Stacked Image Sensor Color Separation Element Light Efficiency
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Solution Overview
Problem
Current color displays and image sensors using RGB or CYGM color filters suffer from low light use efficiency due to significant light absorption, with RGB filters transmitting only about 1/3 of incident light and absorbing 2/3, leading to substantial optical loss.
Innovation Solution
A stacked type image sensor employing a color separation element that directs different wavelength bands of light to specific pixels, using a transparent dielectric layer and color separation elements with a higher refractive index than the layer, allowing for efficient separation and transmission of light without obstructing the main propagation paths, thereby improving light use efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If color filters are used to detect colors of incident light, then color detection capability is improved, but light use efficiency deteriorates due to absorption of 2/3 of incident light
Solution Approach 1:
The incident light is segmented into different wavelength bands using a color separation element (prism or diffraction grating) that spatially separates colors. Each pixel then detects only its assigned wavelength band without filtering, eliminating the 2/3 light absorption loss while maintaining color detection capability through spectral separation rather than absorption-based filtering
Solution Approach 2:
A color separation element acts as an intermediary between incident light and the pixel array. This intermediary spatially separates different wavelength bands before they reach the pixels, allowing each pixel to detect its target wavelength band directly without requiring absorptive color filters, thus resolving the contradiction between color detection and light efficiency
2Adaptability or versatility
If RGB color filter scheme is used with green filters for two of four pixels, then color display capability is improved, but light transmission efficiency deteriorates to only 33%
Solution Approach 1:
The pixel array is segmented into different wavelength band detection regions, with each pixel assigned to detect a specific wavelength band. The color separation element directs different colors to different pixels spatially, eliminating the need for absorptive filters and achieving near 100% light transmission efficiency while maintaining full color display capability
Solution Approach 2:
The system changes the operational parameter from absorptive filtering to refractive/diffractive separation. By using the color separation element's refractive or diffractive properties to spatially separate wavelengths, the system achieves high light transmission efficiency while maintaining color detection versatility across all pixels
3Loss of energy
If color separation elements are introduced to improve light use efficiency, then light transmission efficiency is improved, but device complexity increases
Solution Approach 1:
The color separation function is added in the spatial dimension rather than requiring additional filtering layers in the vertical dimension. The color separation element spatially separates wavelengths in the horizontal plane, directing different colors to different pixel locations, which adds functionality without significantly increasing vertical device complexity
Solution Approach 2:
The color separation element serves multiple functions simultaneously: it separates wavelengths spatially, directs different colors to appropriate pixels, and enables all pixels to detect their assigned wavelength bands with high efficiency. This multi-functionality achieves high light transmission efficiency without proportionally increasing device complexity
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 enhances light use efficiency by allowing nearly all incident light to be detected without loss, improving the sensitivity and resolution of the image sensor across various wavelength bands, and simplifies the design and manufacturing of color separation elements.
Implementation Method 1
a color separation element 130 positioned between the first light sensing layer 140 and the second light sensing layer 110. The color separation elements 130 may be formed of a material having a refractive index greater than that of the transparent dielectric layer 120
Data Source
Figure 1~2A
Figure 2B~3
Figure 4~5
AI summary
A stacked type image sensor (100) with improved optical characteristics, which may result from a color separation element (130), and an image pickup apparatus including this image sensor. The stacked type image sensor includes first (140) and second (110) light sensing layers arranged in a stacked manner, and color separation elements (130) positioned between the first and second light sensing layers. Accordingly, the first light sensing layer absorbs and detects light of a first wavelength band, and the second light sensing layer detects light of second and third wavelength bands separated by the color separation elements.