Image sensors, their fabrication methods, and electronic devices

Abstract

This application provides an image sensor, its fabrication method, and an electronic device. The image sensor includes an array of metasurface structures and an array of photoelectric conversion units. The array of metasurface structures is located above the array of photoelectric conversion units. Each photoelectric conversion unit includes multiple photoelectric conversion elements, each corresponding to a frequency band in the spectrum. The metasurface structure includes a first substrate and a microstructure located above the first substrate. The microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band. The microstructure is a rotationally symmetric structure with a rotation angle less than or equal to 90 degrees. The technical solution of this application can improve the light transmittance of each spectral channel, thereby improving the overall light utilization rate of the image sensor.

Description

Technical Field

[0001] This application relates to the field of optical imaging, and more particularly to an image sensor, its fabrication method, and an electronic device. Background Technology

[0002] Image sensors convert optical images into electrical signals and are widely used in various electronic devices, such as digital cameras. The hardware of a digital camera mainly includes a lens assembly, an image sensor, and an electrical signal processor. The lens assembly projects the optical image onto the image sensor. The image sensor converts the light signal of the image into an analog electrical signal, which is then input to the electrical signal processor. The electrical signal processor converts the analog electrical signal into a digital signal, and after data processing, outputs the photograph. As a photoelectric converter, the image sensor is one of the core components of a digital camera, and its performance directly determines the quality of the output photograph.

[0003] Image sensors utilize photoelectric conversion elements to convert light signals of varying intensities into electrical signals of varying intensities. However, these elements themselves cannot distinguish light frequencies, i.e., they cannot distinguish colors. Therefore, images obtained directly from image sensors without a color acquisition layer are black and white. To obtain color images, a color filter system is needed as a color acquisition layer to acquire color information. For example, leveraging the human eye's sensitivity to the red, green, and blue (RGB) primary color spectrum, RGB color filters can be arranged on the photoelectric conversion element to form an RGB mosaic-style Bayer color filter system, enabling the acquisition of color images. However, for each spectral channel, over 70% of the light is filtered out by the Bayer color filter, with less than 30% reaching the photoelectric conversion element to be converted into electrical signals for final computational imaging. This results in very low light utilization for image sensors based on Bayer color filter systems. Summary of the Invention

[0004] This application provides an image sensor, a method for fabricating the same, and an electronic device thereof, to improve the light utilization rate of the image sensor.

[0005] In a first aspect, an image sensor is provided, comprising: an array of metasurface structures and an array of photoelectric conversion units, wherein the array of metasurface structures is located above the array of photoelectric conversion units, wherein the metasurface structure includes a first substrate and a microstructure located above the first substrate, the microstructure and the first substrate being used to transmit optical signals of each frequency band to the photoelectric conversion element corresponding to each frequency band, and the microstructure is a rotationally symmetric structure, wherein the rotation angle of the rotationally symmetric structure is less than or equal to 90 degrees.

[0006] It should be understood that in the embodiments of this application, the microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band. In some cases, it can also be understood that the microstructure and the first substrate are used to focus the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band.

[0007] A rotationally symmetric structure is a structure that can coincide with itself by rotating around its center point by an angle. The angle of rotation is called the rotation angle. The microstructure in the embodiments of this application can coincide with itself by rotating 90 degrees or less than 90 degrees around its center point.

[0008] The microstructures on a metasurface structure can be one or multiple.

[0009] According to the embodiments of this application, the metasurface structure can adjust the transmission direction of the optical signal, transmitting the optical signal of each frequency band received by the entire metasurface structure to the corresponding photoelectric conversion element. This method uses beam splitting instead of existing filtering, avoiding signal loss during filtering. The rotationally symmetric structure with a rotation angle less than or equal to 90 degrees provides the same response to optical signals of different polarizations, eliminating polarization dependence and improving the transmittance of each spectral channel. Overall, this improves the light utilization rate of the image sensor and enhances the imaging quality of the output image. For example, the polarization can include linear polarization and circular polarization.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, the microstructure and the first substrate are used to generate a spatial transmission phase in the tangential direction of the array of metasurface structures to obtain a spatial transmission phase gradient, which is used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band.

[0011] According to the scheme of the embodiments of this application, the transmission direction of optical signals of different frequency bands is controlled by the spatial transmission phase gradient generated on the array of metasurface structures, so that optical signals of different frequency bands can be transmitted to the photoelectric conversion elements corresponding to different frequency bands, thereby improving the light transmittance of each spectral channel and improving the overall light utilization of the image sensor.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the spatial transmission phase distribution is related to the wavelength of the optical signal in each frequency band, the position of the optical signal in each frequency band incident on the metasurface structure, and the position of the optical signal in each frequency band transmitted to the photoelectric conversion element corresponding to each frequency band.

[0013] Optionally, the metasurface structure and the photoelectric conversion unit may not be in direct contact. The spatial transport phase distribution is also related to the refractive index of the medium between the metasurface structure and the photoelectric conversion element. In some cases, it can also be said that the spatial transport phase distribution is related to the refractive index of the medium between the metasurface structure and the photoelectric conversion unit.

[0014] For example, the spatial transmission phase of the nth frequency band at a certain location on the metasurface structure, the wavelength of the light signal of the nth frequency band, the coordinates of the location of the light signal of the nth frequency band transmitted to the photoelectric conversion element corresponding to the nth frequency band, and the refractive index of the medium between the metasurface structure and the photoelectric conversion unit are related.

[0015] In conjunction with the first aspect, in certain implementations of the first aspect, the spatial transmission phase distribution φ(x,y,λ) n )satisfy:

[0016]

[0017] Where x, y represent the coordinates of the position on the metasurface structure, and λ n f represents the wavelength of the optical signal in the nth frequency band. n x represents the focal length corresponding to the optical signal in the nth frequency band. f,n and y f,n The coordinates of the position where the optical signal of the nth frequency band is transmitted to the photoelectric conversion element corresponding to the nth frequency band are represented. sub The refractive index of the medium between the metasurface structure and the photoelectric conversion unit is given, where C represents any phase.

[0018] In conjunction with the first aspect, in some implementations of the first aspect, the medium is air.

[0019] In other words, the metasurface structure and the photoelectric conversion unit can form a hollow structure, which can be filled with air.

[0020] In conjunction with the first aspect, in some implementations of the first aspect, the medium includes a second substrate.

[0021] The metasurface structure can contact the photoelectric conversion unit through a second substrate, which can be used to support the metasurface structure.

[0022] Optionally, the material of the second substrate can be a low-loss transparent dielectric material. For example, the material of the second substrate can be silicon dioxide glass, etc.

[0023] In conjunction with the first aspect, in some implementations of the first aspect, the microstructure includes a cylindrical structure, a square column structure, or a cross-shaped structure.

[0024] In conjunction with the first aspect, in some implementations of the first aspect, the material of the microstructure includes titanium dioxide, gallium nitride, or silicon carbide.

[0025] In conjunction with the first aspect, in some implementations of the first aspect, the material of the first substrate includes silicon dioxide, titanium dioxide, gallium nitride, or silicon carbide.

[0026] In conjunction with the first aspect, in some implementations of the first aspect, the plurality of photoelectric conversion elements correspond to V different frequency bands in the spectrum, where V is an integer greater than 3.

[0027] For example, V can be 4, and the four frequency bands can be red, yellow, cyan, and purple. Alternatively, the four frequency bands can be cyan-green, magenta, yellow, and white.

