Symmetric LED Light Bar for Uniform Backlight Illumination
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Solution Overview
Problem
Conventional LED units in back light units for liquid crystal displays suffer from a lack of color uniformity across the light guide plate, leading to inconsistent illumination.
Innovation Solution
A light bar comprising multiple instances of a repetition unit with a symmetric sequence of at least three types of light emitting devices, including LEDs that emit light at different peak wavelengths, is integrated into a back light unit. The light bar is designed such that the first and last LEDs emit the same color light, and is optically coupled with a light guide plate and a reflector to direct light perpendicular to the guide plate, ensuring uniform light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LED units are fabricated by mounting LEDs to a substrate and optically coupling them to a light guide plate, then the structure is simple and easy to manufacture, but color uniformity across the light guide plate deteriorates
Solution Approach 1:
The patent applies asymmetry by using a symmetric sequence of LEDs at the ends of the light bar that mirrors the color composition. Specifically, the first and last LEDs emit the same color light, and the sequence of LEDs symmetrically about the center emits complementary colors, creating a symmetric color distribution pattern that compensates for edge effects and achieves uniform chromaticity across the display.
Solution Approach 2:
The patent applies local quality by differentiating the LED sequences at different positions along the light bar. The symmetric sequence at the ends differs from the central region, with specific LEDs positioned to emit particular colors (red, green, blue) in a mirrored pattern. This localized variation in LED color composition compensates for spatial non-uniformities in light extraction and achieves uniform chromaticity across the entire display area.
2Manufacturing precision
If LEDs of different types are arranged in a symmetric sequence with first and last LEDs emitting the same color, then color uniformity and chromaticity are improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the light bar into multiple discrete LED positions arranged in a symmetric sequence. The LED array is segmented into specific groups (first LED, second and third LEDs, fourth and fifth LEDs, sixth LED) with predetermined color emissions. This segmentation allows precise control over color distribution while maintaining a relatively simple overall structure that can be manufactured using standard LED mounting techniques.
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 enhances corner uniformity and overall chromaticity across the display by reducing color non-uniformity, providing a more uniform light distribution compared to conventional systems.
Implementation Method 1
a light bar for an integrated back light unit... multiple instances of a repetition unit... at least three types of light emitting devices... LEDs that emit light at different peak wavelengths
Implementation Method 2
a reflector located on a face of the light guide plate and including extraction features configured to direct light from the light emitting devices of the light bar along a direction substantially perpendicular to the face of the light guide plate
Data Source
AI summary
A light bar includes a plurality of light emitting diode (LED) clusters which extend along a lengthwise direction of the light bar from a first end of the light bar to an opposite second end of the light bar. Each LED cluster includes at least three different types of LEDs. A first LED at the first end of the light bar and a last LED at the second end of the light bar emit the same color light.