Color-Scanning Grating Backlight for Passive Displays
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Solution Overview
Problem
Passive electronic displays, such as LCDs and EP displays, lack the ability to emit light, limiting their practical applications due to the need for an external light source, which can be inefficient and restrict their functionality.
Innovation Solution
A color-scanning grating-based backlight system that employs a light guide with diffraction gratings to scatter and direct light in different colors, using a multicolor light source and a scanning protocol to introduce colors sequentially across the light guide, creating a light field with different principal angular directions, allowing for efficient light modulation and reduced bleeding between colors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multicolor light source with scanning protocol is used, then color emission capability is improved, but device complexity increases
Solution Approach 1:
The patent employs a scanning protocol that sequentially activates different color regions of the light source in periodic cycles (e.g., red region first, then green, then blue). This periodic activation allows the backlight to emit multiple colors over time without requiring all color regions to be active simultaneously, thereby achieving versatile color emission while managing device complexity through temporal separation rather than spatial complexity
Solution Approach 2:
The light source is divided into multiple independent color regions (red, green, blue regions with respective red, green, and blue LEDs). Each region can be independently controlled and activated. This segmentation allows the system to emit different colors by selectively activating specific regions, providing color versatility without requiring a completely different light source for each color
2Speed
If diffraction gratings are used to direct light, then light directionality is improved, but manufacturing precision requirements increase
Solution Approach 1:
Different diffraction gratings are designed with different local properties tailored to specific color regions. For example, gratings in the red region have different parameters than those in the green or blue regions. This local optimization allows each grating to efficiently direct its corresponding color while accommodating variations in manufacturing precision across different regions of the light guide plate
Solution Approach 2:
The diffraction grating parameters (such as groove spacing, depth, and shape) are varied across different color regions to optimize light directionality for each wavelength. By changing these parameters locally rather than using a uniform grating design, the system achieves improved light directionality while being more tolerant of manufacturing variations
3Manufacturing precision
If color scanning is implemented, then color separation is improved, but loss of time increases
Solution Approach 1:
The color scanning process operates continuously in cyclic fashion without interruption. While one color region is being activated, the system is already preparing to activate the next region. This continuous cyclic operation ensures that color separation is maintained while minimizing the time penalty, as the scanning protocol flows seamlessly from one color to the next without stopping or resetting
Solution Approach 2:
The scanning protocol is pre-synchronized with the light valve modulation timing. Before a color region is activated, the corresponding light valve pixels are already prepared with the appropriate image data. This preliminary preparation eliminates delays during color transitions, achieving good color separation without significant time loss
4Adaptability or versatility
If external light sources are removed, then display autonomy is improved, but illumination intensity decreases
Solution Approach 1:
The patent merges the light source function and the color filtering function into a single integrated component - the multicolor light guide plate with embedded diffraction gratings. This integration eliminates the need for separate external light sources and color filters, achieving display autonomy. The merged structure uses the light guide plate itself to both generate light (via embedded LEDs) and direct/separate colors (via diffraction gratings), maintaining illumination intensity while removing external dependencies
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 solution enables passive displays to function similarly to active displays by emitting modulated light with reduced color bleeding, supporting dynamic 2D and 3D color electronic display applications without the need for external light sources, enhancing their practicality and performance.
Implementation Method 1
a light guide with diffraction gratings to scatter and direct light in different colors
Implementation Method 2
employs a light guide with diffraction gratings to scatter and direct light
Implementation Method 3
a light guide with diffraction gratings
Data Source
Figure 1A~1B
Figure 1C~2A
Figure 2B~3A
AI summary
Color-scanning grating-based backlighting includes a color scanning protocol to provide different colors of light in different regions of a plate light guide with an intervening dark region. A color-scanning grating-based backlight includes the plate light guide and a diffraction grating configured to diffractively couple out a portion of a guided light beam as a coupled-out light beam directed away from a plate light guide surface at a predetermined principal angular direction. The backlight further includes a multicolor light source configured to provide the different colors of light to the plate light guide as the guided light beam according to the color scanning protocol. Provided light of a first color in a first region is separated from provided light of a second color in a second region one or both by the intervening dark region and by a light-confining wall of the plate light guide.