Photosensitive pixel circuit, image sensor, and electronic device

Abstract

The application discloses a photosensitive pixel circuit, an image sensor and an electronic device, and belongs to the technical field of images. The photosensitive pixel circuit comprises a switching element, a single-photon avalanche transistor, a sensitivity adjusting module and a counting module; the first end of the switching element is used for connecting a first voltage, the second end is used for inputting a switching control signal, the third end is connected with the first end of the single-photon avalanche transistor, and the second end of the single-photon avalanche transistor is used for connecting a second voltage; the first input end of the sensitivity adjusting module is connected with the first end of the single-photon avalanche transistor, and the second input end is used for inputting a sensitivity control signal; the sensitivity control signal is used for controlling the sensitivity adjusting module to switch between a first working state and a second working state; the photosensitive pixel circuit has a first photosensitivity and a second photosensitivity when the sensitivity adjusting module is in the first working state and the second working state respectively, and the first photosensitivity is greater than the second photosensitivity.

Description

Technical Field

[0001] This application belongs to the field of image technology, specifically relating to a photosensitive pixel circuit, an image sensor, and an electronic device. Background Technology

[0002] Single-photon avalanche diodes (SPADs) possess extremely high sensitivity compared to pinned photodiodes (PPDs) in conventional complementary metal-oxide-semiconductor (CMOS) image sensors (CIS). Each photon striking a SPAD generates a corresponding electrical signal, which, after rectification, forms a square-wave pulse signal. This pulse is then counted by a counter and output as a pixel signal. In recent years, researchers have begun exploring the use of SPADs to replace PPDs as pixel sensors in the CIS of ordinary visible-light RGB cameras. This aims to fully utilize the ultra-high sensitivity of SPADs at the single-photon sensing level, enabling imaging capabilities surpassing those of the human eye in extreme low-light conditions.

[0003] However, existing SPAD-based CISs have issues such as... Figure 1 The problem is that in low-light environments, the number of photons is relatively small, allowing for accurate recording of sensed photons. However, in high-light environments, the large number of photons, when incident sequentially on the SPAD pixels, generates a continuous square wave signal. This results in the number of incident photons being far greater than the count of the pixel's counter. When capturing images with complex lighting conditions, the counter counts of some low-light pixels and some high-light pixels may be the same or similar. This prevents the backend image processing software from accurately distinguishing between high-light and low-light pixels, thus affecting image capture quality. Summary of the Invention

[0004] The purpose of this application is to provide a photosensitive pixel circuit, an image sensor, and an electronic device that can solve the problem that existing SPAD-based CIS cannot accurately sense light.

[0005] In a first aspect, embodiments of this application provide a photosensitive pixel circuit, including: a switching element, a single-photon avalanche diode, a sensitivity adjustment module, and a counting module;

[0006] 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 diode, and the second end of the single-photon avalanche diode is used to connect to a second voltage, the second voltage being less than the first voltage;

[0007] The first input terminal of the sensitivity adjustment module is connected to the first terminal of the single-photon avalanche diode to obtain an initial light sensing signal when the switching element is turned off by the switch control signal. The second input terminal of the sensitivity adjustment module is used to receive the sensitivity control signal. The output terminal of the sensitivity adjustment module is connected to the input terminal of the counting module. The output terminal of the counting module is used to output the pixel photosensitive signal.

[0008] 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 photosensitivity when the sensitivity adjustment module is in the first working state, and a second photosensitivity when the sensitivity adjustment module is in the second working state, wherein the first photosensitivity is greater than the second photosensitivity.

[0009] Secondly, embodiments of this application provide an image sensor, including the photosensitive pixel circuit described in the first aspect.

[0010] Thirdly, embodiments of this application provide an electronic device including the image sensor described in the second aspect.

[0011] In this embodiment, the photosensitive pixel circuit includes: a switching element, a single-photon avalanche diode, a sensitivity adjustment module, and a counting module; wherein, a first terminal of the switching element is connected to a first voltage, a second terminal of the switching element is connected to a switching control signal, a third terminal of the switching element is connected to the first terminal of the single-photon avalanche diode, and the second terminal of the single-photon avalanche diode is connected to a second voltage, the second voltage being less than the first voltage; a first input terminal of the sensitivity adjustment module is connected to the first terminal of the single-photon avalanche diode to acquire an initial light-sensing signal when the switching element is turned off by the switching control signal, a second input terminal of the sensitivity adjustment module is connected to a sensitivity control signal, and an output terminal of the sensitivity adjustment module is connected to the input terminal of the counting module, the output terminal of the counting module being used to output a pixel photosensitive signal; the sensitivity control signal is used to control the sensitivity adjustment module to switch between a first operating state and a second operating state; the photosensitive pixel circuit has a first photosensitivity when the sensitivity adjustment module is in the first operating state, and a second photosensitivity when the sensitivity adjustment module is in the second operating state, the first photosensitivity being greater than the second photosensitivity. In this way, by adding a sensitivity adjustment module to the photosensitive pixel circuit based on a single-photon avalanche diode, the light sensitivity of the photosensitive pixel circuit can be adjusted. In practical applications, the working state of the sensitivity control signal can be controlled according to the number of incident photons in the actual environment to adjust the light sensitivity, ensuring that the photosensitive pixel circuit can accurately identify high-light pixels and low-light pixels, thereby improving the image shooting effect. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the photosensitive principle and counting of a SPAD-based CIS chip in the existing technology;

[0013] Figure 2 These are circuit diagrams and working principle diagrams of SPAD-based CIS chips in the existing technology;

[0014] Figure 3 This is a circuit structure diagram of the photosensitive pixel circuit provided in the embodiments of this application;

[0015] Figure 4 This is one of the specific circuit structure diagrams of the photosensitive pixel circuit provided in the embodiments of this application;

[0016] Figure 5a This is provided by the embodiments of this application. Figure 4 The diagram shows the working principle of the photosensitive pixel circuit in a low-light environment.

[0017] Figure 5bThis is provided by the embodiments of this application. Figure 4 The diagram shows the working principle of the photosensitive pixel circuit under high light conditions.

[0018] Figure 6 This is the second specific circuit structure diagram of the photosensitive pixel circuit provided in the embodiments of this application;

[0019] Figure 7 This is provided by the embodiments of this application. Figure 6 The diagram shows the working principle of the photosensitive pixel circuit under high light conditions.

[0020] Figure 8 This is a hardware structure diagram of the image sensor provided in the embodiments of this application;

[0021] Figure 9 This is a hardware structure diagram of the electronic device provided in the embodiments of this application. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0023] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] To make the embodiments of this application clearer, the relevant background technical knowledge involved in the embodiments of this application will be introduced as follows:

[0025] Currently, single-photon avalanche diodes (SPADs) are widely used in direct time-of-flight (dToF) image sensor CIS chips. Their main pixel circuit structure and working principle are as follows: Figure 2 As shown.

