Shortwave Infrared Polarimeter Using Pixelated Wire Grid Array
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Solution Overview
Problem
Current shortwave infrared polarimetry technologies face challenges in effectively distinguishing man-made objects from natural clutter in maritime environments due to limited contrast and reliance on ambient illumination, which restricts their usability, especially at night.
Innovation Solution
A shortwave infrared polarimeter (SWIP) incorporating a pixelated polarizer array with a wire grid polarizer and InGaAs focal plane array, optimized for wide spectral bandwidth and angular acceptance, allows interlaced imaging of different polarization states to enhance contrast and detectivity, particularly useful in maritime environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional intensity imaging is used in SWIR range, then the device can operate with simple sensors, but the ability to distinguish man-made objects from natural clutter is limited
Solution Approach 1:
The imaging device segments the detection function by separating intensity detection from polarization detection into different sensor arrays. The first sensor array detects intensity information while the second sensor array detects polarization state information, allowing each array to be optimized for its specific function and improving overall object detection capability without requiring a single complex sensor to perform all functions
Solution Approach 2:
The invention adds the polarization dimension to the traditional intensity-based imaging. By detecting both intensity and polarization state independently, the system extracts information from a new dimension that provides additional discrimination capability for distinguishing man-made objects from natural clutter, effectively transforming 2D intensity imaging into 4D imaging (x, y, intensity, polarization)
2Adaptability or versatility
If the polarimeter relies on ambient illumination, then the device can maintain simplicity in its illumination system, but it is primarily useful only during the day
Solution Approach 1:
The invention changes the operational parameters of the SWIR sensors to enable detection at lower light levels. By optimizing the sensors for SWIR range and utilizing the polarization detection capability which can extract information from low-light conditions, the system extends operational versatility to include nighttime use while maintaining the simplicity of relying on ambient illumination rather than active illumination systems
3Adaptability or versatility
If wire grid polarizers are used to achieve wide spectral bandwidth and angular acceptance, then the device can capture more polarization states, but the manufacturing precision requirements increase
Solution Approach 1:
The wire grid polarizers serve as intermediary optical elements that mediate between the incident SWIR radiation and the sensor arrays. By positioning the wire grid polarizers at the focal plane and using them to modulate the polarization state before detection, the system achieves wide spectral bandwidth and angular acceptance while the manufacturing tolerances can be managed through proper optical design and positioning
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 SWIP improves object detection by extracting more information from polarized images than conventional intensity imaging, effectively differentiating man-made objects from their natural backgrounds, even in low-light conditions, by leveraging the unique properties of shortwave infrared radiation.
Implementation Method 1
A shortwave infrared polarimeter (SWIP) incorporating a pixelated polarizer array with a wire grid polarizer
Implementation Method 2
InGaAs focal plane array
Implementation Method 3
A micro lens array is placed in close proximity to the PPA to form an image of the system aperture onto the InGaAs FPA
Implementation Method 4
The SWIR part of the optical spectrum scatters less from atmospheric aerosols than other wavelengths, so SWIR allows improved contrast in many situations for passive optical sensing
Data Source
AI summary
A short wave infrared polarimeter comprising a pixelated polarizer array and an Indium-Gallium-Arsenide (“InGaAs”) focal plane array. The short wave infrared polarimeter optionally includes a micro-lens array and/or an aperture layer.