Pixel signal sampling circuit, sampling method, image sensor and electronic equipment

Abstract

The invention relates to the technical field of image processing, and discloses a pixel signal sampling circuit, a sampling method, an image sensor and electronic equipment, the pixel signal sampling circuit comprises a first sampling branch, a second sampling branch and a reset branch, the first sampling branch is used for collecting each pixel reset signal to a control module, and the second sampling branch is used for collecting each pixel reset signal; the second sampling branch is used for collecting exposure signals of all pixels to the control module, the two ends of the reset branch are electrically connected with the output end of the first sampling branch and the output end of the second sampling branch respectively, and the reset branch is used for being connected after the first sampling branch and the second sampling branch output respective signals each time. And the output ends of the first sampling branch and the second sampling branch are reset. The reset branch circuit is conducted after the pixel exposure signal and the pixel reset signal of the pixel are collected each time, reset is carried out, the difference between the initial states of different pixel units is eliminated, therefore, fixed mode noise is reduced, and the quality and consistency of images are greatly improved.

Description

Technical Field

[0001] The present application relates to the field of image processing technology, and in particular to a pixel signal sampling circuit, a sampling method, an image sensor, and an electronic device. Background Art

[0002] Image processing technology has become extremely common in today's society and is widely used in various fields, from consumer electronics and medical imaging to autonomous driving and security monitoring. Among them, image sensors, as the core components of image processing systems, play a vital role. Image sensors are responsible for converting optical signals into electrical signals. This process not only directly affects the quality of the image, but also determines the efficiency and effect of subsequent image processing.

[0003] In existing image sensor technology, Correlated Double Sampling (CDS) circuits are widely used to collect pixel signals. However, although CDS technology can effectively reduce noise, the difference in the initial state of different pixel units still leads to fixed pattern noise (FPN). This inconsistency in the initial state seriously affects the quality and consistency of the image. Summary of the invention

[0004] In view of this, the embodiments of the present application provide a pixel signal sampling circuit, a sampling method, an image sensor, and an electronic device, which can effectively solve the problem that the differences in the initial states of different pixel units in the pixel signal acquisition circuit in the prior art still lead to fixed pattern noise, seriously affecting the quality and consistency of the image.

[0005] In a first aspect, an embodiment of the present application provides a pixel signal sampling circuit, comprising: a first sampling branch, a second sampling branch and a reset branch, wherein the first sampling branch is used to collect reset signals of each pixel to a control module, and the second sampling branch is used to collect exposure signals of each pixel to the control module;

[0006] Two ends of the reset branch are electrically connected to the output end of the first sampling branch and the output end of the second sampling branch respectively;

[0007] The control module is connected to the control end of the reset branch, and is used to control the reset branch to be turned on each time the first sampling branch and the second sampling branch output their respective signals, so as to reset the output ends of the first sampling branch and the second sampling branch.

[0008] In some embodiments, the first sampling branch and the second sampling branch have the same structure, and both sampling branches include: a CMOS transmission gate;

[0009] The input ends of the two CMOS transmission gates are respectively used to input the pixel reset signal and the pixel exposure signal, the output ends of the two CMOS transmission gates are respectively connected to the two ends of the reset branch, and the control ends of each CMOS transmission gate are respectively used to input control signals.

[0010] In some embodiments, the pixel signal sampling circuit also includes: a low-pass filter and a voltage regulator, the input end of the low-pass filter is used to connect to a power supply, the output end of the low-pass filter is connected to the input end of the voltage regulator, and the voltage regulator is used to stabilize the signal at the output end of the low-pass filter to provide the power required by the photodiode of each pixel unit.

