Image Sensor Shading Structures for Color Cross-Talk Reduction
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Solution Overview
Problem
Image sensor devices experience color cross-talk between adjacent pixels due to spatial asymmetry, leading to artifacts in the output image, particularly pronounced in pixels farther from the optical center.
Innovation Solution
Incorporating shading structures into the image sensor device to provide symmetrical angular responses to light, controlling the locations where light impinges on photodiode areas, thereby reducing or eliminating color cross-talk and artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If pixel multiplexing is used to increase photodiode area, then photodiode area and sensitivity are improved, but spatial asymmetry between adjacent pixels causes color cross-talk
Solution Approach 1:
The patent applies asymmetry by introducing shading structures with asymmetric patterns (e.g., different shading densities, positions, or geometries for different pixels) to compensate for the spatial asymmetry in pixel arrangement. This asymmetric shading design creates symmetrical angular responses by selectively blocking light paths that would otherwise cause color cross-talk between adjacent pixels with different spatial relationships to shared transistors and interconnects.
Solution Approach 2:
The shading structures serve as intermediary elements positioned between the color filters and photodiodes. These intermediaries selectively block or attenuate light paths that would cause color cross-talk, mediating the interaction between incident light and the photodiode while preserving the benefits of pixel multiplexing for increased photodiode area.
2Device complexity
If pixels are arranged with spatial asymmetry for multiplexing, then device complexity is reduced through shared transistors, but asymmetrical optical angular response produces color cross-talk
Solution Approach 1:
The patent introduces asymmetric shading structures that counterbalance the spatial asymmetry created by sharing transistors among adjacent pixels. By carefully designing the shading patterns to compensate for the unequal light paths to shared transistors and interconnects, the system maintains the simplified device architecture while eliminating the harmful asymmetrical optical angular response.
Solution Approach 2:
The shading structures are designed with local variations in shading density, position, or geometry tailored to each pixel's specific spatial relationship to shared transistors and interconnects. This localized customization of shading properties compensates for the asymmetrical light paths in different regions of the pixel array, reducing color cross-talk while preserving the benefits of transistor sharing.
3Ease of manufacture
If color filters follow translational symmetry, then manufacturing is simplified, but asymmetrical optical angular response results in artifacts in output image
Solution Approach 1:
The patent combines symmetric color filter patterns with asymmetric shading structures. The symmetric color filters maintain ease of manufacture through standard fabrication processes, while the asymmetric shading layers (added as separate structures) compensate for the optical asymmetry, achieving both manufacturing simplicity and angular response uniformity.
Solution Approach 2:
The optical control function is segmented into two independent components: symmetric color filters for spectral separation and asymmetric shading structures for angular response control. This segmentation allows each component to be optimized independently—the color filters for ease of manufacture and the shading structures for angular response uniformity—while working together to eliminate color cross-talk.
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 use of shading structures ensures symmetrical angular responses, significantly reducing color cross-talk and associated artifacts in the output image, maintaining color uniformity across the imaging array.
Implementation Method 1
one or more shading structures configured to provide a predetermined shading pattern to control locations at which light impinges on the photodiode areas of the pixels
Data Source
AI summary
An image sensor device formed in an integrated circuit (IC) with one or more shading structures configured to provide a predetermined shading pattern to control the locations at which light impinges on the photodiode areas of the pixels. The predetermined shading patterns preventing color cross-talk and providing the pixels with substantially symmetric angular responses to light to thereby eliminate or reduce the occurrence of artifacts in the output image produced by the image sensor device.