Asymmetric Optical Element for Uniform Oblique Illumination
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Solution Overview
Problem
Current billboard lighting systems using metal halide lamps or LEDs suffer from poor uniformity of irradiance, with variations of 6:1 or more, leading to undesirable light distribution patterns and obstructed views, as they struggle to control both direct and reflected light paths simultaneously.
Innovation Solution
An asymmetrically shaped optical element with a base cavity for a light source, featuring total internal reflection and carefully curated surface curvatures to direct light output uniformly across a surface, increasing intensity with height and providing overlapping illumination distributions from multiple elements for comprehensive coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a smooth center portion window is used to control reflected light, then reflected light path is controlled, but direct light remains uncontrolled and creates poor uniformity
Solution Approach 1:
The window is divided into distinct functional zones: a central transparent portion for reflected light control and a peripheral refractive portion for direct light control. This segmentation allows each zone to be optimized for its specific light path without interfering with the other, resolving the contradiction between controlling reflected light and maintaining direct light control.
Solution Approach 2:
Different portions of the window are assigned different optical properties: the center portion is smooth for reflected light transmission, while the periphery contains refractive prismatic structures for direct light redirection. This local differentiation enables simultaneous control of both light paths, achieving uniform illumination without excessive overall complexity.
2Manufacturing precision
If refractive prismatic structures are added to the window periphery to control direct light, then direct light path is improved, but the structure becomes more complex
Solution Approach 1:
The window is divided into distinct functional zones: a central transparent portion for reflected light control and a peripheral refractive portion for direct light control. This segmentation allows each zone to be optimized for its specific light path without interfering with the other, resolving the contradiction between controlling reflected light and maintaining direct light control.
Solution Approach 2:
Different portions of the window are assigned different optical properties: the center portion is smooth for reflected light transmission, while the periphery contains refractive prismatic structures for direct light redirection. This local differentiation enables simultaneous control of both light paths, achieving uniform illumination without excessive overall complexity.
3Area of stationary object
If multiple high-power metal halide lamps are placed at the base of the billboard, then illumination coverage is achieved, but irradiance uniformity deteriorates with 6:1 or more variation
Solution Approach 1:
Multiple optical elements are combined in a single fixture housing, with each element contributing to illumination of different portions of the billboard. The optical elements work together to create a composite light distribution that achieves both broad coverage and uniform irradiance, eliminating the need for separate fixtures and improving overall uniformity.
Solution Approach 2:
The optical elements are designed with specific curvature parameters and orientations that control the angular distribution of light from each lamp. By carefully selecting these geometric parameters, the system achieves uniform irradiance across the billboard while maintaining comprehensive coverage, reducing variation from 6:1 to less than 2:1.
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 substantially uniform illumination with an irradiance variation of less than 2:1, enhancing visibility and reducing light pollution by optimizing light distribution along the height and width of the surface, compared to conventional systems.
Implementation Method 1
outer sides providing total internal reflection
Data Source
AI summary
An optical element is provided having an asymmetric body with a base cavity for receiving a light source, and outer sides providing total internal reflection, and a front face tilted so that the optical element's optical axis is at an oblique angle with respect to a target surface. Curvatures along cavity surfaces and outer sides are selected to output illumination from the body's front face having a distribution extending along the target surface's height and at least a portion of the width thereof having increased intensity with increasing height to provide at least substantially uniform illumination along the target surface's height. One or more optical elements may be in an apparatus, and multiple apparatuses may be disposed in front of one edge of a target surface and spaced from each other to provide the target surface with at least substantially uniform oblique illumination.