Direct-Lit Backlight Reflectors for Uniform Illumination
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Solution Overview
Problem
Direct-lit backlit displays can be bulky and produce non-uniform backlight illumination if not properly designed, leading to issues with dynamic range and visual quality.
Innovation Solution
The use of a backlight unit with a two-dimensional array of light-emitting diodes and a reflector with a cross-sectional profile featuring parabolic or elliptical portions, combined with a diffuser and a partially reflective layer, helps to distribute light uniformly across the display, enhancing illumination uniformity and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If direct-lit backlight units use arrays of light-emitting diodes to emit light vertically through the display, then dynamic range can be enhanced with locally dimmable LEDs, but the display becomes bulky and produces non-uniform backlight illumination
Solution Approach 1:
The backlight unit is divided into multiple independently controllable cells, each containing one or more light-emitting diodes. This segmentation enables local dimming control where different regions can be dimmed independently, improving illumination uniformity and dynamic range while maintaining a compact overall structure.
Solution Approach 2:
Different regions of the backlight unit are assigned different optical properties and control characteristics. Edge regions have optimized light extraction and reflection properties to prevent hotspots, while center regions have different characteristics. This local optimization allows uniform illumination across the display without requiring excessive thickness.
2Illumination intensity
If direct-lit backlight units use arrays of light-emitting diodes to emit light vertically through the display, then dynamic range can be enhanced with locally dimmable LEDs, but the display becomes bulky and produces non-uniform backlight illumination
Solution Approach 1:
Multiple functional elements are merged into integrated components. The cell structure combines light-emitting diodes, reflectors, and optical elements into a single modular unit. This merging reduces the number of separate components and simplifies assembly while achieving uniform illumination through careful integration of these elements.
Solution Approach 2:
The cell structure serves multiple functions simultaneously: it contains the light-emitting diode, provides reflective surfaces for light management, defines the optical path, and enables local dimming control. This multi-functionality reduces the need for separate dedicated components, simplifying the overall device complexity.
3Illumination intensity
If light-emitting diodes are placed in respective cells with reflectors having parabolic or elliptical profiles, then light distribution uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The reflector surfaces within each cell are given curved profiles, specifically parabolic or elliptical cross-sections. These curved surfaces optimize light reflection and distribution patterns, directing light uniformly across the display area. The curvature is designed to redirect light from the LED source evenly across the cell aperture, improving illumination uniformity.
Solution Approach 2:
The reflector geometry is optimized by adjusting key parameters such as curvature radius, focal positions, and surface profiles. By carefully selecting and tuning these geometric parameters, the reflector achieves optimal light distribution characteristics. This parameter optimization allows standard manufacturing processes to produce the curved surfaces with acceptable precision.
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 ensures more uniform backlight illumination and improved dynamic range by recycling light near the center of each cell while allowing light near the edges to pass directly through, reducing hotspots and enhancing overall visual quality.
Implementation Method 1
a light reflector that helps reflect light from the light-emitting diodes through the pixel array
Implementation Method 2
A diffuser in the display may be used to homogenize light from the array of light-emitting diodes
Implementation Method 3
The stack of dielectric layers may form a thin-film interference filter with an angularly dependent transmission
Implementation Method 4
A partially reflective layer may be interposed between the diffuser and the array of light-emitting diodes
Implementation Method 5
Direct-lit backlight units have arrays of light-emitting diodes that emit light vertically through the display
Implementation Method 6
light-emitting diodes that emit light into an edge surface of a light guide plate
Implementation Method 7
A phosphorescent layer and other optical films may overlap the diffuser
Data Source
AI summary
An array of pixels in a display may be illuminated by a backlight having an array of light-emitting diodes in an array of respective cells. A reflector is used to reflect light from the light-emitting diodes through the array of pixels. Within the cells, the reflector has cross-sectional profiles that help distribute light emitted from the light-emitting diodes toward edges of the cells. A light diffuser layer for the backlight may have a partially reflective layer such as a thin-film interference filter with an angularly dependent transmission. Within each cell, the reflector may have cross-sectional profiles with portions that are parabolic or elliptical.