons sequentially incident on the SPAD pixel generate a continuous square wave signal, resulting in the number of incident photons being far greater than the count of the counter within the pixel. When capturing images with complex light and shadow changes, the counter counts output by some pixels in the low-light area and the counter counts output by some pixels in the high-light area are the same or similar, resulting in the back-end image processing software being unable to accurately distinguish between high-light pixels and low-light pixels, which in turn affects the image capture effect.

[0006] Summary of the Invention

[0007] The purpose of the embodiments of the present application is to provide a photosensitive pixel circuit, an image sensor, and an electronic device that can solve the problem that the existing SPAD-based CIS cannot accurately sense light.

[0008] In a first aspect, an embodiment of the present application provides a photosensitive pixel circuit, comprising: a switch element, a single-photon avalanche transistor, a sensitivity adjustment module, and a counting module;

[0009] The first end of the switch element is used to connect to a first voltage, the second end of the switch element is used to receive a switch control signal, the third end of the switch element is connected to the first end of the single-photon avalanche transistor, and the second end of the single-photon avalanche transistor is used to connect to a second voltage, and the second voltage is less than the first voltage;

[0010] The first input end of the sensitivity adjustment module is connected to the first end of the single-photon avalanche transistor to obtain an initial light sensing signal when the switch control signal controls the switch element to be disconnected. The second input end of the sensitivity adjustment module is used to receive the sensitivity control signal. The output end of the sensitivity adjustment module is connected to the input end of the counting module. The output end of the counting module is used to output the pixel light sensing signal.

[0011] The sensitivity control signal is used to control the sensitivity adjustment module to switch between a first working state and a second working state; the photosensitive pixel circuit has a first light sensitivity when the sensitivity adjustment module is in the first working state, and the photosensitive pixel circuit has a second light sensitivity when the sensitivity adjustment module is in the second working state, and the first light sensitivity is greater than the second light sensitivity.

[0012] In a second aspect, an embodiment of the present application provides an image sensor comprising the photosensitive pixel circuit described in the first aspect.

[0013] In a third aspect, an embodiment of the present application provides an electronic device comprising the image sensor described in the second aspect.

[0014] In an embodiment of the present application, a photosensitive pixel circuit includes: a switching element, a single-photon avalanche transistor, a sensitivity adjustment module, and a counting module; wherein the first end of the switching element is used to connect to a first voltage, the second end of the switching element is used to receive a switching control signal, the third end of the switching element is connected to the first end of the single-photon avalanche transistor, and the second end of the single-photon avalanche transistor is used to connect to a second voltage, and the second voltage is less than the first voltage; the first input end of the sensitivity adjustment module is connected to the first end of the single-photon avalanche transistor to obtain an initial light sensing signal when the switching element is disconnected by the switching control signal, the second input end of the sensitivity adjustment module is used to receive a sensitivity control signal, the output end of the sensitivity adjustment module is connected to the input end of the counting module, and the output end of the counting module is used to output a pixel light sensing signal; the sensitivity control signal is used to control the sensitivity adjustment module to switch between a first working state and a second working state; the photosensitive pixel circuit has a first light sensitivity when the sensitivity adjustment module is in the first working state, and has a second light sensitivity when the sensitivity adjustment module is in the second working state, and the first light sensitivity is greater than the second light sensitivity. In this way, by adding a sensitivity adjustment module that can control the working state through a sensitivity control signal to the photosensitive pixel circuit based on the single-photon avalanche transistor, the light sensitivity of the photosensitive pixel circuit can be adjusted. In actual applications, the working state of the sensitivity control signal can be controlled according to the number of photons incident in the actual environment to adjust the light sensitivity, thereby ensuring that the photosensitive pixel circuit can accurately identify high-light pixels and low-light pixels, thereby improving the image capture effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG1 is a schematic diagram of the photosensitivity principle and counting of a CIS chip based on a SPAD in the prior art;

[0016] FIG2 is a circuit diagram and a working principle diagram of a SPAD-based CIS chip in the prior art;

[0017] FIG3 is a circuit structure diagram of a photosensitive pixel circuit provided in an embodiment of the present application;

[0018] FIG4 is one of the specific circuit structure diagrams of the photosensitive pixel circuit provided in an embodiment of the present application;

[0019] FIG5 a is a diagram showing the light-sensing working principle of the light-sensing pixel circuit shown in FIG4 in a low-light environment, provided by an embodiment of the present application;

[0020] FIG5 b is a diagram showing the light-sensing working principle of the light-sensing pixel circuit shown in FIG4 under a high-light environment, provided by an embodiment of the present application;

[0021] FIG6 is a second specific circuit structure diagram of the photosensitive pixel circuit provided in an embodiment of the present application;

[0022] FIG7 is a diagram showing the light-sensing working principle of the light-sensing pixel circuit shown in FIG6 under a high-light environment provided by an embodiment of the present application;

[0023] FIG8 is a hardware structure diagram of an image sensor provided in an embodiment of the present application;

[0024] FIG9 is a hardware structure diagram of the electronic device provided in an embodiment of the present application. Specific embodiments

[0025] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0026] The terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than that illustrated or described herein, and that the objects distinguished by "first," "second," and the like are generally of the same type, and do not limit the number of objects; for example, the first object can be one or more. In addition, the term "and / or" in the specification and claims refers to at least one of the connected objects, and the character " / " generally indicates that the objects connected are in an "or" relationship.

[0027] To make the embodiments of the present application clearer, the following first introduces the relevant background technology knowledge involved in the embodiments of the present application:

[0028] At present, single-photon avalanche transistors (SPADs) are widely used in direct time-of-flight (dToF) image sensor CIS chips. The main pixel circuit structure and working principle are shown in Figure 2.

[0029] Among them, there is no structural difference between SPAD and PPD used in conventional CIS pixels, except that the higher bias voltage (VDD-VSS) causes the PPD to operate in the avalanche region. Compared with PPD, SPAD has extremely high sensitivity. Each photon (Photon) shining on the SPAD will stimulate a corresponding electrical signal. In the typical SPAD pixel structure shown in Figure 2, the SPAD generates a pulse signal Vc when it receives a photon, which is rectified by an inverter (NOT gate) to form a square wave pulse signal Vp; the PMOS transistor switch connected to the power supply voltage VDD is equivalent to a variable resistor, which mainly controls the size of the pulse signal flowing through the SPAD to prevent the Vc signal from being too large or too small; the Vp signal is connected to a counter (Counter). In theory, the counter will count once for each photon received by the SPAD. If N photons reach the SPAD, the counter will count N times.

[0030] Among various CIS types, SPADs are currently primarily used in dToF CIS products, serving as the receiving-side chip for infrared / near-infrared 3D depth-sensing cameras. In recent years, researchers have begun exploring the use of SPADs as a replacement for PPDs as pixel sensors in standard visible light RGB (RGB) CIS cameras. Due to their ultra-high sensitivity, reaching single-photon sensing levels, SPAD-based CIS chips possess imaging capabilities exceeding those of the human eye in polar night scenes.

