Image sensor exposure control method and image sensor

Abstract

The invention provides an image sensor exposure control method and an image sensor. An exposure stage of each frame of image is divided into a pre-reading time period and a subsequent effective exposure time period. In the pre-reading time period, each pixel unit is controlled to be subjected to pre-exposure, and the voltage signals of the pixel units are read when the pre-exposure is finished. The current brightness interval of each pixel unit is determined by comparing the voltage signal with a plurality of preset threshold voltages, and corresponding shutter channels and shutter control parameters are distributed for the pixel units according to the current brightness interval. And after the end of the pre-reading time period, emptying the charge of each pixel unit, and controlling the effective exposure of the pixel units based on the distributed shutter control parameters in the effective exposure time period, thereby realizing the pixel-level dynamic exposure control for different brightness intervals. According to the embodiment of the invention, effective exposure data in different brightness intervals can be simultaneously acquired in a single frame, high dynamic range imaging is realized, and multi-frame synthesis is avoided, so that the data volume of redundant image acquisition and storage is reduced.

Description

Technical Field

[0001] The present invention relates to the field of image processing technology, and in particular to an image sensor exposure control method and an image sensor. Background Art

[0002] As the requirements for image acquisition quality and real-time performance in application scenarios such as autonomous driving, industrial inspection, and biological imaging continue to increase, image sensors have exposed significant bottlenecks in dynamic range, response speed, noise resistance, and local detail capture.

[0003] Traditional exposure control solutions typically use a global shutter or rolling shutter approach, controlling the exposure of all pixels with a uniform exposure time. This approach struggles to capture details in both bright and dark areas in high dynamic range scenes (such as those with both bright and dark light), resulting in image distortion or increased noise, limiting the sensor's versatility in complex environments.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0005] In view of the problems in the prior art, the purpose of the present invention is to provide an image sensor exposure control method and an image sensor, which overcome the difficulties of the prior art and can solve the technical problem of the limited application scope of related art image sensors.

[0006] The present disclosure provides an image sensor exposure control method, which includes: During a pre-reading period starting from the start of the exposure phase of the current frame image, each pixel unit is controlled to pre-exposure, and at the end of the pre-exposure, a voltage signal of each pixel unit is pre-read, wherein the voltage signal reflects the degree of light response of the current scene brightness to the light of the pixel unit; Determine the current brightness range corresponding to each pixel unit based on the comparison results of the voltage signal of each pixel unit and multiple threshold voltages; allocating a corresponding shutter channel according to the current brightness range of each pixel unit, wherein at least two pixel units having different current brightness ranges are respectively allocated different shutter channels, and shutter control parameters of different shutter channels are different; After the pre-reading time period ends, the charge of each pixel unit is cleared, and in the effective exposure time period, the shutter channel allocated to each pixel unit is scheduled, and the corresponding pixel unit is effectively exposed based on the corresponding shutter control parameters to obtain the current frame image.

[0007] Optionally, allocating a corresponding shutter channel according to the current brightness range of each pixel unit includes: According to the current brightness range of each pixel unit, a corresponding shutter channel number is assigned and written into a register array, where each pixel unit corresponds to one or more register fields; The step of scheduling the shutter channel allocated to each pixel unit includes: Based on the shutter channel numbers stored in the register array, the shutter channel corresponding to each pixel unit is scheduled through row and column selection signals.

[0008] Optionally, the shutter channels are triggered in a staggered manner within a plurality of clock cycles to control the exposure of each pixel unit based on a corresponding shutter control parameter.

[0009] Optionally, the shutter control parameter includes an effective exposure time, so that the effective exposure processes of different pixel units partially overlap in the effective exposure time.

[0010] Optionally, pre-reading the voltage signal of each pixel unit includes: pre-reading the voltage signal of the pixel unit inside the pixel unit.

[0011] Optionally, each of the pixel units includes a source follower, a selection transistor, and a lateral overflow integration capacitor; and pre-reading the voltage signal of the pixel unit inside the pixel unit includes: The source follower converts the voltage on the floating diffusion node or the lateral overflow integration capacitor into the voltage signal output by the selection transistor.

[0012] Optionally, determining a current brightness interval corresponding to each pixel unit according to a comparison result of the voltage signal of each pixel unit with a plurality of threshold voltages includes: Acquire multiple threshold voltages arranged from low to high and their corresponding multiple brightness intervals, use a step-by-step comparison or parallel comparison method to determine the threshold voltage level corresponding to the voltage signal of each pixel unit, and determine the corresponding current brightness interval based on the threshold voltage level.

[0013] Optionally, the pixel unit includes a photodiode, a transfer transistor, a reset transistor, and a lateral overflow integration capacitor; and clearing the charge of each pixel unit includes: The charge in the photodiode is transferred to a floating diffusion node through the transfer transistor, and the charge in the floating diffusion node or the lateral overflow integration capacitor is cleared through the reset transistor.

[0014] Optionally, the image sensor further includes a pre-read reset transistor and a pre-read transfer transistor, each of the pre-read reset transistors is coupled to each of the reset transistors in the same row of pixel units, and each of the pre-read transfer transistors is coupled to each of the transfer transistors in the same row of pixel units; clearing the charge of each of the pixel units specifically includes: By controlling the pre-read transfer transistor, each transfer transistor in the same row of pixel units transfers the charge in the photodiode to the floating diffusion node, and by controlling the pre-read reset transistor, each reset transistor in the same row of pixel units clears the charge of the floating diffusion node or the lateral overflow integration capacitor.

