Image sensor and method for reducing crosstalk amount

Abstract

The invention provides an image sensor and a crosstalk amount reducing method thereof, the image sensor comprises a pixel array structure, and the pixel array structure is an array composed of a plurality of pixels; a photoelectric conversion structure; the color filter array comprises at least two color filter units with different colors, the color filter units with different pigments correspond to different spectrum channels, one color filter unit corresponds to at least two spectrum channels with different light sensitivities, and the other color filter unit corresponds to at least two spectrum channels with different light sensitivities. The color filter array is located in the light incidence direction of the pixel array structure, the pixel array structure is located between the photoelectric conversion structure and the color filter array and is connected with the photoelectric conversion structure, and the color filter array is located in the light incidence direction of the pixel array structure. Wherein after photoelectric signal conversion is completed, photoelectric signals, close to purity, of the pixels are obtained through operation.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to an image sensor and a method for reducing crosstalk. Background Art

[0002] For a long time, image sensors, whether based on CIS or CCD, have struggled to achieve a perfect balance between infrared and visible light imaging. Some surveillance cameras, which require continuous operation day and night, use visible light imaging during the day and near-infrared imaging at night. These cameras' sensors often employ an RGBIR color arrangement, distinct from the traditional Bayer array, using the RGB portion during the day and the IR portion at night. Other specialized applications, such as facial recognition, palm print recognition, and object material identification, also require simultaneous color and infrared imaging.

[0003] like Figure 1 The RGBIR color arrangement shown, or the arrangement of several visible light channels plus an IR channel, both have unavoidable crosstalk problems. That is, the visible light signals of the RGB channels can enter the IR channel through reflection, refraction, scattering on the pixel surface or inside, as well as electrical signal leakage between pixels. As a result, the signal output by the IR channel is not equal to the true signal generated by the actual IR light incident, causing imaging distortion.

[0004] Currently, methods such as BSI architecture, adding metal grids, adding deep trench isolation (DTI), and reducing the thickness of each layer on the pixel surface to shorten the optical path are commonly used to reduce the impact of crosstalk on the IR channel. However, none of these methods can completely avoid crosstalk, or very complex calculations are required to reduce the crosstalk signal. Summary of the Invention

[0005] A major advantage of the present invention is that it provides an image sensor and a method for reducing crosstalk, wherein one of the two spaced-apart channels of the image sensor in the same wavelength band has a photosensitivity x times that of the other, and a nearly pure signal can be obtained through calculation after photoelectric conversion, which is beneficial to reducing crosstalk signals.

[0006] Another advantage of the present invention is that it provides an image sensor and a method for reducing crosstalk, wherein the IR pixel in the image sensor is a normal infrared pixel, and the xIR pixel is an infrared pixel with a sensitivity set to x times that of the IR pixel. When exposed to the same infrared light, without considering crosstalk, the signal output by the xIR pixel is x times the signal of the IR pixel. It can be considered that the signal of each other pixel around the IR pixel is consistent with the signal of each other responsive pixel around the xIR pixel, so the sum of the crosstalk signals received by the surrounding pixels IR and xIR is approximately consistent.

[0007] Another advantage of the present invention is to provide an image sensor and a method for reducing crosstalk, wherein the image sensor performs calculations so that the light intensity signals output by two pixels with different sensitivities have the same level, and does not output signals with different brightness due to differences in sensitivity.

[0008] Another advantage of the present invention is to provide an image sensor and a method for reducing crosstalk, wherein the image sensor is not only applicable to RGBIR but also applicable to image sensors with more than 4 channels (such as 9 channels or 16 channels).

[0009] Another advantage of the present invention is to provide an image sensor and a method for reducing crosstalk, wherein the image sensor has different openings at different positions, for example, there may be no obstruction, partial obstruction, and openings of different sizes in the partial obstruction.

[0010] Another advantage of the present invention is to provide an image sensor and a method for reducing crosstalk, wherein the image sensor can perform the above-mentioned design on the channels corresponding to the required bands according to design requirements, such as the R channel, the B channel, and the channels of other bands.

[0011] Another advantage of the present invention is that it provides an image sensor and a method for reducing crosstalk, wherein the image sensor can adjust the sensitivity of the pixel to x times that of a normal pixel by simply changing the blocking area of the metal grid on the surface of the xIR pixel to block part of the incident light without changing the stacking relationship of the above-mentioned structure, thereby reducing the manufacturing difficulty.

[0012] Another advantage of the present invention is to provide an image sensor and a method for reducing crosstalk, wherein the image sensor only requires additional metal interconnect wires to achieve partial shading of xIR pixels to obtain x times the sensitivity of the responsiveness, reducing the manufacturing difficulty.

[0013] Another advantage of the present invention is to provide an image sensor and a method for reducing crosstalk, wherein the image sensor manufacturing process and procedure do not need to be modified and there is no additional cost.

