Pixel array reading method and image sensor

Abstract

The application 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 comprises at least a photoelectric conversion module, a floating storage module and a reading module; the pixel array reading method comprises the following steps: resetting the floating storage module, exposing the photoelectric conversion module and keeping the floating storage module conducting to output a charge signal to the floating storage module; first reading out an image signal of the floating storage module, then resetting the floating storage module and reading out a reset signal of the floating storage module; and obtaining a real signal of the floating storage module based on the image signal and the reset signal, so as to reduce the noise introduced when the photoelectric conversion module outputs the charge signal to the floating storage module. The application first quantitatively reads the reset signal and the image signal corresponding to the switch tube connected with the photodiode, thereby effectively avoiding the signal noise introduced by the operation of the switch tube.

Description

Technical Field

[0001] This invention relates to the field of image sensing, and in particular to a pixel array reading method and an image sensor. Background Technology

[0002] With the development of chip integration, CMOS sensors are evolving towards smaller size and lower power consumption, and their applications in monitoring, automotive, and artificial intelligence fields are increasing. At the same time, the performance requirements for CMOS image sensors are becoming increasingly stringent in different application scenarios. In the field of automotive monitoring, some image sensors need to monitor scenes outside the vehicle, including traffic lights. Traffic lights are typically flickering LEDs, requiring the chip to have a sufficiently long exposure time to cover the LED's flicker cycle in order to capture the "bright" image information. However, the scene outside the vehicle also contains some bright signals, such as the light at tunnel exits, the sun in the sky, the headlights of nearby cars, and the glare from license plates. Therefore, the sensor needs to have a large full-well capacity to cover the LED flicker cycle during long exposures while capturing information from areas of strong light without overexposure.

[0003] Existing pixel exposure conversion and signal storage areas require at least a photodiode, a switching transistor, and a storage area. The charge signal is input and output via the switching transistor's on / off state, facilitating subsequent quantization and readout. However, current pixel array readout methods often keep the switching transistor connected to the photodiode off during exposure and turn it on during readout. This introduces noise, and the voltage change caused by the switching transistor's activation is coupled to the storage area, requiring additional timing logic design or subsequent signal processing to compensate for the charge signal change due to coupling. Furthermore, transferring all the charge from the photodiode to the storage area during quantization wastes some of the photodiode's capacity.

[0004] Based on this, the present invention provides a new pixel array reading method, as well as a pixel array and an image sensor, to solve the problems introduced by existing pixel array reading methods, such as noise, complex timing design, and inability to better utilize diode capacity.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a pixel array reading method, a pixel array, and an image sensor containing the pixel array, so as to solve the problems of noise, complex timing design, and inability to better utilize diode capacity introduced by the pixel array reading method in the prior art.

[0007] To achieve the above and other related objectives, the present invention provides a pixel array reading method; the pixel array includes a plurality of pixel units arranged in an array; wherein each pixel unit includes at least a photoelectric conversion module, a floating storage module, and a reading module; the photoelectric conversion module receives an optical signal and converts it into a charge signal; the floating storage module receives and stores the charge signal; and the reading module is used to read out the charge signal stored in the floating storage module.

[0008] The pixel array reading method includes:

[0009] The floating storage module is reset and the photoelectric conversion module is exposed, keeping the floating storage module on to output the charge signal to the floating storage module or store the charge signal in the photoelectric conversion module; the image signal of the floating storage module is read out first, then the floating storage module is reset and the reset signal of the floating storage module is read out, and the real signal of the floating storage module is obtained based on the image signal and the reset signal; the noise introduced when the photoelectric conversion module outputs the charge signal to the floating storage module is reduced based on the exposure readout.

[0010] Optionally, when the floating storage module includes a first charge storage area, a second charge storage area, and a first gain switch is disposed between the first charge storage area and the second charge storage area; the first charge storage area is used to receive and store the charge signal overflowing from the photoelectric conversion module; and the second charge storage area receives the charge signal overflowing from the photoelectric conversion module when the first gain switch is turned on, the pixel array readout method includes an exposure step and / or a readout step, wherein:

[0011] The exposure steps include:

[0012] When the first gain switch is turned on, the photoelectric conversion module is exposed so as to input the converted charge signal into the first charge storage area and the second charge storage area or to store the converted charge signal in the photoelectric conversion module;

[0013] The readout step includes:

[0014] Keeping the first gain switch on and reading the first image signal and the first reset signal of the first and second charge storage regions, the actual signals of the first and second charge storage regions are calculated based on the difference between the first image signal and the first reset signal; and

[0015] The first gain switch is turned off, and the second image signal and the second reset signal of the first charge storage area are read. The real signal of the first charge storage area is obtained by calculating the difference between the second image signal and the second reset signal.

[0016] Optionally, when the floating storage module includes a first charge storage area, a second charge storage area, a third charge storage area, a first gain switch is disposed between the first charge storage area and the second charge storage area, and a second gain switch is disposed between the second charge storage area and the third charge storage area; the first charge storage area is used to receive and store the charge signal overflowing from the photoelectric conversion module; the second charge storage area receives the charge signal overflowing from the photoelectric conversion module when the first gain switch is turned on; and the third charge storage area receives the charge signal overflowing from the photoelectric conversion module when the second gain switch is turned on, the pixel array readout method includes an exposure step and / or a readout step, wherein:

[0017] The exposure steps include:

[0018] The photoelectric conversion module is exposed when both the first gain switch and the second gain switch are turned on, so as to input the converted charge signal into the first charge storage area, the second charge storage area and the third charge storage area or store the converted charge signal in the photoelectric conversion module.

[0019] The readout step includes:

[0020] Keeping the first gain switch and the second gain switch on, and reading the third image signal and the third reset signal of the first charge storage area, the second charge storage area, and the third charge storage area, respectively; calculating the difference between the third image signal and the third reset signal to obtain the actual signals of the first charge storage area, the second charge storage area, and the third charge storage area; and...

