Adaptive Brightness Control for Head Mounted Displays
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) are limited by cost, size, weight, field of view, and efficiency due to their optical systems, which restrict their practical and leisure applications, particularly in augmented reality where dynamic brightness control and contrast are essential for user comfort and effective overlay of computer-generated imagery (CGI) over real-world views.
Innovation Solution
The implementation of an adaptive brightness control system in HMDs, utilizing an ambient light sensor, a variable transparency layer, and a controller to adjust display brightness and eyepiece transparency in real-time, based on ambient light conditions, to achieve optimal contrast and user comfort, incorporating a functional block diagram and flow charts detailing the process for dynamic adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional optical systems are used in HMDs, then the basic display function is achieved, but the field of view, efficiency, and user comfort are limited due to fixed brightness and contrast
Solution Approach 1:
The patent implements dynamic brightness control by making the eyepiece transparency variable rather than fixed. The eyepiece transparency is adjusted in real-time based on ambient light conditions detected by sensors, allowing the system to adapt to different lighting environments (indoor, outdoor, twilight) and maintain optimal contrast between CGI and real-world views.
Solution Approach 2:
The patent changes the transparency parameter of the eyepiece as a variable control mechanism. By adjusting the transparency parameter of the eyepiece in response to ambient light level changes, the system optimizes the contrast between the computer-generated image and the real-world view, thereby improving adaptability without fundamentally redesigning the optical system.
2Ease of operation
If fixed brightness display is used in HMDs, then device simplicity is maintained, but user comfort and display effectiveness vary poorly across different lighting conditions
Solution Approach 1:
The patent implements a feedback control system where ambient light sensors continuously monitor the lighting conditions and provide this information to a controller. The controller then adjusts the eyepiece transparency and/or CGI brightness accordingly, creating a closed-loop system that automatically maintains optimal display characteristics across varying environmental conditions without user intervention.
Solution Approach 2:
The HMD system performs self-adjustment of display parameters based on environmental conditions. The ambient light sensors and controller work together to automatically optimize the eyepiece transparency and CGI brightness, allowing the device to serve itself in adapting to different lighting environments (indoor, outdoor, twilight) without requiring manual user adjustment.
3Illumination intensity
If high brightness CGI is displayed to ensure visibility, then image visibility is improved, but contrast with real-world view deteriorates in bright ambient light conditions
Solution Approach 1:
The patent applies different brightness and transparency characteristics to different parts of the optical path. The eyepiece transparency is adjusted locally to control the amount of real-world light reaching the user's eye, while the CGI brightness is independently controlled. This allows optimization of both the CGI visibility and the contrast with the real-world view by treating these two light paths differently rather than uniformly.
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 enhances user comfort and display options by dynamically adjusting brightness and transparency, improving the dynamic range and efficiency of HMDs, thereby expanding their application potential in augmented reality and other fields.
Implementation Method 1
a variable transparency layer to control the amount of ambient light blocked by the eyepiece
Implementation Method 2
an ambient light sensor to determine the brightness of an ambient environment
Data Source
AI summary
A technique for adaptive brightness control of an eyepiece of a head mounted display (“HMD”) includes displaying a computer generated image (“CGI”) to an eye of a user from a viewing region of the eyepiece of the HMD. Image data is captured from an ambient environment surrounding the HMD. A brightness value is calculated for the ambient environment based at least in part upon the image data. A bias power setting is determined based at least in part upon the brightness value. The bias power setting is applied to an illumination source for generating the CGI and a brightness level of the CGI displayed to the eye of the user is controlled with the bias power setting.