Color polarization image sensor based on spectral routing metasurface

Abstract

The invention discloses a color polarization image sensor based on a spectrum routing metasurface, and belongs to the field of image detectors. According to the invention, a color focal plane polarization imaging detection technology is adopted, a superstructure surface with a double-layer structure is used to replace a commercial Bayer array optical filter and a micro-polarization array, and color and polarization information of light can be captured at the same time, so that details and contrast of an image are improved; and the polarization channel and the color channel complement each other, so that color imaging, polarization imaging and color polarization fusion imaging can be carried out in real time according to requirements. According to the method, light guidance and polarization detection are introduced by adopting spectrum routing, so that the object identification and classification capability is enhanced especially in a complex illumination environment, and the material and the surface state can be identified more accurately, thereby providing richer information. Finally, the improvement of the whole technology opens up a new possibility for scientific research and industrial application.

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] Metasurface is a two-dimensional surface composed of periodic or quasi-periodic arrangements of subwavelength-scale microstructures. It can produce local phase, amplitude, and polarization state control for light waves or other electromagnetic waves, and is widely used in many scenarios such as radar, imaging, data transmission and storage. Metasurfaces used in the field of image sensing can effectively replace traditional color filters. They can not only achieve compatibility with CMOS manufacturing processes, but also have the potential to improve optical efficiency and stability. Therefore, it has set off a research boom in academia and industry, especially the technology of using metasurfaces to achieve spatial light dispersion.

[0003] Polarization imaging technology uses polarization devices of different types and directions to collect polarization information reflected from the surface of an object. Through the polarization image obtained by the polarization imaging acquisition device, we can obtain more information than general optical imaging. Therefore, polarization imaging technology has important application prospects in the fields of material science, microscopic imaging, remote sensing and biomedicine. SONY's polarization image sensor creatively uses pixel quadrupole polarization filtering technology to polarize each pixel at four angles, presenting more polarization numbers and polarization angles, and is currently widely used in the market.

[0004] The ability to observe and utilize the multi-dimensional information of light is a long-standing pursuit of mankind. 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 fields, color polarization imaging technology that combines these two types of information has received increasing attention.

[0005] Traditional spectral and polarization imaging systems mainly rely on diffractive optical elements or optical filters, which are often bulky and heavy. At the same time, the current commercial color polarization cameras incorporate polarization elements into the spectral system - integrating the linear micropolarizer array into the RGB color filter in the traditional image sensor. Due to the limitations of the RGB color filter in the traditional image sensor, this method has spectral overlap between RGB channels and high crosstalk between different wavelengths of light between multiple pixels; at the same time, under low illumination conditions, there will be problems such as low light flux, poor imaging quality, and low signal-to-noise ratio.

[0006] The Bayer color filter array on which the traditional CMOS image sensor (CIS) is based is an organic dye three-color bandpass filter (RGB). This traditional organic color filter is not compatible with the CMOS process and needs to be deposited through a complex process before it can be used. At the same time, the color filter has poor stability and is easily decomposed in high temperature or radiation environments.

[0007] In existing color polarization cameras, each pixel has a polarization element, which causes different spectral responses at different wavelengths and reduces the imaging resolution. At the same time, there are still problems 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-illuminance imaging scenes.

[0009] The 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 includes a pixel sensor layer, a double-layer metasurface layer, and a microlens layer from bottom to top.

[0010] The pixel sensor layer is composed of N pixel basic units, 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 routing and a micro-polarization grating array formed on a semiconductor substrate. The sub-pixels of the double-layer metasurface layer correspond one-to-one to the sub-pixels of the pixel sensor layer. Among the four sub-pixels in a pixel block, three sub-pixels are spectral routing 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 four pixel blocks constitute a basic pixel unit of the double-layer metasurface; the spectral routings are R, G, and B pixels respectively, and the micro-polarization grating array of the basic pixel unit of the double-layer metasurface has four directions, namely 0°, 90°, 45°, and 135°, and each sub-pixel of the pixel sensor corresponds to the spectral routing 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, and 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 designated sub-pixel of the pixel sensor according to the wavelength, and the incident light is filtered through 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, and 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 using a double-layer metasurface to guide light and introduce polarization detection, the ability to identify 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 overall technological improvement opens up new possibilities for scientific research and industrial applications.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will 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 easily 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 provided 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) A schematic diagram of pixel blocks in four micro-polarization grating directions of a double-layer metasurface layer of an embodiment of the present invention;

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

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

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

[0027] Embodiments of the present invention are described in detail below, 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 should not 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 technology, especially in the field of machine vision and automated inspection, there is an urgent need for small-volume, low-cost, high-resolution color polarization cameras;