[0021] The second gain switch is turned off, and the fourth image signal and the fourth reset signal of the first and second charge storage regions are read. The actual signals of the first and second charge storage regions are calculated by subtracting the fourth image signal from the fourth reset signal.

[0022] The fifth image signal and the fifth reset signal of the first charge storage area are read, and the real signal of the first charge storage area is obtained by calculating the difference between the fifth image signal and the fifth reset signal.

[0023] Optionally, the readout order of the fourth image signal, the fourth reset signal, the fifth image signal, and the fifth reset signal includes:

[0024] The fourth reset signal is read based on the conduction of the first gain switch to read the first charge storage area and the second charge storage area;

[0025] The first gain switch is used to turn off the fifth reset signal for reading the first charge storage area and the fifth image signal for the first charge storage area.

[0026] The fourth image signal is read based on the first gain switch being turned on and the first charge storage area and the second charge storage area.

[0027] Optionally, the pixel unit further includes a reset transistor for resetting at least one of the first charge storage region, the second charge storage region, and the third charge storage region; wherein the reset transistor is continuously turned on during the reading of the fourth reset signal, the fourth image signal, the fifth reset signal, and the fifth image signal.

[0028] Optionally, the pixel array reading method further includes setting the photoelectric conversion module to partial conduction after resetting the floating storage module and exposing the photoelectric conversion module, so as to output the charge signal to the floating storage module.

[0029] Optionally, setting the photoelectric conversion module to a partially conducting mode includes: before resetting the floating storage module to turn off the corresponding reset transistor, lowering the transmission transistor of the photoelectric conversion module from a first level to a second level to turn off the transmission transistor, and after resetting the floating storage module to turn off the corresponding reset transistor, raising the transmission transistor from the second level to a third level lower than the first level.

[0030] To achieve the above and other related objectives, the present invention provides a pixel array for implementing the aforementioned pixel array reading method. The pixel array includes a plurality of pixel units arranged in an array. Each pixel unit includes at least a photoelectric conversion module, a floating storage module, and a reading module. The photoelectric conversion module receives an optical signal and converts it into a charge signal. The floating storage module receives and stores the charge signal. The reading module is used to read out the signal stored in the floating storage module.

[0031] To achieve the above and other related objectives, the present invention provides an image sensor, including a pixel array, wherein the pixel array is used to implement the pixel array reading method described in any of the above claims, the pixel array including a plurality of pixel units arranged in an array; wherein each pixel unit includes at least a photoelectric conversion module, a floating storage module and a reading module; the photoelectric conversion module receives an optical signal and converts it into a charge signal; the floating storage module receives and stores the charge signal; and the reading module is used to read out the signal stored in the floating storage module.

[0032] Optionally, the photoelectric conversion module includes a photodiode and a transmission tube, wherein:

[0033] The control terminal of the transmission tube is connected to the first switch control signal, and the photodiode is connected to the floating storage module via the transmission tube to receive the optical signal and transfer the converted charge signal to the floating storage module.

[0034] Optionally, the reading module includes an output tube and / or a selection tube, wherein:

[0035] The first end of the output transistor is connected to the floating memory module, the second end is connected to the power supply voltage, and the third end is connected to the first end of the selection transistor, so as to amplify the output signal of the floating memory module.

[0036] The control terminal of the selection tube is connected to the read switch signal, and the second terminal serves as the output terminal of the readout module. The selection tube is turned on based on the read switch signal to output the output signal of the output tube.

[0037] Optionally, the floating storage module includes a first charge storage region, a second charge storage region, and a first gain switch transistor disposed between the first charge storage region and the second charge storage region, wherein:

[0038] The first charge storage area is used to receive and store the charge signal output by the photoelectric conversion module.

[0039] The control terminal of the first gain switch is connected to a second switch control signal, which causes the first gain switch to be turned on or off.

[0040] The second charge storage region receives the charge signal output by the first charge storage region when the first gain switch is turned on.

[0041] Optionally, the first charge storage region is configured as a first floating diffusion node; the second charge storage region includes a second floating diffusion node and a first capacitor; the first plate of the first capacitor is grounded, and the second plate is connected to the second floating diffusion node; the second floating diffusion node is connected to the first floating diffusion node via the first gain switch.

[0042] Optionally, the floating storage module further includes a third charge storage region and a second gain switch disposed between the second charge storage region and the third charge storage region;

[0043] The control terminal of the second gain switch is connected to a third switch control signal, and the second gain switch is turned on or off based on the third switch control signal.

[0044] The third charge storage region receives the charge signal output by the second charge storage region when the second gain switch is turned on.

[0045] Optionally, the third charge storage region includes a second capacitor, with the first plate grounded and the second plate connected to the second charge storage region via the second gain switch.

[0046] Optionally, each pixel unit also includes a reset transistor whose control terminal is connected to a reset switch signal, whose first terminal is connected to the power supply voltage, and whose second terminal is connected to the floating memory module.

[0047] Optionally, when the floating storage module includes a first charge storage area, a second charge storage area, and a first gain switch transistor disposed between the first charge storage area and the second charge storage area, the first end of the reset transistor is connected to the power supply voltage, and the second end is connected to the second charge storage area;

[0048] When the floating storage module includes a first charge storage region, a second charge storage region, a third charge storage region, a first gain switch is disposed between the first charge storage region and the second charge storage region, and a second gain switch is disposed between the second charge storage region and the third charge storage region,

[0049] The first end of the reset tube is connected to the power supply voltage, and the second end is connected to the third charge storage area or the second end is connected to the connection node between the second charge storage area and the third charge storage area.

