WO2021218315A1

WO2021218315A1 - Image sensing circuit, image sensor, and terminal device

Info

Publication number: WO2021218315A1
Application number: PCT/CN2021/077597
Authority: WO
Inventors: 杨鑫
Original assignee: Oppo广东移动通信有限公司
Priority date: 2020-04-26
Filing date: 2021-02-24
Publication date: 2021-11-04
Also published as: CN111510651B; CN111510651A

Abstract

The present application relates to the technical field of image sensors, and provides an image sensing circuit, an image sensor, and a terminal device. According to embodiments of the present application, when an image sensing circuit is in an image sensing mode, a reset signal and an analog image signal sequentially output by a pixel structure after one exposure is completed are performed differential by a correlated double sampling circuit to obtain a first differential signal, and then the first differential signal is converted by an analog-to-digital conversion circuit into a digital image signal for outputting, thus obtaining complete image information of a scenario; when the image sensing circuit is in a dynamic vision sensing mode, two analog image signals output by the pixel structure after two successive exposures are completed are performed differential by the correlated double sampling circuit to obtain a second differential signal, and then a corresponding digital image signal is output by a comparison circuit according to a voltage of the second differential signal, thus only outputting address and information of a pixel of which the light intensity changes, and identifying the change in the scenario.

Description

Image sensor circuit, image sensor and terminal equipment

Cross-references to related applications

This application is filed based on the Chinese patent application with the application number 202010339135.6 and the filing date on April 26, 2020, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced in this application in full .

Technical field

This application belongs to the technical field of image sensors, and in particular relates to an image sensor circuit, an image sensor, and a terminal device.

Background technique

At present, traditional image sensors mainly include complementary metal oxide semiconductor (Complementary Metal Oxide Semiconductor, CMOS) image sensors (CMOS Image Sensor, CIS) and charge-coupled device (Charge-coupled Device, CCD) image sensors. The visual image acquisition method of the traditional CMOS image sensor is to acquire image frames at a fixed frequency, which has defects such as high redundancy, high delay, high noise, low dynamic range and high data volume. Dynamic Vision Sensor (DVS) is a new type of CMOS image sensor. Its working principle imitates the working mechanism of biological vision. It only outputs the address and information of the pixels whose light intensity changes, instead of passively reading out the image sequentially. The information of each pixel in the frame can eliminate redundant data from the source. It has the characteristics of real-time dynamic response to scene changes, ultra-sparse image representation, and asynchronous output of events. It is widely used in target tracking, real-time monitoring, industrial automation and robotics. And other fields.

However, the existing dynamic vision sensor can only output the address and information of the pixel whose light intensity changes, and can only identify the scene change, and cannot obtain the complete image information of the scene.

Summary of the invention

The purpose of this application is to provide an image sensor circuit, image sensor and terminal equipment, which aims to solve the problem that the existing dynamic vision sensor can only output the address and information of the pixel where the light intensity changes, and can only recognize the scene change, but cannot obtain the scene. The problem of complete image information.

The first aspect of the embodiments of the present application provides an image sensing circuit, which includes a pixel structure, a correlated double sampling circuit, a path selection circuit, an analog-to-digital conversion circuit, and a comparison circuit;

The pixel structure, the correlated double sampling circuit, and the path selection circuit are electrically connected in sequence, and the path selection circuit is also electrically connected with the analog-to-digital conversion circuit and the comparison circuit;

When the image sensing circuit is in the image sensing mode, the path selection circuit is used for turning on the electrical connection between the correlated double sampling circuit and the analog-to-digital conversion circuit, and the pixel structure is used for After one exposure is completed, a reset signal and an analog image signal are sequentially output. The correlated double sampling circuit is used to differentiate the reset signal and the analog image signal to obtain a first differential signal. The analog-to-digital conversion circuit is used to The first differential signal is converted into a digital image signal and then output;

When the image sensing circuit is in the dynamic vision sensing mode, the path selection circuit is used to turn on the electrical connection between the correlated double sampling circuit and the comparison circuit, and the pixel structure is used to The first analog image signal is output after the exposure is completed, and the second analog image signal is output after the next exposure is completed. The correlated double sampling circuit is used to differentiate the first analog image signal and the second analog image signal to obtain The second differential signal, the comparison circuit is used for outputting the corresponding digital image signal according to the voltage level of the second differential signal.

In an embodiment, the correlated double sampling circuit includes a capacitor, a first comparator and a first switch;

The positive electrode of the capacitor is electrically connected to the pixel structure, the negative electrode of the capacitor is electrically connected to the negative input terminal of the first comparator and one end of the first switch, and the first comparator The positive input terminal of is used to access a ramp signal, and the output terminal of the first comparator is electrically connected to the other terminal of the first switch and the path selection circuit;

When the image sensing circuit is in the image sensing mode, the first switch is used to turn on when the pixel structure outputs the reset signal, and turn off when the pixel structure outputs the analog image signal, The capacitor is used to store the reset signal, and the first comparator is used to make a difference between the reset signal and the analog image signal to obtain a first differential signal and output it to the analog-to-digital conversion circuit;

When the image sensing circuit is in the dynamic vision sensing mode, the first switch is turned off, the capacitor is used to store the first analog image signal, and the first comparator is used to compare the first analog image signal After performing difference with the second analog image signal, a second difference signal is obtained and output to the comparison circuit.

