Digital Holography Phase Error Correction via Region Segmentation
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Solution Overview
Problem
Existing digital holography techniques struggle to accurately estimate phase errors and form clear images from single-shot data, especially in the presence of strong turbulence, due to surface roughness causing speckle effects.
Innovation Solution
A method and apparatus for digital holography that models phase perturbations across multiple discrete regions along the propagation path, using a test function to estimate reflectance values and phase perturbations from a single hologram record, reducing speckle and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image sharpening algorithms are used for single-shot digital holography, then phase error estimation can be performed, but the accuracy deteriorates in the presence of strong turbulence due to speckle effects
Solution Approach 1:
The patent divides the propagation path into multiple discrete regions and models phase perturbations separately in each region. This segmentation allows the system to handle turbulence effects region-by-region rather than as a unified complex problem, improving phase error estimation accuracy in single-shot conditions by reducing the impact of speckle effects through localized modeling
Solution Approach 2:
The patent introduces regularization terms with adjustable parameters into the test function to control the trade-off between data fidelity and spatial correlation. By optimizing these parameters, the system can suppress speckle-induced noise while preserving genuine phase information, thereby maintaining measurement precision under turbulent conditions
2Measurement precision
If multiple independent data sets are used for image sharpening, then phase error estimation accuracy improves, but the complexity of the system increases
Solution Approach 1:
The patent incorporates spatial correlation information and regularization constraints into the test function before actual phase estimation is performed. This preliminary incorporation of prior knowledge allows single-shot data to be processed with the same effectiveness as multi-shot data, eliminating the need for multiple data acquisitions while maintaining measurement precision
Solution Approach 2:
The patent enables the single-shot hologram data to serve multiple purposes simultaneously: it provides both the interference pattern for phase estimation and contains embedded spatial correlation information through the regularization terms. This self-service approach extracts maximum information from a single data set, avoiding the need for additional data acquisition systems
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 the formation of images with reduced high spatial frequency variations and improved accuracy in estimating phase errors, even in conditions of strong turbulence, by modeling phase perturbations and using regularization terms to enhance data fidelity and spatial correlation.
Implementation Method 1
Digital Holography (DH) uses coherent illumination and heterodyne detection to sense the amplitude and phase of light scattered off an object's surface
Implementation Method 2
Digital Holography (DH) uses coherent illumination and heterodyne detection to sense the amplitude and phase of light scattered off an object's surface
Data Source
AI summary
Light reflected from an illuminated object is mixed with a reference beam and sensed at a sensor array of a digital hologram apparatus. Digital hologram data, determined from the sensed light, is dependent upon complex valued reflection coefficients of the object and upon phase perturbations in propagation paths between the object and the sensor array. Reflectance values, which may be dependent upon expected values of the absolute square of the reflection coefficients, and phase perturbations are determined for which a test function is at an extremum, where the test function contains a data fidelity term dependent upon the hologram data from a single hologram, a first regularization term dependent upon the phase perturbations and a second regularization term dependent upon the reflectance values. An image of the object may be formed from the reflectance values and a wavefront of the reflected light may be determined from the phase perturbations.