Head-Mounted Display Light Reducing Unit for Brightness Uniformity
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Solution Overview
Problem
Existing head-mounted displays suffer from uneven brightness between outside light from the front and diagonally lower angles, causing visual discrepancies that affect the user's ability to see a natural outside view.
Innovation Solution
Incorporating a combiner and a light reducing unit with specific transmittance properties to balance the brightness of outside light from different angles, ensuring equal transmittance for outside light from the front and diagonally lower positions, thereby reducing visual discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a half-mirror and polarizing beam splitter are used to combine display light with outside light from the front, then the display image can be superimposed on the front view, but outside light from the diagonally lower front enters the user's eyes without passing through the half-mirror, causing brightness difference between front and lower front views
Solution Approach 1:
The optical path is segmented into multiple independent channels: a front view channel through the half-mirror and polarizing beam splitter, and a lower front view channel through the light reducing unit. This allows different optical paths to handle different viewing angles separately, resolving the brightness inconsistency issue while maintaining the complex optical structure necessary for AR display functionality
Solution Approach 2:
A light reducing unit is introduced as an intermediary component in the lower front view optical path. This unit acts as a mediator that attenuates outside light from the diagonally lower front to match the brightness level of front view light, enabling consistent brightness across different viewing angles without requiring a complete redesign of the optical system
2Manufacturing precision
If the half-mirror attenuates outside light from the front, then the display image can be properly superimposed, but outside light from the diagonally lower front is not attenuated, causing brightness difference
Solution Approach 1:
Different optical components are assigned to different spatial regions: the half-mirror and polarizing beam splitter handle front view light, while the light reducing unit specifically handles lower front view light. Each component is optimized for its specific function, with the light reducing unit providing localized attenuation only where needed to achieve uniform brightness across the field of view
Solution Approach 2:
The transmittance parameter of the light reducing unit is specifically optimized to match the attenuation level of the half-mirror. By adjusting the transmittance value of the light reducing unit, the system achieves brightness uniformity between front and lower front views, transforming an optical design problem into a parameter optimization problem
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 allows users to see the outside view properly by equalizing brightness across different viewing angles, enhancing visibility and reducing the sense of visual discomfort.
Implementation Method 1
a polarizing beam splitter, a concave half-mirror, a 1/4 wave plate, and a polarizing diffractive element. The polarizing beam splitter reflects s-polarized light and transmits p-polarized light
Implementation Method 2
a light reducing unit configured to transmit a part of outside light from below the combiner and have transmittance equal to or lower than transmittance of the combiner
Data Source
AI summary
Provided is a head-mounted display that allows a user to see an outside view properly. The head-mounted display includes a combiner configured to combine display light for forming a display image with outside light from in front of a user wearing a head-mounted display, and a light reducing unit configured to transmit a part of outside light from below the combiner and have transmittance equal to or lower than transmittance of the combiner.