Fractional Coverage Louver Device for Rear Projection Displays
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Solution Overview
Problem
Rear projection display systems face issues with light loss and limited viewing angles due to the design of light guide screens, which affect picture quality and contrast, especially in environments with varying ambient light.
Innovation Solution
A fractional coverage louver device is integrated into the light guide screen, comprising a transparent layer with louver members that redirect light to improve viewing angles and reduce ambient light reflection, thereby enhancing contrast and reducing light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If light guide screens are used in rear projection displays, then the display thickness and weight are reduced, but light loss increases and viewing angles are limited
Solution Approach 1:
The light guide screen is segmented into multiple layers including a light guide layer, a louver layer with reflective louvers, and a viewing angle control layer. Each layer performs a specific function: the light guide layer transports light, the louver layer redirects light at specific angles, and the viewing angle control layer manages light distribution. This segmentation allows the system to maintain thin profile while controlling light loss and viewing angles through coordinated layer interactions.
Solution Approach 2:
The patent introduces a louver layer that operates in a different dimensional space than traditional projection screens. The louvers are arranged at specific angles (e.g., 45 degrees) to redirect light from the projection source toward the viewer while blocking ambient light from the front. This angular dimensionality allows the system to achieve both thinness and effective light management without requiring deep optical paths.
2Length of moving object
If light guide screens are used in rear projection displays, then the display thickness and weight are reduced, but viewing angles are limited
Solution Approach 1:
The viewing angle control is achieved through segmentation of the optical path into multiple functional layers. The louver layer contains multiple independently angled reflective surfaces that direct light to different viewing zones. The viewing angle control layer uses prismatic structures or microlens arrays to further distribute light across desired viewing angles. This layered segmentation enables thin display construction while achieving wide viewing angles through cumulative angular redirection.
Solution Approach 2:
Different regions of the light guide screen have different optical properties tailored to specific viewing requirements. The louver angles and densities vary across the screen surface to optimize light direction for different seating positions. This local optimization allows the thin display to provide consistent image quality across wide viewing angles without requiring uniform optical structures throughout.
3Manufacturing precision
If traditional lens and reflector designs are used in rear projection displays, then picture quality can be maintained, but the display thickness increases
Solution Approach 1:
The patent replaces traditional mechanical lens and reflector systems with an optical waveguide-based light transport system. Instead of using bulky projection lenses and adjustable mirrors, the invention uses total internal reflection in the light guide layer to transport images from the projection source to the viewing surface. This substitution of mechanical optical components with waveguide physics dramatically reduces display thickness while maintaining picture quality through precise optical path control.
Solution Approach 2:
The invention changes the fundamental parameters of light transport by utilizing total internal reflection at specific critical angles within the light guide layer. By controlling the refractive index differences between layers and setting precise incident angles, the system achieves efficient light transport without requiring traditional projection optics. The louver layer further modifies light parameters by redirecting at 45-degree angles, enabling thin display construction with maintained image quality.
4Illumination intensity
If ambient light is allowed to strike the viewing surface, then light room contrast improves, but picture quality deteriorates due to reflection
Solution Approach 1:
The patent converts the harmful effect of ambient light reflection into a beneficial feature by using the louver layer's reflective surfaces. The louvers are angled to reflect projection light toward viewers while simultaneously blocking front-incident ambient light from reaching the viewing surface. Ambient light that would normally cause glare is instead redirected away from the viewer's line of sight, transforming the problem of ambient light sensitivity into an advantage for light room viewing performance.
Solution Approach 2:
The optical system is segmented into light transport pathways and ambient light blocking pathways. The louver layer creates distinct optical channels: one for projecting image light at specific angles toward viewers, and another that blocks ambient light from the front. This segmentation allows the display to simultaneously achieve good light room contrast by blocking ambient reflections while maintaining visibility in bright environments through the controlled light transport path.
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 increases the viewing angle and contrast of the display, allowing a larger audience zone and minimizing the impact of ambient light, resulting in improved picture quality and reduced thickness and weight of the display system.
Implementation Method 1
louver members that redirect light to improve viewing angles and reduce ambient light reflection
Data Source
AI summary
In a particular embodiment, the fractional coverage louver device includes a transparent layer of material having a first surface and a second surface parallel thereto. A plurality of louver members disposed within the transparent layer of material provide fractional reflective coverage across the width of the transparent material. The louver members are aligned to receive light entering the first surface at a shallow angle relative to the first surface and direct the light out the second surface at a high angle relative to the second surface, thereby increasing the angular viewing range. Transparent areas between louver members allow a portion of incident ambient light to pass through the louver device without being reflected back to a viewer. As such, the louver device has advantageous contrast properties.