[0014] According to one aspect of the present invention, a color filter array of the present invention that can achieve the aforementioned objects and other objects and advantages includes:

[0015] At least two color filter units with different colors, the color filter units of different colorants correspond to different spectral channels, wherein there is a color filter unit corresponding to at least two spectral channels with different photosensitivity, the color filter units of the color filter array include a first sub-color filter unit and a second sub-color filter unit, wherein the first sub-color filter unit and the second sub-color filter unit have the same color, the first sub-color filter unit and the second sub-color filter unit are arranged at intervals, and the photosensitivity of the first sub-color filter unit corresponding to the spectral channel is x times the photosensitivity of the second sub-color filter unit corresponding to the spectral channel, and x≠1.

[0016] According to an embodiment of the present application, the color filter unit includes a red color filter unit, a green color filter unit, a blue color filter unit, and an infrared color filter unit.

[0017] According to an embodiment of the present application, the first sub-color filter unit of the color filter unit corresponds to a normal IR channel with a photosensitivity of 1, and the second sub-color filter unit corresponds to a proportional IR channel with a photosensitivity of x.

[0018] According to another aspect of the present application, the present application further provides an image sensor, comprising:

[0019] A pixel array structure, wherein the pixel array structure is an array composed of a plurality of pixels;

[0020] a photoelectric conversion structure; and

[0021] A color filter array as described above, wherein the color filter array is located in the light incident direction of the pixel array structure, the pixel array structure is located between the photoelectric conversion structure and the color filter array and is connected to the photoelectric conversion structure, wherein after the photoelectric signal conversion is completed, a nearly pure photoelectric signal of the pixel is obtained through calculation.

[0022] According to an embodiment of the present application, the pixel array structure includes an R channel, a G channel, a B channel, and an IR channel.

[0023] According to one embodiment of the present application, IR is a normal infrared pixel, and xIR is a proportional infrared pixel with a sensitivity set to x times that of the IR pixel. When exposed to the same infrared light, without considering crosstalk, the signal output by the xIR pixel is x times the signal of the IR pixel. The R, G, B or other channels around each IR channel and the xIR channel are arranged in the same manner. At the scale of the spaced IR pixels and xIR pixels, the signal of each other pixel around the IR channel is consistent with the signal of each other responsive pixel around the xIR channel.

[0024] According to one embodiment of the present application, when the sensitivity of xIR is x times that of IR, then:

[0025] S IR =x·S xIR (4)

[0026] Formula (2)-(3) gives

[0027]

[0028]

[0029] Where DN is the readout signal value output by a single pixel. In equations (5) and (6), the crosstalk signal is directly eliminated through simple arithmetic operations, thereby obtaining a pure IR channel signal.

[0030] According to an embodiment of the present application, x is 0.5, and the true signal values without crosstalk of IR and xIR are obtained as follows:

[0031] S IR =2·(DN IR -DN xIR )

[0032] S xIR =DN IR -DN xIR

[0033] After x times the scaling operation, the complete output image signal can be obtained.

[0034] According to one embodiment of the present application, when calculating the true crosstalk-free signal of a certain IR / xIR pixel, the signal is calculated with the average of the signals of four IR / xIR pixels arranged at intervals, where x is 0.5, and the result is:

[0035]

[0036]

[0037] The real infrared light signal value is obtained by multiplying (9) and (10) by x times the scale.

[0038] According to one embodiment of the present application, the pixel array structure includes a passivation layer and a metal gate, wherein the passivation layer and the metal gate are located above the photoelectric conversion structure, and the shading area of the metal gate on the surface of the proportional pixel is larger than the shading area on the surface of the normal pixel, so as to adjust the sensitivity of the proportional pixel to x times that of the normal pixel.

[0039] According to one embodiment of the present application, the metal gate includes a spacing unit and a blocking unit, wherein the spacing unit is arranged between the PDs of two adjacent normal pixels to space the incident light entering the two adjacent pixels, and the blocking unit is arranged above the PD corresponding to the proportional pixel to reduce the amount of incident light entering the pixel.

[0040] According to one embodiment of the present application, the pixel array includes a passivation layer and a metal interconnection structure formed on the passivation layer, the metal interconnection structure includes a spacer segment and a blocking segment, wherein the spacer segment is arranged between the photodiodes of two adjacent normal pixels, and the blocking segment is arranged above the corresponding photodiode of the proportional pixel to block part of the incident light entering the photodiode.

[0041] According to one embodiment of the present application, it further includes a microlens array, wherein the microlens array is located above the color filter array, wherein the incident light enters the color filter array through the microlens array, and the microlens array is used to optimize the stacking structure of the light path.

[0042] According to one embodiment of the present application, a calculation module is further included, wherein the calculation module is electrically connected to the photoelectric conversion structure, and the electrical signal converted by the photoelectric conversion structure is output as an image after passing through the calculation module.

[0043] According to another aspect of the present application, the present application further provides a method for reducing the crosstalk amount of a color image sensor, wherein the method for reducing the crosstalk amount of a color image sensor comprises the following steps:

[0044] (a) setting the photosensitivity of the spectral channels corresponding to at least one wavelength band according to a specific ratio, wherein the photosensitivity of one of the two alternately arranged spectral channels corresponding to the wavelength band is set to x times the photosensitivity of the other, where x≠1; and

[0045] (b) After the photoelectric signal conversion is completed, a nearly pure photoelectric signal of the pixel is obtained through calculation.