[0011] In some embodiments, the first sampling branch and the second sampling branch have the same structure, and both sampling branches include: a transmission tube and a column selection tube;

[0012] The gates of the transmission tubes are respectively connected to the two ends of the reset branch, the drains of the transmission tubes are grounded, and the sources of the transmission tubes are respectively connected to the second signal ends of the column selection tubes;

[0013] The first signal end of each column selection tube is used to input the first power supply, the controlled end of each column selection tube is used to input each control signal, and the first signal end of each column selection tube is used to output each pixel reset signal and each pixel exposure signal.

[0014] In some embodiments, the first sampling branch and the second sampling branch both further include: a charge injection module;

[0015] The first signal end of each charge injection module is used to input the second power supply and the third power supply respectively, the second signal end of each charge injection module is connected to the gate of each transmission tube respectively, and the controlled end of each charge injection module is used to input each control signal.

[0016] In some embodiments, the pixel signal sampling circuit further includes: a differential amplifier;

[0017] The first input end of the differential amplifier is electrically connected to the output end of the first sampling branch, the second input end of the differential amplifier is electrically connected to the output end of the second sampling branch, and the output end of the differential amplifier is used to connect to the control module.

[0018] In some embodiments, the pixel signal sampling circuit further includes: a source follower and a current source module;

[0019] The gate of the source follower is used to input each of the pixel reset signals and each of the pixel exposure signals, the source of the source follower is connected to the input ends of the first sampling branch and the second sampling branch, the drain of the source follower is connected to one end of the current source module, and the other end of the current source module is grounded.

[0020] In a second aspect, an embodiment of the present application provides a pixel signal sampling method, which is applied to at least one pixel signal sampling circuit described in the first aspect, and the pixel signal sampling method includes:

[0021] respectively controlling the first sampling branch and the second sampling branch to collect the pixel reset signal and the pixel exposure signal of the current pixel unit;

[0022] When the current pixel unit acquisition is completed, controlling the reset branch to be turned on to reset the first sampling branch and the second sampling branch;

[0023] After the reset is completed, the first sampling branch and the second sampling branch are respectively controlled to continue to collect the pixel reset signal and the pixel exposure signal of the next pixel unit, and so on, until the collection of all pixel units is completed.

[0024] In a third aspect, an embodiment of the present application provides an image sensor, wherein the image sensor includes at least one pixel signal sampling circuit as described in the first aspect.

[0025] In a fourth aspect, an embodiment of the present application provides an electronic device, wherein the electronic device includes the image sensor described in the third aspect.

[0026] The embodiments of the present application have the following beneficial effects:

[0027] The pixel signal sampling circuit of the present application includes a first sampling branch, a second sampling branch and a reset branch. The first sampling branch is used to collect reset signals of each pixel to the control module, and the second sampling branch is used to collect exposure signals of each pixel to the control module. The two ends of the reset branch are electrically connected to the output end of the first sampling branch and the output end of the second sampling branch respectively. The reset branch is used to be turned on after the first sampling branch and the second sampling branch output their respective signals each time, so as to reset the output ends of the first sampling branch and the second sampling branch. The present application sets a reset branch in the pixel signal sampling circuit. The reset branch is turned on after collecting the pixel exposure signal and the pixel reset signal of the pixel each time, and resets the output ends of the first sampling branch and the second sampling branch, so as to ensure that the process of collecting each pixel is exactly the same, eliminate the differences between the initial states of different pixel units, thereby reducing fixed pattern noise and greatly improving the quality and consistency of the image. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A first structural schematic diagram of a pixel signal sampling circuit according to an embodiment of the present application is shown;

[0030] Figure 2 A second structural schematic diagram of the pixel signal sampling circuit according to an embodiment of the present application is shown;

[0031] Figure 3 A first circuit schematic diagram of a pixel signal sampling circuit according to an embodiment of the present application is shown;

[0032] Figure 4 A second circuit schematic diagram of the pixel signal sampling circuit according to an embodiment of the present application is shown;

[0033] Figure 5 A schematic flow chart of a pixel signal sampling method according to an embodiment of the present application is shown.

