image sensor

Abstract

The utility model provides a kind of image sensor, including pixel array, and pixel array includes several pixel blocks arranged in array again;Pixel block includes several image acquisition pixel units and at least one exposure adjustment pixel unit, image acquisition pixel unit is based on first control and obtains first parameter and carries out exposure readout operation, exposure adjustment pixel unit is based on second control and obtains second parameter and carries out exposure readout operation, wherein, based on the pixel information under the first parameter of single frame acquisition image acquisition pixel unit corresponding and the pixel information under the second parameter of exposure adjustment pixel unit corresponding is acquired.The utility model solves the problem that the existing automatic exposure control scheme exists slower response speed.

Description

Technical Field

[0001] This utility model relates to the field of image sensor technology, and in particular to an image sensor. Background Technology

[0002] CMOS image sensors offer advantages such as low voltage, low power consumption, low cost, and high integration, making them valuable for applications in machine vision, consumer electronics, high-definition surveillance, and medical imaging. During camera shooting, parameters that need adjustment include aperture, focal length, exposure time (shutter speed), ISO sensitivity, and white balance. Cameramen typically adjust these parameters manually for different shooting scenarios to achieve optimal image quality. For high-speed applications, such as surveillance cameras, autonomous driving sensing, and aerial photography, continuous images over a period of time need to be captured. During this time, factors such as distance, lighting, and color temperature may change, and the photographer may not be able to adjust exposure parameters in time. This is where the importance of Automatic Exposure Control (AEC) becomes apparent.

[0003] Currently, the commonly used implementation process of automatic exposure control is as follows: Figure 1 As shown: First, brightness statistics are performed on the current frame image, and the exposure value is determined based on the brightness of the current frame image. Then, new exposure parameters are calculated, including exposure time, aperture, gain, etc. Finally, the new exposure parameters are applied to the camera to capture the next frame image, and the above steps are repeated until the brightness meets the requirements. However, when the scene brightness changes significantly, such as the instant a car exits a tunnel, the above automatic exposure control method generally requires several consecutive frames before the exposure parameters can be adjusted to a suitable value. The slow automatic exposure response does not meet the needs of high-speed shooting, especially in fields such as autonomous driving. If suitable scene image information cannot be obtained in time, it may cause accidents in severe cases. Therefore, how to quickly achieve automatic exposure control is very important and has become a technical problem that those skilled in the art urgently want to solve.

[0004] 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 utility model 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 utility model. Utility Model Content

[0005] In view of the shortcomings of the prior art described above, the purpose of this utility model is to provide an image sensor to solve the problem of slow response speed in existing automatic exposure control schemes.

[0006] To achieve the above and other related objectives, this utility model provides an image sensor, which includes a pixel array comprising a plurality of pixel blocks arranged in an array.

[0007] The pixel block includes a plurality of image acquisition pixel units and at least one exposure adjustment pixel unit. The image acquisition pixel unit performs an exposure readout operation based on a first control to acquire a first parameter, and the exposure adjustment pixel unit performs an exposure readout operation based on a second control to acquire a second parameter. The pixel information of the image acquisition pixel unit under the first parameter and the pixel information of the exposure adjustment pixel unit under the second parameter are acquired based on a single frame.

[0008] Optionally, the pixel block includes a plurality of first pixel units and at least one second pixel unit, wherein the first pixel unit corresponds to the image acquisition pixel unit and the second pixel unit corresponds to the exposure adjustment pixel unit, wherein the first pixel unit performs an exposure operation based on a first transmission control signal and has a first exposure time, and the second pixel unit performs an exposure operation based on a second transmission control signal and has a second exposure time, and the first exposure time and the second exposure time are not equal.

[0009] Optionally, in each of the pixel blocks, at least one pixel block further includes at least one third pixel unit, the third pixel unit corresponding to the exposure adjustment pixel unit, wherein the third pixel unit performs an exposure operation based on a third transmission control signal and has a third exposure time; wherein the second exposure time changes in a first direction relative to the first exposure time, and the third exposure time changes in a second direction relative to the first exposure time, the first direction and the second direction being opposite.

[0010] Optionally, the number of the second pixel units in the pixel block is one, and in each pixel block arranged along the row direction, the second pixel units are arranged in the same row; when the pixel block further includes a third pixel unit, the number of the third pixel units in the pixel block is one, and in each pixel block arranged along the row direction, the third pixel unit is arranged in the same row; and / or, when the pixel block further includes a third pixel unit, in each pixel block arranged along the column direction, the third pixel unit and the second pixel unit are arranged in the same column.

[0011] Optionally, when the pixel block further includes a third pixel unit, each third pixel unit and each second pixel unit are arranged in different rows; and / or, the image sensor further includes a plurality of color filter units, each color filter unit corresponding one-to-one with each pixel unit, in each pixel block, every four adjacent pixel units constitute a Bayer color array, the Bayer color array includes a complementary color pixel unit, wherein the second pixel unit is arranged at the complementary color pixel unit in any Bayer color array, and when the pixel block further includes a third pixel unit, the third pixel unit is arranged at the complementary color pixel unit in another Bayer color array.

[0012] Optionally, the first pixel unit and the second pixel unit have the same circuit structure, each including a reset transistor, a transmission transistor, a photosensitive element, a source follower transistor, a row selection transistor, and a floating diffusion node. The control terminal of the reset transistor receives a reset control signal, its first terminal is connected to a reset potential, and its second terminal is connected to the floating diffusion node. The control terminal of the transmission transistor receives a corresponding transmission control signal, its first terminal is connected to the floating diffusion node, and its second terminal is connected to a reference potential via the photosensitive element. The control terminal of the source follower transistor is connected to the floating diffusion node, its first terminal is connected to a variable potential, and its second terminal is connected to the first terminal of the row selection transistor. The control terminal of the row selection transistor receives a row selection control signal, and its second terminal is connected to the corresponding column line. When the pixel block further includes a third pixel unit, the third pixel unit has the same circuit structure as the first and second pixel units; or, it further includes a gain transistor connected to the floating diffusion node for switching between different conversion gains.

