Local Dimming Unit for Edge-Type Backlight Light Guide Plate
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Solution Overview
Problem
Display apparatuses with edge-type backlight units face challenges in achieving precise local dimming, which affects contrast ratio and leads to light loss.
Innovation Solution
Incorporating a local dimming unit with an electro-optical layer that changes optical properties based on an electric field, controlled by a controller to adjust voltage applied to electrodes, allowing for precise light reflection or scattering according to image luminance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an edge-type backlight unit is used to achieve uniform brightness and thin thickness, then the backlight can be implemented with a small number of light sources, but it has a narrow area capable of realizing local dimming and difficulty in precisely controlling local dimming
Solution Approach 1:
The patent divides the backlight unit into multiple independently controllable regions by segmenting the light guide plate into several sections, each with its own dimming control. This allows precise local dimming control in the edge-type backlight unit by treating each segment separately, resolving the contradiction between using fewer light sources and achieving precise local dimming control.
Solution Approach 2:
The patent applies different optical properties to different regions of the light guide plate, with each region having tailored refractive indices and absorption coefficients optimized for its specific location. This enables precise control of light distribution in each local area, allowing accurate local dimming while maintaining the overall efficiency of the edge-type backlight structure.
2Illumination intensity
If local dimming is implemented to improve contrast ratio, then image quality is enhanced, but light loss increases
Solution Approach 1:
The patent dynamically adjusts optical parameters such as refractive index and absorption coefficient in different regions of the light guide plate based on image content requirements. By changing these parameters selectively, the system achieves high contrast ratio where needed while minimizing light loss in other regions, resolving the contradiction between improving contrast and reducing energy loss.
Solution Approach 2:
The patent implements a feedback control mechanism that monitors the actual light distribution and contrast ratio, then adjusts the dimming control parameters accordingly. This feedback system ensures that local dimming is applied only when and where necessary to achieve the desired contrast ratio, minimizing unnecessary light loss while maintaining optimal image quality.
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 enhances the contrast ratio by enabling precise local dimming while minimizing light loss, improving image quality and efficiency.
Implementation Method 1
an electro-optical layer configured to change optical properties according to an electric field
Implementation Method 2
The light incident on the light guide plate may move from the side of the light guide plate to the center through total internal reflection inside the light guide plate
Implementation Method 3
a local dimming unit configured to reflect or scatter light emitted through the second surface of the light guide plate according to a location
Data Source
AI summary
A display apparatus includes a plurality of light sources configured to emit light; a light guide plate having a first surface and a second surface, configured to spread light emitted from the plurality of light sources therein to emit light through the first surface; and a local dimming unit configured to reflect or scatter light emitted through the second surface of the light guide plate according to a location. The local dimming unit may include an electro-optical layer configured to change optical properties according to an electric field; a plurality of electrodes located on the same plane, configured to generate the electric field; and a controller configured to change a voltage applied to the plurality of electrodes according to an image.