Optical Mask System for High Irradiance Beam Control
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Solution Overview
Problem
Current methods for generating high peak irradiance electromagnetic radiation with small lateral dimensions are limited by diffraction, leading to reduced Strehl ratios and increased complexity, and require mechanical scanning mechanisms, which are slow and prone to distortions.
Innovation Solution
Employing amplitude and phase masks at non-conjugate locations within the optical system to modify the electromagnetic radiation's amplitude and phase, allowing for localized enhancements in irradiance and radiance without reducing the Strehl ratio, and enabling electronic control of beam shape and position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If diffraction-limited focusing is used to generate high peak irradiance with small lateral dimensions, then the irradiance concentration is improved, but the Strehl ratio deteriorates and system complexity increases
Solution Approach 1:
The patent divides the optical system into multiple functional components: a diffraction grating that segments the incident beam into multiple orders, and a zone plate that selectively focuses specific diffraction orders. This segmentation allows control over the focal spot characteristics while maintaining high Strehl ratio by excluding higher-order diffraction components that would degrade image quality.
Solution Approach 2:
The zone plate introduces local quality variations through its alternating transparent and opaque zones, creating constructive interference at the focal point while suppressing sidelobes. This local modulation of the wavefront enables high peak irradiance concentration without the aberrations that would reduce the Strehl ratio.
2Adaptability or versatility
If mechanical scanning mechanisms are used to control beam position and shape, then positioning flexibility is improved, but scanning speed deteriorates and distortion increases
Solution Approach 1:
The patent replaces mechanical scanning mechanisms with a purely optical solution using diffraction gratings and zone plates. The beam position and shape are controlled by selecting which diffraction orders are focused, enabling rapid, distortion-free beam steering without moving parts. This substitution of mechanical systems with optical interference-based control achieves both flexibility and high speed.
3Length of moving object
If lens aperture diameter is reduced to decrease Airy disk size, then the focal spot size is improved, but the lens size and complexity increase
Solution Approach 1:
The patent extracts the focusing function from a conventional lens system and implements it through a zone plate placed at the focal plane of a simple lens. The zone plate selectively transmits only the necessary diffraction orders, eliminating the need for a complex, large-aperture lens while achieving the same or better focal spot size. This extraction of the critical focusing function simplifies the overall optical system.
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
Achieves significant increases in output radiation irradiance and radiance with flexible control over size, shape, and direction, eliminating the need for mechanical scanners and maintaining high Strehl ratios, suitable for a broad range of electromagnetic wavelengths.
Implementation Method 1
The size of the resulting pattern in the focal plane is limited primarily by diffraction. The resultant field distribution of the diffraction limited lens is called an Airy pattern
Data Source
AI summary
An optical system for producing electromagnetic radiation with localized increases in irradiance or radiance at the system output includes a first optical mask containing localized regions for producing controlled modifications of phase delays and/or amplitude attenuations and located within the input plane of said optical system. The system also includes at least a single optical component with positive optical power located after the input plane and at least one additional optical mask located after the optical component at non-conjugate locations with respect to the input plane of the system. The additional optical mask contains localized regions for producing controlled modifications of phase delays. Locally increased radiation distributions are produced at the system output.