PDLC Display Illumination With Diffractive Luminance Equalization
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Solution Overview
Problem
Display devices using polymer dispersed liquid crystal experience a decrease in luminance with increasing distance from the light source, leading to non-uniform luminance across the display area.
Innovation Solution
Incorporation of a diffractive optical element that diffracts illumination light to ensure uniform luminance across the display area by adjusting the diffraction efficiency and direction of light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a light source is provided along the side surface of a transparent substrate, then the display device can be constructed with a simple structure, but the luminance decreases with increasing distance from the light source resulting in non-uniform luminance
Solution Approach 1:
A light guide plate is introduced as an intermediary component between the light source and the display panel. The light guide plate receives light from the side-mounted light source and redistributes it across the display area through its internal structure, achieving uniform luminance without requiring a complex multi-source configuration.
Solution Approach 2:
The patent transitions from direct linear light propagation to two-dimensional light distribution by using a light guide plate with specific cross-sectional structures. The light is redirected from a one-dimensional source path into a two-dimensional uniform illumination pattern across the display surface.
2Illumination intensity
If multiple light sources are arranged to improve luminance uniformity, then luminance uniformity improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts the light distribution function from the light sources themselves and transfers it to a dedicated light guide plate. This allows a single light source to perform the work that would otherwise require multiple light sources, simplifying the overall structure while maintaining uniform luminance.
3Area of stationary object
If the light source is placed at a distance from the display panel, then there is sufficient space for other components, but the luminance intensity decreases
Solution Approach 1:
The light guide plate serves as a mediator that bridges the gap between the remotely positioned light source and the display panel. It captures light at a distance from the panel and actively transports and distributes it across the display area, maintaining high luminance intensity despite the increased separation distance.
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 solution improves luminance uniformity by controlling the distribution of light across the display area, ensuring consistent illumination regardless of distance from the light source.
Implementation Method 1
a diffractive optical element which faces the first surface, is provided at a position which does not overlap the liquid crystal layer, and is configured to diffract the illumination light
Data Source
AI summary
According to one embodiment, a display device includes a first transparent substrate, a second transparent substrate which has a first surface and a second surface different from the first surface, a liquid crystal layer which is located between the first transparent substrate and the second transparent substrate and contains a polymer dispersed liquid crystal, a light emitting unit configured to emit illumination light for illuminating the liquid crystal layer, and a diffractive optical element which faces the first surface, is provided at a position which does not overlap the liquid crystal layer, and is configured to diffract the illumination light.