Lens Sheet Prism Deflection for LED Color Uniformity
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Solution Overview
Problem
Conventional illumination devices using pseudo white LEDs suffer from color unevenness due to varying wavelengths of light emitted, with lights closer to the optical axis tending to have a blue hue and those farther away having a yellow hue, resulting from differential wavelength conversion by the fluorescent material.
Innovation Solution
An illuminating device with a light source and a lens sheet comprising symmetrically arranged prisms, where the first lens group has prisms with inclined faces facing the optical axis, and the second lens group includes reflecting prisms, allowing for controlled deflection of exiting lights to reduce color unevenness without impairing brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a pseudo white LED with fluorescent material is used as a light source, then the device can achieve white light illumination, but color unevenness occurs where lights closer to the optical axis have a blue hue and those farther away have a yellow hue
Solution Approach 1:
The lens sheet is divided into multiple lens groups (first lens group with refracting prisms adjacent to the optical axis, and second lens group with reflecting prisms farther from the optical axis). Each lens group independently processes light from different regions of the LED, allowing separate optimization of light paths to achieve uniform color distribution across the illumination output.
Solution Approach 2:
Different regions of the lens sheet are assigned different optical functions: the first lens group uses refracting prisms with specific inclination angles optimized for central light paths, while the second lens group uses reflecting prisms optimized for peripheral light paths. This local differentiation compensates for the varying wavelength conversion effects in different regions of the LED.
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 ensures uniform exit angles and effective mixing of light, reducing color unevenness and enhancing chromaticity distribution, thereby improving the illumination quality.
Implementation Method 1
A blue light emitted from the blue LED 102, while traveling through the transparent resin 106 disposed in the lamp house 104, is diffused, also at the same time is subjected to wavelength conversion by the yellow color fluorescent material 108 into a yellow color fluorescence
Implementation Method 2
The exit angles of the exiting lights L emitted from the pseudo white LED 100 are deflected by both the first lens group 112 and the second lens group 114 so as to travel in the direction parallel to the optical axis C
Implementation Method 3
a second lens group 114 which is composed of reflecting prisms (TIR: total internal reflection) and which is arranged outwardly to be located away from the optical axis C of the pseudo white LED 100
Data Source
AI summary
In an illuminating device, when exiting lights come out from a lens sheet, the optical paths of the exiting lights are deflected in a direction opposite to an optical axis of a light source by means of a plurality of prisms which are included in a first lens group arranged on an inward side of the lens sheet located adjacent to the optical axis of the light source and each of which has a inclined face facing toward the optical axis of the light source, wherein the exiting lights from the light source via the first lens group of the lens sheet are adapted to mix with exiting lights from the light source via a second lens group located outside the first lens group, whereby the degree of color unevenness is reduced, that appears inherently when a pseudo white LED is used as the light source of the illuminating device.