[0050] Optionally, when the floating storage module includes a first charge storage area, a second charge storage area, a third charge storage area, a first gain switch is disposed between the first charge storage area and the second charge storage area, and a second gain switch is disposed between the second charge storage area and the third charge storage area, the first end of the reset tube is connected to the power supply voltage, and the second end is connected to the connection node between the second charge storage area and the third charge storage area, the pixel unit further includes an additional reset tube;

[0051] The control terminal of the additional reset tube receives an additional reset signal. The first terminal is connected to the power supply voltage, and the second terminal is connected to the third charge storage area. When the third charge storage area includes a second capacitor, the second terminal is connected to the second capacitor plate.

[0052] As described above, the pixel array readout method and pixel array of the present invention have the following beneficial effects: The pixel array readout method of the present invention effectively avoids signal noise in the final readout signal caused by operating the switch connected to the photodiode by first quantizing and reading the reset signal and image signal corresponding to the switch connected to the photodiode. The pixel array readout method of the present invention ensures that the switch can effectively leak and transfer the charge signal converted by the photodiode PD to the storage area by setting the switch to maintain a subthreshold state, thus effectively utilizing the storage space of each storage device. The pixel array readout method of the present invention is simple, and the pixel array structure of the present invention is simple, making it well applicable to the field of image sensing. Attached Figure Description

[0053] Figure 1 The diagram shown is a structural schematic of the first pixel unit of the present invention.

[0054] Figure 2 Displayed as Figure 1 Timing diagram of the pixel unit reading method.

[0055] Figures 3-7 Displayed as Figure 1 A schematic diagram of charge signal transfer in pixel units in small signal mode.

[0056] Figures 8 to 14 Displayed as Figure 1 A schematic diagram of charge signal transfer in pixel units under large signal mode.

[0057] Figure 15 The diagram shown is a structural schematic of the second type of pixel unit of the present invention.

[0058] Figure 16 The diagram shown is another example of the structure of the second type of pixel unit of the present invention.

[0059] Figure 17 The diagram shown is a structural schematic of the third type of pixel unit of the present invention.

[0060] Figure 18 Displayed as Figure 17 Timing diagram of the pixel unit reading method.

[0061] Figure 19 Displayed as Figure 17 Timing diagram of the pixel unit reading method.

[0062] Component designation explanation

[0063] 1 pixel unit

[0064] 11. Photoelectric conversion module

[0065] 12 Floating Storage Modules

[0066] 13 Reading Module

[0067] 2-pixel unit

[0068] 21 Floating Storage Module

[0069] 22 Floating Storage Modules Detailed Implementation

[0070] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0071] Please see Figures 1 to 19 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0072] Example 1

[0073] like Figure 1 As shown, this embodiment provides a pixel array reading method, implemented based on the pixel array described below. The pixel array provided in this embodiment includes:

[0074] like Figure 1As shown, the pixel array includes a plurality of pixel units 1 arranged in an array; wherein each pixel unit 1 includes at least a photoelectric conversion module 11, a floating storage module 12, and a reading module 13; the photoelectric conversion module 11 receives light signals and converts them into charge signals; the floating storage module 12 receives and stores the charge signals; and the reading module 13 is used to read out the charge signals stored in the floating storage module 12.

[0075] Specifically, the photoelectric conversion module 11 includes a photodiode PD and a transmission transistor TX; the control terminal of the transmission transistor TX is connected to a first switch control signal; the photodiode PD is connected to the floating storage module 12 via the transmission transistor TX, and is used to receive optical signals and convert them into charge signals, and output the converted charge signals to the floating storage module 12 when the transmission transistor TX is turned on. In this embodiment, the transmission transistor and the photodiode are arranged in a one-to-one correspondence. In other examples, they can also be shared. In addition, the number of photodiodes can be determined according to actual needs. A pixel unit can include at least two photodiodes, and at least two photodiodes share the pixel transistor in the pixel unit, such as an output transistor, a reset transistor, etc.

[0076] Specifically, the floating storage module 12 includes a first charge storage area, a second charge storage area, and a first gain switch SWT1 disposed between the first charge storage area and the second charge storage area; the first charge storage area is used to receive and store the charge signal output by the photoelectric conversion module 11; the control terminal of the first gain switch SWT1 is connected to a second switch control signal, and the first gain switch SWT1 is turned on or off based on the second switch control signal; the second charge storage area receives the charge signal output by the first charge storage area when the first gain switch is turned on.

[0077] As an example, such as Figure 1As shown, the first charge storage area is configured as a first floating diffusion node FD1; the second charge storage area includes a second floating diffusion node FD2 and a first capacitor MIM1; the first plate of the first capacitor MIM1 is grounded, and the second plate is connected to the second floating diffusion node FD2; the second floating diffusion node FD2 is connected to the first floating diffusion node FD1 via the first gain switch SWT1. In this example, when the first gain switch SWT1 is turned on, the charge signal overflowing from the photoelectric conversion module 11 flows to the first floating diffusion node FD1, the second floating diffusion node FD2, and the first capacitor for storage. The first capacitor MIM1, with its certain charge storage capacity, ensures that even under strong light signals, a large amount of charge signal from the pixel unit 1 can still be effectively stored by the first capacitor MIM1. Of course, under weak light signals, the charge signal from photoelectric conversion can be stored in the photoelectric conversion module.

[0078] It should be noted that, in order to ensure that enough charge signal can be stored, in this embodiment, the capacitor is set to a MIM capacitor (Metal-Insulator-Metal, MIM), but it can also be set to any type of capacitor such as a MOM capacitor (Metal-Oxide-Metal, MOM), and is not limited to this embodiment.

[0079] Specifically, each pixel unit 1 also includes a reset transistor RST whose control terminal is connected to a reset switch signal; the first end of the reset transistor RST is connected to the power supply voltage VDD, and the second end is connected to the second charge storage area (in this embodiment, the second floating diffusion node FD2, that is, the second end is connected between the second floating diffusion node FD2 and the first capacitor MIM1). The voltage of the power supply voltage VDD is introduced to the corresponding position through the reset transistor RST, thereby realizing the reset.

