Tandem Electrochromic Filter for AR Display Sunlight Readability
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Solution Overview
Problem
Current augmented reality (AR) display systems face challenges in achieving sunlight readability without high power consumption and display lifetime degradation, as existing electronically switchable optical windows either have fast switching speed with limited dynamic transmittance range or high dynamic range with slow switching speed.
Innovation Solution
A tandem electrochromic (EC) filter architecture is used, combining a gel-based EC window for high dynamic range with a Guest-Host Liquid Crystal (LC) window for fast switching speed, enabled by an augmented display transmittance system controller that determines and adjusts transmittance based on ambient light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If display brightness is increased to very high levels to overpower outside scene brightness, then sunlight readability is improved, but power consumption and heat dissipation increase undesirably
Solution Approach 1:
The patent introduces an electrochromic window as an intermediary component between the AR display and the external environment. This window dynamically modulates ambient light transmission, acting as a mediator that reduces the need for high display brightness while maintaining visibility. The EC window serves as a buffer that adapts to ambient lighting conditions, allowing the display to operate at lower power consumption levels.
Solution Approach 2:
The system dynamically changes the optical parameters of the EC window based on ambient light sensor input. By adjusting the transmittance parameter of the EC window in response to varying ambient conditions, the system maintains optimal display visibility without requiring constant high brightness output, thereby reducing overall power consumption.
2Illumination intensity
If display brightness is increased to very high levels to overpower outside scene brightness, then sunlight readability is improved, but display lifetime degradation occurs
Solution Approach 1:
The EC window serves as a protective intermediary that filters and modulates ambient light before it reaches the display. By controlling the amount of ambient light that interacts with the display system, the window reduces stress on display components, thereby extending display lifetime while maintaining readability in bright conditions.
3Speed
If fast switching optical windows are used (e.g., GH-LC, guest-host liquid crystal), then switching speed is improved, but dynamic transmittance range is limited
Solution Approach 1:
The patent segments the optical control function into two distinct components: a fast-switching GH-LC window for rapid response and an electrochromic window for broad transmittance range. Each component is optimized for its specific function, and their combination achieves both fast switching and wide dynamic range control.
Solution Approach 2:
The system merges two different optical window technologies (GH-LC and EC) into a single integrated solution. The GH-LC window provides fast switching capability while the EC window contributes broad dynamic transmittance range, creating a hybrid system that leverages the strengths of both technologies.
4Adaptability or versatility
If gel-based electrochromic windows are used, then dynamic transmittance range is improved (>100:1), but switching speed becomes very slow (10s of seconds)
Solution Approach 1:
The patent divides the optical control task between two specialized components: the EC window handles the broad transmittance range adjustment while the GH-LC window provides fast switching. This segmentation allows each component to be optimized for its specific strength without compromise.
Solution Approach 2:
The system uses partial action by having the EC window operate only when broad transmittance adjustment is needed, while the fast GH-LC window handles routine switching. This distributes the workload appropriately, allowing the slow EC window to provide its high dynamic range capability without being the bottleneck for all switching operations.
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 configuration allows for wide dynamic range control and fast switching speed, enabling AR display systems to operate effectively in various lighting conditions, including direct sunlight, with improved power efficiency and reduced heat dissipation and lifetime degradation issues.
Implementation Method 1
a first window (EC-C) optimized for faster clearing and a second window (EC-D) optimized for faster darkening
Implementation Method 2
a second window (EC-D) optimized for faster darkening
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
An augmented display system with dynamic see-through transmittance control is disclosed. The augmented display system includes: an augmented display screen; a tandem electrochromic (EC) filter disposed over the augmented display screen. The tandem EC filter includes a first window having a dominant first transmittance characteristic and a second window having a dominant second transmittance characteristic; and an augmented display transmittance controller configured to individually control the activation of the first window and the second window of the tandem EC filter, wherein the augmented display transmittance controller is configured to: determine from an ambient light sensor output the transmittance required from the first window and the second window for a selected augmented display luminance; and apply appropriate drive voltage waveforms to the first window and the second window to achieve the determined transmittance.