[0026] The SPAD (Special Anode Device) is structurally no different from the PPD (Precision Photodiode Device) used in conventional CIS (Corporate Identity Spectroscopy) pixels; the only difference is the higher bias voltage (VDD-VSS), which causes the PPD to operate in the avalanche region. Compared to the PPD, the SPAD has extremely high sensitivity; each photon illuminating the SPAD will generate a corresponding electrical signal. Figure 2 In the typical SPAD pixel structure shown, the SPAD receives a photon and generates a pulse signal Vc. After being rectified by an inverter (NOT gate), it forms a square wave pulse signal Vp. The PMOS transistor switch connected to the power supply voltage VDD acts as a variable resistor, mainly controlling the magnitude 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. Theoretically, the counter will count once after each photon is received by the SPAD. If N photons arrive at the SPAD, the counter will count N times.

[0027] Among different types of CIS (CMOS Image Sensor), SPAD is currently mainly used in dToF (dToF) CIS products as the receiver chip for infrared / near-infrared 3D depth-sensing cameras. In recent years, researchers have begun to explore replacing PPD (pixel photosensitive element) with SPAD as the pixel photosensitive element in ordinary visible light RGB camera CIS. Due to the ultra-high sensitivity of SPAD at the single-photon sensing level, SPAD-based CIS chips exhibit imaging capabilities surpassing the human eye in extreme nighttime scenes.

[0028] Due to the extremely high sensitivity of SPADs, i.e., single-photon response, when used as photosensitive devices in traditional CIS, issues such as... Figure 1 The problem shown:

[0029] In low-light environments, such as those with illuminance less than 10 lux, the number of photons in the environment is relatively small, allowing SPAD-based CMOS single-photon image sensor pixels to accurately record the sensed photons. For example, when three photons are sequentially incident on a SPAD pixel, three square wave signals are generated, and the pixel's counter counts three times. In this case, the number of photons received by the sensor pixel equals the count of the pixel's counter. However, in high-light environments, such as those with illuminance greater than 500 lux, the number of photons in the environment is extremely large, preventing SPAD-based CMOS single-photon image sensor pixels from accurately recording the sensed photons. This is primarily because when a large number of photons are sequentially incident on a SPAD pixel, a continuous square wave signal is generated, while the pixel's counter only counts the number of square waves. Therefore, in this situation, the number of incident photons is much greater than the count of the pixel's counter. Consequently, when a SPAD-based CMOS single-photon image sensor captures images with complex lighting conditions, such as those with both highlights and shadows, issues may arise. Figure 1The problem shown on the right is that the counter counts of some pixels in low-light areas are the same as those of some pixels in high-light areas. This problem causes the back-end image processing software to be unable to distinguish which pixels are sensing high light and which are sensing low light, resulting in errors in photosensitive imaging.

[0030] This application proposes a photosensitive pixel circuit scheme that can adjust pixel sensitivity to address the counting error, also known as oversaturation error, that occurs in SPAD-based CMOS single-photon image sensors under high light conditions. By intervening in pixel sensitivity adjustment, the erroneous counting problem of SPAD-based CMOS single-photon image sensors under high light conditions is solved, enabling the CMOS single-photon image sensor to correctly sense light in both low-light and high-light environments.

[0031] The photosensitive pixel circuit, image sensor, and electronic device provided in this application will be described in detail below with reference to the accompanying drawings and through specific embodiments and application scenarios.

[0032] Please see Figure 3 , Figure 3 The circuit structure diagram of the photosensitive pixel circuit provided in the embodiments of this application is as follows: Figure 3 As shown, the photosensitive pixel circuit includes a switching element, a single-photon avalanche diode (SPAD), a sensitivity adjustment module, and a counting module.

[0033] 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 diode (SPAD), and the second end of the SPAD is used to connect to a second voltage, the second voltage being less than the first voltage;

[0034] The first input terminal of the sensitivity adjustment module is connected to the first terminal of the single-photon avalanche diode (SPAD) to obtain an initial light-sensing signal when the switching element is turned off by the switch control signal. The second input terminal of the sensitivity adjustment module is used to receive the sensitivity control signal. The output terminal of the sensitivity adjustment module is connected to the input terminal of the counting module. The output terminal of the counting module is used to output the pixel light-sensing signal.

[0035] 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 photosensitivity when the sensitivity adjustment module is in the first working state, and a second photosensitivity when the sensitivity adjustment module is in the second working state, wherein the first photosensitivity is greater than the second photosensitivity.

[0036] In this embodiment, to ensure that the photosensitive pixel circuit based on a single-photon avalanche diode (SPAD) can accurately count the number of incident photons even in high-light conditions, without the problem of the same count in high-light and low-light conditions, a sensitivity adjustment module is added to the existing SPAD pixel architecture. This module is located between the SPAD device output signal and the digital counter module. The sensitivity adjustment module can switch its working state to adjust the photosensitivity under the action of an external control signal, i.e., a sensitivity control signal. For example, the sensitivity adjustment module can be in a first working state in high-light conditions to reduce photosensitivity, and in a second working state in low-light conditions to increase photosensitivity or maintain high photosensitivity. This allows it to output a corresponding number of square wave signals according to the number of incident photons, ensuring that the counting module counts the number of incident photons relatively accurately. This, in turn, ensures that the back-end image processing software can accurately identify high-light pixels and low-light pixels and correctly capture images.

[0037] Specifically, such as Figure 3 As shown, the SPAD-based photosensitive pixel circuit proposed in this application embodiment includes a switching element, a single-photon avalanche diode (SPAD), a sensitivity adjustment module, and a counting module.

[0038] The switching element can be implemented using a MOSFET, such as a PMOS or an NMOS. When a PMOS is selected, the source of the PMOS is connected to a first voltage, which can be the power supply voltage VDD. The drain is connected to the cathode of the SPAD, and the gate is connected to the switching control signal ɸ. EXPO When an NMOS is selected, the drain of the NMOS is connected to the first voltage, i.e., the power supply voltage VDD, the source is connected to the cathode of the SPAD, and the gate is connected to the switching control signal ɸ. EXPO The anode of the SPAD can be connected to a second voltage, specifically ground or a negative voltage VSS.

[0039] The switching element can be in an open or closed state under the control of the switching control signal. The single-photon avalanche diode (SPAD) performs photosensitive sensing when the switching element is open, generates an initial photosensitive signal Vc, and inputs it to the sensitivity adjustment module. It is also reset when the switching element is closed. In other words, the switching control signal can be used to control the photosensitive time. When photosensitive sensing is required, the switching control signal outputs a voltage signal to open the switching element. When photosensitive sensing is not required or when photosensitive sensing is complete, the switching control signal outputs a voltage signal to close the switching element.

