Color and polarization image sensor based on spectral routing metasurface

Abstract

The present invention discloses a color polarization image sensor based on a spectral routing metasurface, which belongs to the field of image detectors. The present invention adopts color focal plane polarization imaging detection technology and uses a double-layer structured metasurface to replace the commercial Bayer array filter and micro-polarization array. The present invention can simultaneously capture the color and polarization information of light, thereby improving the details and contrast of the image; and the polarization channel and the color channel have complementary effects, and can perform color imaging, polarization imaging and color polarization fusion imaging in real time according to needs. By adopting spectral routing to guide light and introducing polarization detection, the ability to recognize and classify objects is enhanced, especially in complex lighting environments, and the material and surface state can be more accurately identified, thereby providing richer information. Ultimately, the improvement of the overall technology opens up new possibilities for scientific research and industrial applications.

Description

Technical Field

[0001] The present invention relates to the technical field of image sensors, and in particular to a color polarization image sensor based on a spectral routing metasurface. Background Art

[0002] Metasurfaces are two-dimensional surfaces composed of periodic or quasi-periodic arrangements of subwavelength-scale microstructures. They can locally manipulate the phase, amplitude, and polarization of light or other electromagnetic waves, and are widely used in radar, imaging, data transmission, and storage. Metasurfaces, when applied to image sensing, can effectively replace traditional color filters, achieving compatibility with CMOS manufacturing processes while also potentially improving optical efficiency and stability. This has sparked a wave of research in both academia and industry, particularly in the area of ​​using metasurfaces to achieve spatial light dispersion.

[0003] Polarization imaging technology utilizes polarization devices of different types and orientations to collect polarization information reflected from an object's surface. Polarization images captured by polarization imaging acquisition devices provide more information than conventional optical imaging, and therefore hold significant application prospects in fields such as materials science, microscopy, remote sensing, and biomedicine. Sony's polarization image sensors utilize innovative pixel quadrupole polarization filtering technology, polarizing each pixel at four different angles, resulting in a greater number of polarizations and angles. This technology is currently widely used in the market.

[0004] The ability to observe and utilize the multidimensional information of light has long been a human pursuit. It provides a more comprehensive understanding of the interaction between light and matter and promotes more accurate characterization in many fields. In recent years, with the advancement of science and technology and the expansion of application areas, color polarization imaging technology that combines these two types of information has gained increasing attention.

[0005] Traditional spectral and polarization imaging systems rely primarily on diffractive optical elements or optical filters, which are often bulky and heavy. Currently commercially available color polarization cameras incorporate polarization elements into spectral systems—integrating linear micropolarizer arrays into the RGB color filters of traditional image sensors. However, due to the limitations of the RGB color filters in traditional image sensors, this approach suffers from spectral overlap between RGB channels and high crosstalk between different wavelengths of light across multiple pixels. Furthermore, under low illumination conditions, this approach can lead to low light throughput, poor image quality, and low signal-to-noise ratio.

[0006] The Bayer color filter arrays used in traditional CMOS image sensors (CIS) are organic dye three-color bandpass filters (RGB). These traditional organic color filters are incompatible with CMOS processes and require complex deposition processes before they can be used. Furthermore, these filters have poor stability and are prone to decomposition in high-temperature or radiation environments.

[0007] In existing color polarization cameras, each pixel incorporates a polarization element, resulting in different spectral responses at different wavelengths and reduced imaging resolution. Furthermore, problems remain, such as complex optical system design and insufficient optical collection efficiency in complex environments. This limits the compactness of the system and makes real-time imaging quite challenging. Summary of the Invention

[0008] The present invention provides a color polarization image sensor based on a spectral routing metasurface, which improves light utilization and has great application potential in low-illumination imaging scenarios.

[0009] An embodiment of the present invention provides a color polarization image sensor based on a spectral routing metasurface. The color polarization image sensor has a three-layer structure, which comprises, from bottom to top, a pixel sensor layer, a double-layer metasurface layer, and a microlens layer.