[0080] Specifically, the read module 13 includes an output transistor SF and a selection transistor Row_SEL. The first end of the output transistor SF is connected to the floating memory module 12, the second end is connected to the power supply voltage VDD, and the third end is connected to the first end of the selection transistor Row_SEL, which is used to output the output signal of the floating memory module 12, such as a source follower transistor. The control end of the selection transistor Row_SEL is connected to the read switch signal, and the second end serves as the output end of the read module 12. Based on the read switch signal, the selection transistor Row_SEL is turned on to output the output signal of the output transistor SF.

[0081] It should be noted that the pixel array reading method provided in this embodiment is not limited to the pixel array provided above. Pixel arrays composed of pixel units including photoelectric conversion module 11, floating storage module 12 and reading module 13 are all within the protection scope of this embodiment.

[0082] This embodiment provides a pixel array reading method, including:

[0083] The floating storage module 12 is reset and the photoelectric conversion module 11 is exposed. While the floating storage module 12 remains on, the charge signal generated by the photoelectric conversion module 11 is output to the floating storage module 12. It is understood that when the corresponding light intensity is weak, the charge signal generated by the photoelectric conversion module 11 can also be stored in the photoelectric conversion element of the photoelectric conversion module 11. During the resetting and exposure sequence, the image signal of the floating storage module 12 is read out first, then the floating storage module 12 is reset and its reset signal is read out. Based on the image signal and the reset signal, the true signal of the floating storage module 12 is obtained. Through this exposure readout method, the noise introduced when the photoelectric conversion module 11 outputs its charge signal to the floating storage module 12 can be reduced. Furthermore, it avoids the voltage change caused by the opening action of the connection switch from coupling to the first and second storage areas, thus avoiding the need for additional timing and subsequent signal processing to compensate for the signal change caused by coupling.

[0084] Specifically, in this embodiment, when the floating storage module 12 includes a first charge storage region, a second charge storage region, and a first gain switch SWT1 is disposed between the first charge storage region and the second charge storage region, the pixel array readout method includes at least an exposure step or a readout step:

[0085] As an example, the exposure steps in this example include: exposing the photoelectric conversion module 11 when the first gain switch SWT1 is turned on, so as to input the converted charge signal into the first charge storage area (in this embodiment, the first floating diffusion node FD1) and the second charge storage area (in this embodiment, the second floating diffusion node FD2 and the first capacitor MIM1); that is, the overflowed charge can be distributed among the storage nodes corresponding to the first storage area and the storage nodes corresponding to the second storage area. In one embodiment, the overflowed charge signal of the photoelectric conversion module is distributed according to the capacitance value ratio of the storage nodes in each storage area. The capacitance value of the storage nodes in each storage area can be set according to actual needs and process conditions. Of course, it should also be noted that when the corresponding light intensity is weak, the charge signal converted by the photoelectric conversion module can also be directly stored in the photodiode; in this embodiment, the beginning of exposing the photoelectric conversion module 11 means turning on and then turning off the transmission tube TX so that the light signal is converted in the photodiode PD.

[0086] In this embodiment, the photoelectric conversion module is set to be partially turned on. When the transmission tube TX is turned on after being turned off, the gate voltage of the transmission tube TX is set to change from low voltage to positive voltage, so that the transmission tube TX is turned on at the subthreshold, ensuring that the channel of the transmission tube TX can leak sufficiently so that photons in the photoelectric conversion module 11 overflow and at least transfer to the first floating diffusion point FD1.

[0087] As an example, setting the photoelectric conversion module 11 to partial conduction includes: before resetting the floating memory module 12 to turn off the corresponding reset transistor RST, lowering the transmission transistor TX of the photoelectric conversion module 11 from a first level to a second level to turn off the transmission transistor TX; and after resetting the floating memory module to turn off the corresponding reset transistor RST, raising the transmission transistor TX from the second level (fully off state) to a third level (such as a subthreshold state) lower than the first level. Setting the turn-off of the transmission transistor TX to the second level before the reset transistor RST is turned off can eliminate the noise caused by the turn-off of the transmission transistor TX based on the reset state of the reset transistor RST; furthermore, after the reset transistor RST is turned off, the transmission transistor TX is further raised from the second level to the third level to cancel out the noise caused by the complete turn-off of the transmission transistor TX before reading begins.

[0088] As an example, the readout steps of this example include: reading the first image signal Overflow_SIG and the first reset signal Overflow_RST of the first charge storage region and the second charge storage region, and calculating the actual signal of the first charge storage region and the second charge storage region based on the difference between the first image signal Overflow_SIG and the first reset signal Overflow_RST; and reading the second image signal CDS_SIG (the charge signal is transferred to the first charge storage region by the photodiode after the transmission tube is turned on) and the second reset signal CDS_RST of the first charge storage region, and calculating the actual signal of the first charge storage region based on the difference between the second image signal CDS_SIG and the second reset signal CDS_RST.

[0089] The following is combined Figure 2 The pixel array reading method provided in this embodiment includes:

[0090] Reset Exposure Step: Turn on the transmission transistor TX (at time t11 in this embodiment) and then turn it off (at time t12 in this embodiment) to allow the photodiode PD to start exposure accumulation. The reset is performed with the first gain switch transistor SWT1 on, so that the first charge storage area, the second charge storage area and the photoelectric conversion module are reset simultaneously (in this embodiment, the reset transistor RST is turned on at time t13 to achieve the reset).

[0091] It should be noted that the reset exposure step also includes a charge overflow step: the transfer transistor TX is partially turned on (maintaining a subthreshold level) to allow the charge signal to overflow through the transfer transistor TX for subsequent signal reading. Before reading the signal, the partially turned-on transfer transistor TX is completely turned off. During this process, the overflowed charge signal can be simultaneously distributed at the corresponding nodes of the first and second memory areas through transistor control.

