Method for improving pixel crosstalk of image sensor under different color temperatures and image sensor

Abstract

The invention discloses a method for improving pixel crosstalk of an image sensor under different color temperatures and the image sensor, and the method is characterized in that a phase difference detection module of the image sensor at least comprises a first phase difference detection pixel and a second phase difference detection pixel which are arranged along a first direction; and the range of crosstalk at the two ends of the phase difference detection module in the first direction along with color temperature change is set to be within a first error range, so that the image quality of the image sensor under different color temperatures is improved, and the cost of processing pixel crosstalk in a digital stage is reduced.

Description

Technical Field

[0001] The present invention relates to the field of image sensors, and in particular to a method for improving pixel crosstalk of image sensors under different color temperatures and an image sensor. Background Art

[0002] With the development of digital imaging technology, users have put forward higher requirements for the focusing speed and accuracy of camera equipment. Although the traditional contrast auto focus (CDAF) method can achieve accurate focusing, it has the problem of slow focusing speed in actual operation because it constantly adjusts the lens position and compares the contrast of the image to find the best focus. In order to improve this situation, phase detection auto focus (PDAF) technology has been introduced into various imaging devices in recent years. The basic principle of PDAF technology is to set specific PDAF pixels on the image sensor and use these pixels to directly measure the phase difference of the incident light, so as to quickly determine the position of the object and focus. Specifically, on the image sensor that supports the PDAF function, some pixels are designed as phase difference detection pixels. When the light reaches these specially designed phase difference detection pixels after passing through the lens, it will be divided into two beams, which are received by two phase difference detection pixels respectively. By comparing the phase difference between the two beams of light, the system can quickly determine the distance of the lens relative to the target object, and adjust the position of the lens accordingly to achieve fast focusing.

[0003] Generally speaking, the filters of the pixels of the image sensor mainly include red (R) filters that allow red light to pass through, green (Gr, Gb) filters that allow green light to pass through, and blue (B) filters that mainly allow blue light to pass through. Sometimes, yellow (Y) filters that allow yellow (Y) light to pass through, transparent filters that allow all visible light to pass through, etc. are also selected. The corresponding pixels are matched with the filters of the corresponding colors to obtain pixels of the corresponding colors. The pixel units containing filters of various colors are repeatedly arranged in the row and column directions with one unit as a period to form a pixel array. Common arrangement patterns, such as Figure 1a In the common pixel array 0 shown, a red pixel 01, a first green pixel 02, a second green pixel 03, and a blue pixel 04 form a Bayer array 1, and the Bayer array 1 is repeatedly arranged in the row direction and the column direction to form a pixel array 0. In order to improve the light-gathering ability of the pixel, a lens 2 is set on each pixel, such as Figure 1b Alternatively, a microlens 2 is set corresponding to a sub-pixel, as shown in Figure 1c shown.

[0004] The currently commonly used PDAF pixel module is usually arranged as follows: the PDAF pixel module includes two different phase difference detection pixels, which are arranged side by side in the row direction and occupy the green pixel and the red pixel in the adjacent Bayer array 1, or occupy the green pixel and the blue pixel in the adjacent Bayer array 1. In order to reduce the difference between the two phase difference detection pixels, the colors used as the phase difference detection pixels are usually set to be the same, such as Figure 2a The PDAF pixel module 4 is shown to include two green pixels, which are composed of a green pixel and a red pixel in the adjacent Bayer array 1. However, such a design usually results in different colors of pixels on both sides of the PDAF pixel module 4, for example, Figure 2a The example shows a PDAF pixel module 4 (2×1 single design, one microlens corresponds to two pixels, set as a group) with green pixels on the left and blue pixels on the right; Figure 2b The example shows a PDAF pixel module (2×1 double design, one microlens corresponds to two pixels, and two groups are set, including the first group 41 and the second group 42) with green pixels on the left and blue pixels on the right. Because the difference in structure between the PDAF pixel module and the ordinary image acquisition pixel will cause the PDAF pixel module to crosstalk to the ordinary image acquisition pixels on both sides, resulting in a significant increase in the response of the image acquisition pixels on both sides. As an example, the difference in structure between the PDAF pixel module and the ordinary image acquisition pixel can be, for example, the difference between the lens of the PDAF pixel module and the microlens 2 of the ordinary image acquisition pixel, the difference between the color filter in the PDAF pixel module not setting a grid and the image acquisition pixel needing to set a grid. In order to solve this problem in the prior art, the aforementioned crosstalk is often corrected at the digital stage. However, the inventors found that when the color temperature changes greatly, the existing digital correction mechanism cannot adapt to the correction under the condition of color temperature change, and the error of the corrected result is large. Sometimes, not only can it not be corrected, but the crosstalk is also made more serious.

