An image sensor based on a backside illumination process

Abstract

The application provides a back-illumination process-based image sensor, comprising a pixel array, an analog processing circuit, a digital processing circuit and a frame buffer circuit; the analog processing circuit is connected with the pixel array and is used for quantizing and reading a pixel signal of the pixel unit after row exposure to obtain a row quantization signal; the frame buffer circuit is connected with the analog processing circuit and is used for buffering the row quantization signal into a row buffer signal; and the digital processing circuit is connected with the frame buffer circuit and is used for processing the row buffer signal. The back-illumination process-based image sensor provided by the application can improve the quantization speed of the analog processing circuit by adding the frame buffer circuit to temporarily buffer the signal quantized by the analog processing circuit row by row, thereby greatly shortening the quantization window of the whole frame image, realizing high frame rate quantization and achieving an image effect similar to a global shutter.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of imaging technology, in particular to an image sensor based on a back-illumination process. BACKGROUND

[0002] An image sensor is a functional device that converts a light image on a photosensitive surface into an electrical signal in a corresponding proportional relationship by using the photoelectric conversion function of a photoelectric device. Compared with a photosensitive diode, a photosensitive triode, and other "point" light-sensitive elements, an image sensor divides a light image on its light-receiving surface into many small units and converts them into usable electrical signals. The current exposure mode of an image sensor includes a rolling shutter and a global shutter, and the image sensor has gradually developed into a device with small size, light weight, high integration, high resolution, low power consumption, long service life, and low price, and has been widely used in various industries.

[0003] During the conception and implementation of the present application, the inventors found that at least the following problems exist: a rolling shutter image sensor uses a row-by-row exposure quantization reading mode for image signal processing of a frame, which limits the frame rate of the rolling shutter image sensor to the cycle waiting time of row quantization and row data processing, that is, the time for analog circuit quantization of pixel signals and the time for digital circuit processing of read-out signals do not match, which limits the quantization frame rate of the rolling shutter image sensor; in addition, the row-by-row exposure quantization of the rolling shutter image sensor also causes image tailing when shooting moving objects due to the difference in exposure time between rows.

[0004] The foregoing narrative is intended to provide general background information and does not necessarily constitute the prior art. SUMMARY

[0005] To alleviate the above problems, the present application provides an image sensor based on a back-illumination process, specifically comprising: a pixel array, an analog processing circuit, a digital processing circuit, and a frame buffer circuit;

[0006] The analog processing circuit is connected to the pixel array and is configured to quantize and read the pixel signals after row-by-row exposure of the pixel units to obtain row quantization signals;

[0007] The frame buffer circuit is connected to the analog processing circuit and is configured to buffer the row quantization signals row by row into row buffer signals;

[0008] The digital processing circuit is connected to the frame buffer circuit and is configured to process the row buffer signals.

[0009] Optionally, the analog processing circuit in the image sensor comprises a row driving unit and a quantization unit connected to each other, the row driving unit is configured to drive the photosensitive voltage of each row of pixels to the quantization unit, so that the quantization unit quantizes and reads the photosensitive voltage.

[0010] Optionally, the pixel array arranged in rows and columns in the image sensor is arranged at the center of the silicon wafer, and the analog processing circuit, the digital processing circuit and the frame buffer circuit are arranged at the side of the pixel array.

[0011] Optionally, the analog processing circuit in the image sensor is arranged adjacent to at least two adjacent sides of the pixel array on the silicon wafer.

[0012] Optionally, the frame buffer circuit in the image sensor is arranged adjacent to at least one side of the analog processing circuit on the silicon wafer.

[0013] Optionally, the frame buffer circuit in the image sensor is arranged adjacent to at least one side of the digital processing circuit on the silicon wafer.

[0014] Optionally, the digital processing circuit in the image sensor is arranged adjacent to at least one side of the analog processing circuit on the silicon wafer.

[0015] And / or, at least one side of the digital processing circuit is arranged at the edge of the silicon wafer.

[0016] Optionally, the analog processing circuit in the image sensor is arranged adjacent to three adjacent sides of the pixel array, the three adjacent sides include two opposite column selection sides and one row selection side.