[0046] According to one embodiment of the present invention, the color image sensor is a color image sensor with IR, wherein the spectral channel can be an R channel, a G channel, a B channel or an IR channel, and the pixels corresponding to the band include normal pixels and geometric pixels, and the normal pixels and the geometric pixels are arranged at intervals, wherein the spectral channel corresponding to the normal pixels is the normal channel, and the spectral channel corresponding to the geometric pixels is the geometric channel, wherein the photosensitivity of the geometric channel is x times the photosensitivity of the normal channel, where x≠1.

[0047] According to one embodiment of the present invention, the photosensitivity corresponding to two IR channels arranged at intervals is set according to a specific ratio, where IR is a normal infrared pixel and xIR is a proportional infrared pixel with the sensitivity set to x times that of the IR pixel.

[0048] According to one embodiment of the present invention, in step (b) of the method for reducing the amount of crosstalk,

[0049]

[0050] Where CTK is the amount of crosstalk signal received by a pixel, and the signal composition of each IR channel is:

[0051] DN IR =S IR +CTK IR (2)

[0052] DN xIR =S xIR +CTK xIR (3)

[0053] Where DN is the readout signal value output by a single pixel, which includes the sum of the real signal without crosstalk and the crosstalk signal. S is the real signal value without crosstalk generated by the pixel after being irradiated with light.

[0054] According to one embodiment of the present invention, when the sensitivity of xIR is x times that of IR, we have:

[0055] S IR =x·S xIR (4)

[0056] Formula (2)-(3) gives

[0057]

[0058]

[0059] In equations (5) and (6), the crosstalk signal is directly eliminated through simple arithmetic operations, thereby obtaining a pure IR channel signal.

[0060] According to one embodiment of the present invention, x is designed to be 0.5. Then, as a preferred embodiment of the present application, the true signal values without crosstalk of IR and xIR can be obtained as follows:

[0061] S IR =2·(DN IR -DN xIR )

[0062] S xIR=DN IR -DN xIR

[0063] After x times the scaling operation, the complete output image signal can be obtained.

[0064] According to one embodiment of the present invention, when calculating a certain IR / xIR crosstalk-free real signal, it is calculated with the average value of the signals of four IR pixels and xIR pixels arranged at intervals, that is:

[0065]

[0066]

[0067] According to one embodiment of the present invention, if x is set to 0.5, the above two equations can be simplified to

[0068]

[0069]

[0070] Then, by multiplying (9) and (10) by x, the true infrared light signal value can be obtained. The further objectives and advantages of the present invention will be fully reflected through understanding the following description and accompanying drawings.

[0071] These and other objects, features and advantages of the present invention will be more fully understood from the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. In the accompanying drawings, unless otherwise specified, the same reference numerals are used to represent the same components.

[0073] Figure 1 This is a schematic diagram of the RGBIR color arrangement of a color image sensor in the prior art.

[0074] Figure 2 FIG. 4 is a schematic block diagram of the structure of an image sensor according to a first preferred embodiment of the present invention.

[0075] Figure 3 FIG. 4 is a schematic diagram of pixel distribution of an image sensor according to a first preferred embodiment of the present invention.

[0076] Figure 4 FIG. 1 is a cross-sectional schematic diagram of an image sensor according to a first preferred embodiment of the present invention.

[0077] Figure 5 FIG. 1 is a top view of an image sensor according to a first preferred embodiment of the present invention.

[0078] Figure 6 FIG. 4 is a cross-sectional schematic diagram of an image sensor according to a second preferred embodiment of the present invention. DETAILED DESCRIPTION

[0079] It should be pointed out that the embodiments shown in the drawings are only used as examples to specifically and vividly explain and illustrate the concept of the present invention. Their size and structure are not necessarily drawn to scale, nor do they constitute a limitation to the concept of the present invention.

[0080] The directional terms such as up, down, left, right, front, back, front, back, top, and bottom mentioned or possibly mentioned in this specification are defined relative to the structure shown in the respective drawings. They are relative concepts and may vary accordingly depending on the position or usage of the device. Therefore, these or other directional terms should not be interpreted as restrictive.

[0081] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0082] Refer to the accompanying drawings of this application specification Figures 2 to 5 As shown, an image sensor according to the first preferred embodiment of the present application is explained in the following description. The image sensor includes a pixel array structure 10, a photoelectric conversion structure 20, and a color filter array 30 located in the light incident direction of the pixel array structure 10, wherein the pixel array structure 10 is located between the photoelectric conversion structure 20 and the color filter array 30 and is connected to the photoelectric conversion structure 20, and the pixel array structure 10 is an array composed of multiple physical pixels. The color filter array 30 includes color filter units 31 corresponding to incident light of different wavelength bands, wherein each color filter unit of the color filter array 30 is located at the front end of the physical pixel and forms spectral channels of different wavelength bands corresponding to the pixel, such as R, G, B, IR channels or spectral channels corresponding to more spectra, for example, it can further include C, Y, M channels, etc., and this application does not impose any restrictions on this.

