Earth Observation Scanning with Stepped Across-Track Imaging
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Solution Overview
Problem
Aerial imaging systems face a trade-off between resolution and field of view, with physical limitations on optics and detector technology hindering the ability to image large areas of the earth at high resolution without large, heavy systems.
Innovation Solution
An earth observation apparatus with an optical train and image sensor that uses a view adjuster to provide forward motion compensation and displace the image in across-track direction in discrete steps, allowing for a sparse sampling of image data using area array detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focal length is increased to improve resolution, then resolution is improved, but optical system size and weight increase
Solution Approach 1:
The patent employs dynamic scanning of the focal plane using a detector array that sequentially samples different regions. This allows a smaller optical system to achieve the effective resolution of a larger system by temporally multiplexing the detection of fine spatial details across multiple detector elements during the integration period.
Solution Approach 2:
The invention transitions from static spatial sampling to temporal-spatial sampling by introducing the time dimension. The detector array scans through different spatial positions over time, effectively synthesizing a larger aperture through temporal integration rather than requiring a physically larger optical system.
2Measurement precision
If aperture is increased to maintain f-number, then resolution is improved, but optical system volume increases
Solution Approach 1:
The patent uses dynamic scanning of the focal plane to effectively synthesize a larger aperture. By sequentially sampling different spatial frequencies and angles during the integration period, the system achieves the resolution enhancement that would otherwise require a physically larger aperture, thereby reducing optical system volume.
Solution Approach 2:
The invention changes the operational parameters of the detector array, switching from simultaneous full-field detection to sequential spatial sampling. This parameter change allows the system to achieve high resolution through temporal integration of multiple measurements, avoiding the need for increased aperture size.
3Area of stationary object
If detector area is increased to maintain field of view, then field of view is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent divides the detection task across multiple smaller detector elements that are scanned sequentially rather than requiring a single large detector array. This segmentation allows the use of smaller, more manufacturable detector elements while achieving equivalent or superior effective field of view through the scanning mechanism.
Solution Approach 2:
The invention introduces temporal dynamics to the detection process, where a smaller detector array achieves the effective coverage of a larger array by scanning through different spatial positions over time. This dynamic approach reduces the required detector area and associated manufacturing precision challenges.
4Measurement precision
If focal length is increased to improve resolution, then resolution is improved, but alignment and surface form error requirements become tighter
Solution Approach 1:
The patent employs dynamic scanning to effectively synthesize high resolution without requiring the physically larger optical system that would necessitate tighter manufacturing tolerances. By using temporal integration of sequential measurements, the system achieves high resolution with relaxed optical fabrication and alignment requirements.
Data Source
AI summary
An aspect of the disclosure provides An earth observation apparatus to be carried by a moving aerial platform or satellite for obtaining images of the surface of the earth, the apparatus comprising: an optical train having an optical field of view for imaging a region of the surface of the earth and being configured to form an image of the region at an image plane; an image sensor disposed at the image plane providing an imaging field of view; a view adjuster configured to control the optical train to: provide forward motion compensation for a stare time; and to displace the image, relative to the imaging field of view, in an across-track direction in a sequence of discrete displacement steps during each stare time; wherein the image sensor comprises a plurality of active areas, each comprising an area array detector and the active areas being spaced apart by inactive areas at the image plane wherein each active area captures a frame of image data for each discrete displacement step thereby to capture a plurality of frames for each discrete displacement step and the plurality of frames captured for each discrete displacement step are displaced in the across-track direction, relative to the imaging field of view, from the plurality of frames captured for the next discrete step.