Eyepiece Polarization Plates for HMD Ghost Reduction
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Solution Overview
Problem
Existing head mount display (HMD) systems suffer from external light ghosts, which obstruct the observer's ability to visually recognize their surroundings due to refraction and reflection of external light in the eyepiece optical system, despite attempts to prevent these effects.
Innovation Solution
The implementation of an eyepiece optical system comprising a first linear polarization plate closest to the observer and a second linear polarization plate outside the optical path, with differing transmission axis directions, to guide light from the image display element to the observer while shielding external light using a light shielding unit with a second linear polarization plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light shielding member is used to prevent external light intrusion, then external light ghost is prevented, but the observer cannot directly visually recognize the surroundings
Solution Approach 1:
The light shielding function is segmented into two parts: the light shielding member that blocks external light from entering the optical system, and the second linear polarization plate that selectively blocks polarized external light while allowing non-polarized or differently polarized light to pass through to the observer's eye. This segmentation resolves the contradiction by distributing the light control function across multiple components with different characteristics.
Solution Approach 2:
Different regions of the optical system are assigned different optical properties. The first linear polarization plate is positioned at a specific location with its transmission axis perpendicular to the PBS reflection direction, creating a localized polarization filtering effect that prevents external light ghost while maintaining transparency for the observer in other regions.
2Object-affected harmful factors
If the transmission axis direction of the first linear polarization plate is perpendicular to the transmission axis direction of the second linear polarization plate, then external light ghost is effectively prevented, but the light shielding effectiveness may be reduced
Solution Approach 1:
The first linear polarization plate acts as an intermediary element between the PBS and the observer's eye. By positioning it with its transmission axis perpendicular to the PBS reflection direction, it selectively filters external light that would otherwise cause ghost images, while allowing the desired image light to pass through to the observer.
Solution Approach 2:
The polarization state of light is changed as it passes through the first linear polarization plate. The plate transforms the polarization parameters of incoming light, allowing only light with specific polarization characteristics to pass through, thereby preventing external light ghost while maintaining image quality.
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 the observer to visually recognize their surroundings while effectively preventing external light ghosts, maintaining image light intensity and reducing external light intrusion to about 10% or less, enhancing safety during video experiences.
Implementation Method 1
an eyepiece optical system including a first linear polarization plate and configured to guide light from an image display element to an eye of an observer
Implementation Method 2
a second linear polarization plate disposed outside an optical path from the image display element to the eye of the observer... Transmission axis direction of the first linear polarization plate and a transmission axis direction of the second linear polarization plate are different from each other
Implementation Method 3
External light incident from a gap between the image display apparatus and the eye(s) of the observer may cause refraction and reflection in the eyepiece optical system
Implementation Method 4
External light incident from a gap between the image display apparatus and the eye(s) of the observer may cause refraction and reflection in the eyepiece optical system
Data Source
AI summary
An optical apparatus includes an eyepiece optical system including a first linear polarization plate and configured to guide light from an image display element to an eye of an observer, and a second linear polarization plate disposed outside an optical path from the image display element to the eye of the observer. The first linear polarization plate is disposed closest to the observer in the eyepiece optical system. A transmission axis direction of the first linear polarization plate and a transmission axis direction of the second linear polarization plate are different from each other.