Reading circuit with switchable pixel structure and control method thereof

Abstract

The invention discloses a readout circuit with a switchable pixel structure and a control method thereof, and the readout circuit comprises a photosensitive unit which is used for converting an optical signal into a light current signal; the switching unit is used for transmitting the light current signal output by the light sensing unit to the first reading unit or the second reading unit; the first reading unit is used for integrating the light current signal generated by the light sensing unit and outputting a first voltage signal; the second reading unit is used for integrating the photocurrent signal generated by the photosensitive unit and outputting a second voltage signal when the first voltage signal output by the first reading unit is saturated in advance; and the readout switch unit is used for transmitting the first voltage signal output by the first readout unit or the second voltage signal output by the second readout unit to the column output bus. The light current signals generated by the light sensing unit are distributed to different read-out units for processing through the switching unit, so that the image sensor can maintain high-quality signal output under a wider illumination condition.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric imaging detection, and in particular to a readout circuit with switchable pixel structure and a control method thereof. Background Art

[0002] In the field of optoelectronic imaging technology, photodetectors are core components whose performance directly determines the overall performance of the imaging system. After receiving incident light, photodetectors generate corresponding photocurrent signals, which need to be converted into processable voltage signals by signal processing circuits to achieve image acquisition and reconstruction. As a key link in this conversion process, the design of the readout circuit directly affects the key performance indicators of the optoelectronic imaging system, such as sensitivity, dynamic range, noise level and linearity.

[0003] Traditional readout circuit architectures often use a single pixel unit structure, which greatly limits its application scenarios. At the same time, due to the performance constraints of various single-structure pixel units, they often cannot take into account performance characteristics such as integration time, photocurrent size, injection efficiency, linearity, and noise at the same time.

[0004] For example: the pixel unit of the self-integration readout circuit (SI) is composed of only one MOS switch, so its layout area can be made very small. However, the integral capacitor of the SI pixel unit is the parasitic capacitor of the detector. Since the parasitic capacitor of the detector is nonlinear, the bias voltage of the detector will change significantly with the change of the photocurrent, causing the output signal to have extremely poor linearity; the pixel unit of the direct injection readout circuit (DI) is composed of an injection tube, an integral capacitor and a reset tube. Under medium and high intensity radiation conditions, the transconductance of the injection tube is large and has good injection efficiency. However, in application scenarios with low radiation intensity and small photocurrent, the transconductance of the injection tube becomes smaller and the input impedance becomes larger. The injection efficiency will be significantly reduced, so the DI type pixel unit structure is more suitable for medium and long wave infrared detectors with large photocurrent; the pixel unit of the source follower type readout circuit (SFD) adds a source follower structure on the basis of the SI type readout circuit pixel unit, which enhances the driving ability. Its integral capacitor is composed of the parasitic capacitance of the photosensitive device and the parasitic capacitance of the source follower input tube. Since the parasitic capacitance of the detector and the parasitic capacitance of the source follower input tube are determined by their respective process conditions, they cannot be accurately controlled, and the bias voltage of the detector will also change continuously with the integration process of the photocurrent, which also affects the linearity of the output signal; the capacitor transimpedance amplifier type readout circuit (CT The pixel unit of CTIA is composed of an operational amplifier and an integrating capacitor controlled by a reset switch, which can achieve stable control of the detector bias and has a low detector input impedance. At the same time, the charge conversion gain can be regulated by adjusting the capacitance of the integrating capacitor. It can also have good linear output under weak light conditions and has strong applicability. However, when the integration time is long, the small integrating capacitor of CTIA will be saturated in advance, resulting in a significant impact on the linear dynamic range of the readout circuit. At the same time, when the integration time is long, CTIA will have higher output noise. Summary of the invention

[0005] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a readout circuit with switchable pixel structure and a control method thereof which can overcome the limitations of a readout circuit with a single pixel unit structure.