[0017] Optionally, in the image sensor, the area of the frame buffer circuit is greater than the area of the analog processing circuit on the silicon wafer, and the area of the frame buffer circuit is greater than the area of the digital processing circuit.

[0018] Optionally, the frame buffer circuit in the image sensor buffers the row quantization signals of a frame of image into row buffer signals of a frame of image row by row to obtain and send frame buffer signals to the digital processing circuit.

[0019] And / or, the frame buffer circuit buffers the row quantization signals of a frame of image into a plurality of row buffer signals row by row to obtain and send each row buffer signal to the digital processing circuit respectively.

[0020] As described above, the image sensor based on the back-illumination process provided by the present application can increase the speed of quantization of the analog processing circuit by adding a frame buffer circuit for temporarily buffering the signals quantized by the analog processing circuit row by row, without affecting the time for the digital processing circuit to process the signals, thereby greatly shortening the quantization window of the whole frame image, realizing high frame rate quantization, and achieving an image effect similar to that of a global shutter. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced as follows. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0022] Figure 1 Structure diagram of the image sensor based on the back-illumination process according to an embodiment of the present application Figure One .

[0023] Figure 2 Structure diagram of the image sensor based on the back-illumination process according to an embodiment of the present application Figure Two .

[0024] Figure 3 Structure diagram of the image sensor based on the back-illumination process according to an embodiment of the present application Figure Three .

[0025] Figure 4 Timing diagram of the frame buffer circuit and the digital processing circuit according to an embodiment of the present application Figure One .

[0026] Figure 5 Timing diagram of the frame buffer circuit and the digital processing circuit according to an embodiment of the present application Figure Two .

[0027] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. The above-described drawings have shown the specific embodiments of the present application, and more detailed descriptions will be given hereinafter. These drawings and textual descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0028] The exemplary embodiments will be described in detail herein with reference to the attached drawings. The description herein relates to the drawings, in which the same numbers represent the same or similar elements, throughout the several views. The following exemplary embodiments are described in order to provide a thorough understanding into the present application. It is understood that the application is not limited to the embodiments described herein, but can be practiced with modifications and changes within the scope and spirit of the present application, as described in the accompanying claims.

[0029] It should be noted that, as used herein, the terms "includes," "including," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements is not limited to only those elements, but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without limitation, an element preceded by "comprises a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. Also, any reference to claim elements in the singular, for example, a reference to "a" element, does not exclude the existence of additional such elements in the process, method, article, or apparatus. The use of zero, one, or more of an element or limit thereof does not exclude the existence of additional such elements or limits in the process, method, article, or apparatus.

[0030] It should be understood that the specific embodiments described herein are merely exemplary and do not limit the application.

[0031] In one aspect, the present application provides a backside-illumination process based image sensor. Figure 1 Structure of a backside-illumination process based image sensor according to an embodiment of the present application Figure One .

[0032] Referring to Figure 1 In one embodiment, the image sensor comprises a pixel array 10, an analog processing circuit 20, a digital processing circuit 30, and a frame buffer circuit 40.

[0033] The analog processing circuit 20 is connected to the pixel array 10, and is configured to quantize and read the pixel signals of the pixel units after each row is exposed, to obtain a row quantization signal. The frame buffer circuit 40 is connected to the analog processing circuit 20, and is configured to buffer the row quantization signal row by row as a row buffer signal. The digital processing circuit 30 is connected to the frame buffer circuit 40, and is configured to process the row buffer signal.

[0034] Exemplarily, the frame buffer circuit 40 is a buffer circuit for realizing frame buffering, and can buffer the image signal quantized by the analog processing circuit 20, and read and process the image signal at any time when the digital processing circuit 30 is idle. The addition of the frame buffer circuit 40 can enable the analog processing circuit 20 to quickly quantize the pixel signals of the whole frame row by row, regardless of the time required by the digital processing circuit 30 to process the quantized data, thereby shortening the quantization window time and improving the image processing speed of the image sensor.

