CN-119922428-B - Pixel array reading method and image sensor

CN119922428BCN 119922428 BCN119922428 BCN 119922428BCN-119922428-B

Abstract

The invention provides a pixel array reading method and an image sensor, which are realized based on a plurality of pixel units arranged in an array, wherein each pixel unit at least comprises a photoelectric conversion module, a floating storage module and a reading module, the pixel array reading method comprises the steps of resetting the floating storage module, exposing the photoelectric conversion module, keeping the floating storage module conductive to output charge signals to the floating storage module, firstly reading out image signals of the floating storage module, resetting the floating storage module, and then reading out reset signals of the floating storage module, and obtaining real signals of the floating storage module based on the image signals and the reset signals so as to reduce noise introduced when the photoelectric conversion module outputs the charge signals to the floating storage module. The invention reads the reset signal and the image signal corresponding to the switching tube connected with the photodiode in a quantification way, thereby effectively avoiding the signal noise introduced by operating the switching tube.

Inventors

HU ZEWANG
ZHANG SHENGXIN
YU HAIYU

Assignees

思特威(上海)电子科技股份有限公司

Dates

Publication Date: 20260508
Application Date: 20231023

Claims (14)

1. The pixel array comprises a plurality of pixel units which are arranged in an array; each pixel unit at least comprises a photoelectric conversion module, a floating storage module and a reading module, wherein the photoelectric conversion module receives optical signals and converts the optical signals into charge signals, the floating storage module receives and stores the charge signals, and the reading module is used for reading out the charge signals stored by the floating storage module, and the pixel array reading method is characterized by comprising the following steps: resetting the floating memory module and exposing the photoelectric conversion module, and keeping the floating memory module conductive to output the charge signal to the floating memory module or store the charge signal in the photoelectric conversion module; firstly reading out an image signal of the floating memory module, resetting the floating memory module and reading out a reset signal of the floating memory module, and obtaining a real signal of the floating memory module based on the image signal and the reset signal; When the floating memory module comprises a first charge storage area, a second charge storage area and a first gain switch tube arranged between the first charge storage area and the second charge storage area, the first charge storage area is used for receiving and storing charge signals overflowed by the photoelectric conversion module, and the second charge storage area is used for receiving the charge signals overflowed by the photoelectric conversion module under the conduction of the first gain switch tube, the pixel array reading method comprises an exposure step and/or a reading step, wherein: the exposure step includes: exposing the photoelectric conversion module when the first gain switching tube is turned on to input the converted charge signal to the first charge storage region and the second charge storage region or store the converted charge signal in the photoelectric conversion module; the reading step includes: Maintaining the first gain switching transistor on and reading the first image signal and the first reset signal of the first charge storage region and the second charge storage region, obtaining the real signals of the first charge storage region and the second charge storage region based on the difference between the first image signal and the first reset signal, and Closing the first gain switching tube, reading a second image signal and a second reset signal of the first charge storage region, and calculating a difference between the second image signal and the second reset signal to obtain a real signal of the first charge storage region; The charge signals converted by the photoelectric conversion modules are stored in the photoelectric conversion modules, and charges overflowed by the photoelectric conversion modules are distributed at least in the storage nodes corresponding to the first charge storage areas and the storage nodes corresponding to the second charge storage areas.
2. The method according to claim 1, wherein when the floating memory module includes a first charge storage region, a second charge storage region, a third charge storage region, a first gain switching transistor is disposed between the first charge storage region and the second charge storage region, and a second gain switching transistor is disposed between the second charge storage region and the third charge storage region, the first charge storage region is configured to receive and store a charge signal overflowed from the photoelectric conversion module, the second charge storage region is configured to receive the charge signal overflowed from the photoelectric conversion module when the first gain switching transistor is turned on, and the third charge storage region is configured to receive the charge signal overflowed from the photoelectric conversion module when the second gain switching transistor is turned on, the method comprises an exposure step and/or a readout step, wherein: the exposure step includes: Exposing the photoelectric conversion module when the first gain switching tube and the second gain switching tube are both on, so as to input the converted charge signals to the first charge storage region, the second charge storage region and the third charge storage region or store the converted charge signals in the photoelectric conversion module; the reading step includes: maintaining the first and second gain switches on and reading the third image signals and the third reset signals of the first, second and third charge storage areas, obtaining the true signals of the first, second and third charge storage areas based on the difference between the third image signals and the third reset signals, and Closing the second gain switching transistor and reading a fourth image signal and a fourth reset signal of the first charge storage region and the second charge storage region, obtaining real signals of the first charge storage region and the second charge storage region based on a difference calculation between the fourth image signal and the fourth reset signal, and And reading the fifth image signal and the fifth reset signal of the first charge storage region, and calculating to obtain the real signal of the first charge storage region based on the difference between the fifth image signal and the fifth reset signal.
3. The method for reading a pixel array according to claim 2, wherein the readout sequence of the fourth image signal, the fourth reset signal, the fifth image signal, and the fifth reset signal includes: A fourth reset signal that reads the first charge storage region and the second charge storage region based on the first gain switch being turned on; reading a fifth reset signal of the first charge storage region and a fifth image signal of the first charge storage region based on the first gain switching transistor turn-off; And a fourth image signal based on the first gain switching transistor turn-on read and the first charge storage region and the second charge storage region.