[0015] A second aspect of the present disclosure provides an image sensor, comprising: A pixel array comprising a plurality of pixel units; An exposure control logic module is connected to the pixel array and is configured as follows: During a pre-reading period starting from the start of the exposure phase of the current frame image, each pixel unit is controlled to pre-exposure, and at the end of the pre-exposure, a voltage signal of each pixel unit is pre-read, wherein the voltage signal reflects the degree of light response of the current scene brightness to the light of the pixel unit; Determine the current brightness range corresponding to each pixel unit based on the comparison results of the voltage signal of each pixel unit and multiple threshold voltages; allocating a corresponding shutter channel according to the current brightness range of each pixel unit, wherein at least two pixel units having different current brightness ranges are respectively allocated different shutter channels, and shutter control parameters of different shutter channels are different; After the pre-reading time period ends, the charge of each pixel unit is cleared, and in the effective exposure time period, the shutter channel allocated to each pixel unit is scheduled, and the corresponding pixel unit is effectively exposed based on the corresponding shutter control parameters to obtain the current frame image.

[0016] Optionally, the image sensor adopts a stacked chip structure, including a main chip integrating the pixel array and a second chip consisting of the exposure control logic module.

[0017] Optionally, the pixel unit includes a photodiode, a transfer transistor, a reset transistor, and a lateral overflow integration capacitor; the exposure control logic module is further configured to clear the charge of each pixel unit in the following manner: The charge in the photodiode is transferred to a floating diffusion node through the transfer transistor, and the charge in the floating diffusion node or the lateral overflow integration capacitor is cleared through the reset transistor.

[0018] Optionally, the image sensor further includes a pre-read reset transistor and a pre-read transfer transistor, each of the pre-read reset transistors is coupled to each of the reset transistors in the same row of pixel units, and each of the pre-read transfer transistors is coupled to each of the transfer transistors in the same row of pixel units; the exposure control logic module is specifically configured as follows: By controlling the pre-read transfer transistor, each transfer transistor in the same row of pixel units transfers the charge in the photodiode to the floating diffusion node, and by controlling the pre-read reset transistor, each reset transistor in the same row of pixel units clears the charge of the floating diffusion node or the lateral overflow integration capacitor.

[0019] The image sensor exposure control method and image sensor proposed in the embodiments of the present disclosure have the following advantages: In this embodiment, the exposure phase of each frame of an image is divided into a pre-reading period and a subsequent effective exposure period. During the pre-reading period, each pixel unit is controlled to perform pre-exposure, and its voltage signal is read at the end of the pre-exposure. The voltage signal represents the degree of response of the pixel unit to the current incident light intensity and can be used to determine its light response level. By comparing the voltage signal with multiple preset threshold voltages, the current brightness range of each pixel unit is determined, and the corresponding shutter channel and shutter control parameters are assigned accordingly. After the pre-reading period ends, the charge of each pixel unit is cleared, and during the effective exposure period, the effective exposure of the pixel unit is controlled based on the assigned shutter control parameters, thereby achieving pixel-level dynamic exposure control for different brightness ranges.

[0020] Compared to related technologies, this implementation can simultaneously acquire effective exposure data for different brightness ranges within a single frame, achieving high dynamic range imaging and avoiding multi-frame synthesis, thereby reducing the amount of redundant image acquisition and storage data. It can also significantly enhance the image sensor's imaging adaptability in conditions with high brightness differences, high-speed motion, or complex lighting. This method is suitable for image sensor systems that require precise exposure control in complex lighting and rapidly changing environments, such as autonomous driving, high-speed detection, and biological imaging.

[0021] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objects and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0023] Figure 1 This is one of the flow charts of the image sensor exposure control method provided in an embodiment of the present disclosure; Figure 2A circuit architecture diagram of an image sensor provided by an embodiment of the present disclosure is shown; Figure 3-Figure 6 Based on the Figure 1 Schematic diagram of four exposure process principles of the image sensor exposure control method shown; Figure 7 Display based on Figure 1 A schematic diagram of the working timing of an exposure process of the image sensor exposure control method shown; Figure 8 A schematic diagram showing the pixel array in the image sensor and the corresponding operating timing; Figure 9 and Figure 10 Display based on Figure 1 Schematic diagram of various shutter channel timings of the image sensor exposure control method shown; Figure 11 A shutter channel timing diagram is shown; Figure 12 An architectural diagram showing an image sensor provided by an embodiment of the present disclosure; Figure 13 exhibit Figure 12 Block diagram of the exposure control logic module in the image sensor shown. DETAILED DESCRIPTION

[0024] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be embodied in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0025] In addition, the accompanying drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale. Identical reference numerals in the figures denote identical or similar parts, and thus repetitive descriptions thereof will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities that do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0026] In related technologies, some image sensors generate high dynamic range imaging HDR (High Dynamic Range) images through multi-frame image fusion, but this requires multiple exposures and data processing, which increases power consumption and latency, making it difficult to balance frame rate requirements and dynamic range performance.

[0027] To improve the dynamic range performance of image sensors, related technologies have proposed multiple optimization paths: Dual Conversion Gain (DCG): Reads signals from two different gain paths in a single exposure to cover a wider dynamic range; Multiple Exposure High Dynamic Range (ME-HDR): This technology captures multiple images with different exposure times in one or more frames and fuses them together to enhance the image's dynamic range. The dynamic range represents the image sensor's ability to adapt to light intensity. A higher value indicates the sensor's ability to capture both bright and dark details simultaneously, making it suitable for imaging environments with strong contrast and high brightness differences.

[0028] These solutions have made technical progress in improving dynamic range, but the following technical problems still exist: Data redundancy and processing burden: Fusion solutions, especially those using staggered high dynamic range (HDR), require the output and storage of multiple frames, significantly increasing the system's data throughput and computational burden. Furthermore, current exposure control is based on entire rows or frames, making it difficult to optimize overexposed or underexposed areas in complex scenes.

[0029] Therefore, while existing solutions improve the dynamic range, they also face problems such as large data volume, low response accuracy and insufficient pixel control capabilities, which limit their application adaptability under complex lighting conditions.