[0028] For example, V can be 7, and the 7 frequency bands can be red, orange, yellow, green, cyan, blue, and purple.

[0029] According to the solution of the embodiments of this application, by increasing the number of different frequency bands corresponding to a photoelectric conversion unit, more spectral information can be obtained with less light utilization loss, thereby improving the spectral utilization of the image sensor, reducing the loss of color information in the image, increasing the color fidelity of the imaging, and improving the imaging quality.

[0030] Secondly, a method for fabricating an image sensor is provided, comprising: fabricating an array of photoelectric conversion units; and fabricating an array of metasurface structures on the array of photoelectric conversion units, wherein the photoelectric conversion units include multiple photoelectric conversion elements, each photoelectric conversion element in the photoelectric conversion units corresponds to a frequency band in the spectrum, the metasurface structure includes a first substrate and a microstructure located above the first substrate, the microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band, and the microstructure is a rotationally symmetric structure, wherein the rotation angle of the rotationally symmetric structure is less than or equal to 90 degrees.

[0031] For example, arrays of photoelectric conversion units and arrays of metasurface structures are integrated and fabricated using complementary metal oxide semiconductor (CMOS) technology.

[0032] According to the scheme of this application embodiment, the integrated processing of the array of photoelectric conversion units and the array of metasurface structures can ensure a good alignment effect between the photoelectric conversion units and the metasurface structures, thereby improving the accuracy of the image sensor. The metasurface structure can transmit the optical signal of each frequency band received by the entire metasurface structure to the corresponding photoelectric conversion element. It uses a beam splitting method instead of the existing filtering method, avoiding the loss of optical signal during the filtering process. Employing a rotationally symmetric structure with a rotation angle less than or equal to 90 degrees, it has the same response to the polarization of the optical signal, eliminating polarization dependence and improving the light transmittance of each spectral channel. Overall, it improves the light utilization rate of the image sensor and enhances the imaging quality of the output image. For example, the polarization of the optical signal can include linearly polarized light and circularly polarized light.

[0033] In conjunction with the second aspect, in some implementations of the second aspect, the microstructure and the first substrate are used to generate a spatial transmission phase in the tangential direction of the array of metasurface structures to obtain a spatial transmission phase gradient, which is used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band.

[0034] According to the scheme of the embodiments of this application, the spatial transmission phase gradient generated on the array of metasurface structures changes the transmission direction of optical signals of different frequency bands, so that optical signals of different frequency bands can be transmitted to the photoelectric conversion elements corresponding to different frequency bands, thereby improving the light transmittance of each spectral channel and improving the overall light utilization of the image sensor.

[0035] Thirdly, a method for fabricating an image sensor is provided, comprising: fabricating an array of photoelectric conversion units; fabricating an array of metasurface structures; assembling the array of metasurface structures with the array of photoelectric conversion units to obtain an image sensor; wherein, the photoelectric conversion unit includes a plurality of photoelectric conversion elements, each photoelectric conversion element in the photoelectric conversion unit corresponds to a frequency band in the spectrum, the metasurface structure includes a first substrate and a microstructure located above the first substrate, the microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band, the microstructure is a rotationally symmetric structure, and the rotation angle of the rotationally symmetric structure is less than or equal to 90 degrees.

[0036] For example, an array of metasurface structures can be fabricated using CMOS technology and then assembled with an array of photoelectric conversion units.

[0037] According to the embodiments of this application, the array of photoelectric conversion units and the array of metasurface structures are fabricated separately, resulting in a relatively simple fabrication process. The metasurface structure enables the transmission of optical signals in each frequency band received by the entire metasurface structure to the corresponding photoelectric conversion element. This uses beam splitting instead of existing filtering methods, avoiding signal loss during filtering. The rotationally symmetric structure with a rotation angle less than or equal to 90 degrees provides the same response to optical signal polarization, eliminating polarization dependence and improving the transmittance of each spectral channel. Overall, this improves the light utilization rate of the image sensor and enhances the imaging quality of the output image. For example, the polarization of the optical signal can include linearly polarized light and circularly polarized light.

[0038] In conjunction with the third aspect, in some implementations of the third aspect, the microstructure and the first substrate are used to generate a spatial transmission phase in the tangential direction of the array of metasurface structures to obtain a spatial transmission phase gradient, which is used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band.

[0039] According to the scheme of the embodiments of this application, the spatial transmission phase gradient generated on the array of metasurface structures changes the transmission direction of optical signals of different frequency bands, so that optical signals of different frequency bands can be transmitted to the photoelectric conversion elements corresponding to different frequency bands, thereby improving the light transmittance of each spectral channel and improving the overall light utilization of the image sensor.

[0040] Fourthly, an electronic device is provided, including the image sensor of the first aspect and any implementation thereof.

[0041] According to the embodiments of this application, the electronic device includes an image sensor based on a metasurface structure. The metasurface structure can transmit the optical signal of each frequency band received by the entire metasurface structure to the photoelectric conversion element corresponding to that frequency band. It uses a beam splitting method instead of the existing filtering method, avoiding the loss of optical signal during the filtering process. Employing a rotationally symmetric structure with a rotation angle less than or equal to 90 degrees, it has the same response to the polarization of the optical signal, eliminating polarization dependence and improving the light transmittance of each spectral channel. Overall, it improves the light utilization rate of the image sensor and enhances the imaging quality of the output image. For example, the polarization of the optical signal can include linearly polarized light and circularly polarized light. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the electronic device.

[0043] Figure 2 This is a schematic diagram of the structure of an image sensor based on a Bayer filter system.

[0044] Figure 3 This is a schematic diagram of the structure of a single color pixel unit in an image sensor based on a Bayer filter system.

[0045] Figure 4 This is a schematic diagram of optical signal transmission in a spectral channel.

[0046] Figure 5 This is a schematic diagram of the structure of the image sensor provided in the embodiments of this application.

[0047] Figure 6 This is a schematic diagram of the microstructure provided in the embodiments of this application.

[0048] Figure 7 This is a schematic diagram of the optical path transmission on the image sensor provided in the embodiments of this application.

[0049] Figure 8 This is a schematic diagram of a color pixel unit in an image sensor provided in an embodiment of this application.

[0050] Figure 9 This is a schematic diagram of the arrangement of photoelectric conversion elements provided in the embodiments of this application.

[0051] Figure 10 This is a schematic diagram of the refraction and reflection of optical signals provided in the embodiments of this application.

[0052] Figure 11 This is a schematic diagram of the spatial transmission phase distribution corresponding to different frequency bands provided in the embodiments of this application.

[0053] Figure 12 This is a schematic diagram of a method for fabricating an image sensor according to an embodiment of this application.

[0054] Figure 13 This is a schematic diagram of another method for fabricating an image sensor provided in an embodiment of this application.

[0055] Figure 14 This is a schematic diagram of an image sensor design method provided in an embodiment of this application. Detailed Implementation

[0056] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0057] The electronic devices involved in the embodiments of this application may include handheld devices, in-vehicle devices, wearable devices, computing devices, or other processing devices connected to a wireless modem. They may also include digital cameras, cellular phones, smartphones, personal digital assistant (PDA) computers, tablet computers, laptop computers, machine type communication (MTC) terminals, point of sale (POS) terminals, in-vehicle computers, and other electronic devices with imaging capabilities.

[0058] For ease of understanding, the technical terms used in this application will be explained and described below.