[0040] The sensitivity adjustment module is located between the output signal of the SPAD and the counting module. Its first input terminal is connected to the anode of the SPAD, and its second input terminal is connected to the sensitivity control signal α. SEN The output terminal is connected to the input terminal of the counting module, and the output terminal of the counting module outputs a counting signal, or pixel photosensitive signal. The counting module can be a digital counter.

[0041] During photosensitivity, the anode of the SPAD outputs an initial photosensitivity signal Vc, which is a pulse voltage signal. The sensitivity adjustment module is used to shape or compare the initial photosensitivity signal Vc and output a second photosensitivity signal Vb, which is a pulse signal, such as a square wave signal, and can be adjusted by the sensitivity control signal ɸ. SEN Under the control of the sensitivity adjustment module, the photosensitive pixel circuit switches its working state. The photosensitive pixel circuit has different photosensitivity in different working states of the sensitivity adjustment module. Correspondingly, the number of square wave signals output by the sensitivity adjustment module within a unit photosensitive time varies in different working states. In other words, the sensitivity adjustment module can switch its working state according to the sensitivity control signal ɸ. SEN The light sensitivity of the photosensitive pixel circuit is adjusted under the control of the module. The counter is used to count the number of square waves output by the sensitivity adjustment module and output a counting signal. This counting signal can be converted into a pixel photosensitive signal by the readout circuit.

[0042] Specifically, the sensitivity control signal ɸ SEN It can also be called the pixel sensitivity adjustment signal. This signal can be a 1-bit or N-bit digital signal or an analog signal. This signal, together with the initial light sensing signal Vc output by the SPAD device, enters the sensitivity adjustment module.

[0043] When controlled by switch signal ɸ EXPO When the switching element is turned off, the SPAD performs exposure / photosensing. At this time, the sensitivity control signal ɸ is changed / adjusted. SEN This can change the light sensitivity of the SPAD pixel, and the counting speed of the counting module will change accordingly. In practical applications, the sensitivity control signal ɸ SEN Specifically, the sensitivity adjustment module can be changed / adjusted according to the ambient light intensity to ensure that the working state of the sensitivity adjustment module matches the ambient light intensity, so that the number of square wave signals output by the sensitivity adjustment module in a unit photosensitive time and the count of the counting module match the number of incident photons in the actual environment.

[0044] In practical applications, the switch control signal ɸ EXPO and the sensitivity control signal ɸ SENAn external controller can output a suitable switching control signal (ɸ) to the photosensitive pixel circuit. EXPO and sensitivity control signal ɸ SEN The system controls the photosensitive pixel circuit to sense light, and can adjust the sensitivity control signal α according to the ambient light intensity. SEN The parameters, such as signal magnitude or signal frequency, are used to control the light sensitivity of the photosensitive pixel circuit.

[0045] This design effectively adjusts the light sensitivity of SPAD pixels, ensuring that the photosensitive pixel circuit outputs the correct pixel light-sensing signal under different lighting conditions.

[0046] Optionally, when the switch control signal controls the switch element to open, 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 photosensitive signal based on the second light sensing signal and outputs it through the output terminal of the counting module.

[0047] Specifically, the switching element is as follows: Figure 3 In the case of the PMOS transistor shown, the switch control signal ɸ EXPO A high-level signal can be used to control the PMOS transistor to be in the off state, and the SPAD will generate an initial photosensor signal Vc under photon irradiation; or, if the switching element is an NMOS transistor, the switch control signal ɸ EXPO A low-level signal can be used to control the PMOS transistor to be in the off state, and the SPAD generates an initial photosensitive signal Vc under the illumination of photons.

[0048] The sensitivity adjustment module acquires the initial photosensing signal Vc generated by the SPAD and, under the action of the sensitivity control signal, generates a second photosensing signal Vb. Specifically, the initial photosensing signal Vc input to the sensitivity adjustment module can adjust the number of square waves in the output second photosensing signal Vb under the interference of the sensitivity control signal. The counting module generates a pixel photosensing signal based on the second photosensing signal Vb. Specifically, the pixel photosensing signal can be generated by counting the square waves of the second photosensing signal Vb; that is, the pixel photosensing signal can be a counting signal, which is finally output through the output terminal of the counting module.

[0049] In this embodiment, the sensitivity adjustment module can generate a second light sensing signal based on the initial light sensing signal and sensitivity control signal generated by the SPAD, and then output the pixel light sensing signal through the counting module to realize the light sensing control logic.

[0050] 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.

[0051] In one embodiment, the sensitivity control signal ɸ SEN The signal can be a pulse signal, and the operating state of the sensitivity adjustment module can be switched by changing the frequency of the pulse signal. Specifically, different pulse signals result in different numbers of pulses within the same time period. By superimposing this pulse signal with the initial photosensitive signal Vc, the number of square waves in the second photosensitive signal Vb output by the sensitivity adjustment module can be changed, thereby switching the operating state of the sensitivity adjustment module.

[0052] For example, such as Figure 5a and Figure 5b As shown, the sensitivity control signal ɸ SEN It is a pulse signal, and Figure 5a The frequency of the medium pulse signal is lower than Figure 5b As the frequency of the pulse signal changes, the number of square waves in the second photosensitive signal Vb output by the sensitivity adjustment module within the same time period also changes accordingly.

[0053] In practical applications, the sensitivity control signal ɸ SEN The frequency can be adjusted by an external controller according to the ambient light intensity to match the working state of the sensitivity adjustment module and the light sensitivity of the photosensitive pixel circuit with the actual lighting environment. Specifically, in high-light environments, for example, when the ambient light intensity is higher than a preset brightness threshold, the sensitivity control signal α can be increased. SEN The frequency is adjusted to increase the number of output pulses, thereby converting the original continuous square wave signal into multiple square wave signals, increasing the count of incident photons; in low-light environments, such as when the ambient light is below a preset brightness threshold, the sensitivity control signal ɸ is lowered. SEN The frequency is adjusted to maintain the original number of square wave signals output, thus maintaining the normal counting of incident photons.

[0054] The preset brightness threshold can be a threshold that defines low-light and high-light environments, such as 200 Lux, where above the threshold is a high-light environment and below it is a low-light environment. Alternatively, it can be a threshold that defines high-light and non-high-light environments, such as 500 Lux, where above the threshold is a high-light environment and below the threshold is not a high-light environment. In particular, thresholds that distinguish different levels of lighting environments can be set according to actual needs.

