Object Transmission Characterization via Multi-Configuration Phase Retrieval
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Solution Overview
Problem
Conventional coherent diffraction imaging techniques face challenges in robustness due to non-trivial phase retrieval, requiring stable setups and prior knowledge of modulator functions, which limits their applicability to objects with simple phase variation and fast sample dynamics.
Innovation Solution
A method utilizing coherent incident radiation at multiple configurations, combined with iterative processes and amplitude constraints, to determine an object's transmission function by averaging independent measurements, enabling robust characterization of unknown objects without the need for overlapping measurements or prior modulator knowledge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ptychography is used to improve algorithmic convergence and imaging performance, then measurement robustness is improved, but setup stability requirements increase and device complexity increases
Solution Approach 1:
The imaging process is segmented into multiple independent measurements with different illumination configurations rather than requiring a single complex ptychography scan. Each measurement is independent and can be acquired rapidly, eliminating the need for stable mechanical positioning between measurements while still enabling robust reconstruction through computational integration of multiple configurations.
2Measurement precision
If ptychography is used to characterize the modulator, then modulator function accuracy is improved, but measurement time increases and device complexity increases
Solution Approach 1:
The modulator characterization and object imaging processes are merged into a single simultaneous reconstruction process. By incorporating the modulator function as a variable in the iterative phase retrieval algorithm alongside the object transmission function, both are determined from the same set of measurements without requiring separate characterization experiments, thereby reducing total measurement time while maintaining accuracy.
3Ease of operation
If conventional CDI techniques are used for phase retrieval, then simplicity of operation is maintained, but robustness deteriorates and applicability to complex objects is limited
Solution Approach 1:
The imaging approach transitions from conventional single-configuration CDI to multi-configuration illumination with iterative phase retrieval. By changing the illumination parameters (amplitude and phase profiles) across multiple measurements and incorporating an iterative optimization algorithm, the method achieves robust phase retrieval for complex objects while maintaining operational simplicity through automated computational processing.
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 robust imaging of unknown objects with fast sample dynamics and unstable setups, achieving rapid convergence and accurate reconstruction of the object's wavefield, eliminating the need for secondary measurement techniques.
Implementation Method 1
providing, via a support plane, coherent incident radiation at the object at each of a plurality of radiation configurations
Implementation Method 2
Coherent Diffraction Imaging (CDI) is a lensless coherent imaging technique
Implementation Method 3
detecting, at a detector, an intensity of radiation scattered by the object for each of the plurality of radiation configurations
Implementation Method 4
Coherent Modulation Imaging (CMI)... a modulator is placed between the object and the detector to strengthen interference among wavelets of the object exit wave and facilitate the phase retrieval
Data Source
AI summary
A method for characterising an object, including: providing, via a support plane, coherent incident radiation at the object at each of a plurality of radiation configurations, detecting, at a detector, an intensity of radiation scattered by the object for each radiation configuration, and determining, via an iterative process, an object transmission function associated with the object in dependence on the detected intensity of radiation for each radiation configuration. The iterative process comprises estimating, for each radiation configuration, an entrance wave function and an exit wave function, a support constraint and a current estimate of the object transmission function, determining a ratio of a sum of intensities of the exit wave function for the plurality of radiation configurations to a sum of intensities of the entrance wave function therefor, and updating the estimate of the object transmission function in dependence on the determined ratio and an amplitude constraint.