[0006] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide a readout circuit with switchable pixel structure, comprising:

[0007] A photosensitive unit, used for converting a light signal into a photocurrent signal;

[0008] A switching unit, used for transmitting the photocurrent signal output by the photosensitive unit to the first readout unit or the second readout unit;

[0009] A first readout unit, used for integrating the photocurrent signal generated by the photosensitive unit and outputting a first voltage signal;

[0010] a second readout unit, configured to integrate the photocurrent signal generated by the photosensitive unit and output a second voltage signal when the first voltage signal output by the first readout unit is saturated in advance; and

[0011] The readout switch unit is used to transmit the first voltage signal output by the first readout unit or the second voltage signal output by the second readout unit to a column output bus.

[0012] Furthermore, the switching unit includes a first switch tube Φ CTIA And the second switch tube Φ SFD The optical signal input end of the photosensitive unit is used to receive the optical signal, and the photocurrent signal output end of the photosensitive unit is connected to the first switch tube Φ CTIA The photocurrent signal output end of the photosensitive unit is also electrically connected to the first photocurrent signal input end of the first readout unit, and the photocurrent signal output end of the photosensitive unit is also electrically connected to the first photocurrent signal input end of the first readout unit. SFD The first photocurrent signal input terminal of the second readout unit is electrically connected to the first end of the readout switch unit, and the second end of the readout switch unit is electrically connected to the column output bus.

[0013] Further, the photosensitive unit is defined as a photosensitive element VD, the photosensitive surface of the photosensitive element VD receives incident light to access the light signal, the positive electrode of the photosensitive element VD is connected to the power supply voltage, and the negative electrode of the photosensitive element VD is connected to the power supply voltage through the first switch tube Φ CTIA The negative electrode of the photosensitive element VD is also electrically connected to the first photocurrent signal input terminal of the first readout unit through the second switch tube Φ SFD The optical signal input terminal of the second readout unit is electrically connected to the second optical current signal input terminal of the second readout unit.

[0014] Furthermore, the first readout unit includes an operational amplifier AD, a first reset transistor Φ RS1 And the integrating capacitor C INT_CTIA The inverting input terminal of the operational amplifier AD and the first switch tube Φ CTIA The collector of the first switch tube Φ CTIA The emitter of the photosensitive element VD is electrically connected to the negative electrode; the output end of the operational amplifier AD is electrically connected to the first end of the readout switch unit, and the integral capacitor C INT_CTIA In parallel with the operational amplifier AD, the first reset tube Φ RS1 The emitter of the first switch tube Φ CTIAThe collector of the first reset transistor Φ RS1 The collector is electrically connected to the output end of the operational amplifier AD.

[0015] Furthermore, the second readout unit includes a second reset transistor Φ RS2 and a source follower SF; the second reset transistor Φ RS2 The collector of the second switch tube Φ SFD The collector of the second switch tube Φ SFD The emitter of the photosensitive element VD is electrically connected to the negative electrode, and the second reset tube Φ RS2 The emitter of the source follower SF is grounded; the input end of the source follower SF is connected to the second reset tube Φ RS2 The collector of the source follower SF is electrically connected, and the output end of the source follower SF is electrically connected to the first end of the readout switch unit.

[0016] Further, the readout switch unit is defined as a third switch tube Φ SEL , the third switch tube Φ SEL The emitter of the third switch tube Φ is electrically connected to the output end of the source follower SF and the output end of the operational amplifier AD respectively. SEL The collector is electrically connected to the column output bus.

[0017] In order to solve the above technical problems, another technical solution adopted by the present invention is: to provide a control method of a readout circuit with switchable pixel structure, using the readout circuit with switchable pixel structure, comprising the following steps:

[0018] enabling the first readout unit to integrate the photocurrent signal and output a first voltage signal;

[0019] determining whether a switching condition of the second readout unit is satisfied;

[0020] If the switching condition of the second readout unit is met, the control is switched to the second readout unit to integrate the photocurrent signal and output the second voltage signal; otherwise, the first readout unit is kept integrating the photocurrent signal.

[0021] Further, the switching condition of the second readout unit includes: the first voltage signal output by the first readout unit is saturated in advance;

[0022] The method for determining whether a switching condition of the second readout unit is satisfied includes:

[0023] Draw a characteristic curve of the first voltage signal output by the first readout unit;

[0024] Observe whether the characteristic curve is saturated early;

[0025] If the characteristic curve is saturated in advance, it is determined that the switching condition of the second readout unit is met; otherwise, it is determined that the switching condition of the second readout unit is not met.