[0083] That is, the color filter array 30 includes at least two color filter units 31 with different colors, and the color filter units 31 respectively correspond to the spectral channels of the incident light in the corresponding bands. For example, the red filter unit of the color filter array 30 corresponds to the R channel of the incident red light, the green filter unit of the color filter array 30 corresponds to the G channel, the blue filter unit of the color filter array 30 corresponds to the B channel, and the infrared filter unit of the color filter array 30 corresponds to the IR channel.

[0084] As an example, in a specific embodiment of the present application, the image sensor is a color image sensor with an IR channel, that is, the pixel array structure 10 includes an R channel, a G channel, a B channel, and an IR channel. It should be noted that the color filter units 31 of different colorants in the color filter array 30 correspond to different spectral channels. Different channels of the color filter array 30 and the physical pixels corresponding to the channels are defined as the pixels corresponding to the channels. For example, an IR channel and the corresponding physical pixel are combined to form an IR pixel. One channel can correspond to one physical pixel, or one channel can correspond to multiple physical pixels, for example, one channel corresponds to four physical pixels.

[0085] Generally speaking, each pixel receives the sum of the crosstalk signals from all other channels surrounding it. Even with the numerous physical structures in RGBIR cameras designed to suppress crosstalk, long wavelengths inevitably penetrate farther into the pixel, making the infrared channel more susceptible to crosstalk from red light. While the impact of medium and short wavelengths is less severe, it's still significant. For these reasons, each wavelength contributes different amounts of crosstalk to the infrared (IR) channel. Furthermore, since RGB is a partially overlapping, wide-bandwidth spectroscopic channel, it's difficult to accurately calculate the crosstalk ratio of each IR channel to the R, G, and B channels in complex everyday lighting environments, thereby minimizing their impact.

[0086] One color filter unit 31 of the color filter array 30 corresponds to at least two spectral channels with different photosensitivity, and the photosensitivity of the at least two spectral channels corresponding to the color filter unit 31 is arranged in a specific ratio.

[0087] In a specific example of the present application, the color filter unit 31 of the color filter array 30 further includes a first sub-color filter unit 311 and a second sub-color filter unit 312, wherein the first sub-color filter unit 311 and the second sub-color filter unit 312 have the same color, such as but not limited to the R channel, the G channel, the B channel, and the IR channel. The first sub-color filter unit 311 and the second sub-color filter unit 312 are arranged at intervals, that is, a color filter unit of another type is spaced between the first sub-color filter unit 311 and the second sub-color filter unit 312, and the photosensitivity of the spectral channel corresponding to the first sub-color filter unit 311 is x times the photosensitivity of the spectral channel corresponding to the second sub-color filter unit 312. Figure 3As shown in a specific example of the present application, IRi,j in the figure refers to the second sub-color filter unit 312 corresponding to the i-th row and j-th column, wherein xIRi,j+1, xIRi,j-1, xIRi-1,j, and xIRi+1,j are respectively the first sub-color filter units 311 spaced apart from IRi,j, and an R filter unit and a G filter unit are spaced between the first sub-color filter unit 311 and the second sub-color filter unit 312. It should be noted that, preferably, the spaced arrangement means that the first sub-color filter unit and the second sub-color filter unit are not adjacent in a physical sense, but a filter unit that is consistent with the first sub-color filter unit or the second sub-color filter unit is not set between the two color filter units, and other different color filter units may be set.

[0088] In this preferred embodiment of the present application, after completing the photoelectric signal conversion, the image sensor obtains a near-pure photoelectric signal for the pixel through calculation. It is understood that the spectral channels of the image sensor may include, but are not limited to, R, G, B, and IR channels. Pixels corresponding to the color filter unit 31 in the same wavelength band include normal pixels and proportional pixels. The spectral channel corresponding to normal pixels is the normal channel, which can be understood as having no occlusion or other processing, and a photosensitivity of 1. The spectral channel corresponding to proportional pixels is the proportional channel, where the photosensitivity of the proportional channel is x times that of the normal channel, where x ≠ 1. As an example, in a specific embodiment of the present application, the spectral channel corresponding to the first sub-filter unit 311 of the color filter unit 31 is the normal channel, with a photosensitivity of 1; the spectral channel corresponding to the second sub-filter unit 312 is the proportional channel, where its photosensitivity is x times that of the normal channel, where x ≠ 1.

[0089] In a specific example of the present application, in an RGBIR sensor having visible light and near-infrared (IR) channels, the photosensitivity of the proportional IR channel of the two alternately arranged IR channels is set to x times that of the normal IR channel, and after completing the optical-to-electrical signal conversion, a nearly pure IR signal can be directly obtained through calculation. That is, in a specific example of the present application, the image sensor is an RGBIR sensor having visible light and near-infrared (IR) channels, wherein the color filter unit 31 of the color filter array 30 includes a red filter unit, a green filter unit, a blue filter unit, and an infrared filter unit, and the first sub-filter unit 311 of the color filter unit 31 corresponds to the normal IR channel with a photosensitivity of 1, and the second sub-filter unit 312 corresponds to the proportional IR channel with a photosensitivity of x.