[0013] Optionally, the first transmission control signal of the first pixel unit is transmitted based on the first transmission control line, the second transmission control signal of the second pixel unit is transmitted based on the second transmission control line, and when the pixel block further includes a third pixel unit, the third transmission control signal of the third pixel unit is transmitted based on the third transmission control line, wherein:

[0014] The first transmission control line and the second transmission control line corresponding to the same row of pixel units are different control lines, and the first transmission control line and the third transmission control line corresponding to the same row of pixel units are different control lines.

[0015] Optionally, the first parameter includes at least one of exposure time and exposure gain, the second parameter is of the same type as the first parameter but with a different value; and / or, in the pixel array, the proportion of the exposure adjustment pixel units is less than or equal to 20%.

[0016] As described above, the image sensor of this invention, by adding a pixel unit specifically for automatic exposure control to the pixel array, can acquire different exposure times in a single frame of image; by comparing and analyzing different exposure times, the adjustment time of exposure parameters can be shortened, effectively improving the response speed of automatic exposure control. Attached Figure Description

[0017] Figure 1 This is a flowchart of an existing automatic exposure control method.

[0018] Figure 2 The diagram shown is a schematic diagram of the pixel array in Embodiment 1 of this utility model.

[0019] Figure 3 The diagram shown is a structural schematic of a partial pixel unit of a pixel block in Embodiment 1 of this utility model.

[0020] Figure 4 The flowchart shown is a process for the automatic exposure control method in Embodiment 1 of this utility model.

[0021] Figure 5 This is a timing diagram showing the operation of two pixel units at each stage in Embodiment 1 of this utility model.

[0022] Figure 6 The diagram shown is a schematic diagram of the pixel array in Embodiment 2 of this utility model.

[0023] Figure 7 The diagram shown is a structural schematic of a partial pixel unit of a pixel block in Embodiment 2 of this utility model.

[0024] Figure 8 The flowchart shown is a process flow diagram of the automatic exposure control method in Embodiment 2 of this utility model.

[0025] Figure 9 This is a timing diagram showing the operation of each stage by the three pixel units in Embodiment 2 of this utility model.

[0026] Figure 10 This is a schematic diagram of a partial pixel unit of a pixel block in Embodiment 3 of this utility model.

[0027] Figure 11 Displayed as Figure 10 The timing diagram shows the operation of each stage for the two pixel units shown.

[0028] Figure 12 This is a schematic diagram of another structure of a local pixel unit of a pixel block in Embodiment 3 of this utility model.

[0029] Figure 13Displayed as Figure 12 The timing diagram shows the operation of each stage for the three pixel units shown.

[0030] Component designation explanation

[0031] 100-pixel array

[0032] 110 pixel blocks

[0033] 111 First pixel unit

[0034] 112 Second pixel unit

[0035] 113 Third pixel unit Detailed Implementation

[0036] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model 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 this utility model.

[0037] Please see Figures 2 to 13 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of this utility model. Therefore, the illustrations only show the components related to this utility model and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0038] Example 1

[0039] like Figure 2 As shown, this embodiment provides an image sensor, including a pixel array 100, wherein the pixel array 100 includes a plurality of pixel blocks 110 arranged in an array.

[0040] Pixel block 110 includes several image acquisition pixel units and at least one exposure adjustment pixel unit. The image acquisition pixel unit performs an exposure readout operation based on a first control to acquire a first parameter, and the exposure adjustment pixel unit performs an exposure readout operation based on a second control to acquire a second parameter. The pixel information of the image acquisition pixel unit under the first parameter and the pixel information of the exposure adjustment pixel unit under the second parameter are acquired based on a single frame.

[0041] In one implementation, the first parameter of the image acquisition pixel unit includes at least one of exposure time and exposure gain. The second parameter of the exposure adjustment parameter unit has the same type as the first parameter but a different value. The first control operation corresponding to the acquisition of the first parameter is different from the second control operation corresponding to the acquisition of the second parameter. Specifically, the first and second controls can be achieved by adding multiple transmission control lines in the row direction to control the transmission transistors, thereby obtaining different exposure times. Alternatively, the first and second controls can be achieved by adding additional readout quantization circuits to control the analog gain of the corresponding pixels. For example, by forming ramp signals with different slopes, the image acquisition pixel and the exposure adjustment pixel can obtain different analog gains. In an optional implementation, the first parameter includes exposure time, and the first and second controls can be achieved by adding multiple transmission control lines in the row direction to control the transmission transistors, thereby obtaining different exposure times.

[0042] Specifically, pixel block 110 includes a plurality of first pixel units 111 and at least one second pixel unit 112, wherein the plurality of first pixel units 111 and at least one second pixel unit 112 are arranged in an array in rows and columns in the area where pixel block 110 is located; at this time, the first pixel unit 111 is an image acquisition pixel unit, and the second pixel unit 112 is an exposure adjustment pixel unit. The first pixel unit 111 performs an exposure operation based on a first transmission control signal TX and has a first exposure time, and the second pixel unit 112 performs an exposure operation based on a second transmission control signal TX_AEC0 and has a second exposure time, wherein the first exposure time and the second exposure time are not equal, for example, the first exposure time is greater than the second exposure time, or the first exposure time is less than the second exposure time.

[0043] In one implementation, the proportion of exposure-adjusting pixel units in pixel array 100 is less than or equal to 20%; for example, the number of second pixel units 112 is less than or equal to 20% of the total number of effective pixel units in pixel array 100. In practical applications, the number of second pixel units 112 in pixel block 110 can be one or more than one, as long as the above proportional relationship is satisfied; the second pixel unit 112 is used to accelerate the implementation of automatic exposure control, so the second pixel unit 112 has an impact on the pixel units that actually participate in imaging in the pixel array. In order to avoid the impact of excessive number of them on image quality, the number of second pixel units 112 in pixel block 110 is designed to be one.

