Variable Focal Backlighting Using Birefringent Wedges
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Solution Overview
Problem
Conventional backlighting systems in display devices waste significant power by emitting light that does not reach the viewer's pupils, leading to inefficient power consumption and heat generation, especially in battery-powered devices.
Innovation Solution
A variable focal backlighting system using a waveguide assembly with birefringent and isotropic wedges and a liquid crystal layer to dynamically adjust the convergence and directionality of light, ensuring illumination is focused at the viewer's pupils, reducing unnecessary light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional backlighting systems emit light in all directions, then the display is uniformly illuminated, but significant power is wasted by emitting light that does not reach the viewer's pupils
Solution Approach 1:
The patent applies local quality by making different regions of the backlight system have different optical properties. The waveguide assembly contains birefringent and isotropic wedge regions that selectively manipulate light propagation. These localized regions with different refractive indices create directionality in the backlight, concentrating light toward the viewer's pupils rather than emitting uniformly in all directions, thus reducing wasted energy while maintaining display illumination.
Solution Approach 2:
The patent implements dynamics by making the backlight system adaptable to changing viewing conditions. The liquid crystal layer can dynamically adjust its optical properties in response to detected pupil positions, and the waveguide assembly can vary the convergence angle of light based on viewer distance and angle. This dynamic adjustment ensures light is always directed toward the actual pupil location, maximizing energy efficiency across different viewing scenarios.
2Temperature
If backlighting emits light in all directions, then the display remains visible from various angles, but heat is generated from unnecessary light emission
Solution Approach 1:
The waveguide assembly introduces local quality variations through birefringent and isotropic wedge regions that selectively control light propagation directions. These localized optical structures redirect light preferentially toward the viewer's pupils while maintaining sufficient angular distribution for comfortable viewing. This approach reduces heat-generating omnidirectional emission while preserving essential viewing angle flexibility.
Solution Approach 2:
The system dynamically adjusts light directionality based on detected pupil positions and viewing conditions. The liquid crystal layer and waveguide assembly work together to modify the angular distribution of backlight in real-time, concentrating light toward the actual viewing direction while maintaining adaptability to different viewing angles. This dynamic control reduces heat generation from light emitted in irrelevant directions while preserving viewing flexibility.
3Loss of energy
If a variable focal backlighting system uses waveguide assembly with birefringent and isotropic wedges and liquid crystal layer to dynamically adjust light convergence, then light is focused precisely on the viewer's pupils, but the device complexity increases
Solution Approach 1:
The patent merges multiple optical functions into a single integrated waveguide assembly. The birefringent wedge, isotropic wedge, and liquid crystal layer are combined in one structure that simultaneously performs light redirection, convergence control, and directional filtering. This consolidation achieves precise pupil-focused illumination while avoiding the need for separate optical components, thereby reducing overall device complexity despite the advanced functionality.
Solution Approach 2:
The waveguide assembly serves multiple functions within a single component: it redirects light from the LED source, controls the convergence angle of backlight, filters light directionality through birefringent and isotropic regions, and adapts to different viewing conditions. This multi-functionality eliminates the need for separate optical elements, achieving efficient pupil-focused lighting without proportionally increasing device complexity.
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 significantly reduces power consumption by focusing light only on the viewer's pupils, enhancing display visibility in bright conditions and extending battery life in portable devices, while also reducing heat generation.
Implementation Method 1
A variable focal backlighting system using a waveguide assembly with birefringent and isotropic wedges and a liquid crystal layer to dynamically adjust the convergence and directionality of light
Implementation Method 2
The other wedge may be an isotropic wedge or other wedge that propagates light at a different speed than the birefringent wedge for at least one polarization state
Implementation Method 3
A liquid crystal layer is disposed adjacent the waveguide assembly to selectively switch the polarization state of the light reflectively propagating down the waveguide assembly
Implementation Method 4
The backlight unit includes a waveguide assembly including a first wedge and a birefringent wedge disposed adjacent to, and arranged nose-to-tail with, the first wedge, to define an interface of the waveguide assembly
Data Source
AI summary
A backlight unit includes a waveguide assembly having a first wedge and a birefringent wedge disposed adjacent to, and arranged nose-to-tail with, the first wedge, to define an interface of the waveguide assembly. The birefringent wedge has different indices of refraction for light propagating through the waveguide assembly in first and second polarization states. The first wedge is configured to propagate the light in the second polarization state at a different speed than the birefringent wedge. A liquid crystal layer is configured to selectively switch the light between the first and second polarization states.