[0031] Due to the ultra-high sensitivity of SPAD, i.e. single-photon response, problems such as those shown in Figure 1 may arise when it is used as a photosensor in traditional CIS:

[0032] In low-light environments, such as those with an illumination of less than 10 lux, the number of photons in the environment is relatively small, so the SPAD-based CMOS single-photon image sensor pixel can accurately record the sensed photons. For example, when three photons sequentially strike a SPAD pixel, three square wave signals are generated, and the counter within the pixel counts three times. At this point, the number of photons received by the sensor pixel equals the count of the pixel counter. In high-light environments, such as those with an illumination of more than 500 lux, the number of photons in the environment is very large, so the SPAD-based CMOS single-photon image sensor pixel cannot accurately record the number of sensed photons. The main reason is that when a large number of photons sequentially strike the SPAD pixel, a continuous square wave signal is generated, and the pixel counter only counts the number of square waves. Therefore, in this case, the number of incident photons is much greater than the count of the pixel counter. Therefore, when a SPAD-based CMOS single-photon image sensor captures an image with complex light and shadow variations, such as highlights and shadows, the problem shown on the right side of Figure 1 occurs: the counter counts of some pixels in low-light areas and some pixels in high-light areas are the same. This problem prevents the back-end image processing software from distinguishing which pixels are sensing high light and which are sensing low light, resulting in photosensitive imaging errors.

[0033] This embodiment of the application addresses the problem of pixel counting errors, also known as oversaturation errors, that occur in SPAD-based CMOS single-photon image sensors under high light conditions. By adjusting the pixel sensitivity, this solution addresses the problem of pixel counting errors in SPAD-based CMOS single-photon image sensors under high light conditions, enabling the CMOS single-photon image sensor to accurately sense light in both low-light and high-light environments.

[0034] The photosensitive pixel circuit, image sensor, and electronic device provided in the embodiments of the present application are described in detail below with reference to specific embodiments and their application scenarios in conjunction with the accompanying drawings.

[0035] Please refer to FIG3 , which is a circuit structure diagram of a photosensitive pixel circuit provided in an embodiment of the present application. As shown in FIG3 , the photosensitive pixel circuit includes a switch element, a single photon avalanche transistor (SPAD), a sensitivity adjustment module, and a counting module.

[0036] The first end of the switch element is used to connect to a first voltage, the second end of the switch element is used to access a switch control signal, the third end of the switch element is connected to the first end of the single-photon avalanche transistor SPAD, and the second end of the single-photon avalanche transistor SPAD is used to connect to a second voltage, and the second voltage is less than the first voltage;

[0037] The first input end of the sensitivity adjustment module is connected to the first end of the single-photon avalanche transistor SPAD to obtain an initial light sensing signal when the switch control signal controls the switch element to be disconnected. The second input end of the sensitivity adjustment module is used to receive the sensitivity control signal. The output end of the sensitivity adjustment module is connected to the input end of the counting module. The output end of the counting module is used to output the pixel light sensing signal.

[0038] The sensitivity control signal is used to control the sensitivity adjustment module to switch between a first working state and a second working state; the photosensitive pixel circuit has a first light sensitivity when the sensitivity adjustment module is in the first working state, and the photosensitive pixel circuit has a second light sensitivity when the sensitivity adjustment module is in the second working state, and the first light sensitivity is greater than the second light sensitivity.

[0039] In an embodiment of the present application, in order to enable a photosensitive pixel circuit based on a single-photon avalanche transistor (SPAD) to accurately count the number of incident photons in a high-light environment without causing the problem of the count in a high-light environment being the same as the count in a low-light environment, a sensitivity adjustment module (Sensitivity Adjustment Block) is added on the basis of the existing SPAD pixel architecture. This module is located between the SPAD device output signal and the digital counter module; and the sensitivity adjustment module can switch the working state under the action of an external control signal, i.e., a sensitivity control signal, to adjust the light sensitivity. For example, the sensitivity adjustment module can be in a first working state in a high-light environment to reduce the light sensitivity, and can be in a second working state in a low-light environment to increase the light sensitivity or maintain high light sensitivity, thereby following the number of incident photons and outputting a corresponding number of square wave signals, ensuring that the counting module counts the number of incident photons more accurately, thereby ensuring that the back-end image processing software can accurately identify high-light pixels and low-light pixels and correctly perform photosensitivity imaging.

[0040] Specifically, as shown in FIG3 , the SPAD-based photosensitive pixel circuit proposed in the embodiment of the present application includes a switching element, a single photon avalanche transistor SPAD, a sensitivity adjustment module and a counting module.

[0041] Among them, the switching element can be implemented by a MOS tube, for example, it can be PMOS or NMOS. When PMOS is selected, the source of PMOS is connected to the first voltage, which can be the power supply voltage VDD, the drain is connected to the cathode of SPAD, and the gate is connected to the switch control signal φEXPO; when NMOS is selected, the drain of NMOS is connected to the first voltage, that is, the power supply voltage VDD, the source is connected to the cathode of SPAD, and the gate is connected to the switch control signal φEXPO; the anode of the SPAD can be connected to the second voltage, which can be grounded or connected to the negative voltage VSS.

[0042] The switching element can be in an off or on state under the control of the switching control signal. The single-photon avalanche transistor SPAD performs light sensing when the switching element is off, generates an initial light sensing signal Vc, and inputs it into the sensitivity adjustment module, and is reset when the switching element is on. That is to say, the switching control signal can be used to control the light sensing time. When light sensing is required, the switching control signal output is a voltage signal that disconnects the switching element. When light sensing is not required or is completed, the switching control signal output is a voltage signal that turns on the switching element.

[0043] The sensitivity adjustment module is located between the output signal of the SPAD and the counting module. Its first input end is connected to the anode of the SPAD, the second input end is connected to the sensitivity control signal φSEN, and the output end is connected to the input end of the counting module. The output end of the counting module outputs a counting signal, or a pixel sensitivity signal. The counting module can be a digital counter.

[0044] During light exposure, the anode of the SPAD outputs an initial light sensing signal Vc, which is a pulse voltage signal. The sensitivity adjustment module is used to shape or compare the initial light sensing signal Vc and output a second light sensing signal Vb. The second light sensing signal Vb is a pulse signal, such as a square wave signal, and can switch the working state under the control of the sensitivity control signal φSEN. The light-sensitive pixel circuit has different light sensitivities under different working states of the sensitivity adjustment module. Accordingly, the number of square wave signals output by the sensitivity adjustment module per unit light-sensitive time under different working states is different. That is to say, the sensitivity adjustment module can adjust the light sensitivity of the light-sensitive pixel circuit under the control of the sensitivity control signal φSEN. The counter is used to count the number of square waves output by the sensitivity adjustment module and output a counting signal. The counting signal can be converted into a pixel light-sensitive signal through a readout circuit.

