An image sensor protection system and protection method based on rapid perception and feedback control

Abstract

The present invention relates to an image sensor protection system and a protection method based on rapid sensing and feedback control, belonging to the technical field of image sensor protection. The system includes a photoelectric detection module, a high-speed comparison module, and an active feedback control module. Among them, the photoelectric detection module is connected to an image sensor through the high-speed comparison module and the active feedback control module in sequence; the photoelectric detection module includes a transimpedance amplifier circuit, a bias voltage adjustment circuit, a temperature compensation circuit, and a photodetector. The photodetector is respectively connected to the transimpedance amplifier circuit, the bias voltage adjustment circuit, and the temperature compensation circuit, and the transimpedance amplifier circuit is connected to the high-speed comparison module. The present invention combines rapid sensing and feedback control. While realizing rapid sensing and intensity judgment of laser irradiation, it executes the feedback control protection program of the image sensor, avoiding the image sensor from still being in the working state when being irradiated by laser, and realizing rapid protection of the image sensor.

Description

Technical Field

[0001] The present invention relates to an image sensor protection system and a protection method based on rapid perception and feedback control, belonging to the technical field of image sensor protection. Background Art

[0002] Currently, mainstream image sensors have the characteristics of low power consumption, high integration, and fast imaging speed, and are widely used in digital cameras, mobile phones, drones, security monitoring, autonomous driving and other fields. As the core component of an optoelectronic imaging system, the principle of an image sensor is based on the photoelectric effect of a photodiode. When the image sensor is working, the pixel unit is under a certain reverse bias voltage. After external photons irradiate the pixel array, corresponding charges will be generated in the pixel unit. These charges will accumulate within the exposure time of the image sensor. After the exposure ends, the accumulated charge signal will be amplified and read out, and finally converted into digital image information. However, with the popularization of technologies such as vehicle-mounted lidar and stage laser lights, there have been many incidents of image sensor damage caused by laser irradiation in life. Although in these scenarios, the laser irradiation power is relatively low and there are few cases of long-term continuous irradiation of the same target, starting from the working principle of the image sensor, when the environment is relatively dark, the image sensor will be in a high-gain and long-exposure working state. At this time, the pixel unit will accumulate a large amount of charges within the exposure time due to the dual effects of the high optical gain of the imaging lens and the applied working bias voltage, resulting in different degrees of damage such as dot damage, line damage, and cross damage.

[0003] To avoid damage to the image sensor caused by laser irradiation, existing image sensor protection technologies are mainly based on protective materials, computational imaging, holographic optics, and mechanical structures, etc. However, these technologies all have certain limitations when used for laser protection of consumer imaging devices. The image sensor protection methods based on protective materials include nonlinear optical laser protection technology and phase change material laser protection technology. Essentially, these protection methods regulate the laser irradiation intensity by changing the transmittance and reflectivity of the materials, which will affect the imaging clarity to a certain extent. The image sensor protection methods based on computational imaging require the design and high-precision processing of optical field modulation components, and at the same time, the collected images need to be decoded to restore the real images. Therefore, there are limitations in imaging speed and imaging quality, and they are not suitable for the protection of image sensors in consumer imaging devices. The image sensor protection methods based on holographic optics need to reflect specific wavelength lasers by adjusting the spacing of hologram interference fringes to achieve the protection of the image sensor. Once this holographic grating is prepared, the spacing of the interference fringes cannot be changed. Therefore, this method can only protect against lasers of a single specific wavelength within a certain incident range when the wavelength of the irradiated laser is known. The image sensor protection methods based on mechanical structures have a high damage threshold and can be actively controlled, but their structures are relatively complex, and the switching response speed is relatively slow, and the switching time is generally in the order of ms. For this reason, the present invention is proposed. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides an image sensor protection system and protection method based on rapid sensing and feedback control. By rapidly sensing laser irradiation and rapidly feedback controlling the image sensor, the process of laser energy accumulation during the exposure time is cut off, so as to realize the protection of the image sensors of consumer imaging devices in most living scenarios. Moreover, by using a photodetector with higher sensitivity, faster response speed, and wider response wavelength range to sense the laser, the protection level can be autonomously judged according to the laser intensity, and the image sensor protection program can be executed to realize the rapid feedback control of the working states of the image sensor and the photoelectric sensor.