[0059] Metamaterial: In a broad sense, it refers to a composite material with a unit structure that is artificially designed and possesses physical properties that are not found in traditional natural materials. Its physical properties are mainly determined by the structure and arrangement of the subwavelength (much smaller than the wavelength) unit structure.

[0060] Metasurface: A two-dimensional form of metamaterial, that is, a surface structure composed of subwavelength micro-unit structures.

[0061] Focal point: When light enters a metasurface structure, the light rays converge at several points behind the metasurface structure. These points where the light rays converge are called focal points.

[0062] Focal length: also known as focal length, is a measure of the convergence or divergence of light in an optical system. In the embodiments of this application, it refers to the distance from the optical center of the metasurface structure to the focal point when a scene at infinity is formed into a clear image on the focal plane through the metasurface structure. It can also be understood as the perpendicular distance from the optical center of the metasurface structure to the focal plane.

[0063] Figure 1 A schematic diagram of an electronic device is shown. As shown, the electronic device may include a lens assembly 110, an image sensor 120, and an electrical signal processor 130. The electrical signal processor 130 may include an analog-to-digital (A / D) converter 131 and a digital signal processor 132. The analog-to-digital converter 131 is an analog-to-digital signal converter used to convert analog electrical signals into digital electrical signals.

[0064] It should be understood that Figure 1The electronic devices shown are not limited to those mentioned above, but may also include other devices such as batteries, flashlights, buttons, sensors, etc. This application embodiment only uses an electronic device equipped with an image sensor 120 as an example for illustration, but the components installed on the electronic device are not limited to this.

[0065] The light signal reflected from the subject is converged by the lens assembly 110 and imaged onto the image sensor 120. The image sensor 120 converts the light signal into an analog electrical signal. The analog electrical signal is converted into a digital electrical signal by the analog-to-digital (A / D) converter 131 in the electrical signal processor 130, and then processed by the digital signal processor 132, for example, by optimizing the data electrical signal through a series of complex mathematical algorithms, and finally outputting an image. The electrical signal processor 130 may also include an analog signal preprocessor 133, which preprocesses the analog electrical signal transmitted from the image sensor and outputs it to the analog-to-digital converter 131.

[0066] The performance of the image sensor 120 affects the quality of the final output image. The image sensor 120, also known as a photosensitive chip or photosensitive element, contains hundreds of thousands to millions of photoelectric conversion elements. When exposed to light, these elements generate electrical charges, which are then converted into digital signals by an analog-to-digital converter chip.

[0067] Typically, the image sensor 120 acquires color information of an image through a color filter system. This color filter system can be a Bayer color filter system. That is, a Bayer color filter is formed by covering the photoelectric conversion element in the image sensor 120. The photoelectric conversion element can be a photodiode. A Bayer color filter can also be called a Bayer optical filter. Figure 2 A schematic diagram of an image sensor based on a Bayer color filter system is shown. The image sensor includes a microlens 121, a Bayer color filter 122, and a photodiode 123. The Bayer color filter 122 includes RGB color filters, which are arranged on a grid of photodiodes to form an RGB mosaic color filter system. Mimicking the biological characteristic that green photoreceptor cells are the most numerous in the human retina, Bayer color filters are typically arranged in an RGGB configuration.

[0068] Figure 3 A schematic diagram of the structure of a color pixel unit in an image sensor based on a Bayer color filter system is shown. Figure 3As shown, a color pixel unit includes four color filters 122 and four corresponding photodiode 123 pixels. The four color filters 122 are arranged in an RGGB configuration, with the red and blue filters diagonally opposite each other and the two green filters diagonally opposite each other. Since the photosensitive area of ​​the photodiode 123 is located at the center of the area occupied by the photodiode pixel, a color pixel unit also includes a microlens array 121 above the color filters 122. This microlens array 121 is used to focus the light signal onto the photosensitive area of ​​the photodiode 123 to ensure light utilization. The microlens array 121 focuses the incident light signal onto the four color filters 122 respectively. After being filtered by the four color filters 122, the light is transmitted to the photodiode 123 it covers, thereby simultaneously obtaining the light intensity information and approximate color information of the image. Afterwards, through a software interpolation algorithm, the closest color image to reality can be optimized and restored.

[0069] However, image sensors based on Bayer filter systems have very low light utilization. For each color pixel channel, or spectral channel, more than 70% of the light signal is filtered out by the Bayer filter, and less than 30% of the light can reach the photodiode to be converted into an electrical signal for final computational imaging. Figure 4 A schematic diagram of the luminous flux of one spectral channel in a color pixel unit is shown. (See diagram below.) Figure 4 As shown, for a color pixel unit arranged in RGGB format, when the incident light is white light (containing light signals of all wavelengths from 400-700 nanometers), under ideal color filtering conditions, the theoretical maximum luminous flux after filtering is only 1 / 3 of the incident luminous flux; when the incident light is red or blue light, the theoretical maximum luminous flux after filtering is 1 / 4 of the incident luminous flux; and when the incident light is green light, due to the two green channels, the theoretical maximum luminous flux after filtering is 1 / 2 of the incident luminous flux. Moreover, in reality, the color filtering effect of a color filter cannot be perfect; that is, its filtering and light transmission efficiency cannot reach 100%, so the actual light utilization rate will be even lower. The total light utilization rate is only about 25% when the incident light is white light; about 23% when the incident light is red light; about 20% when the incident light is blue light; and about 32% when the incident light is green light.

[0070] Furthermore, images obtained from image sensors based on Bayer color filter systems suffer from color distortion. Bayer filters have only three spectral channels: RGB, while the actual image spectrum is continuously distributed across the visible light band of 400-700 nm. Therefore, the spectral information obtained through Bayer filters is actually a discrete digitization of the continuous spectrum using RGB, meaning all light in the 400-500 nm band is considered blue, all light in the 500-600 nm band is considered green, and all light in the 600-700 nm band is considered red. It should be understood that the above spectral band values ​​are for illustrative purposes only; the specific frequency range of each spectral channel depends on the overall spectral design of the actual image sensor and the actual spectral response range of the photodiode. This approach results in a significant loss of the actual spectral information of the image, causing color distortion in the final image. Additionally, actual color filters may have overlapping transmission spectra. If the incident spectrum is at an overlapping position, the filter will allow the light to enter two spectral channels simultaneously, further contributing to errors in color reproduction.

[0071] The essence of Bayer filters is sacrificing light utilization in exchange for spectral information, or color information. Increasing the number of different spectral channels in a color pixel unit allows for the acquisition of more spectral information. At the physical hardware level, currently, the only way to reduce the loss of spectral information when converting continuous spectrum to discrete spectral information is to increase the number of spectral channels in the Bayer filter, but doing so will further reduce light utilization.

[0072] Figure 5 This illustration shows a structural schematic of an image sensor 200 provided in an embodiment of this application. The image sensor 200 can be... Figure 1 Image sensor 120 in the middle.

[0073] The image sensor 200 includes an array of metasurface structures 210 and an array of photoelectric conversion units 220. The array of metasurface structures 210 is located above the array of photoelectric conversion units 220. Each photoelectric conversion unit 220 includes multiple photoelectric conversion elements, and each photoelectric conversion element in the photoelectric conversion unit 220 corresponds to a frequency band in the spectrum. The metasurface structure 210 includes a first substrate and a microstructure located above the first substrate. The microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band. The microstructure is a rotationally symmetric structure, and the rotation angle of the rotationally symmetric structure is less than or equal to 90 degrees.