[0092] The steps for reading out the overflow charge image signal and reset signal are as follows: After resetting the first charge storage area and the second charge storage area, the first gain switch SWT1 is kept on and the control transmission tube TX is completely turned off when reading begins. The control read switch signal is valid (at time t15 in this embodiment) to read the first image signal Overflow_SIG of the first charge storage area and the second charge storage area. Then, the first charge storage area and the second charge storage area are reset (from time t17 to time t18) to read the first reset signal Overflow_RST of the first charge storage area and the second charge storage area.

[0093] The image signal and reset signal readout steps under related dual sampling are as follows: After the readout switch signal is enabled and the first gain switch SWT1 is turned off (at time t19 in this embodiment), the reset signal of the first charge storage area is acquired as the second reset signal CDS_RST. The transmission transistor TX is turned on (from time t110 to t111) to transfer the exposed charge signal to the first charge storage area and quantize the image signal from the first charge storage area as the second image signal CDS_SIG. In the above readout method, the charge is read out in batches, which avoids wasting the photodiode's capacity compared to a complete transfer method.

[0094] The following is combined Figures 2-7 Analysis of the working mechanism of the pixel array readout method in small signal mode in this embodiment:

[0095] like Figure 3 As shown, the first gain switch SWT1 is turned on, which in small signal mode turns on the transmission transistor TX section. Figure 2 During the time intervals t14 to t16, due to the small amount of charge, the charge signal is not transferred to the floating storage module 12 (in this embodiment, the first floating diffusion point FD1 to the first capacitor MIM1), but is stored in the photoelectric conversion module 11.

[0096] like Figure 4 As shown, the control read switch signal is enabled. Figure 2 At time t15, the charge signal was not transferred to the floating storage module 12 (in this embodiment, the first floating diffusion point FD1 to the first capacitor MIM1). Only the charge signal previously stored in the floating storage module 12 was read (if a reset operation has been performed before, the charge signal of the floating storage module 12 in this embodiment is zero). That is, the first image signal Overflow_SIG stored in the first charge storage area and the second charge storage area was read out.

[0097] like Figure 5 As shown, the reset signal is enabled. Figure 2 During the period from t17 to t18, the first reset signal Overflow_RST stored in the first charge storage region and the second charge storage region is read out.

[0098] like Figure 6 As shown, the first gain switch SWT1 is off. Figure 2 At time t19, the space of the floating storage module 12 is divided into two parts. In this embodiment, only the second reset signal CDS_RST stored in the first charge storage area (first floating diffusion point FD1) is read.

[0099] like Figure 7 As shown, the transmission tube TX is on ( Figure 2At time t110, the charge signal in the photoelectric conversion module 11 is transferred to the first charge storage area (first floating diffusion point FD1) and read out.

[0100] The following is combined Figures 8-13 Analysis of the working mechanism of the pixel array readout method in this embodiment under large signal mode:

[0101] like Figure 8 As shown, the first gain switch SWT1 is turned on, which in large signal mode turns on the transmission transistor TX section. Figure 2 During the time intervals t14 to t16, the charge amount is relatively large. At this time, the charge signal will overflow and be transferred to the floating storage module 12 (in this embodiment, the first floating diffusion point FD1 is transferred to the first capacitor MIM1, and charge is distributed at the nodes corresponding to each storage area). The charge signal is partially stored in the photodiode PD and partially stored in the floating storage module 12 at this time.

[0102] like Figure 9 As shown, the control read switch signal is enabled. Figure 2 At time t15, the transmission tube TX is completely turned off to ensure that the charge in the two parts will not migrate to the floating storage module 12 again, and the charge signal in the first charge storage area and the second charge storage area is read as the first image signal Overflow_SIG.

[0103] like Figure 10 and Figure 11 As shown, disconnect after the reset signal is valid. Figure 2 At times t17 and t18, the signals in the first charge storage area and the second charge storage area are reset, and the signals in the first charge storage area and the second charge storage area are read as the first reset signal Overflow_RST.

[0104] like Figure 12 As shown, the first gain switch SWT1 is disconnected. Figure 2 At time t19, the space of the floating storage module 12 is divided into two parts. In this embodiment, only the second reset signal CDS_RST stored in the first charge storage area (first floating diffusion point FD1) is read.

[0105] like Figure 13 and Figure 14 As shown, after the transmission tube TX is turned on and then turned off, the charge is transferred to the first charge storage area, and only the second image signal CDS_SIG stored in the first charge storage area (first floating diffusion point FD1) is read.

[0106] Through the above steps, the accuracy of the acquired signal can be effectively guaranteed, ensuring that the pixel array reading method of this embodiment can be applied to both small signal and large signal modes. That is, the final signal in this application has two situations: one is that there is charge overflow in the photodiode PD, and the other is that there is no charge overflow in the photodiode PD, corresponding to the large signal and small signal in the above description. Subsequently, the digital algorithm module can be used to judge and fuse the two signals to achieve the splicing of the two signals and improve the overall dynamic range.

[0107] Example 2

[0108] To further improve the dynamic range of pixel units, this embodiment provides a pixel array readout method based on, for example... Figure 15 The pixel array of several pixel units 2 shown is read. The pixel unit provided in this embodiment differs from the pixel unit provided in embodiment one in that the floating storage module 21 is different. The floating storage module in this embodiment also includes a third charge storage area and a second gain switch SWT2.

[0109] Specifically, such as Figure 15 The floating storage module 21 shown also includes a third charge storage area and a second gain switch SWT2 disposed between the second charge storage area and the third charge storage area; the control terminal of the second gain switch SWT2 is connected to a third switch control signal, and the second gain switch is turned on or off based on the third switch control signal; the third charge storage area receives the charge signal overflowed from the photoelectric conversion module when the second gain switch SWT2 is turned on.

