Dynamically Controllable Reflector for Light Guide Displays
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Solution Overview
Problem
Light guide displays with exit pupil expanders often suffer from uniformity issues due to multiple stages and paths of visible light, leading to attenuation of certain light paths, which affects color accuracy and balance, especially when trying to project a full RGB color gamut without increasing costs by using multiple light guides.
Innovation Solution
A dynamically controllable reflector is introduced to selectively recycle light, adjusting the ratio of intensities and color temperatures of light projected towards the user, using a tunable wavelength selective color filter and reflective surface to differentially reflect light, dependent on ambient illumination and sensor data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple light guides with narrow color gamut are used to provide fuller color gamut, then color accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies parameter changes by using a dynamically controllable reflector that can adjust its reflection characteristics in real-time. The reflector modifies the ratio of intensities of different colors (R, G, B) by changing its optical properties, allowing a single light guide to achieve full RGB color gamut without requiring multiple specialized light guides. This dynamic adjustment enables the system to optimize color accuracy while maintaining simpler device architecture.
Solution Approach 2:
The dynamically controllable reflector serves multiple functions: it recycles backward projected light, adjusts color ratios, and controls color temperature. By making the reflector multi-functional, the patent eliminates the need for separate components for each function, thereby reducing device complexity while maintaining high color accuracy and full color gamut projection capability.
2Ease of operation
If diffraction is used to project light in forward direction towards user, then image projection is improved, but backward direction light is also projected away from user
Solution Approach 1:
The patent converts the harmful backward projected light into a beneficial resource by using a dynamically controllable reflector to recycle this light back towards the user. The reflector captures the light that would otherwise be lost and redirects it through the light guide display system, effectively converting energy loss into useful image projection. This approach maintains the diffraction-based image projection capability while recovering the energy that would otherwise be wasted.
3Productivity
If multiple stages and paths of visible light are used in light guide display system, then light projection capability is improved, but uniformity issues arise where particular light paths are attenuated
Solution Approach 1:
The dynamically controllable reflector incorporates feedback mechanisms that monitor the light paths and adjust its reflection characteristics in real-time. By sensing the intensity ratios of different colors and dynamically modifying its optical properties, the reflector compensates for attenuation variations in different light paths. This feedback-driven adjustment ensures uniform color balance and intensity distribution across all light paths, resolving uniformity issues while maintaining high light projection capability.
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 optimizes color accuracy and balance by dynamically controlling light reflection, ensuring a uniform and enhanced user experience while potentially reducing the need for multiple light guides, thus lowering costs and improving efficiency in projecting a wide color gamut.
Implementation Method 1
They are attractive because they can have a large exit pupil and therefore do not require exact positioning of a viewing user. However, a light guide display such as an exit pupil expander is often optimized for use in a narrow band of wavelengths of light.
Implementation Method 2
a dynamically controllable reflector configured to provide selective reflection for light outcoupled from the exit pupil expander, wherein the selectivity of reflection of the light is dynamically controllable and wherein the selective reflection of the light is in a backwards direction back towards the user
Implementation Method 3
the dynamically controllable reflector comprises a reflective surface and a color filter. the color filter is a tunable wavelength selective color filter
Data Source
AI summary
An apparatus including: a display comprising an exit pupil expander including an outcoupling element configured to outcouple light in a forward direction towards a user and also in a backward direction away from the user; and a dynamically controllable reflector configured to provide selective reflection for light outcoupled from the exit pupil expander, wherein the selectivity of reflection of the light is dynamically controllable and wherein the selective reflection of the light is in a backwards direction back towards the user.