In one embodiment, the path selection circuit includes a second switch;

The input terminal of the second switch is electrically connected to the correlated double sampling circuit, the first output terminal of the second switch is electrically connected to the analog-to-digital conversion circuit, and the second output terminal of the second switch Electrically connected with the comparison circuit;

When the image sensing circuit is in the image sensing mode, the input terminal and the first output terminal of the second switch are turned on to turn on the electrical connection between the correlated double sampling circuit and the analog-to-digital conversion circuit. Sexual connection

When the image sensing circuit is in the dynamic vision sensing mode, the input terminal and the second output terminal of the second switch are turned on to turn on the electrical characteristics between the correlated double sampling circuit and the comparison circuit. connect.

In one embodiment, the comparison circuit includes a second comparator;

The negative input terminal of the second comparator is electrically connected to the path selection circuit, and the positive input terminal of the second comparator is used to access a threshold voltage signal;

When the image sensing circuit is in the dynamic vision sensing mode, the second comparator is used to compare the voltage of the second differential signal with the voltage of the threshold voltage signal. A first digital image signal is output when the voltage of the threshold voltage signal is greater than that of the threshold voltage signal, and a second digital image signal is output when the voltage of the second differential signal is less than the voltage of the threshold voltage signal.

In one embodiment, the comparison circuit includes a second comparator and a third comparator;

The negative input terminal of the second comparator and the negative input terminal of the third comparator are electrically connected to the path selection circuit, and the positive input terminal of the second comparator and the positive input terminal of the third comparator are electrically connected. The input terminal is used to connect the threshold voltage signal;

When the image sensing circuit is in the dynamic vision sensing mode, the second comparator and the third comparator are used to compare the voltage of the second differential signal with the voltage of the threshold voltage signal, and the The second comparator outputs the first digital image signal when the voltage of the second differential signal is greater than the voltage of the threshold voltage signal, and the third comparator outputs the first digital image signal when the voltage of the second differential signal is less than the threshold voltage signal. The second digital image signal is output when the voltage is higher.

The negative input terminal of the second comparator and the positive input terminal of the third comparator are electrically connected to the path selection circuit, and the positive input terminal of the second comparator is used to connect a positive threshold voltage signal, The negative input terminal of the third comparator is used to connect a negative threshold voltage signal;

When the image sensing circuit is in the dynamic vision sensing mode, the second comparator is used to compare the voltage of the second differential signal with the voltage of the positive threshold voltage signal. Output a first digital image signal when the voltage is greater than the voltage of the positive threshold voltage signal, and output a second digital image signal when the voltage of the second differential signal is less than or equal to the voltage of the positive threshold voltage signal;

When the image sensing circuit is in the dynamic vision sensing mode, the third comparator is used to compare the voltage of the second differential signal with the voltage of the negative threshold voltage signal. A second digital image signal is output when the voltage is greater than or equal to the voltage of the negative threshold voltage signal, and a third digital image signal is output when the voltage of the second differential signal is less than the voltage of the negative threshold voltage signal.

A second aspect of the embodiments of the present application provides an image sensor, including an image sensor circuit array composed of M rows×N columns of image sensor circuits as described in the first aspect of the embodiments of the present application;

Wherein, M≥1, N≥1, and M and N are integers.

A third aspect of the embodiments of the present application provides a terminal device, including a processor, a display screen electrically connected to the processor, and the image sensor according to the second aspect of the embodiments of the present application;

The processor is used for:

When the display screen is off, controlling the image sensor to enter a dynamic vision sensing mode;

When the image sensor is in the dynamic vision sensing mode, detecting whether the image sensor outputs a digital image signal of the first preset target;

When the image sensor outputs the digital image signal of the first preset target, the display screen is turned on.

In an embodiment, the processor is further configured to:

When the image sensor is in a dynamic vision sensing mode, detecting whether the image sensor outputs a digital image signal of a second preset target;

When the image sensor outputs the digital image signal of the second preset target, the first preset application is run.

In an embodiment, the processor is further configured to:

When the second preset application is running, the image sensor is controlled to enter the image sensing mode.

