Backlight Module Grating Collimation for Display Devices
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Solution Overview
Problem
Current backlight modules have a poor collimation effect for light rays from point light sources other than those at their focal planes due to the limited collimating function of lenses, resulting in inefficient light distribution.
Innovation Solution
A backlight module comprising a light guide plate, a light source, a first grating that adjusts light ray propagation directions to exceed the critical angle of total reflection, and a second grating that collimates these adjusted rays to travel perpendicular to the light guide plate, with multiple sub-gratings and half transmitting and half reflective films to ensure even light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lenses are used to collimate light rays from point light sources, then light rays from focal plane sources are collimated, but light rays from other point light sources are not collimated resulting in poor overall collimation effect
Solution Approach 1:
The light guide plate is divided into multiple regions, each equipped with gratings having different grating constants. This segmentation allows each region to handle light from specific light sources independently, achieving both precise collimation for each source and overall good collimation effect across all sources.
Solution Approach 2:
Different regions of the light guide plate are assigned different grating constants tailored to their specific light sources. This local quality approach ensures that each region optimally collimates light from its corresponding light source, resolving the contradiction between precision for specific sources and adaptability to multiple sources.
2Ease of operation
If a single grating is used to adjust light propagation directions, then light can be redirected, but light distribution uniformity is poor
Solution Approach 1:
The grating system is segmented into multiple gratings with different grating constants arranged in specific patterns. This segmentation enables different parts of the light guide plate to redirect light at different angles, achieving both effective light direction control and uniform light distribution across the exit surface.
Solution Approach 2:
Gratings with different grating constants are asymmetrically distributed across the light guide plate regions. This asymmetric arrangement ensures that light from different positions is redirected appropriately to achieve uniform overall distribution, resolving the contradiction between directional control and distribution uniformity.
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
Significantly improves the collimation of light rays, ensuring that most light rays exit perpendicular to the light guide plate, enhancing the overall light distribution and reducing leakage, thereby improving the display quality in devices like mobile phones and TVs.
Implementation Method 1
a first grating provided at the first region and configured to adjust propagation directions of the light rays
Implementation Method 2
the included angle is greater than the critical angle of total reflection of the light guide plate
Implementation Method 3
a second grating provided at the second region and configured to collimate the adjusted light rays
Data Source
AI summary
A backlight module includes: a light guide plate; a light source for emitting light rays towards a first region of the light guide plate; a first grating provided at the first region and configured to adjust propagation directions of the light rays such that the adjusted light rays travel towards a second region of the light guide plate, and the propagation directions make an included angle with a normal to the light guide plate which is greater than the critical angle of total reflection of the light guide plate; and a second grating provided at the second region and configured to collimate the adjusted light rays such that the collimated light rays travel in a direction perpendicular to the light guide plate.