[0090] As an example, in this preferred embodiment of the present application, taking the IR channel in the RGBIR sensor as an example, the photosensitivity corresponding to the two IR channels (i.e., the normal IR channel and the proportional IR channel) arranged at intervals are set in a specific ratio, and the photoelectric crosstalk of the infrared pixels is removed by calculation to obtain a nearly pure IR signal.

[0091] like Figure 3 The diagram shows the arrangement of the pixel array structure 10 of the image sensor of this preferred embodiment of the present application, wherein the IR pixel is a normal infrared pixel, and the xIR pixel is a proportional infrared pixel with a sensitivity set to x times that of the IR pixel. That is, when exposed to the same infrared light, without considering crosstalk, the signal output by the xIR pixel is x times the signal output by the IR pixel. The pixel size is typically at the micron level, and the spacing between the spaced IR pixels and xIR pixels is very small, generally not exceeding 10 μm. At the same time, the R, G, B, or other channels surrounding each IR channel and the xIR channel are arranged in the same manner. Therefore, at the scale of the spaced IR pixels and xIR pixels, it can be assumed that the signal of each other pixel surrounding the IR channel is consistent with the signal of each other pixel responding to the xIR channel, and the sum of the crosstalk signals received by the surrounding pixels of the IR and xIR channels is approximately consistent.

[0092] Right now:

[0093]

[0094] CTK is the amount of crosstalk signal received by a certain pixel.

[0095] The signal composition of each IR channel is:

[0096] DN IR =S IR +CTK IR (2)

[0097] DN xIR =S xIR +CTK xIR (3)

[0098] Where DN is the readout signal value output by a single pixel, which includes the sum of the real signal without crosstalk and the crosstalk signal. S is the real signal value without crosstalk generated by the pixel after being irradiated with light.

[0099] When the sensitivity of the xIR pixel is x times that of the IR pixel after a specific design, we have:

[0100] S IR =x·S xIR (4)

[0101] Formula (2)-(3) gives

[0102]

[0103]

[0104] In equations (5) and (6), the crosstalk signal is directly eliminated through simple arithmetic operations, thereby obtaining a pure IR channel signal. Since the signal strength of the IR pixel and the xIR pixel differs by a factor of x, when actually outputting the image, the two need to be adjusted to the same ratio by a factor of x. For example, the output signal of the xIR pixel is SxIR / x, while the IR pixel remains unchanged, or the xIR pixel remains unchanged and the IR pixel output signal is xSIR.

[0105] As an example, in a specific example of the present application, to simplify the design and calculation, x can be designed to be 0.5. Then, as a preferred embodiment of the present application, the true signal value without crosstalk of the IR pixel and the xIR pixel can be obtained as follows:

[0106] S IR =2·(DN IR -DN xIR )

[0107] S xIR =DN IR -DN xIR

[0108] After x times the scaling operation, the complete output image signal can be obtained.

[0109] Of course, in actual use scenarios, the lighting environment around each pixel may be different. In this case, simply using the conclusions of (5) and (6) may cause signal distortion. In order to ensure the accuracy of signal restoration, the following calculation scheme can be used for more accurate restoration:

[0110] When calculating the true signal of a certain IR pixel and xIR pixel without crosstalk, it can be calculated with the average value of the signals of four alternately arranged IR pixels and xIR pixels, that is:

[0111]

[0112]

[0113] If x is set to 0.5, the above two equations are simplified to

[0114]

[0115]

[0116] By multiplying (9) and (10) by x, we can get the true infrared light signal value. Through this operation, the light intensity signals output by the two pixels with different sensitivities have the same level, and will not output signals with different brightness due to differences in sensitivity.

[0117] It is worth mentioning that the solution for reducing crosstalk in the IR channel in the present invention is not only applicable to RGBIR (i.e., 4 channels), but is also applicable to image sensors with more than 4 channels (such as 9 channels or 16 channels). It only requires setting the sensitivity of one of the alternately arranged IR channels to x times that of the other, and ensuring that the pixel arrangements of all other channels around IR and xIR are completely consistent.

[0118] It is worth mentioning that the image sensor of this preferred embodiment of the present application is not limited to removing crosstalk from the IR channel. According to the design requirements of the image sensor, the above-mentioned design can be performed on the channels corresponding to the required bands, such as the R channel, the B channel, and the channels of other bands.

[0119] like Figure 4 and Figure 5 As shown, the image sensor of the first preferred embodiment of the present application is a back-illuminated image sensor. The pixel array structure 10 is formed on the upper surface of the photoelectric conversion structure 20, and the pixels of the pixel array structure 10 correspond to the photodiodes (PDs) of the photoelectric conversion structure 20, forming a physical pixel unit. The pixel array structure 10 includes a passivation layer 11 and a metal gate 12, wherein the passivation layer 11 and the metal gate 12 are located above the photoelectric conversion structure 20, and the metal gate 12 is an opaque structure for separating and blocking light between pixels. As an example, the metal gate 12 is metal AL or W.

