Pixel unit, image sensor and electronic equipment

Abstract

The utility model provides a pixel unit, an image sensor and an electronic device, the pixel unit comprises a photoelectric conversion part, a first reset part, a charge transmission storage circuit and a signal output circuit, the first reset part is connected with the photoelectric conversion part and the charge transmission storage circuit; one end of the charge transmission and storage circuit is connected with the photoelectric conversion part and the first reset part, the other end of the charge transmission and storage circuit is connected with the floating diffusion region, and the charge transmission and storage circuit is at least configured to orderly transmit and store the collected exposure signals before the photoelectric conversion part completes the first exposure stage or the second exposure stage. The exposure time lengths of the first exposure stage and the second exposure stage are different; and the signal output circuit is connected with the floating diffusion region and is configured to read and output the exposure signals so as to combine the exposure signals to obtain pixel signals. According to the utility model, the photosensitive dynamic range of the image sensor in a global exposure working mode can be effectively improved.

Description

Technical Field

[0001] This utility model belongs to the field of image sensor technology, and in particular relates to a pixel unit, an image sensor and an electronic device. Background Technology

[0002] Image sensors have been widely used in digital cameras, mobile phones, medical devices, automobiles, drones, and machine recognition. In particular, the rapid development of complementary metal oxide semiconductor (CMOS) image sensor technology has led to higher requirements for the output image quality of image sensors.

[0003] Image sensors are categorized into two types based on their exposure methods: rolling exposure image sensors and global exposure image sensors. Currently, the consumer electronics and IoT sectors almost exclusively use rolling exposure image sensors. Rolling exposure image sensors are technically mature, easy to implement, and produce lower image noise, making them suitable for capturing still or slow-moving images. However, they may exhibit image blurring and distortion issues when capturing relatively fast-moving images. In the automotive electronics and traffic monitoring sectors, global exposure image sensors are preferred. Global exposure image sensors are better suited for capturing moving images and do not suffer from image blurring or distortion issues when capturing relatively fast-moving images.

[0004] However, global exposure image sensors generally suffer from a low dynamic range. Utility Model Content

[0005] In order to overcome the above-mentioned defects in the prior art, the present invention provides a pixel unit, an image sensor and an electronic device to solve the problem that the image sensor with global exposure mode in the prior art cannot meet the dynamic range of light sensitivity.

[0006] In a first aspect of this utility model, a pixel unit is provided, comprising: a photoelectric conversion unit, a first reset unit, a charge transport and storage circuit, and a signal output circuit. The first reset unit is connected to the photoelectric conversion unit and the charge transport and storage circuit. One end of the charge transport and storage circuit is connected to the photoelectric conversion unit and the first reset unit, and the other end is connected to a floating diffusion region. The charge transport and storage circuit is configured to transmit and store the collected exposure signal in an orderly manner before the photoelectric conversion unit completes a first exposure stage or a second exposure stage, wherein the exposure time lengths of the first exposure stage and the second exposure stage are different. The signal output circuit is connected to the floating diffusion region and is configured to read and output the exposure signal to combine it to obtain a pixel signal.

[0007] In one embodiment, the charge transport and storage circuit includes a charge transport section and a charge storage section. A first end of the charge transport section is connected to a photoelectric conversion section and a first reset section, a second end of the charge transport section is connected to the charge storage section, and a third end of the charge transport section is connected to a floating diffusion region. The charge transport section is configured to transmit exposure signals corresponding one-to-one with the first exposure stage and the second exposure stage in an orderly manner from the photoelectric conversion section to the charge storage section, or to transmit exposure signals in an orderly manner to the floating diffusion region, according to a transmission control signal. The charge storage section is configured to receive exposure signals asynchronously and store exposure signals synchronously.

[0008] In another embodiment, the charge transport section includes a first transport transistor, a second transport transistor, and a third transport transistor; the charge storage section includes a first storage capacitor and a second storage capacitor; and the transmission control signal includes a first transmission control signal, a second transmission control signal, and a third transmission control signal. The first transmission control signal controls the operating state of the first transport transistor, the second transmission control signal controls the operating state of the second transport transistor, and the third transmission control signal controls the operating state of the third transport transistor. A first terminal of the first transport transistor is connected to a first reset section and a photoelectric conversion section; a second terminal of the first transport transistor is connected to the first terminal of the second transport transistor and the first terminal of the second storage capacitor; and a third terminal of the first transport transistor is configured to receive the first transmission control signal. A second terminal of the second transport transistor is connected to the first terminal of the third transport transistor and the first terminal of the first storage capacitor; and a third terminal of the second transport transistor is configured to receive the second transmission control signal. A second terminal of the third transport transistor is connected to a floating diffusion region; and a third terminal of the third transport transistor is configured to receive the third transmission control signal. Both the second terminals of the first and second storage capacitors are grounded.