[0055] It should be noted that in this embodiment, under high light conditions, the number of incident photons is large and their continuity is strong, such as... Figure 1and Figure 2 As shown, the output signal Vp of the NOT gate will remain at a high level continuously when photons are continuously incident on the SPAD device. At this time, by increasing the sensitivity control signal ɸ SEN The frequency of the second photosensitive signal Vb output by the sensitivity adjustment module can be increased within a unit photosensitive time, thereby increasing the number of square waves and accelerating the counting of the counting module, thus recording more photons. In this case, appropriately reducing the sensitivity control signal ɸ SEN The frequency can effectively slow down the counting speed of the counting module, thereby reducing the sensitivity of SPAD pixels under strong light and preventing SPAD pixels from being overexposed quickly under strong light.

[0056] However, it should be noted that in high-light environments, the sensitivity control signal ɸ SEN The frequency cannot be reduced too much; a safe frequency threshold f needs to be set. THR To ensure the sensitivity control signal ɸ SEN The frequency is always greater than f THR The reason is that SPAD pixels must ensure a certain level of sensitivity to detect and count a certain number of incident photons, in order to prevent the output signal from being too different in strong and weak light environments, which would lead to a narrowing of the dynamic range.

[0057] In this embodiment, the sensitivity adjustment of the SPAD pixel is achieved through a pulse digital signal ɸ SEN The sensitivity is adjusted by changing the frequency of this signal, similar to pulse frequency modulation (PFM). The adjustment principle is simple and easy to operate.

[0058] Optionally, the sensitivity adjustment module includes NOT gates and AND gates;

[0059] The input terminal of the NOT gate is connected to the first terminal of the single-photon avalanche diode (SPAD), the output terminal of the NOT gate is connected to the first input terminal of the AND gate, the second input terminal of the AND gate is used to receive the sensitivity control signal, and the output terminal of the AND gate is connected to the output terminal of the sensitivity adjustment module.

[0060] like Figure 4 As shown, in one embodiment, the sensitivity adjustment module can be composed of a NOT gate and an AND gate. The input of the NOT gate is connected to the output signal of the SPAD device, i.e., the initial photosensing signal Vc. The NOT gate inverts the initial photosensing signal Vc and outputs a first photosensing signal Vp, where Vp is a square wave pulse signal. The input signals of the AND gate are the first photosensing signal Vp and the sensitivity control signal ɸ. SENThe AND gate is used to connect the first photosensitive signal Vp and the sensitivity control signal ɸ SEN After performing the AND operation, the second photosensitive signal Vb is output, which is also a square wave pulse signal.

[0061] In some embodiments, the sensitivity control signal ɸ SEN The signal can be a pulse signal, such as a 1-bit binary digital signal, meaning it only has two signals: 1 and 0. The second photosensitive signal Vb is also a 1-bit digital signal. The counting module can be an N-bit digital counter. In this way, the second photosensitive signal Vb is transmitted to the N-bit digital counter for counting. The maximum count of the counter is N bits of binary digits, which means it can count N 1s.

[0062] In this implementation, the pixel sensitivity adjustment module is a purely digital circuit design and is placed in the SPAD pixel circuit processing link. It is independent of the SPAD device manufacturing process, optical structure, and working principle, and will not affect the operation of other pixel modules. Moreover, it only requires the sensitivity control signal α to be adjusted. SEN The light sensitivity can be controlled by adjusting the frequency, and the adjustment method is simple.

[0063] 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.

[0064] In some embodiments, for Figure 4 The photosensitive pixel circuit design shown herein includes a sensitivity control signal ɸ. SEN It can be a periodic pulse signal, and the sensitivity adjustment module can be controlled to operate in different states by adjusting the frequency of the pulse signal.

[0065] Specifically, in the sensitivity control signal ɸ SEN When the first pulse signal has a low frequency, the sensitivity adjustment module is in its first operating state. At this time, the light sensitivity of the photosensitive pixel circuit is high, and the sensitivity control signal ɸ SEN When the second pulse signal has a higher frequency, the sensitivity adjustment module is in the second working state, at which time the light sensitivity of the photosensitive pixel circuit is low.

[0066] For example, under the first illumination environment, the sensitivity control signal ɸ can be adjusted. SEN The first pulse signal is a first pulse signal of a first frequency, thereby controlling the sensitivity adjustment module to be in a first working state. Under the second lighting environment, the sensitivity control signal α can be adjusted.SEN The second pulse signal is a second pulse signal at a second frequency, thereby controlling the sensitivity adjustment module to be in a second operating state; wherein, the illumination parameters of the first illumination environment can be less than those of the second illumination environment, the first frequency is lower than the second frequency, and the light sensitivity corresponding to the first operating state is greater than that corresponding to the second operating state. In other words, the sensitivity control signal α can be lowered under relatively low illumination conditions. SEN The frequency of the sensitivity control signal can be adjusted to achieve higher photosensitivity. In relatively high-light environments, the sensitivity control signal can be increased. SEN The frequency is adjusted to reduce photosensitivity.

[0067] In this embodiment, the sensitivity adjustment of SPAD pixels can be achieved by changing the frequency of the pulse signal, similar to the sensitivity adjustment achieved by pulse frequency modulation (PFM). The adjustment principle is simple and highly operable.

[0068] Furthermore, when the sensitivity adjustment module is in the first working state, the number of pulses 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 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.

[0069] In other embodiments, for Figure 4 The photosensitive pixel circuit design shown herein includes a sensitivity control signal ɸ. SEN It 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 per unit time.

[0070] Specifically, the sensitivity control signal ɸ received by the sensitivity adjustment module per unit time SEN When the number of pulses contained is M, the sensitivity adjustment module is in its first working state. At this time, the light sensitivity of the photosensitive pixel circuit is relatively high. The sensitivity control signal ɸ received by the sensitivity adjustment module per unit time... SEN When the number of pulses contained is N, the sensitivity adjustment module is in the second working state. At this time, the light sensitivity of the photosensitive pixel circuit is low, where M is less than N.

[0071] For example, under the first illumination environment, the sensitivity control signal ɸ can be adjusted. SEN The number of pulses per unit time is 100, thereby controlling the sensitivity adjustment module to be in the first working state. Under the second lighting environment, the sensitivity control signal ɸ can be adjusted.SEN The number of pulses per unit time is 200, thereby controlling the sensitivity adjustment module to be in a second working state; wherein, the illumination parameters of the first illumination environment can be less than the illumination parameters of the second illumination 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 to say, the sensitivity control signal α can be reduced in a relatively low illumination environment. SEN The number of pulses per unit time is used to obtain higher photosensitivity. In relatively high illumination environments, the sensitivity control signal ɸ can be increased. SEN The number of pulses per unit time is used to reduce photosensitivity.

