Waveguide Sidewall Gradient for Uniform Luminance in Rear Projection Screens
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Solution Overview
Problem
Existing optical display devices, such as rear projection screens, suffer from non-uniform light distribution and luminance due to varying incident angles and light intensities across the screen, leading to degraded image quality and homogeneity.
Innovation Solution
The design of waveguides with varying sidewall gradients, sizes, heights, and refractive indices across different sections of the screen, tailored to incident angles and light intensities, ensures uniform light distribution by optimizing reflection angles and reducing light loss in peripheral areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If waveguides of the same structure are used throughout the screen, then a wide viewing angle can be achieved in the central area, but the luminance in the peripheral area is considerably degraded
Solution Approach 1:
The patent applies local quality by designing waveguides with different structures in different regions of the screen. Specifically, the waveguides in the central area have one structure optimized for wide viewing angle, while waveguides in the peripheral area have a different structure optimized for luminance. This regional differentiation allows each area to have the optimal waveguide configuration for its specific lighting conditions and viewing requirements.
2Device complexity
If a single diffusive light source is employed, then the device structure is simplified, but the central and peripheral areas of the screen exhibit different luminance due to different incident angles and different light-paths
Solution Approach 1:
The patent compensates for the non-uniform light distribution from a single diffusive light source by implementing local quality variations in the waveguide structures. Waveguides in different regions are designed with specific structural parameters that account for the varying incident angles and light paths from the central light source, thereby achieving uniform luminance across the entire screen despite the simplified single-source configuration.
3Area of stationary object
If a plurality of unit light sources is used, then the light coverage is improved, but the light intensity is lowered in the boundary area between the light sources
Solution Approach 1:
The patent addresses the boundary area luminance reduction issue by designing waveguides with region-specific structures. In boundary areas between multiple light sources, the waveguide structures are optimized to compensate for the lower light intensity, while in central areas with higher intensity, different structural parameters are used. This local optimization ensures uniform luminance distribution across the entire screen area covered by multiple light sources.
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
This approach achieves uniform luminance and enhanced image homogeneity across the entire screen, preventing luminance degradation and improving overall image quality.
Implementation Method 1
imaging light rays incident from a light source placed rearwards of the center of the optical device being reflected inside the waveguide to be projected to the outside of the waveguide
Data Source
AI summary
Disclosed are an optical display device producing uniform light distribution and a method of fabricating such devices. The optical display device has waveguides arranged in vertical and horizontal directions. The waveguide has a conical shape whose cross-section decreases towards the light-projection side thereof. At least one of the size, height, spacing, and refraction index of the waveguide is designed to be different for each section, depending on an incident angle and/or intensity of light inputted from a light source. Therefore, the intensity of projected light can be made uniform over all sections of the optical device.