[0010] The pixel sensor layer is composed of N pixel basic units, where N is a positive integer, each pixel basic unit includes 4 pixel blocks, each pixel block includes 4 sub-pixels, and each sub-pixel is composed of a photodetector formed on a semiconductor substrate;

[0011] The double-layer metasurface layer is a double-layer structure composed of a spectral router and a micro-polarization grating array formed on a semiconductor substrate. The sub-pixels of the double-layer metasurface layer correspond one-to-one with the sub-pixels of the pixel sensor layer. Among the four sub-pixels in a pixel block, three sub-pixels are spectral routers arranged in the upper layer, and one sub-pixel is a micro-polarization grating arranged in the lower layer. The upper layer of the micro-polarization grating is hollow, and the four pixel blocks constitute a basic pixel unit of the double-layer metasurface; the spectral routers are R, G, and B pixels respectively. The micro-polarization grating array of the basic pixel unit of the double-layer metasurface has four directions, namely 0°, 90°, 45°, and 135°. Each sub-pixel of the pixel sensor corresponds to the spectral router of the double-layer metasurface or a micro-polarization grating of a given direction.

[0012] In the microlens layer, one pixel block corresponds to one microlens. The microlens layer includes 4N microlenses. After the incident light passes through the microlenses, the spectral routing structure of the upper layer is used to guide the incident light to the designated sub-pixel of the pixel sensor according to the wavelength. The incident light is filtered by the micro-polarization grating array of the lower layer to obtain the polarization information of the detection object for imaging.

[0013] Optionally, in one embodiment of the present invention, the size of each sub-pixel is 1.1*1.1 um.

[0014] Optionally, in one embodiment of the present invention, the micro-polarization grating is made of aluminum.

[0015] Optionally, in one embodiment of the present invention, the spectral routing material is titanium dioxide.

[0016] The color polarization image sensor based on the spectral routing metasurface according to the embodiment of the present invention has the following beneficial effects:

[0017] 1. The present invention can simultaneously capture the color and polarization information of light, thereby improving the details and contrast of the image. The polarization channel and the color channel have complementary effects, and can perform color imaging, polarization imaging, and color and polarization fusion imaging in real time according to needs.

[0018] 2. By utilizing a dual-layer metasurface to guide light and introduce polarization detection, the ability to identify and classify objects is enhanced, particularly in complex lighting environments. This enables more accurate identification of materials and surface conditions, providing richer information. Ultimately, this overall technological advancement opens up new possibilities for scientific research and industrial applications.

[0019] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0021] Figure 1 A schematic diagram of a color polarization image sensor based on a spectral routing metasurface according to an embodiment of the present invention;

[0022] Figure 2 is a cross-sectional view of a color polarization image sensor based on a spectral routing metasurface according to an embodiment of the present invention;

[0023] Figure 3(a)-Figure 3(d) Schematic diagram of pixel blocks in four micro-polarization grating directions of a double-layer metasurface layer according to an embodiment of the present invention;

[0024] Figure 4 Schematic diagram of a basic pixel unit consisting of four pixel blocks of a double-layer metasurface according to an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of spectrum routing according to an embodiment of the present invention;

[0026] Figure 6 2 is a schematic diagram of the principle of light polarization imaging according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0028] Based on the defects of the background technology, the present invention proposes a color polarization image sensor based on a spectral routing metasurface for the following purpose.

[0029] Meeting market demand: With the growing market demand for advanced imaging technologies, especially in the fields of machine vision and automated inspection, there is an urgent need for small, low-cost, high-resolution color polarization cameras.

[0030] Improved imaging quality: By increasing the efficiency of incident light utilization and introducing polarization imaging detection, background noise can be effectively suppressed, highlighting target details and improving imaging quality under low-light conditions such as low signal-to-noise ratio or haze.

[0031] Promote interdisciplinary integration: It can promote the cross-integration of multiple disciplines such as physics, materials science, and computer science, and promote the overall progress of science and technology; it opens up new possibilities for future scientific research and application exploration.