[0005] This image sensor protection technology based on "sensing + control" is compatible with the existing imaging architecture, has less hardware restrictions on image sensors, etc., the realized high-speed and high-dynamic photoelectric detection and rapid feedback control logic have relatively low costs themselves, and at the same time can realize additional functions such as image sensor exposure control, electronic device screen brightness adjustment, and laser pulse echo signal reception, and has the characteristics of fast response speed, good compatibility, and wide application range.

[0006] The technical solution of the present invention is as follows:

[0007] An image sensor protection system based on fast perception and feedback control, comprising a photoelectric detection module, a high-speed comparison module and an active feedback control module. Among them, the photoelectric detection module is connected to an image sensor through the high-speed comparison module and the active feedback control module in sequence;

[0008] The photoelectric detection module includes a transimpedance amplifier circuit, a bias voltage adjustment circuit, a temperature compensation circuit and a photodetector. The photodetector is respectively connected to the transimpedance amplifier circuit, the bias voltage adjustment circuit and the temperature compensation circuit, and the transimpedance amplifier circuit is connected to the high-speed comparison module.

[0009] The photoelectric detection module realizes high-signal-bandwidth detection and is equipped with a supporting gain (bias voltage) adjustment circuit, a temperature compensation circuit and a transimpedance amplifier circuit; the high-speed comparison module has a low delay of the order of ns and can realize the functions of protection threshold adjustment and level standard conversion; the active feedback control module realizes high-speed feedback control of the exposure state of the image sensor and the gain setting of the photodetector, and can independently determine the protection state according to the laser intensity. Among them, the photoelectric detection module can adopt different implementation schemes according to different application devices.

[0010] According to the preference of the present invention, the bias voltage adjustment circuit controls the response of the photodetector to be quickly adjusted within a high dynamic range, and the sensitivity of the photodetector is stronger than that of the photodiode in the image sensor, realizing sensitive perception of laser irradiation in a complex environment. During the protection process, the temperature compensation circuit real-time collects the temperature of the photodetector and dynamically adjusts the bias voltage at both ends of the photodetector according to the temperature characteristics of the selected photodetector to make up for the gain change of the photodetector caused by temperature and realize the stability of the gain coefficient of the photodetector. The transimpedance amplifier circuit adopts a transimpedance amplifier (TIA), and converts and amplifies the level signal generated by the photodetector into a voltage signal by configuring the circuit gain of the transimpedance amplifier, and can realize a high conversion gain and high speed and high bandwidth.

[0011] According to the preference of the present invention, the high-speed comparison module adopts a voltage comparison circuit, which can shape the pulse signal, and there is a weak delay as low as the order of ns between the output signal and the input signal. The active feedback control module selects a high-speed logic chip. On the one hand, it focuses on optimizing the control processes of the image sensor and the photodetector, reducing the program logic delay and improving the response speed of the protection operation; on the other hand, after starting the protection mode, it is necessary to realize the independent judgment of the laser intensity and perform feedback control on the image sensor and the photodetector according to the laser intensity to set different levels of protection modes.

[0012] Preferably, according to the present invention, the active feedback control module is responsible for setting parameters such as the image sensor integration time and image frame rate, and realizes the reading of the collected image data. In addition, the active feedback control module can call the photodetector to realize the perception of the ambient light intensity, which is used to assist the screen brightness adjustment or automatic exposure control of electronic devices such as mobile phones and cameras. Alternatively, a TDC (time to digital converter) module can be added to the control module to cooperate with the laser focus and laser ranging modules in the imaging device to realize the reception of pulse echo signals.

[0013] The protection method of the image sensor protection system based on rapid perception and feedback control comprises the following steps:

[0014] (1) When the photodetector senses laser irradiation, the photodetector generates a high-speed level signal, and the transimpedance amplifier circuit converts and amplifies the high-speed level signal into a voltage signal. The high-speed comparison module determines whether the voltage signal reaches the laser protection threshold. If the threshold is reached, a trigger signal that meets the digital circuit logic level standard is output to the active feedback control module. The active feedback control module quickly executes the image sensor integration termination and reset operations, and controls the photodetection module to reduce the photodetector gain;