The embodiment of the application provides an image sensing circuit including a pixel structure, a correlated double sampling circuit, a path selection circuit, an analog-to-digital conversion circuit, and a comparison circuit. When in the image sensing mode, the pixel structure is detected by the correlated double sampling circuit. After an exposure is completed, the reset signal and the analog image signal output in sequence are differentiated to obtain the first differential signal, and then the first differential signal is converted into a digital image signal through an analog-to-digital conversion circuit and output, so that the complete image information of the scene can be obtained; When in the dynamic vision sensing mode, the two analog image signals output by the pixel structure after two consecutive exposures are differentiated through the correlated double sampling circuit to obtain the second differential signal, and then the second differential signal is obtained by the comparison circuit according to the second differential signal. The voltage output corresponds to the digital image signal, which can output only the address and information of the pixel whose light intensity has changed to identify the scene change.

Description of the drawings

FIG. 1 is a schematic diagram of a structure of an image sensor circuit provided by an embodiment of the application;

2 is a schematic diagram of another structure of an image sensor circuit provided by an embodiment of the application;

3 is a waveform diagram of node voltage when the image sensing circuit provided by an embodiment of the application is in an image sensing mode;

4 is a waveform diagram of node voltage when the image sensing circuit provided by an embodiment of the application is in a dynamic visual sensing mode;

FIG. 5 is a schematic structural diagram of an image sensor provided by an embodiment of the application;

FIG. 6 is a schematic structural diagram of a terminal device provided by an embodiment of the application.

Detailed ways

In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present application clearer, the following further describes the present application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application, and are not used to limit the present application.

It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top" , "Bottom", "Inner", "Outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply the device referred to. Or the element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present application.

In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present application, "multiple" means two or more than two, unless otherwise specifically defined.

As shown in FIG. 1, an embodiment of the present application provides a CMOS image sensor circuit 1, including a pixel structure 10, a correlated double sampling circuit 20, a path selection circuit 30, an analog-to-digital conversion circuit 40, and a comparison circuit 50;

The pixel structure 10, the correlated double sampling circuit 20 and the path selection circuit 30 are electrically connected in sequence, and the path selection circuit 30 is also electrically connected to the analog-to-digital conversion circuit 40 and the comparison circuit 50.

In the application, the pixel structure can be selected according to actual needs, which is suitable for the PPD pixel structure (Pinned Photodiode Pixel) of the CMOS image sensor and the correlated double sampling circuit. Correlated Double Sampling (CDS) circuit can choose a circuit structure with correlated double sampling function according to actual needs. The analog-to-digital conversion circuit can be realized by an analog-to-digital converter, an analog-to-digital conversion chip, and other electronic components with analog-to-digital conversion functions. The comparison circuit can be realized by electronic components with a comparison function such as a comparator and a comparison chip.

The working principle of the image sensor circuit 1 provided in the embodiment of the present application is as follows:

When the image sensing circuit 1 is in the image sensing mode, the path selection circuit 30 is used to switch on the electrical connection between the correlated double sampling circuit 20 and the analog-to-digital conversion circuit 40, and the pixel structure 10 is used to sequentially after one exposure is completed. The reset signal and the analog image signal are output, the correlated double sampling circuit 20 is used to differentiate the reset signal and the analog image signal to obtain the first differential signal, and the analog-to-digital conversion circuit 40 is used to convert the first differential signal into a digital image signal and then output ；

When the image sensing circuit 1 is in the dynamic visual sensing mode, the path selection circuit 30 is used to turn on the electrical connection between the correlated double sampling circuit 20 and the comparison circuit 50, and the pixel structure 10 is used to output the first exposure after one exposure is completed. An analog image signal, output a second analog image signal after the next exposure is completed, the correlated double sampling circuit 20 is used to differentiate the first analog image signal and the second analog image signal to obtain the second differential signal, and the comparison circuit 50 is used to The corresponding digital image signal is output according to the voltage level of the second differential signal.

In application, the pixel structure is connected with row scan driver, column scan driver and timing controller, and realizes its function under the driving control of row scan driver, column scan driver and timing controller. The related double sampling circuit is connected with the ramp generator and the processor, and realizes its function under the control of the ramp generator and the processor. The path selection circuit and the comparison circuit are connected to the processor, and realize their functions under the control of the processor. The processor and the timing controller can be the same device.

As shown in FIG. 2, in one embodiment, a PPD pixel structure 10 is exemplarily shown, including a photodiode PD (Photo Diode), a transfer transistor TX (transfer transistor), a reset transistor RST, and a source follower transistor SF. And row select transistor RS (Row Select);

The anode of the photodiode PD is connected to the analog ground, and the cathode is electrically connected to the input end of the transfer transistor TX. The output end of the transfer transistor TX, the output end of the reset transistor RST and the controlled end of the source follower transistor SF are electrically connected to the floating node. FD (Floating Diffusion), the input ends of the reset transistor RST and the source follower transistor SF are electrically connected to the power supply VDD, the output end of the source follower transistor SF is electrically connected to the input end of the row selection transistor RS, and the row selection transistor RS is electrically connected to the current source The correlated double sampling circuit is electrically connected to the output node OUT, and the current source is connected to the analog ground.

