Shared-Aperture EO Sensor Time Multiplexing Ranging and Imaging
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Solution Overview
Problem
Existing electro-optic sensors face challenges in providing accurate range information without compromising imaging performance, as current methods like active laser rangefinders are costly, passive approaches suffer from accuracy issues, and coded aperture techniques result in significant image loss and noise.
Innovation Solution
A shared-aperture EO sensor that time multiplexes an optical imaging channel and an optical ranging channel, using an adaptive optical modulator to modulate the wavefront with spatial patterns, allowing for accurate range estimation without sacrificing imaging performance by allocating unused frame portions for ranging processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an active laser rangefinder is used to provide accurate range information, then ranging accuracy is improved, but system cost increases
Solution Approach 1:
The patent combines the imaging function and ranging function into a single shared-aperture sensor system. The same optical aperture and detector are used for both imaging and ranging measurements, eliminating the need for separate laser rangefinder hardware and reducing system cost while maintaining ranging accuracy through temporal multiplexing of the two functions.
Solution Approach 2:
The sensor system is designed to perform multiple functions (imaging and ranging) using a single unified platform. The detector and optical system serve dual purposes, with the ranging channel utilizing the same hardware resources as the imaging channel, thereby reducing overall system complexity and cost.
2Device complexity
If multiple apertures are used to make parallax measurements for passive ranging, then ranging function is provided without active components, but measurement accuracy degrades and calibration becomes difficult
Solution Approach 1:
The patent segments the frame time into distinct imaging intervals and ranging intervals. During ranging intervals, a spatial code is applied to the aperture, and the detector captures coded aperture images. This temporal segmentation allows accurate passive ranging through wavefront coding while maintaining a single aperture, avoiding the accuracy degradation and calibration issues of multi-aperture systems.
3Measurement precision
If coded aperture is used for simultaneous imaging and passive ranging, then ranging function is achieved, but imaging performance suffers from approximately 50% loss and reconstruction noise
Solution Approach 1:
The patent employs periodic temporal multiplexing where the aperture alternates between imaging mode and ranging mode with spatial coding. During imaging intervals, the full aperture is used for high-quality image capture. During ranging intervals, a spatial code is applied. This periodic switching ensures that imaging performance is not continuously degraded, as full-aperture imaging occurs during dedicated imaging intervals.
Solution Approach 2:
The patent applies spatial codes to the aperture in advance during ranging intervals before the imaging interval begins. This preliminary action with coded aperture allows the system to extract ranging information from the coded pattern while preserving the ability to capture high-quality images during subsequent imaging intervals without the 50% performance loss associated with continuous coded aperture operation.
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
Enables high-accuracy range estimation within a specific range window while maintaining imaging channel performance, with the ability to expand range windows and optimize spatial patterns for improved accuracy and reduced error.
Implementation Method 1
The spatial pattern is configured such that objects in the scene within a certain range window produce image components having a distinct spatial structure sensitive to the range within the range window
Implementation Method 2
A detector converts the optical radiation of an optical image of the modulated wavefront into an electrical signal
Data Source
AI summary
A shared-aperture EO imaging and ranging sensor is implemented by time multiplexing an optical imaging channel and an optical ranging channel. The optical ranging channel is allocated the “unused portion” of each frame; that portion of the frame that is reserved from electronics processing of the imaging channel. The electronics processing of ranging channel is performed during the integration period of the next frame. This allows ranging to be provided without sacrificing the performance of the imaging channel. Ranging may be provided using either “coded aperture” or “wavefront coding”.