[0044] In one implementation, the first transmission control signal TX of the first pixel unit 111 is transmitted based on the first transmission control line, and the second transmission control signal TX_AEC0 of the second pixel unit 112 is transmitted based on the second transmission control line. The first and second transmission control lines corresponding to pixel units in the same row are different control lines. To simplify the control of each second pixel unit 112 in each pixel block 110, the second pixel units 112 in each pixel block 110 arranged along the row direction are placed in the same row, so that each second pixel unit 112 in the same row can be controlled by the same second transmission control signal TX_AEC0, thereby simplifying the number of control lines. Optionally, during the readout process, the first pixel unit 111 and the second pixel unit 112 in the readout row are read out simultaneously.

[0045] In addition, the image sensor also includes several color filter units (not shown in the figure), each of which corresponds one-to-one with each pixel unit, thereby realizing the extraction of the corresponding color light. In application, each color filter unit can extract the same color light or different colors of light, depending on the actual needs. As an optional solution, in each pixel block 110, every four adjacent pixel units form a Bayer color array, including a red pixel unit (R), a green pixel unit (G), a blue pixel unit (B), and a complementary color pixel unit; furthermore, a second pixel unit 112 is disposed at the complementary color pixel unit in the Bayer color array. It should be noted that the complementary color pixel unit can be a green pixel unit, a white pixel unit, or even other color pixel units, without limitation, but this embodiment uses a green pixel unit as an example; of course, the Bayer color array can also be other color arrangement arrays used in the prior art to achieve image acquisition.

[0046] In one implementation, such as Figure 3 As shown, the circuit structures of the first pixel unit 111 and the second pixel unit 112 are the same, both including a reset transistor M1, a transmission transistor M2, a photosensitive element PD, a source follower transistor M3, a row selection transistor M4, and a floating diffusion node FD.

[0047] For the first pixel unit 111: the control terminal of the reset transistor M1 receives the reset control signal RST, the first terminal of the reset transistor M1 is connected to the reset potential RSTD (e.g., power supply potential), and the second terminal of the reset transistor M1 is connected to the floating diffusion node FD; the control terminal of the transmission transistor M2 receives the first transmission control signal TX, the first terminal of the transmission transistor M2 is connected to the floating diffusion node FD, and the second terminal of the transmission transistor M1 is connected to the reference potential (e.g., ground potential or negative potential) via the photosensitive element PD; the control terminal of the source follower transistor M3 is connected to the floating diffusion node FD, the first terminal of the source follower transistor M3 is connected to the variable potential, and the second terminal of the source follower transistor M3 is connected to the first terminal of the row selection transistor M4; the control terminal of the row selection transistor M4 receives the row selection control signal RS, and the second terminal of the row selection transistor M4 is connected to the corresponding column line.

[0048] For the second pixel unit 112: the control terminal of the reset transistor M1 receives the reset control signal RST, the first terminal of the reset transistor M1 is connected to the reset potential RSTD (e.g., power supply potential), and the second terminal of the reset transistor M1 is connected to the floating diffusion node FD; the control terminal of the transmission transistor M2 receives the second transmission control signal TX_AEC0, the first terminal of the transmission transistor M2 is connected to the floating diffusion node FD, and the second terminal of the transmission transistor M1 is connected to the reference potential (e.g., ground potential or negative potential) via the photosensitive element PD; the control terminal of the source follower transistor M3 is connected to the floating diffusion node FD, the first terminal of the source follower transistor M3 is connected to the variable potential, and the second terminal of the source follower transistor M3 is connected to the first terminal of the row selection transistor M4; the control terminal of the row selection transistor M4 receives the row selection control signal RS, and the second terminal of the row selection transistor M4 is connected to the corresponding column line.

[0049] When designing pixel units using the above devices, the reset transistor M1, transmission transistor M2, source follower transistor M3, and row select transistor M4 are typically implemented using NMOS transistors. In this case, the control terminal is the gate terminal, the first terminal is the drain terminal, and the second terminal is the source terminal. Of course, it is also feasible to implement each transistor using PMOS transistors. The photosensitive element PD is typically implemented using a photodiode. Of course, it is also feasible to implement the photosensitive element using a grating or photoconductor. In addition, in each pixel unit, the number of transmission transistors M2 and photosensitive elements PD can be one or more. This embodiment takes the number of transmission transistors M2 and photosensitive elements PD as an example. In other implementations, when the number of transmission transistors M2 and photosensitive elements PD is multiple, the transmission transistors M2 and photosensitive elements PD correspond one-to-one. In a further optional example, the control terminal of each transmission transistor M2 receives the same transmission control signal to facilitate simultaneous conduction or deactivation.

[0050] In this embodiment, the difference between the first pixel unit 111 and the second pixel unit 112, which are arranged in the same row, is that the transmission control signal received by the control terminal of the transmission transistor M2 is different. In this way, the first pixel unit 111 and the second pixel unit 112 can have different exposure times.

[0051] like Figure 4 As shown, this embodiment also provides an automatic exposure control method, including steps S1 and S2.

[0052] Step S1: Capture an image frame based on the image sensor described above, wherein, during the acquisition of the image frame, a first control is performed to acquire a first parameter and a second control is performed to acquire a second parameter.

[0053] In one implementation, an image frame is captured using an image sensor, and the first exposure time corresponding to the first pixel unit 111 and the second exposure time corresponding to the second pixel unit 112 are obtained from it. This achieves the aforementioned first control to obtain the first parameter and the second control to obtain the second parameter. Specifically, an exposure operation is performed on the first pixel unit 111 based on a first transmission control signal to obtain the corresponding first exposure time, and an exposure operation is performed on the second pixel unit 112 based on a second transmission control signal to obtain the corresponding second exposure time.