[0005] Attach Figure 2b For example, a PDAF pixel module (2×1 double design, one microlens corresponds to two pixels, and two groups are set, including a first group 41 and a second group 42) occupies the positions of four image acquisition pixels, two of which are green and the other two are blue. In order to improve the PDAF pixel module, the positions of the two original blue image acquisition pixels are occupied and uniformly set to green, thereby forming a PDAF pixel module. For the left side of such a PDAF pixel module, since the color of the image acquisition pixel on the left side is the same as the color of the pixel in the PDAF pixel module, under different color temperatures, S PD / S nG It can be kept roughly constant, but the color of the pixel acquired in the right image is different from the color of the pixel in the PDAF pixel module.PD / S nB It cannot always maintain a constant value under different color temperatures and may even vary greatly. In particular, S nB will become smaller, and the crosstalk of the phase difference detection pixel on the right side will increase significantly. The difference in color on both sides will make it more difficult for the algorithm to correct. The definitions are as follows: S PD Represents the response of the PDAF pixel module; S L Represents the response of the image acquisition pixel on the left side of the PDAF pixel module; S R Represents the response of the image acquisition pixel on the right side of the PDAF pixel module; S nX Represents the response of the image acquisition pixel of color X which is not adjacent to the PDAF pixel module, where X can be red, green, blue, etc.; S pdxtL Represents the response caused by crosstalk to the left by the PDAF pixel module; S pdxtR Represents the response caused by crosstalk to the right by the PDAF pixel module; pdxtL represents the crosstalk of the PDAF pixel module to the left; pdxtR represents the crosstalk of the PDAF pixel module to the right.

[0006] Define A as the response S of the PDAF pixel module to a certain crosstalk pdxt and the response S of the PDAF pixel module PD The ratio of the color temperature is uniformly determined to be A at different color temperatures, that is, A on the left and right sides. L , A R is equal to the fixed value.

[0007] (1)

[0008] Attach Figure 2b For example, the response of the image acquisition pixel on the left side of the PDAF pixel module: (2) The response of the image acquisition pixel on the right side of the PDAF pixel module: (3) Crosstalk of PDAF pixel module to the left: (4) Crosstalk of PDAF pixel module to the right: (5) It can be seen that the crosstalk of the PDAF pixel module to the left and right sides has the following relationship with the image acquisition pixels on both sides of the PDAF pixel module: (6) (7) It can be seen that the inventor found that the A corresponding to the left and right sides L , A R When the color temperature is equal, the color of the image acquisition pixels on both sides of the PDAF pixel module is a prominent reason why the image sensor chip cannot adapt to different color temperatures. However, the image sensor chip needs to be applicable to different environments, especially those with large color temperature changes, in order to improve the competitiveness of the image sensor. However, the existing digital processing can generally only process a single color temperature. If the crosstalk caused by the image acquisition pixels of different colors on the side of the PDAF pixel module is corrected for each color temperature, the complexity of the circuit design and the size of the chip will face challenges, resulting in high chip production costs and poor chip imaging quality. Summary of the invention

[0009] Based on the above-described problems, the present invention proposes a method for improving pixel crosstalk of an image sensor at different color temperatures and an image sensor, so as to improve the image quality of the image sensor at different color temperatures and reduce the cost of processing pixel crosstalk at the digital stage.

