Intersecting Light Guide Arrays for Local Dimming in Slim Backlight Units
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Solution Overview
Problem
The existing liquid crystal displays using edge type backlight units face challenges in implementing local dimming due to the difficulty in reducing thickness while maintaining luminance evenness, as the space between the light sources and the diffusion plate is necessary for light diffusion, leading to increased cost and limitations in improving contrast properties.
Innovation Solution
A backlight unit is designed with a first and second light guide plate array intersecting each other, forming matrix-shaped blocks, and equipped with light arrays at the ends of the light guide plates, which allows for independent control of light sources to achieve local dimming, thereby improving contrast and reducing thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the space between light sources and diffusion plate is narrowed to reduce thickness, then the backlight unit becomes thinner, but luminance evenness deteriorates due to insufficient light diffusion
Solution Approach 1:
The light guide plate is divided into multiple segmented light guide plates with different refractive indices arranged in layers. This segmentation allows each layer to contribute differently to light diffusion, achieving sufficient luminance evenness in a narrower space without requiring a large distance between light sources and diffusion plate.
Solution Approach 2:
Different regions of the light guide plate structure are assigned different optical properties. The segmented light guide plates have different refractive indices, creating local quality variations that optimize light diffusion characteristics at each layer, enabling effective light distribution even with reduced overall thickness.
2Illumination intensity
If local dimming is implemented using direct type backlight unit with multiple light sources, then contrast property is improved, but thickness increases due to space requirements for light diffusion
Solution Approach 1:
The backlight unit is divided into multiple independently controllable light sources arranged in an array, allowing local dimming control. The segmented light guide plates with different refractive indices enable each light source region to be controlled independently while maintaining thin overall structure.
Solution Approach 2:
Instead of using a single diffusion plate in one dimension, the invention uses multiple light guide plates stacked in the thickness direction (adding a new dimension). This vertical stacking allows light diffusion to occur through multiple layers, achieving effective diffusion without increasing the horizontal space required.
3Illumination intensity
If the number of light sources is increased to improve luminance evenness, then luminance evenness is improved, but device complexity and cost increase
Solution Approach 1:
Rather than increasing the number of light sources, the invention achieves luminance evenness by assigning different refractive indices to different light guide plate layers. This optical property variation creates local quality differences that naturally distribute light more evenly without requiring additional light sources.
Solution Approach 2:
The invention changes the refractive index parameter of the light guide plates to achieve better light diffusion. By selecting light guide plates with different refractive indices, the system optimizes light distribution characteristics without increasing the number of light sources, thereby reducing device complexity and cost.
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 solution enables effective local dimming in liquid crystal displays with edge type backlight units, enhancing contrast and luminance evenness while maintaining a slim design, as demonstrated by improved luminous flux distribution and reduced luminance differences between blocks.
Implementation Method 1
a first light guide plate array including a plurality of first light guide plates arranged in parallel in a first direction to define a plurality of first light guide channels; a second light guide plate array including a plurality of second light guide plates arranged in parallel in a second direction intersected with the first direction to define a plurality of second light guide channels
Data Source
AI summary
A backlight unit capable of improving contrast properties by implementing a local dimming method while making the backlight unit slim, and a liquid crystal display using the same are provided. The backlight unit includes a first light guide plate array including a plurality of first light guide plates arranged in parallel in a first direction to define a first light guide channels; a second light guide plate array including a plurality of second light guide plates arranged in parallel in a second direction intersected with the first direction to a second light guide channels; a first light array arranged near at least one end of the first light guide plate array to illuminate light to the at least one end of the first light guide plate array; and a second light array arranged near at least one end of the second light guide plate array to illuminate light to the at least one end of the second light guide plate array.