Anamorphic Field Mapping for Back-Scanned Imager Blur Control
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Solution Overview
Problem
Existing optical designs for back-scanned and line-scanned imagers suffer from image blurring and reduced signal-to-noise ratio due to image wander of off-axis field points during exposure, particularly in two-dimensional imaging systems.
Innovation Solution
Implementing an optical imaging system with anamorphic field correcting elements that apply a non-rotationally symmetric field mapping, defined by θi = A mag θo and ϕi = A mag ϕo, to stabilize images on the focal plane array during back-scanning operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If back-scanning is used to increase integration time, then integration time is improved, but image wander and blur occur during exposure
Solution Approach 1:
The patent applies anamorphic field correcting elements that introduce non-rotationally symmetric field mapping to compensate for distortion. This asymmetric correction specifically addresses the differential wander of off-axis field points during back-scanning, allowing the system to maintain image fidelity while achieving extended integration time through the back-scan mirror's step/stare coverage.
2Area of moving object
If afocal telescope is used for back-scanned imagery, then field of view coverage is improved, but distortion characteristics cause field point wander
Solution Approach 1:
The patent introduces anamorphic field correcting elements at specific locations within the optical path (between the afocal telescope and the imaging sensor). These elements provide localized distortion correction tailored to the specific wander characteristics of off-axis field points, allowing the system to maintain both wide field of view coverage and field point stability during back-scanning operations.
3Device complexity
If conventional optical design is used, then system simplicity is maintained, but image blurring and reduced signal-to-noise ratio occur
Solution Approach 1:
The patent introduces anamorphic field correcting elements as intermediary components within the existing optical train. These elements act as mediators that correct the distortion introduced by the afocal telescope without requiring a complete redesign of the optical system. The correcting elements are positioned at convenient locations in the optical path and work in conjunction with existing components to eliminate image blur and improve signal-to-noise ratio while maintaining relatively simple system architecture.
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
Significantly reduces image wander and associated blur across all field points, maintaining high image fidelity and signal-to-noise ratio by controlling distortion characteristics.
Implementation Method 1
an anamorphic field correcting optical element configured to implement a non-rotationally symmetric field mapping to set distortion characteristics of the afocal optics
Implementation Method 2
a back-scan mirror positioned proximate the exit pupil of the afocal optics and between the afocal optics and the imager, and configured to perform the back-scan operation to stabilize the image on the imaging sensor
Implementation Method 3
afocal optics configured to receive the electromagnetic radiation and to direct the electromagnetic radiation via an exit pupil of the afocal optics to the imager
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
Optimal field mappings that provide the highest contrast images for back-scanned and time delay integration (TDI) imaging are given. The mapping can be implemented for back- scanned imaging with afocal optics including an anamorphic field correcting assembly configured to implement a non-rotationally symmetric field mapping between object space and image space to adjust distortion characteristics of the afocal optics to control image wander on a focal plane array. The anamorphic field correcting assembly can include one or more mirrors or lenses having non-rotationally symmetric aspherical departures. For optimal TDI imaging, anamorphic optics are also employed.