[0026] Furthermore, the method of causing the first readout unit to integrate the photocurrent signal and output the first voltage signal includes:

[0027] Disconnect the first switch Φ CTIA , and close the first reset tube Φ RS1 , to convert the integrating capacitor C INT_CTIA The charge in the body is discharged cleanly;

[0028] The first reset transistor Φ RS1 Open and close the first switch tube Φ CTIA , so as to connect the first readout unit and the photosensitive unit, through the integration capacitor C INT_CTIA Integrate the photocurrent signal generated by the photosensitive unit;

[0029] Disconnect the first switch Φ CTIA , and close the third switch tube Φ SEL , to output a first voltage signal to the column transmission bus.

[0030] Further, the method of controlling the switching to the second readout unit to integrate the photocurrent signal and output the second voltage signal includes:

[0031] Disconnect the second switch Φ SFD , and close the second reset tube Φ RS2 , reset the voltage at the input terminal of the source follower SF to the ground potential GND to clear the previous integration result;

[0032] Disconnect the second reset tube Φ RS2 , and close the second switch tube Φ SFD , so as to conduct the second readout unit with the photosensitive unit, wherein the second readout unit integrates the photocurrent signal generated by the photosensitive unit;

[0033] Disconnect the second switch Φ SFD , and close the third switch tube Φ SEL , to output a second voltage signal to the column transmission bus.

[0034] The readout circuit with switchable pixel structure and the control method thereof of the present invention have at least the following beneficial effects: the present invention can select a suitable readout unit according to different application scenarios through the switchable pixel structure, and realizes switching to the second readout unit for integration when the voltage signal output by the first readout unit is saturated in advance, thereby expanding the dynamic range of the readout circuit, enabling the circuit to cope with signal reading requirements under different light intensities and improving the adaptability of the circuit; when the photocurrent signal of the photosensitive element is weak, the bias voltage needs to be strictly controlled, and the injection efficiency is required to be high, high-quality injection efficiency and linearity can be obtained by reasonably designing the first readout unit; under the condition of strong light or long-term integration, the second readout unit can provide a more stable signal output and reduce noise; through simple switch control, switching between different readout units can be achieved to meet different application requirements; at the same time, the switchable readout unit design also helps to reduce the risk of failure of the entire system due to failure of a single unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0036] Figure 1 It is a structural block diagram of an embodiment of a readout circuit with switchable pixel structure according to the present invention.

[0037] Figure 2 A circuit diagram of an embodiment of a readout circuit with switchable pixel structure according to the present invention.

[0038] Figure 3 The flowchart is a method for controlling a readout circuit with switchable pixel structure according to an embodiment of the present invention.

[0039] Figure 4 This is an equivalent circuit diagram of the switchable readout circuit of the pixel structure of the present invention when the first readout unit is working.

[0040] Figure 5 is a characteristic curve diagram of the first voltage signal output by the first readout unit.

[0041] Figure 6 This is an equivalent circuit diagram of the switchable readout circuit of the pixel structure of the present invention when the second readout unit is working.

[0042] Figure 7 is a characteristic curve diagram of the second voltage signal output by the second readout unit. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings.

[0044] See also Figure 1 and Figure 2 The readout circuit with switchable pixel structure of the present invention comprises a photosensitive unit 1, a switching unit 2, a first readout unit 3, a second readout unit 4 and a readout switch unit 5. The light signal input end of the photosensitive unit 1 is connected to the light signal and then converts the light signal into a photocurrent signal; the photocurrent output end of the photosensitive unit 1 is electrically connected to the first photocurrent signal input end of the first readout unit 3 and the second photocurrent signal input end of the second readout unit 4 through the switching unit 2. The switching unit 2 is used to transmit the first photocurrent signal output by the photosensitive unit 1 to the first readout unit 3 or the second readout unit 4; the first readout unit 3 is used to integrate the photocurrent signal generated by the photosensitive unit 1 and output a first voltage signal; the second readout unit 4 is used to integrate the photocurrent signal generated by the photosensitive unit 1 and output a second voltage signal when the first voltage signal output by the first readout unit 3 is saturated in advance. The first voltage signal output end of the first readout unit 3 and the second voltage signal output end of the second readout unit 4 are both electrically connected to the first end of the readout switch unit 5, and the second end of the readout switch unit 5 is electrically connected to the column output bus; the readout switch unit 5 is used to transmit the first voltage signal output by the first readout unit 3 or the second voltage signal output by the second readout unit 4 to the column output bus.

