Light Guide for Rollable Reflective Displays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Reflective rollable or wrappable displays face challenges with conventional front-lighting systems due to contrast degradation and thickness issues, making them unsuitable for flexible and thin form factors required for modern displays.
Innovation Solution
A display device with a flexible screen and integrated light source, utilizing a light guide and optics to distribute light evenly and compensate for specular reflections, allowing the screen to be wrappable or rollable while maintaining effective illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional front-lighting system is used for reflective displays, then the display can be illuminated, but contrast degradation occurs due to unwanted out-coupling of light directly towards the viewer
Solution Approach 1:
The patent applies local quality by creating different optical zones within the light guide: a first light guide portion directs light at oblique angles for diffuse reflection, while a second light guide portion directs light at perpendicular angles for specular reflection. This spatial differentiation of light coupling angles resolves the contradiction by providing localized illumination paths that preserve contrast while maintaining overall display illumination.
Solution Approach 2:
The light guide is segmented into distinct portions with different optical functions. The first portion handles oblique light coupling for areas requiring diffuse reflection, while the second portion handles perpendicular light coupling for areas requiring specular reflection. This segmentation allows the system to simultaneously achieve both illumination and contrast preservation that would be impossible with a uniform light guide design.
2Length of moving object
If the display is made thin and flexible for modern applications, then portability and form factor are improved, but conventional front-lighting systems become too thick to integrate
Solution Approach 1:
The patent merges the lighting system with the display structure by integrating the light guide directly into the display assembly. The light guide portions are combined with the display surface, eliminating the need for separate bulky lighting components. This integration resolves the contradiction by achieving thin-form-factor compatibility while maintaining the complexity of the dual-mode illumination system.
Solution Approach 2:
The patent employs thin-film and flexible structure technologies to create a light guide that can be integrated into thin and flexible displays. The light guide is designed as a thin component that can conform to flexible substrates, enabling the entire display assembly to achieve the required thinness and flexibility for modern portable applications.
3Illumination intensity
If light is coupled into the display at oblique angles, then uniform illumination can be achieved, but grey level shifts occur due to viewing angle problems in LCDs
Solution Approach 1:
The patent applies local quality by directing oblique light primarily to regions with diffuse reflective properties where uniform illumination is prioritized, while directing perpendicular light to regions requiring precise grey level control. This spatial differentiation resolves the contradiction by matching light coupling angles to the optical characteristics of different display regions.
Solution Approach 2:
The patent changes the light coupling angle parameter based on the reflective properties of different display regions. By varying the incident angle parameter from oblique to perpendicular depending on the location and type of reflective material, the system achieves both uniform illumination and accurate grey level representation without the viewing angle problems that plague conventional LCDs.
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
Enables thin, flexible, and rollable reflective displays with improved contrast and reduced light loss, suitable for modern display applications by providing uniform illumination and color projection capabilities.
Implementation Method 1
a light-guiding system with a light guide on top of the display, for example. The light guide has out-coupling structures on its surface for coupling the light out towards the reflective display
Implementation Method 2
The display effects of electrophoretic displays do not have the viewing angle problems associated with LCD displays. Rather, the electrophoretic displays are almost perfect (Lambertian) diffuse scatterers of light
Implementation Method 3
A light source is used for emitting light onto the image display for improving image visibility
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A display device includes a housing, a screen connected to the housing and being configured to display data in grey-scale on a first portion of the screen, and at least one light source connected to the housing. The light source is configured to project color content on a second portion of the screen. The screen may be flexible and/or rolloable on a roller included in the housing. The screen may be electrophoretic and/or reflective. The display device may also include optics or a light guide-to-guide light from the light source to the screen. Further, optics may be provided to detect light reflected from the screen and direct more light to portions of the screen having reduced illumination.