[0010] In a first aspect, an embodiment of the present invention provides a method for improving pixel crosstalk of an image sensor at different color temperatures, characterized in that the pixel array of the image sensor includes an image acquisition pixel and a phase difference detection module, The phase difference detection module at least includes a first phase difference detection pixel and a second phase difference detection pixel arranged along a first direction, wherein the range in which the crosstalk at both ends of the phase difference detection module in the first direction varies with the color temperature is set within a first error range.

[0011] In a preferred embodiment, the crosstalk at two ends of the phase difference detection module in the first direction is arranged not to vary with the color temperature.

[0012] In a preferred embodiment, the color of the color filters of the first phase difference detection pixel and the second phase difference detection pixel is the same, the color filter color of the image acquisition pixels at both ends of the phase difference detection module adjacent to the first direction is set to be the same as the color filter color of the phase difference detection pixel of the phase difference detection module, or the color filter of the image acquisition pixels at both ends of the phase difference detection module adjacent to the first direction is set to be light-shielding.

[0013] In a preferred embodiment, the color filters of the phase difference detection pixels in the phase difference detection module are all green, or all red, or all blue, or all yellow, or all transparent.

[0014] In a preferred embodiment, the first phase difference detection pixel and the second phase difference detection pixel are covered by the same lens.

[0015] In a preferred embodiment, one of the phase difference detection modules includes one or two groups of first phase difference detection pixels and second phase difference detection pixels covered by the same lens; or, One of the phase difference detection modules includes two first phase difference detection pixels and two second phase difference detection pixels, and the two first phase difference detection pixels and the two second phase difference detection pixels are covered by the same lens.

[0016] In a preferred embodiment, no metal grid is provided between the color filters of the phase difference detection pixels sharing the same lens.

[0017] In a preferred embodiment, the image acquisition pixels in the pixel array include red pixels, blue pixels, first green pixels, and second green pixels, wherein the red pixels, blue pixels, first green pixels, and second green pixels are arranged in a 2×2 manner to form an image acquisition pixel module, and the image acquisition pixel module is repeatedly arranged in the row and column directions in the pixel array.

[0018] In a preferred embodiment, the red pixels and the blue pixels are arranged on a diagonal line of the 2×2 arrangement, and the first green pixels and the second green pixels are arranged on another diagonal line of the 2×2 arrangement.

[0019] In a preferred embodiment, the first green pixel and the second green pixel of the image acquisition pixel module are replaced by the first yellow pixel and the second yellow pixel.

[0020] In a second aspect, the present invention provides an image sensor, which is configured according to the method for improving pixel crosstalk of an image sensor at different color temperatures according to any one of the embodiments described above.

[0021] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: by setting the phase difference detection module of the image sensor to include at least a first phase difference detection pixel and a second phase difference detection pixel arranged along a first direction, and setting the range of crosstalk at both ends of the phase difference detection module in the first direction to be within a first error range as the color temperature changes, the image quality of the image sensor at different color temperatures is improved, and the cost of processing pixel crosstalk in the digital stage is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings of the present invention constitute a part of this specification and are used to further understand the present invention. The drawings illustrate embodiments of the present invention and together with the description are used to explain the principle of the present invention.

[0023] Figure 1a is a schematic diagram of a conventional pixel array.

[0024] Figure 1b A schematic diagram of a Bayer array of an existing pixel array.

[0025] Figure 1c A schematic diagram of a Bayer array of an existing pixel array.

[0026] Figure 2a Schematic diagram of applying a PDAF pixel module to a Bayer array of an existing pixel array.

[0027] Figure 2b Schematic diagram of applying a PDAF pixel module to a Bayer array of an existing pixel array.

[0028] Figure 3a , 4a 5a are schematic diagrams of different design embodiments of the PDAF pixel module in the pixel array of the present invention.

[0029] Figure 3b , 4b 5b are schematic diagrams of different design embodiments of the PDAF pixel module in the pixel array of the present invention. DETAILED DESCRIPTION

[0030] The following detailed descriptions are all illustrative and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention.

[0032] In the first aspect, the key to the method for improving pixel crosstalk of image sensors under different color temperatures proposed by the present invention is to set the range of crosstalk at both ends of the phase difference detection module in the first direction as the range of color temperature changes is within a first error range. Most preferably, the crosstalk at both ends of the phase difference detection module in the first direction is set not to change with color temperature.