[0045] Specifically, the sensitivity control signal φSEN can also be called a pixel sensitivity adjustment signal. This signal can be a 1-bit or N-bit digital signal or an analog signal. This signal enters the sensitivity adjustment module together with the initial light sensing signal Vc output by the SPAD device.

[0046] When the switch element is turned off by the switch control signal φEXPO, the SPAD is exposed / sensing light. At this point, by changing / adjusting the sensitivity control signal φSEN, the light sensitivity of the SPAD pixel can be altered, and the counting speed of the counting module can be changed accordingly. In actual applications, the sensitivity control signal φSEN can be changed / adjusted based on the ambient light brightness to ensure that the operating state of the sensitivity adjustment module matches the ambient light brightness, so that the number of square wave signals output by the sensitivity adjustment module per unit exposure time and the counts of the counting module match the number of photons incident in the actual environment.

[0047] In actual applications, the switch control signal φEXPO and the sensitivity control signal φSEN can be output through an external controller, and the controller outputs appropriate switch control signal φEXPO and sensitivity control signal φSEN to the photosensitive pixel circuit to control the photosensitive pixel circuit to perform photosensitivity, and can adjust the parameters of the sensitivity control signal φSEN, such as signal size or signal frequency, according to the ambient light brightness to control the light sensitivity of the photosensitive pixel circuit.

[0048] Through this design, the light sensitivity of the SPAD pixel can be effectively adjusted. By adjusting the pixel sensitivity, the photosensitive pixel circuit can output the correct pixel photosensitive signal under different lighting environments.

[0049] Optionally, when the switch control signal controls the switch element to be disconnected, the sensitivity adjustment module generates a second light sensing signal based on the initial light sensing signal and the sensitivity control signal, and the counting module generates the pixel light sensing signal based on the second light sensing signal and outputs it through the output end of the counting module.

[0050] Specifically, when the switching element is a PMOS tube as shown in Figure 3, the switching control signal φEXPO can be a high-level signal to control the PMOS tube to be in an off state, and the SPAD generates an initial light sensing signal Vc under the irradiation of photons; or, when the switching element is an NMOS tube, the switching control signal φEXPO can be a low-level signal to control the PMOS tube to be in an off state, and the SPAD generates an initial light sensing signal Vc under the irradiation of photons.

[0051] The sensitivity adjustment module obtains the initial light sensing signal Vc generated by the SPAD and generates a second light sensing signal Vb under the influence of the sensitivity control signal. Specifically, the initial light sensing signal Vc input to the sensitivity adjustment module can adjust the number of square waves in the output second light sensing signal Vb under the interference of the sensitivity control signal. The counting module generates a pixel light sensing signal based on the second light sensing signal Vb. Specifically, the pixel light sensing signal can be generated by counting the square waves of the second light sensing signal Vb. That is, the pixel light sensing signal can be a count signal, which is ultimately output through the output terminal of the counting module.

[0052] In this embodiment, the sensitivity adjustment module can generate a second light sensing signal based on the initial light sensing signal and the sensitivity control signal generated by the SPAD, and then output the pixel light sensing signal through the counting module to implement the light sensing control logic.

[0053] Optionally, the sensitivity control signal is a pulse signal, and the frequency of the sensitivity control signal is changed to control the sensitivity adjustment module to switch between the first working state and the second working state.

[0054] In one embodiment, the sensitivity control signal φSEN may be a pulse signal, and the operating state of the sensitivity adjustment module can be switched by varying the frequency of the pulse signal. Specifically, different pulse signal frequencies result in different numbers of pulses within the same time period. By superimposing the pulse signal with the initial light sensing signal Vc, the number of square waves in the second light sensing signal Vb output by the sensitivity adjustment module can be varied, thereby switching the operating state of the sensitivity adjustment module.

[0055] For example, as shown in Figures 5a and 5b, the sensitivity control signal φSEN is a pulse signal, and the frequency of the pulse signal in Figure 5a is lower than the frequency of the pulse signal in Figure 5b. When the frequency of the pulse signal changes, the number of square waves of the second light sensing signal Vb output by the sensitivity adjustment module within the same time period also changes accordingly.

[0056] In actual applications, the sensitivity control signal φSEN can be frequency-adjusted by an external controller according to the ambient light brightness, so that the working state of the sensitivity adjustment module and the light sensitivity of the photosensitive pixel circuit match the actual lighting environment. Specifically, in a high-light environment, for example, when the ambient light brightness is higher than the preset brightness threshold, the frequency of the sensitivity control signal φSEN can be increased so that the number of pulses it outputs is larger, thereby adjusting the original continuous square wave signal output to multiple square wave signal outputs, thereby increasing the count of the number of incident photons; in a low-light environment, for example, when the ambient light brightness is lower than the preset brightness threshold, the frequency of the sensitivity control signal φSEN can be lowered to maintain the number of square wave signals originally output and maintain a normal count of the number of incident photons.

[0057] Among them, the preset brightness threshold can be a threshold for defining low-light environment and high-light environment, such as 200Lux, that is, above the threshold it is a high-light environment, and below it is a low-light environment; it can also be a threshold for defining high-light environment and non-high-light environment, such as 500Lux, that is, above the threshold it is a high-light environment, and below the threshold it is not a high-light environment. The threshold for distinguishing different levels of lighting environments can also be set according to actual needs.

[0058] It should be noted that in this embodiment, under high-light conditions, the number of incident photons is large and highly coherent. As shown in Figures 1 and 2, the output signal Vp of the NOT gate will remain continuously at a high level when continuous photons enter the SPAD device. At this time, by increasing the frequency of the sensitivity control signal φSEN, the number of square waves of the second light sensing signal Vb output by the sensitivity adjustment module per unit light-sensing time can be increased, and the counting module will also count faster, thereby recording more photons. In this case, appropriately reducing the frequency of the sensitivity control signal φSEN can effectively slow down the counting speed of the counting module, thereby reducing the sensitivity of the SPAD pixel in strong light and preventing the SPAD pixel from being quickly overexposed in strong light.

[0059] However, it should be noted that in high-light environments, the frequency of the sensitivity control signal φSEN cannot drop too much. A safe frequency threshold fTHR must be set to ensure that the frequency of the sensitivity control signal φSEN is always greater than fTHR. The reason is that the SPAD pixel must maintain a certain sensitivity to sense and count a certain number of incident photons to prevent the output signal difference between strong light and weak light environments from being too small, resulting in a narrowing of the dynamic range.

[0060] In this embodiment, the sensitivity of the SPAD pixel is adjusted by a pulse digital signal φSEN. By changing the frequency of this signal, similar to pulse frequency modulation (PFM), the sensitivity is adjusted. The adjustment principle is simple and highly operable.