[0074] A metasurface structure 210 may include multiple microstructures.

[0075] A rotationally symmetric structure is a structure that can coincide with itself by rotating around its center point by an angle. The angle of rotation is called the rotation angle. The microstructure in the embodiments of this application can coincide with itself by rotating 90 degrees or less than 90 degrees around its center point.

[0076] In the embodiments of this application, each photoelectric conversion element corresponds to a frequency band in the spectrum, or it can be said that each photoelectric conversion element corresponds to a spectrum channel.

[0077] Optionally, Figure 6 A schematic diagram of a microstructure according to an embodiment of this application is shown. The microstructure described above can be a cylindrical structure, such as... Figure 6 As shown in (a), the above microstructure can also be a cross-shaped structure, such as... Figure 6 As shown in (b), the microstructure described above can also be a square columnar structure, such as... Figure 6 As shown in (c). It should be understood that these three structures are for illustrative purposes only, and the shape of the microstructure is not limited to these three structures.

[0078] Optionally, the metasurface structure 210 and the photoelectric conversion unit 220 may not be in direct contact; that is, a medium may exist between the metasurface structure 210 and the photoelectric conversion unit 220.

[0079] Specifically, the medium can be air.

[0080] For example, a hollow structure can be formed between the metasurface structure 210 and the photoelectric conversion unit 220, and the hollow structure can contain air.

[0081] Specifically, the medium can be a second substrate 230.

[0082] For example, the metasurface structure 210 can contact the photoelectric conversion unit 220 through the second substrate 230, which can be used to support the metasurface structure 210.

[0083] Optionally, the material of the second substrate can be a low-loss transparent dielectric material. For example, the material of the second substrate can be silicon dioxide glass, etc.

[0084] It should be understood that in the embodiments of this application, the microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band. In some cases, it can also be understood that the microstructure and the first substrate are used to focus the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band.

[0085] A metasurface structure 210 can correspond to a photoelectric conversion unit 220. The metasurface structure 210 can cover the photoelectric conversion unit 220. The microstructures and the first substrate on each metasurface structure 210 can transmit the incident light signal to the photoelectric conversion unit 220 corresponding to that metasurface structure 210. For ease of description, it can be said that the microstructures and the first substrate on the metasurface structure 210 transmit the incident light signal to the photoelectric conversion unit 220 corresponding to that metasurface structure 210, or that the metasurface structure 210 transmits the incident light signal to the photoelectric conversion unit 220 corresponding to that metasurface structure 210.

[0086] A color pixel unit may include a metasurface structure 210 and a photoelectric conversion unit 220. The color pixel unit may also include a second substrate 230. Multiple color pixel units may be included on the image sensor 200.

[0087] Figure 7 A schematic diagram of the optical path transmission in a color pixel unit of an image sensor is shown. Figure 7 As shown, Figure 7 Metasurface structure 210 and Figure 7 The photoelectric conversion unit 220 (an example of photoelectric conversion unit 220) includes n photoelectric conversion elements, each corresponding to one of the n frequency bands in the spectrum. These n frequency bands may include the same frequency band. The metasurface structure 210 can transmit all received optical signals to the photoelectric conversion elements corresponding to the n frequency bands in the photoelectric conversion unit 220 according to the n frequency bands.

[0088] For each frequency band of optical signal, it is sufficient that the optical signal of each frequency band can be transmitted to the photosensitive area on the photoelectric conversion element corresponding to each frequency band. For example, the focal point can be located below the photoelectric conversion element corresponding to each frequency band, such as... Figure 7 As shown in (a); the focal point can also be located above the photoelectric conversion element corresponding to that frequency band, such as... Figure 7 As shown in (b); the focal point can also be located on the photoelectric conversion element corresponding to that frequency band, such as Figure 7 As shown in (c). The embodiments of this application do not limit the position of the focus.

[0089] Photoelectric conversion elements are used to convert optical signals into electrical signals. For example, a photoelectric conversion element can be a photodiode in a complementary metal oxide semiconductor (CMOS). Another example is a charge-coupled device (CCD).

[0090] It should be understood that Figure 5 and Figure 7 The photoelectric conversion elements shown in the diagram are arranged in a one-dimensional manner for illustrative purposes only and should not be construed as limiting the embodiments of this application. The photoelectric conversion elements can also be arranged in a two-dimensional manner.

[0091] For example, a photoelectric conversion unit 220 may include four photoelectric conversion elements, each corresponding to one of the three frequency bands: red, green, and blue light. The wavelength of red light can be 600-700 nanometers, the wavelength of green light can be 500-600 nanometers, and the wavelength of blue light can be 400-500 nanometers. The frequency bands corresponding to these four photoelectric conversion elements can be arranged in an RGGB pattern, that is, two photoelectric conversion elements on one diagonal correspond to the green light frequency band, and two photoelectric conversion elements on the other diagonal correspond to the red light and blue light frequency bands, respectively. For ease of description, the frequency bands corresponding to the photoelectric conversion elements in the embodiments of this application can also be referred to as the arrangement of the photoelectric conversion elements. For example, arranging the photoelectric conversion elements in an RGGB pattern means that the frequency bands corresponding to the photoelectric conversion elements can be arranged in an RGGB pattern.

[0092] Figure 8 Image (a) shows a schematic diagram of the structure of a color pixel unit in an embodiment of this application. Figure 8 As shown in (a), a color pixel unit may include a metasurface structure 210 and four adjacent two-dimensionally arranged photoelectric conversion elements located below the metasurface structure 210. These four photoelectric conversion elements correspond to... Figure 8 Photoelectric conversion elements A, B, C, and D in (b) are used. These four photoelectric conversion elements can be arranged in an RGGB pattern. For example, photoelectric conversion elements A, B, C, and D can correspond to the red, green, and blue light frequency bands, respectively. The metasurface structure 210 can focus red, green, and blue light onto the photosensitive positions of photoelectric conversion elements A, B, C, and D, respectively.

[0093] It should be understood that the values ​​of the above-mentioned spectrum bands are only for illustrative reference and should not be regarded as limitations on the embodiments of this application. The specific frequency range of each spectrum channel is based on the overall spectrum design of the actual image sensor and the actual spectrum response range of the photoelectric conversion element. Figure 8 The number of photoelectric conversion elements in a single color pixel unit shown is merely illustrative and does not constitute a limitation on the embodiments of this application.

[0094] Figure 9 A schematic diagram of an array of photoelectric conversion units 220 is shown. (As shown) Figure 9As shown, each photoelectric conversion unit 220 can correspond to 4 photoelectric conversion elements, and the 4 photoelectric conversion elements are arranged in the RGGB manner.

[0095] It should be understood that Figure 8 and Figure 9 The number of photoelectric conversion elements in a photoelectric conversion unit 220 shown is merely illustrative and does not constitute a limitation on the embodiments of this application.

[0096] As mentioned earlier, each photoelectric conversion unit 220 includes n photoelectric conversion elements, which can correspond to n frequency bands. Among these n frequency bands, V different frequency bands can be included. That is, n and V can be different, and each photoelectric conversion unit 220 can correspond to V different frequency bands in the spectrum.