In applications, the transfer transistor, reset transistor, source follower transistor, and row select transistor can be selected according to actual needs of field effect transistors or triodes.

As shown in FIG. 2, in one embodiment, the correlated double sampling circuit 20 includes a capacitor C0, a first comparator U1, and a first switch S1;

The positive electrode of the capacitor C0 is electrically connected to the pixel structure 10, the negative electrode of the capacitor C0 is electrically connected to the negative input terminal of the first comparator U1 and one end of the first switch S1, and the positive input terminal of the first comparator U1 is used for access For the ramp signal, the output terminal of the first comparator U1 is electrically connected to the other terminal of the first switch S1 and the path selection circuit 30;

When the image sensing circuit 1 is in the image sensing mode, the first switch S1 is used to turn on when the pixel structure 10 outputs a reset signal, and turn off when the pixel structure 10 outputs an analog image signal, and the capacitor C0 is used to store the reset signal, The first comparator U1 is used to obtain a first differential signal after performing a difference between the reset signal and the analog image signal, and output it to the analog-to-digital conversion circuit 40;

When the image sensing circuit 1 is in the dynamic vision sensing mode, the first switch S1 is turned off, the capacitor C0 is used to store the first analog image signal, and the first comparator U1 is used to compare the first analog image signal and the second analog image. After the signals are differentiated, a second differential signal is obtained and output to the comparison circuit 50.

In application, the positive input terminal of the first comparator is used to connect a ramp generator (RAMP) to input a ramp signal. The first switch may be a single-pole single-throw analog switch or an electronic switch with the same function as the single-pole single-throw analog switch. The first switch is electrically connected to the processor, and is turned on or off under the control of the processor. FIG. 2 exemplarily shows that the first switch S1 is a single-pole single-throw analog switch.

As shown in FIG. 2, in one embodiment, the path selection circuit 30 includes a second switch S2;

The input terminal of the second switch S2 is electrically connected to the correlated double sampling circuit 20, the first output terminal of the second switch S2 is electrically connected to the analog-to-digital converter 40, and the second output terminal of the second switch is electrically connected to the comparison circuit 50. connect;

When the image sensing circuit 1 is in the image sensing mode, the input terminal and the first output terminal of the second switch S2 are turned on to connect the electrical connection between the correlated double sampling circuit 20 and the analog-to-digital conversion circuit 40;

When the image sensing circuit 1 is in the dynamic vision sensing mode, the input terminal and the second output terminal of the second switch S2 are turned on to connect the electrical connection between the correlated double sampling circuit 20 and the comparison circuit 50.

In application, the second switch can be a single-pole double-throw analog switch or an electronic switch with the same function as a single-pole double-throw analog switch. The second switch is electrically connected to the processor, and is turned on or off under the control of the processor. The single-pole double-throw analog switch can be equivalently replaced with two single-pole single-throw analog switches. Fig. 2 exemplarily shows that the second switch S2 is a single-pole double-throw analog switch.

As shown in FIG. 2, in one embodiment, the comparison circuit 50 includes a second comparator U2 and a third comparator U3;

The negative input terminal of the second comparator U2 and the negative input terminal of the third comparator U3 are electrically connected to the path selection circuit 30, and the positive input terminal of the second comparator U2 and the positive input terminal of the third comparator are used for access Threshold voltage signal;

When the image sensing circuit 1 is in the dynamic visual sensing mode, the second comparator U2 and the third comparator U3 are used to compare the voltage of the second differential signal with the voltage of the threshold voltage signal, and the second comparator U2 is in the second When the voltage of the differential signal is greater than or equal to the voltage of the threshold voltage signal, the first digital image signal is output, and the third comparator U3 outputs the second digital image signal when the voltage of the second differential signal is less than the voltage of the threshold voltage signal.

In application, the voltage of the threshold voltage signal can be set to be greater than or equal to 0V according to actual needs. When the voltage of the second differential signal is greater than the voltage of the threshold voltage signal, it indicates that the analog image signal of the pixel structure becomes stronger, that is, the voltage of the second analog image signal is greater than the voltage of the first analog image signal, and the second comparator outputs the first analog image signal. A digital image signal, which is used to characterize the analog signal of the pixel structure becoming stronger, is called an "ON" event, and the third comparator has no output; when the voltage of the second differential signal is less than the voltage of the threshold voltage signal, it indicates that the pixel structure is The analog image signal becomes weak, that is, the voltage of the second analog image signal is less than the voltage of the first analog image signal. At this time, the third comparator outputs the second digital image signal, and the analog signal used to characterize the pixel structure becomes weak, which is called In the "OFF" event, the second comparator has no output; when the voltage of the second differential signal is equal to the voltage of the threshold voltage signal, neither the second comparator nor the third comparator has an output. The first digital image signal may be a high level signal or a binary signal "1", and the second digital image signal may be a low level signal or a binary signal "0".

