Beam Expander with Diffuser for Uniform Speckle-Reduced Output
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Solution Overview
Problem
Optical systems, particularly holographic imaging and display systems, face challenges in maintaining coherence and uniformity of light beams while minimizing device size, efficiently shaping the beam cross-section, and reducing speckles.
Innovation Solution
A beam expander comprising a first and second optical element, a light diffuser with an angular aperture, and a waveguide that diffuses and transforms light through total internal reflection to achieve coherent light homogeneity, required cross-sectional shaping, and speckle reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional high-efficiency beam expander is used, then optical efficiency is improved, but light beam uniformity deteriorates
Solution Approach 1:
The beam expander is divided into multiple functional modules: a beam shaping module with a first diffractive optical element, a homogenization module with a second diffractive optical element, and a speckle reduction module with a light diffuser. Each module performs a specific function to progressively improve beam quality while maintaining optical efficiency.
Solution Approach 2:
A light diffuser is introduced as an intermediary element between the beam shaping module and the output. This diffuser scattered the coherent light to reduce speckles while the subsequent optical elements re-collimate the light, maintaining both uniformity and efficiency.
2Shape
If the light beam cross-section is shaped, then beam cross-section shaping is improved, but light beam uniformity deteriorates
Solution Approach 1:
The diffractive optical elements are designed with spatially varying phase profiles that locally modify the light wavefront. The first DOE shapes the beam cross-section while the second DOE compensates for intensity variations, ensuring both shaping and uniformity are achieved through localized optical modifications.
3Stability of the object's composition
If coherent laser light is used, then coherence is improved, but speckles increase
Solution Approach 1:
A movable diffuser or oscillating diffuser is introduced to dynamically scatter the coherent light. By continuously varying the scattering pattern, the speckle patterns change over time, and when averaged by the detector or human eye, the apparent speckle contrast is reduced while coherence is maintained.
4Device complexity
If the device size is minimized, then device complexity is improved, but beam shaping capability deteriorates
Solution Approach 1:
Traditional mechanical beam shaping components such as multiple lenses and mirrors are replaced with diffractive optical elements that achieve the same beam shaping function through micro-scale surface relief structures. This substitution dramatically reduces the overall device size while maintaining or improving beam shaping capability.
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 beam expander ensures high uniformity and coherence of output light, reduces speckles by up to 80%, and maintains optical efficiency, suitable for applications in holographic displays and illumination systems.
Implementation Method 1
a waveguide that diffuses and transforms light through total internal reflection
Implementation Method 2
a light diffuser having an angular aperture, the light diffuser diffusing incident light through the angular aperture
Data Source
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AI summary
A beam expander (10) includes first (110) and second (120) optical elements spaced apart from each other, and a light diffuser (140) having an angular aperture that diffuses incident light through the angular aperture, wherein the first optical element (110) in-couples the diffused light such that light exiting the first optical element has a first cross-sectional shape and light having a second cross-sectional shape different from the first cross-sectional shape is incident on the second optical element (120), and the second optical element out-couples light incident from the first optical element.