AR Optical Layout Using Polarization to Block Projector Visibility
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Solution Overview
Problem
Conventional head-mounted augmented reality (AR) apparatuses suffer from issues such as direct visibility of the image projection source, light emission affecting image quality and user comfort, and privacy concerns due to light exiting the apparatus, which impacts interaction and image quality when additional lenses are used.
Innovation Solution
An optical system incorporating a polarizing beam splitter and polarizer to control light polarization, combined with wave plates and semi-reflectors, ensures that light emitted from the image projection source is managed to prevent direct visibility and exit from the apparatus, enhancing user comfort, privacy, and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional head-mounted AR apparatus is designed, then the structure is simple, but the user can directly see the image projection source and light emitted from it, affecting image quality and user comfort
Solution Approach 1:
A polarizing beam splitter is introduced as an intermediary optical element between the image projection source and the user's eye. This beam splitter separates light based on polarization direction, allowing the system to control which light reaches the user while blocking direct visibility of the projection source. The intermediary element enables selective light transmission without requiring complex mechanical shutters or additional shielding structures.
Solution Approach 2:
The system changes the polarization parameter of light emitted from the image projection source by incorporating a polarizer. This parameter change allows the polarizing beam splitter to differentiate between desired image light and unwanted direct light from the projection source, resolving the contradiction by modifying light properties rather than complicating the physical structure.
2Volume of moving object
If a conventional head-mounted AR apparatus is designed, then the device is compact, but light exits from the semi-reflector side, affecting privacy and interaction
Solution Approach 1:
The polarizing beam splitter acts as a mediator that prevents light from exiting the apparatus unwantedly. By positioning the beam splitter and polarizer in the optical path, the system ensures that only properly polarized light transmitted through the semi-reflector reaches the user, while blocking any light that would otherwise exit and compromise privacy or interfere with interactions.
Solution Approach 2:
The system utilizes polarization parameter changes to control light direction and prevent unwanted light exit. The polarizer and beam splitter work together to ensure light follows the intended optical path, maintaining compact device geometry while eliminating privacy issues through optical parameter control rather than physical containment.
3Manufacturing precision
If additional lenses are arranged outside the augmented reality apparatus, then image quality can be adjusted, but light emitted from the image projection source is reflected at the lens, affecting final image quality
Solution Approach 1:
The polarizer and polarizing beam splitter are positioned upstream in the optical path, performing preliminary polarization filtering before light reaches any additional external lenses. This preliminary action ensures that only the desired polarized light component reaches the external lens, preventing unwanted reflections and maintaining image quality without requiring modifications to the external lens itself.
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
The solution effectively reduces the visibility of the image projection source and light exit, improving user comfort, privacy, and interaction while enhancing image quality and reducing power consumption.
Implementation Method 1
a polarizing beam splitter having a beam splitting side adjacent to the image projection source and a transmission side facing away from the image projection source, the polarizing beam splitter being arranged such that light emitted from the image projection source is able to be non-perpendicularly incident on and be at least partially reflected by the beam splitting side, and the polarizing beam splitter being configured such that when light is incident on the beam splitting side, a polarized light component, whose polarization is in a first direction, passes through the polarizing beam splitter and is transmitted through the transmission side thereof, and a polarized light component, whose polarization is in a second direction perpendicular to the first direction, is reflected from the beam splitting side
Implementation Method 2
the optical system also comprises a polarizer disposed between the image projection source and the beam splitting side of the polarizing beam splitter, and the polarizer is configured to allow polarized light, whose polarization is in the second direction, to be transmitted therethrough and polarized light, whose polarization is in the first direction to be absorbed
Implementation Method 3
a wave plate adjacent to the beam splitting side, the light emitted from the image projection source being able to be at least partially reflected by the beam splitting side towards the wave plate
Implementation Method 4
a semi-reflector located downstream of the wave plate in an optical path of reflected light
Data Source
AI summary
The disclosure relates to an optical system for an augmented reality apparatus, comprising: an image projection source; and a polarizing beam splitter. The polarizing beam splitter is arranged such that light emitted from the image projection source is able to be non-perpendicularly incident on the beam splitting side and be at least partially reflected. The polarizing beam splitter is configured such that a polarized light component passes through the polarizing beam splitter and is transmitted through the transmission side thereof, and a polarized light component is reflected from the beam splitting side. The optical system also comprises a polarizer disposed between the image projection source and the polarizing beam splitter, and the polarizer is configured to allow polarized light, whose polarization is in the second direction, to be transmitted therethrough and polarized light, whose polarization is in the first direction to be absorbed.