[0035] By adding the frame buffer circuit 40 for temporarily buffering the signals quantized by the analog processing circuit 20 row by row, the quantization speed of the analog processing circuit 20 can be improved, the time for the digital processing circuit 30 to process the signals is not affected, and the quantization window of the whole frame image is greatly shortened, high frame rate quantization is realized, and an image effect similar to global shutter is achieved.

[0036] In an embodiment, the analog processing circuit 20 in the image sensor includes a row driving unit and a quantization unit connected to each other, and the row driving unit is configured to drive and output the photosensitive voltage of each row of pixels to the quantization unit, so that the quantization unit quantizes and reads the photosensitive voltage.

[0037] The analog processing circuit 20 is responsible for amplifying, denoising, quantizing, etc. the voltage signal of the pixel exposed row by row. Exemplarily, the row driving unit can transfer the charge sensed by the pixel through amplification, drive and output the photosensitive voltage, and the quantization unit further quantizes and reads the photosensitive voltage to form quantized photosensitive data corresponding to the charge of the pixel.

[0038] Figure 2 Structure diagram of the image sensor based on the back-illumination process in an embodiment of the present application Figure Two .

[0039] Please refer to Figure 2 In an embodiment, the pixel array 10 arranged in rows and columns in the image sensor is arranged in a rectangular shape at the center of the silicon wafer, and the analog processing circuit 20, the digital processing circuit 30 and the frame buffer circuit 40 are arranged at the side of the pixel array 10.

[0040] The pixel array 10 can be arranged in a rectangular array on the silicon wafer in rows and columns as a photosensitive window of the image sensor. The pixel array 10 is arranged at the center of the silicon wafer to collect light towards the direction needing to be sensed. The central position of the silicon wafer is convenient for process manufacturing and can completely and comprehensively sense the light focused by the lens.

[0041] The analog processing circuit 20, the digital processing circuit 30 and the frame buffer circuit 40 are arranged at the side of the pixel array 10 and can be connected by metal lines in the silicon wafer. The frame rate per second in the silicon wafer can reach about 100 FPS.

[0042] Please continue to refer to Figure 2In an embodiment, the analog processing circuit 20 in the image sensor is placed on the silicon die such that it has at least one contiguous side with the pixel array 10.

[0043] The analog processing circuit 20 processes the pixel charge by reading out at least one column of corresponding pixels from the column select side of the pixel array 10 for each row of pixels in the pixel array 10 that is opened by the row select signal input to the row select side of the pixel array 10. Figure 2 In the embodiment shown, the analog processing circuit 20 has two contiguous sides with the pixel array 10.

[0044] Please continue to refer to Figure 2 In an embodiment, the frame buffer circuit 40 in the image sensor is placed on the silicon die such that it has at least one contiguous side with the analog processing circuit 20.

[0045] The analog processing circuit 20 needs to send the row-quantized image signal to the frame buffer circuit 40 for temporary storage. The analog processing circuit 20 and the frame buffer circuit 40 are placed adjacently, which can be directly connected by the on-die metal interconnect, shortens the connection distance, and speeds up the information transmission and processing speed. Figure 2 In the embodiment shown, the frame buffer circuit 40 has two contiguous sides with the analog processing circuit 20.

[0046] Please continue to refer to Figure 2 In an embodiment, the digital processing circuit 30 in the image sensor is placed on the silicon die such that it has at least one contiguous side with the frame buffer circuit 40.

[0047] The digital processing circuit 30 can read the buffered quantized signal from the frame buffer circuit 40 for processing. The digital processing circuit 30 and the frame buffer circuit 40 are placed adjacently, which can be directly connected by the on-die metal interconnect, shortens the connection distance, and speeds up the information transmission and processing speed. Figure 2 In the embodiment shown, the digital processing circuit 30 has two contiguous sides.

[0048] Please continue to refer to Figure 2 In an embodiment, the digital processing circuit 30 in the image sensor is placed on the silicon die such that it has at least one contiguous side with the analog processing circuit 20.

