Polarization-Switched HMD Optics to Prevent Display Deterioration
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Solution Overview
Problem
Existing head mount displays (HMDs) suffer from issues such as display element deterioration due to strong light entering through openings, and previous solutions either increase the apparatus size or degrade image quality.
Innovation Solution
An optical system comprising a polarization selective half-transmissive reflective element, quarter waveplates, and a polarizer, which can switch between states to manage light guidance based on the HMD's usage state, preventing strong light from being condensed on the display element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the eyepiece lens is moved in the optical axis direction to prevent sunlight condensation, then display element deterioration is prevented, but the apparatus size increases in the optical axis direction
Solution Approach 1:
The patent changes the polarization state parameter of light to control its path. By switching the polarizer between orthogonal and parallel states relative to the PBS, the system redirects light without mechanical lens movement, thus preventing display element deterioration while maintaining compact size
Solution Approach 2:
The patent replaces the mechanical lens movement system with an optical control system using polarizers and a polarization beam splitter. This substitution eliminates the need for mechanical displacement while achieving the same protective function, thereby reducing apparatus size
2Object-affected harmful factors
If two polarizing filters are provided to attenuate incident light, then display element deterioration is prevented, but the apparatus size increases in the optical axis direction
Solution Approach 1:
The polarizer in the patent serves multiple functions: it controls the polarization state for normal operation and simultaneously acts as a light attenuation mechanism when in the orthogonal state. This multi-functionality eliminates the need for separate protective filters, reducing apparatus size
Solution Approach 2:
The patent merges the light control function and the protective attenuation function into a single polarizer element working in conjunction with the polarization beam splitter. This consolidation replaces the need for two separate polarizing filters, thereby reducing the apparatus size in the optical axis direction
3Object-affected harmful factors
If polarizing filters are provided to attenuate incident light, then display element deterioration is prevented, but image quality deteriorates
Solution Approach 1:
The patent dynamically switches the polarizer's orientation based on operational state. During normal use, the polarizer is in the parallel state that maintains image quality; during non-use, it switches to the orthogonal state for protection. This dynamic switching allows both high image quality and effective protection without permanent degradation
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 display element deterioration without increasing the HMD's size, ensuring optimal image quality and comfort during use.
Implementation Method 1
a polarization selective half-transmissive reflective element, a first quarter waveplate, an optical member including a half-transmissive reflective surface, a second quarter waveplate, and a polarizer, and is configured to guide light from the display element to the exit pupil
Implementation Method 2
a first quarter waveplate, an optical member including a half-transmissive reflective surface, a second quarter waveplate
Data Source
AI summary
An optical system includes, in order from a side of an exit pupil to a side of a display element, a polarization selective half-transmissive reflective element, a first quarter waveplate, an optical member including a half-transmissive reflective surface, a second quarter waveplate, and a polarizer, and is configured to guide light from the display element to the exit pupil. The optical system is changeable between a first state in which polarization directions of the polarization selective half-transmissive reflective element and the polarizer are orthogonal to each other, and a second state in which the polarization directions of the polarization selective half-transmissive reflective element and the polarizer coincide with each other.