[0032] like Figure 1 and Figure 2 As shown in the figure, the color polarization image sensor based on the spectral routing metasurface has a three-layer structure, which includes a pixel sensor layer, a double-layer metasurface layer, and a microlens layer from bottom to top.

[0033] The pixel sensor layer is composed of N pixel basic units, where N is a positive integer, each pixel basic unit includes 4 pixel blocks, each pixel block includes 4 sub-pixels, and each sub-pixel is composed of a photodetector formed on a semiconductor substrate;

[0034] The double-layer metasurface layer is a double-layer structure composed of a spectral router and a micro-polarization grating array formed on a semiconductor substrate. The sub-pixels of the double-layer metasurface layer correspond one-to-one with the sub-pixels of the pixel sensor layer. Among the four sub-pixels in a pixel block, three sub-pixels are spectral routers set in the upper layer, and one sub-pixel is a micro-polarization grating set in the lower layer. The upper layer of the micro-polarization grating is hollow, and the four pixel blocks constitute a basic pixel unit of the double-layer metasurface; the spectral routes are R, G, and B pixels respectively. The micro-polarization grating array of the basic pixel unit of the double-layer metasurface has four directions, namely 0°, 90°, 45°, and 135°. Each sub-pixel of the pixel sensor corresponds to the spectral router of the double-layer metasurface or a micro-polarization grating of a given direction.

[0035] In the microlens layer, one pixel block corresponds to one microlens. The microlens layer includes 4N microlenses. After the incident light passes through the microlens, the spectral routing structure of the upper layer is used to guide the incident light to the specified sub-pixel of the pixel sensor according to the wavelength. The incident light is filtered by the micro-polarization grating array of the lower layer to obtain the polarization information of the detection object used for imaging.

[0036] This invention utilizes color-focused plane polarization imaging detection technology, employing a dual-layer metasurface to replace commercial Bayer array filters and micropolarization arrays. Working vertically from bottom to top, each subpixel includes a photodetector formed on a semiconductor substrate, and above that subpixel is a corresponding spectral routing or micropolarization grating with a given orientation.

[0037] By utilizing the upper layer's spectral routing, incident light can be directed to specific sub-pixels (R, G, B) based on wavelength, effectively replacing traditional color filters. This significantly improves light utilization and has great potential for application in low-light imaging scenarios. The lower layer's micro-polarization grating structure filters the incident light to obtain polarization information about the detected object.

[0038] Specifically, each 4*4 sub-pixel constitutes a pixel block, and the size of a single sub-pixel is 1.1*1.1um. Based on the spectral splitting of the classic Bayer array arrangement (RGGB from upper left to lower right), the G channel in the lower left corner is removed, and a unidirectional micro-polarization grating is embedded in the lower layer of the channel. Each micro-polarization grating is combined with the spectral routing structure to form a 2*2 pixel block. Finally, 4 pixel blocks form a pixel basic unit. The 4*4 pixel basic unit will contain 4 polarization channels. The polarization angles of the polarization channels are 0°, 45°, 135°, and 90° from upper left to lower right, as shown in Figures 3(a), 3(b), 3(c), 3(d), and Figure 4At the same time, RGB color information without polarization information is obtained in other channels. Interpolation calculations are performed on the collected image data to perform real-time color imaging and polarization imaging dual-channel imaging. At the same time, color polarization images can also be obtained based on actual needs by combining the back-end image fusion algorithm.

[0039] Furthermore, if Figure 5 As shown, the spectral router is titanium dioxide. The spectral router can regulate the phase of the incident light according to the wavelength of the incident light and guide it to the specified sub-pixel of the pixel sensor, thereby greatly improving the light utilization rate (theoretically up to 100%) and has great application potential in low-light imaging scenarios.

[0040] The optical selectivity of the micro-polarization grating structure: The micro-polarization grating is made of aluminum. When the gap size between the metal grating bars of the micro-polarization grating is smaller than the wavelength of the incident light, when TE waves (waves with an electric field perpendicular to the propagation direction) are incident, the electric field aligns with the arrangement direction of the metal wires, allowing them to effectively interact with the metal wires, resulting in the electric field energy coupling between the metal wires and being absorbed or reflected by the metal wire grid. However, for TM waves (waves with a magnetic field perpendicular to the propagation direction), their magnetic field is perpendicular to the arrangement direction of the metal wires, making it difficult for them to effectively couple with the metal wires. Therefore, most TM waves can pass through the metal wire grid smoothly.