[0045] The photosensitive unit 1 is used to convert the light signal into a photocurrent signal. The photosensitive unit 1 is defined as a photosensitive element VD, and the photosensitive surface of the photosensitive element VD serves as the light signal input end of the photosensitive unit 1 to receive incident light to access the light signal. The positive electrode of the photosensitive element VD is connected to the power supply voltage, and the negative electrode of the photosensitive element serves as the photocurrent signal output end of the photosensitive unit 1 and is electrically connected to the first readout unit 3 and the second readout unit 4 through the switching unit 2.

[0046] The switching unit 2 is used to transmit the photocurrent signal output by the photosensitive unit 1 to the first readout unit 3 or the second readout unit 4. The switching unit 2 includes a first switch tube Φ CTIA And the second switch tube Φ SFD , the first switch tube Φ CTIA The emitter of is electrically connected to the negative electrode of the photosensitive element VD, and the first switch tube Φ CTIA The collector of the second switch tube Φ is electrically connected to the first photocurrent signal input terminal of the first readout unit 3 to transmit the photocurrent signal to the first readout unit 3; SFD The emitter of is electrically connected to the negative electrode of the photosensitive element VD, and the second switch tube Φ SFD The collector of the first switch tube Φ is electrically connected to the second photocurrent signal input terminal of the second readout unit 4 to transmit the photocurrent signal to the second readout unit 4. CTIA And the second switch tube Φ SFD, realizing the switching of the photocurrent signal between the first readout unit 3 and the second readout unit 4. When the first switch tube is opened and the second switch tube is closed, the photocurrent signal is transmitted to the second readout unit 4; when the first switch tube is closed and the second switch tube is opened, the photocurrent signal is transmitted to the first readout unit 3.

[0047] The first readout unit 3 is used to integrate the photocurrent signal generated by the photosensitive unit 1 and output a first voltage signal. The first readout unit 3 includes a first reset transistor Φ RS1 , operational amplifier AD and integrating capacitor C INT_CTIA The inverting input terminal of the operational amplifier AD is used as the first photocurrent signal input terminal of the first readout unit 3 and the first switch tube Φ CTIA The output end of the operational amplifier AD is electrically connected to the first end of the readout switch unit 5 as the first voltage signal output end of the first readout unit 3, and the photocurrent signal is electrically connected to the first end of the readout switch unit 5 through the first switch tube Φ CTIA Enter the inverting input terminal of the operational amplifier AD; the integrating capacitor C INT_CTIA Connected in parallel with the operational amplifier AD, the photocurrent signal is integrated; the first reset tube Φ RS1 The emitter of the first switch tube Φ CTIA The collector of the first reset transistor Φ RS1 The collector is electrically connected to the output terminal of the operational amplifier AD, and is used to reset the circuit to ensure that the circuit is in an initial state before each integration. When the photocurrent signal is weak or the integration time is short, that is, the first readout unit 3 will not be saturated in advance due to a large photocurrent signal or a long integration time, the first readout unit 3 is used to integrate the photocurrent signal. The injection efficiency η of the first readout unit 3 is calculated as follows:

[0048]

[0049] Among them, C PD Represents the parasitic capacitance of the photosensitive element VD, R PD Represents the parasitic resistance of the photosensitive element VD, A v represents the open-loop gain of operational amplifier AD, t INT Indicates the integration time, C INT_CTIA represents the integral capacitance. The calculation formula of the nonlinearity S of the first readout unit 3 is:

[0050]

[0051] In this embodiment, the integration time t of the first readout unit 3 is comprehensively designed. INT , Integral capacitor C INT_CTIA The capacitance value and the open-loop gain A of the operational amplifier v , high quality injection efficiency and linearity can be obtained.