[0015] (2) The active feedback control module will continue to detect the trigger signal of the high-speed comparison module. If the trigger signal persists, the image sensor will be reset and the high-intensity protection mode will be turned on, and the photodetector gain will be maintained at a low gain state. If the trigger signal disappears, the photodetector gain will be increased first, the normal protection mode will be restored, and then the image sensor exposure state will be restored. (High-intensity protection and normal-intensity protection are for setting the gain of the photodetector in terms of the intensity of the irradiated laser. In the high-intensity protection mode, the photodetector needs to be set to a low gain state due to the excessive laser intensity to prevent the photodetector from being damaged due to the excessive laser intensity and excessive gain. In the normal protection mode, the initial gain of the photodetector is restored to sensitively sense laser irradiation. When the photodetector gain coefficient is greater than 5, it is in high gain mode; when the photodetector gain coefficient is less than 2, it is in low gain mode.)

[0016] According to the preferred embodiment of the present invention, in step (1), the protection threshold calibration process is as follows: first, the photoelectric detection module is set to a high gain state, using about 5×10 -3 W / cm 2 The light of illumination is used to simulate sunlight and car lights, and at the same time, the trigger threshold of the high-speed comparison module is increased to ensure that the protection program is not triggered and prevent the program from being started by mistake;

[0017] Secondly, at high gain, using about 1W / cm 2Illuminance light is used to simulate the illumination of on-vehicle lidar, and at the same time, the trigger threshold of the high-speed comparison module is reduced to ensure that the protection program can be triggered. At this time, stronger lasers can also effectively trigger the threshold;

[0018] Finally, the photoelectric detection module is set to a low-gain state, and light with an illuminance of about 10 W / cm 2 is used to simulate the illumination of stage laser lights. At the same time, the trigger threshold of the high-speed comparison module is reduced to ensure that the threshold can be triggered under strong laser illumination, and it will not be triggered under weak laser illumination, realizing different levels of protection programs.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. The present invention combines rapid sensing and feedback control. While achieving rapid sensing and intensity judgment of laser illumination, it executes the feedback control protection program of the image sensor, avoiding the image sensor still being in a high-gain working state when being irradiated by a laser, and realizing rapid protection of the image sensor.

[0021] 2. The present invention solves problems such as gain control and temperature drift of the photodetector, ensures that the photodetector always works in the best working state, and realizes a rapid response to laser illumination signals.

[0022] 3. The present invention optimizes the control logic of the control module, reduces logic delay, ensures that the integration state of the image sensor is aborted at the first time when laser illumination is sensed, and performs protection operations such as resetting the image sensor and reducing the bias voltage of the photodetector; the active feedback control module continuously detects the output state of the photodetector, and combines the gain setting of the photodetector to judge the laser intensity, and independently determines the protection level of the image sensor and the photodetector.

[0023] 4. The image sensor protection technology proposed by the present invention is based on the protection logic of "sensing + control", has less hardware restrictions on imaging devices, and can be well compatible with existing imaging devices in architecture; compared with the image sensor protection method based on computational imaging, it does not affect the imaging speed and imaging quality of existing imaging devices; compared with the image sensor protection method based on protection materials, it has a higher damage threshold. By adopting a wide-band, high-speed, and high-dynamic-range photodetector, a rapid response to laser illumination can be achieved; compared with the image sensor protection method based on a mechanical structure, it has a faster response speed; compared with the image sensor protection method based on holographic optics, it is not limited by the laser band and has the ability to protect against wide-band lasers covering visible to infrared. While the photodetector realizes rapid sensing of lasers, it can also realize additional functions such as exposure control of the image sensor, brightness adjustment of the electronic device screen, and reception of laser pulse echo signals; compared with protection materials, gratings, light field modulation elements, or special mechanical structures, the photodetector has a lower cost and is widely used. Description of the Drawings

[0024] Figure 1 is a schematic diagram of the present invention;

[0025] Figure 2 is a flowchart of the image sensor protection program of the present invention;

[0026] Figure 3 is a flowchart for calibrating the protection threshold of the image sensor of the present invention. Specific embodiments

[0027] The present invention will be further described below through embodiments in conjunction with the accompanying drawings, but not limited thereto.