[0009] In another embodiment, during the first exposure stage, when the first and second transmission transistors are on and the third transmission transistor is off, the first storage capacitor is configured to receive the first exposure signal acquired during the first exposure stage from the photoelectric conversion unit, and to store the first exposure signal according to the global control signal after the photoelectric conversion unit completes the second exposure; during the first exposure stage, when the first transmission transistor is on and the second and third transmission transistors are off, the second storage capacitor is configured to receive the second exposure signal acquired during the second exposure stage from the photoelectric conversion unit; and to store the second exposure signal while the first storage capacitor stores the first exposure signal.

[0010] In another embodiment, the first reset unit is a global reset transistor, the photoelectric conversion unit is a photodiode, the first terminal of the global reset transistor is connected to the power supply module, the second terminal of the global reset transistor is connected to the negative terminal of the photodiode, and the third terminal of the global reset transistor is configured to receive a global control signal. The global control signal is used to control the global reset transistor to turn on or off. When the global reset transistor is on, the photodiode is reset, and the operation of the charge transfer storage circuit and the signal output circuit is synchronously controlled.

[0011] In another embodiment, when the global reset transistor is off, the photodiode is configured to receive an optical signal and convert the optical signal into a first exposure signal or a second exposure signal, depending on the duration for which the global reset transistor is off.

[0012] In another embodiment, the charge transport storage circuit includes a first transport transistor, a second transport transistor, a third transport transistor, a first storage capacitor, and a second storage capacitor. The circuit includes a configuration where, after the photodiode completes its second exposure stage, a global reset transistor is turned on, and the first, second, and third transport transistors are all turned off. In this configuration, the first storage capacitor is configured to store the received first exposure signal, and the second storage capacitor is configured to synchronously store the received second exposure signal.

[0013] In another embodiment, the signal output circuit includes a reset transistor, a first terminal of which is connected to a power supply module, a second terminal of which is connected to a floating diffusion region, and a third terminal of which is configured to receive a reset control signal, wherein the floating diffusion region is reset when the reset transistor is turned on.

[0014] In another embodiment, the signal output circuit further includes a source follower transistor and a pixel selection transistor. A first terminal of the source follower transistor is connected to a power supply module, a second terminal of the source follower transistor is connected to the first terminal of the pixel selection transistor, and a third terminal of the source follower transistor is connected to a floating diffusion region. The third terminal of the source follower transistor is used to read the exposure signal from the floating diffusion region. The second terminal of the pixel selection transistor is used to output the exposure signal. The third terminal of the pixel selection transistor is used to receive a selection control signal, which controls the operating state of the pixel selection transistor. When the pixel selection transistor is on and the third transmission transistor is on, the floating diffusion region is configured to read the first exposure signal acquired in the first exposure stage from the first storage capacitor. When the pixel selection transistor is on and both the third and second transmission transistors are on, the floating diffusion region is configured to read the second exposure signal in the second exposure stage from the second storage capacitor.

[0015] In another embodiment, the exposure time of the first exposure stage is longer than that of the second exposure stage. The first exposure stage is used to acquire low-light image information, and the second exposure stage is used to acquire strong-light image information.

[0016] In a second aspect of the present invention, an image sensor is provided, comprising: a pixel array in which the pixel units described in the first aspect are arranged in an array.

[0017] In a fourth aspect of the present invention, an electronic device is provided, including an image sensor as described in the third aspect.

[0018] This invention provides a pixel unit, image sensor, and electronic device. The pixel unit includes a photoelectric conversion unit, a first reset unit, a charge transfer and storage circuit, and a signal output circuit. The first reset unit is connected to the photoelectric conversion unit and the charge transfer and storage circuit. One end of the charge transfer and storage circuit is connected to the photoelectric conversion unit and the first reset unit, and the other end is connected to a floating diffusion region. The charge transfer and storage circuit is configured to transmit and store the acquired exposure signal in an orderly manner before the photoelectric conversion unit completes the first exposure stage or the second exposure stage. The exposure time lengths of the first exposure stage and the second exposure stage are different. The signal output circuit is connected to the floating diffusion region to output the exposure signal. The pixel unit provided by this invention can improve the dynamic range of light sensitivity by combining the image information from two exposures, effectively improving the dynamic range of light sensitivity of image sensors operating in global exposure mode compared to existing technologies. Attached Figure Description

[0019] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0020] Figure 1 This is a circuit structure diagram of a pixel unit according to an embodiment of the present invention;

[0021] Figure 2 This is a circuit structure diagram of a pixel unit according to another embodiment of the present invention;

[0022] Figure 3 This is a circuit structure diagram of a pixel unit according to another embodiment of the present invention;

[0023] Figure 4 This is a timing diagram of a pixel unit provided according to an embodiment of the present invention.