[0120] The shielding area of the metal grid 12 on the surface of the geometric pixel (such as xIR) is larger than the shielding area on the surface of the normal pixel (IR). That is, by changing the shielding area of the metal grid on the surface of the geometric pixel and blocking part of the incident light, the sensitivity of the pixel can be adjusted to x times that of the normal pixel. It can be understood that when x is less than 1, the amount of light entering the normal channel is greater than the amount of light entering the geometric channel. When light of the same intensity is irradiated on the surface of the normal pixel and the blocked geometric pixel, the area allowed for light to pass through is only x times that of the normal pixel, while the photoelectric conversion unit below is exactly the same, and the signal generated is only x times that of the normal pixel, which is manifested macroscopically as a change in sensitivity. The appropriate x is obtained by modulating the ratio of the shielding area and the light-transmitting area. For example, by setting the shielding area of the xIR pixel to 0.5 times that of the IR, an xIR pixel with x=0.5 can be obtained.

[0121] The metal grid 12 includes a spacing unit 121 and a shielding unit 122, wherein the spacing unit 121 is arranged between the PDs (photodiodes) of two adjacent normal pixels to space the incident light entering the two adjacent pixels, wherein the shielding unit 122 is arranged above the PDs corresponding to the proportional pixels to reduce the amount of incident light entering the pixel, thereby adjusting the photosensitivity of the pixel. It should be noted that in this preferred embodiment of the present application, the shielding unit 122 of the metal grid 12 is a structure formed by thickening around the spacing unit 121, and the present application is not limited to the above-mentioned metal thickening structure. Therefore, the shielding unit 122 of the metal grid only needs to have a specific proportion of shielding for the lower PD. For example, the shielding unit 122 can be, but is not limited to, a network-shaped, dot-shaped, pixel central square or stripe-shaped shielding, and the present application does not impose any restrictions on this.

[0122] It is worth mentioning that, for the same incident light, if it is blocked, part of the light cannot enter. Then, under the same PD, the proportional pixel receives x times the front incident light of the normal pixel (x≠1). Preferably, in this preferred embodiment of the present application, 0<x<1.

[0123] It is worth mentioning that crosstalk mostly occurs at the bottom of the metal gate 12 or inside the PD. Therefore, the metal gate 12 used for shielding will not affect the crosstalk of surrounding pixels to normal pixels. Therefore, the crosstalk experienced by normal pixels and proportional pixels is the same, and only the light incident from the front is different.

[0124] The color filter array 30 includes a plurality of color filter units 31, wherein the color filter units correspond to the spectral channels of the pixels, wherein the color filter units 31 include but are not limited to R filter units, G filter units, B filter units, and IR filter units.

[0125] The image sensor further includes a microlens array 40 , wherein the microlens array 40 is located above the color filter array 30 , wherein incident light enters the color filter array 30 through the microlens array 40 , and the microlens array 40 is used to optimize the stacking structure of the light path.

[0126] like Figure 2 As shown, the image sensor further includes a computing module 50, which is electrically connected to the photoelectric conversion structure 20. The electrical signal converted by the photoelectric conversion structure 20 is output through the computing module and then output as an image. It is understood that the computing module 50 can be integrated into the low-crosstalk color image sensor or provided in the computing module of the camera system. That is, the calculation process of the above-mentioned calculation method can be implemented in the computing module 50 through circuit design, or it can be performed by the camera system without the calculation output.

[0127] like Figure 6 As shown, an image sensor according to the second preferred embodiment of the present application is a front-illuminated image sensor. The difference from the above preferred embodiment is the structure of the pixel array 10A, wherein the pixel array 10A includes a passivation layer 11A and a metal interconnection structure 13A formed on the passivation layer 11A, wherein the metal interconnection structure 13A is opaque and is located above the photodiode of the photoelectric conversion structure 20.

[0128] The metal interconnect structure 13A includes a spacing segment 131A and a blocking segment 132A, wherein the spacing segment 131A is arranged between the photodiodes of two adjacent normal pixels, and the blocking segment 132A is arranged above the corresponding photodiode of the proportional pixel to block part of the incident light entering the photodiode, that is, part of the light entering the proportional pixel is blocked by the blocking segment 132A of the metal interconnect structure 13A, thereby obtaining the corresponding x times photosensitivity.

[0129] It is understandable that the image sensor of this preferred embodiment of the present application is not limited to a sensor with four channels of RGBIR. Therefore, the image sensor can also be implemented as other types of sensors containing more colors, and the pixels corresponding to adjacent specific bands can be set to a fixed ratio of sensitivity.

[0130] It is worth mentioning that the above-mentioned first preferred embodiment and the above-mentioned second preferred embodiment of the present application adjust the photosensitivity by blocking the incident light entering the pixels of a specific band. In addition to the above-mentioned use of metal blocking, other methods can also be used to achieve sensitivity adjustment, wherein the sensitivity adjustment must ensure that the sensitivity ratio for all required wavelengths in the IR band is consistent, for example, from 750 to 1300nm, x is 0.5, or x is 0.5 near the typical value of 850nm / 940nm.