[0097] For example, n can be 4 and V can be 3. For instance, the three frequency bands can be red light, green light, and blue light. A photoelectric conversion unit 220 can include four photoelectric conversion elements, meaning a metasurface structure 210 can cover four photoelectric conversion elements. These four photoelectric conversion elements can each correspond to one of the three frequency bands: red light, green light, and blue light.

[0098] Optionally, the plurality of photoelectric conversion elements correspond to V different frequency bands in the spectrum, where V can be an integer greater than 3.

[0099] In other words, the number of photoelectric conversion elements contained in a photoelectric conversion unit 220 is also greater than 3.

[0100] For example, V can be 4, and the four frequency bands can be red, yellow, cyan, and purple. The four frequency bands can also be cyan (C), magenta (M), yellow (Y), and white (W).

[0101] In this context, V and n can be the same. For example, a photoelectric conversion unit 220 can include four photoelectric conversion elements, meaning that a metasurface structure 210 can cover four photoelectric conversion elements. These four photoelectric conversion elements correspond to the four frequency bands of red, yellow, cyan, and violet, respectively.

[0102] For example, V can be 7, and the 7 frequency bands can be red, orange, yellow, green, cyan, blue, and purple.

[0103] Here, V and n can be different. For example, a photoelectric conversion unit 220 can include 9 photoelectric conversion elements, that is, a metasurface structure 210 can cover 9 photoelectric conversion elements. These 9 photoelectric conversion elements correspond to 7 frequency bands: red, orange, yellow, green, cyan, blue, and violet. That is, among the 9 frequency bands corresponding to the 9 photoelectric conversion elements, there are two identical frequency bands.

[0104] By increasing the number of different frequency bands corresponding to a photoelectric conversion unit 220, that is, increasing the number of photoelectric conversion elements covered by a metasurface structure 210, the loss of spectral information acquired by the image sensor can be significantly reduced with a small loss of light utilization, more spectral information can be obtained, the spectral utilization of the image sensor can be improved, the loss of color information in the image can be reduced, and the color fidelity of the imaging can be increased.

[0105] In a photoelectric conversion unit 220, the number of frequency bands corresponding to the photoelectric conversion elements can be called the number of spectrum channels, and the position of the photoelectric conversion element corresponding to a frequency band can be called the position of the spectrum channel.

[0106] The number and location of spectral channels are related to different imaging requirements. Different numbers and / or different locations of spectral channels can meet different imaging needs.

[0107] For example, when multispectral imaging is required, i.e., determining the material of an object by acquiring its spectral information, a photoelectric conversion unit 220 may include nine photoelectric conversion elements. That is, each metasurface structure 210 may cover nine photoelectric conversion elements, and each photoelectric conversion element may correspond to a frequency band. For example, these nine photoelectric conversion elements correspond to the seven frequency bands of red, orange, yellow, green, cyan, blue, and violet, respectively.

[0108] For example, when other color arrangements are required, such as the four frequency bands of cyan (C), magenta (M), yellow (Y), and white (W), a photoelectric conversion unit 220 can include four photoelectric conversion elements, meaning each metasurface structure 210 can cover four photoelectric conversion elements, and the frequency bands corresponding to the four photoelectric conversion elements can be arranged in a CMYW pattern. As another example, if the three frequency bands of red, yellow, and blue are required, a photoelectric conversion unit 220 can include four photoelectric conversion elements, meaning each metasurface structure 210 can cover four photoelectric conversion elements. The frequency bands corresponding to the four photoelectric conversion elements can be arranged in an RYYB pattern.

[0109] Figure 10A schematic diagram of the propagation path of optical signals through reflection and refraction is shown. According to the generalized Snell's law, the directions of reflected and transmitted light depend not only on the refractive index of the interface material but also on the phase gradient distribution at the interface. The formula for the refractive index according to the generalized Snell's law is as follows.

[0110]

[0111] Where n1 represents the refractive index of the incident space, n2 represents the refractive index of the exit space, θ2 represents the angle of incidence, and θ1 represents the angle of refraction. λ represents the spatial transmission phase gradient along the x-direction, and λ0 represents the wavelength of the optical signal.

[0112] Figure 10 (a) shows the propagation paths of refracted and reflected light when the spatial transmission phase gradient at the interface is 0. Figure 10 (b) shows the propagation paths of refracted and reflected light when the spatial transmission phase gradient at the interface is not zero.

[0113] Optionally, the microstructure and the first substrate are used to generate a spatial transmission phase in the tangential direction of the array of metasurface structures 210, to obtain a spatial transmission phase gradient, which is used to transmit the optical signal of each frequency band to the corresponding photoelectric conversion element of each frequency band. In the embodiments of this application, the transmission phase can also be referred to as the transmission phase.

[0114] The existence of the spatial transmission phase gradient enables the incident light signal to form a certain resonance effect with the metasurface structure 210. When light signals of different frequency bands pass through the metasurface structure 210, different transmission phase changes will occur in the metasurface structure 210, which can change the refraction angle of the light signal, that is, control the propagation direction of the light signal, and transmit the light signals of different frequency bands to the photoelectric conversion elements of different frequency bands.

[0115] Based on the positions of the photoelectric conversion elements corresponding to different frequency bands in the photoelectric conversion unit 220, the refraction angle of the light signal of each frequency band at each position of the metasurface structure 210, or the transmission direction of the light signal of each frequency band at each position, can be calculated, and thus the spatial transmission phase distribution of the metasurface structure 210 can be obtained.

[0116] The spatial transmission phase distribution is related to the wavelength of the optical signal in each frequency band, the position of the optical signal in each frequency band incident on the metasurface structure, and the position of the optical signal in each frequency band transmitted to the photoelectric conversion element corresponding to each frequency band.

[0117] Optionally, when the metasurface structure 210 and the photoelectric conversion unit 220 are not in direct contact, i.e., when a medium exists between the metasurface structure 210 and the photoelectric conversion unit 220, the spatial transmission phase distribution is also related to the refractive index of the medium between the metasurface structure 210 and the photoelectric conversion unit 220. In some cases, it can also be said that the spatial transmission phase distribution is related to the refractive index of the medium between the metasurface structure 210 and the photoelectric conversion unit 220. For example, when the medium between multiple photoelectric conversion elements in a photoelectric conversion unit 220 and the metasurface structure 210 is the same, the spatial transmission phase distribution is related to the refractive index of the medium between the metasurface structure 210 and the photoelectric conversion unit 220. This can be understood as the spatial transmission phase distribution being related to the refractive index of the medium between the metasurface structure 210 and the photoelectric conversion unit 220.

[0118] For example, the spatial transmission phase of the nth frequency band at a certain position on the metasurface structure 210 is related to the wavelength of the light signal of the nth frequency band, the coordinates of the position of the light signal of the nth frequency band transmitted to the photoelectric conversion element corresponding to the nth frequency band, and the refractive index of the medium between the metasurface structure 210 and the photoelectric conversion unit 220.