[0034] Description of main component symbols:

[0035] 10: first sampling branch; 20: second sampling branch; 30: reset branch; 40: control module; 50: low-pass filter; 60: voltage regulator; 70: pixel unit; 80: source follower; 90: current source module; 101: first CMOS transmission gate; 201: second CMOS transmission gate; 102: first charge injection module; 202: second charge injection module. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0037] The components of the embodiments of the present application generally described and shown in the drawings herein may be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0038] Hereinafter, the terms "including", "having" and their cognates that can be used in various embodiments of the present application are intended only to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or increasing the possibility of one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items. In addition, the terms "first", "second", "third" and the like are only used to distinguish descriptions and cannot be understood as indicating or implying relative importance.

[0039] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present application belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present application.

[0040] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0041] Taking into account that the differences in the initial states of different pixel units in the pixel signal acquisition circuit in the existing scheme will still lead to fixed pattern noise problems, seriously affecting the quality and consistency of the image, etc., for this purpose, the present application provides a pixel signal sampling circuit, a sampling method, an image sensor, and an electronic device. The present application sets a reset branch in the pixel signal sampling circuit. The reset branch is turned on after each pixel exposure signal and pixel reset signal of the pixel are acquired, and the output ends of the first sampling branch and the second sampling branch are reset to ensure that the acquisition process of each pixel is exactly the same, eliminate the differences between the initial states of different pixel units, thereby reducing fixed pattern noise and greatly improving the quality and consistency of the image.

[0042] It can be understood that in order to reduce the readout noise and improve the quality of the signal, the image sensor uses a correlated double sampling circuit to collect pixel signals. Specifically, the pixel exposure signal and the pixel reset signal of the pixel unit are collected separately, wherein the pixel exposure signal is a signal read after the pixel unit is exposed, and the pixel reset signal is a signal read after the pixel unit is reset. The collection order can be set according to the actual application situation. The pixel exposure signal can be collected first, and then the pixel unit is reset and the pixel reset signal is collected; or the pixel unit can be reset first, and the pixel reset signal can be collected, and then the pixel unit is exposed, and the pixel exposure signal can be collected. The difference between the pixel exposure signal and the pixel reset signal is calculated, so as to eliminate the readout noise and improve the signal-to-noise ratio of the signal.

[0043] The pixel signal sampling circuit is described below in conjunction with some specific embodiments.

[0044] Figure 1 A schematic diagram of the structure of the pixel signal sampling circuit of the embodiment of the present application is shown. Exemplarily, the pixel signal sampling circuit includes a first sampling branch 10, a second sampling branch 20 and a reset branch 30. The first sampling branch 10 is used to collect each pixel reset signal to the control module 40, and the second sampling branch 20 is used to collect each pixel exposure signal to the control module 40. Specifically, the control module 40 controls the sampling of the pixel signal by controlling each branch, and processes the pixel exposure signal and the pixel reset signal to obtain the pixel value.

[0045] It is understandable that the control module 40 of the present embodiment can be any type of control module. The control module 40 of the present embodiment can be an MCU, the control module 40 of the present embodiment can also be a CPU, the control module 40 of the present embodiment can also be a DSP, and the control module 40 of the present embodiment can also be an FPGA. Exemplarily, the control module 40 of the present embodiment is a DSP.

[0046] The two ends of the reset branch 30 are electrically connected to the output end of the first sampling branch 10 and the output end of the second sampling branch 20 respectively. The control module 40 is connected to the control end of the reset branch 30. The control module 40 is used to control the reset branch 30 to be turned on each time the first sampling branch 10 and the second sampling branch 20 output their respective signals, so as to reset the output ends of the first sampling branch 10 and the second sampling branch 20.

[0047] It can be understood that pixel points are arranged in the pixel unit, and the pixel point is the basic unit of the image sensor. Each pixel point is responsible for capturing the light intensity information of an area. The pixel point includes a photodiode, and the photodiode converts the incident light into a current or voltage signal. Furthermore, a readout circuit can be arranged in the pixel point to perform preliminary processing on the current or voltage signal.