[0030] The disclosed embodiments propose an image sensor exposure control method and image sensor. By integrating a pixel-level pre-read voltage analysis mechanism with a multi-channel exposure signal allocation strategy, this method dynamically adjusts the exposure path of individual pixels between image frames, achieving true pixel-level adaptive exposure control. This technical solution reduces data redundancy and improves frame rates through efficient data scheduling, making it particularly suitable for imaging tasks in high-brightness, high-speed, and complex lighting environments.

[0031] Figure 1 The flowchart of the image sensor exposure control method provided by the embodiment of the present disclosure is shown. The execution subject of this method is an exposure control logic (ESL) module or a chip integrating the exposure control logic module, such as Figure 1 As shown, the image sensor exposure control method of this embodiment includes but is not limited to the following steps: Step 110: Controlling pre-exposure of each pixel unit during a pre-reading period starting from the start of the current frame image exposure phase, and pre-reading a voltage signal of each pixel unit at the end of the pre-exposure, wherein the voltage signal reflects the degree of response of the current scene brightness to the illumination of the pixel unit; Step 120: Determine the current brightness range corresponding to each pixel unit based on the comparison results of the voltage signal of each pixel unit and multiple threshold voltages; Step 130: allocating a corresponding shutter channel according to the current brightness range of each pixel unit, wherein at least two pixel units having different current brightness ranges are respectively allocated different shutter channels, and the shutter control parameters of different shutter channels are different; Step 140: After the pre-reading time period ends, the charge of each pixel unit is cleared, and in the effective exposure time period, the shutter channel allocated to each pixel unit is scheduled, and the corresponding pixel unit is controlled to be effectively exposed based on the corresponding shutter control parameters to obtain the current frame image.

[0032] In this embodiment, the exposure phase of each frame of an image is divided into a pre-reading period and a subsequent effective exposure period. During the pre-reading period, each pixel unit is controlled to perform pre-exposure, and its voltage signal is read at the end of the pre-exposure. The voltage signal represents the degree of response of the pixel unit to the current incident light intensity and can be used to determine its light response level. By comparing the voltage signal with multiple preset threshold voltages, the current brightness range of each pixel unit is determined, and the corresponding shutter channel and shutter control parameters are assigned accordingly. After the pre-reading period ends, the charge of each pixel unit is cleared, and during the effective exposure period, the effective exposure of the pixel unit is controlled based on the assigned shutter control parameters, thereby achieving pixel-level dynamic exposure control for different brightness ranges.

[0033] Compared to related technologies, this implementation can simultaneously acquire effective exposure data for different brightness ranges within a single frame, achieving high dynamic range imaging and avoiding multi-frame synthesis, thereby reducing the amount of redundant image acquisition and storage data. It can also significantly enhance the image sensor's imaging adaptability in conditions with high brightness differences, high-speed motion, or complex lighting. This method is suitable for image sensor systems that require precise exposure control in complex lighting and rapidly changing environments, such as autonomous driving, high-speed detection, and biological imaging.

[0034] In the disclosed embodiment, to assess the current scene brightness, each pixel unit is controlled to perform pre-exposure during a pre-read period starting from the start of the current frame image exposure phase, and the voltage signal of the pixel unit is collected at the end of the pre-exposure. For example, the pre-read period can be 10 microseconds or other time interval between the end of pre-exposure and the start of effective exposure.

[0035] In one embodiment, a voltage signal can be pre-read directly within the pixel unit. This voltage signal reflects the current scene brightness's response to the pixel unit's illumination and can be used to characterize the brightness range (e.g., low, medium, or high) within which the incident light intensity received by the pixel unit falls. Pre-reading within the pixel unit avoids interference caused by long-distance transmission of analog signals, improves signal sampling reliability, and eliminates the need to output the voltage signal through an external analog-to-digital conversion path to complete brightness determination.

[0036] Combined with reference Figure 2 As shown, it shows four pixel units in the same column: Pixel 1, Pixel 2, Pixel 3, and Pixel 4. Taking Pixel 1 as an example, the pixel circuit in the pixel unit includes a photodiode PD, a transfer transistor TX, a floating diffusion node (FD), a switching transistor DCG, a reset transistor RST, a lateral overflow integration capacitor (LOFIC) Cs, a first power supply Vddrst, a second power supply Vddsf, a source follower SF (Source Follower), a select transistor SEL, and a column output bus OUT. The anode of the photodiode PD is connected to ground, the cathode of the photodiode PD is connected to the source of the transfer transistor TX, the drain of the transfer transistor TX is connected to the floating diffusion node FD and the source of the switching transistor DCG, the drain of the switching transistor DCG is connected to the top plate of the lateral overflow integration capacitor Cs, the drain of the reset transistor RST is connected to the first power supply Vddrst, and the bottom plate of the lateral overflow integration capacitor Cs is connected to ground.

[0037] exist Figure 2 In the pixel circuit based on the LOFIC structure shown, the floating diffusion node FD has an associated floating diffusion capacitor Cfd, which temporarily stores the voltage signal converted from photogenerated charge. After the current frame image exposure begins, a pre-read period begins. The pixel cell is controlled to perform pre-exposure during this period. At the end of the pre-read period, the transfer transistor TX is turned on, transferring the charge accumulated in the photodiode PD to the floating diffusion node FD or the lateral overflow integrating capacitor Cs. During the pre-read operation, the source follower SF buffers the voltage at the floating diffusion node FD or the lateral overflow integrating capacitor Cs into an analog voltage signal. After turning on the select transistor SEL, the voltage is output to the column bus, forming the pre-read voltage signal Vpix_pre. Vpix_pre is temporarily stored in the column register array via the column select signal ColSel. It is then read by the Exposure Setting Logic (ESL) module, compared with multiple threshold voltages to determine the brightness range and assign the corresponding shutter channel and shutter control parameters.

