Optical Wavefront Analyser Phase Diversity Plate
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Solution Overview
Problem
Optical instruments, such as space telescopes, are limited in measuring light intensity and lose phase information, leading to noisy measurements and aberrations due to the convolution of the observed object with the optical system's Point Spread Function (PSF), which complicates the estimation of Wave-Front Error (WFE) essential for correcting image defects.
Innovation Solution
The introduction of an optical plate with low or zero optical power near the photoreception assembly in the optical architecture to create a phase diversity algorithm, generating a first focused image and a second defocused image, allowing for the estimation of WFE through phase diversity analysis, which can correct optical aberrations and improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase diversity analysis is implemented to estimate WFE, then measurement precision of wavefront error is improved, but device complexity increases due to requiring multiple image acquisitions and processing algorithms
Solution Approach 1:
The patent introduces an optical plate that pre-establishes the defocused image path before detection. By incorporating the defocusing element into the optical train, the system prepares both focused and defocused images simultaneously through passive optical means, eliminating the need for active defocus adjustment mechanisms and reducing system complexity while maintaining wavefront estimation capability
Solution Approach 2:
The optical plate serves as an intermediary element that splits the optical path to create both focused and defocused images. This intermediary component enables phase diversity analysis by introducing a controlled defocus between two image paths, allowing wavefront error estimation without requiring complex active optical modulation or multiple separate detection systems
2Loss of information
If multiple images (focused and defocused) are acquired for phase diversity analysis, then information completeness for wavefront reconstruction is improved, but loss of time increases due to multiple acquisitions
Solution Approach 1:
The optical plate enables continuous capture of both focused and defocused images simultaneously in a single exposure. By creating parallel optical paths that deliver both image types to the detector at the same time, the system maintains continuous useful action without interruption for sequential acquisitions, thereby preserving phase information while eliminating time loss
Solution Approach 2:
The patent adds a spatial dimension to the image acquisition by creating a second image path with defocused geometry. Instead of acquiring images sequentially in time, the system uses spatial separation through the optical plate to produce both focused and defocused images simultaneously on the detector plane, transforming a time-based problem into a space-based solution
3Measurement precision
If Shack-Hartmann method is used for wavefront analysis, then measurement precision of local WFE is improved, but device complexity increases due to ancillary analysis channel and optical components
Solution Approach 1:
The patent merges the wavefront analysis function with the existing imaging detector by using the same detector to capture both focused and defocused images. This consolidation eliminates the need for separate Shack-Hartmann sensor components such as microlens arrays and position-sensitive detectors, reducing optical device complexity while maintaining local wavefront measurement capability through phase diversity analysis of the combined image data
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 enables the simple creation of necessary defocuses for phase diversity algorithms, facilitating the estimation and correction of WFE, thereby enhancing the optical quality and clarity of images obtained by space telescopes by accounting for geometric and chromatic aberrations.
Implementation Method 1
the second image being obtained in transmission after double reflection on the two faces of the plate
Implementation Method 2
the first image being obtained in simple transmission through said optical plate
Data Source
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Figure 5~6
AI summary
The instrument has an optical architecture including an optical unit (1) intended to make an image of a luminous object, and a photoreception assembly (3). Acquisition and analysis units of the image comprise a phase diversity type algorithm. The architecture comprises an optical blade (2) having a low or zero optical power in vicinity of the assembly. The blade is arranged to form a focused image (10) using a first predetermined value, and a defocused and shifted image (20) using a second predetermined value relative to the focused image, on entire or part of the assembly. The blade is plane-parallel faces blade, a plane faces prism, an air blade and a mangin mirror.