[0048] Exemplarily, after acquiring the pixel exposure signal and the pixel reset signal of the current pixel unit, the control module 40 controls the reset branch 30 to be turned on, and the output end of the first sampling branch 10 and the output end of the second sampling branch 20 are reset. After the reset, the control module 40 continues to control the first sampling branch 10 and the second sampling branch 20 to collect the pixel exposure signal and the pixel reset signal of the next pixel unit. It can be understood that the reset branch 30 of this embodiment can be any kind of switch module, the reset branch 30 can be a switch tube, the reset branch 30 can also be a relay, the reset branch 30 can also be an optocoupler, etc.

[0049] In the pixel signal sampling circuit of the present embodiment, a reset branch 30 is provided between the output ends of the first sampling branch 10 and the second sampling branch 20. The control module 40 resets the output end of the first sampling signal and the output end of the second signal after each signal output by the first sampling branch 10 and the second sampling branch 20, thereby ensuring that each exposure or reset process is exactly the same, eliminating the difference in the initial exposure state or the initial reset state of different pixel units, offsetting the fixed pattern noise between the pixel units, and improving the consistency of the signal.

[0050] As an optional solution, Figure 2 Shown is another structural schematic diagram of a pixel signal sampling circuit.

[0051] In one embodiment, if Figure 2 As shown, based on the above embodiment, the pixel signal sampling circuit further includes: a low-pass filter 50 and a voltage regulator 60. The input end of the low-pass filter is used to connect to a power supply. Exemplarily, the output end of the low-pass filter 50 is connected to the input end of the voltage regulator 60. The voltage regulator 60 is used to stabilize the signal at the output end of the low-pass filter 50 to provide the power required by the photodiode of each pixel unit 70. The power supply in this embodiment is represented by VCC1.

[0052] As another embodiment, the voltage regulator 60 may also be any voltage regulator circuit, and the voltage regulator element of the voltage regulator circuit is used to stabilize the signal of the low-pass filter 50 to ensure the reliability of the photodiode of the pixel unit 70 .

[0053] The cutoff frequency of the low-pass filter 50 may be set according to actual application conditions. Exemplarily, the cutoff frequency of the low-pass filter 50 is determined according to the frequency characteristics of the power supply noise, thereby effectively suppressing the power supply noise.

[0054] In the pixel signal sampling circuit of the present embodiment, a low-pass filter 50 is arranged between the power supply and the photodiode to filter the power supply. The low-pass filter 50 can filter out the high-frequency noise of the power supply, further improving the quality of the pixel signal, and a voltage stabilizer 60 is arranged to stabilize the signal of the low-pass filter 50, ensuring that the photodiode can maintain consistent performance under different conditions. By filtering out high-frequency noise and stabilizing the power supply voltage, the signal-to-noise ratio of the photodiode output signal can be significantly improved, which greatly improves the detection capability and image quality of the system and reduces the performance changes caused by power supply fluctuations.

[0055] In one embodiment, if Figure 2As shown, based on the above embodiment, the pixel signal sampling circuit also includes: a source follower 80 and a current source module 90, the gate of the source follower 80 is used to input each pixel reset signal and each pixel exposure signal, the source of the source follower 80 is connected to the input end of the first sampling branch 10 and the second sampling branch 20, the drain of the source follower 80 is connected to one end of the current source module 90, and the other end of the current source module 90 is grounded.

[0056] It is understandable that the source follower 80 is an N-channel MOS tube, and the signal of the pixel unit 70 is input from the gate and output from the source. The MOS tube acts as a voltage follower to maintain the integrity of the signal. Furthermore, the N-well substrate of the MOS tube is connected to the source end to reduce the influence of the substrate bias, thereby improving the linearity of the signal output.

