Optical Element Exit Surface Scattering for LED Color Uniformity
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Solution Overview
Problem
LED light sources with separate emission positions for shorter-wavelength and longer-wavelength lights result in directional color variations, leading to undesirable bluish or reddish light tones depending on the direction, as existing optical elements fail to effectively diverge lights while minimizing color differences.
Innovation Solution
An optical element with a specific exit surface configuration featuring multiple local minimum and maximum values for scattering light in various directions, ensuring that the scattering area is limited to a range around the central axis, maintaining the light-diverging function while reducing color differences effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an optical element is used to diverge lights from the LED light source, then the light covering area is expanded, but color difference among directions increases
Solution Approach 1:
The exit surface is divided into multiple regions with different surface normal directions. Specifically, the surface is configured with multiple peaks and valleys (local maximum and minimum values of inclination angle) to create distinct light scattering regions. This segmentation allows different wavelengths to be scattered in different directions, thereby reducing color difference while maintaining wide light coverage.
Solution Approach 2:
Different regions of the exit surface are given different local properties through varying surface inclination angles. The surface includes multiple local maximum and minimum inclination angle regions, where each region scatters light with specific wavelength characteristics in particular directions. This local differentiation enables simultaneous achievement of wide coverage and color uniformity.
2Ease of manufacture
If the exit surface is made flat for simple manufacturing, then manufacturing is easier, but light scattering is insufficient and color difference remains
Solution Approach 1:
The exit surface is designed with curved features including multiple peaks and valleys (local maximum and minimum inclination angle regions). These curvature variations enable effective light scattering to reduce color difference. The curved surface profile allows precise control over light direction while remaining manufacturable through standard optical surface fabrication techniques.
3Object-affected harmful factors
If the optical element is designed with complex surface structure to reduce color difference, then color uniformity improves, but manufacturing complexity increases
Solution Approach 1:
The complex surface structure is segmented into multiple discrete peaks and valleys with specific inclination angles. This segmentation approach reduces color difference by creating distinct light scattering zones while maintaining a relatively simple overall structure that can be manufactured using standard optical surface techniques. The segmented design avoids requiring overly complex continuous surface variations.
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 optical element effectively reduces color differences among directions by scattering light from the outer region, maintaining the light-diverging function and ensuring uniform illumination, while avoiding color variations near the central axis.
Implementation Method 1
the exit surface is configured such that φ has plural local minimum values and plural local maximum values as a function of r... lights which pass through the area of the exit surface provided with the local maximum values and the local minimum values are scattered in various directions
Data Source
AI summary
An optical element includes a light receiving surface 101 covering a light source on a plane and an exit surface 103. When the central axis is AX, the intersection of AX with the plane is P0, and in a cross section containing AX, an angle between a line connecting P0 and P on 101 and AX is θr, an angle between a normal to 103 at Q and AX is ϕ, a distance from AX to Q is r, the maximum value of r on 103 is rmax, and θr and ϕ are positive when measured clockwise with respect to AX, ϕ has plural positive local maximum and minimum values as a function of r in0.5rmax≤r, in an area of 103 through which a ray travelling from P0 at a positive angle θr passes, and the shape of 103 is symmetric with respect to AX.