Head-Mounted Display Polarization Control for Privacy
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Solution Overview
Problem
Head-mounted displays using diffraction elements face issues with image resolution due to peripheral wavelengths, and existing solutions like half mirrors can inadvertently transmit imaging light, making the viewed image visible to third parties.
Innovation Solution
Incorporating a polarization conversion member, such as a wave plate or polarization film, to convert the polarization state of imaging light before it reaches a half mirror, which is positioned to reflect the imaging light while absorbing unwanted polarizations, thereby reducing the visibility of the image to outsiders while maintaining see-through properties for external light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a half mirror is used to guide imaging light, then the external scene viewing range is increased, but the imaging light may be transmitted without being reflected, making it visible to third parties
Solution Approach 1:
The patent changes the polarization parameter of the imaging light by introducing a polarization conversion member (wave plate or polarization film) that converts the polarization state. This parameter change enables the half mirror to selectively reflect the converted polarization while maintaining transmission of external light, thus preventing imaging light from reaching third parties while preserving the wide viewing angle capability.
Solution Approach 2:
The patent introduces a polarization conversion member as an intermediary component between the imaging light generating device and the half mirror. This intermediary converts the polarization state of imaging light, enabling the half mirror to distinguish between imaging light (which should be reflected) and external light (which should be transmitted), thereby solving the security issue while maintaining viewing range.
2Object-affected harmful factors
If a polarization conversion member is added to convert polarization state, then imaging light transmission to third parties is reduced, but device complexity increases
Solution Approach 1:
The patent utilizes polarization state conversion, a well-understood optical parameter transformation, to achieve secure imaging light reflection. By changing the polarization parameter through a simple wave plate or polarization film, the system prevents imaging light leakage without requiring complex active control mechanisms or multiple sophisticated optical components.
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 enhances image resolution by minimizing the transmission of imaging light through the half mirror, making it difficult for third parties to view the displayed information while ensuring a wide field of view for external light, thus improving security and visibility.
Implementation Method 1
a polarization conversion member provided on an optical path of the imaging light between the imaging light generating device and the half mirror, and configured to convert a polarization state of the imaging light to the second polarization
Implementation Method 2
with respect to the light of the predetermined polarization state, reflectance of a first polarization by the half mirror is lower than reflectance of a second polarization by the half mirror
Implementation Method 3
a polarization absorbing film provided on an opposite side of the half mirror from a reflection surface thereof, and configured to absorb the first polarization
Data Source
AI summary
A head-mounted display according to the present disclosure includes an imaging light generating device that emits imaging light, and a half mirror that reflects the imaging light and transmits external light. The imaging light is incident on the half mirror as light of a predetermined polarization state, and, with respect to the light of the predetermined polarization state, reflectance of a first polarization by the half mirror is lower than reflectance of a second polarization by the half mirror.