[0057] Specifically, the current source module 90 can be set according to actual application conditions. A resistor can be set in the current source module 90 to form a resistive load, or a transistor can be set in the current source module 90 to provide a current signal. Furthermore, an operational amplifier can be set in the current source module 90 to improve the accuracy of the current by using the negative feedback mechanism of the operational amplifier.

[0058] The pixel signal sampling circuit of this embodiment is provided with a source follower 80 and a current source module 90. The source follower 80 is used to buffer the pixel signal to ensure that the signal is not distorted during transmission. At the same time, impedance matching can be performed to improve signal transmission efficiency. The current source module 90 is used to provide bias current and reference current, thereby ensuring the high performance and stability of the image sensor.

[0059] As an optional solution, Figure 3 Shown is a circuit schematic diagram of a pixel signal sampling circuit.

[0060] In one embodiment, if Figure 3As shown, on the basis of the above embodiment, in order to prevent the charge on the gate capacitor and the external capacitor from being redistributed when the switch tube switches state, resulting in charge injection and extraction, and then causing imbalance, the first sampling branch 10 and the second sampling branch 20 of this embodiment have the same structure. Exemplarily, both sampling branches include: CMOS transmission gates, that is, the first sampling branch 10 includes a first CMOS transmission gate 101, and the second sampling branch 20 includes a second CMOS transmission gate 201. Specifically, the input end of the first CMOS transmission gate 101 is used to input a pixel reset signal, the output end of the first CMOS transmission gate 101 is connected to one end of the reset branch 30, and the control end of the first CMOS transmission gate 101 is used to input a control signal; the input end of the second CMOS transmission gate 201 is used to input a pixel exposure signal, the output end of the second CMOS transmission gate 201 is connected to the other end of the reset branch 30, and the control end of the second CMOS transmission gate 201 is used to input a control signal.

[0061] Specifically, each CMOS transmission gate includes a PMOS tube and an NMOS tube, and the PMOS tube and the NMOS tube are connected in parallel. When the control signals of the PMOS tube and the NMOS tube change from low to high, the NMOS tube is turned on and the PMOS tube is turned off. At this time, the gate capacitance of the NMOS tube is charged and the gate capacitance of the PMOS tube is discharged; when the control signals of the PMOS tube and the NMOS tube change from high to low, the NMOS tube is turned off and the PMOS tube is turned on. At this time, the gate capacitance of the NMOS tube is discharged and the gate capacitance of the PMOS tube is charged. Since the operations of the NMOS and PMOS tubes are complementary, these charge changes can offset each other, thereby reducing the voltage change on the holding capacitor, reducing the offset voltage, and further improving the image quality.

[0062] In one embodiment, if Figure 3 As shown, based on the above embodiment, the first sampling branch 10 and the second sampling branch 20 have the same structure. Exemplarily, both sampling branches include: a transmission tube and a column selection tube; that is, the first sampling branch 10 includes a first transmission tube Q1 and a first column selection tube Q2, and the second sampling branch 20 includes a second transmission tube Q3 and a second column selection tube Q4.

[0063] Specifically, the gate of the first transmission tube Q1 is connected to one end of the reset branch 30, the drain of the first transmission tube Q1 is grounded, and the source of the first transmission tube Q1 is connected to the second signal end of the first column selection tube Q2. The first signal end of the first column selection tube Q2 is used to input the first power supply, the controlled end of the first column selection tube Q2 is used to input the control signal, and the first signal end of the first column selection tube Q2 is used to output the pixel reset signal. The gate of the second transmission tube Q3 is connected to the other end of the reset branch 30, the drain of the second transmission tube Q3 is grounded, and the source of the second transmission tube Q3 is connected to the second signal end of the second column selection tube Q4. The first signal end of the second column selection tube Q4 is used to input the first power supply, the controlled end of the second column selection tube Q4 is used to input the control signal, and the first signal end of the second column selection tube Q4 is used to output the pixel exposure signal.

