Complex Diversity Phase Retrieval for Accurate Single-Shot Acquisition
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Solution Overview
Problem
Conventional single-shot phase retrieval techniques face challenges in accurately determining the effective filters applied to individual diffraction orders, leading to low accuracy and stagnation issues, despite advancements in diversity techniques like defocus, translation, and random diversity.
Innovation Solution
A new phase retrieval technique called complex diversity, which uses a diffractive grating or CGH to generate multiple diffraction orders with different diversity values, extracts both real and imaginary effective filters through numerical propagation, and employs a modified Fourier iterative algorithm to reconstruct the extrinsic phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase retrieval techniques are used, then multiple image acquisitions can be performed, but the measurement accuracy and productivity are limited due to multiple shots requirement
Solution Approach 1:
The patent segments the wavefront measurement into multiple diffraction orders generated by a grating, allowing simultaneous capture of multiple measurements in a single shot. Each diffraction order carries phase information with different diversity characteristics, enabling accurate phase retrieval without requiring multiple sequential acquisitions.
Solution Approach 2:
The patent transitions from temporal multiplexing (multiple shots in time) to spatial multiplexing (multiple diffraction orders in space). By using a grating to disperse light into multiple spatial orders, the system captures multiple phase measurements simultaneously in a single exposure, resolving the contradiction between measurement accuracy and acquisition speed.
2Productivity
If single-shot phase retrieval techniques with special gratings are used, then acquisition speed is improved, but the effective filters applied to diffracted orders are not accurately known
Solution Approach 1:
The patent implements a feedback mechanism where the known grating parameters and propagation distance are used to calculate the effective filters applied to each diffraction order. This calculated filter information feeds back into the phase retrieval algorithm, ensuring accurate reconstruction despite the single-shot acquisition constraint.
Solution Approach 2:
The patent performs preliminary calculation of the effective filters based on the known grating design and propagation geometry before the phase retrieval process. This pre-computed filter information is then used in the reconstruction algorithm, eliminating the need to empirically determine filters during the measurement process.
3Productivity
If computer-generated holograms are used to distribute multiple images, then single-shot acquisition is achieved, but the true effective filters differ from seed filters due to unconstrained complex field modulation
Solution Approach 1:
The patent replaces physical filter elements with computationally calculated effective filters. Instead of using physical filters whose characteristics might differ from design, the system calculates the exact effective filters based on the grating parameters and propagation distance, then uses these calculated filters in the phase retrieval algorithm.
Solution Approach 2:
The patent changes the approach from assuming seed filters are the effective filters to calculating the actual effective filters as a function of grating parameters, wavelength, and propagation distance. This parameter-based calculation accounts for the complex field modulation effects in CGHs and provides accurate filter characterization.
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
The complex diversity technique significantly improves phase retrieval accuracy by estimating extrinsic aberrations better than conventional methods, achieving sensor-less adaptive optics correction through iterative refinement of effective filters.
Implementation Method 1
uses a diffractive grating or CGH to generate multiple diffraction orders
Data Source
AI summary
A new diversity concept is provided for achieving accurate phase retrieval with a single shot acquisition. Multiple irradiance data are obtained by a diffractive grating or CGH designed to generate multiple diffraction orders with different diversity values. The effective filters associated with the individual diffraction orders from the diffractive grating or CGH are calculated. The effective filters are extracted by numerical propagation, and they preferably include both real and imaginary values, which signify both absorption and phase shift versus position in the filter plane. The reconstruction process utilizes accurate knowledge of the effective filters for each diffraction order for high quality reconstruction of the extrinsic phase.