[0119] Optical signals experience phase differences due to varying optical paths during transmission. For any frequency band, a metasurface structure ensures that optical signals incident from a point on the metasurface structure at any location on the structure have the same phase when reaching the photoelectric conversion element. In other words, a metasurface structure can compensate for phase differences caused by different optical paths. For example, if the spatial transmission phase at position A on the metasurface structure is φ, the phase generated at position B on the photoelectric conversion element from position A is φ1. The distance between position C on the metasurface structure and position B on the photoelectric conversion element is the shortest, and the phase generated at position C on position B is φ0. The spatial transmission phase φ at position A satisfies:

[0120] φ=φ0-φ1

[0121] Specifically, for the nth frequency band, φ0 satisfies:

[0122]

[0123] For the nth frequency band, φ1 satisfies:

[0124]

[0125] Where, λ n f represents the wavelength of the optical signal in the nth frequency band. n This represents the focal length corresponding to the optical signal in the nth frequency band. This focal length is used to ensure that the optical signal in the nth frequency band is transmitted to the photosensitive position of the photoelectric conversion element corresponding to the nth frequency band.sub The refractive index of the medium between the metasurface structure 210 and the photoelectric conversion unit 220 is given, where C represents any phase. The focal length corresponding to the optical signal in the nth frequency band can be the perpendicular distance between the metasurface structure and the focal point corresponding to the optical signal in the nth frequency band.

[0126] For example, the focal point can be located on the photoelectric conversion element corresponding to the nth frequency band, or above the photoelectric conversion element corresponding to the nth frequency band, or below the photoelectric conversion element corresponding to the nth frequency band, as long as the light signal of the nth frequency band can be transmitted to the photosensitive area on the photoelectric conversion element corresponding to the nth frequency band.

[0127] Optionally, the spatial transport phase distribution φ(x,y,λ) of the metasurface structure 210 n )satisfy:

[0128]

[0129] Where φ(x,y,λ) n ) represents the phase distribution corresponding to each position and frequency band on the metasurface structure 210, x, y represent the coordinates on the metasurface structure 210, and λ n f represents the wavelength of the optical signal in the nth frequency band. n This represents the focal length corresponding to the optical signal in the nth frequency band. This focal length is used to ensure that the optical signal in the nth frequency band is transmitted to the photosensitive position of the photoelectric conversion element corresponding to the nth frequency band. f,n and y f,n The coordinates of the position where the optical signal of the nth frequency band is transmitted to the photoelectric conversion element corresponding to the nth frequency band are represented. sub The refractive index of the medium between the metasurface structure 210 and the photoelectric conversion unit 220 is given, where C represents any phase.

[0130] When the image sensor 200 includes a second substrate 230, the medium can be the second substrate 230.

[0131] For example, for such Figure 8 The color pixel unit shown in (a) Figure 11A schematic diagram of the spatial transport phase distribution of the metasurface structure 210 at different frequency bands is shown. The size of a photoelectric conversion element can be 1.6 μm * 1.6 μm, meaning the size of a photoelectric conversion unit 220 can be 3.2 μm * 3.2 μm, and the size of a metasurface structure 210 can be 3.2 μm * 3.2 μm. The thickness of the second substrate can be 15 μm. Light with a center wavelength of 650 nm in the red spectrum is focused at the center of photoelectric conversion element A, light with a center wavelength of 550 nm in the green spectrum is focused at the centers of photoelectric conversion elements B and C, and light with a center wavelength of 450 nm in the blue spectrum is focused at the center of photoelectric conversion element D. The material of the second substrate can be silicon dioxide glass with a refractive index n. sub =1.47~1.46, the obtained spatial transmission phase distribution is as follows Figure 11 As shown. Figure 11 (a) shows the spatial transmission phase distribution corresponding to a wavelength of 650 nm. Figure 11 (b) shows the spatial transmission phase distribution corresponding to a wavelength of 550 nm. Figure 11 (c) shows the spatial transmission phase distribution corresponding to a wavelength of 450 nm.

[0132] The above example only uses the center wavelength of each frequency band. For other frequencies, or other wavelengths, the corresponding spatial transmission phase distribution can also be calculated using the above formula.

[0133] For example, the center frequency of each frequency band can achieve maximum focusing efficiency, while the focusing efficiency of other frequencies within that band may be lower than that of the center frequency. In other words, the center frequency is focused onto the center position of the photoelectric conversion element corresponding to that frequency band, and other frequencies within that band need to be focused onto the corresponding photosensitive position on the photoelectric conversion element corresponding to that frequency band.

[0134] The transport phase change generated on the metasurface structure 210 is related to factors such as the size of the microstructure, the shape of the microstructure, the material of the microstructure, and the material of the first substrate.

[0135] Alternatively, the microstructure can be made of a low-loss dielectric material, such as titanium dioxide, gallium nitride, or silicon carbide.

[0136] Optionally, the first substrate can be made of a low-loss dielectric material, such as silicon dioxide, titanium dioxide, gallium nitride, or silicon carbide.

[0137] The solution provided in this application utilizes a metasurface structure to adjust the transmission direction of optical signals, transmitting the optical signal of each frequency band received by the entire metasurface structure to the corresponding photoelectric conversion element. It replaces the existing filtering method with a beam splitting approach, avoiding signal loss during the filtering process. Employing a rotationally symmetric structure with a rotation angle less than or equal to 90 degrees, it exhibits the same response to optical signals of different polarizations, eliminating polarization dependence and improving the light transmittance of each spectral channel. Overall, this improves the light utilization of the image sensor and enhances the imaging quality of the output image. For example, the polarization can include linear polarization and circular polarization. Compared to the Bayer color filter system, the solution in this application does not perform filtering. It uses an array of metasurface structures instead of a microlens array and Bayer color filters, that is, it uses a dichroic focusing scheme instead of a filtering focusing scheme, avoiding signal loss during the filtering process and fundamentally improving the light utilization of the image sensor and enhancing the imaging quality of the output image. Furthermore, in this embodiment, by increasing the number of different frequency bands corresponding to a photoelectric conversion unit, more spectral information can be obtained with less light utilization loss, thereby improving the spectral utilization of the image sensor, reducing the loss of color information in the image, increasing the color fidelity of the image, and improving the imaging quality.

[0138] Figure 12 This diagram illustrates a method 300 for fabricating an image sensor according to an embodiment of this application. Method 300 can be used to fabricate the image sensor 200 described in the foregoing embodiments of this application. To avoid unnecessary repetition, repeated descriptions are omitted below when introducing the method for fabricating the image sensor according to the embodiments of this application. Method 300 includes steps 310 to 320. Steps 310 to 320 are described in detail below.

[0139] 310, Fabrication of an array of photoelectric conversion units;

[0140] 320. An array of metasurface structures is fabricated on an array of photoelectric conversion units. The photoelectric conversion unit comprises multiple photoelectric conversion elements, each corresponding to a frequency band in the spectrum. The metasurface structure comprises a first substrate and a microstructure located above the first substrate. The microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band. The microstructure is a rotationally symmetric structure, and the rotation angle of the rotationally symmetric structure is less than or equal to 90 degrees.

[0141] For example, arrays of photoelectric conversion units and arrays of metasurface structures are integrated and fabricated using CMOS technology.

[0142] For example, step 320 may involve depositing a first substrate on an array of photoelectric conversion units and fabricating microstructures on the first substrate.

[0143] Optionally, the microstructure and the first substrate are used to generate a spatial transmission phase in the tangential direction of the array of metasurface structures to obtain a spatial transmission phase gradient, which is used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band.

[0144] Optionally, the image sensor may also include a second substrate.

[0145] For example, step 320 may involve depositing a second substrate on the array of photoelectric conversion units and fabricating an array of metasurface structures on the second substrate.