[0072] 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.

[0073] Optionally, when the switch control signal controls the switch element to open and the sensitivity control signal is a continuous high-level signal, the sensitivity adjustment module is in the first working state;

[0074] When the switch control signal controls the switch element to open, and the sensitivity control signal is a pulse signal containing multiple pulses, the sensitivity adjustment module is in the second working state.

[0075] In one embodiment, the sensitivity control signal ɸ SEN A continuous high-level signal can be maintained during the photosensitivity period to keep the sensitivity adjustment module in a first operating state, which can correspond to the operating state with the highest photosensitivity. For example, the sensitivity control signal α can be adjusted when the ambient light is lower than a preset brightness threshold, i.e., in a low-light environment. SEN If the signal is a continuous high-level signal, such as a digital 1 signal, the number of square waves in the second photosensitive signal Vb output by the AND gate is the same as the number of square waves in the first photosensitive signal Vp output by the NOT gate. That is, the number of incident photons is small at this time, so there is no need to reduce the photosensitiveness and the highest photosensitiveness can be maintained.

[0076] In this case, the principle of adjusting the light sensitivity of SPAD pixels can be as follows: Figure 5a As shown. In low-light environments, the SPAD pixel receives fewer photons. Therefore, it's necessary to adjust the SPAD pixel's light sensitivity to a high sensitivity level. Specifically, this is done by adjusting the switch control signal ɸ within a unit exposure time. EXPO The period of time the sensitivity control signal ɸ is lowered SEN The frequency needs to be adjusted as low as possible to achieve high sensitivity. Figure 5aIn the example shown, the sensitivity control signal ɸ SEN The frequency is at its lowest, meaning it is at a high level throughout the exposure time. At this time, each incident photon will excite an initial photosensitive signal Vc pulse wave and cause the first photosensitive signal Vp to generate a corresponding square wave. At the AND gate output, the second photosensitive signal Vb corresponds to the first photosensitive signal Vp. At this time, the count recorded by the counting module is the number of incident photons.

[0077] In this embodiment, the sensitivity control signal ɸ SEN Alternatively, a pulse signal containing multiple pulses can be used within the photosensitivity time to put the sensitivity adjustment module into a second operating state, which can correspond to a lower photosensitivity. For example, when the ambient light intensity is higher than the preset illumination parameter threshold, i.e., in a high-light environment, the sensitivity control signal α can be adjusted. SEN It is a signal that alternates between low and high levels, and the sensitivity control signal ɸ can be adjusted. SEN The frequency or number of pulses per unit time, at which point the sensitivity control signal ɸ SEN The number of pulses contained per unit time will directly determine the number or frequency of square wave signals output by the AND gate during the photosensitive time, as well as the counting frequency of the digital counter.

[0078] In this case, the principle of SPAD pixel sensitivity adjustment can be as follows: Figure 5b As shown. In high-light environments, SPAD pixels receive a large number of photons. Therefore, it is necessary to reduce the sensitivity of the SPAD pixels. This can be achieved by changing the sensitivity control signal ɸ. SEN The frequency. For example... Figure 5b As shown, under high illumination, the number of incident photons is large and their continuity is strong. The output signal of the NOT gate, i.e., the first photosensitizing signal Vp, will remain continuously at a high level when photons continuously incident on the SPAD device. At this time, the sensitivity control signal ɸ SEN The frequency of the AND gate output square wave signal and the counting frequency of the digital counter will be directly determined. The sensitivity control signal ɸ SEN The higher the frequency, the more square waves the first photosensitive signal Vb output by the AND gate has, and the faster the digital counter counts, thus recording more photons. In this case, appropriately reducing the sensitivity control signal ɸ SEN The frequency can effectively slow down the counting speed of the counter, thereby reducing the sensitivity of SPAD pixels under strong light and preventing SPAD pixels from being overexposed quickly under strong light.

[0079] It should be noted that under high light conditions, the sensitivity control signal ɸ SENThe frequency cannot be reduced too much; a safe frequency threshold f needs to be set. THR To ensure the sensitivity control signal ɸ SEN The frequency is always greater than f THR The reason is that SPAD pixels must ensure a certain level of sensitivity to detect and count a certain number of incident photons, in order to prevent the output signal from being too different in strong and weak light environments, which would lead to a narrowing of the dynamic range.

[0080] Figure 4 The illustrated embodiment has the following advantages: the SPAD-based photosensitive pixel circuit can adjust pixel sensitivity to capture images under different lighting conditions, and will not produce significant counting errors when shooting under high light conditions; the pixel sensitivity adjustment module is a purely digital circuit design and is placed in the SPAD pixel circuit processing link, independent of the SPAD device manufacturing process, optical structure, and working principle, and will not affect the operation of other pixel modules; the SPAD pixel sensitivity adjustment is achieved through a single digital signal α. SEN The sensitivity is adjusted by changing the frequency of this digital signal, similar to pulse frequency modulation (PFM). The adjustment principle is simple and easy to operate.

[0081] Optionally, the sensitivity adjustment module generates a second photosensing signal based on the initial photosensing signal and the sensitivity control signal; the counting module records the number of pulses in the second photosensing signal to generate the pixel photosensing signal.

[0082] Specifically, the photosensitive pixel circuit begins to sense light when the switching element is in the off state. The SPAD generates an initial light-sensing signal Vc under photon irradiation. The sensitivity adjustment module acquires the initial light-sensing signal Vc generated by the SPAD and modifies it with the sensitivity control signal ɸ. SEN The calculation generates a second photosensing signal Vb. Specifically, the initial photosensing signal Vc first passes through a NOT gate to output a first photosensing signal Vp, which is then compared with the sensitivity control signal ɸ. SEN The AND operation is performed to output a second photosensitizing signal Vb, which is a pulse signal. The counting module then generates the pixel photosensitizing signal by counting the number of pulses in the second photosensitizing signal Vb.

[0083] In this embodiment, the sensitivity adjustment module can generate a second light sensing signal based on the initial light sensing signal and sensitivity control signal generated by the SPAD, and then output the pixel light sensing signal through the counting module to realize the light sensing control logic.

[0084] Optionally, when the ambient light intensity 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 intensity is higher than the brightness threshold, the sensitivity adjustment module is controlled to operate in the second working state by the sensitivity control signal.

[0085] In practical applications, the sensitivity adjustment module can be controlled to work in a corresponding working state according to the ambient light brightness, so that the photosensitive pixel circuit can change 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.

[0086] Specifically, in low-light environments, such as when the ambient light is below 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 high light sensitivity; in high-light environments, such as when the ambient light 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.