[0064] Among them, the transmission tube is a source follower, and the first power supply is a current source I1, which provides a stable bias current for the transmission tube. The source follower is used to buffer the pixel signal to ensure that the signal is not distorted during transmission. At the same time, impedance matching can be performed to improve signal transmission efficiency.

[0065] In order to amplify the difference between the pixel exposure signal and the pixel reset signal, the pixel signal sampling circuit further includes: a differential amplifier U1, a first input terminal of the differential amplifier U1 is electrically connected to the output terminal of the first sampling branch 10, a second input terminal of the differential amplifier U1 is electrically connected to the output terminal of the second sampling branch 20, and an output terminal of the differential amplifier U1 is used to connect to the control module 40. Specifically, the differential amplifier U1 is a differential amplifier, and further, a first output control tube Q5 and a second output control tube Q6 are respectively provided after the first signal terminal of each column selection tube, and the first output control tube Q5 and the second output control tube Q6 are respectively connected to the two input terminals of the differential amplifier U1.

[0066] Exemplarily, the working process of the pixel signal sampling circuit of the present embodiment is: controlling the first column selection tube Q2 and the second column selection tube Q4 to be turned on, providing a stable current for the first transmission tube Q1 and the second transmission tube Q3, exposing the current pixel unit 70, controlling the second CMOS transmission gate 201 to be turned on, collecting the pixel exposure signal of the pixel unit 70, resetting the pixel unit 70 after the collection is completed, controlling the first CMOS transmission gate 101 to be turned on after the reset, collecting the pixel reset signal of the pixel unit 70, controlling the first output control tube Q5 and the second output control tube Q6 to be turned on, transmitting the collected signal to the differential amplifier U1, so that it differentially amplifies the pixel exposure signal and the pixel reset signal, and then transmitting it to the control module 40. After the control module 40 controls the first output control tube Q5 and the second output control tube Q6 to be turned on, it controls the reset branch 30 to be turned on, resets the gate signals of the first transmission tube Q1 and the second transmission tube Q3, eliminates the difference between the initial states of different pixel units 70, and then continues to collect the signal of the next pixel unit 70.

[0067] The pixel signal sampling circuit of this embodiment is provided with a source follower 80 to transmit the collected signal. The source follower 80 can protect the output signal of the pixel unit 70 from being affected by the load of the subsequent circuit, thereby ensuring the integrity and consistency of the signal. At the same time, a differential amplifier U1 is provided to differentially amplify the pixel exposure signal and the pixel reset signal, thereby effectively amplifying the weak photocurrent signal, suppressing noise and background signals, and improving image quality.

[0068] In one embodiment, Figure 4 The figure shows another circuit diagram of the pixel signal sampling circuit. On the basis of the above embodiment, the first sampling branch 10 and the second sampling branch 20 both further include a charge injection module, that is, the first sampling branch 10 includes a first charge injection module 102, and the second sampling branch 20 includes a second charge injection module 202. The first signal end of the first charge injection module 102 is used to input the second power supply VCC2, the second signal end of the first charge injection module 102 is connected to the gate of the first transmission tube Q1, and the controlled end of the first charge injection module 102 is used to input the control signal; the first signal end of the second charge injection module 202 is used to input the third power supply VCC3, the second signal end of the second charge injection module 202 is connected to the gate of the second transmission tube Q3, and the controlled end of the second charge injection module 202 is used to input the control signal. Exemplarily, as Figure 3 As shown, the charge injection module is configured as a CMOS transmission gate, and the magnitudes of the second power source VCC2 and the third power source VCC3 can be set according to actual application conditions.

[0069] Specifically, according to the pixel average value of the pixel unit 70 under the dark condition, the first charge injection module 102 and the second charge injection module 202 are controlled. If the pixel average value is greater than zero, the second charge injection module 202 is controlled to inject charge into the gate of the second transmission tube Q3; if the pixel average value is less than zero, the gate charge of the first transmission tube Q1 is obtained by controlling the first charge injection module 102.