[0052] The second readout unit 4 is used to integrate the photocurrent signal generated by the photosensitive unit 1 and output a second voltage signal when the first voltage signal output by the first readout unit 3 is saturated in advance. The second readout unit 4 includes a second reset transistor Φ RS2 And source follower SF; second reset tube Φ RS2 The collector of the second photocurrent signal input terminal of the second readout unit 4 is connected to the second switch tube Φ SFD The collector of the second reset transistor Φ RS2 The emitter of the source follower SF is grounded; the input end of the source follower SF is connected to the second reset tube Φ RS2 The output end of the source follower SF is electrically connected to the collector of the second readout unit 4, and the output end of the source follower SF is electrically connected to the first end of the readout switch unit 5 as the second voltage signal output end of the second readout unit 4. The photocurrent signal passes through the second switch tube Φ SFD Enter the second reset tube Φ RS2 The collector of the photosensitive element VD outputs the second voltage signal through the output terminal of the source follower SF. The source follower SF provides a buffering effect to reduce signal loss. The second readout unit 4 is suitable for signal reading in a strong light environment. When a longer integration time or a larger integrated photocurrent signal is required, the second readout unit can be used to reduce noise. In this embodiment, the integral capacitor of the second readout unit 4 is the parasitic capacitor C of the photosensitive element VD. PD And the parasitic capacitance C of the input tube of the source follower SF SF The voltage at the input of the source follower SF changes with the integration process, and the voltage gain of the source follower SF is:

[0053]

[0054] Among them, g m is the transconductance of the source follower SF input tube, g mb It is the body effect transconductance of the source follower SF input tube.

[0055] The readout switch unit 5 is used to transmit the first voltage signal output by the first readout unit 3 or the second voltage signal output by the second readout unit 4 to the column output bus. The readout switch unit 5 is defined as a third switch tube Φ SEL , the third switch tube Φ SEL The emitter of the third switch tube Φ is used as the first end of the readout switch unit 5 and is electrically connected to the output end of the source follower SF and the output end of the operational amplifier AD respectively. SEL The collector of serves as the second end of the readout switch unit 5 and is electrically connected to the column output bus.

[0056] Another preferred embodiment of the present invention further discloses a control method for a readout circuit with switchable pixel structure, which is implemented based on the readout circuit with switchable pixel structure of the above embodiment, and includes a photosensitive unit 1, a switching unit 2, a first readout unit 3, a second readout unit 4 and a readout switch unit 5 having the same or similar structure as the above embodiment. Figure 3 , is a flow chart of an implementation method of a control method of a readout circuit with a switchable pixel structure of the present invention, and this implementation method specifically includes the following steps:

[0057] S1. Enable the first readout unit 3 to integrate the photocurrent signal and output a first voltage signal.

[0058] When the first readout unit 3 is working, the equivalent circuit diagram is as follows: Figure 4 Specifically, first, the first switch tube Φ is turned off. CTIA , and close the first reset tube Φ RS1 , to convert the integrating capacitor C INT_CTIA The charge in the tube is discharged cleanly; then, the first reset tube Φ RS1 Open and close the first switch tube Φ CTIA , so as to connect the first readout unit 3 and the photosensitive unit 1, through the integral capacitor C INT_CTIA The photocurrent signal generated by the photosensitive unit 1 is integrated; after the integration time is over, the first switch tube Φ is turned off. CTIA , stop injecting photocurrent; finally, close the third switch tube Φ SEL The first voltage signal is output to the column transmission bus for subsequent circuit processing. Figure 5 , is a characteristic curve diagram of the first voltage signal output by the first readout unit 3. It can be seen from the figure that the first readout unit 3 has a good output effect when working under the conditions of weak photocurrent and short integration time.

[0059] S2. Determine whether the switching condition of the second readout unit 4 is met.

[0060] Specifically, the switching condition of the second readout unit 4 includes: the first voltage signal output by the first readout unit 3 is saturated in advance. Generally, a weak photocurrent or a short integration time will cause the first voltage signal output by the first readout unit 3 to be saturated in advance. The method for determining whether the switching condition of the second readout unit 4 is met includes: drawing a characteristic curve of the first voltage signal output by the first readout unit 3, for details, please refer to Figure 5 ; Observe whether the characteristic curve is saturated early; if the characteristic curve is saturated early, it is determined that the switching condition of the second read-out unit 4 is met, otherwise, it is determined that the switching condition of the second read-out unit 4 is not met.

