Rotating Grating VHOE Recording System for Ghost-Free Angle Multiplexing
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Solution Overview
Problem
Existing VHOE-based light-guide near-eye displays have limited viewing angles due to strong angle selectivity, requiring complex and inefficient angle multiplexing techniques to increase viewing angles, which often result in ghost images and high production costs.
Innovation Solution
A VHOE-forming angle-multiplexing recording system with a rotating grating is introduced, which includes a collimated light source, a rotating grating with a light output surface for placing a volume-hologram-recording photosensitive material, and an electronic iris to prevent interference between light beams, allowing for precise recording of multiple gratings without ghost images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional two-time angle-multiplexing recording structure is used to increase viewing angle, then the viewing angle of VHOE is improved, but the system complexity increases and ghost images are generated
Solution Approach 1:
The patent combines the functions of multiple beam splitters, shutters, and mirrors into a single rotating grating mechanism. The rotating grating simultaneously performs beam splitting, angle modulation, and spatial filtering, reducing the number of optical elements from over 10 separate components to one integrated device, thereby simplifying the recording system while maintaining angle multiplexing capability
Solution Approach 2:
The rotating grating serves multiple functions: it acts as a beam splitter to divide the collimated light into multiple beams, as an angle modulator to create different incidence angles for angle multiplexing, and as a spatial filter to prevent ghost images. This multi-functional design eliminates the need for separate optical elements for each function, reducing system complexity
2Adaptability or versatility
If conventional angle multiplexing with multiple beam splitters and shutters is used, then viewing angle is increased, but energy efficiency decreases
Solution Approach 1:
By merging the functions of multiple beam splitters into a single rotating grating, the patent reduces the number of optical interfaces from 4 or more beam splitting surfaces to one grating structure. This reduction in optical interfaces minimizes energy loss through reflection and absorption, improving overall optical energy efficiency while maintaining the capability to generate multiple beams for angle multiplexing
3Manufacturing precision
If precise control of incidence angles is implemented in conventional system, then grating recording precision is improved, but system complexity and cost increase
Solution Approach 1:
The patent replaces static, precisely-adjusted optical elements with a dynamic rotating grating mechanism. The grating rotates to different angular positions to sequentially present different beam splitting angles to the photosensitive material, eliminating the need for complex mechanical adjustment mechanisms and precision alignment systems while maintaining accurate angle control through rotational positioning
4Device complexity
If rotating grating is used for angle multiplexing, then system simplicity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses computer-aided design and computer-aided manufacturing (CAD/CAM) techniques to precisely fabricate the rotating grating with the required angular parameters. By transferring the complexity from mechanical assembly to digital design and manufacturing, the system achieves high precision grating fabrication with controlled diffraction angles while maintaining overall system 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 system effectively prevents ghost images, achieves higher precision in grating recording, reduces production defects, and increases efficiency while lowering costs, compared to conventional methods.
Implementation Method 1
a rotating grating provided in an optical path of the collimated light source... The light of the collimated light source is projected to the rotating grating... the rotating grating is rotated to a first angle such that the first collimated light beam... is diffracted at the far end of the thin grating
Implementation Method 2
the rotating grating is rotated to a first angle such that the first collimated light beam, i.e., the first object light, enters the volume-hologram-recording photosensitive material at a first-collimated-light-beam angle of incidence
Implementation Method 3
an electronic iris provided in the optical path between the collimated light source and the rotating grating
Implementation Method 4
a rotating grating provided in the optical path of the collimated light source and having a light output surface serving also as a placement surface on which a volume-hologram-recording photosensitive material is placed
Data Source
AI summary
A VHOE (volume holographic optical element)-forming angle-multiplexing recording system with a rotating grating includes a collimated light source and an electronic iris in addition to the rotating grating. The rotating grating is provided in the optical path of the collimated light source and has a light output surface serving also as a placement surface on which a volume-hologram-recording photosensitive material can be placed. The electronic iris is provided in the optical path between the collimated light source and the rotating grating. The VHOE-forming angle-multiplexing recording system is easy to operate, is stable, and can make a plurality of gratings without generating a ghost image.