[0070] Exemplarily, the working process of the pixel signal sampling circuit of this embodiment is: controlling the second CMOS transmission gate 201 to be turned on, collecting the pixel exposure signal of the pixel unit 70, resetting the pixel unit 70 after the collection is completed, and after resetting, injecting charges into the gate of the transmission tube by controlling the second charge injection module 202 and the second charge injection module 202, or controlling the charge output of the gate of the transmission tube to compensate for the dark current, and then controlling the first CMOS transmission gate 101 to be turned on, and collecting the pixel reset signal of the pixel unit 70.

[0071] The pixel signal sampling circuit of this embodiment is provided with a charge injection module to inject charge into the gate of the transmission tube, which can correct the offset of the output signal of the pixel unit 70 caused by the dark current, making the output signal more accurate. At the same time, by compensating for the dark current, the influence of noise can be reduced, the signal-to-noise ratio of the signal can be improved, and the image quality can be improved.

[0072] The present application also provides a pixel signal sampling method. Figure 5 The figure is a flow chart of a pixel signal sampling method according to an embodiment of the present application. The pixel signal sampling method is applied to the pixel signal sampling circuit mentioned in the above embodiment, and includes:

[0073] Step S101 : respectively controlling the first sampling branch 10 and the second sampling branch 20 to collect the pixel reset signal and the pixel exposure signal of the current pixel unit 70 .

[0074] Specifically, the acquisition sequence can be set according to the actual application situation. The pixel exposure signal can be acquired first, and then the pixel unit 70 is reset and the pixel reset signal is acquired. Alternatively, the pixel unit 70 can be reset first, the pixel reset signal can be acquired, and then the pixel unit 70 can be exposed and the pixel exposure signal can be acquired.

[0075] Step S102 : when the current pixel unit 70 has finished collecting data, the reset branch 30 is controlled to be turned on to reset the first sampling branch 10 and the second sampling branch 20 .

[0076] Specifically, after obtaining the pixel exposure signal and pixel reset signal of the current pixel unit 70, the control module 40 controls the reset branch 30 to be turned on, and the output end of the first sampling branch 10 and the output end of the second sampling branch 20 are reset to ensure that each exposure or reset process is exactly the same.

[0077] Step S103: after the resetting is completed, the first sampling branch 10 and the second sampling branch 20 are respectively controlled to continue to collect the pixel reset signal and the pixel exposure signal of the next pixel unit 70, and so on, until the collection of all pixel units is completed.

[0078] Specifically, after collecting the pixel reset signal and pixel exposure signal of the next pixel unit 70, the reset branch 30 is controlled to be turned on, the output end of the first sampling branch 10 and the output end of the second sampling branch 20 are reset again, and the pixel reset signal and pixel exposure signal of other pixel units 70 are continuously collected until the collection of all pixel units is completed.

[0079] In this embodiment, after the control module 40 obtains the pixel exposure signal and the pixel reset signal of the current pixel unit 70, it controls the reset branch 30 to be turned on, resets the output end of the first sampling branch 10 and the output end of the second sampling branch 20, eliminates the fixed offset error of the initial exposure state or the initial reset state of different pixel units 70, and significantly improves the image quality and measurement accuracy.

[0080] The present application also provides an image sensor. Exemplarily, the image sensor includes the above-mentioned pixel signal sampling circuit.

[0081] The present application also provides an electronic device. Exemplarily, the electronic device includes the above-mentioned image sensor. Exemplarily, the electronic device can be a digital camera, a smart phone, a surveillance camera, etc.

[0082] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and structure diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in an alternative implementation, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the structure diagram and / or the flow diagram, and the combination of boxes in the structure diagram and / or the flow diagram, can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0083] In addition, the functional modules or units in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0084] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a smart phone, a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the various embodiments of the present application.

