Coherent Backlight Unit for 3D Display
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Solution Overview
Problem
Current three-dimensional (3D) image display devices face challenges in achieving high optical efficiency and effective 3D image rendering, particularly in glass-free types that rely on directional backlight units, which often suffer from light leakage and inefficient optical path utilization.
Innovation Solution
The implementation of a coherent backlight unit featuring a light guide plate with diffraction gratings and reflective optical elements, such as retro-reflective or mirror surfaces, to manage coherent light propagation and exit angles, ensuring a single optical path and enhanced optical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a glass-free 3D image display device uses a directional backlight unit system, then it eliminates the need for special glasses, but it suffers from light leakage and inefficient optical path utilization
Solution Approach 1:
The patent segments the optical path into distinct functional zones using multiple diffraction gratings (first, second, and third gratings) positioned at different locations and orientations. Each grating handles specific light redirection tasks, creating segmented optical paths that prevent light leakage while maintaining directional control for glass-free 3D display operation
Solution Approach 2:
The patent introduces vertical layering of diffraction gratings at different positions and angles, transforming the optical control from a single-plane approach to a multi-dimensional spatial arrangement. This dimensional expansion enables precise light path management that eliminates leakage while preserving optical efficiency in the glass-free configuration
2Use of energy by moving object
If diffraction gratings are used to control light direction, then optical path utilization improves, but light leakage occurs at interfaces and edges
Solution Approach 1:
The patent introduces a reflective optical element as an intermediary component between the light guide plate and the third diffraction grating. This mediator redirects light that would otherwise leak at interfaces, capturing straying light rays and redirecting them through the third grating to maintain optical efficiency while preventing harmful light leakage
Solution Approach 2:
The patent converts the potentially harmful light leakage at edges and interfaces into a beneficial resource by using the reflective optical element to capture these straying light rays and redirect them through the third diffraction grating. This transforms wasted light into useful illumination, improving overall optical efficiency while eliminating the harmful leakage effect
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 significantly increases the optical efficiency of the coherent backlight unit, reducing light leakage and ensuring uniform image output by controlling the exit angle of coherent light, thereby improving the overall performance of 3D image display devices.
Implementation Method 1
a first diffraction grating provided on either the first flat panel surface or the second flat panel surface and configured to diffract the coherent light irradiated from the light source toward an inner side of the light guide plate
Implementation Method 2
a second diffraction grating provided on the first flat panel surface and configured to discharge the coherent light that is totally reflected by the light guide plate to the outside of the light guide plate
Implementation Method 3
a reflective optical element provided on at least one of a plurality of side surfaces of the light guide plate and configured to reflect the coherent light that propagates toward one of the side surfaces from the inner side of the light guide plate toward the inner side of the light guide plate
Data Source
AI summary
A coherent backlight unit and a 3D image display device including the coherent backlight unit are provided. The coherent backlight unit includes a light source, a light guide plate, a first diffraction grating, a second diffraction grating, and a reflective optical element. The light source irradiates a coherent light and the reflective optical element reflects the coherent light that is propagating toward one of the side surfaces from the inner side of the light guide plate toward the inner side of the light guide plate.