Pixel array and image sensor
By increasing the aspect ratio of the edge follower in the pixel array of the image sensor, the signal gain of the edge image is improved, solving the problems of image edge blurring and brightness reduction, and achieving a clearer image edge effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN CHUXING TECH CO LTD
- Filing Date
- 2024-11-26
- Publication Date
- 2026-05-26
AI Technical Summary
In image sensors, the light energy attenuates from the center to the edge of the lens, resulting in less light received by pixels at the edge, and weaker electrical signals, leading to blurred edges or reduced brightness in the image.
Design a pixel array in which the aspect ratio of the edge followers is greater than that of the center followers to enhance the gain effect of the edge followers, thereby improving the sharpness and brightness of the edge image.
By enhancing the gain of the edge follower, the signal strength at the image edges is improved, thereby enhancing the sharpness and brightness of the image edges and resolving the problems of blurred or reduced brightness at the image edges.
Smart Images
Figure CN122093684A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of image sensor technology, and in particular to a pixel array and an image sensor. Background Technology
[0002] Image sensors work by using optical devices to focus external light sources onto a pixel array. The pixel array converts the received light signals into analog electrical signals. These signals are then amplified and denoised, and finally converted into digital signals by an analog-to-digital converter (ADC). Finally, the digital signals are processed by an image processing chip to obtain the final image. However, in practical applications, because the light energy gradually decreases from the center to the edge of the lens, there is a difference in the amount of light received. Pixels at the edge of the lens receive less light and fewer photons, resulting in weaker electrical signals. This causes the image signal at the edges to gradually weaken, potentially leading to blurred edges or reduced brightness. Summary of the Invention
[0003] This application discloses a pixel array and an image sensor to solve the problem that the edges of related image sensors are prone to image blurring or reduced brightness.
[0004] To achieve the above objectives, this application provides the following technical solution:
[0005] In a first aspect, this application provides a pixel array comprising a plurality of pixel units arranged in an array, each pixel unit including a source follower; wherein, each pixel unit includes a central unit and an edge unit, the central unit being located in the center of the pixel array, the edge units surrounding the central unit, the source follower corresponding to the central unit being a central follower, the source follower corresponding to the edge unit being an edge follower, and the aspect ratio of the edge follower being greater than that of the central follower.
[0006] In the pixel array of this application, the aspect ratio of the edge follower is greater than that of the middle follower, which makes the gain effect of the edge follower greater than that of the middle follower. The gain effect of the light signal of the edge follower is higher than that of the middle follower, so that the image signal of the edge follower is gradually enhanced, thereby improving the clarity and brightness of the image edges.
[0007] In some embodiments, the width-to-length ratio of the source follower is the ratio of the gate width W to the channel length L in the source follower.
[0008] Wherein, the width of the gate in the edge follower is greater than the width of the gate in the middle follower, and / or, the length of the channel in the edge follower is less than the length of the channel in the middle follower.
[0009] In some embodiments, the straight-line distance D between the center of the edge unit and the center of the pixel array is positively correlated with the aspect ratio of the corresponding edge follower.
[0010] In some embodiments, the straight-line distance D between the center of the edge unit and the center of the pixel array is greater than or equal to a first preset value.
[0011] In some embodiments, pixel units whose center is at the same vertical distance from the edge of the pixel array form a pixel group, and the source followers in each pixel group have the same aspect ratio.
[0012] In some embodiments, along the width direction of the pixel unit, the distance between the component located on the source follower side and the source follower is greater than or equal to a preset distance.
[0013] In some embodiments, the spacing between the source follower and the edge of the corresponding pixel unit is greater than or equal to 0.025 μm.
[0014] In some embodiments, the width W of the gate in the source follower is less than or equal to 1 / 3 of the width of the pixel unit.
[0015] In some embodiments, the channel length L in the source follower is greater than or equal to 0.06 μm.
[0016] In a second aspect, this application provides an image sensor that includes the image array of the first aspect. Attached Figure Description
[0017] Figure 1 This is a schematic diagram showing the amount of light entering the lens of an existing image sensor;
[0018] Figure 2 A schematic diagram of the brightness of image signals from an existing image sensor;
[0019] Figure 3 This is a schematic diagram of a pixel array structure provided in an embodiment of this application;
[0020] Figure 4 This is a schematic diagram of the structure of a pixel unit provided in an embodiment of this application.
[0021] Icons: 100 - Pixel unit; 101 - Middle unit; 102 - Edge unit; 110 - Source follower; 110a - Middle follower; 110b - Edge follower; 120 - Transmission transistor; 130 - Reset transistor; 140 - Row selector. Detailed Implementation
[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. In the description of the embodiments of this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships, for example, A and / or B can represent: A alone, A and B at the same time, and B alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.
[0023] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.
[0024] Figure 1 This is a schematic diagram illustrating the amount of light entering the lens of an existing image sensor, with reference to... Figure 1 In existing image sensors, the light energy gradually decreases from the center to the edge of the lens, resulting in differences in the amount of light received. Pixels at the edge of the lens receive less light and fewer photons, and the electrical signals they convert are also weaker. Figure 2 A schematic diagram of the brightness of image signals from existing image sensors, such as... Figure 2 As shown, the image signal at the edge of the pixel array in the image sensor gradually weakens, and the brightness of the image edge decreases, which may lead to image blurring.
