Liquid-Crystal Display Backlight with Variable Angle Injection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LCD display backlights consume excessive power due to directing light over a wide range of incidence angles, resulting in only a small fraction of light being received by the viewer's pupils, with the remainder being wasted.
Innovation Solution
Implementing an imaging system to track viewer pupils and adjust the direction of display light emission, concentrating light into the viewer's pupils while reducing light emission elsewhere, using a light-extraction layer with diffractive features and injection optics to control light injection angles into a waveguide, allowing for efficient light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the LCD backlight emits light over a wide range of incidence angles to ensure viewability, then the display is viewable over wide angles, but most of the light is wasted and not received by the viewer's pupils
Solution Approach 1:
The patent applies local quality by directing light from different zones of the backlight to different angular ranges. Each zone's light is directed at a specific angle corresponding to the viewer's pupil position, rather than emitting light uniformly in all directions. This localized angular distribution ensures that light is concentrated where needed (at the pupil) rather than wasted in unused angular ranges.
Solution Approach 2:
The patent implements dynamics by making the backlight's light emission angles adjustable and responsive to viewer position. The system dynamically changes the angular distribution of light based on real-time detection of pupil locations, transitioning from a static wide-angle emission pattern to a dynamic, viewer-adapted pattern that concentrates light efficiently.
2Illumination intensity
If a highly emissive backlight is used to ensure sufficient brightness in bright ambient conditions, then the display remains viewable, but power consumption increases excessively
Solution Approach 1:
The patent applies parameter changes by adjusting the angular distribution parameters of backlight emission rather than simply increasing overall intensity. By changing the emission pattern from wide-angle to concentrated angular ranges and optimizing the luminous output parameters of individual backlight zones, the system achieves sufficient perceived brightness while reducing total power consumption.
Solution Approach 2:
The patent implements partial action by activating or emphasizing only the portions of the backlight that contribute to useful illumination (light reaching the pupil). Rather than operating the entire backlight at full intensity, the system applies partial intensity to relevant zones and reduces or eliminates emission in irrelevant angular ranges, achieving adequate brightness with reduced energy expenditure.
3Ease of operation
If the backlight directs light over wide incidence angles, then the display can be viewed from different positions, but only a small fraction of light is received by the viewer's pupils
Solution Approach 1:
The patent implements feedback by using an imaging device to detect the viewer's pupil locations and using this information to adjust the backlight's light emission angles. The system continuously monitors viewer position and dynamically adjusts the angular distribution of light from different backlight zones, ensuring that light is directed precisely at the pupil location, thereby maximizing light utilization efficiency while maintaining viewability.
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
Reduces overall luminous output of the backlight while maintaining viewer-perceived brightness, thereby decreasing power consumption and extending battery life in portable devices and reducing operating costs and environmental impact in stationary displays.
Implementation Method 1
a waveguide having a front face on the side facing the liquid-crystal layer, a back face opposite the liquid-crystal layer, and an edge face through which display light is received into the waveguide
Implementation Method 2
at least one volume hologram arranged on or within the waveguide... an injection optic is provided for directing light at a controllable angle into the waveguide to excitation of the at least one volume hologram
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A display includes an optical waveguide (44) with opposing front (46) and back faces (48), an injection optic (54), and volume hologram (52) arranged on or within the waveguide. The injection optic is configured to inject light into the waveguide at a variable injection angle (C), which influences the reflection angle at which the light (64) reflects from the front and back faces on propagating through the waveguide. The hologram is configured to release, in a predetermined direction, a portion of the light from the waveguide when excited at a predetermined reflection angle.