Patterned Spectral Filter Attachment for MWIR Sensor
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Solution Overview
Problem
Current methods for improving mid-wavelength infrared (MWIR) sensor performance are complex and costly, particularly in achieving spectral discrimination without significant modifications to existing focal plane array (FPA) designs.
Innovation Solution
A method involving the attachment of a patterned spectral filter in close proximity to the FPA, allowing for color selective pixels that enable spectral discrimination without altering the FPA design, optics, or fabrication processes, using a checkerboard or other patterned band-pass filters with anti-reflective coatings for improved spectral and polarization discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral filters or micro lenses are added to FPAs to improve spectral discrimination and MTF performance, then detection capability is improved, but device complexity and cost increase
Solution Approach 1:
A spectral filter array is introduced as an intermediary component positioned between the scene and the FPA detector. This filter array performs the spectral discrimination function externally, allowing the existing FPA to maintain its simple structure while achieving enhanced spectral detection capability through the intermediary filtering layer.
Solution Approach 2:
The spectral filtering function is segmented from the FPA detector itself and implemented as a separate, removable filter array. Each filter in the array corresponds to specific spectral bands, allowing independent optimization of filter properties without modifying the FPA structure. This segmentation enables spectral discrimination while keeping the detector design simple and modular.
2Adaptability or versatility
If multiple wavelengths are integrated within the same unit cell to broaden detection capability, then spectral range is improved, but manufacturing yield decreases due to complex semiconductor processing
Solution Approach 1:
Instead of integrating multiple wavelength detectors in the same unit cell, the invention segments the spectral detection into separate spatial locations on the FPA. Each pixel or group of pixels is paired with specific spectral filters, allowing the FPA to detect multiple spectral bands without requiring complex multi-wavelength semiconductor processing. This approach maintains high production yield while achieving broad spectral coverage.
Solution Approach 2:
The invention transitions from integrating multiple wavelengths in the same spatial unit (vertical integration in semiconductor layers) to distributing different wavelength detections across different spatial locations on the FPA surface. This dimensional shift from vertical to lateral arrangement simplifies manufacturing while achieving multi-spectral capability.
3Measurement precision
If beam splitters and multiple detectors are used to achieve spectral discrimination with sub 10th pixel accuracy, then spectral separation is improved, but device complexity and alignment precision requirements increase
Solution Approach 1:
A spectral filter array serves as an intermediary optical element that performs spectral separation before light reaches the FPA detector. This eliminates the need for complex beam splitters and multiple detectors with sub-pixel alignment requirements. The filter array provides passive, contactless spectral discrimination that is much simpler to implement and align.
Solution Approach 2:
Instead of using a single complex optical path with beam splitters, the invention creates multiple spectral copies that are spatially separated and directed to different pixel regions on the FPA. Each pixel or pixel group receives a specific spectral copy through the filter array, achieving spectral separation without complex optical routing.
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 enables cost-effective, high-yield production of MWIR sensors with enhanced spectral discrimination capabilities, allowing consistent detection across the entire sensor for improved target tracking and reduced production costs.
Implementation Method 1
A 2 Color MWIR sensor is manufactured by making a patterned close proximity spectral filter and attaching the filter to a focal plane array (FPA), which creates a detector capable of 2 color spectral discrimination in the MWIR band
Implementation Method 2
A preferred embodiment of a multi-color detector according to the present invention is a 2 color mid-wavelength infrared (MWIR) sensor
Data Source
AI summary
The present invention relates generally to a method and apparatus for attaching a close proximity filter to an FPA (focal plane array) and more particularly, to a method and apparatus that allows improved spectral discrimination of a mid-wave infra red (MWIR) detector by applying an improved multi-color filter to a focal plane array (FPA), while employing existing production equipment and techniques to reduce cost and improve production yield.