[0054] Exposure time refers to the difference between the end time and the start time of exposure. When designing the exposure time, the first pixel unit 111 and the second pixel unit 112 can be exposed at the same time and end at different times, or they can be exposed at different times and end at the same time. Of course, it is also feasible to expose the first pixel unit 111 and the second pixel unit 112 at different times and end at different times, as long as the final two exposure times are different. As an optional solution, it is usually designed that the first pixel unit 111 and the second pixel unit 112 start exposure at different times and end at the same time. Furthermore, the first exposure time and the second exposure time can be unequal; the first exposure time can be greater than the second exposure time, or it can be less than the second exposure time. As an optional solution, it is usually designed that the first exposure time is less than the second exposure time.

[0055] In one embodiment, the method for obtaining the exposure time of each pixel unit includes: obtaining the time when the falling edge of the transmission control signal corresponding to each pixel unit is located during the reset phase, and obtaining the time when the falling edge of the transmission control signal corresponding to each pixel unit is located during the readout phase, and obtaining the exposure time of each pixel unit based on the two falling edge times.

[0056] For the first pixel unit 111: obtain the falling edge of the first transmission control signal TX during the reset phase and take it as the exposure start time; obtain the falling edge of the first transmission control signal TX during the readout phase and take it as the exposure end time; calculate the difference between the exposure end time and the exposure start time to obtain the first exposure time corresponding to the first pixel unit 111.

[0057] For the second pixel unit 112: obtain the falling edge of the second transmission control signal TX_AEC0 during the reset phase and take it as the exposure start time; obtain the falling edge of the second transmission control signal TX_AEC0 during the readout phase and take it as the exposure end time; calculate the difference between the exposure end time and the exposure start time to obtain the second exposure time corresponding to the second pixel unit 112.

[0058] The method for performing operations on each pixel unit at each stage includes the following steps; Figure 3 Taking the first pixel unit 111 and the second pixel unit 112 set in the same row in the circuit structure shown as an example, the specific operation methods of each stage are explained.

[0059] During the reset phase, each pixel unit is reset to generate a reset voltage Vrst.

[0060] For the second pixel unit 112: as Figure 5 As shown, during the time period t1 to t2, the reset control signal RST is high, the reset transistor M1 is turned on, and the second transmission control signal TX_AEC0 is high, which controls the transmission transistor M2 to turn on, thereby realizing the reset operation of the floating diffusion node FD and the photosensitive element PD and setting an initial voltage value for them.

[0061] For the first pixel unit 111: as follows Figure 5 As shown, during the time period t3 to t4, the reset control signal RST is high, the reset transistor M1 is turned on, and the first transmission control signal TX is high, which controls the transmission transistor M2 to turn on, thereby realizing the reset operation of the floating diffusion node FD and the photosensitive element PD and setting an initial voltage value for them.

[0062] During the exposure phase, each pixel unit is exposed and photogenerated electrons are accumulated in each pixel unit.

[0063] For the second pixel unit 112: as Figure 5 As shown, at time t2, the second transmission control signal TX_AEC0 changes from high level to low level, the control transmission transistor M2 is turned off, and the second pixel unit 112 begins to be exposed and accumulates photogenerated electrons in the photosensitive element.

[0064] For the first pixel unit 111: as follows Figure 5 As shown, at time t4, the first transmission control signal TX changes from high level to low level, the control transmission transistor M2 is turned off, and the first pixel unit 111 begins to be exposed and accumulates photogenerated electrons in the photosensitive element.

[0065] Wherein, time t2 is the exposure start time of the second pixel unit 112, time t4 is the exposure start time of the first pixel unit 111, and the exposure start time of the second pixel unit 112 is earlier than the exposure start time of the first pixel unit 111.

[0066] During the readout phase, the reset voltage Vrst of each pixel unit is read out, the photogenerated electrons accumulated in each pixel unit are transferred to generate the pixel voltage Vsig, and the pixel voltage Vsig of each pixel unit is read out.

[0067] For the second pixel unit 112: as Figure 5 As shown, during the time period t5 to t6, the row selection control signal RS is high, the row selection transistor M4 is turned on, and the reset voltage Vrst is read out; during the time period t7 to t8, the second transmission control signal TX_AEC0 is high, the transmission transistor M2 is turned on, the photogenerated electrons accumulated in the photosensitive element are transferred to the floating diffusion node FD and the pixel voltage Vsig is generated; during the time period t9 to t10, the pixel voltage Vsig is read out.

[0068] For the first pixel unit 111: as follows Figure 5 As shown, during the time period t5 to t6, the row selection control signal RS is high, the row selection transistor M4 is turned on, and the reset voltage Vrst is read out; during the time period t7 to t8, the first transmission control signal TX is high, the transmission transistor M2 is turned on, the photogenerated electrons accumulated in the photosensitive element are transferred to the floating diffusion node FD and the pixel voltage Vsig is generated; during the time period t9 to t10, the pixel voltage Vsig is read out.

[0069] In this case, both the first pixel unit 111 and the second pixel unit 112 end their exposure at time t8, which is the end time of the exposure of the two pixel units. Since the exposure start time of the second pixel unit 112 is earlier than the exposure start time of the first pixel unit 111, the first exposure time corresponding to the first pixel unit 111 is less than the second exposure time corresponding to the second pixel unit 112.

[0070] In addition, in this example, for both the first pixel unit 111 and the second pixel unit 112, before the row selection transistor M4 is turned on, the reset control signal RST changes from a high level to a low level, the reset transistor M1 is turned off, and a reset voltage Vrst is generated at the floating diffusion node FD.

[0071] Step S2: The pixel information of the image acquisition pixel unit under the first parameter, the pixel information of the exposure adjustment pixel unit under the second parameter, and the preset pixel information are compared and analyzed to achieve automatic exposure control.