In one embodiment, the comparison circuit includes a second comparator;

In application, only one comparator can be used to compare the voltage of the second differential signal with the voltage of the threshold voltage signal. The voltage of the threshold voltage signal is set to be greater than or equal to 0V. When the voltage of the second differential signal is greater than the voltage of the threshold voltage signal, it indicates that the analog image signal of the pixel structure becomes stronger, that is, the voltage of the second analog image signal is greater than the voltage of the first analog image signal, and the second comparator outputs the first analog image signal. A digital image signal, which is used to characterize the analog signal of the pixel structure becoming stronger, is called an "ON" event; when the voltage of the second differential signal is less than the voltage of the threshold voltage signal, it indicates that the analog image signal of the pixel structure becomes weak, that is The voltage of the second analog image signal is less than the voltage of the first analog image signal. At this time, the second comparator outputs the second digital image signal, which is used to characterize the weakening of the analog signal of the pixel structure, which is called an "OFF" event; When the voltage of the second differential signal is equal to the voltage of the threshold voltage signal, the second comparator has no output. The first digital image signal may be a high level signal or a binary signal "1", and the second digital image signal may be a low level signal or a binary signal "0".

In the application, you can also set two threshold voltage signals of equal magnitude and opposite polarity, namely a positive threshold voltage signal and a negative threshold voltage signal. The voltage of the positive threshold voltage signal can be set to be greater than 0V according to actual needs, and the negative threshold voltage signal It is a negative value with the same polarity as the magnitude of the positive threshold voltage signal, that is, less than 0V. When the voltage of the second differential signal is greater than the voltage of the positive threshold voltage signal, the second comparator outputs the first digital image signal, and the analog signal used to characterize the pixel structure becomes stronger. At this time, the third comparator has no output; When the voltage of the differential signal is less than or equal to the voltage of the positive threshold voltage signal, the second comparator outputs a second digital image signal, which is used to characterize the analog signal of the pixel structure without change. At this time, the third comparator has no output; when the second differential When the voltage of the signal is greater than or equal to the voltage of the negative threshold voltage signal, the third comparator outputs a second digital image signal, which is used to characterize that the analog signal output by the pixel structure has not changed. At this time, the second comparator has no output; when the second differential When the voltage of the signal is less than the voltage of the negative threshold voltage signal, the third comparator outputs a third digital image signal, which is used to characterize that the analog signal output by the pixel structure becomes weak, and the second comparator has no output at this time. The first digital image signal can be a high level signal or a binary signal "1", the second digital image signal can be a 0 level signal or a binary signal "0", and the third digital image signal can be a low level signal or a binary signal "-1".

Based on the structure of the image sensing circuit 1 shown in FIG. 2, the second switch S2 turns on the electrical connection between the correlated double sampling circuit 20 and the analog-to-digital converter 40. When the image sensing circuit 1 is in the image sensing mode, The workflow of the image sensing circuit 1 is as follows:

1. Exposure. The electron-hole pairs generated by the PPD pixel structure under light irradiation are separated due to the existence of the PPD electric field, the electrons move to the n region, and the holes move to the p region.

2. Reset. At the end of the exposure, the reset transistor RST is activated to reset the readout area to a high level.

3. Reset level readout. After the resetting of the reset transistor RST is completed, the first switch S1 is turned on, the reset level is read, and the read signal is stored in the capacitor C0 of the correlation double sampling circuit 20.

4. Charge transfer. The first switch S1 is turned off, activating the transfer transistor TX, and completely transfers the charge from the photosensitive area to the n+ area for reading.

5. The signal level is read to obtain the reset signal and the analog image signal. The correlated double sampling circuit 30 differentiates the reset signal and the analog image signal to obtain the first differential signal, and the analog-to-digital conversion circuit 40 performs analog-to-digital conversion on the first differential signal. Output after getting digital image signal.

As shown in FIG. 3, it exemplarily shows the voltage of each node of the image sensing circuit 1 when the image sensing circuit 1 is in the image sensing mode; wherein, when the image sensing circuit 1 is in the reset state, RST The node level is from high to low, the RS node is at high level, the TX node is in the off state, and the first switch S1 is turned on. At this time, the electrical signal read is the reset signal level Reset level; then, the first switch S1 is disconnected, the level of the RST node changes from high to low, the RS node is high, the TX node is open, the electrical signal of the photodiode PD is transferred, and the signal level of the analog image signal is read after the RS node. Then, the reset signal and the analog image signal are differentiated through the correlated double sampling circuit to obtain the first differential signal PDSignal.

Based on the structure of the image sensing circuit 1 shown in FIG. 2, the first switch S1 is turned off, and the second switch S2 is turned on the electrical connection between the correlated double sampling circuit 20 and the comparison circuit 50, and the image sensing circuit 1 is in a dynamic state. In the visual sensing mode, the workflow of the image sensing circuit 1 is as follows:

3. Charge transfer. The transfer transistor TX is activated to completely transfer the charge from the photosensitive area to the n+ area for readout.