[0049] Since the digital processing circuit 30 needs to convert the pre-exposure row address digital signal, the sampling row address digital signal, the pre-exposure row transmission digital signal and the sampling row transmission digital signal into the pre-exposure row address analog signal, the sampling row address analog signal, the pre-exposure row transmission analog signal and the sampling row transmission analog signal, and output the transmission control signal that can control the gate of the transmission transistor in the pixel circuit based on the above-mentioned analog signals and the latched address analog signal to select each row of pixels, the digital processing circuit 30 is arranged adjacent to the analog processing circuit 20, and is directly connected through the on-chip metal interconnection line, so that the connection distance can be shortened to provide high-speed information transmission and processing on the chip.

[0050] Optionally, at least one side of the digital processing circuit 30 is arranged at the edge of the silicon wafer.

[0051] Since the digital processing circuit 30 needs to output the processed pixel signal through the data interface, the parallel output or the serial output data can be selected based on the requirement, and therefore the digital processing circuit 30 is arranged at the edge of the silicon wafer to facilitate the arrangement of the data interface.

[0052] Figure 3 It is shown in the middle that the digital processing circuit 30 and the analog processing circuit 20 are arranged on the silicon wafer with an adjacent side, and one side is arranged at the edge of the silicon wafer.

[0053] Figure Three Structure diagram of the back-illuminated image sensor of an embodiment of the present application Figure 3 .

[0054] Please refer to Figure 2 In an embodiment, the analog processing circuit 20 in the image sensor is arranged adjacent to three adjacent sides of the pixel array 10, including two opposite column selection sides and one row selection side.

[0055] When the analog processing circuit 20 is directly connected or wired connected to the two opposite column selection sides of the pixel array 10, the analog processing circuit 20 can simultaneously quantize and read two columns of pixel signals through one row selection signal, and can realize multi-row simultaneous readout and speed up quantization.

[0056] Please refer to Figure 3 and Figure 4 In an embodiment, on the silicon wafer, the area of the frame buffer circuit 40 is greater than the area of the analog processing circuit 20, and the area of the frame buffer circuit 40 is greater than the area of the digital processing circuit 30.

[0057] The larger the area of the frame buffer circuit 40 is, the more quantized data can be buffered, so that the analog processing circuit 20 and the digital processing circuit 30 are released from the restriction caused by the difference in signal processing speed, and the image processing speed of the image sensor is greatly improved.

[0058] Figure One Timing diagram of frame buffer circuit and digital processing circuit for an embodiment of the present application Figure 4 .

[0059] Optionally, the frame buffer circuit 40 in the image sensor buffers the row quantized signals of a frame of image into row buffered signals of a frame of image, and sends the frame buffered signals to the digital processing circuit 30.

[0060] Please refer to Figure 5 In an exemplary embodiment, the frame buffer circuit 40 buffers a complete frame of image, and the digital processing circuit 30 reads and processes the frame of image information as a whole.

[0061] Figure Two Timing diagram of frame buffer circuit and digital processing circuit for an embodiment of the present application Figure 5 .

[0062] Optionally, the frame buffer circuit 40 buffers the row quantized signals of a frame of image into multiple row buffered signals, and sends each row buffered signal to the digital processing circuit 30. In this way, the digital processing circuit 30 can read frame by frame.

[0063] Please refer to ​ In an exemplary embodiment, the frame buffer circuit 40 buffers a row of image signals at a time, and the digital processing circuit 30 reads and processes a row of image signals at a time. In this way, the image signals are read row by row, and the frame buffer circuit 40 and the digital processing circuit 30 can process synchronously.

[0064] As described above, the image sensor based on back-illumination process provided by the present application can increase the speed of quantization of the analog processing circuit by adding the frame buffer circuit for temporarily buffering the signals quantized by the analog processing circuit row by row, without affecting the time for processing the signals by the digital processing circuit, thereby greatly shortening the quantization window of the whole frame of image, realizing high frame rate quantization, achieving the image effect similar to global shutter, and having the advantages of simple circuit design and small noise.

[0065] In the embodiments of the intelligent terminal and the computer readable storage medium provided by the present application, all the technical features of any of the above method embodiments can be included, and the description and explanation contents are basically the same as those of the above method embodiments, which will not be repeated here.