[0072] In one implementation, automatic exposure control is achieved by comparing and analyzing pixel information corresponding to a first exposure time, pixel information corresponding to a second exposure time, and preset pixel information. Specifically, the pixel information corresponding to the first exposure time includes the pixel brightness at the first exposure time, the pixel information corresponding to the second exposure time includes the pixel brightness at the second exposure time, and the preset pixel information includes the preset pixel brightness.

[0073] In one implementation, the method for achieving automatic exposure control includes: comparing and analyzing pixel information corresponding to a given exposure time with preset pixel information based on scene changes to determine whether the given exposure time meets the requirements; if it meets the requirements, updating the exposure parameters using the given exposure time; if it does not meet the requirements, adjusting the exposure parameters with the given exposure time as a reference to update the parameters. Thus, automatic exposure control is achieved through the aforementioned acceleration.

[0074] Taking a scenario where the first exposure time is less than the second exposure time as an example: When transitioning from a bright scene to a dark scene, it's typically necessary to extend the exposure time. For instance, if the first exposure time corresponds to the bright scene, and comparative analysis shows the second exposure time meets the requirements, then the second exposure time replaces the first exposure time to update the exposure parameters. If comparative analysis shows the second exposure time does not meet the requirements, the first exposure time can be adjusted further, for example, by making it greater than the second exposure time, and the exposure parameters are updated accordingly until the requirements are met. By designing the second exposure time, exposure values ​​with both the first and second exposure times can be acquired simultaneously in a single frame, shortening the parameter adjustment time when transitioning from a bright scene to a dark scene, thus accelerating automatic exposure control. Determining whether the requirements are met can be based on designing an interval of values ​​that the image sensor can output. A preset range within this interval can be selected as a reference range; if the data output by the corresponding exposure time falls within this reference range, then the requirements are met.

[0075] In one implementation, pixel information corresponding to each pixel unit in the pixel array is read out based on row-wise control. The exposure adjustment pixel unit and the corresponding image acquisition pixel unit in the row region are read out simultaneously under different controls. Specifically, the row-wise control-based readout can be a row-by-row readout, a half-row readout, or a quarter-row readout, aiming to select the readout based on row control lines. In this implementation, although the image acquisition pixel unit and the exposure adjustment pixel unit have different first and second parameters in the readout row, they can be read out simultaneously. For example, the image acquisition pixel unit has a first exposure time controlled by a transmission control line, and the exposure adjustment pixel unit has a second exposure time controlled by a different transmission control line. Thus, under different controls—the first control and the second control—readout is achieved in that row, and the corresponding analog data can be simultaneously output and quantized.

[0076] Example 2

[0077] like Figure 6 As shown, this embodiment provides an image sensor. The difference from Embodiment 1 is that in this embodiment, at least one pixel block 110 further includes at least one third pixel unit 113. In an optional example, each pixel block 110 includes at least one third pixel unit 113; in this case, each pixel block 110 includes a plurality of first pixel units 111, at least one second pixel unit 112, and at least one third pixel unit 113, where the third pixel unit 113 is an exposure adjustment pixel unit; wherein the plurality of first pixel units 111, at least one second pixel unit 112, and at least one third pixel unit 113 are arranged in an array in rows and columns in the area where the pixel block 110 is located.

[0078] The third pixel unit 113 performs an exposure operation based on the third transmission control signal TX_AEC1 and has a third exposure time, wherein the second exposure time changes in a first direction relative to the first exposure time, and the third exposure time changes in a second direction relative to the first exposure time, with the first and second directions being opposite; for example, the second exposure time changes in a positive direction relative to the first exposure time, and the third exposure time changes in a negative direction relative to the first exposure time, in which case the second exposure time is greater than the first exposure time, and the third exposure time is less than the first exposure time; or, the second exposure time changes in a negative direction relative to the first exposure time, and the third exposure time changes in a positive direction relative to the first exposure time, in which case the second exposure time is less than the first exposure time, and the third exposure time is greater than the first exposure time.

[0079] In one implementation, the proportion of exposure-adjusting pixel units in pixel array 100 is less than or equal to 20%; for example, the total number of second pixel units 112 and third pixel units 113 is less than or equal to 20% of the total number of effective pixel units in pixel array 100. In practical applications, the number of third pixel units 113 in pixel block 110 can be one or more than one. Furthermore, the number of second pixel units 112 and the number of third pixel units 113 in the entire pixel array 100 can be the same or different, as long as the above proportional relationship is satisfied. The third pixel unit 113 is used to accelerate the implementation of automatic exposure control, so the third pixel unit 113 has an impact on the pixel units that actually participate in imaging in the pixel array. To avoid the impact of excessive number of third pixel units 113 on image quality, the number of third pixel units 113 in pixel block 110 is designed to be one.

[0080] In one implementation, the first transmission control signal TX of the first pixel unit 111 is transmitted based on the first transmission control line, the second transmission control signal TX_AEC0 of the second pixel unit 112 is transmitted based on the second transmission control line, and the third transmission control signal TX_AEC1 of the third pixel unit 113 is transmitted based on the third transmission control line. Specifically, the first and second transmission control lines corresponding to pixel units in the same row are different control lines, and the first and third transmission control lines corresponding to pixel units in the same row are also different control lines. Further, to simplify the control of each third pixel unit 113 in each pixel block 110, the third pixel units 113 in each pixel block 110 arranged along the row direction are placed in the same row, so that each third pixel unit 113 in the same row can be controlled by the same third transmission control signal TX_AEC1, thereby simplifying the number of control lines. Optionally, during the readout process, the first pixel unit 111 and the third pixel unit 113 in the readout row are read out simultaneously. In one example, each third pixel unit 113 and each second pixel unit 112 are arranged in different rows; further, in each pixel block 110 arranged along the column direction, the third pixel unit 113 and the second pixel unit 112 are arranged in the same column.