[0061] S3. If the switching condition of the second readout unit 4 is met, the control is switched to the second readout unit 4 to integrate the photocurrent signal and output a second voltage signal.

[0062] When the second readout unit 4 is working, the equivalent circuit diagram is as follows: Figure 6 Specifically, first, the second switch tube Φ is turned off. SFD , and close the second reset tube Φ RS2 , reset the voltage at the input end of the source follower SF to the ground potential GND to clear the previous integration result; then, disconnect the second reset tube Φ RS2 , and close the second switch tube Φ SFD , so as to connect the second readout unit 4 with the photosensitive unit 1, and the second readout unit 4 integrates the photocurrent signal generated by the photosensitive unit 1, and the integral capacitor of the second readout unit 4 is the parasitic capacitor C of the photosensitive element VD PD And the parasitic capacitance C of the input tube of the source follower SF SF After the integration time is over, the second switch tube Φ is disconnected SFD , stop injecting photocurrent; finally, close the third switch tube Φ SEL The second voltage signal is output to the column transmission bus for subsequent circuit processing. Figure 7 , is a characteristic curve diagram of the second voltage signal output by the second readout unit 4. It can be seen from the figure that the second readout unit 4 has a good output effect when working under the conditions of strong photocurrent and long integration time.

[0063] S4. Otherwise, keep the first readout unit 3 integrating the photocurrent signal.

[0064] The present invention, through the switchable pixel structure, can select a suitable readout unit according to different application scenarios, and realizes switching to the second readout unit for integration when the voltage signal output by the first readout unit is saturated in advance, thereby expanding the dynamic range of the readout circuit, enabling the circuit to cope with signal reading requirements under different light intensities, and improving the adaptability of the circuit; when the photocurrent signal of the photosensitive element is weak, the bias voltage needs to be strictly controlled, and the injection efficiency is required to be high, high-quality injection efficiency and linearity can be obtained by reasonably designing the first readout unit; in the case of strong light or long-term integration, the second readout unit can provide a more stable signal output and reduce noise; through simple switch control, switching between different readout units can be achieved to meet different application requirements; at the same time, the switchable readout unit design also helps to reduce the risk of failure of the entire system due to failure of a single unit.

[0065] The above embodiments only express the preferred embodiments of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A readout circuit with switchable pixel structure, characterized in that: include: A photosensitive unit, used for converting a light signal into a photocurrent signal; A switching unit, used for transmitting the photocurrent signal output by the photosensitive unit to the first readout unit or the second readout unit; A first readout unit, used for integrating the photocurrent signal generated by the photosensitive unit and outputting a first voltage signal; a second readout unit, configured to integrate the photocurrent signal generated by the photosensitive unit and output a second voltage signal when the first voltage signal output by the first readout unit is saturated in advance; as well as The readout switch unit is used to transmit the first voltage signal output by the first readout unit or the second voltage signal output by the second readout unit to a column output bus.

2. The readout circuit with switchable pixel structure as claimed in claim 1, characterized in that: The switching unit includes a first switch tube Φ CTIA And the second switch tube Φ SFD The optical signal input end of the photosensitive unit is used to receive the optical signal, and the photocurrent signal output end of the photosensitive unit is connected to the first switch tube Φ CTIA The photocurrent signal output end of the photosensitive unit is also electrically connected to the first photocurrent signal input end of the first readout unit, and the photocurrent signal output end of the photosensitive unit is also electrically connected to the first photocurrent signal input end of the first readout unit. SFD The first photocurrent signal input terminal of the second readout unit is electrically connected to the first end of the readout switch unit, and the second end of the readout switch unit is electrically connected to the column output bus.

3. The readout circuit with switchable pixel structure as claimed in claim 2, characterized in that: The photosensitive unit is defined as a photosensitive element VD, the photosensitive surface of the photosensitive element VD receives incident light to access the light signal, the positive electrode of the photosensitive element VD is connected to the power supply voltage, and the negative electrode of the photosensitive element VD is connected to the power supply voltage through the first switch tube Φ CTIA The negative electrode of the photosensitive element VD is also electrically connected to the first photocurrent signal input terminal of the first readout unit through the second switch tube Φ SFD The optical signal input terminal of the second readout unit is electrically connected to the second optical current signal input terminal of the second readout unit.