[0110] As an example, such as Figure 15 As shown, the third charge storage region includes a second capacitor MIM2; the first plate of the second capacitor MIM2 is grounded, and the second plate is connected to the second charge storage region via the second gain switch SWT2. In this example, the second plate is connected to the second floating diffusion node FD2 via the second gain switch SWT2.

[0111] In this example, when the first gain switch SWT1 is turned on, the charge signal overflowing from the photoelectric conversion module 11 flows to the first floating diffusion node FD1, the second floating diffusion node FD2, and the first capacitor MIM1 for storage; and when both the first gain switch SWT1 and the second gain switch SWT2 are turned on, the charge signal overflowing from the photoelectric conversion module 11 flows to the first floating diffusion node FD1, the second floating diffusion node FD2, the first capacitor MIM1, and the second capacitor MIM2 for storage. At this time, the overflowing charge can be distributed among the storage nodes corresponding to the first storage area, the second storage area, and the third storage area. In one embodiment, the charge signal overflowing from the photoelectric conversion module is distributed according to the capacitance value ratio of the storage nodes in each storage area. The capacitance value of the storage nodes in each storage area can be set according to actual needs and process conditions. It should also be noted that when the corresponding light intensity is weak, the charge signal generated by the photoelectric conversion module can be directly stored in the photodiode. Adding a charge storage area compared to the pixel unit in Embodiment 1 can effectively improve the dynamic range.

[0112] As an example, the pixel unit 2 in this embodiment also includes a reset transistor, the control terminal of which is connected to a reset switch signal.

[0113] In the first example, such as Figure 15 As shown, the first end of the reset transistor RST in pixel unit 2 is connected to the power supply voltage VDD, and the second end is connected to the connection node between the second charge storage area and the third charge storage area (in this embodiment, the second floating diffusion point FD2). The control reset switch signal introduces the power supply voltage VDD into the second charge storage area to reset the corresponding storage area, and resets the third charge storage area when the second gain switch SWT2 is turned on.

[0114] In further examples, such as Figure 16 As shown, the pixel unit also includes an additional reset transistor RST_C. The control terminal of the additional reset transistor RST_C receives an additional reset signal. The first terminal is connected to the power supply voltage VDD, and the second terminal is connected to the third charge storage area. When the third charge storage area includes the second capacitor MIM2, the second terminal is connected to one plate of the second capacitor MIM2. At this time, the other plate of the second capacitor MIM2 can be grounded. The above-mentioned additional reset transistor RST_C is beneficial to realize the fast reset of the node.

[0115] In the second example, such as Figure 17As shown, the first end of the reset transistor RST in the pixel unit 2 is connected to the power supply voltage VDD, and the second end is connected to the third charge storage area. In this embodiment, the second end is connected to the node between the second gain switch transistor SWT2 and the second capacitor MIM2. The reset switch signal is controlled to introduce the power supply voltage VDD into the third charge storage area to reset the corresponding storage area. When the second gain switch transistor SWT2 is turned on, the second charge storage area is reset.

[0116] It should be noted that the photoelectric conversion module 11 and the reading module 13 in this embodiment are basically the same as those in Embodiment 1, and will not be described in detail here.

[0117] The pixel array reading method of this embodiment is based on several pixel units 2 provided in this embodiment, and the pixel array reading method of this embodiment is basically the same as that of embodiment one. The difference is that the pixel array reading method of this embodiment needs to read the signal in the floating storage module 21 that includes the third charge storage area.

[0118] Specifically, the exposure step in this embodiment includes: exposing the photoelectric conversion module 11 when both the first gain switch SWT1 and the second gain switch SWT2 are turned on, so as to input the converted charge signal into the first charge storage area, the second charge storage area and the third charge storage area; during this process, through the control of the transistor, the overflow charge signal can be simultaneously distributed at the nodes corresponding to the first storage area and the second storage area.

[0119] Specifically, the readout steps in this example include: after resetting the exposure, keeping the first and second gain switches on, and continuously reading the third image signal nonCDS_SIG and the third reset signal nonCDS_RST of the first charge storage region, the second charge storage region, and the third charge storage region; calculating the actual signals of the first charge storage region, the second charge storage region, and the third charge storage region by subtracting the third image signal nonCDS_SIG and the third reset signal nonCDS_RST; reading the fourth reset signal CDS_LCG_RST and the fourth image signal CDS_LCG_SIG of the first and second charge storage regions, and calculating the actual signals of the first and second charge storage regions by subtracting the fourth image signal CDS_LCG_SIG and the fourth reset signal CDS_LCG_RST; and reading the fifth reset signal CDS_HCG_RST and the fifth image signal CDS_HCG_SIG of the first charge storage region, and calculating the actual signal of the first charge storage region by subtracting the fifth image signal CDS_HCG_SIG and the fifth reset signal CDS_HCG_RST. Similarly, the charge storage area corresponding to the read charge is controlled by controlling the first gain switch SWT1 and the second gain switch SWT2.

[0120] Combination Figure 18 The pixel array reading provided in this embodiment is described below. The exposure steps (from t21 to t26) are basically the same as in Embodiment 1, wherein the first gain switch SWT1 and the second gain switch SWT2 are kept on during the exposure process. The main difference between this embodiment and Embodiment 1 is that at the beginning of the readout step, the second gain switch SWT2 and the first gain switch SWT1 are kept on, and the third image signal nonCDS_SIG and the third reset signal nonCDS_RST are sampled by controlling the reset switch RST to be on and off (corresponding to t27 and t28, respectively). Then, the second gain switch SWT2 (at t29) and the first gain switch SWT1 (at t210) are turned off in sequence, and the fourth reset signal CDS_LCG_RST (between t29 and t210) and the fifth reset signal CDS_HCG_RST (between t210 and t211) are read out in sequence. Turn on the transmission transistor TX (t211 to t212) to read the fifth image signal CDS_HCG_SIG; turn on the first gain switch SWT1 (t213) and then turn on the transmission transistor TX again (t214 to t215) to read the fourth image signal CDS_LCG_SIG. Figure 17The settings can still be applied to large and small signal scenarios corresponding to pixel arrays, while ensuring the effectiveness and accuracy of the reading.