[0025] In view of this, the present application provides a pixel array, Figure 3 This is a schematic diagram of a pixel array structure provided in an embodiment of this application, with reference to... Figure 3 The pixel array includes multiple pixel units 100 arranged in an array, and each pixel unit 100 includes a source-follower (SF) 110. Each pixel unit 100 includes a central unit 101 and edge units 102. The central unit 101 is located in the center of the pixel array, and the edge units 102 surround the central unit 101. The source-follower corresponding to the central unit 101 is the central follower 110a, and the source-follower corresponding to the edge unit 102 is the edge follower 110b. The aspect ratio of the edge follower 110b is greater than that of the central follower 110a.
[0026] It should be noted that the central unit 101 is located in the center of the pixel array, and the edge unit 102 is located at the edge of the image array. The terms "central" and "edge" are relative. Figure 1 As shown, the nine pixel units 100 in the middle are the central unit 101, and the remaining pixel units 100 are the edge unit 102.
[0027] The center follower 110a may include one, two, or more pixel units 100. The edge follower 110b may include multiple pixel units 100, depending on the actual needs.
[0028] It is understood that this application does not limit the shape of the pixel array; multiple pixel units 100 can form a rectangular array, a triangular array, a hexagonal array, or an irregular array, etc. Among them, the common shape of the pixel array is a rectangular array.
[0029] Understandably, the image signal intensity of pixel unit 100 depends on the intensity of the light signal, i.e., the amount of incident light. When the light intensity increases, the number of photons received by the photodiode increases, and the amount of charge generated also increases, thereby increasing the intensity of the electrical signal output by pixel unit 100. Increasing the electrical signal gain of edge follower 110b can improve the image signal intensity of edge unit 102 of the image sensor. Therefore, to improve the image signal intensity of edge unit 102, the electrical signal gain of edge follower 110b can be increased.
[0030] Among them, g m Transconductance refers to the transconductance of a transistor, which can be understood as the transistor's response to changes in gate voltage; that is, how much change in drain current a small change in gate voltage will cause. The magnitude of transconductance is usually related to the width-to-length ratio (W / L) of the gate structure of a source follower, as follows:
[0031]
[0032] in, It is the change in drain current. The change in gate-to-source voltage, μ n It is electron mobility, C ox It is the gate oxide capacitance per unit area, W is the width of the gate in source follower 110, L is the length of the channel in source follower 110, and V is the gate oxide capacitance per unit area. ds It is the voltage from the gate to the source.
[0033] According to the above formula, when the width-to-length ratio W / L of the gate structure of the source follower 110 located at the edge increases, the transconductance g m It will increase. This is because increasing the W / L ratio increases the channel width of the transistor, which in turn results in a larger change in drain current for the same gate voltage change. In other words, the transistor's amplification capability is enhanced, thereby strengthening the image signal at the edge of the pixel array.
[0034] In one possible implementation, the photon energy value in pixel unit 100 is detected by a specialized instrument, such as a spectrometer. When the photon energy in pixel unit 100 decays to a preset threshold, the aspect ratio of the source follower 110 in the corresponding pixel unit 100 is increased to enhance the intensity of the image signal of the pixel unit 100. The preset threshold is defined according to the application requirements of the image sensor.
[0035] In one possible implementation, the aspect ratio of the source follower 110 is the ratio of the gate width W to the channel length L in the source follower 110. Wherein, the aspect ratio of the edge follower 110b is greater than that of the middle follower 110a, including at least one of the following two cases:
[0036] 1) The width of the gate in the edge follower 110b is greater than the width of the gate in the middle follower 110a;
[0037] 2) The length of the channel in the side follower 110b is less than the length of the channel in the middle follower 110a.
[0038] In the pixel array of this application, the aspect ratio of the edge follower 110b is greater than that of the middle follower 110a. The patterns of the edge follower 110b and the middle follower 110a need to be optically proximity corrected separately. Moreover, the size and shape of the pattern etching area are different, and the etching load effect needs to be overcome.
[0039] In one possible implementation, the straight-line distance D between the center of the edge unit 102 and the center of the pixel array is positively correlated with the aspect ratio of the corresponding edge follower 110b. When the straight-line distance D between the center of the edge unit 102 and the center of the pixel array increases, the aspect ratio of the corresponding edge follower 110b also increases, thereby increasing the electrical signal gain of the edge follower 110b and thus enhancing the image signal of the corresponding pixel unit 100.
[0040] The positive correlation can be linear or nonlinear, depending on the requirements of the image signal from the image sensor.
[0041] In one possible implementation, the straight-line distance D between the center of the edge unit 102 and the center of the pixel array is greater than or equal to a first preset value, wherein the first preset value is set according to the attenuation of photon energy of the edge unit 102 in the pixel array. For example, the first preset value may be 1 / 20, 1 / 15, 1 / 10, or 1 / 5 of the total width or total length of the pixel array.