[0033] The detailed description is as follows according to the accompanying drawings: Figure 3a~5bAs shown, the Bayer array 1 includes red pixels, first green pixels, second green pixels, and blue pixels to form the Bayer array 1 and are repeatedly arranged in the row direction and the column direction to form the pixel array 0. In order to improve the light-gathering ability of the pixels, a lens 2 is provided on the corresponding pixels (sub-pixels), and each pixel (sub-pixel) formed by the corresponding lens 2 is an image acquisition pixel. In this embodiment, the phase difference detection module (PDAF) is provided to include at least the first phase difference detection pixel and the second phase difference detection pixel arranged along the first direction, and occupy the positions of several original image acquisition pixels, so that the pixel array of the image sensor includes image acquisition pixels and a phase difference detection module.

[0034] like Figure 3a , 4a As shown in 5a, a first preferred embodiment for ensuring that the range of crosstalk variation with color temperature at both ends of the phase difference detection module in the first direction is within the first error range is to set the color filters of the first phase difference detection pixel and the second phase difference detection pixel of the phase difference detection module to be the same, and to set the color filters of the image acquisition pixels at both ends of the adjacent phase difference detection module in the first direction to be the same as the color filters of the phase difference detection pixels of the phase difference detection module.

[0035] The solution of this patent is to change the color of the image acquisition pixels on both sides of the PDAF pixel module in the first direction and make the pixel color in the PDAF pixel module roughly consistent with the color of the image acquisition pixels on both sides of the first direction. PD / S nX It can always be kept consistent or even equal within the first error range, so it is more convenient for the digital module to correct the response of both sides of the PDAF pixel module. Preferably, the pixels in the PDAF pixel module are preferably green, but are not limited to green, and can also be transparent, yellow or other colors.

[0036] like Figure 3b , 4b As shown in 5b, in order to ensure that the range of crosstalk variation with color temperature at both ends of the phase difference detection module in the first direction is within the first error range, the second preferred embodiment is to set the color of the color filters of the first phase difference detection pixel and the second phase difference detection pixel of the phase difference detection module to be the same, and set the color filters of the image acquisition pixels at both ends of the first direction adjacent to the phase difference detection module to be light-shielded. By directly shielding the image acquisition pixels on both sides of the first direction with light-shielding materials, the response of the PDAF pixel module on both sides of the first direction can be kept at 0 at different color temperatures, so that AS PD / S nX is 0, the crosstalk on both sides of the first direction is not affected by the color temperature change, so it can be directly corrected by the digital module. Figure 3b As shown, the image acquisition pixels 51, 52, 53, 54 on both sides of the first group 41 and the second group 42 of the PDAF pixel module are all set to be opaque pixels. Figure 4b As shown, the image acquisition pixels 51, 52 on both sides of the PDAF pixel module 4 are set to be opaque pixels. Figure 5b As shown, a total of 4 image acquisition pixels of the PDAF pixel module 4 are all set as opaque pixels.

[0037] In a preferred embodiment, the first and second preferred embodiments of the phase difference detection module can be implemented separately or simultaneously in a pixel array of an image sensor.

[0038] In a preferred embodiment, if Figure 3a~5b As shown, the first phase difference detection pixel and the second phase difference detection pixel are both covered by the same lens. The first direction is the direction in which the first phase difference detection pixel and the second phase difference detection pixel are arranged side by side.

[0039] In a preferred embodiment, if Figure 3a~4b As shown in the figure, a single phase difference detection module may include one or two groups of first phase difference detection pixels and second phase difference detection pixels covered by the same lens; or Figure 5a~5b As shown, one phase difference detection module includes two first phase difference detection pixels and two second phase difference detection pixels, and the two first phase difference detection pixels and the two second phase difference detection pixels are covered by the same lens.

[0040] In a preferred embodiment, no metal grid is provided between the color filters of the phase difference detection pixels sharing the same lens to increase the amount of incident light.

[0041] Optionally, the color filters of the phase difference detection pixels in the phase difference detection module are all green, or all red, or all blue, or all yellow, or all transparent; among these colors, green is most preferred.