[0024] The same or similar reference numerals in the accompanying drawings represent the same or similar parts. Detailed Implementation

[0025] To better understand and explain this utility model, a further detailed description will be provided below with reference to the accompanying drawings. This utility model is not limited to these specific embodiments. Rather, any modifications or equivalent substitutions made to this utility model should be covered within the scope of the claims.

[0026] It should be noted that numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be implemented without these specific details. In the various detailed embodiments given below, principles, structures, and components well-known in the art are not described in detail in order to highlight the main points of this invention.

[0027] Image sensors are categorized into two types based on their exposure methods: rolling exposure image sensors and global exposure image sensors. Currently, the consumer electronics and IoT sectors almost exclusively use rolling exposure image sensors. Rolling exposure image sensors are technically mature, easy to implement, and produce lower image noise, making them suitable for capturing still or slow-moving images. However, they may exhibit image blurring and distortion issues when capturing relatively fast-moving images. In the automotive electronics and traffic monitoring sectors, global exposure image sensors are preferred. Global exposure image sensors are better suited for capturing moving images and do not suffer from image blurring or distortion issues when capturing relatively fast-moving images.

[0028] Image sensors operating under global exposure can be classified into two types based on pixel operation: charge signal storage type and voltage signal storage type. Voltage signal storage type image sensors have more components in each pixel, which reduces the area of ​​the photodiode and lowers the photosensitivity. Charge signal storage type is relatively more difficult to manufacture pixels, but its advantage of having fewer components makes it the preferred choice for image sensors operating under global exposure.

[0029] Image sensors operating on a global exposure basis generally have a low dynamic range, such as 60dB or 70dB, which is insufficient to meet the performance requirements of the current market. Therefore, there is an urgent need to find methods to improve the dynamic range of image sensors operating on a global exposure basis.

[0030] Please refer to Figure 1 , Figure 1 This is a circuit structure diagram of a pixel unit according to an embodiment of the present invention. As shown in the figure, the pixel unit includes: a photoelectric conversion unit 101, a first reset unit 102, a charge transfer and storage circuit 103, and a signal output circuit 104.

[0031] The photoelectric conversion unit 101 can be a photodiode. The photodiode receives light signals during the exposure time to generate photoelectric charge.

[0032] The first reset unit 102 is connected to the photoelectric conversion unit 101 and the charge transfer and storage circuit 103. The first reset unit 102 is used to control the photoelectric conversion unit 101 to complete the conversion of photoelectric signals in the first exposure stage and the second exposure stage according to the global control signal, and to control the working state of the charge transfer and storage circuit 103 and the signal output circuit 104 according to the global control signal.

[0033] The charge transfer and storage circuit 103 is connected at one end to the photoelectric conversion unit 101 and the first reset unit 102, and at the other end to the floating diffusion region FD. The charge transfer and storage circuit 103 is used to transmit and store the exposure signals collected by the photoelectric conversion unit 101 in the first exposure stage and the second exposure stage in an orderly manner according to the received transmission control signal; and to transmit the exposure signals to the floating diffusion region. The exposure time lengths of the first exposure stage and the second exposure cycle are different.

[0034] The exposure time in the first exposure phase is longer than the exposure time in the second exposure cycle.

[0035] First exposure: The image sensor takes the first exposure to the scene. To capture information about the low-light image, the signal charge generated by the exposure is transferred to a set of storage capacitors. These charges are temporarily stored in the storage capacitors, awaiting subsequent readout operations.

[0036] Second exposure: After the first exposure, the image sensor performs a second exposure of the scene to capture information from the stronger light. The signal charge generated during this exposure is transferred to another set of storage capacitors.

[0037] Simultaneous storage: After two exposures, all storage capacitors simultaneously store charge. All signal charge is stored in the storage capacitors, ready for subsequent signal processing and readout.

[0038] This operating mode effectively reduces motion artifacts in images and improves image quality. By performing two exposures and storing the signals in different storage capacitors, it ensures that no artifacts are generated during readout due to charge movement, resulting in a clearer and more accurate image.

[0039] The signal output circuit 104 is connected to the floating diffusion region FD and is used to read the exposure signals stored in the floating diffusion region FD that correspond one-to-one with the first exposure stage and the second exposure stage, and to output the exposure signals for merging to obtain the pixel signal.

[0040] In the global exposure mode, the pixel unit stores the exposure signals acquired from two exposures through a charge transfer storage circuit, and then merges the output exposure signals to obtain the pixel signal, which can effectively improve the dynamic range of the image sensor.