[0131] A method for reducing the amount of crosstalk in a color image sensor according to another aspect of the present application is described below, wherein the method for reducing the amount of crosstalk in a color image sensor comprises the following steps:

[0132] (a) setting the photosensitivity of at least one wavelength band corresponding to a spectral channel according to a specific ratio, wherein the photosensitivity of one of two alternately arranged spectral channels corresponding to the wavelength band is set to x times the photosensitivity of the other; and

[0133] (b) After the photoelectric signal conversion is completed, a nearly pure photoelectric signal of the pixel is obtained through calculation.

[0134] In the method for reducing crosstalk in a color image sensor according to this preferred embodiment of the present application, the color image sensor is a color image sensor with an IR channel, wherein the spectral channel can be an R channel, a G channel, a B channel, or an IR channel. The pixels corresponding to the channel include normal pixels and geometrically scaled pixels, and the normal pixels and the geometrically scaled pixels are arranged alternately. The spectral channel corresponding to the normal pixels is the normal channel, and the spectral channel corresponding to the geometrically scaled pixels is the geometrically scaled channel. The photosensitivity of the geometrically scaled channel is x times the photosensitivity of the normal channel, where x ≠ 1.

[0135] As an example, in this preferred embodiment of the present application, the channel for reducing the amount of crosstalk is taken as an example of the IR channel in the RGBIR sensor, and the photosensitivity corresponding to the two IR channels (i.e., the normal IR channel and the proportional IR channel) arranged at intervals is set by a specific ratio, where IR is a normal infrared pixel and xIR is a proportional infrared pixel with the sensitivity set to x times that of the IR pixel. When irradiated with the same infrared light, without considering crosstalk, the signal output by the xIR pixel is x times the signal of the IR pixel. The RGB or other color channels around each IR channel and the xIR channel are arranged in exactly the same way, so at the scale of the IR pixels and the xIR pixels arranged at intervals, it can be considered that the signal of each other pixel around the IR channel is consistent with the signal of each other pixel responding to the xIR channel, and then the sum of the crosstalk signals of the surrounding pixels received by IR and xIR is approximately consistent.

[0136] In the step (b) of the method for reducing crosstalk in the preferred embodiment of the present application,

[0137]

[0138] Where CTK is the amount of crosstalk signal received by a pixel, and the signal composition of each IR channel is:

[0139] DN IR =S IR +CTK IR (2)

[0140] DN xIR =S xIR +CTK xIR (3)

[0141] Where DN is the readout signal value output by a single pixel, which includes the sum of the real signal without crosstalk and the crosstalk signal. S is the real signal value without crosstalk generated by the pixel after being irradiated with light.

[0142] Furthermore, when the sensitivity of xIR is x times that of IR, we have:

[0143] SIR =x·S xIR (4)

[0144] Formula (2)-(3) gives

[0145]

[0146]

[0147] In equations (5) and (6), the crosstalk signal is directly eliminated through simple arithmetic operations, thereby obtaining a pure IR channel signal. Since the signal strength of the IR channel and the xIR channel differs by a factor of x, when actually outputting the image, the two need to be adjusted to the same ratio by a factor of x. For example, the output signal of the xIR channel is SxIR / x, while the IR channel remains unchanged, or the xIR channel output signal is xSIR while the xIR channel remains unchanged.

[0148] As an example, in a specific example of this application, to simplify the design and calculation, x can be designed to be 0.5. Then, as a preferred embodiment of this application, the true signal values without crosstalk of IR and xIR can be obtained as follows:

[0149] S IR =2·(DN IR -DN xIR )

[0150] S xIR =DN IR -DN xIR

[0151] After x times the scaling operation, the complete output image signal can be obtained.

[0152] Of course, in actual use scenarios, the lighting environment around each pixel may be different. In this case, simply using the conclusions of (5) and (6) may cause signal distortion. In order to ensure the accuracy of signal restoration, the following calculation scheme can be used for more accurate restoration:

[0153] When calculating the true signal of a certain IR pixel and xIR without crosstalk, it can be calculated with the average of the signals of four alternately arranged IR pixels and xIR pixels, that is:

[0154]

[0155]

[0156] If x is set to 0.5, the above two equations are simplified to

[0157]

[0158]

[0159] By multiplying (9) and (10) by x, we can get the true infrared light signal value. Through this operation, the light intensity signals output by the two pixels with different sensitivities have the same level, and will not output signals with different brightness due to differences in sensitivity.

[0160] Those skilled in the art will appreciate that the embodiments of the present invention described above and shown in the accompanying drawings are intended to be illustrative only and are not intended to limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and illustrated in the embodiments. Any variations or modifications may be made to the embodiments of the present invention without departing from the principles described.

[0161] The technical scope of the present invention is not limited to the contents of the above description. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical concept of the present invention, and these deformations and modifications all fall within the protection scope of the present invention.

