Dual-mode Image Sensor Signal-Separating Color Filter Array
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Solution Overview
Problem
Conventional dual-mode visible-infrared (VIS-IR) CMOS image sensors face image quality degradation due to IR contamination, which is difficult to address with existing methods that require masking or patterning of IR-cut filters, especially as pixel dimensions become smaller.
Innovation Solution
A signal-separating color filter array (CFA) with multi-height spectral filters and pixel-localized IR-cut filters is used, where IR-pass filters are taller than visible spectral filters, and single-layer blocking filters are disposed on short spectral filters to block IR wavelengths without masking or patterning, allowing for effective IR contamination reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single continuous IR-cut filter is used across the entire pixel array, then IR contamination is blocked, but IR light cannot reach IR pixels
Solution Approach 1:
The IR-cut filter is segmented into discrete pixel-level filters rather than a continuous filter across the entire array. Each pixel receives an IR-cut filter except IR pixels, allowing selective IR blocking for color pixels while preserving IR transmission for IR pixels.
Solution Approach 2:
Different filtering properties are applied to different regions: color pixels receive IR-cut filters to block IR contamination, while IR pixels remain without IR-cut filters to allow IR light transmission. This local differentiation resolves the contradiction between blocking IR for color imaging and allowing IR for IR imaging.
2Object-affected harmful factors
If masking or patterning processes are used to create pixel-level IR-cut filters, then IR contamination is reduced, but manufacturing complexity increases
Solution Approach 1:
The substrate is pre-configured with regions having different properties (e.g., different silicon thickness or material composition) that inherently allow or block IR transmission. This preliminary structuring eliminates the need for complex masking and patterning processes during filter fabrication, as the pixel-type-specific filtering capability is built into the substrate itself.
Solution Approach 2:
Complex mechanical masking and patterning processes are replaced by a simpler filter deposition process. The filter layer is deposited uniformly, and the pixel-level selectivity is achieved through the underlying substrate structure rather than through complex mechanical patterning steps.
3Area of moving object
If pixel dimensions are reduced, then sensor integration density increases, but masking and patterning become more difficult
Solution Approach 1:
The patent replaces complex mechanical masking and patterning processes with a simpler filter deposition approach. By using a uniform filter layer combined with substrate-level differentiation, the manufacturing process becomes less sensitive to pixel size reductions, allowing higher integration density without proportionally increasing manufacturing difficulty.
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 eliminates the need for complex masking or patterning processes, ensuring reduced IR contamination and improved image quality by aligning filter heights and using materials like Color Mosaic materials for effective IR blocking, maintaining image sensor efficiency and accuracy.
Implementation Method 1
a plurality of single-layer blocking filters for blocking the first electromagnetic wavelength range... Each single-layer blocking filter... has a combined height substantially equal to the first height
Implementation Method 2
Each spectral filter is disposed on the substrate and aligned with a respective one of the plurality of photodiode regions... transmitting a first electromagnetic wavelength range
Implementation Method 3
a substrate including a plurality of photodiode regions... aligned with a respective one of the plurality of photodiode regions
Data Source
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AI summary
A dual-mode image sensor (300) with a signal-separating CFA (334) includes a substrate (320) including a plurality of photodiode regions (322) and a plurality of tall spectral filters (391) having a uniform first height and for transmitting a first electromagnetic wavelength range. Each of the tall spectral filters is disposed on the substrate and aligned with a respective photodiode region. The image sensor also includes a plurality of short spectral filters (314) for transmitting one or more spectral bands within a second electromagnetic wavelength range. Each of the short spectral filters is disposed on the substrate and aligned with a respective photodiode region. The image sensor also includes a plurality of single-layer blocking filters (390) for blocking the first electromagnetic wavelength range. Each single-layer blocking filter is disposed on a respective short spectral filter. Each single-layer blocking filter and its respective short spectral filter have a combined height substantially equal to the first height.