Switchable Grating Optical Attenuator for HMD Brightness Control
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Solution Overview
Problem
Existing display devices, particularly head-mounted displays, face challenges in adjusting brightness in low-light environments, as traditional methods for dimming lasers are either unstable or result in bulky, power-hungry mechanical devices with unsuitable insertion losses.
Innovation Solution
The use of a switchable grating-based optical attenuator that diffracts a tunable proportion of light towards an optical dump, allowing for compact, power-efficient, and fast adjustment of brightness by applying a voltage across the grating, achieving a dynamic range of 1% to 99% attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional mechanical devices are used to dim lasers, then brightness adjustment is achieved, but the device becomes bulky and power-hungry
Solution Approach 1:
The patent replaces mechanical dimming devices with an optical attenuator comprising a diffraction grating and control electrodes. The electrodes apply voltages to tune the diffraction efficiency of the grating, thereby controlling the proportion of light directed to the optical dump versus the output. This electrical control mechanism eliminates bulky mechanical components while achieving the same brightness adjustment function.
2Illumination intensity
If traditional mechanical devices are used to dim lasers, then brightness adjustment is achieved, but insertion losses increase
Solution Approach 1:
The optical attenuator uses a diffraction grating that can be electrically tuned to diffract specific proportions of incident light. By controlling the diffraction efficiency through applied voltages, the system directs varying amounts of light to the optical dump while maintaining high transmission efficiency for the desired output, thereby minimizing insertion losses compared to mechanical absorption-based dimmers.
3Illumination intensity
If laser brightness is reduced in low-light environments, then comfort is improved, but display visibility decreases
Solution Approach 1:
The patent enables continuous tuning of the diffraction efficiency parameter of the grating by varying the control voltages. This allows precise control over the proportion of light attenuated, enabling the display to adapt its brightness to different ambient lighting conditions while maintaining optimal visibility and user comfort across varying 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
This solution provides high repeatability, fast response times, and avoids insertion losses, enabling precise control of display brightness in various lighting conditions, from full brightness to minimal levels, while maintaining compactness and efficiency.
Implementation Method 1
a switchable grating configured to diffract light within a wavelength band at a diffraction angle
Implementation Method 2
an electrode pair configured to apply a voltage across the switchable grating to tune a proportion of incident light diffracted
Data Source
AI summary
Examples are disclosed relating to tunable attenuation of incident light using a switchable grating. One example provides an optical attenuator comprising a switchable grating configured to diffract light within a wavelength band at a diffraction angle. The optical attenuator further comprises an electrode pair configured to apply a voltage across the switchable grating to tune a proportion of incident light diffracted at the diffraction angle, and an optical dump to receive the proportion of incident light diffracted.