[0087] The brightness threshold can be a threshold that defines low-light and high-light environments, such as 200 Lux, where above the threshold is a high-light environment and below the threshold is a low-light environment. Alternatively, it can be a threshold that defines high-light and non-high-light environments, such as 500 Lux, where above the threshold is a high-light environment and below the threshold is not a high-light environment. In particular, thresholds that distinguish different levels of lighting environments can be set according to actual needs.

[0088] 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.

[0089] In another embodiment, the sensitivity control signal ɸ SEN The signal can be an analog signal, and the operating state of the sensitivity adjustment module can be switched by changing the voltage magnitude of the analog signal. Specifically, different voltage magnitudes of the analog signal, through comparison with the initial photosensing signal Vc, can change the number of square waves in the second photosensing signal Vb output by the sensitivity adjustment module, thereby switching the operating state of the sensitivity adjustment module.

[0090] For example, such as Figure 7 As shown, the sensitivity control signal ɸ SEN As the analog signal changes in voltage, the number of square waves in the second photosensitive signal Vb output by the sensitivity adjustment module within the same time period also changes accordingly.

[0091] In practical applications, the sensitivity control signal ɸ SEN The sensitivity of the SAPD pixels can be adjusted according to the ambient light intensity via an external controller to match the actual lighting environment. Specifically, in high-light environments, such as when the ambient light intensity exceeds a preset brightness threshold, the sensitivity control signal α can be adjusted. SEN The voltage is set to a suitable value so that the comparator outputs a certain number of square wave signals; in low-light environments, for example, when the ambient light is lower than the preset brightness threshold, the sensitivity control signal α is appropriately adjusted. SEN The voltage magnitude is such that the comparator outputs a square wave signal with the same number of incident photons.

[0092] In this embodiment, the sensitivity adjustment of the SPAD pixel is achieved through an analog voltage signal α. SEN The sensitivity is adjusted by changing the voltage of this signal. The adjustment principle is simple and easy to operate.

[0093] Optionally, the sensitivity adjustment module includes a comparator;

[0094] The first input terminal of the comparator is connected to the first terminal of the single-photon avalanche diode (SPAD), the second input terminal of the comparator is connected to the sensitivity control signal, and the output terminal of the comparator is connected to the output terminal of the sensitivity adjustment module.

[0095] like Figure 6 As shown, in another embodiment, the sensitivity adjustment module can be implemented using a comparator (CMP) based on an operational amplifier. The input signals of the comparator are the initial photosensitivity signal Vc output by the SPAD device and the sensitivity control signal ɸ. SEN The comparator compares the initial light-sensing signal Vc with the sensitivity control signal ɸ. SEN After comparison, the second photosensitive signal Vb is output.

[0096] In some embodiments, the sensitivity control signal ɸ SEN It can be an analog voltage signal; the sensitivity of the SPAD pixel is adjusted by the sensitivity control signal ɸ. SEN The voltage magnitude is determined by the amount of incident photons. When a photon is incident on the SPAD device, the SPAD outputs an initial photosensitivity signal Vc, the magnitude and frequency of which are determined by the number of incident photons.

[0097] In this implementation, the pixel sensitivity adjustment module is designed as an analog circuit and placed in the SPAD pixel circuit processing link. It is independent of the SPAD device manufacturing process, optical structure, and working principle, and will not affect the operation of other pixel modules. Moreover, it only requires adjustment of the sensitivity control signal α. SEN The light sensitivity can be controlled by adjusting the size of the sensor, and the adjustment method is simple.

[0098] Optionally, the comparator is a non-inverting comparator, which lowers 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.

[0099] The comparator is an inverting comparator. Increasing the voltage of the sensitivity control signal causes the sensitivity adjustment module to operate in the first operating state; decreasing the voltage of the sensitivity control signal causes the sensitivity adjustment module to operate in the second operating state.

[0100] In practical applications, the sensitivity control signal ɸ SEN The sensitivity of the SAPD pixels can be adjusted according to the ambient light intensity via an external controller to match the actual lighting environment. Specifically, in high-light environments, such as when the ambient light intensity exceeds a preset brightness threshold, the sensitivity control signal α can be adjusted. SEN The voltage is set to a suitable value so that the comparator outputs a certain number of square wave signals; in low-light environments, for example, when the ambient light is lower than the preset brightness threshold, the sensitivity control signal α is appropriately adjusted. SEN The voltage magnitude is such that the comparator outputs a square wave signal with the same number of incident photons.

[0101] In practical implementation, based on the working principle of the comparator, the sensitivity control signal α can be adjusted according to the ambient light intensity. SEN The voltage level is adjusted to regulate the sensitivity of the SPAD pixels and adapt them to the actual lighting environment.

[0102] Specifically, the comparator is a non-inverting comparator. When the voltage of the initial photosensitive signal is greater than the voltage of the sensitivity control signal, the second photosensitive signal output by the comparator is at a high level; when the voltage of the initial photosensitive signal is less than or equal to the voltage of the sensitivity control signal, the second photosensitive signal output by the comparator is at a low level; the counting module generates the pixel photosensitive signal based on the second photosensitive signal.

[0103] Alternatively, the comparator is an inverting comparator. When the voltage of the initial photosensitive signal is less than the voltage of the sensitivity control signal, the second photosensitive signal output by the comparator is high; when the voltage of the initial photosensitive signal is greater than or equal to the voltage of the sensitivity control signal, the second photosensitive signal output by the comparator is low; the counting module generates the pixel photosensitive signal based on the second photosensitive signal.

[0104] In one scenario, the comparator is a non-inverting comparator, and its operating mode is as follows: when the initial light-sensing signal Vc output by the SPAD is greater than or equal to the sensitivity control signal ɸ SEN When the initial photosensitive signal Vc is less than the sensitivity control signal ɸ, the second photosensitive signal Vb output by the comparator is pulled high; when the initial photosensitive signal Vc is less than the sensitivity control signal ɸ, the second photosensitive signal Vb is pulled high. SEN At that time, the second photosensitive signal Vb output by the comparator is pulled low to a low level.

[0105] In this case, the sensitivity control signal ɸ can be reduced. SEN The voltage is used to control the sensitivity adjustment module to operate in the first working state to obtain higher photosensitivity; and the sensitivity control signal α can be increased. SEN The voltage is used to control the sensitivity adjustment module to operate in the second working state in order to reduce photosensitivity.

[0106] For example, when the ambient light is lower than the preset brightness threshold, i.e. in a low-light environment, the sensitivity control signal α can be adjusted to be as low as possible. SEN The voltage is set to a value that is not lower than the minimum output voltage of the initial photosensitive signal Vc, so that the number of square waves in the second photosensitive signal Vb output by the comparator is the same as the number of pulse waves in the initial photosensitive signal Vc. That is, the number of incident photons is small at this time, which can maintain high sensitivity.