[0061] Optionally, the sensitivity adjustment module includes a NOT gate and an AND gate;

[0062] The input end of the NOT gate is connected to the first end of the single-photon avalanche transistor SPAD, the output end of the NOT gate is connected to the first input end of the AND gate, the second input end of the AND gate is used to access the sensitivity control signal, and the output end of the AND gate is connected to the output end of the sensitivity adjustment module.

[0063] As shown in Figure 4, in one embodiment, the sensitivity adjustment module can be composed of a NOT gate and an AND gate. The NOT gate's input is connected to the output signal of the SPAD device, i.e., the initial light sensing signal Vc. The NOT gate inverts the initial light sensing signal Vc and outputs a first light sensing signal Vp, which is a square wave pulse signal. The AND gate's input signals are the first light sensing signal Vp and the sensitivity control signal φSEN. The AND gate performs an AND operation on the first light sensing signal Vp and the sensitivity control signal φSEN and outputs a second light sensing signal Vb, which is also a square wave pulse signal.

[0064] In some embodiments, the sensitivity control signal φSEN can be a pulse signal, such as a 1-bit binary digital signal, that is, only two signals, 1 and 0; the second light sensing signal Vb is also a 1-bit digital signal; the counting module can be an N-bit digital counter; thus, the second light sensing signal Vb is transmitted to the N-bit digital counter for counting, and the maximum count of the counter is an N-bit binary digit, that is, N 1s.

[0065] In this embodiment, the pixel sensitivity adjustment module is a purely digital circuit design and is placed in the SPAD pixel circuit processing chain. It is independent of the SPAD device process, optical structure, and working principle, and will not affect the operation of other pixel modules. The light sensitivity can be controlled by simply adjusting the frequency of the sensitivity control signal φSEN, and the adjustment method is simple.

[0066] Furthermore, when the sensitivity control signal is a first pulse signal, the sensitivity adjustment module is in the first working state; when the sensitivity control signal is a second pulse signal, the sensitivity adjustment module is in the second working state; the pulse frequency of the first pulse signal is lower than the pulse frequency of the second pulse signal.

[0067] In some embodiments, for the photosensitive pixel circuit design shown in FIG4 , the sensitivity control signal φSEN may be a periodic pulse signal, and the sensitivity adjustment module may be controlled to be in different working states by adjusting the frequency of the pulse signal.

[0068] Specifically, when the sensitivity control signal φSEN is a first pulse signal with a lower frequency, the sensitivity adjustment module is in a first working state, and at this time the light sensitivity of the photosensitive pixel circuit is higher; when the sensitivity control signal φSEN is a second pulse signal with a higher frequency, the sensitivity adjustment module is in a second working state, and at this time the light sensitivity of the photosensitive pixel circuit is lower.

[0069] For example, in a first lighting environment, the sensitivity control signal φSEN can be adjusted to a first pulse signal of a first frequency, thereby controlling the sensitivity adjustment module to be in a first working state; in a second lighting environment, the sensitivity control signal φSEN can be adjusted to a second pulse signal of a second frequency, thereby controlling the sensitivity adjustment module to be in a second working state; wherein, the lighting parameters of the first lighting environment can be smaller than the lighting parameters of the second lighting environment, the first frequency is lower than the second frequency, and the light sensitivity corresponding to the first working state is greater than the light sensitivity corresponding to the second working state, that is, in a relatively low lighting environment, the frequency of the sensitivity control signal φSEN can be lowered to obtain higher light sensitivity, and in a relatively high lighting environment, the frequency of the sensitivity control signal φSEN can be increased to reduce light sensitivity.

[0070] In this embodiment, the sensitivity adjustment of the SPAD pixel can be achieved by changing the frequency of the pulse signal, which is similar to the sensitivity adjustment achieved by pulse frequency modulation PFM. The adjustment principle is simple and highly operable.

[0071] Furthermore, when the sensitivity adjustment module is in the first working state, the number of pulses contained in the sensitivity control signal received by the sensitivity adjustment module per unit time is M; when the sensitivity adjustment module is in the second working state, the number of pulses contained in the sensitivity control signal received by the sensitivity adjustment module per unit time is N, where M and N are both positive integers, and M is less than N.

[0072] In other embodiments, for the photosensitive pixel circuit design shown in Figure 4, the sensitivity control signal φSEN can be a periodic pulse signal or a non-periodic pulse signal, and the sensitivity adjustment module can be controlled to be in different working states by adjusting the number of pulses of the pulse signal per unit time.

[0073] Specifically, when the number of pulses contained in the sensitivity control signal φSEN received by the sensitivity adjustment module within unit time is M, the sensitivity adjustment module is in a first working state, and at this time the light sensitivity of the photosensitive pixel circuit is high; when the number of pulses contained in the sensitivity control signal φSEN received by the sensitivity adjustment module within unit time is N, the sensitivity adjustment module is in a second working state, and at this time the light sensitivity of the photosensitive pixel circuit is low, wherein M is less than N.

[0074] For example, in a first lighting environment, the number of pulses of the sensitivity control signal φSEN per unit time can be adjusted to 100, thereby controlling the sensitivity adjustment module to be in a first working state; in a second lighting environment, the number of pulses of the sensitivity control signal φSEN per unit time can be adjusted to 200, thereby controlling the sensitivity adjustment module to be in a second working state; wherein, the lighting parameters of the first lighting environment can be smaller than the lighting parameters of the second lighting environment, and the light sensitivity corresponding to the first working state is greater than the light sensitivity corresponding to the second working state, that is, in a relatively low lighting environment, the number of pulses of the sensitivity control signal φSEN per unit time can be reduced to obtain higher light sensitivity, and in a relatively high lighting environment, the number of pulses of the sensitivity control signal φSEN per unit time can be increased to reduce light sensitivity.

[0075] In this embodiment, the sensitivity adjustment of the SPAD pixel can be achieved by changing the number of pulses per unit time of the pulse signal. The adjustment principle is simple and highly operable.

[0076] Optionally, when the switch control signal controls the switch element to be disconnected and the sensitivity control signal is a continuous high-level signal, the sensitivity adjustment module is in the first working state;

[0077] When the switch control signal controls the switch element to be turned off, and the sensitivity control signal is a pulse signal including a plurality of pulses, the sensitivity adjustment module is in the second working state.

[0078] In one embodiment, the sensitivity control signal φSEN can be a continuously high-level signal during the light-sensing time, thereby placing the sensitivity adjustment module in a first operating state. This first operating state can be the operating state corresponding to the highest light sensitivity. For example, when the ambient light brightness is below a preset brightness threshold, i.e., in a low-light environment, the sensitivity control signal φSEN can be adjusted to a continuously high-level signal, such as a digital 1 signal, so that the number of square waves in the second light sensing signal Vb output by the AND gate is consistent with the number of square waves in the first light sensing signal Vp output by the NOT gate. In other words, the number of incident photons is relatively low, and there is no need to reduce light sensitivity, so that the highest light sensitivity can be maintained.