4. The first analog image signal level is read and stored in the capacitor C0.

5. Repeat procedures 1 to 3, read out the level of the second analog image signal to obtain the second analog image signal, the correlated double sampling circuit 30 differentiates the first analog image signal and the second analog image signal and then outputs the difference to the comparison circuit 50 for comparison , Output the first digital image signal or the second digital image signal representing the "ON" event or the "OFF" event.

As shown in FIG. 4, it exemplarily shows the voltage of each node of the image sensor circuit 1 when the image sensor circuit 1 is in the dynamic vision sensing mode; among them, the level of the first analog image signal Signal level1 readout process In, the level of the RST node is from low to high, the RS node is at high level, the TX node is in the open state, the electrical signal of the photodiode PD is transferred, and the RS node is read out and reset, and the first analog image signal is obtained at this time Signal level1; the level of the second analog image signal Signal level2 During the readout process, the level of the RST node changes from low to high, the RS node is at high level, the TX node is at the open state, and the electrical signal of the photodiode PD It is transferred out and reset after being read out by the RS node. At this time, the signal level 2 of the second analog image signal is obtained; and then the correlated double sampling circuit is used to differentiate between the first analog image signal and the second analog image signal to obtain the first analog image signal. Two differential signal Difference.

The embodiment of the application provides an image sensing circuit including a pixel structure, a correlated double sampling circuit, a path selection circuit, an analog-to-digital conversion circuit, and a comparison circuit. When in the image sensing mode, the pixel structure is detected by the correlated double sampling circuit. After an exposure is completed, the reset signal and the analog image signal output in sequence are differentiated to obtain the first differential signal, and then the first differential signal is converted into a digital image signal through the analog-to-digital conversion circuit and output, which can obtain the complete image information of the scene. In this way, the normal imaging of the scene can be realized, which can be applied to work scenes that need to be photographed, such as photographing or video recording; when in the dynamic vision sensing mode, the two output of the pixel structure after two consecutive exposures are completed through the correlated double sampling circuit. The analog image signals are differentiated to obtain the second differential signal, and then the corresponding digital image signal is output according to the voltage of the second differential signal through the comparison circuit, which can output only the address and information of the pixel whose light intensity has changed, and identify the scene change. It can be widely used in target tracking, real-time monitoring, industrial automation and robotics.

As shown in FIG. 5, an embodiment of the present application further provides an image sensor 100, which includes an image sensor circuit array composed of M rows×N columns of image sensor circuits 1;

Wherein, M≥1, N≥1, and M and N are integers.

In application, the number of image sensing circuits included in the image sensor can be set according to actual needs, and the number of image sensing circuits is proportional to the resolution of the image sensor.

The embodiments of the present application provide an image sensor composed of several image sensing circuits that can operate in an image sensing mode and a dynamic vision sensing mode, so that the image sensor can be compatible with the functions of the dynamic vision sensor, and can obtain the scene information. Complete image information, and able to identify scene changes.

As shown in FIG. 6, an embodiment of the present application further provides a terminal device 100, including a processor 200, a display screen 300 and an image sensor 100 electrically connected to the processor 200;

The processor 200 is used for:

When the display screen 300 is off, control the image sensor 100 to enter the dynamic vision sensing mode;

When the image sensor 100 is in the dynamic vision sensing mode, detecting whether the image sensor 100 outputs the digital image signal of the first preset target;

When the image sensor 100 outputs the digital image signal of the first preset target, the display screen 300 is turned on.

In applications, the processor can be a central processing unit (Central Processing Unit, CPU), or other general-purpose processors, digital image signal processors (Digital Signal Processor, DSP), application specific integrated circuits (ASICs) ), off-the-shelf programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor or the like. The processor can also be a timing controller.

In application, the display screen can be TFT-LCD (Thin Film Transistor Liquid Crystal Display), LCD (Liquid Crystal Display, liquid crystal display device), based on OLED (Organic Electroluminesence Display, organic electric laser display) technology Organic electro-laser display, quantum dot light-emitting diode display or curved display based on QLED (Quantum Dot Light Emitting Diodes) technology. Further, the display screen may also include a touch panel covering the display screen. After the touch panel detects a touch operation on or near it, it transmits it to the processor to determine the type of the touch event, and the processor then determines the type of the touch event. Provide corresponding visual output on the display.

In the application, when the display screen is off, the terminal device is in a dormant state, and the image sensor can be controlled to enter the dynamic vision sensing mode to reduce power consumption. The first preset target may be a human face, a specific gesture, or other feature points of the human body, and may also be other specific scenes related or unrelated to the human body. By illuminating the display screen when the first preset target is detected, the terminal device can be awakened to enter the working state.