[0041] Further reference Figure 2 , Figure 2 This is a circuit structure diagram of a pixel unit according to another embodiment of the present invention. As shown in the figure, the pixel unit includes: a photoelectric conversion unit 101, a first reset unit 102, a charge transfer and storage circuit 103, and a signal output circuit 104. The charge transfer and storage circuit 103 includes a charge transfer unit 1031 and a charge storage unit 1032. The charge transfer unit 1031 is connected to the photoelectric conversion unit 101 and the first reset unit 102, and the charge storage unit 1032 is connected to the charge transfer unit 1031.

[0042] The charge transfer unit 1031 is used to orderly transfer the exposure signals corresponding one-to-one with the first exposure stage and the second exposure stage from the photoelectric conversion unit 102 to the charge storage unit 1032. The charge storage unit 1032 is used to synchronously store the exposure signals corresponding one-to-one with the first exposure stage and the second exposure stage.

[0043] The signal output circuit 104 includes a second reset unit 1041 and an auxiliary circuit 1042.

[0044] The second reset unit 1041 is connected to the charge transfer storage circuit 103 and the auxiliary circuit 1042. When the second reset unit 1041 is turned on, it resets the floating diffusion region FD. The auxiliary circuit 1042 is connected to the floating diffusion region FD and is used to read the exposure signal from the floating diffusion region in an orderly manner.

[0045] Because the floating diffusion region (FD) is isolated from external circuitry, the influence of external noise can be effectively reduced during readout, improving the signal-to-noise ratio. This isolation also helps reduce crosstalk between pixels, thereby improving image sharpness and quality.

[0046] Further reference Figure 3 , Figure 3 This is a circuit structure diagram of a pixel unit according to another embodiment of the present invention. As shown in the figure, the pixel unit includes: a photoelectric conversion unit 101, a first reset unit 102, a charge transfer and storage circuit 103, and a signal output circuit 104.

[0047] The first reset unit 102 can be a global reset transistor. The first terminal of the global reset transistor is connected to the power module AVDD, the second terminal of the global reset transistor is connected to the photoelectric conversion unit 101, and the third terminal of the global reset transistor is configured to receive the global control signal GRST. The global control signal GRST is used to control the global reset transistor to be turned on or off.

[0048] In a single pixel unit, the conduction state of the global reset transistor is controlled according to the global control signal to control the working state of the photoelectric conversion unit, charge transfer storage circuit and signal output circuit, and to ensure that they can be reset at the same time to maintain the synchronization of the pixel units of the image sensor in the global working mode, effectively reducing interference and noise between devices.

[0049] The charge transport and storage circuit 103 may include a first transport transistor 1031, a second transport transistor 1032, a third transport transistor 1033, a first storage capacitor 1034, and a second storage capacitor 1035. The first transport transistor 1031, the second transport transistor 1032, and the third transport transistor 1033 constitute a charge transport circuit, and the first storage capacitor 1034 and the second storage capacitor 1035 constitute a charge storage circuit.

[0050] The first terminal of the first transmission transistor 1031 is connected to the first reset unit 102 and the photoelectric conversion unit 101. The second terminal of the first transmission transistor 1031 is connected to the first terminal of the second transmission transistor 1032 and the first terminal of the second storage capacitor 1035. The third terminal 1031 of the first transmission transistor is configured to receive a first transmission control signal TXA for controlling the operating state of the first transmission transistor 1031.

[0051] The second terminal of the second transmission transistor 1032 is connected to the first terminal of the third transmission transistor 1033 and the first terminal of the first storage capacitor 1034. The third terminal of the second transmission transistor 1032 is configured to receive a second transmission control signal TXB for controlling the operating state of the second transmission transistor 1032.

[0052] The second terminal of the third transmission transistor 1033 is connected to the floating diffusion region FD, and the third terminal of the third transmission transistor 1033 is configured to receive the third transmission control signal TXC used to control the operating state of the third transmission transistor 1033.

[0053] The second terminal of the first storage capacitor 1034 and the second terminal of the second storage capacitor 1035 are both grounded.

[0054] The signal output circuit 104 may include a reset transistor 10411, a source follower transistor 10421, and a pixel selection transistor 10422. The reset transistor 10411 serves as a second reset unit 1041, and the source follower transistor 10421 and the pixel selection transistor 10422 constitute an auxiliary circuit 1042.

[0055] The first terminal of the reset transistor 10411 is connected to the power supply module, the second terminal of the reset transistor 10411 is connected to the floating diffusion region FD, and the third terminal of the reset transistor 10411 is configured to receive the reset control signal RST. When the reset transistor 10411 is turned on, the floating diffusion region FD is reset.

