Backlight Unit With Position-Specific Lenses For Brightness Uniformity
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Solution Overview
Problem
Conventional direct-type backlight units for liquid crystal display devices with LEDs arranged in a matrix structure are costly and suffer from uneven brightness, particularly when the circuit board is shorter than the liquid crystal panel, leading to differences in brightness between end areas and other regions.
Innovation Solution
A backlight unit design featuring a substrate with LEDs aligned along one direction, where end lenses and middle lenses are used to enlarge light divergence angles differently, ensuring even brightness distribution by orienting the lenses' divergence angles to address specific areas of the liquid crystal panel, such as the ends and corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LEDs are arranged in a matrix over the entire area of the backlight unit, then brightness uniformity is improved, but the number of light sources and cost increase
Solution Approach 1:
The patent applies local quality by differentiating the lens types based on their positions in the LED array. LEDs at the end positions use end lenses with specific optical characteristics, while LEDs at middle positions use middle lenses with different characteristics. This localized differentiation allows the system to achieve uniform brightness across the entire display area without requiring a complete matrix of LEDs, thereby reducing the total number of light sources needed while maintaining brightness uniformity.
2Quantity of substance
If an elongate circuit board with LEDs arranged in one or two lines is used, then the number of light sources is reduced, but brightness difference between end areas and other areas occurs
Solution Approach 1:
The patent implements local quality by assigning different lens types to different positional groups of LEDs. End lenses are installed on LEDs at the end positions of the circuit board, while middle lenses are installed on LEDs at middle positions. Each lens type is optimized for its specific position to compensate for the natural brightness falloff that occurs in elongated arrangements, thereby eliminating brightness differences between end areas and middle areas while maintaining a reduced number of light sources.
Solution Approach 2:
The patent applies parameter changes by modifying the optical parameters (divergence angles) of the lenses based on their positional parameters. End lenses are designed with specific divergence angles suited for end positions, while middle lenses have different divergence angles optimized for middle positions. This parameter differentiation allows the system to achieve uniform brightness distribution across the display area despite the elongated, space-saving LED arrangement.
3Ease of manufacture
If all lenses have identical light distribution characteristic, then manufacturing is simplified, but brightness difference between end areas and other areas cannot be eliminated
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through positional differentiation of lens types. Instead of using identical lenses everywhere, the system uses end lenses at end positions and middle lenses at middle positions. Each lens type is specifically designed for its location to compensate for positional brightness variations. This approach prioritizes brightness uniformity over manufacturing simplicity, as the different lens types are optimized for their respective positions to eliminate brightness differences across the display area.
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
This design reduces the number of light sources required and effectively eliminates brightness differences between end and middle areas of the liquid crystal panel, enhancing overall brightness uniformity.
Implementation Method 1
an end lens disposed on a light source located toward on an end of the light source area and being for enlarging the divergence angle of the light from the light source
Implementation Method 2
a middle lens disposed on a light source located closer to the middle of the light source area than the light source with the end lens disposed thereon and being for enlarging the divergence angle of the light from the light source
Data Source
AI summary
A backlight unit has a light source area. The width of the light source area in a first direction is shorter than the width of a liquid crystal panel in the first direction. A plurality of LED modules (31) are arranged along the second direction perpendicular to the first direction. End lenses (41A, 41B) and a middle lens (42) for enlarging a light divergence angle are disposed on the plurality of LED modules (31). The direction in which the end lens (41A, 41B) enlarges the light divergence angle differs from that in which the middle lens (42) enlarges the divergence angle. This structure can reduce difference in brightness of the liquid crystal panel, while reducing the number of light sources.