[0038] The introduction of LOFIC helps to guide the excess charge into the additional capacitor in the highlight scenario, prevent charge overflow and expand the charge accommodation capacity of the pixel unit, so as to maintain the linear response of Vpix_pre under highlight conditions and improve the accuracy of brightness interval determination.

[0039] In addition, as Figure 2 shown, after the end of the effective exposure phase, it enters the image readout (Readout) phase. The FD node stores the photo-generated charge generated by the effective exposure and converts it into an effective voltage signal, which is then output to the column bus through SF and SEL to obtain the formal output data Vout of this frame of image.

[0040] In an alternative embodiment, the column circuit or row buffer stage can also be used to pre-read the voltage signal and perform brightness judgment, and specific optimization design can be carried out according to the application scenario and system integration.

[0041] After obtaining the voltage signal, perform step 120 above, and use the voltage signal of each pixel unit to determine its current brightness interval. The brightness interval is the brightness level range divided according to multiple threshold voltages (representing the light intensity). Each brightness interval corresponds to a class of light intensity ranges, which can be preset according to the specific scenario. Combining Figure 3 shown, Vrst represents the reset voltage, and Vsat represents the saturation voltage. Taking the time before the shutter channel 0 is triggered as an example, the exposure control logic module compares the pre-read Vpix_pre with multiple preset threshold voltages (exemplarily, Vref1, Vref2, Vref3), determines the current brightness interval of each pixel unit, and assigns the corresponding shutter channel and shutter control parameters thereto accordingly. The shutter control parameters of different shutter channels can include different exposure times.

[0042] Taking Figure 3 as an example, after the pre-read time period T0, at the termination time point of T0, the pre-read voltage signal Vpix_pre is greater than the first threshold voltage Vref1 (Vpix_pre > Vref1), and Vref1 corresponds to the low brightness interval, then Figure 3 the pixel unit shown corresponds to the low brightness interval; Before Figure 4 shown Shutter 1, after the pre-read time period T0, the voltage signal Vpix_pre is between the second threshold voltage Vref2 and the first threshold voltage Vref1 (Vref2 < Vpix_pre ≤ Vref1), corresponding to the medium-low brightness interval; Before Figure 5Before the Shutter 2 shown, after a pre-reading time period T0, the voltage signal Vpix_pre is between the third threshold voltage Vref3 and the second threshold voltage Vref2 (Vref3 < Vpix_pre ≤ Vref2), corresponding to the medium-high brightness range; Before Figure 6 the Shutter 3 shown, after a pre-reading time period T0, the voltage signal Vpix_pre is less than Vref3 (Vpix_pre ≤ Vref3), corresponding to the high brightness range.

[0043] As above Figure 3-Figure 6 Four threshold voltages and the corresponding four brightness ranges are shown above as an example. In actual applications, the number of threshold voltages and the number of corresponding brightness ranges can be designed as needed.

[0044] In the above embodiment, a plurality of threshold voltages arranged from low to high and their corresponding plurality of brightness ranges are obtained, and a step-by-step comparison or parallel comparison method is used to determine the threshold voltage level corresponding to the voltage signal of each pixel unit, and the corresponding current brightness range is determined based on the threshold voltage level.

[0045] Among them, the step-by-step comparison method means that Vpix_pre is sequentially compared with a plurality of threshold voltages arranged from low to high. If Vpix_pre meets the set conditions (for example, greater than a certain threshold voltage), it is determined as the corresponding current brightness level, and its belonging threshold voltage level is determined. The parallel comparison method means that Vpix_pre is simultaneously compared with all threshold voltages through a comparator array, significantly improving the processing speed. In this way, according to the comparison results, the brightness range number (such as 0: low brightness, 1: medium brightness, 2: high brightness) is output, and this number is mapped to the corresponding shutter channel number for the exposure control logic module to allocate shutter control parameters.

[0046] In the embodiment of the present disclosure, after determining the current brightness range corresponding to each pixel unit, step 130 is executed to allocate a corresponding shutter channel for each pixel unit based on the current brightness range of each pixel unit, and corresponding shutter control parameters are provided through each shutter channel.

[0047] Optionally, the shutter channel can correspond to a combination of a hardware trigger signal (such as EXRST) and a logic port for scheduling corresponding shutter control parameters. There may be a mapping relationship between the current brightness range, the shutter channel, and the shutter control parameters. Among them, pixel units with the same current brightness range can share the shutter channel to reduce the occupation of shutter channel resources.

[0048] In some embodiments, the shutter control parameters may include: Exposure time control strategy: Allocate different effective exposure times for different brightness ranges to avoid overexposure or underexposure. For example, long exposure time is allocated to low brightness ranges and short exposure time is allocated to high brightness ranges. Gain control strategy: Assign different analog gain or digital gain levels to pixel cells. This can be used alone or in combination with exposure time control strategies to achieve a wider dynamic range, such as switching between high conversion gain (HCG) and low conversion gain (LCG). Exposure mode switching strategy: Select the integration path of the pixel unit, such as switching between the main capacitor path and the lateral overflow integration capacitor (LOFIC) path, which can enable LOFIC shunt in the high brightness range to improve charge holding capacity.

[0049] Optionally, the shutter channel allocation can be configured in batches by row, column or pixel group within the pixel array, or can be configured independently for a single pixel; the channel allocation method can adopt different implementation methods such as hardware register writing, lookup table mapping or firmware algorithm dynamic calculation.

[0050] During the effective exposure time period, the exposure control logic module can activate each shutter channel according to a preset scheduling strategy, output corresponding trigger signals and control parameters, thereby implementing differentiated exposure control for pixel units in different brightness ranges and realizing pixel-level dynamic exposure adjustment.