[0056] The first terminal of the source follower transistor 10421 is connected to the power supply module, the second terminal of the source follower transistor 10421 is connected to the first terminal of the pixel selection transistor 10422, and the third terminal of the source follower transistor 10421 is connected to the floating diffusion region FD. The second terminal of the pixel selection transistor 10422 is used to output the exposure signal, and the third terminal of the pixel selection transistor 10422 is used to receive the selection control signal SEL.

[0057] The third terminal of the source follower transistor 10421 is used to read the exposure signal from the floating diffusion region.

[0058] The third terminal of the pixel selection transistor 10422 is used to receive the selection control signal SEL, which is used to control the pixel selection transistor 10422 to be turned on. When the pixel selection transistor 10422 is turned on and the third transmission transistor 1033 is turned on (the second transmission transistor 1032 and the first transmission transistor 1031 remain off), the first exposure signal acquired in the first exposure stage is read from the first storage capacitor 1034. When the pixel selection transistor 10422 is turned on and the third transmission transistor 1033 and the second transmission transistor 1032 are both turned on (the first transmission transistor 1031 remains off), the second exposure signal in the second exposure stage is read from the second storage capacitor 1035.

[0059] In some embodiments, the transistors described above can all be NMOS transistors. The photoelectric conversion unit 101 can be a photodiode.

[0060] The drain of the global reset transistor is connected to the negative terminal of the photodiode, the source of the global reset transistor is connected to the power module AVDD, and the gate of the global reset transistor receives the GRST signal; the positive terminal of the photodiode is grounded.

[0061] The source of the first transmission transistor 1031 is connected to the negative terminal of the photodiode and the drain of the global reset transistor. The drain of the first transmission transistor 1031 is connected to one end of the second storage capacitor 1035 and the source of the second transmission transistor 1032. The gate of the first transmission transistor 1031 receives the first transmission control signal TXA.

[0062] The source of the second transmission transistor 1032 is connected to the drain of the first transmission transistor 1031 and one end of the second storage capacitor 1035; the drain of the second transmission transistor 1032 is connected to one end of the first storage capacitor 1034 and the source of the third transmission transistor 1033, and the gate of the second transmission transistor 1032 receives the second transmission control signal TXB; the source of the third transmission transistor 1033 is connected to the drain of the second transmission transistor 1032 and one end of the first storage capacitor 1034, the drain of the third transmission transistor 1033 is connected to the floating diffusion region FD, and the gate of the third transmission transistor 1033 receives the third transmission control signal TXC.

[0063] The second storage capacitor 1035 is located between the first transmission transistor 1031 and the second transmission transistor 1032, and the first storage capacitor 1034 is located between the second transmission transistor 1032 and the third transmission transistor 1033.

[0064] The source follower transistor 10421 and the pixel select transistor 10422 are connected. The gate of the source follower transistor 10421 is connected to the floating diffusion region FD. The drain of the source follower transistor 10421 is connected to the power supply module. The source of the source follower transistor 10421 is connected to the drain of the pixel select transistor 10422. The source of the pixel select transistor 10422 serves as the output terminal of the pixel unit. The gate of the pixel select transistor 10422 receives the selection control signal SEL.

[0065] The source of the reset transistor 10411 is connected to the power supply module, the drain of the reset transistor 10411 is connected to the floating diffusion region FD, and the gate of the reset transistor 10411 receives the reset control signal RST. The reset control signal RST is used to control the turn-on or turn-off of the reset transistor 10411. When the reset transistor 10411 is turned on, the floating diffusion region FD is reset.

[0066] Clearing and resetting the floating diffusion region by controlling the conduction status of the reset transistor can effectively improve image quality. Precisely controlling the reset of the photodiode, the timing of synchronous storage of the exposure signal, and the timing of reading the exposure signal by controlling the conduction status of the global reset transistor helps to improve the adaptability of the image sensor.

[0067] The following is combined Figure 4 The timing control method for pixel units is further described. Figure 4 This is a timing diagram of a pixel unit provided according to an embodiment of the present invention.

[0068] like Figure 4 As shown, the global control signal GRST includes a first exposure phase (i.e., a first time period), a reset control phase, and a second exposure phase (i.e., a second time period). The first exposure phase is a first duration for which the global control signal is changed from a high level to a low level. The second exposure phase is a second duration for which the global control signal is changed from a high level to a low level. The reset control phase is a duration for which the global control signal is changed from a low level to a high level, and it is located between the first exposure phase and the second exposure phase.

[0069] During the first exposure stage, the first reset unit 102 is disconnected, the photoelectric conversion unit 101 receives the light signal to generate the first exposure signal, and the charge transfer storage circuit 103 transmits the first exposure signal according to the received transmission control signal during the first exposure stage.

[0070] The reset control phase is set between the first exposure operation phase and the second exposure operation phase. During the reset control phase, the photoelectric conversion unit 101 clears all charges and resets itself.

