Light Guide Device with Inclined Reflective Surfaces for Compact Projectors
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Solution Overview
Problem
Projectors using LCOS panels are bulky due to the large distance between the polarizing beam splitter and the image-forming lens, resulting in a thick and inefficient design with lower light efficiency compared to other spatial light modulators.
Innovation Solution
A display module comprising a light guide plate, a reflective element with inclined surfaces, and a reflective polarizer, which guides the illumination beam efficiently while reducing thickness and volume, and enhances light efficiency and contrast ratio by modulating the polarization state of the beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polarizing beam splitter (PBS) with a continuous beam splitting plane inclined at 45 degrees is used in an LCOS panel projector, then the beam can be effectively split and redirected, but the PBS occupies a large space between the LCOS panel and the image-forming lens, resulting in a long distance and a thick, bulky projector
Solution Approach 1:
The continuous beam splitting plane of the traditional PBS is segmented into multiple discrete reflective surfaces (first reflective surfaces, second reflective surfaces, third reflective surfaces) with different inclination angles. Each surface handles a specific angular range of incident light, collectively achieving the beam splitting function while reducing the overall optical path length and device thickness.
Solution Approach 2:
Instead of using a single inclined plane at 45 degrees, the invention introduces reflective surfaces with multiple inclination angles (different dimensions of angular orientation) to redirect light beams. This multi-dimensional approach allows for more compact light path folding, reducing the distance between the LCOS panel and image-forming lens while maintaining effective beam splitting.
2Ease of manufacture
If a transmissive LCD panel is used as the spatial light modulator, then the device cost is lower, but the light efficiency is less than that of an LCOS panel
Solution Approach 1:
The invention uses reflective display units (reflective LCD panels or reflective LCOS panels) instead of transmissive panels. The illumination beam is directed onto the reflective display unit from the front side, and the modulated beam is reflected back through the same path. This reflective configuration increases light efficiency compared to transmissive panels while maintaining compatibility with cost-effective reflective display technologies.
3Length of stationary object
If the light guide plate is made thinner to reduce overall device thickness, then the display module achieves smaller thickness and volume, but the light guidance effectiveness must be maintained
Solution Approach 1:
The light guide plate incorporates localized reflective structures (reflective dots or reflective regions) at specific positions and orientations to redirect light beams. By concentrating the light guidance function in specific local areas rather than relying on the overall thickness of the plate, the design achieves effective light guidance in a thinner profile. The reflective elements are strategically positioned to redirect light from the incident surface to the appropriate exit surface.
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 achieves a thinner and more efficient display module with improved light efficiency and contrast ratio, effectively guiding light beams and reducing ghosting issues, while maintaining imaging quality.
Implementation Method 1
The reflective element has a plurality of first reflective surfaces inclined with respect to the second surface
Implementation Method 2
The reflective display unit is capable of modulating a polarization state of the illumination beam to form a modulated beam
Implementation Method 3
The reflective polarizer filters the modulated beam into an image beam
Implementation Method 4
The illumination beam enters the light guide plate through the incident surface
Data Source
AI summary
A display module is provided. A light source is configured to provide an illumination beam. A light guide plate has a first surface, a second surface opposite to the first surface, and an incident surface connecting the first surface and the second surface. The illumination beam enters the light guide plate through the incident surface. A reflective element is connected to the light guide plate and has a plurality of first reflective surfaces inclined with respect to the second surface. A reflective display unit is capable of modulating a polarization state of the illumination beam to form a modulated beam. The second surface is disposed between the reflective display unit and the first surface. The first surface is disposed between the second surface and a reflective polarizer, and the reflective polarizer filters the modulated beam into an image beam.