[0051] In some embodiments, in order to implement the above-mentioned shutter channel allocation based on brightness intervals, the following register array-based implementation method may be adopted: Based on the current brightness range of each pixel unit, a corresponding shutter channel number is assigned and written into a register array. Each pixel unit corresponds to one or more register fields. In this way, the exposure control logic module can schedule the corresponding shutter channel via row and column selection signals based on the shutter channel number stored in the register array, and control the exposure of the corresponding pixel unit based on the corresponding shutter control parameters, thereby generating a single frame image.

[0052] In one example, if Figure 3-Figure 6 As shown in the figure, Te represents the effective exposure time. The mapping relationship between brightness ranges and shutter channels (for example, Shutter0 to Shutter3) can be: Shutter0 is assigned to the low brightness range (corresponding to the longest exposure time), Shutter1 is assigned to the medium-low brightness range, Shutter2 is assigned to the medium-high brightness range, and Shutter3 is assigned to the high brightness range (corresponding to the shortest exposure time). This mapping relationship can be adjusted according to specific application scenarios.

[0053] Each pixel cell occupies one or more fields in the register array to store the shutter channel number (e.g., binary 00 represents Shutter 0, 01 represents Shutter 1, 10 represents Shutter 2, and so on). The exposure control logic module writes the shutter channel number to the register array via the data bus and synchronizes updates with the system controller via the I2C interface to ensure real-time and accurate allocation results. The register array's efficient storage structure supports fast batch reads, row or column access, and multiplexing across multiple frames, optimizing system performance.

[0054] In the disclosed embodiment, during step 140, the shutter channels are triggered in a staggered manner over multiple clock cycles. The staggered triggering activates the channels sequentially at equal or varying intervals within each clock cycle to control the exposure of each pixel unit based on the corresponding shutter control parameters. By staggering the triggering timing of the corresponding shutter channels in the staggered shutter manner, exposure control is achieved for the corresponding pixel units.

[0055] Combine Figure 2 and Figure 7 As shown, the exposure control logic module sends an EXRST (ExtendedReset) signal to the corresponding row of pixel units as a reset control signal for resetting the floating diffusion node (FD) or other charge storage nodes to Vddrst. Figure 7 EXRST1 to EXRST4 correspond to Figures 3 to 6 Reset control signal of pixel units in different exposure intervals (shutter0~shutter3).

[0056] Among them, Figure 7 In the shutter phase, the previous frame's signal is cleared and the current frame's exposure is initiated. The pre-read period prepares for the current frame's exposure. After the pre-read period, the effective exposure period begins. During the pre-read period, pixel rows are selected using the SEL, TXread, and RSTread signals to pre-sample the voltage signals. During the effective exposure period, the ΦExpo signal is pulled high, and EXRST1 through EXRST4 are sequentially pulled high, activating the exposure windows of the corresponding shutter channels, forming a staggered shutter strategy.

[0057] Further references Figure 8In the pixel array shown, Row Address represents the row address, and EXRST1 to EXRST4 are reset control signals corresponding to four types of pixel units. Different pixel units in the same row respond to different EXRST signals to achieve classified triggering. For example, taking the first row with Row Address = 0 as an example, in response to the EXRST1 signal, three corresponding pixel units of the same type are synchronously triggered; in response to the EXRST2 signal, two corresponding pixel units of the same type are synchronously triggered. The three corresponding pixel units of the same type corresponding to the EXRST1 signal and the two corresponding pixel units of the same type corresponding to the EXRST2 signal are staggered. In this way, EXRST1 to EXRST4 correspond to four types of pixel units, achieving classification and staggered triggering of pixel units in the same row.

[0058] Figure 2 The pixel circuit shown includes a pre-read reset transistor, RSTread, and a pre-read transfer transistor, TXread, whose control terminals are coupled to the reset transistor, RST, and transfer transistor, TX, in the same row of pixels. This embodiment uses ΦExpo pulses to control the timing of the RSTread and TXread signals, managing exposure initiation and charge processing for each row of pixels. EXRST<1:4> pulses are applied via the column address decoding logic to activate the corresponding shutter path, enabling sequential exposure on a row-by-row, class-by-class basis.

[0059] The specific timing is: During the shutter phase of the previous frame, the DCG, TXread, and RSTread gates are all pulled high to reset the pixels in the same row and prepare for pre-reading. ΦExpo remains low, and effective exposure setting has not yet begun.

[0060] During the pre-read period, SEL is briefly pulled high to enable the corresponding row pixel circuit. TXread is pulled low and then briefly pulled high, transferring the charge in the PD to the FD. SF buffers the analog voltage and outputs it to the column bus via SEL, forming a voltage signal Vpix_pre that reflects the current light intensity. A reset is not performed during this phase to ensure that the sampled data accurately reflects the current brightness. TXread is then pulled low, and RSTread remains low to prevent the pre-read signal from being cleared.

[0061] During the effective exposure period, ΦExpo is pulled high, and the shutter channels EXRST1 to EXRST4 corresponding to the same pixel unit are sequentially pulled high in a staggered manner. Different shutter channels are assigned to different shutter channels and exposure is started in a time-sharing manner, forming a staggered exposure strategy (StaggeredShutter). After the effective exposure ends, ΦExpo returns to a low level, TXread, RSTread, and SEL are pulled high, and the image readout phase begins.

[0062] This implementation uses a phased exposure control sequence, dividing the current frame exposure into pre-read and effective exposure phases, optimizing the trade-off between exposure accuracy and system frame rate. During the pre-read phase, ΦExpo and SEL are used to select row pixels, controlling TXread and RSTread to enable the transmission and reset channels, respectively. This completes charge clearing and pre-sampling before voltage signal pre-sampling, providing accurate brightness input for effective exposure.