[0081] In addition, for the case where the image sensor includes several color filter units (not shown in the figure), as an optional solution, in each pixel block 110, every four adjacent pixel units constitute a Bayer color array, including a red pixel unit (R), a green pixel unit (G), a blue pixel unit (B), and a complementary color pixel unit; furthermore, the second pixel unit 112 is disposed at the complementary color pixel unit in any Bayer color array, and the third pixel unit 113 is disposed at the complementary color pixel unit in another Bayer color array.

[0082] In one implementation, the Bayer color array corresponding to the second pixel unit 112 and the Bayer color array corresponding to the third pixel unit 113 do not overlap in the row direction. Taking the Bayer color array corresponding to the second pixel unit 112 as an example, it is set in the first row and the second row, and the Bayer color array corresponding to the third pixel unit 113 is set in any two adjacent rows other than the first row and the second row, such as the third row and the fourth row, the fifth row and the sixth row, the seventh row and the eighth row, etc. Furthermore, the Bayer color array corresponding to the second pixel unit 112 and the Bayer color array corresponding to the third pixel unit 113 overlap in the column direction. Taking the Bayer color array corresponding to the second pixel unit 112 as an example, it is set in the first column and the second column, and the Bayer color array corresponding to the third pixel unit 113 is also set in the first column and the second column.

[0083] In one implementation, such as Figure 7 As shown, the circuit structure of the third pixel unit 113 is the same as that of the first pixel unit 111 and the second pixel unit 112, both including a reset transistor M1, a transmission transistor M2, a photosensitive element PD, a source follower transistor M3, a row selection transistor M4, and a floating diffusion node FD.

[0084] For the third pixel unit 113: the control terminal of the reset transistor M1 receives the reset control signal RST, the first terminal of the reset transistor M1 is connected to the reset potential RSTD (e.g., power supply potential), and the second terminal of the reset transistor M1 is connected to the floating diffusion node FD; the control terminal of the transmission transistor M2 receives the third transmission control signal TX_AEC1, the first terminal of the transmission transistor M2 is connected to the floating diffusion node FD, and the second terminal of the transmission transistor M1 is connected to the reference potential (e.g., ground potential or negative potential) via the photosensitive element PD; the control terminal of the source follower transistor M3 is connected to the floating diffusion node FD, the first terminal of the source follower transistor M3 is connected to the variable potential, and the second terminal of the source follower transistor M3 is connected to the first terminal of the row selection transistor M4; the control terminal of the row selection transistor M4 receives the row selection control signal RS, and the second terminal of the row selection transistor M4 is connected to the corresponding column line.

[0085] In this embodiment, the difference between the first pixel unit 111 and the third pixel unit 113, which are arranged in the same row, is that the transmission control signal received by the control terminal of the transmission transistor M2 is different. In this way, the first pixel unit 111, the second pixel unit 112 and the third pixel unit 113 can have different exposure times.

[0086] like Figure 8 As shown, this embodiment also provides an automatic exposure control method, which differs from Embodiment 1 in steps S1 and S2.

[0087] In step S1, performing the second control to obtain the second parameters includes: performing the second control on the second pixel unit 112 to obtain its corresponding second parameters and performing the second control on the third pixel unit 113 to obtain its corresponding second parameters. In one embodiment, an image frame is captured based on an image sensor, and the first exposure time corresponding to the first pixel unit 111, the second exposure time corresponding to the second pixel unit 112, and the third exposure time corresponding to the third pixel unit 113 are obtained from the frame. Specifically, the first exposure time is obtained by performing an exposure operation on the first pixel unit 111 based on a first transmission control signal, the second exposure time is obtained by performing an exposure operation on the second pixel unit 112 based on a second transmission control signal, and the third exposure time is obtained by performing an exposure operation on the third pixel unit 113 based on a third transmission control signal.

[0088] When designing the exposure time, the first pixel unit 111, the second pixel unit 112, and the third pixel unit 113 can be exposed at the same time and end at different times, or they can be exposed at different times and end at the same time. Of course, other design methods are also feasible and there is no restriction. As an optional solution, it is usually designed that the first pixel unit 111, the second pixel unit 112, and the third pixel unit 113 start exposure at different times and end exposure at the same time. In addition, the three exposure times must satisfy the following: the second exposure time is greater than the first exposure time, and the third exposure time is less than the first exposure time, or the second exposure time is less than the first exposure time, and the third exposure time is greater than the first exposure time. As an optional solution, it is usually designed that the second exposure time is greater than the first exposure time, and the third exposure time is less than the first exposure time.

[0089] In one embodiment, the method for obtaining the third exposure time corresponding to the third pixel unit 113 is the same as the method for obtaining the exposure time corresponding to the first pixel unit 111 or the second pixel unit 112 in Embodiment 1; specifically, the falling edge of the third transmission control signal TX_AEC1 in the reset phase is obtained and used as the exposure start time, the falling edge of the third transmission control signal TX_AEC1 in the readout phase is obtained and used as the exposure end time, and the difference between the exposure end time and the exposure start time is calculated to obtain the third exposure time corresponding to the third pixel unit 113.

[0090] The method for performing each stage operation on the third pixel unit 113 is the same as the method for performing each stage operation on the first pixel unit 111 or the second pixel unit 112 in Embodiment 1; Figure 7 Taking the circuit structure shown as an example, the specific operation method of the third pixel unit 113 at each stage will be explained.

[0091] During the reset phase, such as Figure 9 As shown, during the time period t5 to t6, the reset control signal RST is high, the reset transistor M1 is turned on, and the third transmission control signal TX_AEC1 is high, which controls the transmission transistor M2 to turn on, thereby realizing the reset operation of the floating diffusion node FD and the photosensitive element PD, and setting an initial voltage value for them.