[0085] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A pixel signal sampling circuit, characterized in that: include: A first sampling branch, a second sampling branch and a reset branch, wherein the first sampling branch is used to collect reset signals of each pixel and send them to a control module, and the second sampling branch is used to collect exposure signals of each pixel and send them to the control module; Two ends of the reset branch are electrically connected to the output end of the first sampling branch and the output end of the second sampling branch respectively; The control module is connected to the control end of the reset branch, and is used to control the reset branch to be turned on each time the first sampling branch and the second sampling branch output their respective signals, so as to reset the output ends of the first sampling branch and the second sampling branch.

2. The pixel signal sampling circuit according to claim 1, characterized in that: The first sampling branch and the second sampling branch have the same structure, and both sampling branches include: a CMOS transmission gate; The input ends of the two CMOS transmission gates are respectively used to input the pixel reset signal and the pixel exposure signal, the output ends of the two CMOS transmission gates are respectively connected to the two ends of the reset branch, and the control ends of each CMOS transmission gate are respectively used to input control signals.

3. The pixel signal sampling circuit according to claim 1, characterized in that: The pixel signal sampling circuit further includes: a low-pass filter and a voltage stabilizer, wherein the input end of the low-pass filter is used to connect to a power supply, and the output end of the low-pass filter is connected to the input end of the voltage stabilizer; The voltage regulator is used to stabilize the signal at the output end of the low-pass filter to provide the power required by the photodiode of each pixel unit.

4. The pixel signal sampling circuit according to claim 1, characterized in that: The first sampling branch and the second sampling branch have the same structure, and both sampling branches include: a transmission tube and a column selection tube; The gates of the transmission tubes are respectively connected to the two ends of the reset branch, the drains of the transmission tubes are grounded, and the sources of the transmission tubes are respectively connected to the second signal ends of the column selection tubes; The first signal end of each column selection tube is used to input the first power supply, the controlled end of each column selection tube is used to input each control signal, and the first signal end of each column selection tube is used to output each pixel reset signal and each pixel exposure signal.

5. The pixel signal sampling circuit according to claim 4, characterized in that: The first sampling branch and the second sampling branch both further include: a charge injection module; The first signal end of each charge injection module is used to input the second power supply and the third power supply respectively, the second signal end of each charge injection module is connected to the gate of each transmission tube respectively, and the controlled end of each charge injection module is used to input each control signal.

6. The pixel signal sampling circuit according to claim 1, characterized in that: The pixel signal sampling circuit further includes: a differential amplifier; The first input end of the differential amplifier is electrically connected to the output end of the first sampling branch, the second input end of the differential amplifier is electrically connected to the output end of the second sampling branch, and the output end of the differential amplifier is used to connect to the control module.

7. The pixel signal sampling circuit according to claim 1, characterized in that: The pixel signal sampling circuit further includes: a source follower and a current source module; The gate of the source follower is used to input each of the pixel reset signals and each of the pixel exposure signals, the source of the source follower is connected to the input ends of the first sampling branch and the second sampling branch, the drain of the source follower is connected to one end of the current source module, and the other end of the current source module is grounded.

8. A pixel signal sampling method, characterized in that: The pixel signal sampling circuit according to any one of claims 1 to 7, wherein the pixel signal sampling method comprises: respectively controlling the first sampling branch and the second sampling branch to collect the pixel reset signal and the pixel exposure signal of the current pixel unit; When the current pixel unit acquisition is completed, controlling the reset branch to be turned on to reset the first sampling branch and the second sampling branch; After the reset is completed, the first sampling branch and the second sampling branch are respectively controlled to continue to collect the pixel reset signal and the pixel exposure signal of the next pixel unit, and so on, until the collection of all pixel units is completed.

9. An image sensor, characterized in that: The image sensor comprises: a pixel signal sampling circuit as described in any one of claims 1-7.

10. An electronic device, characterized in that: The electronic device comprises: the image sensor as claimed in claim 9.

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