Backlight Unit Local Dimming via Grooved Light Guide Plate
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Solution Overview
Problem
Edge-type backlight units face challenges in achieving local dimming while maintaining thinness and low power consumption, often resulting in reduced light uniformity due to hot spots caused by LED placement within the light guide plate.
Innovation Solution
The design incorporates a light guide plate with inverse prism patterns and grooves, along with a reflective layer, to direct light emission and reduce hot spots, eliminating the need for additional diffusion or prism sheets, thereby enhancing light uniformity and contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the light source is located on the side of the light emitting surface of the light guide plate (edge type), then the entire thickness is small and fewer light sources are required, but it is difficult to perform local dimming which divides the light emitting surface into a plurality of sections
Solution Approach 1:
The light guide plate is divided into multiple independent light guide regions by groove structures. Each region can independently control light emission, enabling local dimming functionality while maintaining the thin edge-type structure. The grooves physically separate the light guide plate into distinct sections that can be individually controlled.
Solution Approach 2:
Different regions of the light guide plate are designed with different optical properties through the groove structures and inverse prism patterns. This allows each local region to have tailored light guiding and emission characteristics, enabling selective dimming of specific areas while maintaining overall thinness.
2Object-affected harmful factors
If additional diffusion sheet and prism sheet are disposed on the light guide plate to solve the hot spot problem, then the hot spot issue is addressed, but it is complicated to individually form each backlight unit and assembly them, and there are problems of increase of the entire thickness, cost increase, and optical loss at the interface between the sheets
Solution Approach 1:
The diffusion and light guiding functions are merged into a single integrated light guide plate structure. The inverse prism patterns are directly formed on the light guide plate surface, eliminating the need for separate diffusion sheets and prism sheets. This integration simplifies manufacturing and assembly while reducing optical losses at interfaces.
Solution Approach 2:
The light guide plate incorporates multiple functional elements (grooves for diffusion, inverse prism patterns for light extraction) within a single composite structure. This allows the plate to simultaneously achieve hot spot elimination, uniform light distribution, and effective light extraction without requiring multiple separate components.
3Adaptability or versatility
If the light source is arranged in a 2-dimensional manner below the light emitting surface (directly downward type), then it is easy to perform local dimming, but the entire thickness of the liquid crystal display device is very large and a plurality of light sources are required
Solution Approach 1:
The light source arrangement transitions from a 2-dimensional array below the display to a 1-dimensional linear arrangement at the edge. The light guide plate then distributes this linear light source across the entire display area using optical guiding principles, achieving both thinness and local dimming capability through optical path control rather than spatial arrangement.
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 configuration allows for effective local dimming with improved light uniformity and reduced optical loss, maintaining a thin profile and low power consumption, while simplifying manufacturing and reducing costs.
Implementation Method 1
a reflective layer which is disposed within the one or the plurality of grooves and reflects light emitted from the light emitting device
Implementation Method 2
a plurality of inverse prism patterns disposed in the top surface
Data Source
AI summary
A backlight unit may be provided which is capable of local dimming. The backlight unit includes: one or a plurality of light emitting devices; and a light guide plate including a top surface and a bottom surface, one or a plurality of grooves which are formed in the bottom surface and in which the light emitting device is disposed, a reflective layer which is disposed within the one or the plurality of grooves and reflects light emitted from the light emitting device, and a plurality of inverse prism patterns disposed in the top surface.