Backlight Lens Design for Uniform Light Distribution
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Solution Overview
Problem
Conventional liquid crystal display (LCD) backlight units with isotropic lenses face challenges in dispersing light efficiently, particularly in achieving circular isotropic light distribution, as the pitch between light sources increases with fewer sources, leading to difficulties in maintaining uniform brightness and luminance.
Innovation Solution
The implementation of a secondary lens with a concentric, cylindrical shape and an aspheric top surface portion that refracts and reflects light anisotropically, combined with a reflective layer and light guide layer, to achieve anisotropic light distribution and improve light efficiency and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of light sources is reduced, then device complexity is reduced, but light distribution uniformity deteriorates
Solution Approach 1:
A secondary lens is introduced as an intermediary optical element between the light source and the display panel. This secondary lens receives light from the first lens and redistributes it through its own optical path, effectively mediating the light distribution to achieve uniformity even with reduced light source count
Solution Approach 2:
The optical system combines multiple lens types (first lens with specific refractive index, second lens with different refractive index) to create a composite optical structure. Each lens material is optimized for specific functions, and their combination achieves superior light distribution that cannot be obtained with a single lens type
2Device complexity
If the pitch between light sources increases, then device complexity is reduced, but light distribution uniformity deteriorates
Solution Approach 1:
The patent transitions from a single-plane light source arrangement to a multi-dimensional optical path by introducing the secondary lens that creates additional light redistribution paths. This dimensional expansion in the optical system allows compensation for the increased pitch between light sources
Solution Approach 2:
The patent optimizes specific optical parameters including the refractive indices of the lens materials, the curvature radii of the lens surfaces, and the thicknesses of the lenses. By precisely controlling these parameters, the system achieves uniform circular light distribution despite increased light source pitch
3Ease of manufacture
If isotropic light distribution is used, then ease of manufacture is improved, but light efficiency deteriorates due to hot-spots
Solution Approach 1:
The patent implements local quality optimization by designing the secondary lens with spatially varying optical properties. Different regions of the lens have different curvature radii and refractive index characteristics, allowing localized control of light paths to prevent concentration in specific areas and eliminate hot-spots
Solution Approach 2:
The patent employs curved surface designs for both lenses, with the secondary lens featuring specific curvature radii on its first and second surfaces. These curved geometries naturally distribute light more evenly compared to flat surfaces, reducing hot-spot formation while maintaining manufacturability
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 light distribution, reduces hot-spots, and maintains uniform brightness even with fewer light sources, resulting in improved image quality and a slimmer display apparatus.
Implementation Method 1
a lens provided over a corresponding the light emitting device... which refracts and reflects light anisotropically
Implementation Method 2
a lens provided over a corresponding the light emitting device... which refracts and reflects light anisotropically
Data Source
AI summary
Provided is a display apparatus. The display apparatus may include a display panel and a backlight provided adjacent the display panel. The backlight may include an optical sheet provided adjacent the display panel, a reflector provided a prescribed distance from the optical sheet, at least one light emitting device provided adjacent the reflector, and a lens provided over a corresponding the light emitting device. The lens may include a lower recess formed on a bottom surface of the lens and provided a prescribed distance over the light emitting device, and an upper recess formed on a top surface of the lens and provided to vertically overlap the bottom recess. The lower recess may include an upper surface that extends from the side surface and having a prescribed shape and curvature. The upper recess may also include a lower surface having a prescribed shape and curvature.