MEMS Micro-Mirror Array Non-Uniformity Compensation
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Solution Overview
Problem
Imaging sensors face non-uniformity issues due to manufacturing defects and environmental variations, requiring frequent calibration to maintain uniform response across their field-of-view, which can be time-consuming and computationally demanding, especially in operational settings where scene visibility is crucial.
Innovation Solution
The integration of Micro-Electro-Mechanical System (MEMS) Micro-Mirror Arrays that can tip, tilt, and piston in multiple degrees of freedom, allowing for continuous control of optical elements to focus, blur, or re-direct radiation for calibration and operational modes, enabling on-board calibration without losing scene visibility and reducing computational demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional NUC calibration is performed using a black body source with mechanically gimballed mirror, then non-uniformity correction is achieved, but scene visibility is lost during calibration
Solution Approach 1:
The calibration function is segmented from the main imaging path by using a separate on-board black body source that can be selectively directed to the detector through the MEMS mirror array, allowing calibration without blocking the scene view during normal operation
Solution Approach 2:
The MEMS mirror array provides dynamic control over the optical path, enabling rapid switching between scene imaging and calibration modes by electronically steering the black body source radiation to the detector without mechanical movement of the entire calibration system
2Loss of time
If scene-based NUC is used to maintain scene visibility, then computational demands increase significantly
Solution Approach 1:
The system performs self-calibration by using its own on-board black body source and MEMS mirror array to generate uniform radiation patterns, eliminating the need for external computational algorithms to analyze scene images for non-uniformity correction
3Measurement precision
If frequent NUC calibration is performed to correct manufacturing defects and environmental variations, then operational efficiency decreases
Solution Approach 1:
The MEMS mirror array enables rapid, dynamic switching between calibration and imaging modes, allowing frequent calibration cycles with minimal interruption to operational efficiency by electronically controlling the calibration source direction rather than using slow mechanical systems
Solution Approach 2:
The system maintains continuous operational capability by performing calibration in brief intervals without complete loss of scene visibility, keeping the imaging function active while periodically inserting calibration measurements through the controllable MEMS optical path
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 solution allows for real-time non-uniformity correction and multi-spectral imaging, maintaining scene visibility during calibration, reducing computational load, and providing precise focus adjustments for aerodynamic and thermal variations, thus enhancing the sensor's operational efficiency and accuracy.
Implementation Method 1
the mirrors are tipped and tilted such that the optical radiation is focused at the pixelated detector to read out an image of the scene
Implementation Method 2
the mirrors are tipped and tilted and/or pistoned to spatially or temporally blur the image
Implementation Method 3
the mirrors are tipped and tilted and/or pistoned to spatially or temporally blur the image or to re-direct the FOV to one or more on-board calibration sources to generate a uniform image
Data Source
AI summary
A passive imaging sensor includes a plurality of optical elements in which at least one includes one or more Micro-Electro-Mechanical System (MEMS) Micro-Mirror Arrays (MMAs) having a plurality of independently and continuously controllable mirrors that at least tip and tilt in 2 DOF and may tip, tilt and piston in 3 DOF, In an operational mode, the mirrors are tipped and tilted, and possibly pistoned, such that the optical radiation is focused at the pixelated detector to read out an image of the scene. NUC coefficients such as offset and/or gain are applied to either the output signals of the detector or to the image to form the NUC'd images. In a calibration mode, the mirrors are tipped and tilted and/or pistoned to spatially or temporally blur the image or to re-direct the FOV to one or more on-board calibration sources to generate a uniform image from which to calculate and update the NUC coefficients.