[0079] The principle for adjusting the photosensitivity of the SPAD pixel in this case can be shown in Figure 5a. When in a low-light environment, the number of photons received by the SPAD pixel is relatively small. At this point, the photosensitivity of the SPAD pixel needs to be adjusted to a high-sensitivity stage. Specifically, within a unit exposure time, such as the period when the switch control signal φEXPO is pulled low, the frequency of the sensitivity control signal φSEN needs to be adjusted as low as possible to achieve high sensitivity. In the case shown in Figure 5a, the frequency of the sensitivity control signal φSEN is at its lowest, meaning it remains high throughout the exposure time. At this point, each incident photon stimulates a pulse wave of the initial photosensor signal Vc and causes the first photosensor signal Vp to generate a corresponding square wave. At the output of the AND gate, the second photosensor signal Vb corresponds to the first photosensor signal Vp. At this point, the count recorded by the counting module is the number of incident photons.

[0080] In this embodiment, the sensitivity control signal φSEN can also be a pulse signal containing multiple pulses within the light-sensing time, so as to place the sensitivity adjustment module in a second operating state, and this second operating state can be an operating state corresponding to lower light sensitivity. For example, when the ambient light brightness is higher than the preset light parameter threshold, i.e., in a high-light environment, the sensitivity control signal φSEN can be adjusted to a signal that alternates between a low level and a high level. The frequency of the sensitivity control signal φSEN or the number of pulses per unit time can also be adjusted. In this case, the number of pulses per unit time of the sensitivity control signal φSEN directly determines the number or frequency of square wave signals output by the AND gate within the light-sensing time, as well as the counting frequency of the digital counter.

[0081] The principle for adjusting the sensitivity of the SPAD pixel in this case is shown in Figure 5b. When exposed to high light levels, the number of photons received by the SPAD pixel is very high, necessitating a reduction in its sensitivity. This can be achieved by changing the frequency of the sensitivity control signal φSEN. As shown in Figure 5b, in high light levels, the number of incident photons is high and consistent. The output signal of the NOT gate, the first light sensing signal Vp, will remain continuously high when continuous photons strike the SPAD device. The frequency of the sensitivity control signal φSEN directly determines the frequency of the square wave signal output by the AND gate and the counting frequency of the digital counter. The higher the frequency of the sensitivity control signal φSEN, the greater the number of square waves in the first light sensing signal Vb output by the AND gate, and the faster the digital counter counts, thereby recording a greater number of photons. In this case, appropriately reducing the frequency of the sensitivity control signal φSEN can effectively slow the counter's counting speed, thereby reducing the sensitivity of the SPAD pixel in strong light and preventing rapid overexposure of the SPAD pixel in such conditions.

[0082] It should be noted that in high-light environments, the frequency of the sensitivity control signal φSEN cannot drop too much. A safe frequency threshold fTHR must be set to ensure that the frequency of the sensitivity control signal φSEN is always greater than fTHR. The reason is that the SPAD pixel must maintain a certain sensitivity to sense and count a certain number of incident photons to prevent the output signal difference between strong light and weak light environments from being too small, resulting in a narrowing of the dynamic range.

[0083] The embodiment shown in Figure 4 has the following advantages: the SPAD-based photosensitive pixel circuit can adjust the pixel sensitivity to capture images under different lighting conditions, and no obvious counting errors will occur when shooting under high lighting conditions; the pixel sensitivity adjustment module is a purely digital circuit design and is placed in the SPAD pixel circuit processing chain. It is independent of the SPAD device process, optical structure, and working principle, and will not affect the operation of other pixel modules; the sensitivity adjustment of the SPAD pixel is performed through a single digital signal φSEN, and the sensitivity adjustment is achieved by changing the frequency of this digital signal, similar to pulse frequency modulation (PFM). The adjustment principle is simple and highly operational.

[0084] Optionally, the sensitivity adjustment module generates a second light sensing signal according to the initial light sensing signal and the sensitivity control signal; and the counting module records the number of pulses in the second light sensing signal to generate the pixel light sensing signal.

[0085] Specifically, the photosensitive pixel circuit begins to sense light when the switch element is in the off state. The SPAD generates an initial light sensing signal Vc under the irradiation of photons. The sensitivity adjustment module obtains the initial light sensing signal Vc generated by the SPAD and generates a second light sensing signal Vb by performing an operation on the signal and the sensitivity control signal φSEN. Specifically, the initial light sensing signal Vc first undergoes a negation operation of a NOT gate to output a first light sensing signal Vp, which is then ANDed with the sensitivity control signal φSEN to output a second light sensing signal Vb, which is a pulse signal. The counting module generates the pixel light sensing signal by counting the number of pulses in the second light sensing signal Vb.

[0086] In this embodiment, the sensitivity adjustment module can generate a second light sensing signal based on the initial light sensing signal generated by the SPAD and the sensitivity control signal, and then output the pixel light sensing signal through the counting module to implement the light sensing control logic.

[0087] Optionally, when the ambient light brightness is lower than the brightness threshold, the sensitivity adjustment module is controlled to operate in the first working state by the sensitivity control signal; when the ambient light brightness is higher than the brightness threshold, the sensitivity adjustment module is controlled to operate in the second working state by the sensitivity control signal.

[0088] In actual applications, the sensitivity adjustment module can be controlled to operate in a corresponding working state through the sensitivity control signal according to the ambient light brightness, so that the photosensitive pixel circuit changes the light sensitivity according to the ambient light brightness, thereby ensuring that the output pixel photosensitive signal is accurate and can reflect the number of incident photons in the actual ambient light.

[0089] Specifically, in a low-light environment, such as when the ambient light brightness is lower than the brightness threshold, the sensitivity control signal can be used to control the sensitivity adjustment module to operate in the first working state to ensure higher light sensitivity; in a high-light environment, such as when the ambient light brightness is higher than the brightness threshold, the sensitivity control signal can be used to control the sensitivity adjustment module to operate in the second working state to appropriately reduce light sensitivity.

[0090] Among them, the brightness threshold can be a threshold for defining low-light environment and high-light environment, such as 200Lux, that is, above the threshold it is a high-light environment, and below the threshold it is a low-light environment. It can also be a threshold for defining high-light environment and non-high-light environment, such as 500Lux, that is, above the threshold it is a high-light environment, and below the threshold it is not a high-light environment. The threshold for distinguishing different levels of lighting environments can also be set according to actual needs.

[0091] Optionally, the sensitivity control signal is an analog signal, and the voltage of the sensitivity control signal is changed to control the sensitivity adjustment module to switch between the first working state and the second working state.

[0092] In another embodiment, the sensitivity control signal φSEN may be an analog signal, and the operating state of the sensitivity adjustment module may be switched by varying the voltage of the analog signal. Specifically, by varying the voltage of the analog signal, the number of square waves in the second light sensing signal Vb output by the sensitivity adjustment module may be varied by comparison with the initial light sensing signal Vc, thereby switching the operating state of the sensitivity adjustment module.

