Polarization Grating Fabrication via Orthogonal Light Scanning
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Solution Overview
Problem
Conventional liquid-crystal-on-silicon (LCOS) projectors suffer from low optical efficiency due to the polarization state modulation process, which reduces the brightness of the image frame when a polarizing beam splitter is used.
Innovation Solution
A projection device incorporating a light source, a reflective spatial polarization modulator, and a polarization grating, where the polarization grating diffracts the light beam, concentrating light energy on a specific diffracted order, eliminating the need for a polarizing beam splitter and enhancing optical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a polarizing beam splitter is used to separate polarized light in an LCOS projector, then the polarization state can be modulated, but the optical efficiency is considerably reduced to about 3-4%
Solution Approach 1:
The patent extracts and removes the polarizing beam splitter from the optical path by using a reflective spatial light modulator that directly modulates the polarization state of reflected light. This eliminates the need for separate polarization separation components, thereby removing the source of significant optical efficiency loss while simplifying the overall device structure.
Solution Approach 2:
The patent replaces the mechanical/optical polarizing beam splitter system with an electrically controlled reflective spatial light modulator that uses liquid crystal technology to modulate polarization states. This substitution allows for more efficient light utilization since the modulator reflects and modulates the same light beam rather than separating and blocking portions of it.
2Manufacturing precision
If conventional fabrication methods are used for polarization gratings, then alignment layers must be contacted, but this causes contact problems that reduce fabrication quality
Solution Approach 1:
The patent introduces a suspension liquid crystal layer as an intermediary medium during the fabrication process. This layer allows the polarization grating pattern to be formed through optical field distribution without direct contact between alignment layers and other components, thereby eliminating contact-related fabrication problems while maintaining precise pattern formation.
Solution Approach 2:
The patent replaces mechanical contact-based alignment layer processing with an optical field-based fabrication method. By using optical fields to pattern the polarization grating through the suspension liquid crystal layer, the process eliminates mechanical contact issues while achieving high manufacturing precision through optical control.
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 results in a projection device with improved optical efficiency, providing a high-brightness image frame without the limitations of conventional systems, and a simple fabrication method for the polarization grating that avoids contact issues with alignment layers.
Implementation Method 1
the polarization grating diffracts the light beam from the light source, and the light energy transferred to the projection lens can be concentrated on the light beam with a certain diffracted order
Implementation Method 2
causing two orthogonally polarized lights to scan the polarization-sensitive material and to meet on the polarization-sensitive material
Data Source
AI summary
A fabrication method of a polarization grating is provided. The method includes providing a polarization-sensitive material; and causing two orthogonally polarized lights to scan the polarization-sensitive material and to meet on the polarization-sensitive material.