[0028] Embodiment 1:

[0029] As Figure 1 shown, this embodiment provides an image sensor protection system based on fast sensing and feedback control, including a photoelectric detection module, a high-speed comparison module, and an active feedback control module. Among them, the photoelectric detection module is connected to an image sensor through the high-speed comparison module and the active feedback control module in sequence;

[0030] The photoelectric detection module includes a transimpedance amplifier circuit, a bias voltage adjustment circuit, a temperature compensation circuit, and a photodetector. The photodetector is respectively connected to the transimpedance amplifier circuit, the bias voltage adjustment circuit, and the temperature compensation circuit, and the transimpedance amplifier circuit is connected to the high-speed comparison module.

[0031] The photoelectric detection module realizes high-signal-bandwidth detection and is equipped with a supporting gain (bias voltage) adjustment circuit, a temperature compensation circuit, and a transimpedance amplifier circuit; the high-speed comparison module has a low delay in the ns level and can realize the functions of protection threshold adjustment and level standard conversion; the active feedback control module realizes high-speed feedback control of the exposure state of the image sensor and the gain setting of the photodetector, and can also independently determine the protection state according to the laser intensity. Among them, the photoelectric detection module can adopt different implementation schemes according to different application devices.

[0032] A filter is installed in front of the photodetector to attenuate the laser intensity, prevent the photodetector from being damaged, and expand the gain adjustment range of the photodetector.

[0033] When applied to the protection of image sensors in low-light monitoring devices such as underground garages and night vision, since the image sensors in low-light monitoring devices have a high response rate and the response wavelength may cover the near-infrared band, the photoelectric detector can adopt an InGaAs (indium gallium arsenide) APD photodetector with a photosensitive surface element size of 200 μm, a wavelength response range of 400-1700 nm, and a cut-off frequency of 500 MHz. The signal bandwidth of the APD photodetector can be calculated according to the empirical formula by collecting the pulse fall time:

[0034]

[0035] Among them, BW is the output signal bandwidth of the InGaAs APD photodetector, and T fall is the APD pulse fall time. Therefore, when the bandwidth of the InGaAs APD photodetection module is 500 MHz, the corresponding pulse response time is 700 ps.

[0036] The gain of the APD detector is regulated by the reverse bias voltage at both ends. The InGaAs APD bias voltage regulation circuit mainly controls the magnitude of the APD reverse bias voltage through a DAC (digital-to-analog converter) and a non-inverting operational amplifier circuit. Since the monitoring device has less restrictions on volume and power consumption, a 12-bit high-precision and high-linearity DAC is used. The SPI communication protocol is used for data instruction transmission between the DAC and the control chip. To improve the APD gain switching speed, the DAC encodings for the high and low gain modes can be set to 1111 11111111 and 0111 1111 1111, and the corresponding output voltage values V bctrl are 4095 / 4096 V REF and 2047 / 4096 V REF . The non-inverting operational amplifier circuit uses a rail-to-rail single-channel input operational amplifier, and the output voltage of the circuit is:

[0037]

[0038] Among them, V b output is the bias voltage of the APD, and V bctrl input is the DAC output voltage. According to the APD gain curve and the resistance values of R1 and R2, the amplification factor of the operational amplifier circuit can be set to about 10 to 20 times.

[0039] The gain of the InGaAs APD is greatly affected by temperature. The temperature compensation circuit adjusts the bias voltage at both ends of the APD by collecting the real-time temperature of the APD to make up for the APD gain change caused by temperature change. First, the PT1000 temperature sensor is closely attached to the surface of the APD package, and the ADC (analog-to-digital converter) collects the voltage signal with temperature information and sends it to the control chip. The control chip obtains the real-time temperature of the APD through a look-up table, and then the control chip controls the bias voltage regulation circuit to maintain the APD gain by referring to the APD temperature-gain-bias voltage parameter table.

[0040] During the protection process, the temperature compensation circuit continuously collects the temperature of the InGaAs APD. When the temperature rises, the bias voltage at both ends of the photodetector is controlled to increase synchronously; when the temperature drops, the bias voltage at both ends of the InGaAs APD is controlled to decrease synchronously. The temperature compensation circuit is used to make up for the detector gain change caused by temperature and achieve the stability of the photodetector gain coefficient.

