Composite Variable Light Attenuator for HMD Brightness Control
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Solution Overview
Problem
Head-mounted display systems face challenges in maintaining consistent brightness of virtual and real-world objects due to varying ambient light conditions, which can lead to an immersive experience being lessened and power constraints.
Innovation Solution
An optical stack with two or more variable optical elements under synchronous control, allowing for rapid and continuous adjustment of light transmission based on ambient light levels, combining elements with wide and narrow ranges of transmission to maintain consistent perceived brightness across varying environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single variable optical element is used to control light transmission, then the device complexity is reduced, but the light transmission control range and precision are insufficient to maintain consistent brightness across varying ambient light conditions
Solution Approach 1:
The optical system is divided into multiple variable optical elements (first variable optical element and second variable optical element) that operate in series. Each element handles a different portion of the light transmission control range, with the first element providing coarse adjustment and the second element providing fine adjustment, thereby achieving wide-range precise control without requiring a single complex element
Solution Approach 2:
The patent implements dynamic control of multiple variable optical elements through synchronous operation. The controller dynamically adjusts the transmission characteristics of each element based on ambient light conditions, enabling the system to adapt to varying lighting environments while maintaining consistent perceived brightness through coordinated dynamic adjustment
2Stability of the object's composition
If light transmission is attenuated to maintain consistent brightness in high ambient light conditions, then the perceived brightness stability is improved, but the power consumption increases
Solution Approach 1:
Instead of using a single optical element at maximum attenuation, the patent distributes the attenuation requirement across multiple variable optical elements. Each element operates at a moderate transmission level rather than one element operating at extreme attenuation, reducing the power consumption while achieving the same overall light transmission control and brightness stability
Solution Approach 2:
The system dynamically changes the transmission parameters of multiple variable optical elements based on ambient light conditions. By adjusting the transmission characteristics of each element proportionally and synchronously, the system achieves efficient power consumption while maintaining consistent perceived brightness across different lighting environments
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
The solution enables consistent control of light transmission, ensuring that virtual and real-world objects appear with stable brightness regardless of ambient light conditions, enhancing user experience and reducing power consumption.
Implementation Method 1
EP2562588A1 describes a non-see-through display comprising pixels configured to display a color image in which each pixel acts as a tunable photonic crystal filter that reflects wavelengths of light of a selected colour into the eye of the user
Implementation Method 2
US2012/0068913 describes a head-mounted display device that selectively blocks portions of a real world scene so that augmented reality image appears more distinctly
Data Source
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AI summary
An optical stack includes a first variable element and a second variable element. The first variable element is configured to vary light transmission through the first variable element as a function of a first control signal. The second variable element is in series with the first variable element and is configured to vary light transmission through the second variable element as a function of a second control signal. A controller dynamically supplies the first control signal to the first variable element and supplies the second control signal to the second variable element.