Micro-Spectroscopic Image Sensor for High-Sensitivity Color Separation
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Solution Overview
Problem
Existing color image-capture elements face challenges with low light utilization efficiency, increased manufacturing costs, and polarization dependency due to the use of microstructures that separate incident light into two or three wavelength ranges, making it difficult to achieve high sensitivity and accurate color reproduction.
Innovation Solution
A color image-capture element with a two-dimensional pixel array and a two-dimensional spectroscopic element array, where microstructures with a higher refractive index than the transparent layer are used to separate incident light into three wavelength ranges, with columnar structures having equal length but different shapes, allowing for efficient light separation and reduced polarization dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If color filters are used for color separation, then color information can be obtained, but light utilization efficiency decreases to about 30%
Solution Approach 1:
The patent replaces the conventional color filter system (which absorbs light) with a microstructure-based optical system that uses refraction and diffraction to separate wavelengths. The microstructures guide different wavelength components to different pixel groups through geometric optics principles, achieving color separation without light absorption losses.
2Loss of energy
If spectroscopic elements like micro-prisms or dichroic mirrors are used to improve light utilization efficiency, then light loss is reduced, but integration on photoelectric conversion elements becomes difficult due to pixel miniaturization
Solution Approach 1:
The patent segments the pixel array into multiple pixel groups, with each group assigned to detect specific wavelength components. The microstructures are integrated directly into the substrate beneath the pixel groups, dividing the optical function into discrete, manufacturable units that can be produced using standard semiconductor fabrication processes.
Solution Approach 2:
The patent transitions from planar color filters to three-dimensional microstructures with specific geometries (prisms, gratings, or lens arrays) that exploit spatial dimensionality to separate wavelengths. These microstructures are formed within the substrate thickness dimension, enabling compact integration without increasing lateral footprint.
3Loss of energy
If microstructures are used to separate light into wavelength ranges, then light utilization efficiency improves, but manufacturing costs increase
Solution Approach 1:
The patent optimizes microstructure parameters (size, shape, spacing, refractive index) to achieve effective wavelength separation at scales compatible with standard semiconductor fabrication. By scaling the microstructure dimensions to sub-micrometer ranges and using conventional materials like silicon or glass with known refractive indices, the design leverages existing manufacturing capabilities.
Solution Approach 2:
The patent employs composite structures combining the substrate material with integrated microstructures, where the substrate itself serves as part of the optical system. This integration eliminates the need for separate, expensive optical components and allows the use of cost-effective materials that can be processed using standard fabrication techniques.
4Loss of energy
If conventional spectroscopic elements are used for color separation, then light utilization efficiency improves, but polarization dependency increases affecting color accuracy
Solution Approach 1:
The patent uses asymmetric microstructure geometries (such as triangular or trapezoidal prisms) that create wavelength-dependent refraction patterns independent of polarization state. The asymmetric shape ensures that the optical path difference between different wavelengths remains consistent regardless of the incident light's polarization orientation, eliminating polarization dependency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a high light utilization ratio and improved color reproducibility with simplified manufacturing, reducing polarization dependency and increasing image capturing sensitivity by effectively separating incident light into three wavelength ranges.
Implementation Method 1
each of the spectroscopic elements includes a set of microstructures composed of a plurality of microstructures formed of a material having a higher refractive index than a refractive index of the transparent layer... at least part of light incident on the spectroscopic elements is separated into first to third deflected lights that have different propagation directions according to their respective wavelengths
Implementation Method 2
the set of microstructures... are disposed at intervals equal to or shorter than a wavelength of incident light... at least part of light incident on the spectroscopic elements is separated into first to third deflected lights that have different propagation directions according to their respective wavelengths
Implementation Method 3
a two-dimensional pixel array in which a plurality of pixels each including a photoelectric conversion element are disposed on a substrate in a two-dimensional array
Data Source
AI summary
Provided is a highly-sensitive image-capture element and an image capture device that can be simply manufactured, have little polarization dependency, and have micro-spectroscopic elements capable of separating incident light into three wavelength ranges integrated facing a pixel array. An image capture element has a transparent layer having a low refractive index made of SiO2 or the like and a plurality of micro-lenses laminated on a pixel array in which pixels each including a photoelectric conversion element are disposed in an array. Inside the transparent layer having the low refractive index, micro-spectroscopic elements composed of a plurality of microstructures having constant thickness (length in a direction perpendicular to the pixel array) formed of a material such as SiN having a higher refractive index than that of the transparent layer is embedded.