Diffractive Element Wavefront Analysis for High-Resolution Phase Imaging
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Solution Overview
Problem
Current wave front analysers, such as those using Shack-Hartmann technology, suffer from degraded spatial resolution in phase images due to the need to distribute wave front samples over multiple sensor pixels, limiting the achievable resolution of phase measurements.
Innovation Solution
A method involving a diffractive element that converts incident electromagnetic waves into diffracted waves, which are then analyzed by a matrix-array sensor with multiple acquisitions at various relative positions, allowing for the calculation of intensity and phase gradients with improved resolution by considering multiple harmonics of the interference pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wave front analysers use Shack-Hartmann technology with a matrix array of microlenses, then phase gradients can be calculated from spot positions, but the spatial resolution of phase images is degraded because multiple sensor pixels are required to sample each wave front sample
Solution Approach 1:
The patent replaces the mechanical/optical sampling system (microlenses physically distributing wave front samples) with a computational approach using Fast Fourier Transform. The diffractive element creates an interference pattern that encodes phase information, and the FFT algorithm extracts this information computationally, eliminating the need for physical spot distribution across multiple pixels and achieving full sensor resolution.
Solution Approach 2:
The patent transforms the measurement approach by changing from direct spatial sampling (Shack-Hartmann) to frequency domain analysis. By capturing the interference pattern in the spatial domain and transforming it to the frequency domain via FFT, the system extracts phase information with higher resolution, converting a spatial sampling problem into a frequency analysis problem.
2Measurement precision
If wave front analysers use quadriwave lateral shearing interferometry with a grating, then phase gradients can be calculated from interferogram deformation, but the spatial resolution remains lower than sensor resolution because only a small number of pixels (4x4) are used to sample the interferogram
Solution Approach 1:
The patent replaces the limited spatial sampling approach (using only 4x4 pixels to sample interferogram deformation) with a global Fourier analysis of the entire interferogram. The FFT process utilizes all sensor pixels to extract phase gradient information, transforming a localized sampling method into a global analysis method that achieves full sensor resolution.
Solution Approach 2:
The patent transitions from spatial domain sampling (using a small subset of pixels in real space) to frequency domain analysis (using the Fourier transform to analyze the entire interferogram). This dimensional transformation allows extraction of phase information with resolution matching the full sensor array, rather than being limited by the small sampling grid.
3Productivity
If phase analysis methods assume phase data is constant over several neighbouring pixels to generate offset interferograms, then phase images can be obtained rapidly, but the resolution of phase images is reduced with respect to sensor resolution
Solution Approach 1:
The patent replaces the assumption-based method (assuming phase is constant over multiple pixels) with a rigorous Fourier analysis method. Instead of making simplifying assumptions about phase uniformity, the FFT approach directly extracts phase information from the interference pattern, achieving both speed (single interferogram processing) and full sensor resolution without requiring phase constancy assumptions.
4Measurement precision
If additional optical masks or elements are used to achieve high resolution phase measurements, then measurement precision can be improved, but device complexity increases
Solution Approach 1:
The patent makes the diffractive element serve multiple functions: it creates the interference pattern, encodes the phase information in the spatial frequencies, and enables full-resolution measurement. This single element replaces what would traditionally require multiple optical components (masks, gratings, shearing elements), achieving high precision while minimizing device complexity.
Solution Approach 2:
The patent merges the functions of wave front sampling, interference pattern generation, and phase encoding into a single diffractive element. Instead of using separate optical masks or multiple elements to achieve phase measurement, the diffractive element performs all these functions simultaneously, and the FFT algorithm extracts the phase information, reducing the overall system complexity.
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 enhances the resolution of phase images to match the sensor's resolution, providing higher definition and compactness compared to existing methods, while eliminating the need for additional optical masks or elements.
Implementation Method 1
reception of an incident electromagnetic wave by a diffractive element, and conversion of this incident electromagnetic wave into a diffracted electromagnetic wave by the diffractive element
Implementation Method 2
reception, by a matrix-array sensor, of an interference pattern of the diffracted electromagnetic wave
Data Source
AI summary
The present invention relates to a method comprising reception of an incident electromagnetic wave (9) by a diffractive element (2) and conversion of this incident electromagnetic wave (9) into a diffracted electromagnetic wave (10) by the diffractive element (2); reception of the diffracted electromagnetic wave (10) by a matrix-array sensor (4) comprising a matrix-array of pixels that are aligned along one or two axes of pixel alignment (13, 14). The method comprises a plurality of acquisitions, by the matrix-array sensor (4), of a signal of the diffracted electromagnetic wave (10) corresponding to a plurality of relative positions between the diffractive element (2) and the matrix-array sensor (4). The invention also relates to a device (1) implementing this method.