Spectral Element Array for Filterless Image Sensor Color Splitting
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Solution Overview
Problem
Conventional color image sensors suffer from low light utilization efficiency due to the use of color filters, which limits their sensitivity and results in reduced spatial resolution uniformity, especially as pixel sizes decrease.
Innovation Solution
The implementation of a two-dimensional spectroscopic element array within a transparent layer on top of a pixel array, where each spectroscopic element splits incident light into four different transmission directions based on wavelength, allowing adjacent pixels to detect light in distinct wavelength regions without the need for color reconfiguration through signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If color filters are used for color splitting in each pixel, then color information can be acquired, but light utilization efficiency is reduced to about one-third due to absorption and reflection losses
Solution Approach 1:
The patent replaces the conventional color filter system (which relies on absorption and reflection) with a microlens-based color splitting system. The microlens array directs different wavelength components of light to different photoelectric conversion elements through geometric optics, eliminating the energy losses associated with absorption and reflection in color filters. This substitution of the optical mechanism achieves both high light utilization efficiency and maintained image sensor sensitivity.
2Loss of energy
If spectroscopic elements such as prisms or dichroic mirrors are used to branch incident light by wavelength band, then light utilization efficiency is significantly improved, but integration on photoelectric conversion elements becomes difficult as pixels become smaller
Solution Approach 1:
The patent divides the color splitting function into multiple microlenses arranged in a specific pattern above each pixel. Each microlens is responsible for directing a specific wavelength band to the appropriate photoelectric conversion element. This segmentation of the optical function into discrete, miniaturizable microlens units enables integration on small-pixel photoelectric conversion elements while maintaining the high light utilization efficiency of spectroscopic elements.
Solution Approach 2:
The patent transitions from planar color filters to a three-dimensional microlens array structure. The microlenses are positioned at different heights and angles above the photoelectric conversion elements, creating a vertical dimension for light path control. This dimensional transition enables effective color splitting and wavelength-based light directing in a compact format suitable for small pixels.
3Manufacturing precision
If pixels are made smaller to increase image resolution, then spatial resolution is improved, but the amount of light received by one pixel decreases, limiting sensitivity
Solution Approach 1:
The patent extracts the color filtering function from the pixel plane and implements it in the optical path above the pixels using microlenses. This allows the photoelectric conversion elements to be made smaller for higher resolution without the constraint of needing large-area color filters, while still receiving sufficient light through the efficient microlens-based light directing system.
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
This approach enhances the sensitivity of the image sensor by increasing light utilization efficiency and maintains uniform spatial resolution across the image, while being compatible with existing production processes and pixel arrangements like the Bayer arrangement.
Implementation Method 1
Microlenses 103 are arranged on the color filters 104. When light enters from the microlens 103...
Implementation Method 2
the color filter 104 is used to allow only light of a desired wavelength band to pass through, and to absorb or reflect light of an unnecessary wavelength band
Implementation Method 3
photoelectric conversion elements 102 are arranged on electrical wiring 112... signals are acquired from three photoelectric conversion elements 102
Implementation Method 4
the incident light is split into light that goes straight and light that is deflected to the left and right depending on the wavelength region by micro beam structures 206-1 and 206-2, which are arranged corresponding to pixels
Implementation Method 5
This is because the phase delay effect felt by the incident light in and around the micro beam structures is significantly different in one wavelength region and almost equal in another wavelength region
Data Source
AI summary
An image sensor includes a two-dimensional pixel array in which a plurality of pixels including photoelectric conversion elements are arranged in the form of an array on a substrate, a transparent layer formed on the two-dimensional pixel array, and a two-dimensional spectroscopic element array in which a plurality of spectroscopic elements are arranged in the form of an array inside or on the transparent layer. Each spectroscopic element includes a plurality of microstructures having a higher refractive index than a refractive index of the transparent layer. The plurality of microstructures have a microstructure pattern. Each of the spectroscopic elements splits incident light into first to fourth deflected lights, which have different transmission directions, according to the wavelength region. First to fourth pixels, which are adjacent to each other and are located directly below each of the spectroscopic elements, respectively detect the first to fourth deflected lights.