[0121] In this embodiment, the pixel array reading method further includes applications such as Figure 19 The reset and hold steps for the pixel unit shown are as follows: During the quantization reading of the fourth reset signal CDS_LCG_RST, the fifth reset signal CDS_HCG_RST, the fifth image signal CDS_HCG_SIG, and the fourth image signal CDS_LCG_SIG, the reset transistor RST remains on, as shown. Figure 19 The reset state is maintained continuously starting from time t216'. In this embodiment, the reset transistor RST is turned on and kept conducting after the third reset signal nonCDS_RST is read out, and the second gain switch SWT2 is turned off after the reset transistor RST is turned on. At this time, the first gain switch SWT1 is in the conducting state. The above design can, on the one hand, improve the influence of charge movement on the potential of the corresponding storage node during the turn-off process of the reset transistor RST based on the operating voltage VDD. On the other hand, it can also improve the influence of capacitive coupling caused by voltage changes during the operation of the reset transistor RST on the potential of the corresponding storage node. For example, the coupling capacitance generated by the wiring of the reset transistor RST and the second capacitor MIM2 during the voltage change of the reset transistor RST. Furthermore, it can help improve the potential of the first floating diffusion node FD1, thereby facilitating the charge transfer in the photoelectric conversion module.

[0122] In summary, this invention provides a pixel array reading method and a pixel array, implemented based on a plurality of pixel units arranged in an array; wherein each pixel unit includes at least a photoelectric conversion module, a floating storage module, and a reading module; the pixel array reading method includes: resetting the floating storage module and exposing the photoelectric conversion module to output a charge signal to the floating storage module; first reading the image signal of the floating storage module, then resetting the floating storage module and reading the reset signal of the floating storage module; obtaining the real signal of the floating storage module based on the image signal and the reset signal, thereby reducing the noise introduced when the photoelectric conversion module outputs a charge signal to the floating storage module. This invention effectively avoids signal noise introduced by operating the switching transistor by first quantizing and reading the reset signal and image signal of the switching transistor connected to the photodiode. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0123] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for reading a pixel array, wherein the pixel array comprises a plurality of pixel units arranged in an array; wherein, Each pixel unit includes at least a photoelectric conversion module, a floating storage module, and a readout module; the photoelectric conversion module receives an optical signal and converts it into a charge signal; the floating storage module receives and stores the charge signal; the readout module is used to read out the charge signal stored in the floating storage module; characterized in that the pixel array readout method includes: The floating storage module is reset and the photoelectric conversion module is exposed, keeping the floating storage module on to output the charge signal to the floating storage module or store the charge signal in the photoelectric conversion module; the image signal of the floating storage module is read out first, then the floating storage module is reset and the reset signal of the floating storage module is read out, and the real signal of the floating storage module is obtained based on the image signal and the reset signal; the noise introduced when the photoelectric conversion module outputs the charge signal to the floating storage module is reduced based on the exposure readout; When the floating storage module includes a first charge storage area, a second charge storage area, and a first gain switch is disposed between the first charge storage area and the second charge storage area; the first charge storage area is used to receive and store the charge signal overflowing from the photoelectric conversion module; and the second charge storage area receives the charge signal overflowing from the photoelectric conversion module when the first gain switch is turned on, the pixel array readout method includes an exposure step and / or a readout step, wherein: The exposure steps include: When the first gain switch is turned on, the photoelectric conversion module is exposed so as to input the converted charge signal into the first charge storage area and the second charge storage area or to store the converted charge signal in the photoelectric conversion module; The readout step includes: Keeping the first gain switch on and reading the first image signal and the first reset signal of the first and second charge storage regions, the actual signals of the first and second charge storage regions are calculated based on the difference between the first image signal and the first reset signal; and The first gain switch is turned off and the second image signal and the second reset signal of the first charge storage area are read. The real signal of the first charge storage area is obtained by calculating the difference between the second image signal and the second reset signal. The charge signal generated by the photoelectric conversion module is stored in the photoelectric conversion module, and the charge overflowing from the photoelectric conversion module is distributed at least in the storage node corresponding to the first charge storage area and the storage node corresponding to the second charge storage area.

2. The pixel array reading method according to claim 1, characterized in that: The floating storage module includes a first charge storage area, a second charge storage area, and a third charge storage area; a first gain switch is disposed between the first charge storage area and the second charge storage area; and a second gain switch is disposed between the second charge storage area and the third charge storage area. The first charge storage area is used to receive and store the charge signal overflowing from the photoelectric conversion module; the second charge storage area receives the charge signal overflowing from the photoelectric conversion module when the first gain switch is turned on. When the third charge storage region receives the charge signal overflowing from the photoelectric conversion module under the conduction of the second gain switch, the pixel array readout method includes an exposure step and / or a readout step, wherein: The exposure steps include: The photoelectric conversion module is exposed when both the first gain switch and the second gain switch are turned on, so as to input the converted charge signal into the first charge storage area, the second charge storage area and the third charge storage area or store the converted charge signal in the photoelectric conversion module. The readout step includes: Keeping the first gain switch and the second gain switch on, and reading the third image signal and the third reset signal of the first charge storage area, the second charge storage area, and the third charge storage area, respectively; calculating the difference between the third image signal and the third reset signal to obtain the actual signals of the first charge storage area, the second charge storage area, and the third charge storage area; and... The second gain switch is turned off, and the fourth image signal and the fourth reset signal of the first and second charge storage regions are read. The actual signals of the first and second charge storage regions are calculated by subtracting the fourth image signal from the fourth reset signal. The fifth image signal and the fifth reset signal of the first charge storage area are read, and the real signal of the first charge storage area is obtained by calculating the difference between the fifth image signal and the fifth reset signal.