[0071] During the second exposure stage, the first reset unit 102 is disconnected, the photoelectric conversion unit 101 receives the light signal to generate the second exposure signal, and the charge transfer storage circuit 103 transmits the second exposure signal according to the received transmission control signal during the second exposure stage.

[0072] The embodiments provided in this disclosure transmit two exposure signals to the first storage capacitor 1034 and the second storage capacitor 1035 respectively. Then, the first storage capacitor 1034 and the second storage capacitor 1035 simultaneously store their respective received exposure signals, which can help reduce motion artifacts and improve image quality.

[0073] In one embodiment, the exposure time of the first exposure stage is longer than that of the second exposure stage. The first exposure stage is used to acquire low-light image information, and the second exposure stage is used to acquire strong-light image information.

[0074] By designing the exposure time, sufficient light signal can be obtained in low-light conditions to maintain the brightness and quality of the image.

[0075] The global control signal also includes an exposure signal storage phase (i.e., charge signal storage period) and an exposure signal reading phase (i.e., the third time period). During the exposure signal storage phase, the charge transfer storage circuit 103 synchronously stores the first exposure signal and the second exposure signal.

[0076] During the exposure signal reading phase, the signal output circuit 104 reads the first exposure signal and the second exposure signal in an orderly manner from the floating diffusion region FD according to the received reset control signal RST, selection control signal SEL, and read timing control signal read. The exposure signal reading phase may also include a first reading sub-phase (i.e., the time period corresponding to reading the first exposure signal) and a second reading sub-phase (i.e., the time period corresponding to reading the second exposure signal).

[0077] During the first or second reading sub-stage, the signal output circuit 104 reads the reset signal from the floating diffusion region according to the reading timing control signal read, and then reads the first exposure signal or the second exposure signal from the floating diffusion region.

[0078] By first reading the reset signal of the floating diffusion region and then reading the sampling exposure signal, it is helpful to ensure the accuracy, reliability and efficiency of signal reading, thereby improving the overall performance of the image sensor and the image quality.

[0079] After the second time period, the pixel selection transistor 10422 receives the selection control signal SEL, transitions from a low potential to a high potential, and maintains a high potential throughout the fourth time period, the length of which is the same as the length of the third time period. During the first read sub-cycle, the reset transistor 10411 receives the reset control signal, resetting the floating diffusion region. When the read timing control signal read transitions from a low potential to a high potential for the first time, the signal output circuit reads the reset signal from the floating diffusion region. Then, when the third transmission control signal TXC transitions from a low potential to a high potential, the first exposure signal stored in the charge transfer storage circuit 103 is transmitted to the floating diffusion region FD. When the read timing control signal read transitions from a low potential to a high potential for the second time, the signal output circuit 104 reads the first exposure signal.

[0080] During the second read sub-cycle, the reset transistor 10411 receives the reset control signal again, resetting the floating diffusion region. When the read timing control signal `read` transitions from low to high for the third time, the signal output circuit reads the reset signal from the floating diffusion region again. Then, the third transmission control signal `TXC` and the second transmission control signal `TXB` simultaneously transition from low to high, transmitting the second exposure signal stored in the charge transfer storage circuit 103 to the floating diffusion region `FD`. When the read timing control signal `read` transitions from low to high for the fourth time, the signal output circuit 104 reads the second exposure signal.

[0081] Taking the above transistors as examples where all are NMOS transistors, a high level represents a conduction signal and a low level represents a turn-off signal.

[0082] First, when the global control signal GRST is set from a high potential to a low potential, the photodiode performs its first exposure operation. Before the first exposure ends, the second transmission control signal TXB, the third transmission control signal TXC, and the reset control signal RST simultaneously change from a low potential to a high potential, turning on the second transmission transistor 1032 and the third transmission transistor 1033, thus resetting the first storage capacitor 1034 and the second storage capacitor 1035 by applying high-potential pulses to TXB, TXC, and RST.

[0083] Subsequently, the second transmission control signal TXB and the third transmission control signal TXC change from high potential to low potential, and the second transmission transistor 1032 and the third transmission transistor 1033 are turned off. When the second transmission control signal TXB and the first transmission control signal TXA change from low potential to high potential, the second transmission transistor 1032 and the first transmission transistor 1031 are turned on, and the third transmission transistor 1033 is turned off, transferring the charge signal collected by the photodiode to the first storage capacitor 1034, that is, giving TXB and TXA a high potential pulse operation.

[0084] When the global control signal GRST changes from low to high, the photodiode is reset, i.e., a high-level pulse operation is applied to GRST.