[0041] The transimpedance amplifier circuit converts and amplifies the level signal generated by the APD into a voltage signal. Its gain setting should ensure low circuit delay while having a high gain. The transimpedance discharge circuit is mainly implemented based on the TIA (transimpedance amplifier), and a TIA with low noise, high gain, and high bandwidth characteristics can be selected. The photocurrent signal generated by the InGaAs APD photodetector is used as the input of the TIA. The transimpedance value is configured through the GAIN pin of the TIA chip. The internal input is clamped, and the circuit selects a gain of 50 KΩ. The TIA chip has a built-in output impedance matching of 50 Ω. Then, the differential signal is converted into a single-ended signal through a balun and output after impedance conversion.

[0042] The high-speed comparison module uses a voltage comparator. The two input terminals of the comparator are respectively connected to the output of the photodetection module and the comparison voltage UREF. When the output voltage of the photodetection module is higher than UREF, the comparator outputs a high level VOH; when the output voltage of the photodetection module is lower than UREF, the comparator outputs a low level VOL.

[0043] The active feedback control module uses a high-speed logic chip based on the ZYNQ architecture. The ARM part is used for temperature compensation control and bias control of the photodetector to achieve rapid adjustment of the gain coefficient of the photodetector; the FPGA part is used to execute the image sensor protection program and drive the image sensor, and parameters such as integration time and image frame rate can be set. The trigger signal generated by the high-speed comparison module is directly input to the FPGA, and in the FPGA, by optimizing the timing logic, shortening the critical path, and reducing the signal transmission path length in layout and wiring, the protection program delay can be effectively reduced to achieve high-speed control of the image sensor. In actual tests, when the FPGA uses a 40 MHz clock, the execution time of the image sensor protection program is about 100 ns.

[0044] Embodiment 2:

[0045] An image sensor protection system based on fast sensing and feedback control for devices such as mobile phones, cameras, and driverless vision sensors has the structure as described in Embodiment 1. The difference is that devices such as mobile phones, cameras, and driverless vision sensors have relatively low requirements for response rate and response speed, but have greater limitations on the power consumption and cost of the photodetector. Therefore, a Si (silicon) PIN photodiode with a wavelength response range of 400 - 1100 nm, a cut-off frequency of 50 MHz, and a photosensitivity of 0.7 A / W is used. The signal bandwidth of the PIN photodiode can be calculated according to the empirical formula by collecting the pulse fall time:

[0046]

[0047] Among them, BW is the output signal bandwidth of the Si PIN photodiode, Tfall is the pulse falling edge time. Therefore, when the bandwidth of the SiPIN photodiode photodetection module is 50 MHz, the corresponding pulse response time is 7 ns.

[0048] The bias voltage adjustment range of the Si PIN photodiode is small, and the requirement for voltage accuracy is low. The inverting operational amplifier circuit can be simplified, and a low-power 8-bit DAC (digital-to-analog converter) is used to achieve bias voltage adjustment. The SPI communication protocol is used for data instruction transmission between the DAC and the control chip. To improve the gain switching speed of the photodetector, the DAC encodings for the high and low gain modes can be set to 11111111 and 0111 1111, corresponding to the output voltage values V bctrl are 255 / 256V REF and 127 / 256V REF . At the same time, since the Si PIN photodiode is less affected by temperature, the temperature compensation circuit can be simplified.

[0049] The transimpedance amplifier circuit uses a transimpedance amplifier (TIA). The level signal generated by the photodetector is converted and amplified into a voltage signal by configuring the circuit gain of the transimpedance amplifier. It can achieve high gain while having low circuit delay. The high-speed comparison module uses a voltage comparison circuit, and the active feedback control module selects a high-speed logic chip. The high-speed comparison module shapes the pulse signal, and the delay between the output signal and the input signal is as low as the ns level. The active feedback control module, on the one hand, focuses on optimizing the control processes of the image sensor and the photodetector, reducing the program logic delay, and improving the response speed of the protection operation; on the other hand, after starting the protection mode, it needs to achieve autonomous judgment of the laser intensity and perform feedback control on the image sensor and the photodetector according to the laser intensity to set different levels of protection modes.

[0050] The active feedback control module is responsible for setting parameters such as the integration time and image frame rate of the image sensor, and realizing the readout of the acquired image data. In addition, the active feedback control module can call the photodetector to sense the ambient light intensity, which is used to assist in adjusting the screen brightness or automatic exposure control of electronic devices such as mobile phones and cameras. Or a TDC (time-to-digital converter) module can be added to the control module to cooperate with the laser focusing and laser ranging modules in the imaging device to receive the pulse echo signal.