In an embodiment, the processor is further configured to:

In applications, the image sensor can be in a dynamic vision sensing mode regardless of whether the terminal device is in a sleep state or a working state. The second preset target may be a specific gesture, and the first preset application may be a specific application running on the terminal device set according to actual needs, for example, call application, game application, social software, office software, etc. When a specific gesture is detected, the terminal device can be triggered to run a specific application.

In an embodiment, the processor is further configured to:

In the application, the second preset application can be a camera application, a surveillance application, a social software, a Meitu application, and other applications that have camera activation permissions and are used to implement functions such as photographing or video recording. By controlling the image when running these applications The sensor enters the image sensing mode and can obtain complete image information of the scene being photographed, thereby realizing normal imaging.

In applications, the terminal device can be a mobile phone, a tablet computer, a personal computer, a personal digital assistant, a monitoring device, or a virtual reality/augmented reality/mixed reality device with a camera or an external camera.

The above-mentioned embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, a person of ordinary skill in the art should understand that it can still implement the foregoing The technical solutions recorded in the examples are modified, or some of the technical features are equivalently replaced; these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the application, and should be included in Within the scope of protection of this application.

Claims

An image sensing circuit, which is characterized by comprising a pixel structure, a correlated double sampling circuit, a path selection circuit, an analog-to-digital conversion circuit, and a comparison circuit;

The pixel structure, the correlated double sampling circuit, and the path selection circuit are electrically connected in sequence, and the path selection circuit is also electrically connected with the analog-to-digital conversion circuit and the comparison circuit;

When the image sensing circuit is in the image sensing mode, the path selection circuit is used for turning on the electrical connection between the correlated double sampling circuit and the analog-to-digital conversion circuit, and the pixel structure is used for After one exposure is completed, a reset signal and an analog image signal are sequentially output. The correlated double sampling circuit is used to differentiate the reset signal and the analog image signal to obtain a first differential signal. The analog-to-digital conversion circuit is used to The first differential signal is converted into a digital image signal and then output;

When the image sensing circuit is in the dynamic vision sensing mode, the path selection circuit is used to turn on the electrical connection between the correlated double sampling circuit and the comparison circuit, and the pixel structure is used to The first analog image signal is output after the exposure is completed, and the second analog image signal is output after the next exposure is completed. The correlated double sampling circuit is used to differentiate the first analog image signal and the second analog image signal to obtain The second differential signal, the comparison circuit is used for outputting the corresponding digital image signal according to the voltage level of the second differential signal.
3. The image sensor circuit of claim 1, wherein the correlated double sampling circuit comprises a capacitor, a first comparator and a first switch;

The positive electrode of the capacitor is electrically connected to the pixel structure, the negative electrode of the capacitor is electrically connected to the negative input terminal of the first comparator and one end of the first switch, and the first comparator The positive input terminal of is used to access a ramp signal, and the output terminal of the first comparator is electrically connected to the other terminal of the first switch and the path selection circuit;

When the image sensing circuit is in the image sensing mode, the first switch is used to turn on when the pixel structure outputs the reset signal, and turn off when the pixel structure outputs the analog image signal, The capacitor is used to store the reset signal, and the first comparator is used to make a difference between the reset signal and the analog image signal to obtain a first differential signal and output it to the analog-to-digital conversion circuit;

When the image sensing circuit is in the dynamic vision sensing mode, the first switch is turned off, the capacitor is used to store the first analog image signal, and the first comparator is used to compare the first analog image signal After performing difference with the second analog image signal, a second difference signal is obtained and output to the comparison circuit.
3. The image sensor circuit of claim 1, wherein the path selection circuit comprises a second switch;

The input terminal of the second switch is electrically connected to the correlated double sampling circuit, the first output terminal of the second switch is electrically connected to the analog-to-digital conversion circuit, and the second output terminal of the second switch Electrically connected with the comparison circuit;

When the image sensing circuit is in the image sensing mode, the input terminal and the first output terminal of the second switch are turned on to turn on the electrical connection between the correlated double sampling circuit and the analog-to-digital conversion circuit. Sexual connection

When the image sensing circuit is in the dynamic vision sensing mode, the input terminal and the second output terminal of the second switch are turned on to turn on the electrical characteristics between the correlated double sampling circuit and the comparison circuit. connect.
5. The image sensor circuit of claim 1, wherein the comparison circuit comprises a second comparator;

The negative input terminal of the second comparator is electrically connected to the path selection circuit, and the positive input terminal of the second comparator is used to access a threshold voltage signal;

When the image sensing circuit is in the dynamic vision sensing mode, the second comparator is used to compare the voltage of the second differential signal with the voltage of the threshold voltage signal. A first digital image signal is output when the voltage of the threshold voltage signal is greater than that of the threshold voltage signal, and a second digital image signal is output when the voltage of the second differential signal is less than the voltage of the threshold voltage signal.
3. The image sensor circuit of claim 1, wherein the comparison circuit comprises a second comparator and a third comparator;