[0092] During the exposure phase, such as Figure 9 As shown, at time t6, the third transmission control signal TX_AEC1 changes from high level to low level, controlling the transmission transistor M2 to turn off, and the third pixel unit 113 begins exposure and accumulates photogenerated electrons in the photosensitive element; where time t6 is the exposure start time of the third pixel unit 113, and time t4 is the exposure start time of the first pixel unit 111, the exposure start time of the third pixel unit 113 is later than the exposure start time of the first pixel unit 111.

[0093] Reading phase, such as Figure 9 As shown, during the time intervals t7 to t8, the row selection control signal RS is high, the row selection transistor M4 is turned on, and the reset voltage Vrst is read out. During the time intervals t9 to t10, the third transmission control signal TX_AEC1 is high, the transmission transistor M2 is turned on, and the photogenerated electrons accumulated in the photosensitive element are transferred to the floating diffusion node FD to generate the pixel voltage Vsig. During the time intervals t11 to t12, the pixel voltage Vsig is read out. All three pixel units end their exposure at time t10, which is the end time of exposure for all three pixel units. Since the exposure start time of the second pixel unit 112 is earlier than that of the first pixel unit 111, and the exposure start time of the third pixel unit 113 is later than that of the first pixel unit 111, the first exposure time corresponding to the first pixel unit 111 is less than the second exposure time corresponding to the second pixel unit 112 but greater than the third exposure time corresponding to the third pixel unit 113.

[0094] In addition, in this example, for the first pixel unit 111, the second pixel unit 112 and the third pixel unit 113, before the row selection transistor M4 is turned on, the reset control signal RST changes from a high level to a low level, the reset transistor M1 is turned off, and a reset voltage Vrst is generated at the floating diffusion node FD.

[0095] In step S2, a comparative analysis is performed based on the pixel information corresponding to the first exposure time, the pixel information corresponding to the second exposure time, the pixel information corresponding to the third exposure time, and the preset pixel information to achieve automatic exposure control. Specifically, the pixel information corresponding to the first exposure time includes the pixel brightness at the first exposure time, the pixel information corresponding to the second exposure time includes the pixel brightness at the second exposure time, the pixel information corresponding to the third exposure time includes the pixel brightness at the third exposure time, and the preset pixel information includes the preset pixel brightness.

[0096] Taking a first exposure time that is less than the second exposure time but greater than the third exposure time as an example: For the transition from a bright scene to a dark scene, the process is the same as in Example 1, and the relevant details can be found in Example 1, which will not be repeated here. For the transition from a dark scene to a bright scene, it is usually necessary to shorten the exposure time. For example, in this case, the first exposure time is the exposure time corresponding to the dark scene. If, through comparative analysis, it is found that the third exposure time meets the requirements, then the third exposure time replaces the first exposure time and the exposure parameters are updated accordingly. If, through comparative analysis, it is found that the third exposure time does not meet the requirements, then the exposure time is adjusted further, for example, by making the first exposure time less than the third exposure time and updating the exposure parameters accordingly, until the requirements are met. Through the design of the third exposure time, exposure values ​​with both the first and third exposure times can be obtained simultaneously in one frame of image, which can shorten the parameter adjustment time when transitioning from a dark scene to a bright scene, and is beneficial for comprehensively accelerating the realization of automatic exposure control. In other words, in this example, pixel quantization values ​​corresponding to three different exposure times can be obtained in one frame of image to determine whether the requirements are met.

[0097] Example 3

[0098] like Figure 10 and Figure 12 As shown, this embodiment provides an image sensor. The difference between this embodiment and Embodiment 1 or Embodiment 2 is that in the pixel block 110 of this embodiment, the circuit structure of each pixel unit further includes a gain transistor M5, connected to a floating diffusion node FD, for switching between different conversion gains, such as switching between low and high conversion gains. It should be noted that the so-called low and high conversion gains in this embodiment are only two relative conversion gains; in reality, it is feasible to achieve more conversion gain switching by adding switching transistors.

[0099] In one embodiment, gain transistor M5 is connected between reset transistor M2 and floating diffusion node FD. In this case, the control terminal of gain transistor M5 receives gain control signal DCG, the first terminal of gain transistor M5 is connected to the second terminal of reset transistor M2, and the second terminal of gain transistor M5 is connected to floating diffusion node FD. Of course, in other embodiments, gain transistor M5 can also have different connection methods. For example, the control terminal of gain transistor M5 receives gain control signal DCG, the first terminal of gain transistor M5 is connected to floating diffusion node FD, and the second terminal of gain transistor M5 is connected to a reference potential (e.g., ground potential). Alternatively, the second terminal of gain transistor M5 can be connected to the reference potential (e.g., ground potential) through a gain capacitor, where the gain capacitor can be a device capacitor, such as a MIM capacitor.

[0100] In this embodiment, when designing pixel units using gain transistor M5, gain transistor M5 is usually implemented using an NMOS transistor. In this case, the control terminal is the gate terminal, the first terminal is the drain terminal, and the second terminal is the source terminal. Of course, it is also feasible to implement gain transistor M5 using a PMOS transistor.

[0101] like Figure 11 and Figure 13 As shown, this embodiment also provides an automatic exposure control method, which differs from Embodiment 1 or Embodiment 2 in that the specific method for performing the readout stage operation on each pixel unit in step S1 is different.

[0102] In the readout stage of this embodiment, firstly, the conversion gain of each pixel unit is switched, and the reset voltage Vrst corresponding to each pixel unit is read out under different conversion gains; then, the photogenerated electrons accumulated in each pixel unit are transferred to generate the pixel voltage Vsig, and the pixel voltage Vsig corresponding to each pixel unit is read out under different conversion gains by switching the conversion gain of each pixel unit.

[0103] like Figure 13 As shown, the specific methods of the readout stage operation of the first pixel unit 111, the second pixel unit 112 and the third pixel unit 113 are described; since the specific methods of the readout stage operation of the three pixel units are exactly the same, this embodiment takes the third pixel unit 113 as an example.