[0051] The protection method of the above image sensor protection system based on fast sensing and feedback control is as Figure 2 shown, and the steps are as follows:

[0052] (1) When the photodetector senses laser irradiation, the photodetector generates a high-speed level signal. The transimpedance amplifier circuit converts and amplifies the high-speed level signal into a voltage signal. The high-speed comparison module determines whether the voltage signal reaches the laser protection threshold. If the threshold is reached, a trigger signal that conforms to the digital circuit logic level standard is output to the active feedback control module. The active feedback control module quickly executes the integration suspension and reset operations of the image sensor, and controls the photodetection module to reduce the gain of the photodetector.

[0053] (2) The active feedback control module continuously detects the trigger signal of the high-speed comparison module. If the trigger signal persists, it maintains the reset state of the image sensor and activates the high-intensity protection mode, maintaining the gain of the photodetector at a low-gain state. If the trigger signal disappears, it first increases the gain of the photodetector, restores the normal protection mode, and then restores the exposure state of the image sensor. (High-intensity protection and normal-intensity protection are for the intensity of the irradiated laser, and the gain of the photodetector is set. In the high-intensity protection mode, due to the excessive laser intensity, the photodetector needs to be set in a low-gain state to prevent the photodetector from being damaged due to excessive laser intensity and high gain. In the normal protection mode, the initial gain of the photodetector is restored to sensitively detect laser irradiation. When the gain coefficient of the photodetector is greater than 5, it is in the high-gain mode; when the gain coefficient of the photodetector is less than 2, it is in the low-gain mode.)

[0054] In step (1), the process of calibrating the protection threshold is as follows: First, set the photodetection module to the high-gain state, and use light with an illuminance of about 5×10 -3 W / cm 2 to simulate sunlight and vehicle headlight irradiation. At the same time, increase the trigger threshold of the high-speed comparison module to ensure that the protection program is not triggered and prevent the program from starting accidentally.

[0055] Secondly, in the high-gain state, use light with an illuminance of about 1W / cm 2 to simulate the irradiation of vehicle-mounted lidar. At the same time, reduce the trigger threshold of the high-speed comparison module to ensure that the protection program can be triggered, and stronger lasers can also effectively trigger the threshold.

[0056] Finally, set the photodetection module to the low-gain state, and use light with an illuminance of about 10W / cm 2 to simulate the irradiation of stage laser lights. At the same time, reduce the trigger threshold of the high-speed comparison module to ensure that the threshold can be triggered under strong laser irradiation and not be triggered under weak laser irradiation, realizing different levels of protection programs. The calibration process is as Figure 3 shown.

[0057] The above are only embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A protection method for an image sensor protection system based on fast perception and feedback control, characterized in that The protection system includes a photoelectric detection module, a high-speed comparison module and an active feedback control module, wherein the photoelectric detection module is connected to an image sensor through the high-speed comparison module and the active feedback control module in sequence; the photoelectric detection module includes a transimpedance amplifier circuit, a bias adjustment circuit, a temperature compensation circuit and a photodetector, wherein the photodetector is respectively connected to the transimpedance amplifier circuit, the bias adjustment circuit and the temperature compensation circuit, and the transimpedance amplifier circuit is connected to the high-speed comparison module; The bias voltage regulating circuit controls the magnitude of the reverse bias voltage of the photodetector through a digital-to-analog converter and a common-direction operational amplifier circuit; The protection method of the image sensor protection system based on rapid perception and feedback control comprises the following steps: (1) When the photodetector senses laser irradiation, it generates a high-speed level signal. The transimpedance amplifier circuit converts and amplifies the high-speed level signal into a voltage signal. The high-speed comparison module determines whether the voltage signal reaches the laser protection threshold. If the threshold is reached, a trigger signal that meets the digital circuit logic level standard is output to the active feedback control module. The active feedback control module quickly executes the image sensor integration termination and reset operations, and controls the photodetection module to reduce the photodetector gain. (2) The active feedback control module will continuously detect the trigger signal of the high-speed comparison module. If the trigger signal continues to exist, the image sensor will be kept in the reset state and the photodetector gain will be maintained in the low gain state. If the trigger signal disappears, the photodetector gain will be increased first and then the image sensor exposure state will be restored.

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