Diamond-Shaped Color Filter Array for Infrared Imaging
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Solution Overview
Problem
Conventional CMOS image sensors with Bayer pattern color filter arrays face issues of reduced resolution and color aliasing when additional non-visible filters are used, which decrease the number of visible pixels and result in incorrect color representation in images.
Innovation Solution
The use of diamond-shaped filters in a color filter array, where the filters are arranged in a rhombic pattern with minimal repeating units, allows for the inclusion of non-visible filters without reducing the resolution, maintaining full-resolution color imaging and enabling near-full-resolution infrared imaging by assigning specific spectral photoresponses to each pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional non-visible filters are used in the color filter array, then sensitivity for non-visible wavelengths is improved, but resolution is reduced and color aliasing occurs
Solution Approach 1:
The patent transitions from a conventional square grid arrangement to a diamond-shaped filter arrangement, effectively changing the spatial dimension and orientation of the filter array. This dimensional change allows non-visible filters to be integrated without reducing the number of visible pixels, thereby maintaining resolution while adding non-visible wavelength sensitivity.
Solution Approach 2:
The patent employs flexible assignment of spectral photoresponses to diamond-shaped filter groups, allowing dynamic configuration of filter functions. This enables the system to adaptively assign different spectral responses (visible and non-visible) to different diamond groups, optimizing both resolution and multi-wavelength sensitivity without fixed constraints.
2Measurement precision
If additional non-visible filters are used in the color filter array, then sensitivity for non-visible wavelengths is improved, but color aliasing occurs
Solution Approach 1:
The patent segments the color filter array into multiple diamond-shaped filter groups, where each group can be independently assigned spectral photoresponses. This segmentation allows non-visible filters to be distributed across specific diamond groups without interfering with the color accuracy of other groups, thereby preventing color aliasing while maintaining non-visible wavelength sensitivity.
Solution Approach 2:
The patent applies different spectral photoresponse assignments to different local regions (diamond groups) of the filter array. By assigning non-visible spectral responses to specific diamond groups and visible spectral responses to others, the system achieves local optimization where each region serves its designated function without causing color aliasing in other regions.
3Measurement precision
If non-visible filters decrease the number of visible pixels, then non-visible wavelength detection is improved, but visible color imaging resolution is reduced
Solution Approach 1:
The patent creates a universal filter array structure where diamond-shaped filter groups can serve multiple functions. Each diamond group can be assigned different spectral photoresponses (visible or non-visible) depending on the imaging requirements, allowing the same physical structure to support both visible color imaging at full resolution and non-visible wavelength detection simultaneously.
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 prevents color aliasing and maintains full-resolution color imaging while allowing for full-resolution or near-full-resolution infrared imaging, essential in applications like biometric iris recognition, without the need for complex interpolation algorithms.
Implementation Method 1
Each pixel is assigned a spectral photoresponse selected from a set of spectral photoresponses, each spectral photoresponse having a different spectral sensitivity
Data Source
AI summary
Embodiments are described of a color filter array including a plurality of tiled minimal repeating units. Each minimal repeating unit includes a primary set of four rhombic color filters positioned so that at least two vertices of each rhombic color filter contact a vertex of an adjoining rhombic color filter and so that the four rhombic filters form a central interstitial space and four peripheral interstitial spaces, wherein the primary set includes at least one color filter with a first spectral photoresponse, at least one color filter with a second spectral photoresponse, and at least one color filter with a third spectral photoresponse. Each minimal repeating unit also includes a secondary set of rhombic filters, the secondary set comprising a rhombic filter positioned in the central interstitial space and rhombic filters positioned in three of the four peripheral interstitial spaces, wherein the rhombic filters in the secondary set have a fourth spectral photoresponse different than any of the first, second, and third spectral photoresponses.