3. The pixel array reading method according to claim 2, characterized in that: The readout order of the fourth image signal, the fourth reset signal, the fifth image signal, and the fifth reset signal includes: The fourth reset signal is read based on the conduction of the first gain switch to read the first charge storage area and the second charge storage area; The first gain switch is used to turn off the fifth reset signal for reading the first charge storage area and the fifth image signal for the first charge storage area. The fourth image signal is read based on the first gain switch being turned on and the first charge storage region and the second charge storage region.

4. The pixel array reading method according to claim 3, characterized in that: The pixel unit further includes a reset transistor for resetting at least one of the first charge storage region, the second charge storage region, and the third charge storage region; wherein the reset transistor is continuously turned on during the reading of the fourth reset signal, the fourth image signal, the fifth reset signal, and the fifth image signal.

5. The pixel array reading method according to any one of claims 1 to 4, characterized in that: The pixel array reading method further includes setting the photoelectric conversion module to partial conduction after resetting the floating storage module and exposing the photoelectric conversion module, so as to output the charge signal to the floating storage module.

6. The pixel array reading method according to claim 5, characterized in that: Setting the photoelectric conversion module to a partially conducting mode includes: before resetting the floating storage module to turn off the corresponding reset transistor, lowering the transmission transistor of the photoelectric conversion module from a first level to a second level to turn off the transmission transistor, and after resetting the floating storage module to turn off the corresponding reset transistor, raising the transmission transistor from the second level to a third level lower than the first level.

7. An image sensor, comprising a pixel array, said pixel array being used to implement the pixel array readout method as described in any one of claims 1-6, characterized in that: The pixel array comprises a plurality of pixel units arranged in an array; Each pixel unit includes at least a photoelectric conversion module, a floating storage module, and a readout module; the photoelectric conversion module receives light signals and converts them into charge signals; the floating storage module receives and stores the charge signals; and the readout module is used to read out the signals stored in the floating storage module.

8. The image sensor according to claim 7, characterized in that: The photoelectric conversion module includes a photodiode and a transmission transistor, wherein: The control terminal of the transmission tube is connected to the first switch control signal, and the photodiode is connected to the floating storage module via the transmission tube to receive the optical signal and transfer the converted charge signal to the floating storage module. Or, the reading module includes an output tube and / or a selection tube, wherein: The first end of the output transistor is connected to the floating memory module, the second end is connected to the power supply voltage, and the third end is connected to the first end of the selection transistor, so as to amplify the output signal of the floating memory module. The control terminal of the selection tube is connected to the read switch signal, and the second terminal serves as the output terminal of the read module. The selection tube is turned on based on the read switch signal to output the output signal of the output tube. And / or, the floating storage module includes a first charge storage region, a second charge storage region, and a first gain switch transistor disposed between the first charge storage region and the second charge storage region, wherein: The first charge storage area is used to receive and store the charge signal output by the photoelectric conversion module. The control terminal of the first gain switch is connected to a second switch control signal, which causes the first gain switch to be turned on or off. The second charge storage region receives the charge signal output by the first charge storage region when the first gain switch is turned on.

9. The image sensor according to claim 8, characterized in that: The first charge storage region is configured as a first floating diffusion node; the second charge storage region includes a second floating diffusion node and a first capacitor; the first plate of the first capacitor is grounded, and the second plate is connected to the second floating diffusion node; the second floating diffusion node is connected to the first floating diffusion node via the first gain switch.

10. The image sensor according to claim 8, characterized in that: The floating storage module further includes a third charge storage region and a second gain switch disposed between the second charge storage region and the third charge storage region; The control terminal of the second gain switch is connected to a third switch control signal, and the second gain switch is turned on or off based on the third switch control signal. The third charge storage region receives the charge signal output by the second charge storage region when the second gain switch is turned on.

11. The image sensor according to claim 10, characterized in that: The third charge storage region includes a second capacitor, with the first plate grounded and the second plate connected to the second charge storage region via the second gain switch.

12. The image sensor according to any one of claims 7 to 11, characterized in that: Each pixel unit also includes a reset transistor whose control terminal is connected to a reset switch signal, whose first terminal is connected to the power supply voltage, and whose second terminal is connected to the floating memory module.

13. The image sensor according to claim 12, characterized in that: When the floating storage module includes a first charge storage area, a second charge storage area, and a first gain switch transistor disposed between the first charge storage area and the second charge storage area, the first end of the reset transistor is connected to the power supply voltage, and the second end is connected to the second charge storage area. When the floating storage module includes a first charge storage region, a second charge storage region, a third charge storage region, a first gain switch is disposed between the first charge storage region and the second charge storage region, and a second gain switch is disposed between the second charge storage region and the third charge storage region, The first end of the reset tube is connected to the power supply voltage, and the second end is connected to the third charge storage area or the second end is connected to the connection node between the second charge storage area and the third charge storage area.

14. The image sensor according to claim 13, characterized in that: When the floating storage module includes a first charge storage area, a second charge storage area, a third charge storage area, a first gain switch is disposed between the first charge storage area and the second charge storage area, and a second gain switch is disposed between the second charge storage area and the third charge storage area, the first end of the reset tube is connected to the power supply voltage, and the second end is connected to the connection node between the second charge storage area and the third charge storage area, the pixel unit also includes an additional reset tube; The control terminal of the additional reset tube receives an additional reset signal. The first terminal is connected to the power supply voltage, and the second terminal is connected to the third charge storage area. When the third charge storage area includes a second capacitor, the second terminal is connected to the second capacitor plate.

Images