Optical Baffle for Beam Scanner Aberration Control
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Solution Overview
Problem
Beam scanning projection systems, such as virtual retinal displays, suffer from geometric aberrations, particularly for off-axis rays, which are exacerbated by the use of holographic optical elements. This leads to image distortion and reduced image quality, and existing solutions like aperture stops and reducing spot size increase unwanted diffraction effects.
Innovation Solution
A beam scanner system comprising a micro scanning mirror and an optical baffle, where the micro scanning mirror rotates to reflectively scan a light beam between angular positions, and the optical baffle controllably vignettes the light beam as the mirror moves, reducing geometric aberrations while minimizing diffraction effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If aperture stops are used to block marginal rays and reduce geometric aberrations, then geometric aberrations are reduced, but unwanted diffraction effects increase
Solution Approach 1:
The optical baffle is designed with a specific geometry that provides different levels of vignetting for different regions of the light beam. The baffle selectively blocks only the problematic marginal rays that cause geometric aberrations while preserving the central paraxial rays that form the image, thereby reducing diffraction effects compared to a uniform aperture stop.
Solution Approach 2:
The optical baffle introduces asymmetric vignetting that is tailored to the specific geometry of the beam scanning system. This asymmetric design allows selective blocking of rays in specific angular ranges that cause aberrations while maintaining transmission of rays in other ranges, optimizing the balance between aberration reduction and diffraction minimization.
2Manufacturing precision
If the spot size of the light source is reduced to reduce aberrations, then geometric aberrations are reduced, but diffraction effects increase
Solution Approach 1:
The optical baffle extracts and removes only the specific portion of the light beam (marginal rays) that causes geometric aberrations, while preserving the majority of the beam that is needed for image formation. This selective extraction allows maintaining a larger spot size without suffering from the full extent of geometric aberrations.
3Weight of moving object
If micro scanning mirrors with small reflective area are used to maintain compact size, then system size and weight are reduced, but geometric aberrations at beam edges increase
Solution Approach 1:
The optical baffle provides localized correction by selectively vignetting only the edge portions of the beam that are affected by geometric aberrations from the small micro scanning mirror, while preserving the quality of the central beam regions. This allows maintaining the compact small mirror design while mitigating its edge aberrations.
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 solution effectively reduces geometric aberrations in beam scanning projection systems without significantly increasing diffraction effects, thereby improving image quality and maintaining a compact, low-cost system design suitable for augmented reality applications.
Implementation Method 1
the micro scanning mirror is located on an optical axis of a light source, and configured and arranged to rotate about an axis of rotation to reflectively scan the light beam between a first angular position and a second angular position
Implementation Method 2
the optical baffle is positioned with respect to the micro scanning mirror to controllably vignette the light beam as the micro scanning mirror moves between a first angular position and a second angular position
Data Source
AI summary
The disclosure relates to a beam scanner system for a virtual retinal display. The beam scanner includes an optical baffle; and a micro scanning mirror The micro scanning mirror is located on an optical axis of a light source, and configured and arranged to rotate about an axis of rotation to reflectively scan the light beam between a first angular position and a second angular position. The optical baffle is positioned with respect to the micro scanning mirror to controllably block or pass the light beam as the micro scanning mirror moves between a first angular position and a second angular position.