[0063] During the effective exposure period, different shutter channels (EXRST1-EXRST4) are sequentially pulled high to control the exposure start time of the corresponding pixel, achieving pixel-level exposure control and adaptive exposure time adjustment. This solution effectively reduces the instantaneous bandwidth pressure of the column bus, improves frame rate, enhances dynamic range, and optimizes image fusion latency, making it suitable for high-speed, high-brightness-difference acquisition tasks.

[0064] This implementation uses row and column strobe signals to coordinate, enabling different exposure times for different pixels in a two-dimensional pixel array, even if they are in the same row or column. This supports fine-grained pixel-level exposure control and adapts to high brightness gradients and complex lighting environments. The readout timing after exposure is consistent with that of a traditional dual-conversion-gain (DCG) pixel structure.

[0065] Traditional non-interleaved shutter methods require sequential exposure and readout of various shutter types. Due to the large number of pixel array rows, the overall exposure cycle is long, limiting the system frame rate. With this interleaved exposure method, different columns use different exposure paths within the same clock cycle, eliminating interference, reducing column bus contention, and increasing the maximum frame rate.

[0066] In conjunction with the above, the row and column selection signals include the row select signal (RowSel, ΦExpo pulse) and the column select signal (ColSel). RowSel activates the pixel array row by row, while ColSel decodes the shutter channel number stored in the column decode register array to schedule the shutter channel for each pixel. Scheduling is completed within a single row processing cycle, ensuring high efficiency. Triggering uses a staggered shutter mechanism, with the shutter channel triggering times staggered (for example, Shutter0 at T0+0ns, Shutter1 at T0+10ns, and Shutter2 at T0+20ns). The logic control module generates the ΦExpo pulse to control the start of exposure.

[0067] There are three specific schemes for staggered triggering: Option 1 ( Figure 9 ): Shutter 1 is triggered after shutter 0 in the array is triggered, and so on. The starting points of different exposure channels do not overlap to avoid mutual interference between EXRST channels in the same column, but the effective exposure time design is limited.

[0068] Option 2 ( Figure 10): Compared with Solution 1, various shutters are staggered and the exposure time overlaps, which improves design flexibility and adapts to various scenarios.

[0069] Solution 3: Further improve the trigger overlap of different shutter channels, compress the shutter trigger window, and increase the upper frame rate limit. Optimize the hardware architecture through a dual-column ADC structure to improve parallel readout capability, shorten readout time, and improve frame rate.

[0070] Compared with the traditional Stagger HDR solution that only outputs one frame of image, this implementation supports pixel-level exposure time control and can independently adjust pixel exposure time, thereby improving exposure flexibility while simplifying data transmission and subsequent processing, reducing system bandwidth usage and image fusion delay.

[0071] Comparing Schemes 2 and 3, by compressing the shutter channel triggering interval, the effective exposure processes of different pixel units are partially overlapped in the effective exposure time, thereby shortening the frame period and improving the system frame rate.

[0072] Combine Figure 11 In high-frame-rate applications, pre-read operations can be interleaved during normal pixel readout. For example, pre-read operations are introduced during the readout process on the left, implementing a "sliding window" interleaving design. This design, similar to staggered exposure, improves exposure design flexibility and maximum frame rate, increases the effective exposure time limit, and reduces signal loss due to charge overflow.

[0073] The present disclosure also provides an image sensor, referring to Figure 12 , the image sensor may include: A pixel array 1 comprising a plurality of pixel units 11; The exposure control logic module 2 is connected to the pixel array 1 and is configured as follows: During the pre-reading period starting from the start of the current frame image exposure phase, each pixel unit 11 is controlled to pre-expose, and at the end of the pre-exposure, a voltage signal of each pixel unit is pre-read, wherein the voltage signal reflects the degree of response of the current scene brightness to the illumination of the pixel unit 11; Determine the current brightness interval corresponding to each pixel unit 11 according to the comparison result of the voltage signal of each pixel unit 11 and multiple threshold voltages; Allocating a corresponding shutter channel according to the current brightness range of each pixel unit 11, wherein at least two pixel units with different current brightness ranges are respectively allocated different shutter channels, and the shutter control parameters of different shutter channels are different; After the pre-reading time period ends, the charge of each pixel unit 11 is cleared, and in the effective exposure time period, the shutter channel allocated to each pixel unit 11 is scheduled, and the corresponding pixel unit 11 is effectively exposed based on the corresponding shutter control parameters to obtain the current frame image.

[0074] The image sensor based on this embodiment combines a pixel-level pre-read voltage analysis mechanism with a multi-channel exposure signal allocation strategy. This allows for dynamic adjustment of the shutter channel of individual pixel units for the effective exposure of each frame, achieving true adaptive adjustment of pixel-level shutter control parameters. This technical solution significantly reduces data redundancy and improves system frame rates through efficient data scheduling, making it particularly suitable for imaging tasks in environments with high brightness differences, high-speed motion, and complex lighting conditions.

[0075] Exposure control logic module 2 is connected to pixel array 1 via a high-speed data bus and performs exposure control. Specifically, exposure control logic module 2 performs the following functions: It compares each pixel's Vpix_pre value with various threshold voltages to determine the corresponding current brightness range. Based on the current brightness range, a shutter channel number (Shutter0 through Shutter3, as shown above) is assigned and written to a register array. Subsequently, during the active exposure period of the current frame, the shutter channel numbers in the register array are used to schedule each shutter channel using row select signals (RowSel, corresponding to the ΦExpo signal) and column select signals (ColSel, decoded from the EXRST signal). These channels are activated one by one using staggered triggering, achieving staggered exposure across multiple shutter channels, ultimately generating a single HDR image.

[0076] This solution not only improves the flexibility and precision of pixel-level exposure control, but also reduces the instantaneous bandwidth pressure of the column bus through staggered triggering, effectively improving the overall frame rate and dynamic range, and greatly enhancing the imaging performance of image sensors in complex environments.