[0107] When the ambient light intensity is higher than the preset brightness threshold, i.e., in a high-light environment, the sensitivity control signal α can be increased. SEN The voltage magnitude, at which point the sensitivity control signal ɸ SEN The voltage magnitude affects the frequency of the square wave signal output by the comparator and the counting frequency of the digital counter.

[0108] In this case, the principle of SPAD pixel sensitivity adjustment can be as follows: Figure 7 As shown. In this case, when the initial light-sensing signal Vc is greater than or equal to the sensitivity control signal ɸ SEN When the initial photosensitive signal Vc is less than the sensitivity control signal ɸ, the second photosensitive signal Vb output by the comparator is pulled high; when the initial photosensitive signal Vc is less than the sensitivity control signal ɸ, the second photosensitive signal Vb is pulled high. SENWhen the comparator outputs the second photosensitive signal Vb, it is pulled low. When the sensitivity control signal ɸ SEN When the voltage is increased, the sensitivity of the SPAD pixels decreases, and vice versa. Therefore, the sensitivity control signal ɸ can be appropriately increased at this time. SEN The voltage magnitude is controlled to be no higher than the highest output voltage of the initial photosensitive signal Vc, or even no higher than the maximum pulse voltage of the initial photosensitive signal Vc, so that the comparator can output as many square wave signals as possible.

[0109] In another scenario, the comparator operates in the following mode: when the initial light-sensing signal Vc output by the SPAD is less than the sensitivity control signal ɸ SEN When the comparator outputs the second photosensing signal Vb, it is pulled high; when the initial photosensing signal Vc is greater than or equal to the sensitivity control signal ɸ SEN At that time, the second photosensitive signal Vb output by the comparator is pulled low to a low level.

[0110] In this case, the sensitivity control signal ɸ can be increased. SEN The voltage is used to control the sensitivity adjustment module to operate in the first working state to obtain higher photosensitivity; and the sensitivity control signal α can be reduced. SEN The voltage is used to control the sensitivity adjustment module to operate in the second working state in order to reduce photosensitivity.

[0111] For example, when the ambient light is below the preset brightness threshold, i.e., in a low-light environment, the sensitivity control signal α can be increased as much as possible. SEN The voltage is set to a value that is not higher than the maximum output voltage of the initial photosensitive signal Vc, so that the number of square waves in the second photosensitive signal Vb output by the comparator is the same as the number of pulse waves in the initial photosensitive signal Vc. That is, the number of incident photons is small at this time, which can maintain high sensitivity.

[0112] When the ambient light intensity is higher than the preset brightness threshold, i.e., in a high-light environment, the sensitivity control signal α can be reduced. SEN The voltage magnitude, at which point the sensitivity control signal ɸ SEN The voltage magnitude affects the frequency of the square wave signal output by the comparator and the counting frequency of the digital counter.

[0113] Specifically, when the sensitivity control signal ɸ SEN When the voltage is increased, the sensitivity of the SPAD pixel increases, and vice versa. Therefore, the sensitivity control signal ɸ can be appropriately reduced at this time. SENThe voltage magnitude is set such that it is not higher than the maximum pulse voltage of the initial photosensitive signal Vc, and not lower than the minimum output voltage of the initial photosensitive signal Vc, so that the comparator can output as many square wave signals as possible.

[0114] same Figure 4 The implementation shown is similar; in high-light environments, the sensitivity control signal ɸ SEN A safe voltage threshold V needs to be set. THR To ensure the sensitivity control signal ɸ SEN The size adjustment range has always been V THR Within, that is, not exceeding V THR The reason is that SPAD pixels must ensure a certain level of sensitivity to detect and count a certain number of incident photons, in order to prevent the output signal from being too different in strong and weak light environments, which would lead to a narrowing of the dynamic range.

[0115] Figure 6 The illustrated embodiment has the following advantages: the photosensitive pixel circuit based on SPAD pixels can adjust pixel sensitivity to capture images under different lighting conditions, and will not produce obvious counting errors when taking pictures under high light conditions; the pixel sensitivity adjustment module is designed as an analog circuit and placed in the SPAD pixel circuit processing link, which 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 SPAD pixels is achieved through a single analog signal α. SEN The sensitivity is adjusted by changing the voltage of this analog signal. The adjustment principle is simple and easy to operate.

[0116] The photosensitive pixel circuit in this embodiment includes: a switching element, a single-photon avalanche diode, a sensitivity adjustment module, and a counting module; wherein, a first terminal of the switching element is connected to a first voltage, a second terminal of the switching element is connected to a switching control signal, a third terminal of the switching element is connected to the first terminal of the single-photon avalanche diode, and the second terminal of the single-photon avalanche diode is connected to a second voltage, the second voltage being less than the first voltage; a first input terminal of the sensitivity adjustment module is connected to the first terminal of the single-photon avalanche diode to acquire an initial light-sensing signal when the switching element is turned off by the switching control signal, a second input terminal of the sensitivity adjustment module is connected to a sensitivity control signal, and an output terminal of the sensitivity adjustment module is connected to the input terminal of the counting module, the output terminal of the counting module being used to output a pixel photosensitive signal; the sensitivity control signal is used to control the sensitivity adjustment module to switch between a first operating state and a second operating state; the photosensitive pixel circuit has a first photosensitivity when the sensitivity adjustment module is in the first operating state, and a second photosensitivity when the sensitivity adjustment module is in the second operating state, the first photosensitivity being greater than the second photosensitivity. In this way, by adding a sensitivity adjustment module to the photosensitive pixel circuit based on a single-photon avalanche diode, the light sensitivity of the photosensitive pixel circuit can be adjusted. In practical applications, the working state of the sensitivity control signal can be controlled according to the number of incident photons in the actual environment to adjust the light sensitivity, ensuring that the photosensitive pixel circuit can accurately identify high-light pixels and low-light pixels, thereby improving the image shooting effect.

[0117] Please see Figure 8 This application also provides an image sensor, including the photosensitive pixel circuit described in the foregoing embodiments.

[0118] Optionally, such as Figure 8 As shown, the image sensor includes a plurality of photosensitive pixel circuits, and the plurality of photosensitive pixel circuits are arranged in an array;

[0119] The image sensor also includes a controller for generating the sensitivity control signal, and the controller is connected to the second input terminal of the sensitivity adjustment module of the plurality of photosensitive pixel circuits.