The negative input terminal of the second comparator and the negative input terminal of the third comparator are electrically connected to the path selection circuit, and the positive input terminal of the second comparator and the positive input terminal of the third comparator are electrically connected. The input terminal is used to connect the threshold voltage signal;

When the image sensing circuit is in the dynamic vision sensing mode, the second comparator and the third comparator are used to compare the voltage of the second differential signal with the voltage of the threshold voltage signal, and the The second comparator outputs the first digital image signal when the voltage of the second differential signal is greater than the voltage of the threshold voltage signal, and the third comparator outputs the first digital image signal when the voltage of the second differential signal is less than the threshold voltage signal. The second digital image signal is output when the voltage is higher.
3. The image sensor circuit of claim 1, wherein the comparison circuit comprises a second comparator and a third comparator;

The negative input terminal of the second comparator and the positive input terminal of the third comparator are electrically connected to the path selection circuit, and the positive input terminal of the second comparator is used to connect a positive threshold voltage signal, The negative input terminal of the third comparator is used to connect a negative threshold voltage signal;

When the image sensing circuit is in the dynamic vision sensing mode, the second comparator is used to compare the voltage of the second differential signal with the voltage of the positive threshold voltage signal. Output a first digital image signal when the voltage is greater than the voltage of the positive threshold voltage signal, and output a second digital image signal when the voltage of the second differential signal is less than or equal to the voltage of the positive threshold voltage signal;

When the image sensing circuit is in the dynamic vision sensing mode, the third comparator is used to compare the voltage of the second differential signal with the voltage of the negative threshold voltage signal. A second digital image signal is output when the voltage is greater than or equal to the voltage of the negative threshold voltage signal, and a third digital image signal is output when the voltage of the second differential signal is less than the voltage of the negative threshold voltage signal.
7. The image sensor circuit according to any one of claims 1 to 6, wherein the pixel structure realizes functions under the driving control of an externally connected row scan driver, column scan driver, and timing controller.
3. The image sensor circuit of claim 2, wherein the correlated double sampling circuit realizes functions under the control of an external ramp generator RAMP and a processor.
The image sensor circuit of claim 8, wherein the positive input terminal of the first comparator is used to connect the ramp generator RAMP to input a ramp signal; the first switch and the processor The electrical connection is turned on or off under the control of the processor.
5. The image sensor circuit of claim 3, wherein the path selection circuit and the comparison circuit implement functions under the control of an external processor.
10. The image sensor circuit of claim 10, wherein the second switch is electrically connected to the processor, and is turned on or off under the control of the processor.
The image sensor circuit of claim 1, wherein the pixel structure includes a photodiode PD, a transfer transistor TX, a reset transistor RST, a source follower transistor SF, and a row selection transistor RS; wherein,

The anode of the photodiode PD is connected to the analog ground, and the cathode is electrically connected to the input terminal of the transfer transistor TX. The output terminal of the transfer transistor TX is connected to the output terminal of the reset transistor RST and the source follower transistor SF. The controlled terminal is electrically connected to the floating node FD in common, the input terminals of the reset transistor RST and the source follower transistor SF are electrically connected to the power supply VDD, and the output terminal of the source follower transistor SF is electrically connected to the row selection transistor RS The input terminal of is electrically connected, the row selection transistor RS, the current source and the correlated double sampling circuit are electrically connected to the output node OUT, and the current source is connected to analog ground.
The image sensor circuit of claim 12, wherein the transfer transistor TX, the reset transistor RST, the source follower transistor SF, and the row selection transistor RS are field effect transistors or triodes.
An image sensor, characterized by comprising an image sensor circuit array composed of the image sensor circuit according to any one of claims 1 to 13 in M rows×N columns;

Wherein, M≥1, N≥1, and M and N are integers.
The image sensor of claim 14, wherein the number of the image sensing circuits is proportional to the resolution of the image sensor.
A terminal device, characterized by comprising a processor, a display screen electrically connected to the processor, and the image sensor according to claim 14;

The processor is used for:

When the display screen is off, controlling the image sensor to enter a dynamic vision sensing mode;

When the image sensor is in a dynamic vision sensing mode, detecting whether the image sensor outputs a digital image signal of a first preset target;

When the image sensor outputs the digital image signal of the first preset target, the display screen is turned on.
The terminal device of claim 16, wherein the processor is further configured to:

When the image sensor is in a dynamic vision sensing mode, detecting whether the image sensor outputs a digital image signal of a second preset target;

When the image sensor outputs the digital image signal of the second preset target, the first preset application is run.
The terminal device of claim 17, wherein the second preset target is a specific gesture.
The terminal device according to any one of claims 16 to 18, wherein the processor is further configured to:

When the second preset application is running, the image sensor is controlled to enter the image sensing mode.
The terminal device according to claim 19, wherein the second preset application is an application with camera activation permission.