Unidirectional Grating Backlight Light Intensity
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Solution Overview
Problem
Passive electronic displays, which rely on external light sources for illumination, face limitations in practical applications due to their inability to emit light, necessitating the use of backlights to function effectively.
Innovation Solution
A unidirectional grating-based backlight system that employs a diffraction grating to couple light out of a light guide and redirect secondary light beams, enhancing light intensity by combining primary and reflectively redirected secondary light beams, allowing for improved brightness and efficiency, and enabling the display of three-dimensional information without the need for glasses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional backlight system is used to illuminate passive displays, then the displays can function effectively, but the light intensity and brightness are insufficient
Solution Approach 1:
A light guide plate is introduced as an intermediary component between the backlight and the display. The light guide plate captures stray light at oblique angles and redirects it toward the viewer through its top surface, effectively mediating the light path to improve brightness while maintaining energy efficiency
Solution Approach 2:
The patent employs a wavelength-selective reflective layer that exhibits angle-dependent reflectivity characteristics. This layer selectively reflects certain wavelengths (colors) of light at specific angles, creating a viewing-angle-dependent color effect that enhances perceived brightness in the forward direction while managing energy distribution across different wavelengths
2Illumination intensity
If the backlight emits light in multiple directions, then the light distribution is broad, but the light intensity in the viewing direction is reduced
Solution Approach 1:
The light guide plate is designed with asymmetric optical properties - the bottom surface has high reflectivity to redirect light upward, while the top surface has specific optical characteristics that favor forward direction light extraction. This asymmetric design concentrates light intensity in the viewing direction while maintaining adequate light distribution
Solution Approach 2:
Different surfaces of the light guide plate are given different optical qualities: the bottom surface is highly reflective to redirect stray light, while the top surface has controlled extraction properties. This local differentiation of optical properties optimizes light intensity in the viewing direction without completely sacrificing light distribution versatility
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
The system significantly enhances light intensity and efficiency, enabling passive displays to function more effectively as active displays, particularly in three-dimensional electronic displays, by utilizing the reflective redirection of secondary light beams to create a brighter and more efficient light field.
Implementation Method 1
A unidirectional grating-based backlight system that employs a diffraction grating to couple light out of a light guide and redirect secondary light beams
Implementation Method 2
an angularly selective reflective layer within the light guide is employed to reflectively redirect a diffractively produced, secondary light beam
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3~4
AI summary
Unidirectional grating-based backlighting includes a light guide and a diffraction grating at a surface of the light guide. The light guide is to guide a light beam and the diffraction grating is configured to couple out a portion of the guided light beam using diffractive coupling and to direct the coupled-out portion away from the light guide as a primary light beam at a principal angular direction. The diffraction grating is to further produce a secondary light beam directed into the light guide at an opposite one of the principal angular direction. The unidirectional grating-based backlighting further includes an angularly selective reflective layer within the light guide adjacent to the light guide surface that is configured to reflectively redirect the diffractively produced, secondary light beam out of the light guide in the direction of the primary light beam.