4. The method of reading a pixel array of claim 3 wherein said pixel cell further comprises a reset tube for resetting at least one of said first charge storage region, said second charge storage region, and said third charge storage region, wherein said reset tube is continuously turned on during reading of said fourth reset signal, said fourth image signal, said fifth reset signal, and said fifth image signal.
5. The method for reading a pixel array according to any one of claims 1 to 4, further comprising setting the photoelectric conversion module to be partially turned on after resetting the floating storage module and when exposing the photoelectric conversion module to light, so as to output the charge signal to the floating storage module.
6. The method of claim 5, wherein setting the photoelectric conversion module to be partially on comprises lowering a transfer tube of the photoelectric conversion module from a first level to a second level to close the transfer tube before the resetting the floating storage module to close the corresponding reset tube, and raising the transfer tube from the second level to a third level smaller than the first level after the resetting the floating storage module to close the corresponding reset tube.
7. An image sensor comprising a pixel array for implementing the pixel array reading method according to any one of claims 1-6, wherein the pixel array comprises a plurality of pixel units arranged in an array; Each pixel unit at least comprises a photoelectric conversion module, a floating storage module and a reading module, wherein the photoelectric conversion module receives optical signals and converts the optical signals into charge signals, the floating storage module receives and stores the charge signals, and the reading module is used for reading out signals stored by the floating storage module.
8. The image sensor of claim 7, wherein: the photoelectric conversion module includes a photodiode and a transfer tube, wherein: The control end of the transmission tube is connected with a first switch control signal, and the photodiode is connected to the floating storage module through the transmission tube and is used for receiving the optical signal and transferring the converted charge signal to the floating storage module; and/or, the reading module comprises an output tube and/or a selection tube, wherein: the first end of the output pipe is connected with the floating storage module, the second end of the output pipe is connected with the power supply voltage, and the third end of the output pipe is connected with the first end of the selection pipe and is used for amplifying an output signal of the floating storage module; The control end of the selection tube is connected with a reading switch signal, the second end is used as the output end of the reading module, and the selection tube is conducted based on the reading switch signal so as to output the output signal of the output tube; and/or the floating memory module includes a first charge storage region, a second charge storage region, and a first gain switching tube disposed between the first charge storage region and the second charge storage region, wherein: the first charge storage region is for receiving and storing a charge signal output from the photoelectric conversion module, The control end of the first gain switching tube is connected with a second switch control signal, the first gain switching tube is turned on or turned off based on the second switch control signal, The second charge storage region receives a charge signal output by the first charge storage region under the conduction of the first gain switch tube.
9. The image sensor of claim 8, wherein the first charge storage region is configured as a first floating diffusion node, the second charge storage region comprises a second floating diffusion node, a first plate of the first capacitor is grounded, a second plate is connected to the second floating diffusion node, and the second floating diffusion node is connected to the first floating diffusion node via the first gain switching tube.
10. The image sensor of claim 8, wherein the floating memory module further comprises a third charge storage region and a second gain switching tube disposed between the second charge storage region and the third charge storage region; The control end of the second gain switching tube is connected with a third switch control signal, and the second gain switching tube is turned on or turned off based on the third switch control signal; The third charge storage region receives the charge signal output by the second charge storage region under the conduction of the second gain switch tube.
11. The image sensor of claim 10, wherein the third charge storage region comprises a second capacitor, the first plate is grounded, and the second plate is connected to the second charge storage region via the second gain switch.
12. The image sensor of any one of claims 7-11, wherein each pixel unit further comprises a reset tube with a control end connected with a reset switch signal, a first end connected with a power supply voltage, and a second end connected with the floating storage module.
13. The image sensor of claim 12, wherein: When the floating storage module comprises a first charge storage area, a second charge storage area and a first gain switching tube arranged between the first charge storage area and the second charge storage area, a first end of the reset tube is connected with a power supply voltage, and a second end of the reset tube is connected with the second charge storage area; When the floating memory module includes a first charge storage region, a second charge storage region, a third charge storage region, a first gain switching transistor is disposed between the first charge storage region and the second charge storage region and a second gain switching transistor is disposed between the second charge storage region and the third charge storage region, The first end of the reset tube is connected with a power supply voltage, the second end of the reset tube is connected with the third charge storage region or the second end of the reset tube is connected with a connecting node between the second charge storage region and the third charge storage region.
14. The image sensor of claim 13, wherein when the floating memory module comprises a first charge storage region, a second charge storage region, a third charge storage region, a first gain switching tube is disposed between the first charge storage region and the second charge storage region, and a second gain switching tube is disposed between the second charge storage region and the third charge storage region, a first terminal of the reset tube is connected to a supply voltage, a second terminal is connected to a connection node between the second charge storage region and the third charge storage region, the pixel cell further comprises an additional reset tube; The control end of the additional reset tube receives an additional reset signal, the first end is connected with a power supply voltage, the second end is connected with the third charge storage region, and when the third charge storage region comprises a second capacitor, the second end is connected with a second capacitor plate.