[0042] Continue to refer to Figure 3 Pixel units 100 whose centers are equidistant from the edges of the pixel array form a pixel group, and the source followers 110 in each pixel group have the same aspect ratio. For example... Figure 3 As shown, multiple source followers 110 connected by each dashed line form a pixel group, and the direction from the center of the pixel array to the edge of the pixel array is such that the aspect ratio of the source followers 110 in each pixel group gradually increases, so that the edge unit 102 in the above image array still has a high image signal.
[0043] In one possible implementation, along the width direction of the pixel unit 100, the distance between the component located on one side of the source follower 110 and the source follower 110 is greater than or equal to a preset distance, so as to avoid interference between the source follower 110 and adjacent components when the width of the gate in the source follower 110 increases. The preset distance is set based on the increase in the width of the gate in the source follower 110 and the safety distance between the source follower 110 and adjacent components.
[0044] In one possible implementation, the distance between the source follower 110 and the edge of the corresponding pixel unit 100 is greater than or equal to 0.025um, so as to prevent the source follower 110 from exceeding the edge of the pixel unit 100 when the width of the gate in the source follower 110 increases, that is, to reserve enough installation space for the source follower 110.
[0045] In one possible implementation, the width W of the gate in the source follower 110 is less than or equal to 1 / 3 of the width of the pixel unit, so as to reserve enough space for adjusting the width W of the gate of the source follower 110.
[0046] In one possible implementation, the channel length L in the source follower 110 is greater than or equal to 0.06 μm.
[0047] Based on the same technical concept, embodiments of this application also provide an image sensor, which includes image arrays in various possible embodiments of this application.
[0048] The image sensors in this application include, but are not limited to, complementary metal-oxide-semiconductor (CMOS) image sensors and charge-coupled device (CCD) image sensors.
[0049] Figure 4 This is a schematic diagram of a pixel unit structure provided in an embodiment of this application, with reference to... Figure 4 The image sensor also includes a transfer tube 120, a reset tube 130, and a row select tube 140. The transfer tube 120 (TX) transmits the charge signal generated by the photodiode to the source follower 110, and is connected to the source follower 110. The reset tube 130 (RST) resets the charge in the pixel unit 100 to zero before each pixel readout, ensuring that the pixel can correctly respond to the light signal during the acquisition of the next frame. The row select tube 140 (RS) controls row selection during the sequential reading of pixel data. When the row select tube 140 is turned on, the pixel data of that row can be read.
[0050] Figure 4 The image sensor shown is a CMOS image sensor. In this image sensor, the transmission tube 120 and the source follower 110 are arranged along the width direction of the pixel unit 100, and the distance between them is greater than or equal to a preset distance to avoid interference between them. For example, the preset distance can be 0.18µm.
[0051] Because of the source follower 110 in various possible embodiments of this application, the image sensor in this application can flexibly set the aspect ratio of the source follower 110 according to the degree of photon energy attenuation in the pixel unit 100, thereby improving the signal gain at the edge of the image and thus improving the problem of the image signal gradually weakening at the edge position of the image sensor.
[0052] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this application without departing from the spirit and scope of this application. Therefore, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application also intends to include these modifications and variations.
Claims
1. A pixel array, characterized in that, It includes multiple pixel units arranged in an array, each pixel unit including a source follower; The pixel unit includes a central unit and an edge unit. The central unit is located in the center of the pixel array, and the edge unit surrounds the central unit. The source follower corresponding to the central unit is a central follower, and the source follower corresponding to the edge unit is an edge follower. The aspect ratio of the edge follower is greater than that of the central follower.
2. The pixel array according to claim 1, characterized in that, The width-to-length ratio of the source follower is the ratio of the gate width W to the channel length L in the source follower. Wherein, the width of the gate in the edge follower is greater than the width of the gate in the middle follower, and / or, the length of the channel in the edge follower is less than the length of the channel in the middle follower.
3. The pixel array according to claim 2, characterized in that, The straight-line distance D between the center of the edge unit and the center of the pixel array is positively correlated with the width-to-length ratio of the corresponding edge follower.
4. The pixel array according to claim 3, characterized in that, The straight-line distance D between the center of the edge unit and the center of the pixel array is greater than or equal to a first preset value.
5. The pixel array according to claim 2, characterized in that, The pixel units whose centers are at the same vertical distance from the edge of the pixel array form a pixel group, and the source follower in each pixel group has the same aspect ratio.
6. The pixel array according to any one of claims 1-5, characterized in that, Along the width direction of the pixel unit, the distance between the component located on one side of the source follower and the source follower is greater than or equal to a preset distance.
7. The pixel array according to claim 6, characterized in that, The distance between the source follower and the edge of the corresponding pixel unit is greater than or equal to 0.025 μm.
8. The pixel array according to claim 6, characterized in that, The width W of the channel in the source follower is less than or equal to 1 / 3 of the width of the pixel unit.
9. The pixel array according to claim 6, characterized in that, The channel length L in the source follower is greater than or equal to 0.06 μm.
10. An image sensor, characterized in that, Includes the pixel array as described in any one of claims 1-9.