[0042] In the present invention Figure 3a~5b In the embodiment of the example, the image acquisition pixels in the pixel array include red pixels, blue pixels, first green pixels, and second green pixels, wherein the red pixels, blue pixels, first green pixels, and second green pixels are arranged in a 2×2 arrangement. Preferably, the red pixels and blue pixels are arranged on the diagonal lines of the 2×2 arrangement, and the first green pixels and second green pixels are arranged on the other diagonal lines of the 2×2 arrangement. Optionally, the image acquisition pixel module can be repeatedly arranged in a certain number of rows and columns in the pixel array. In other embodiments, the setting positions of the first green pixel and the second green pixel of the aforementioned image acquisition pixel module can also be replaced by the first yellow pixel and the second yellow pixel.

[0043] In a second aspect, the present invention provides an image sensor, which is configured according to the method for improving pixel crosstalk of an image sensor at different color temperatures described in any of the aforementioned embodiments.

[0044] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of the present invention. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and corrections to the present invention. Such modifications, improvements and corrections are suggested in the present invention, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of the present invention.

[0045] It should be understood that the embodiments described in the present invention are only used to illustrate the principles of the embodiments of the present invention. Other variations may also fall within the scope of the present invention. Therefore, as examples and not limitations, alternative configurations of the embodiments of the present invention may be considered consistent with the teachings of the present invention. Accordingly, the embodiments of the present invention are not limited to the embodiments explicitly introduced and described in the present invention.

Claims

1. A method for improving pixel crosstalk of an image sensor at different color temperatures, characterized in that: The pixel array of the image sensor includes image acquisition pixels and a phase difference detection module. The phase difference detection module at least includes a first phase difference detection pixel and a second phase difference detection pixel arranged along a first direction, wherein the range in which the crosstalk at both ends of the phase difference detection module in the first direction varies with the color temperature is set within a first error range.

2. The method according to claim 1, characterized in that The crosstalk at two ends of the phase difference detection module in the first direction is set not to change with the color temperature.

3. The method according to claim 1 or 2, characterized in that: The color of the color filters of the first phase difference detection pixel and the second phase difference detection pixel is the same, the color filter color of the image acquisition pixels at both ends of the phase difference detection module adjacent to the first direction is set to be the same as the color filter color of the phase difference detection pixel of the phase difference detection module, or the color filter of the image acquisition pixels at both ends of the phase difference detection module adjacent to the first direction is set to shield light.

4. The method according to claim 1, characterized in that: The color filters of the phase difference detection pixels in the phase difference detection module are all green, or all red, or all blue, or all yellow, or all transparent.

5. The method according to claim 1, characterized in that The first phase difference detection pixel and the second phase difference detection pixel are covered by the same lens.

6. The method according to claim 5, characterized in that One of the phase difference detection modules includes one or two groups of first phase difference detection pixels and second phase difference detection pixels covered by the same lens; or, One of the phase difference detection modules includes two first phase difference detection pixels and two second phase difference detection pixels, and the two first phase difference detection pixels and the two second phase difference detection pixels are covered by the same lens.

7. The method according to claim 6, characterized in that No metal grid is provided between the color filters of the phase difference detection pixels sharing the same lens.

8. The method according to claim 3, characterized in that The image acquisition pixels in the pixel array include red pixels, blue pixels, first green pixels, and second green pixels, wherein the red pixels, blue pixels, first green pixels, and second green pixels are arranged in a 2×2 manner to form an image acquisition pixel module, and the image acquisition pixel module is repeatedly arranged in the row and column directions in the pixel array.

9. The method according to claim 8, characterized in that The red pixel and the blue pixel are arranged on a diagonal line of the 2×2 arrangement, and the first green pixel and the second green pixel are arranged on another diagonal line of the 2×2 arrangement.

10. The method according to claim 8 or 9, characterized in that: The first green pixel and the second green pixel of the image acquisition pixel module are replaced by the first yellow pixel and the second yellow pixel.

11. An image sensor, characterized in that: The method for improving pixel crosstalk of an image sensor at different color temperatures is provided according to any one of claims 1 to 10.

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