Claims

1. A color filter array, characterized in that: include: At least two color filter units with different colors, the color filter units of different colorants correspond to different spectral channels, wherein there is a color filter unit corresponding to at least two spectral channels with different photosensitivity, wherein the color filter units of the color filter array include a first sub-color filter unit and a second sub-color filter unit, wherein the first sub-color filter unit and the second sub-color filter unit have the same color, the first sub-color filter unit and the second sub-color filter unit are arranged at intervals, and the photosensitivity of the first sub-color filter unit corresponding to the spectral channel is x times the photosensitivity of the second sub-color filter unit corresponding to the spectral channel, and x≠1. 2 . The color filter array according to claim 1 , wherein the color filter units include a red color filter unit, a green color filter unit, a blue color filter unit, and an infrared color filter unit. 3 . The color filter array according to claim 1 , wherein the first sub-color filter unit of the color filter unit corresponds to a normal IR channel with a photosensitivity of 1, and the second sub-color filter unit corresponds to a proportional IR channel with a photosensitivity of x.

4. An image sensor, characterized in that include: A pixel array structure, wherein the pixel array structure is an array composed of a plurality of pixels; Photoelectric conversion structure; as well as The color filter array according to any one of claims 1 to 3, wherein the color filter array is located in the light incident direction of the pixel array structure, the pixel array structure is located between the photoelectric conversion structure and the color filter array and is connected to the photoelectric conversion structure, wherein after the photoelectric signal conversion is completed, a nearly pure photoelectric signal of the pixel is obtained through calculation. 5 . The image sensor according to claim 4 , wherein the pixel array structure comprises an R channel, a G channel, a B channel, and an IR channel.

6. The image sensor according to claim 5, wherein IR is a normal infrared pixel, and xIR is a proportional infrared pixel with a sensitivity set to x times that of the IR pixel; when exposed to the same infrared light, without considering crosstalk, the signal output by the xIR pixel is x times the signal output by the IR pixel; each IR channel and the R, G, B or other channels surrounding the xIR channel are arranged in the same manner; at the scale of the spaced IR pixels and xIR pixels, the signal of each other pixel surrounding the IR channel is consistent with the signal of each other pixel responding to the xIR channel.

7. The image sensor according to claim 6, wherein when the sensitivity of xIR is x times that of IR, S IR =x·S xIR (4) Formula (2)-(3) gives Where DN is the readout signal value output by a single pixel. In equations (5) and (6), the crosstalk signal is directly eliminated through calculation, thereby obtaining a pure IR channel signal.

8. The image sensor according to claim 7, wherein x is 0.5, and the true signal values without crosstalk of IR and xIR are obtained as follows: S IR =2·(DN IR -DN xIR ) S xIR =DN IR -DN xIR After x times the scaling operation, the complete output image signal can be obtained.

9. The image sensor according to claim 8, wherein when calculating the true signal of a certain IR / xIR pixel without crosstalk, the signal is calculated by adding the signal to the average of the signals of four IR / xIR pixels arranged at intervals, where x is 0.5, to obtain: The real infrared light signal value is obtained by multiplying (9) and (10) by x times the scale.

10. The image sensor according to any one of claims 5 to 9, wherein the pixel array structure comprises a passivation layer and a metal gate, wherein the passivation layer and the metal gate are located above the photoelectric conversion structure, and the shading area of the metal gate on the surface of the proportional pixel is larger than the shading area on the surface of the normal pixel, so as to adjust the sensitivity of the proportional pixel to x times that of the normal pixel.

11. The image sensor according to claim 10, wherein the metal gate comprises a spacing unit and a shielding unit, wherein the spacing unit is arranged between the PDs of two adjacent normal pixels to space the incident light entering the two adjacent pixels, and wherein the shielding unit is arranged above the PD corresponding to the proportional pixel to reduce the amount of incident light entering the pixel.

12. The image sensor according to claim 10 , wherein the pixel array comprises a passivation layer and a metal interconnection structure formed on the passivation layer, the metal interconnection structure comprises a spacer segment and a blocking segment, wherein the spacer segment is arranged between the photodiodes of two adjacent normal pixels, and wherein the blocking segment is arranged above the corresponding photodiode of the proportional pixel to block part of the incident light entering the photodiode.

13. The image sensor according to claim 11 or 12 further comprises a microlens array, wherein the microlens array is located above the color filter array, wherein incident light enters the color filter array through the microlens array, and the microlens array is used to optimize the stacking structure of the light path.

14. The image sensor according to claim 13, further comprising a computing module, wherein the computing module is electrically connected to the photoelectric conversion structure, and the electrical signal converted by the photoelectric conversion structure is output as an image after passing through the computing module.

15. A method for reducing crosstalk in a color image sensor, characterized in that: The method for reducing the crosstalk of a color image sensor comprises the following steps: (a) setting the photosensitivity of the spectral channel corresponding to at least one wavelength band according to a specific ratio, wherein the photosensitivity of one of the two alternately arranged spectral channels corresponding to the wavelength band is set to x times the photosensitivity of the other, where x≠1; and (b) After the photoelectric signal conversion is completed, a nearly pure photoelectric signal of the pixel is obtained through calculation.

Images