[0077] In this embodiment, if Figure 13 As shown, the exposure control logic module 2 may specifically include the following modules: The pre-reading module 1310 is used to control the pre-exposure of each pixel unit during the pre-reading period starting from the exposure phase of the current frame image, and pre-read the voltage signal of each pixel unit at the end of the pre-exposure; A voltage comparison module 1320 is configured to determine a current brightness range corresponding to each pixel unit based on a comparison result of a voltage signal of each pixel unit with a plurality of threshold voltages; an allocating module 1330 for allocating a corresponding shutter channel according to a current brightness range of each pixel unit, wherein at least two pixel units with different current brightness ranges are respectively allocated different shutter channels, and the shutter control parameters of the different shutter channels are different; The exposure module 1340 is used to clear the charge of each pixel unit after the pre-reading time period ends, and in the effective exposure time period, control the effective exposure of the corresponding pixel unit based on the corresponding shutter control parameters by scheduling the shutter channel assigned to each pixel unit to obtain the current frame image.

[0078] In this embodiment, pixel-level exposure control is achieved by introducing the above program module into the exposure control logic module 2 .

[0079] In an optional embodiment, the shutter channels are triggered in a staggered manner within multiple clock cycles to control the exposure of each pixel unit based on the corresponding shutter control parameters.

[0080] In an optional embodiment, the shutter control parameters include an effective exposure time, so that the effective exposure time intervals of different pixel units partially overlap, thereby compressing the overall exposure time and being compatible with the exposure requirements of different types of pixel units.

[0081] In an optional implementation manner, the exposure control logic module 2 is specifically configured to: pre-read the voltage signal of the pixel unit inside the pixel unit.

[0082] In an alternative embodiment, in combination Figure 2 As shown, each pixel unit includes a source follower SF, a selection transistor SEL and a lateral overflow integration capacitor Cs; the exposure control logic module 2 is configured as follows: The voltage on the floating diffusion node FD or the lateral overflow integration capacitor Cs is converted into the voltage signal output by the selection transistor SEL through the source follower SF.

[0083] In an optional embodiment, the exposure control logic module 2 is configured to: Obtain multiple threshold voltages arranged from low to high and their corresponding multiple brightness intervals, use step-by-step comparison or parallel comparison to determine the threshold voltage level corresponding to the voltage signal of each pixel unit 11, and determine the corresponding current brightness interval based on the threshold voltage level.

[0084] In an optional embodiment, the pixel unit includes a photodiode PD, a transfer transistor TX, a reset transistor RST, and a lateral overflow integration capacitor Cs; the exposure control logic module 2 is further configured to clear the charge of each pixel unit in the following manner: The charge of the photodiode PD is transferred to the floating diffusion node FD through the transfer transistor TX, and the charge of the floating diffusion node FD or the lateral overflow integration capacitor Cs is immediately cleared through the reset transistor RST after the pre-reading is completed.

[0085] In an alternative embodiment, reference Figure 2 As shown, the image sensor includes a pre-read reset transistor RSTread and a pre-read transfer transistor TXread, wherein the control terminal of each pre-read reset transistor RSTread is coupled to the control terminal of each reset transistor RST in the same row of pixel units, and the control terminal of each pre-read transfer transistor TXread is coupled to the control terminal of each transfer transistor TX in the same row of pixel units; the exposure control logic module 2 is further configured as follows: By controlling the pre-read transfer transistor TXread, each transfer transistor TX in the same row of pixel units transfers the charge in the photodiode PD to the floating diffusion node, and by controlling the pre-read reset transistor RSTread, each reset transistor RST in the same row of pixel units clears the charge of the floating diffusion node FD or the lateral overflow integration capacitor Cs.

[0086] Combine Figure 2 As shown, during the pre-read period after the current frame image exposure phase begins, the pixel unit converts the voltage on the floating diffusion node FD or the lateral overflow integration capacitor Cs into a voltage signal Vpix_pre through the source follower SF. This voltage signal is then selected by ColSel via the column output bus OUT and stored in the column register. The reset operation transfers the charge of PD to FD via TX, and then clears the charge of FD or Cs via RST. The pre-read transfer transistor TXread and the pre-read reset transistor RSTread control the reset of the pixel units in the same row. Multiple rows of pixel units share the pre-read transfer transistor and pre-read reset transistor, optimizing the chip layout area.

[0087] In this embodiment, the image sensor utilizes a stacked chip structure, comprising a main chip integrating the pixel array and a second chip comprising the exposure control logic module. The main chip is configured to lay out the pixel array and specifically pre-read the voltage signal for each pixel unit. The exposure control logic module can perform voltage signal pre-reading operations via the main chip. For example, the main chip can perform pre-reading operations under the instructions of the second chip.

[0088] The stacked chip structure described above enables decoupling between functional modules and optimized allocation of system resources. The division of labor described above yields the following technical advantages: By placing the exposure control logic module on a second chip, the size of the main chip is significantly reduced, making the chip area more manageable and suitable for high-pixel-density layouts. At the same time, logic power consumption is reduced, helping to meet the needs of mobile devices or power-sensitive scenarios. The exposure control logic module is physically and functionally decoupled from the pixel array, allowing different exposure control logic modules to be flexibly replaced or upgraded based on scenario requirements, improving design flexibility and maintainability. This ultimately enables the image sensor in this case to support system-level expansion for large-scale image arrays or special control requirements (such as high-speed linear exposure control). Furthermore, the stacked chip structure allows for the flexible deployment of higher computing power or parallel control logic, resolving the control resource bottleneck problem in traditional single-chip architectures.

[0089] Other embodiments of the present disclosure will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the appended claims.

