Mixed Light Apparatus for LCD Backlight Uniformity
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Solution Overview
Problem
Conventional direct-type backlight modules for LCDs face issues with poor light mixing due to reduced distance between the LED light source and diffusion plate, resulting in yellowish-blue light emission, low energy, and inefficient illumination, especially with divergent radiation angles, which affects color saturation and uniformity.
Innovation Solution
A mixed light apparatus comprising light reflecting elements with focal points for each color LED and a field lens to converge light at a common point, using transparent materials like glass or PMMA, with a field lens positioned to concentrate mixed light, enhancing reflection efficiency and allowing color adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the distance between the LED light source and diffusion plate is shortened to achieve thin and lightweight LCDs, then the thickness and weight of the display device are reduced, but the light mixing becomes poor resulting in yellowish-blue light emission instead of white light
Solution Approach 1:
A field lens is introduced as an intermediary optical element between the LED light source and diffusion plate. The field lens converges the divergent light beams from multiple colored LEDs, enabling effective light mixing over a short distance while maintaining the thin profile of the display device. This intermediary component resolves the contradiction by providing the necessary optical function without increasing the overall thickness.
Solution Approach 2:
The patent changes the optical parameters of the system by introducing a field lens with specific focal length and positioning it at a precise distance from the light source. This parameter adjustment allows the light mixing process to occur effectively within a shortened distance, thereby achieving both thin device profile and high quality white light emission.
2Productivity
If a large number of red, green and blue LEDs are utilized for large-scale LCD production, then the display size is increased, but the emitted white light has low energy and color saturation
Solution Approach 1:
The patent merges the light paths of multiple colored LEDs through a field lens, concentrating their divergent beams into a common convergence region. This merging of light paths increases the energy density and color saturation of the emitted white light, resolving the issue of low energy and poor color saturation in large-scale displays.
Solution Approach 2:
By adjusting the positioning and focal parameters of the field lens, the patent optimizes the convergence of light from multiple LEDs. This parameter optimization ensures that light from a large number of LEDs is effectively concentrated, thereby maintaining high energy and color saturation even in large-scale display applications.
3Illumination intensity
If the color of the mixed light is to be adjusted as desired, then the color saturation and energy of the emitted light are improved, but the device complexity increases
Solution Approach 1:
The field lens serves multiple functions simultaneously: it converges divergent light beams, enables effective light mixing, and allows for color adjustment. This multi-functionality achieves improved color saturation and energy without requiring additional separate components, thereby minimizing the increase in device complexity.
Solution Approach 2:
The patent achieves color adjustment through parameter changes in the field lens positioning and focal length rather than through complex additional optical systems. This approach allows for flexible color control while maintaining relative simplicity of the overall device structure.
4Ease of operation
If lenses are used over point light sources to narrow the light beam, then the illumination direction is controlled, but no suitable lens exists for completely converging light with divergent radiation angles of ±90 degrees
Solution Approach 1:
The field lens acts as an intermediary optical element that specifically addresses the challenge of converging highly divergent light from LED sources. This intermediary component is designed with appropriate focal characteristics to effectively handle the ±90 degree radiation angles, thereby improving illumination efficiency without requiring unavailable specialized lenses.
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 high color saturation, improved uniformity, and increased energy efficiency in light convergence, with illumination efficiency improved to 61% and 70% for ±45 degrees and ±90 degrees radiation angles, respectively, while enabling adjustable color output.
Implementation Method 1
a first light reflecting element 22, a second light reflecting element 23, and a third light reflecting element 24... each of the light reflecting elements 22, 23, and 24 respectively includes a concave structure 223, 233, and 243
Implementation Method 2
a field lens 25... The field lens 25 has a bottom surface 251 and a curved surface 252 extended convexly along an edge of the bottom surface 251
Data Source
AI summary
A mixed light apparatus for mixing light emitted from a first light source and a second light source includes a body, a first light reflecting element, a second light reflecting element and a field lens. The body has a light emitting surface. A first reflecting element extends from the light emitting surface. The first light reflecting element has a first emanating point and a first focal point. The first light source is disposed at the first focal point. A second light reflecting element extends from the light emitting surface. The second light reflecting element has a second emanating point and a second focal point. The second light source is disposed at the second focal point. The first emanating point and the second emanating point overlap at the light emitting surface. The field lens is disposed on the light emitting surface and corresponds to the first and second emanating points.