4. The readout circuit with switchable pixel structure as claimed in claim 3, characterized in that: The first readout unit includes an operational amplifier AD, a first reset transistor Φ RS1 And the integrating capacitor C INT_CTIA The inverting input terminal of the operational amplifier AD and the first switch tube Φ CTIA The collector of the first switch tube Φ CTIA The emitter of the photosensitive element VD is electrically connected to the negative electrode; the output end of the operational amplifier AD is electrically connected to the first end of the readout switch unit, and the integral capacitor C INT_CTIA In parallel with the operational amplifier AD, the first reset tube Φ RS1 The emitter of the first switch tube Φ CTIA The collector of the first reset transistor Φ RS1 The collector is electrically connected to the output end of the operational amplifier AD.

5. The readout circuit with switchable pixel structure as claimed in claim 4, characterized in that: The second readout unit includes a second reset transistor Φ RS2 and a source follower SF; the second reset transistor Φ RS2 The collector of the second switch tube Φ SFD The collector of the second switch tube Φ SFD The emitter of the photosensitive element VD is electrically connected to the negative electrode, and the second reset tube Φ RS2 The emitter of the source follower SF is grounded; the input end of the source follower SF is connected to the second reset tube Φ RS2 The collector of the source follower SF is electrically connected, and the output end of the source follower SF is electrically connected to the first end of the readout switch unit.

6. The readout circuit with switchable pixel structure as claimed in claim 5, characterized in that: The readout switch unit is defined as a third switch tube Φ SEL , the third switch tube Φ SEL The emitter of the third switch tube Φ is electrically connected to the output end of the source follower SF and the output end of the operational amplifier AD respectively. SEL The collector is electrically connected to the column output bus.

7. A control method for a readout circuit with a switchable pixel structure, using the readout circuit with a switchable pixel structure as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: enabling the first readout unit to integrate the photocurrent signal and output a first voltage signal; determining whether a switching condition of the second readout unit is satisfied; If the switching condition of the second readout unit is met, the control is switched to the second readout unit to integrate the photocurrent signal and output the second voltage signal; otherwise, the first readout unit is kept integrating the photocurrent signal.

8. The control method of the readout circuit with switchable pixel structure according to claim 7, characterized in that: The switching condition of the second readout unit includes: the first voltage signal output by the first readout unit is saturated in advance; The method for determining whether a switching condition of the second readout unit is satisfied includes: Draw a characteristic curve of the first voltage signal output by the first readout unit; Observe whether the characteristic curve is saturated early; If the characteristic curve is saturated in advance, it is determined that the switching condition of the second readout unit is met; otherwise, it is determined that the switching condition of the second readout unit is not met.

9. The control method of the readout circuit with switchable pixel structure according to claim 7, characterized in that: The method of causing the first readout unit to integrate the photocurrent signal and output a first voltage signal includes: Disconnect the first switch Φ CTIA , and close the first reset tube Φ RS1 , to convert the integrating capacitor C INT_CTIA The charge in the body is discharged cleanly; The first reset transistor Φ RS1 Open and close the first switch Φ CTIA , so as to connect the first readout unit and the photosensitive unit, through the integration capacitor C INT_CTIA Integrate the photocurrent signal generated by the photosensitive unit; Disconnect the first switch Φ CTIA , and close the third switch tube Φ SEL , to output a first voltage signal to the column transmission bus.

10. The control method of the readout circuit with switchable pixel structure according to claim 7, characterized in that: The method of controlling the switching to the second readout unit to integrate the photocurrent signal and output the second voltage signal includes: Disconnect the second switch Φ SFD , and close the second reset tube Φ RS2 , reset the voltage at the input terminal of the source follower SF to the ground potential GND to clear the previous integration result; Disconnect the second reset tube Φ RS2 , and close the second switch tube Φ SFD , so as to conduct the second readout unit with the photosensitive unit, wherein the second readout unit integrates the photocurrent signal generated by the photosensitive unit; Disconnect the second switch Φ SFD , and close the third switch tube Φ SEL , to output a second voltage signal to the column transmission bus.

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