Description

Pixel array reading method and image sensor Technical Field The present invention relates to the field of image sensing, and in particular, to a pixel array reading method and an image sensor. Background Along with the development of chip integration, the CMOS sensor evolves towards smaller volume and lower power consumption, and is increasingly applied to the fields of monitoring, vehicle-mounted and artificial intelligence, and meanwhile, the requirements on certain performances of the CMOS image sensor are also higher and higher under different application scenes. For the field of vehicle-mounted monitoring, some image sensors need to monitor the scene outside the vehicle, wherein traffic lamps are involved, usually, the traffic lamps are stroboscopic LEDs, a chip needs to have enough exposure time to cover the stroboscopic period of the LEDs so as to capture the 'bright' image information of the LEDs, but at the same time, the scene outside the vehicle contains some highlight signals, such as the light of a tunnel outlet, the sun of the sky, the light of a car close to the vehicle, the light of a license plate when reflecting light, and the like, so that the sensor can cover the stroboscopic period of the LEDs in long exposure and can capture the information of a strong light area in long exposure time without being exposed, and the sensor needs to have larger full-well capacity. The area requirement of the existing pixel exposure conversion storage signal at least comprises a photodiode, a switching tube and a storage area, and charge signals are input and output through the on and off of the switching tube, so that the subsequent quantitative reading is facilitated. However, the conventional pixel array reading method often keeps the switching transistor connected to the photodiode closed during the exposure period and is turned on again during the readout period, on the one hand, a part of noise is introduced, on the other hand, a part of voltage change is coupled to the storage area due to the on-state action of the switching transistor, and the additional design of sequential logic or subsequent signal processing is needed to compensate the change of charge signals caused by the coupling, and in addition, a part of capacity of the photodiode is wasted due to the manner of completely transferring the charge in the photodiode to the storage area during the quantization period. Based on the above, the invention provides a new pixel array reading method, a pixel array and an image sensor, so as to solve the problems of noise, complex time sequence design, incapability of better utilizing diode capacity and the like introduced by the existing pixel array reading method. It should be noted that the foregoing description of the background art is only for the purpose of providing a clear and complete description of the technical solution of the present application and is presented for the convenience of understanding by those skilled in the art. The above-described solutions are not considered to be known to the person skilled in the art simply because they are set forth in the background of the application section. Disclosure of Invention In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a pixel array reading method, a pixel array and an image sensor including the pixel array, which are used for solving the problems of noise, complex timing design, and no better utilization of diode capacity, which are introduced in the pixel array reading method in the prior art. The invention provides a pixel array reading method for achieving the above aim and other related aims, wherein the pixel array comprises a plurality of pixel units which are arranged in an array, each pixel unit at least comprises a photoelectric conversion module, a floating storage module and a reading module, wherein the photoelectric conversion module receives an optical signal and converts the optical signal into a charge signal; the pixel array reading method comprises the following steps: Resetting the floating memory module and exposing the photoelectric conversion module, keeping the floating memory module on to output the charge signal to the floating memory module or store the charge signal in the photoelectric conversion module, firstly reading out the image signal of the floating memory module, then resetting the floating memory module and reading out the reset signal of the floating memory module, obtaining the real signal of the floating memory module based on the image signal and the reset signal, and reducing noise introduced when the photoelectric conversion module outputs the charge signal to the floating memory module based on the exposure reading out. Optionally, when the floating memory module includes a first charge storage region, a second charge storage region, and a first gain switch tube disposed between the first charge storage region and the second charge sto