[0146] According to the scheme of this application embodiment, the integrated processing of the array of photoelectric conversion units and the array of metasurface structures can ensure a good alignment effect between the photoelectric conversion units and the metasurface structures, thereby improving the accuracy of the image sensor. The metasurface structure can transmit the optical signal of each frequency band received by the entire metasurface structure to the corresponding photoelectric conversion element. It uses a beam splitting method instead of the existing filtering method, and employs a rotationally symmetric structure with a rotation angle less than or equal to 90 degrees. This results in the same response to optical signals of different polarizations, eliminating polarization dependence and improving the light transmittance of each spectral channel, thus improving the overall light utilization rate of the image sensor.

[0147] Figure 13 This diagram illustrates a method 400 for fabricating an image sensor according to an embodiment of this application. Method 400 can be used to fabricate the image sensor 200 described in the preceding embodiments of this application. To avoid unnecessary repetition, repeated descriptions are omitted below when introducing the method for fabricating the image sensor according to the embodiments of this application. Method 400 includes steps 410 to 430. Steps 410 to 430 are described in detail below.

[0148] 410, Fabrication of an array of photoelectric conversion units.

[0149] 420, to prepare an array of metasurface structures.

[0150] 430. The array of the metasurface structure is assembled with the array of the photoelectric conversion units to obtain an image sensor. The photoelectric conversion unit includes multiple photoelectric conversion elements, each corresponding to a frequency band in the spectrum. The metasurface structure includes a first substrate and a microstructure located above the first substrate. The microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band. The microstructure is a rotationally symmetric structure, and the rotation angle of the rotationally symmetric structure is less than or equal to 90 degrees.

[0151] For example, an array of metasurface structures can be fabricated using CMOS technology and then assembled with an array of photoelectric conversion units.

[0152] For example, step 420 may be to deposit a first substrate in the array of metasurface structures, and to prepare microstructures in the array of metasurface structures on the first substrate.

[0153] Optionally, the microstructure and the first substrate are used to generate a spatial transmission phase in the tangential direction of the array of metasurface structures to obtain a spatial transmission phase gradient, which is used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band.

[0154] Optionally, the image sensor may also include a second substrate.

[0155] For example, step 430 may involve depositing a second substrate on an array of photoelectric conversion units, assembling the array of photoelectric conversion units including the second substrate with an array of metasurface structures, to obtain an image sensor.

[0156] According to the scheme of the embodiments of this application, the array of photoelectric conversion units and the array of metasurface structures are fabricated separately, and the fabrication process is relatively simple. The metasurface structure can transmit the optical signal of each frequency band received by the entire metasurface structure to the corresponding photoelectric conversion element. It uses a beam splitting method instead of the existing filtering method, and employs a rotationally symmetric structure with a rotation angle less than or equal to 90 degrees. This results in the same response to optical signals of different polarizations, eliminating polarization dependence and improving the light transmittance of each spectral channel, thus improving the overall light utilization rate of the image sensor.

[0157] Figure 14This diagram illustrates a design method 500 for an image sensor according to an embodiment of this application. Method 500 can be used to design the image sensor 200 described in the foregoing embodiments of this application. To avoid unnecessary repetition, repeated descriptions are omitted below when introducing the design method for the image sensor according to the embodiments of this application. The design method 500 includes steps 510 to 550. Steps 510 to 550 are described in detail below.

[0158] 510. Design the structure of the color pixel unit in an image sensor.

[0159] This structure can be as follows Figure 8 As shown in (a), an image sensor may include multiple color pixel units. A color pixel unit may include a photoelectric conversion unit and a metasurface structure. The bottom layer of a color pixel unit may be a photoelectric conversion unit. The photoelectric conversion unit may be an array of photoelectric conversion elements. Each photoelectric conversion element in the photoelectric conversion unit may correspond to a frequency band in the spectrum. The array of photoelectric conversion elements may be above the metasurface structure. That is, the metasurface structure may cover multiple photoelectric conversion elements.

[0160] The color pixel unit may also include a second substrate located between the photoelectric conversion unit and the metasurface structure. The second substrate can be used to support the metasurface structure.

[0161] 520. Determine the functional model of the metasurface structure. This means determining the location and number of spectral channels in the image sensor.

[0162] In a color pixel unit, a metasurface structure is used to focus light signals of different frequency bands onto the photosensitive positions of different photoelectric conversion elements. Determining the functional model of the metasurface structure means determining the frequency bands corresponding to the photoelectric conversion elements, the arrangement of the corresponding frequency bands, and the number of photoelectric conversion elements in the photoelectric conversion unit.

[0163] For example, the functional model of the metasurface structure can be determined according to imaging requirements. This means determining the frequency bands corresponding to the photoelectric conversion elements, the arrangement of these frequency bands, and the number of photoelectric conversion elements in the photoelectric conversion unit. For instance, the frequency bands corresponding to the photoelectric conversion elements may include red, green, and blue light. A photoelectric conversion unit may include four photoelectric conversion elements, each corresponding to one of the red, green, or blue light frequency bands. The frequency bands corresponding to the four photoelectric conversion elements can be arranged in an RGGB pattern, such as... Figure 8 As shown in (b), the metasurface structure can focus red, green, and blue light onto [the surface]. Figure 8 The photosensitive positions of the four photoelectric conversion elements in the middle.

[0164] The above are merely examples. If more spectral information is needed, the number of photoelectric conversion elements covered by the metasurface structure and the number of different frequency bands corresponding to these elements can be increased. The metasurface structure can be adaptively modified to obtain more spectral information. If information in other frequency bands is required, this can be achieved by changing the different frequency bands corresponding to the photoelectric conversion elements and adaptively modifying the metasurface structure. In other words, by changing the number of photoelectric conversion elements covered by the metasurface, the frequency bands corresponding to these elements, and the arrangement of these frequency bands, the design of the metasurface structure can be altered. The position of the beam-splitting and focusing mechanism of the metasurface structure can be modified according to the location of the spectral channels and the corresponding frequency bands to obtain more spectral information, thus meeting different imaging needs.

[0165] 530. Design a theoretical model for metasurface structures. The theoretical model of metasurface structures can also be understood as the spatial transport phase of metasurface structures.

[0166] Based on the functional model of the metasurface structure in step 520, the positions of the photoelectric conversion elements corresponding to different frequency bands in the photoelectric conversion unit can be determined, the refraction angle required for each frequency band of the light signal on the metasurface structure can be calculated, and the refraction angle corresponding to each frequency band of the light signal at each position of the metasurface structure, or the transmission direction corresponding to each frequency band of the light signal at each position, can be calculated. Thus, the spatial transmission phase distribution of the metasurface structure can be obtained.

[0167] The spatial transport phase distribution of metasurface structures can satisfy:

[0168]

[0169] Where φ(x,y,λ) n ) represents the phase distribution corresponding to each position and frequency band on the metasurface structure, x, y represent the coordinates on the metasurface structure, and λ n f represents the wavelength of the optical signal in the nth frequency band. n This represents the focal length corresponding to the optical signal in the nth frequency band. This focal length is used to ensure that the optical signal in the nth frequency band is focused on the photosensitive position of the photoelectric conversion element corresponding to the nth frequency band. f,n and y f,n The coordinates of the position where the optical signal of the nth frequency band is transmitted to the photoelectric conversion element corresponding to the nth frequency band are represented. sub The refractive index of the medium between the metasurface structure and the photoelectric conversion unit is represented by C, which is an arbitrary constant.

[0170] When the image sensor includes a second substrate, the medium can be the second substrate.

[0171] 540, designing metasurface structures, can also be described as designing metasurface structure units.