[0120] like Figure 8As shown, the image sensor is configured with multiple photosensitive pixel circuit arrays 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 also 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 photosensitive, photoelectric conversion, and signal output. The signal output by the pixels is read by the readout circuit and then output to the outside of the chip via the port circuit. Figure 8 The design of a photosensitive pixel circuit, namely a SPAD pixel structure, is also shown. Each pixel includes a controller, an 11-bit digital counter, a SPAD device, a sensitivity adjustment module, and a readout circuit. When the excitation signal reaches the controller, the controller controls the SPAD to perform photoelectric conversion, and the digital counter counts the results. The result is read by the readout circuit and output as the pixel output signal.

[0121] The light sensitivity of the SPAD pixel is controlled by a sensitivity control signal ɸ SEN Control is performed. When the sensitivity adjustment module is controlled to be in the first working state via this signal, the pixel enters a high-sensitivity mode; when the sensitivity adjustment module is controlled to be in the second working state via this signal, the pixel enters a low-sensitivity mode. The sensitivity control signal for all pixels in the pixel array is the same signal. This signal is generated by the user settings and transmitted to the chip, where it is issued to each pixel by the column controller and row controller. The output pixel photosensitive signal is processed by the readout circuit module and undergoes analog-to-digital conversion. After being processed by the image signal processing (ISP) module, it is output to the outside of the chip via the port circuit (I / O).

[0122] It should be noted that this embodiment is as a comparison with... Figure 3 The implementation methods of the image sensor corresponding to the illustrated embodiment can be found in the relevant descriptions in the foregoing embodiments, and can achieve the same technical effect. To avoid repetition, they will not be described again here.

[0123] Please see Figure 9 This application also provides an electronic device, including... Figure 8 The image sensor described in the illustrated embodiment.

[0124] Furthermore, the electronic device includes N Compact Camera Modules (CCMs), each of which is equipped with one of the image sensors; each of the image sensors is connected to the Image Signal Processing (ISP) module in the central processing unit.

[0125] Image sensor (CIS) chips, as photosensitive components, are a core component of compression camera modules (CCMs). Currently, the system architecture of a typical mobile communication device, such as a mobile phone, is as follows: Figure 9 As shown, the system can consist of N CCM module systems. Each CCM module is equipped with a CIS chip, and the CIS chips communicate bidirectionally with the central processing unit (such as an application processor (AP)) or the ISP module in a system-on-chip (SoC) via port links. The AP / SoC sends control signals to the CIS chip in each CCM, and the CIS generates image signals and sends them back to the ISP module for backend processing.

[0126] It should be noted that this embodiment is as a comparison with... Figure 3 The implementation methods of the electronic devices corresponding to the embodiments shown can be found in the relevant descriptions in the foregoing embodiments, and can achieve the same technical effects. To avoid repetition, they will not be described again here.

[0127] The aforementioned electronic device can be a terminal or other devices besides a terminal. For example, the electronic device can be a mobile phone, tablet computer, laptop computer, handheld computer, in-vehicle electronic device, mobile internet device (MID), augmented reality (AR) / virtual reality (VR) device, robot, wearable device, ultra-mobile personal computer (UMPC), netbook, or personal digital assistant (PDA), etc. It can also be a server, network attached storage (NAS), personal computer (PC), television (TV), ATM, or self-service machine, etc. The embodiments of this application do not specifically limit the scope.

[0128] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0129] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A photosensitive pixel circuit, characterized in that, include: Switching elements, single-photon avalanche diodes, sensitivity adjustment modules, and counting modules; 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 diode, and the second end of the single-photon avalanche diode is used to connect to a second voltage, the second voltage being less than the first voltage; The first input terminal of the sensitivity adjustment module is connected to the first terminal of the single-photon avalanche diode to obtain an initial light sensing signal when the switching element is turned off by the switch control signal. The second input terminal of the sensitivity adjustment module is used to receive the sensitivity control signal. The output terminal of the sensitivity adjustment module is connected to the input terminal of the counting module. The output terminal of the counting module is used to output the pixel photosensitive 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 photosensitivity when the sensitivity adjustment module is in the first working state, and a second photosensitivity when the sensitivity adjustment module is in the second working state, wherein the first photosensitivity is greater than the second photosensitivity.

2. The photosensitive pixel circuit according to claim 1, characterized in that, When the switch control signal controls the switch element to open, 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 photosensitive signal based on the second light sensing signal and outputs it through the output terminal of the counting module.

3. The photosensitive pixel circuit according to claim 1, characterized in that, The sensitivity control signal is a pulse signal. Changing the frequency of the sensitivity control signal controls 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, characterized in that, The sensitivity adjustment module includes NOT gates and AND gates; The input terminal of the NOT gate is connected to the first terminal of the single-photon avalanche diode, the output terminal of the NOT gate is connected to the first input terminal of the AND gate, the second input terminal of the AND gate is used to receive the sensitivity control signal, and the output terminal of the AND gate is connected to the output terminal of the sensitivity adjustment module.

5. The photosensitive pixel circuit according to claim 4, characterized in that, 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 photosensitive pixel circuit according to claim 4, characterized in that, When the sensitivity adjustment module is in the first working state, the number of pulses 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 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.

7. The photosensitive pixel circuit according to claim 4, characterized in that, When the switch control signal controls the switch element to open 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 open, and the sensitivity control signal is a pulse signal containing multiple pulses, the sensitivity adjustment module is in the second working state.

8. The photosensitive pixel circuit according to claim 1, characterized in that, When the ambient light intensity is below 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 intensity is above the brightness threshold, the sensitivity adjustment module is controlled to operate in the second working state by the sensitivity control signal.

9. The photosensitive pixel circuit according to claim 1, characterized in that, The sensitivity control signal is an analog signal. Changing the voltage of the sensitivity control signal controls 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, characterized in that, The sensitivity adjustment module includes a comparator; The first input terminal of the comparator is connected to the first terminal of the single-photon avalanche diode, the second input terminal of the comparator is connected to the sensitivity control signal, and the output terminal of the comparator is connected to the output terminal of the sensitivity adjustment module.

11. The photosensitive pixel circuit according to claim 10, characterized in that, The comparator is a non-inverting comparator. It lowers 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. Alternatively, the comparator can be an inverting comparator, increasing the voltage of the sensitivity control signal to make the sensitivity adjustment module work in the first working state; and decreasing the voltage of the sensitivity control signal to make the sensitivity adjustment module work in the second working state.

12. An image sensor, characterized in that, Includes the photosensitive pixel circuit as described in any one of claims 1 to 11.

13. The image sensor according to claim 12, characterized in that, Includes multiple photosensitive pixel circuits, and the multiple photosensitive pixel circuits are arranged in an array; The image sensor also includes a controller for generating the sensitivity control signal, and the controller is connected to the second input terminal of the sensitivity adjustment module of the plurality of photosensitive pixel circuits.

14. An electronic device, characterized in that, Includes the image sensor described in claim 12 or 13.

Images