[0085] When the global control signal GRST changes from high to low again, the photodiode performs a second exposure operation. Before the second exposure ends, when the first transmission control signal TXA changes from low to high, the first transmission transistor 1031 is turned on, the second transmission control signal TXB and the third transmission control signal TXC are in a low-level continuous phase, and the second transmission transistor 1032 and the third transmission transistor 1033 are turned off, transferring the charge signal collected by the photodiode to the second storage capacitor 1035, that is, giving TXA a high-level pulse operation.

[0086] When the global control signal GRST changes from a low potential to a high potential and remains at a high potential for a certain duration, the first storage capacitor 1034 and the second storage capacitor 1035 synchronously store the received charge signal. This stage is the charge signal storage period, waiting for subsequent operations.

[0087] When the global control signal GRST remains high and the selection control signal SEL changes from low to high, the first exposure signal is read. When the reset control signal RST changes from low to high, the floating diffusion region FD is reset, i.e., a high-level pulse is applied to RST. When the read timing control signal read changes from low to high for the first time, the reset signal of the floating diffusion region is acquired, i.e., a high-level pulse is applied to the read timing control signal read. When the third transmission control signal TXC changes from low to high, charge is transferred from the first storage capacitor 1034 to the floating diffusion region FD, i.e., a high-level pulse is applied to TXC. Then, when the read timing control signal read changes from low to high for the second time, the charge signal is acquired from the floating diffusion region, i.e., a high-level pulse is applied to the read timing control signal read.

[0088] When the reset control signal RST changes from low to high, the floating diffusion region FD is reset a second time, and the operation of reading the second exposure signal is performed, i.e., a high-potential pulse is applied to RST. When the read timing control signal read changes from low to high for the third time, the reset signal of the floating diffusion region is acquired, i.e., a high-potential pulse is applied to the read timing control signal read. When the third transmission control signal TXC and the second transmission control signal TXB change from low to high, charge is transferred from the second storage capacitor 1035 to the floating diffusion region FD, i.e., high-potential pulses are applied to TXC and TXB. Then, when the read timing control signal read changes from low to high for the fourth time, the charge signal is acquired from the floating diffusion region, i.e., a high-potential pulse is applied to the read timing.

[0089] Finally, the first exposure signal and the second exposure signal are combined and merged to obtain the pixel signal.

[0090] This invention acquires image information through two exposures of different durations, and then combines the image information into a high dynamic range image, which effectively improves the dynamic range of the image sensor in the global exposure mode compared to the prior art.

[0091] Accordingly, this utility model also discloses an image sensor. The image sensor consists of a pixel array composed of the pixel units described above arranged in an array.

[0092] Accordingly, this utility model also discloses an electronic device. The electronic device can be applied to any of the following: pulse camera, high-speed camera, audio / video player, navigation device, fixed-position terminal, entertainment unit, smartphone, communication device, device in a motor vehicle, camera, action or wearable camera, detection device, flight equipment, medical device, security device, etc.

[0093] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and not restrictive, and the scope of this invention is defined by the appended claims rather than the foregoing description. All variations within the meaning and scope of equivalents of the claims are inclusive of this invention. No reference numerals in the claims should be construed as limiting the scope of the claims. Furthermore, it is clear that the word "comprising" does not exclude other components, elements, or steps, and the singular does not exclude the plural.

[0094] The above-described embodiments or specific implementations of the present utility model are only some examples of the present utility model and should not be construed as limiting the scope of the present utility model. Equivalent variations made in accordance with the claims of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A pixel unit, characterized in that, The application relates to a pixel circuit, comprising: a photoelectric conversion unit, a first reset unit, a charge transmission and storage circuit and a signal output circuit, the first reset unit is connected with the photoelectric conversion unit and the charge transmission and storage circuit; one end of the charge transmission and storage circuit is connected with the photoelectric conversion unit and the first reset unit, and the other end is connected with a floating diffusion region, the charge transmission and storage circuit is configured to orderly transmit and store collected exposure signals before the photoelectric conversion unit completes a first exposure stage or a second exposure stage, and the first exposure stage and the second exposure stage have different exposure time lengths; the signal output circuit is connected with the floating diffusion region and is configured to read and output the exposure signals to obtain a pixel signal.

2. The pixel cell of claim 1, wherein, The charge transmission and storage circuit comprises a charge transmission unit and a charge storage unit, a first end of the charge transmission unit is connected with the photoelectric conversion unit and the first reset unit, a second end of the charge transmission unit is connected with the charge storage unit, and a third end of the charge transmission unit is connected with the floating diffusion region; the charge transmission unit is configured to orderly transmit the exposure signals corresponding to the first exposure stage and the second exposure stage from the photoelectric conversion unit to the charge storage unit or to the floating diffusion region according to a transmission control signal; the charge storage unit is configured to asynchronously receive the exposure signals and synchronously store the exposure signals.