[0030] Improve imaging quality: By improving the utilization efficiency of incident light and introducing polarization imaging detection, it can effectively suppress background noise, highlight target details and improve imaging quality under low signal-to-noise ratio or low illumination conditions such as haze;

[0031] Promote interdisciplinary integration: It can promote the cross-integration of multiple disciplines such as physics, materials science, 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, 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, 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 routing and a micro-polarization grating array formed on a semiconductor substrate. The sub-pixels of the double-layer metasurface layer correspond one-to-one to the sub-pixels of the pixel sensor layer. Among the four sub-pixels in a pixel block, three sub-pixels are spectral routing 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 hollowed out, and four pixel blocks constitute a pixel basic unit of the double-layer metasurface; the spectral routings are R, G, and B pixels respectively, and the micro-polarization grating array of the pixel basic unit of the double-layer metasurface has four directions, namely 0°, 90°, 45°, and 135°, and each sub-pixel of the pixel sensor corresponds to the spectral routing 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 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.

[0036] The present invention adopts color split-focus plane polarization imaging detection technology and uses a double-layer metasurface to replace the commercial Bayer array filter and micro-polarization array. From bottom to top in the vertical direction, each sub-pixel includes a photodetector formed on a semiconductor substrate, and the sub-pixel corresponds to a spectral routing or a micro-polarization grating in a given direction.

[0037] By using the upper spectral routing, the incident light can be guided to the specified sub-pixel (R, G, B) according to the wavelength, effectively replacing the traditional color filter, thereby greatly improving the light utilization rate, and has great application potential in low-light imaging scenes. The incident light is filtered through the lower micro-polarization grating structure to obtain the polarization information of 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 (from upper left to lower right: RGGB), the G channel in the lower left corner is removed, and a single-direction micro-polarization grating is buried 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, and finally 4 pixel blocks form a pixel basic unit. In the 4*4 pixel basic unit, there will be 4 polarization channels, and 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 will be obtained in other channels, and the collected image data can be interpolated to perform color imaging and polarization imaging dual-channel imaging in real time; at the same time, color polarization images can also be obtained according to actual needs in combination with the back-end image fusion algorithm.

[0039] Furthermore, if Figure 5 As shown, the spectral router is titanium dioxide. The spectral router can adjust 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 scenes.

[0040] Optical selectivity of micro-polarization grating structure: The material of micro-polarization grating is aluminum. When the gap between the metal bars of micro-polarization grating is smaller than the wavelength of the incident light, when TE wave (wave with electric field perpendicular to the propagation direction) is incident, the electric field is consistent with the arrangement direction of metal wires, so it can effectively interact with the metal wires, causing the electric field energy to couple between metal wires, and thus be absorbed or reflected by the metal wire grid. For TM wave (wave with magnetic field perpendicular to the propagation direction), its magnetic field is perpendicular to the arrangement direction of metal wires, making it difficult to effectively couple with metal wires, so 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 sub-wavelength metal grating surface, surface plasmons are excited and mainly concentrated on the upper and lower surfaces of the metal grating layer. The metal grating slit through which the light wave passes is similar to a Fabry-Perot (FP) cavity, and its transmission enhancement is similar to the cavity mode resonance generated by the FP-like resonance effect. When the grating thickness is constant, the incident light of a specific wavelength meets the matching condition, which enhances the transmission of TM polarized light.

[0042] Polarization imaging is based on the fact that after light acts on an object, the polarization information carried by the light scattered by the object itself can be detected to form a polarization image. Using the split-focus plane polarization imaging method, sub-wavelength metal grating micro-polarizers in multiple polarization directions are integrated into the detector's pixels, realizing the simultaneous detection of polarization information in multiple polarization directions and the 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 the embodiment of the present invention can capture the color and polarization information of light at the same time, 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 and polarization fusion imaging in real time according to needs. By using 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.

[0044] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0045] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "N" is at least two, such as two, three, etc., unless otherwise clearly and 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, 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 routing and a micro-polarization grating array formed on a semiconductor substrate. The sub-pixels of the double-layer metasurface layer correspond one-to-one to the sub-pixels of the pixel sensor layer. Among the four sub-pixels in a pixel block, three sub-pixels are spectral routing 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 four pixel blocks constitute a basic pixel unit of the double-layer metasurface; the spectral routings are R, G, and B pixels respectively, and the micro-polarization grating array of the basic pixel unit of the double-layer metasurface has four directions, namely 0°, 90°, 45°, and 135°, and each sub-pixel of the pixel sensor corresponds to the spectral routing 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, and 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 designated sub-pixel of the pixel sensor according to the wavelength, and the incident light is filtered through 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 micro-polarization grating is made of 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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