[0066] The embodiments of the present application also provide a computer program product, which includes computer program code, when the computer program code runs on a computer, so that the computer executes the method in various possible embodiments as above.

[0067] The embodiment of the present application further provides a chip comprising a memory and a processor, the memory is used for storing a computer program, and the processor is used for calling and running the computer program from the memory, so that the device installed with the chip executes the method in the various possible embodiments.

[0068] It can be understood that the above scenarios are only examples and do not constitute a limitation on the application scenarios of the technical solutions provided by the embodiments of the present application. The technical solutions provided by the present application are also applicable to other scenarios. For example, those skilled in the art can know that, with the evolution of system architecture and the emergence of new business scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0069] The serial numbers of the above embodiments of the present application are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0070] The steps in the method of the embodiments of the present application can be adjusted in sequence, combined and deleted according to actual needs.

[0071] The units in the device of the embodiments of the present application can be combined, divided and deleted according to actual needs.

[0072] In the present application, for the same or similar term concept, technical solution and / or application scenario description, generally only the first time is described in detail, and for the sake of brevity, the repeated description is not repeated, and for the understanding of the technical solutions of the present application, the same or similar term concept, technical solution and / or application scenario description which is not described in detail can be referred to the previous related description.

[0073] In the present application, the description of each embodiment has its own emphasis, and the part not described or recorded in a certain embodiment can be referred to the related description of other embodiments.

[0074] The technical features of the technical solutions of the present application can be combined arbitrarily, in order to make the description simple, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combination of these technical features does not exist contradictory, it should be considered as the scope recorded in the present application.

[0075] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, any equivalent structure or equivalent process transformation using the content of the present application specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An image sensor based on back-illuminated technology, characterized in that, include: Pixel array, analog processing circuit, digital processing circuit, and frame buffer circuit; The analog processing circuit is connected to the pixel array and is used to quantize and read the pixel signal after the pixel unit is exposed line by line to obtain the line quantization signal. The frame buffer circuit is connected to the analog processing circuit and is used to buffer the line quantization signal line by line into a line buffer signal. The digital processing circuit is connected to the frame buffer circuit and is used to process the line buffer signal; The pixel array rectangle, organized into rows and columns, is located at the center of the silicon wafer, while the analog processing circuit, digital processing circuit, and frame buffer circuit are located on the sides of the pixel array. The analog processing circuit is disposed adjacent to at least two adjacent sides of the pixel array on the silicon wafer; And / or, the digital processing circuit and the analog processing circuit are disposed on the silicon wafer having at least one adjacent side; And / or, at least one side of the digital processing circuit is disposed at the edge of the silicon wafer; And / or, on the silicon wafer, the area of ​​the frame buffer circuit is larger than the area of ​​the analog processing circuit, and the area of ​​the frame buffer circuit is larger than the area of ​​the digital processing circuit.

2. The image sensor as described in claim 1, characterized in that, The analog processing circuit includes a row driving unit and a quantization unit connected to each other. The row driving unit is used to drive the photosensitive voltage of each row of pixels to the quantization unit so that the quantization unit can quantize and read the photosensitive voltage.

3. The image sensor as described in claim 1, characterized in that, The frame buffer circuit and the analog processing circuit are disposed on the silicon wafer with at least one adjacent side.

4. The image sensor as described in claim 3, characterized in that, The digital processing circuit and the frame buffer circuit are disposed on the silicon wafer with at least one adjacent side.

5. The image sensor as described in claim 1, characterized in that, The analog processing circuit is disposed adjacent to three adjacent sides of the pixel array, the three adjacent sides including two opposite column selection sides and one row selection side.

6. The image sensor according to any one of claims 1-5, characterized in that, The frame buffer circuit buffers the line quantization signal of a frame of image line by line into a line buffer signal of a frame of image, and obtains and sends the frame buffer signal to the digital processing circuit. And / or, the frame buffer circuit buffers the line quantization signal of a frame of image line by line into multiple line buffer signals, so as to obtain and send each line buffer signal to the digital processing circuit respectively.

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