[0093] For example, as shown in FIG. 7 , the sensitivity control signal φSEN is an analog signal. When the voltage of the analog signal changes, the number of square waves of the second light sensing signal Vb output by the sensitivity adjustment module within the same time period also changes accordingly.

[0094] In practical applications, the sensitivity control signal φSEN can be adjusted by an external controller according to the ambient light brightness so that the sensitivity of the SAPD pixel matches the actual lighting environment. Specifically, in a high-light environment, for example, when the ambient light brightness is higher than a preset brightness threshold, the voltage of the sensitivity control signal φSEN can be adjusted to an appropriate value so that the comparator outputs a certain number of square wave signals; in a low-light environment, for example, when the ambient light brightness is lower than the preset brightness threshold, the voltage of the sensitivity control signal φSEN can be appropriately adjusted so that the comparator outputs a number of square wave signals consistent with the number of incident photons.

[0095] In this embodiment, the sensitivity of the SPAD pixel is adjusted by an analog voltage signal φSEN. The sensitivity is adjusted by changing the voltage of this signal. The adjustment principle is simple and highly operable.

[0096] Optionally, the sensitivity adjustment module includes a comparator;

[0097] The first input end of the comparator is connected to the first end of the single photon avalanche transistor SPAD, the second input end of the comparator is connected to the sensitivity control signal, and the output end of the comparator is connected to the output end of the sensitivity adjustment module.

[0098] As shown in Figure 6, in another embodiment, the sensitivity adjustment module can be implemented using a comparator (CMP) based on an operational amplifier (Operational Amplifier). The input signals of the comparator are the initial light sensing signal Vc output by the SPAD device and the sensitivity control signal φSEN. The comparator compares the initial light sensing signal Vc with the sensitivity control signal φSEN and outputs a second light sensing signal Vb.

[0099] In some embodiments, the sensitivity control signal φSEN can be an analog voltage signal, and the sensitivity of the SPAD pixel is adjusted by adjusting the voltage of the sensitivity control signal φSEN. When photons strike the SPAD device, the SPAD outputs an initial light-sensing signal Vc, the magnitude and frequency of which are determined by the number of incident photons.

[0100] In this embodiment, the pixel sensitivity adjustment module is designed as an analog circuit and is placed in the SPAD pixel circuit processing chain. It is independent of the SPAD device process, optical structure, and working principle, and will not affect the operation of other pixel modules. The light sensitivity can be controlled by simply adjusting the size of the sensitivity control signal φSEN, and the adjustment method is simple.

[0101] Optionally, the comparator is a non-inverting comparator, which reduces the voltage of the sensitivity control signal to enable the sensitivity adjustment module to operate in the first operating state; and increases the voltage of the sensitivity control signal to enable the sensitivity adjustment module to operate in the second operating state;

[0102] The comparator is an inverting comparator, which increases the voltage of the sensitivity control signal to make the sensitivity adjustment module work in the first working state; and reduces the voltage of the sensitivity control signal to make the sensitivity adjustment module work in the second working state.

[0103] In practical applications, the sensitivity control signal φSEN can be adjusted by an external controller according to the ambient light brightness so that the sensitivity of the SAPD pixel matches the actual lighting environment. Specifically, in a high-light environment, for example, when the ambient light brightness is higher than a preset brightness threshold, the voltage of the sensitivity control signal φSEN can be adjusted to an appropriate value so that the comparator outputs a certain number of square wave signals; in a low-light environment, for example, when the ambient light brightness is lower than the preset brightness threshold, the voltage of the sensitivity control signal φSEN can be appropriately adjusted so that the comparator outputs a number of square wave signals consistent with the number of incident photons.

[0104] In a specific implementation, the voltage of the sensitivity control signal φSEN can be adjusted according to the ambient light brightness in view of the working principle of the comparator, so as to adjust the sensitivity of the SPAD pixel to adapt to the actual lighting environment.

[0105] Specifically, the comparator is a non-inverting comparator. When the voltage of the initial light-sensing signal is greater than the voltage of the sensitivity control signal, the second light-sensing signal output by the comparator is a high level; when the voltage of the initial light-sensing signal is less than or equal to the voltage of the sensitivity control signal, the second light-sensing signal output by the comparator is a low level; the counting module generates the pixel light-sensing signal based on the second light-sensing signal.

[0106] Alternatively, the comparator is an inverting comparator, and when the voltage of the initial light-sensing signal is less than the voltage of the sensitivity control signal, the second light-sensing signal output by the comparator is a high level; when the voltage of the initial light-sensing signal is greater than or equal to the voltage of the sensitivity control signal, the second light-sensing signal output by the comparator is a low level; the counting module generates the pixel light-sensing signal based on the second light-sensing signal.

[0107] That is, in one case, the comparator is a non-inverting comparator, and its working mode is: when the initial light sensing signal Vc output by the SPAD is greater than or equal to the sensitivity control signal φSEN, the second light sensing signal Vb output by the comparator is pulled up to a high level; when the initial light sensing signal Vc is less than the sensitivity control signal φSEN, the second light sensing signal Vb output by the comparator is pulled down to a low level.

[0108] In this case, the sensitivity adjustment module can be controlled to operate in the first operating state by reducing the voltage of the sensitivity control signal φSEN to obtain higher light sensitivity; and the sensitivity adjustment module can be controlled to operate in the second operating state by increasing the voltage of the sensitivity control signal φSEN to reduce light sensitivity.

[0109] For example, when the ambient light brightness is lower than the preset brightness threshold, that is, in a low-light environment, the voltage of the sensitivity control signal φSEN can be adjusted as low as possible, but not lower than the minimum output voltage of the initial light sensing signal Vc, so that the number of square waves of the second light sensing signal Vb output by the comparator is consistent with the number of pulse waves of the initial light sensing signal Vc, that is, the number of incident photons is small at this time, and high sensitivity can be maintained.

[0110] When the ambient light brightness is higher than the preset brightness threshold, that is, in a high-light environment, the voltage of the sensitivity control signal φSEN can be increased. At this time, the voltage of the sensitivity control signal φSEN affects the frequency of the square wave signal output by the comparator and the counting frequency of the digital counter.

[0111] The principle of adjusting the SPAD pixel sensitivity in this case can be shown in Figure 7. In this case, when the initial light sensing signal Vc is greater than or equal to the sensitivity control signal φSEN, the comparator outputs the second light sensing signal Vb, which is pulled high. When the initial light sensing signal Vc is less than the sensitivity control signal φSEN, the comparator outputs the second light sensing signal Vb, which is pulled low. When the sensitivity control signal φSEN voltage is increased, the sensitivity of the SPAD pixel decreases, and vice versa. Therefore, the voltage of the sensitivity control signal φSEN can be appropriately increased, but kept within the maximum output voltage of the initial light sensing signal Vc, or even within the maximum pulse voltage of the initial light sensing signal Vc, to enable the comparator to output as many square wave signals as possible.