Claims

1. An image sensor exposure control method, characterized in that: include: During a pre-reading period starting from the start of the exposure phase of the current frame image, each pixel unit is controlled to pre-exposure, and at the end of the pre-exposure, a voltage signal of each pixel unit is pre-read, wherein the voltage signal reflects the degree of light response of the current scene brightness to the light of the pixel unit; Determine the current brightness range corresponding to each pixel unit based on the comparison results of the voltage signal of each pixel unit and multiple threshold voltages; allocating a corresponding shutter channel according to the current brightness range of each pixel unit, wherein at least two pixel units having different current brightness ranges are respectively allocated different shutter channels, and shutter control parameters of different shutter channels are different; After the pre-reading time period ends, the charge of each pixel unit is cleared, and in the effective exposure time period, the shutter channel allocated to each pixel unit is scheduled, and the corresponding pixel unit is effectively exposed based on the corresponding shutter control parameters to obtain the current frame image.

2. The image sensor exposure control method according to claim 1, wherein: The allocating a corresponding shutter channel according to the current brightness range of each pixel unit includes: According to the current brightness range of each pixel unit, a corresponding shutter channel number is assigned and written into a register array, where each pixel unit corresponds to one or more register fields; The step of scheduling the shutter channel allocated to each pixel unit includes: Based on the shutter channel numbers stored in the register array, the shutter channel corresponding to each pixel unit is scheduled through row and column selection signals.

3. The image sensor exposure control method according to claim 1, wherein: in, The shutter channels are triggered in a staggered manner within a plurality of clock cycles to control the exposure of each pixel unit based on a corresponding shutter control parameter.

4. The image sensor exposure control method according to claim 3, wherein: The shutter control parameters include an effective exposure time, so that the effective exposure processes of different pixel units partially overlap in the effective exposure time.

5. The image sensor exposure control method according to claim 1, wherein: The pre-reading of the voltage signal of each pixel unit includes: pre-reading the voltage signal of the pixel unit inside the pixel unit.

6. The image sensor exposure control method according to claim 5, wherein: Each pixel unit includes a source follower, a selection transistor, and a lateral overflow integration capacitor; and pre-reading a voltage signal of the pixel unit inside the pixel unit includes: The source follower converts the voltage on the floating diffusion node or the lateral overflow integration capacitor into the voltage signal output by the selection transistor.

7. The image sensor exposure control method according to claim 1, wherein: Determining the current brightness range corresponding to each pixel unit based on the comparison results of the voltage signal of each pixel unit with multiple threshold voltages includes: Acquire multiple threshold voltages arranged from low to high and their corresponding multiple brightness intervals, use a step-by-step comparison or parallel comparison method to determine the threshold voltage level corresponding to the voltage signal of each pixel unit, and determine the corresponding current brightness interval based on the threshold voltage level.

8. The image sensor exposure control method according to claim 1, wherein: The pixel unit includes a photodiode, a transfer transistor, a reset transistor and a lateral overflow integration capacitor; and clearing the charge of each pixel unit includes: The charge in the photodiode is transferred to a floating diffusion node through the transfer transistor, and the charge in the floating diffusion node or the lateral overflow integration capacitor is cleared through the reset transistor.

9. The image sensor exposure control method according to claim 8, wherein: The image sensor further includes a pre-read reset transistor and a pre-read transfer transistor, each of the pre-read reset transistors is coupled to each of the reset transistors in the same row of pixel units, and each of the pre-read transfer transistors is coupled to each of the transfer transistors in the same row of pixel units; The clearing of charges from each pixel unit specifically includes: By controlling the pre-read transfer transistor, each transfer transistor in the same row of pixel units transfers the charge in the photodiode to the floating diffusion node, and by controlling the pre-read reset transistor, each reset transistor in the same row of pixel units clears the charge of the floating diffusion node or the lateral overflow integration capacitor.

10. An image sensor, characterized in that: include: A pixel array comprising a plurality of pixel units; An exposure control logic module is connected to the pixel array and is configured as follows: During a pre-reading period starting from the start of the exposure phase of the current frame image, each pixel unit is controlled to pre-exposure, and at the end of the pre-exposure, a voltage signal of each pixel unit is pre-read, wherein the voltage signal reflects the degree of light response of the current scene brightness to the light of the pixel unit; Determine the current brightness range corresponding to each pixel unit based on the comparison results of the voltage signal of each pixel unit and multiple threshold voltages; allocating a corresponding shutter channel according to the current brightness range of each pixel unit, wherein at least two pixel units having different current brightness ranges are respectively allocated different shutter channels, and shutter control parameters of different shutter channels are different; After the pre-reading time period ends, the charge of each pixel unit is cleared, and in the effective exposure time period, the shutter channel allocated to each pixel unit is scheduled, and the corresponding pixel unit is effectively exposed based on the corresponding shutter control parameters to obtain the current frame image.

11. The image sensor according to claim 10, wherein: The image sensor adopts a stacked chip structure, including a main chip integrating the pixel array and a second chip consisting of the exposure control logic module.

12. The image sensor according to claim 10, wherein: The pixel unit includes a photodiode, a transfer transistor, a reset transistor, and a lateral overflow integration capacitor; the exposure control logic module is further configured to clear the charge of each pixel unit in the following manner: The charge in the photodiode is transferred to a floating diffusion node through the transfer transistor, and the charge in the floating diffusion node or the lateral overflow integration capacitor is cleared through the reset transistor.

13. The image sensor according to claim 12, wherein: The image sensor further includes a pre-read reset transistor and a pre-read transfer transistor, each of the pre-read reset transistors is coupled to each of the reset transistors in the same row of pixel units, and each of the pre-read transfer transistors is coupled to each of the transfer transistors in the same row of pixel units; the exposure control logic module is specifically configured as follows: By controlling the pre-read transfer transistor, each transfer transistor in the same row of pixel units transfers the charge in the photodiode to the floating diffusion node, and by controlling the pre-read reset transistor, each reset transistor in the same row of pixel units clears the charge of the floating diffusion node or the lateral overflow integration capacitor.

Images