Fresnel Zone Plate Phase Retrieval for Wide-Band Wavefront Reconstruction
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Solution Overview
Problem
Conventional phase retrieval methods using a common lens for wavefront reconstruction are limited by a narrow band of retrieved information, failing to achieve wide-band wavefront reconstruction due to the use of a single focus and limited light intensity acquisition.
Innovation Solution
A phase retrieval detection device and method utilizing a Fresnel zone plate (FZP) for diffraction information fusion, incorporating a laser, attenuation mirror, micro-objective, pinhole filter, collimating lens, and CCD camera, to acquire a light intensity map at an optimal off-focus position, enabling iterative phase retrieval with enhanced diffraction information and multi-focus characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common lens with a single focus is used for phase retrieval, then the device structure is simple, but the wavefront reconstruction band is narrow
Solution Approach 1:
The patent segments the wavefront reconstruction task by using a Fresnel zone plate with multiple focal positions instead of a single-focus lens. Each focal position captures diffraction information for a specific spatial frequency band, allowing the system to reconstruct the entire wavefront by combining information from multiple segments (foci). This is implemented through the FZP's inherent multi-focus property, where different zones of the zone plate correspond to different spatial frequencies.
Solution Approach 2:
The patent transitions from a single-focus lens to a multi-focus Fresnel zone plate, adding the dimension of multiple focal positions. This dimensional change enables the system to capture diffraction information at multiple spatial frequencies simultaneously, expanding the wavefront reconstruction band from a narrow single-band to a wide multi-band without significantly increasing device complexity.
2Ease of operation
If a single focus position is used for light intensity acquisition, then the measurement process is simple, but the information content in the light intensity map is limited
Solution Approach 1:
The Fresnel zone plate serves multiple functions simultaneously: it acts as both the optical element for focusing light and the diffraction grating for spatial frequency separation. The multi-focus characteristic of the FZP allows a single optical element to provide multiple focal positions, each capturing different spatial frequency information. This multi-functionality enables the system to acquire rich diffraction information across multiple spatial frequencies without requiring multiple separate measurement processes.
3Device complexity
If conventional phase retrieval methods are used, then the experimental device is simple, but the wavefront reconstruction precision is insufficient for high-power and high-energy optical systems
Solution Approach 1:
The patent changes the key parameter of the optical element from a conventional lens to a Fresnel zone plate, fundamentally altering the diffraction characteristics. This parameter change enables the system to capture diffraction information across a wider range of spatial frequencies, thereby improving wavefront reconstruction precision for high-power and high-energy optical systems while maintaining experimental simplicity.
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 method achieves higher precision and wider-band wavefront reconstruction with improved convergence speed and accuracy, surpassing conventional lens-based methods by leveraging the FZP's multi-focus capability.
Implementation Method 1
a phase retrieval detection device and method based on diffraction information fusion of a Fresnel zone plate (FZP)
Implementation Method 2
a collimating lens, an element to be detected, an FZP and an image acquisition device that are sequentially arranged along a light path
Implementation Method 3
the micro-objective is positioned behind the attenuation mirror; the pinhole filter is positioned behind the micro-objective and at a convergent focus of the micro-objective
Data Source
AI summary
A phase retrieval detection device based on diffraction information fusion of a Fresnel zone plate (FZP) (7) is provided, including a laser (1), an attenuation mirror (2), a micro-objective (3), a pinhole filter (4), a collimating objective (5), an element (6) to be detected, an FZP (7), and an image acquisition device (8) that are sequentially arranged along a light path. The phase retrieval detection device uses the FZP (7) as a light beam convergent element instead of a conventional lens, and makes an acquired diffraction spot contain more diffraction information by virtue of a multi-focus characteristic of the FZP (7). Based on a classical iterative phase retrieval method, a phase retrieval method based on the diffraction information fusion of the FZP (7) uses a diffraction light intensity distribution modulated by the FZP for retrieval to reconstruct a wider band of a wavefront to be detected.