[0112] In another case, the working mode of the comparator is: when the initial light sensing signal Vc output by the SPAD is less than the sensitivity control signal φSEN, the second light sensing signal Vb output by the comparator is pulled up to a high level; when the initial light sensing signal Vc is greater than or equal to the sensitivity control signal φSEN, the second light sensing signal Vb output by the comparator is pulled down to a low level.

[0113] In this case, the sensitivity adjustment module can be controlled to operate in the first operating state by increasing the voltage of the sensitivity control signal φSEN to obtain higher light sensitivity; and the sensitivity adjustment module can be controlled to operate in the second operating state by reducing the voltage of the sensitivity control signal φSEN to reduce light sensitivity.

[0114] For example, when the ambient light brightness is lower than the preset brightness threshold, that is, in a low-light environment, the voltage of the sensitivity control signal φSEN can be increased as much as possible, but not higher than the maximum output voltage of the initial light sensing signal Vc, so that the number of square waves of the second light sensing signal Vb output by the comparator is consistent with the number of pulse waves of the initial light sensing signal Vc. That is, the number of incident photons is small at this time, and high sensitivity can be maintained.

[0115] When the ambient light brightness is higher than the preset brightness threshold, that is, in a high-light environment, the voltage of the sensitivity control signal φSEN can be lowered. At this time, the voltage of the sensitivity control signal φSEN affects the frequency of the square wave signal output by the comparator and the counting frequency of the digital counter.

[0116] Specifically, when the sensitivity control signal φSEN increases, the sensitivity of the SPAD pixel increases, and vice versa. Therefore, the voltage of the sensitivity control signal φSEN can be appropriately lowered to be no higher than the maximum pulse voltage of the initial light sensing signal Vc and no lower than the minimum output voltage of the initial light sensing signal Vc, allowing the comparator to output as many square wave signals as possible.

[0117] Similar to the implementation shown in Figure 4, in a high-light environment, the sensitivity control signal φSEN voltage needs to set a safety voltage threshold VTHR to ensure that the size adjustment range of the sensitivity control signal φSEN is always within VTHR, that is, it does not exceed VTHR. The reason is that the SPAD pixel must ensure a certain sensitivity to sense and count a certain number of incident photons to prevent the output signal difference between strong light and low light environments from being too small, resulting in a narrowing of the dynamic range.

[0118] The embodiment shown in Figure 6 has the following advantages: the photosensitive pixel circuit based on the SPAD pixel can adjust the pixel sensitivity to capture images under different lighting conditions, and no obvious counting errors will occur when taking pictures under high lighting conditions; the pixel sensitivity adjustment module is designed as an analog circuit and placed in the SPAD pixel circuit processing chain. It is independent of the SPAD device process, optical structure, and working principle, and will not affect the operation of other pixel modules; the sensitivity adjustment of the SPAD pixel is performed through a single analog signal φSEN, and the sensitivity adjustment is achieved by changing the voltage of this analog signal. The adjustment principle is simple and highly operational.

[0119] The photosensitive pixel circuit in the embodiment of the present application includes: a switching element, a single-photon avalanche transistor, a sensitivity adjustment module and a counting module; wherein the first end of the switching element is used to connect to a first voltage, the second end of the switching element is used to receive a switching control signal, the third end of the switching element is connected to the first end of the single-photon avalanche transistor, and the second end of the single-photon avalanche transistor is used to connect to a second voltage, and the second voltage is less than the first voltage; the first input end of the sensitivity adjustment module is connected to the first end of the single-photon avalanche transistor to obtain an initial light sensing signal when the switching element is disconnected by the switching control signal, the second input end of the sensitivity adjustment module is used to receive a sensitivity control signal, the output end of the sensitivity adjustment module is connected to the input end of the counting module, and the output end of the counting module is used to output a pixel light sensing signal; the sensitivity control signal is used to control the sensitivity adjustment module to switch between a first working state and a second working state; the photosensitive pixel circuit has a first light sensitivity when the sensitivity adjustment module is in the first working state, and has a second light sensitivity when the sensitivity adjustment module is in the second working state, and the first light sensitivity is greater than the second light sensitivity. In this way, by adding a sensitivity adjustment module that can control the working state through a sensitivity control signal to the photosensitive pixel circuit based on the single-photon avalanche transistor, the light sensitivity of the photosensitive pixel circuit can be adjusted. In actual applications, the working state of the sensitivity control signal can be controlled according to the number of photons incident in the actual environment to adjust the light sensitivity, thereby ensuring that the photosensitive pixel circuit can accurately identify high-light pixels and low-light pixels, thereby improving the image capture effect.

[0120] Please refer to Figure 8. An embodiment of the present application also provides an image sensor, including the photosensitive pixel circuit introduced in the above embodiment.

[0121] Optionally, as shown in FIG8 , the image sensor includes a plurality of the photosensitive pixel circuits, and the plurality of the photosensitive pixel circuits are arranged in an array;

[0122] The image sensor further includes a controller, which is used to generate the sensitivity control signal. The controller is connected to the second input end of the sensitivity adjustment module of the plurality of photosensitive pixel circuits.

[0123] As shown in Figure 8, the plurality of photosensitive pixel circuit arrays in the image sensor are arranged to form a SPAD pixel array. The controller in the image sensor includes a row controller and a column controller, and the image sensor may further include a readout circuit and a port circuit. The pixel array composed of SPAD pixels is controlled by the row and column controllers to perform photosensitivity, photoelectric conversion and signal output. The signal output by the pixel is read by the readout circuit and output to the outside of the chip via the port circuit. Figure 8 also shows a design case of a photosensitive pixel circuit, namely a SPAD pixel structure. Each pixel includes a controller (Controller), an 11-bit digital counter (11-bit Digital Counter), a SPAD device, a sensitivity adjustment module, and a readout circuit (Readout). When the excitation signal reaches the controller, the controller controls the SPAD to perform photoelectric conversion and the digital counter counts. The counting result is read by the readout circuit and output as a pixel output signal.

[0124] The light sensitivity of a SPAD pixel is controlled by a sensitivity control signal, φSEN. When this signal controls the sensitivity adjustment module to operate in a first state, the pixel enters a high-sensitivity mode; when this signal controls the sensitivity adjustment module to operate in a second state, the pixel enters a low-sensitivity mode. The sensitivity control signal for all pixels in the pixel array is the same. This signal, generated by user settings, is transmitted to the chip and distributed to each pixel by the column and row controllers. The output pixel light-sensing signal (output) is processed by the readout circuit module and converted to analog-to-digital. It is then processed by the image signal processing (ISP) module and output to the chip via the port circuit (I / O).

[0125] It should be noted that this embodiment is an implementation of the image sensor corresponding to the embodiment shown in Figure 3. Its specific implementation can refer to the relevant introduction in the aforementioned embodiments, and can achieve the same technical effects. To avoid repetition, it will not be described here.