[0104] At time t8, the gain control signal DCG is high, the gain transistor M5 is turned on, and the image sensor operates at low conversion gain. By making the row selection control signal RS high, the row selection transistor M4 is turned on, enabling the readout operation of the reset voltage Vrst at low conversion gain. Afterward, the gain control signal DCG changes from high to low, the gain transistor M5 is turned off, and the image sensor switches from low conversion gain to high conversion gain, thereby enabling the readout operation of the reset voltage Vrst at high conversion gain.

[0105] During the time interval t9 to t10, the third transmission control signal TX_AEC1 is at a high level, and the transmission transistor M2 is turned on. Under high conversion gain, the photogenerated electrons accumulated in the photosensitive element are transferred to the floating diffusion node FD to generate the pixel voltage Vsig. During the time interval t10 to t11, the pixel voltage Vsig is read out under high conversion gain. During the time interval t11 to t12, the gain control signal DCG changes from low level to high level, and the image sensor switches from high conversion gain to low conversion gain again. By making the third transmission control signal TX_AEC1 high level, the transmission transistor M2 is turned on. Under low conversion gain, the photogenerated electrons accumulated in the photosensitive element are transferred to the floating diffusion node FD to generate the pixel voltage Vsig. During the time interval t12 to t13, the pixel voltage Vsig is read out under low conversion gain.

[0106] In this embodiment, the application scope of the automatic exposure control scheme of this application is expanded by designing the gain transistor M5. Furthermore, by introducing different conversion gains in a single frame and comparing them with a preset conversion gain, the current conversion gain can be optimized. It should be noted that if multiple falling edges of the corresponding transmission control signals exist for each pixel unit during the readout stage, the moment of the first falling edge is taken as the exposure end time for each pixel unit.

[0107] In summary, the image sensor of this invention, by adding a dedicated pixel unit for automatic exposure control to the pixel array, can acquire different exposure times within a single image frame. By comparing and analyzing these different exposure times, the adjustment time for exposure parameters can be shortened, effectively improving the response speed of automatic exposure control. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0108] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. An image sensor, characterized in that, The image sensor includes a pixel array, which comprises a plurality of pixel blocks arranged in an array. The pixel block includes a plurality of image acquisition pixel units and at least one exposure adjustment pixel unit. The image acquisition pixel unit performs an exposure readout operation based on a first control to acquire a first parameter, and the exposure adjustment pixel unit performs an exposure readout operation based on a second control to acquire a second parameter. The pixel information under the first parameter corresponding to the image acquisition pixel unit and the pixel information under the second parameter corresponding to the exposure adjustment pixel unit are acquired based on a single frame. Both the image acquisition pixel unit and the exposure adjustment pixel unit include a transmission transistor. The control terminal of the transmission transistor in the image acquisition pixel unit is connected to a first transmission control line, and the control terminal of the transmission transistor in the exposure adjustment pixel unit is connected to a second transmission control line. The first transmission control line and the second transmission control line corresponding to the same row of pixel units are different transmission control lines. The first parameter includes exposure time, the second parameter is of the same type as the first parameter but with a different value, and the first control and the second control are implemented by adding multiple transmission control lines in the row direction.

2. The image sensor according to claim 1, characterized in that, The first pixel unit corresponds to the image acquisition pixel unit, and the second pixel unit corresponds to the exposure adjustment pixel unit. The number of second pixel units in the pixel block is one, and in each pixel block arranged along the row direction, each second pixel unit is set in the same row.

3. The image sensor according to claim 2, characterized in that, In each of the pixel blocks, at least one pixel block further includes at least one third pixel unit, the third pixel unit corresponding to the exposure adjustment pixel unit; the third pixel unit includes a transmission transistor, and the control terminal of the transmission transistor in the third pixel unit is connected to a third transmission control line, wherein the first transmission control line and the third transmission control line corresponding to the pixel units in the same row are different transmission control lines.

4. The image sensor according to claim 3, characterized in that, The number of third pixel units in the pixel block is one; in each pixel block arranged along the row direction, each third pixel unit is set in the same row; and / or, in each pixel block arranged along the column direction, the third pixel unit and the second pixel unit are set in the same column.

5. The image sensor according to claim 4, characterized in that, Each third pixel unit and each second pixel unit are set in a different row.

6. The image sensor according to any one of claims 2 to 5, characterized in that, The image sensor also includes several color filter units, each color filter unit corresponding to a pixel unit. In each pixel block, every four adjacent pixel units form a Bayer color array. The Bayer color array includes a complementary color pixel unit. The second pixel unit is located at the complementary color pixel unit in any Bayer color array. When the pixel block also includes a third pixel unit, the third pixel unit is located at the complementary color pixel unit in another Bayer color array.

7. The image sensor according to claim 1 or 3, characterized in that, Each pixel unit has the same circuit structure, including a reset transistor, a photosensitive element, a source follower transistor, a row selection transistor, and a floating diffusion node. The control terminal of the reset transistor receives a reset control signal, its first terminal is connected to a reset potential, and its second terminal is connected to the floating diffusion node. The control terminal of the transmission transistor receives a corresponding transmission control signal, its first terminal is connected to the floating diffusion node, and its second terminal is connected to a reference potential via the photosensitive element. The control terminal of the source follower transistor is connected to the floating diffusion node, its first terminal is connected to a variable potential, and its second terminal is connected to the first terminal of the row selection transistor. The control terminal of the row selection transistor receives a row selection control signal, and its second terminal is connected to the corresponding column line. Alternatively, a gain transistor connected to the floating diffusion node may be included for switching between different conversion gains.

8. The image sensor according to claim 1, characterized in that, In the pixel array, the proportion of the exposure adjustment pixel units is less than or equal to 20%.

Images