3. The pixel cell of claim 2, wherein, The charge transmission unit comprises a first transmission transistor, a second transmission transistor and a third transmission transistor, the charge storage unit comprises a first storage capacitor and a second storage capacitor, the transmission control signal comprises a first transmission control signal, a second transmission control signal and a third transmission control signal, the first transmission control signal is used for controlling the working state of the first transmission transistor, the second transmission control signal is used for controlling the working state of the second transmission transistor, and the third transmission control signal is used for controlling the working state of the third transmission transistor; a first end of the first transmission transistor is connected with the first reset unit and the photoelectric conversion unit, a second end of the first transmission transistor is connected with a first end of the second transmission transistor and a first end of the second storage capacitor, and a third end of the first transmission transistor is configured to receive the first transmission control signal; a second end of the second transmission transistor is connected with a first end of the third transmission transistor and a first end of the first storage capacitor, and a third end of the second transmission transistor is configured to receive the second transmission control signal; a second end of the third transmission transistor is connected with the floating diffusion region, and a third end of the third transmission transistor is configured to receive the third transmission control signal; second ends of the first storage capacitor and the second storage capacitor are grounded.

4. The pixel cell of claim 3, wherein, In the first exposure stage, the first transfer transistor and the second transfer transistor are turned on, and the third transfer transistor is turned off, the first storage capacitor is configured to receive a first exposure signal collected in the first exposure stage from the photoelectric conversion unit, and store the first exposure signal according to a global control signal after the photoelectric conversion unit completes the second exposure; In the first exposure stage, the first transfer transistor is turned on, and the second transfer transistor and the third transfer transistor are turned off, the second storage capacitor is configured to receive a second exposure signal collected in the second exposure stage from the photoelectric conversion unit, and store the second exposure signal while the first storage capacitor stores the first exposure signal.

5. The pixel cell of claim 3, wherein, The first reset unit is a global reset transistor, the photoelectric conversion unit is a photodiode, the first end of the global reset transistor is connected with a power module, the second end of the global reset transistor is connected with the negative electrode of the photodiode, the third end of the global reset transistor is configured to receive a global control signal, the global control signal is used to control the conduction or the disconnection of the global reset transistor, and the photodiode is reset when the global reset transistor is turned on, or the operation of the charge transfer storage circuit and the signal output circuit is synchronously controlled.

6. The pixel unit of claim 5, wherein, When the global reset transistor is turned off, the photodiode is configured to receive a light signal and convert the light signal into a first exposure signal or a second exposure signal according to the length of time during which the global reset transistor is turned off.

7. The pixel cell of claim 5, wherein, The charge transfer storage circuit includes a first transfer transistor, a second transfer transistor, a third transfer transistor, a first storage capacitor and a second storage capacitor, and includes: After the photodiode completes the operation of the second exposure stage, the global reset transistor is turned on, and the first transfer transistor, the second transfer transistor and the third transfer transistor are all turned off, then the first storage capacitor is configured to store the received first exposure signal, and the second storage capacitor is configured to synchronously store the received second exposure signal.

8. The pixel cell of claim 7, wherein, The signal output circuit includes a reset transistor, the first end of the reset transistor is connected with a power module, the second end of the reset transistor is connected with the floating diffusion region, and the third end of the reset transistor is configured to receive a reset control signal, and the reset transistor is configured to reset the floating diffusion region when the reset transistor is turned on.

9. The pixel cell of claim 7, wherein, The signal output circuit further comprises a source follower transistor and a pixel selection transistor, a first end of the source follower transistor is connected with the power module, a second end of the source follower transistor is connected with a first end of the pixel selection transistor, a third end of the source follower transistor is connected with the floating diffusion region, and the third end of the source follower transistor is used for reading the exposure signal from the floating diffusion region; a second end of the pixel selection transistor is used for outputting the exposure signal; a third end of the pixel selection transistor is used for receiving a selection control signal, and the selection control signal is used for controlling the working state of the pixel selection transistor; when the pixel selection transistor is turned on and the third transfer transistor is turned on, the floating diffusion region is configured to read the first exposure signal collected in the first exposure stage from the first storage capacitor; when the pixel selection transistor is turned on and the third transfer transistor and the second transfer transistor are simultaneously turned on, the floating diffusion region is configured to read the second exposure signal in the second exposure stage from the second storage capacitor.

10. The pixel cell of any of claims 1-9, wherein, The exposure time length of the first exposure stage is greater than the exposure time length of the second exposure stage, the first exposure stage is used for collecting dark light image information, and the second exposure stage is used for collecting relatively strong light image information.

11. An image sensor, comprising: The image sensor comprises the pixel array. The image sensor comprises the pixel array.

12. An electronic device, comprising: The image sensor comprises the pixel array.

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