Serially Addressed Sub-Pupil Screen for In Situ Wavefront Measurement
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Solution Overview
Problem
Current wavefront measurement techniques for electro-optic sensors in production are time-consuming, expensive, and require external detectors, limiting the dynamic range and spatial resolution of local wavefront slope measurements.
Innovation Solution
A system and method for in-situ wavefront measurement using the EO sensor's own detector, where a single sub-pupil sized beam is traced over the entrance pupil in a spatial pattern to form a serially addressed sub-pupil screen, allowing for disambiguation of local wavefront measurements and maximizing dynamic range by processing video signals with a computer processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Shack-Hartman wavefront sensor is used to illuminate the entire entrance pupil with a collimated beam, then the dynamic range for measuring local wavefront slopes is increased, but the spatial resolution decreases
Solution Approach 1:
The entrance pupil is divided into multiple sub-pupils that are illuminated sequentially rather than simultaneously. A single sub-pupil sized beam is traced over the entrance pupil in a spatial pattern to serially illuminate different sub-pupils at different times, forming a serially addressed sub-pupil screen. This temporal segmentation allows each sub-pupil to be measured with high spatial resolution while covering the entire pupil area over time, thus achieving both high spatial resolution and full dynamic range.
Solution Approach 2:
The system transitions from a static simultaneous measurement approach to a dynamic sequential measurement approach. The single sub-pupil beam is moved dynamically across the entrance pupil in a predetermined spatial pattern, and the EO detector captures images at different time instances corresponding to different sub-pupil positions. This dynamic approach allows the same detector to measure different spatial locations at different times, resolving the trade-off between spatial resolution and dynamic range.
2Measurement precision
If external detectors are used for wavefront measurement, then measurement capability is provided, but testing time and costs increase
Solution Approach 1:
The EO sensor's own detector is used to perform wavefront measurement on itself. The detector captures images of the sub-pupil beam as it is traced over the entrance pupil, and these images are processed to compute wavefront estimates. This self-service approach eliminates the need for external wavefront sensors and external detectors, reducing testing time and costs while maintaining measurement capability.
Solution Approach 2:
The EO detector serves multiple functions: it acts as both the operational detector for the EO sensor under test and as the wavefront measurement detector. The same detector is used for both imaging the sub-pupil beam positions and computing wavefront estimates, eliminating the need for separate measurement equipment and streamlining the testing process.
3Measurement precision
If the sub-pupil beam is traced over the entrance pupil in a spatial pattern, then local wavefront measurements are disambiguated, but the device complexity increases
Solution Approach 1:
The sub-pupil beam is traced over the entrance pupil in a periodic spatial pattern, systematically visiting different sub-pupil positions in a predetermined sequence. This periodic traversal ensures that each sub-pupil is illuminated and measured in turn, creating a time-stamped record of beam positions that can be mapped to specific spatial locations. The periodic nature of the traversal simplifies the disambiguation process by providing a regular, predictable sampling pattern.
Solution Approach 2:
The system uses feedback from the detected beam positions to compute wavefront estimates. The EO detector captures images showing the sub-pupil beam at different positions, and the computer processor uses these position measurements to calculate the wavefront error. The feedback loop connects the measured beam positions back to the wavefront computation, enabling accurate reconstruction of the wavefront from the sequential measurements.
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 approach reduces testing time and costs, improves wavefront estimate quality, and decouples spatial resolution from dynamic range, enabling more accurate and efficient wavefront error characterization without ambiguity.
Implementation Method 1
The optical telescope focuses the single sub-pupil beam into a single image at the image plane
Implementation Method 2
An EO detector is mounted to the optical telescope at or near the image plane to convert the image of the scene to an electronic representation
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A system and method for wavefront measurement of an EO sensor is performed in-situ using the sensor's EO detector in a manner that disambiguates the local wavefront measurements for different sub-pupils in time and maximizes the dynamic range for measuring the local wavefronts. A single sub-pupil sized optical beam is traced in a spatial, pattern over the EO sensor's entrance pupil to serially illuminate a temporal sequence of sub-pupils to form a serially addressed sub-pupil screen. The EO detector and video card capture a video signal for one sub-pupil at a time as the optical beam traces the spatial pattern. The video signal is routed to a computer processor that generates a spatio-temporal mapping of the spatial positions of the sub-pupils in the sub-pupil screen to the temporal positions of frames in the video signal. The computer processor uses the mapping to process the video signal to compute a wavefront estimate spanning the entrance pupil.