[0126] Please refer to FIG9 . An embodiment of the present application further provides an electronic device, including the image sensor introduced in the embodiment shown in FIG8 .

[0127] Furthermore, the electronic device includes N compact camera modules (CCMs), each of which is provided with an image sensor; each of the image sensors is connected to an image signal processing (ISP) module in a central processing unit.

[0128] As a photosensitive component, the image sensor (CIS) chip is a core component of the compression camera module (CCM). The system architecture of a typical mobile communication device, currently represented by a mobile phone, is shown in Figure 9. N CCM modules can be configured, each equipped with a CIS chip. Each CIS chip communicates bidirectionally with a central processing unit (CPU), such as an application processor (AP) or an ISP module in a system-on-chip (SoC), via a port link. The AP / SoC sends control signals to the CIS chip in each CCM. The CIS generates image signals, which are then transmitted back to the ISP module for back-end processing.

[0129] It should be noted that this embodiment is an implementation of the electronic device corresponding to the embodiment shown in Figure 3. Its specific implementation can refer to the relevant introduction in the aforementioned embodiment, and can achieve the same technical effect. To avoid repetition, it will not be repeated here.

[0130] The electronic device may be a terminal or other device other than a terminal. For example, the electronic device may be a mobile phone, a tablet computer, a laptop computer, a PDA, an in-vehicle electronic device, a mobile internet device (MID), an augmented reality (AR) / virtual reality (VR) device, a robot, a wearable device, an ultra-mobile personal computer (UMPC), a netbook, or a personal digital assistant (PDA), etc. It may also be a server, a network attached storage (NAS), a personal computer (PC), a television (TV), an ATM, or an kiosks, etc., and the embodiments of the present application do not specifically limit this.

[0131] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be noted that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0132] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

Claims

1. A photosensitive pixel circuit, comprising: Switching elements, single photon avalanche transistors, sensitivity adjustment modules and counting modules; The first end of the switch element is used to connect a first voltage, the second end of the switch element is used to access a switch control signal, the third end of the switch element is connected to the first end of the single-photon avalanche transistor, and the second end of the single-photon avalanche transistor is used to connect a second voltage, and the second voltage is less than the first voltage; The first input end of the sensitivity adjustment module is connected to the first end of the single-photon avalanche transistor to obtain an initial light sensing signal when the switch control signal controls the switch element to be disconnected, the second input end of the sensitivity adjustment module is used to access the sensitivity control signal, the output end of the sensitivity adjustment module is connected to the input end of the counting module, and the output end of the counting module is used to output a pixel light sensing signal; The sensitivity control signal is used to control the sensitivity adjustment module to switch between a first working state and a second working state; the photosensitive pixel circuit has a first light sensitivity when the sensitivity adjustment module is in the first working state, and the photosensitive pixel circuit has a second light sensitivity when the sensitivity adjustment module is in the second working state, and the first light sensitivity is greater than the second light sensitivity.

2. The photosensitive pixel circuit according to claim 1, wherein: When the switch control signal controls the switch element to be disconnected, the sensitivity adjustment module generates a second light sensing signal according to the initial light sensing signal and the sensitivity control signal, and the counting module generates the pixel light sensing signal according to the second light sensing signal and outputs it through the output end of the counting module.

3. The photosensitive pixel circuit according to claim 1, wherein: The sensitivity control signal is a pulse signal, and the frequency of the sensitivity control signal is changed to control the sensitivity adjustment module to switch between the first working state and the second working state.

4. The photosensitive pixel circuit according to any one of claims 1 to 3, wherein: The sensitivity adjustment module includes a NOT gate and an AND gate; The input end of the NOT gate is connected to the first end of the single-photon avalanche transistor, the output end of the NOT gate is connected to the first input end of the AND gate, the second input end of the AND gate is used to access the sensitivity control signal, and the output end of the AND gate is connected to the output end of the sensitivity adjustment module.

5. The photosensitive pixel circuit according to claim 4, wherein: When the sensitivity control signal is a first pulse signal, the sensitivity adjustment module is in the first working state; when the sensitivity control signal is a second pulse signal, the sensitivity adjustment module is in the second working state; the pulse frequency of the first pulse signal is lower than the pulse frequency of the second pulse signal.

6. The light-sensitive pixel circuit according to claim 4, wherein: When the sensitivity adjustment module is in the first working state, the number of pulses contained in the sensitivity control signal received by the sensitivity adjustment module within a unit time is M; when the sensitivity adjustment module is in the second working state, the number of pulses contained in the sensitivity control signal received by the sensitivity adjustment module within a unit time is N, M and N are both positive integers, and M is less than N.

7. The light-sensitive pixel circuit according to claim 4, wherein: When the switch control signal controls the switch element to be disconnected and the sensitivity control signal is a continuous high level signal, the sensitivity adjustment module is in the first working state; When the switch control signal controls the switch element to be turned off, and the sensitivity control signal is a pulse signal including a plurality of pulses, the sensitivity adjustment module is in the second working state.

8. The photosensitive pixel circuit according to claim 1, wherein: When the ambient light brightness is lower than the brightness threshold, the sensitivity adjustment module is controlled to operate in the first working state through the sensitivity control signal; when the ambient light brightness is higher than the brightness threshold, the sensitivity adjustment module is controlled to operate in the second working state through the sensitivity control signal.

9. The light-sensitive pixel circuit according to claim 1, wherein: The sensitivity control signal is an analog signal, and the voltage of the sensitivity control signal is changed to control the sensitivity adjustment module to switch between the first working state and the second working state.

10. The photosensitive pixel circuit according to claim 1, 2 or 9, wherein: The sensitivity adjustment module includes a comparator; The first input end of the comparator is connected to the first end of the single photon avalanche transistor, the second input end of the comparator is connected to the sensitivity control signal, and the output end of the comparator is connected to the output end of the sensitivity adjustment module.

11. The light-sensing pixel circuit according to claim 10, wherein: The comparator is a common-phase comparator, which reduces the voltage of the sensitivity control signal to make the sensitivity adjustment module work in the first working state; and increases the voltage of the sensitivity control signal to make the sensitivity adjustment module work in the second working state; The comparator is an inverting comparator, which increases the voltage of the sensitivity control signal to make the sensitivity adjustment module work in the first working state; and reduces the voltage of the sensitivity control signal to make the sensitivity adjustment module work in the second working state.

12. An image sensor, comprising the photosensitive pixel circuit according to any one of claims 1 to 11.

13. The image sensor according to claim 12, wherein: It comprises a plurality of the photosensitive pixel circuits, and the plurality of the photosensitive pixel circuits are arranged in an array; The image sensor also includes a controller, which is used to generate the sensitivity control signal, and the controller is connected to the second input end of the sensitivity adjustment module of the plurality of photosensitive pixel circuits.

14. An electronic device comprising the image sensor according to claim 12 or 13.

Images