[0041] At the same time, due to the surface plasmon resonance effect, when photons act on the surface of a subwavelength metal grating, surface plasmons are excited, primarily concentrated on the upper and lower surfaces of the metal grating layer. The slits of the metal grating through which the light wave passes resemble a Fabry-Perot (FP) cavity, and the transmission enhancement is similar to the cavity mode resonance generated by the FP-like resonance effect. When the grating thickness is constant, incident light of a specific wavelength meets the matching condition, enhancing the transmission of TM polarized light.

[0042] Polarization imaging is based on the fact that after light strikes an object, the polarization information carried by the light scattered from the object itself can be detected to form a polarization image. Using the split-focal plane polarization imaging method, sub-wavelength metal grating micro-polarizers in multiple polarization directions are integrated into the detector's pixel, achieving simultaneous detection of polarization information in multiple polarization directions and miniaturization of the polarization detection system, such as Figure 6 shown.

[0043] The color polarization image sensor based on the spectral routing metasurface proposed in accordance with an embodiment of the present invention can simultaneously capture the color and polarization information of light, thereby improving image detail and contrast. The polarization channel and color channel complement each other, enabling real-time color imaging, polarization imaging, and color and polarization fusion imaging as needed. By using spectral routing to guide light and introducing polarization detection, the ability to identify and classify objects is enhanced, particularly in complex lighting environments, enabling more accurate identification of materials and surface conditions, thereby providing richer information. Ultimately, the overall technological advancement opens up new possibilities for scientific research and industrial applications.

[0044] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0045] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "N" means at least two, such as two, three, etc., unless otherwise specifically defined.

Claims

1. A color polarization image sensor based on a spectral routing metasurface, characterized in that: The color polarization image sensor has a three-layer structure, which includes a pixel sensor layer, a double-layer metasurface layer, and a microlens layer from bottom to top. The pixel sensor layer is composed of N pixel basic units, where N is a positive integer, each pixel basic unit includes 4 pixel blocks, each pixel block includes 4 sub-pixels, and each sub-pixel is composed of a photodetector formed on a semiconductor substrate; The double-layer metasurface layer is a double-layer structure composed of a spectral router and a micro-polarization grating array formed on a semiconductor substrate. The sub-pixels of the double-layer metasurface layer correspond one-to-one with the sub-pixels of the pixel sensor layer. Among the four sub-pixels in a pixel block, three sub-pixels are spectral routers arranged in the upper layer, and one sub-pixel is a micro-polarization grating arranged in the lower layer. The upper layer of the micro-polarization grating is hollow, and the four pixel blocks constitute a basic pixel unit of the double-layer metasurface; the spectral routers are R, G, and B pixels respectively. The micro-polarization grating array of the basic pixel unit of the double-layer metasurface has four directions, namely 0°, 90°, 45°, and 135°. Each sub-pixel of the pixel sensor corresponds to the spectral router of the double-layer metasurface or a micro-polarization grating of a given direction. In the microlens layer, one pixel block corresponds to one microlens. The microlens layer includes 4N microlenses. After the incident light passes through the microlenses, the spectral routing structure of the upper layer is used to guide the incident light to the designated sub-pixel of the pixel sensor according to the wavelength. The incident light is filtered by the micro-polarization grating array of the lower layer to obtain the polarization information of the detection object for imaging.

2. The color polarization image sensor based on spectral routing metasurface according to claim 1, characterized in that: The size of each sub-pixel is 1.1*1.1um.

3. The color polarization image sensor based on spectral routing metasurface according to claim 1, characterized in that: The material of the micro-polarization grating is aluminum.

4. The color polarization image sensor based on spectral routing metasurface according to claim 1, characterized in that: The spectral routing is titanium dioxide.

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