[0172] The metasurface structure can be designed based on the required spatial transport phase distribution on the metasurface structure obtained in step 530.

[0173] Metasurface structures can include a first substrate and microstructures. Designing a metasurface structure is essentially designing the first substrate and microstructures.

[0174] Specifically, the geometry of the microstructure can be designed based on the spatial transmission phase distribution. The microstructure is a rotationally symmetric structure with a rotation angle less than or equal to 90 degrees. For example, the microstructure can be cylindrical, prismatic, or cruciform. The material of the microstructure can also be designed; it can be a low-loss dielectric material such as titanium dioxide, gallium nitride, or silicon carbide. The material of the first substrate can also be designed. The substrate material can be a low-loss dielectric material such as titanium dioxide, gallium nitride, or silicon carbide.

[0175] The above method can be used to obtain multiple sets of first substrates and microstructures that satisfy the spatial transmission phase distribution required for the metasurface structure. Based on full-wave simulation, the transmission phase and transmittance of the metasurface structure at different frequencies can be obtained. Given that the spatial transmission phase distribution and transmission phase required in the theoretical model of step 530 are satisfied, the microstructure with the highest transmittance is selected as the final microstructure, thus obtaining the spatial distribution of the microstructure.

[0176] 550, Processing image sensors.

[0177] For example, an array of photoelectric conversion units can be prepared first, and then an array of metasurface structures can be prepared on the array of photoelectric conversion units.

[0178] For example, arrays of photoelectric conversion units and arrays of metasurface structures can be used, which are integrated and fabricated using CMOS technology.

[0179] For example, an array of photoelectric conversion units and an array of metasurface structures can be fabricated, and then the array of metasurface structures can be assembled with the array of photoelectric conversion units to obtain an image sensor. This is compatible with existing image sensor fabrication techniques.

[0180] For example, an array of metasurface structures can be fabricated using CMOS technology and then assembled with an array of photoelectric conversion units.

[0181] In this application, directional terms such as "center," "upper," "lower," "left," "right," "top," and "bottom" are defined relative to the orientation or position of the components shown in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and not to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. They can change accordingly depending on the orientation of the components in the accompanying drawings, and therefore should not be construed as limiting this application.

[0182] It should also be noted that in the embodiments of this application, the same reference numerals are used to represent the same component or part. For the same part in the embodiments of this application, the reference numerals may only be used to mark one part or component as an example. It should be understood that the reference numerals are also applicable to other identical parts or components.

[0183] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0184] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0185] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0186] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0187] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0188] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0189] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0190] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes: a Universal Serial Bus flash disk (USB flash disk, UFD), which can also be simply referred to as a USB flash drive, portable hard drive, read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk, and other media capable of storing program code.

[0191] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An image sensor, characterized in that, include: An array of metasurface structures, a dielectric material, and an array of photoelectric conversion units, wherein the array of metasurface structures is located above the dielectric material, and the dielectric material is located above the array of photoelectric conversion units. The photoelectric conversion unit includes multiple photoelectric conversion elements, each corresponding to a frequency band in the spectrum. The metasurface structure includes a first substrate and a microstructure located above the first substrate. The microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band. The microstructure is a rotationally symmetric structure with a rotation angle less than or equal to 90 degrees. The microstructure and the first substrate are used to generate a spatial transmission phase in the tangential direction of the array of the metasurface structure to obtain a spatial transmission phase gradient. The spatial transmission phase gradient is used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band. The spatial transmission phase is related to the wavelength of the optical signal of each frequency band, the position of the optical signal of each frequency band incident on the metasurface structure, the position of the optical signal of each frequency band transmitted to the photoelectric conversion element corresponding to each frequency band, and the refractive index of the medium between the metasurface structure and the photoelectric conversion element. The medium includes a second substrate.

2. The image sensor as described in claim 1, characterized in that, The spatial transmission phase φ(x,y,λ) n )satisfy: Where x, y represent the coordinates of the position on the metasurface structure, and λ n f represents the wavelength of the optical signal in the nth frequency band. n x represents the focal length corresponding to the optical signal in the nth frequency band. f,n and y f,n The coordinates of the position where the optical signal of the nth frequency band is transmitted to the photoelectric conversion element corresponding to the nth frequency band are represented. sub The refractive index of the medium between the metasurface structure and the photoelectric conversion unit is given, where C represents any phase.

3. The image sensor as described in claim 1 or 2, characterized in that, The microstructures include cylindrical structures, square column structures, or cross-shaped structures.

4. The image sensor as described in claim 1 or 2, characterized in that, The materials of the microstructure include titanium dioxide, gallium nitride, or silicon carbide.

5. The image sensor as described in claim 1 or 2, characterized in that, The plurality of photoelectric conversion elements correspond to V different frequency bands in the spectrum, where V is an integer greater than 3.

6. A method for fabricating an image sensor, characterized in that, The method includes: Fabrication of an array of photoelectric conversion units; An array of metasurface structures is fabricated on the array of photoelectric conversion units, wherein the array of metasurface structures is located above a dielectric material, which is located above the array of photoelectric conversion units. Each photoelectric conversion unit includes multiple photoelectric conversion elements, each corresponding to a frequency band in the spectrum. The metasurface structure includes a first substrate and a microstructure located above the first substrate. The microstructure and the first substrate are used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band. The microstructure is a rotationally symmetric structure, and the rotation angle of the rotationally symmetric structure is less than or equal to 9°. 0 degrees, wherein the microstructure and the first substrate are used to generate a spatial transmission phase in the tangential direction of the array of metasurface structures to obtain a spatial transmission phase gradient, the spatial transmission phase gradient being used to transmit the optical signal of each frequency band to the photoelectric conversion element corresponding to each frequency band, the spatial transmission phase being related to the wavelength of the optical signal of each frequency band, the position of the optical signal of each frequency band incident on the metasurface structure, the position of the optical signal of each frequency band transmitted to the photoelectric conversion element corresponding to each frequency band, and the refractive index of the medium between the metasurface structure and the photoelectric conversion element, the medium including the second substrate.

7. A method for fabricating an image sensor, characterized in that, The method includes: Fabrication of an array of photoelectric conversion units; Fabrication of arrays of metasurface structures; An image sensor is obtained by assembling the array of the metasurface structure with the array of the photoelectric conversion unit. The array of metasurface structures is located above a medium, which is located above an array of photoelectric conversion units. Each photoelectric conversion unit includes multiple photoelectric conversion elements, each corresponding to a frequency band in the spectrum. The metasurface structure includes a first substrate and a microstructure located above the first substrate. The microstructure and the first substrate are used to transmit optical signals of each frequency band to the corresponding photoelectric conversion element. The microstructure is a rotationally symmetric structure with a rotation angle less than or equal to 90 degrees. The microstructure and the first substrate are used to generate a spatial transmission phase along the tangential direction of the array of metasurface structures to obtain a spatial transmission phase gradient. This spatial transmission phase gradient is used to transmit optical signals of each frequency band to the corresponding photoelectric conversion element. The spatial transmission phase is related to the wavelength of the optical signal of each frequency band, the position of the optical signal incident on the metasurface structure, the position of the optical signal transmitted to the corresponding photoelectric conversion element, and the refractive index of the medium between the metasurface structure and the photoelectric conversion element. The medium includes a second substrate.

8. An electronic device, characterized in that, Including the image sensor as described in any one of claims 1 to 5.

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