Optical System Retardance Matching to Eliminate Ghost Images
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical systems for VR head-mounted displays suffer from ghost images and reduced brightness due to incomplete conversion of light wavelengths by quarter wavelength plates, leading to deviations in polarization function and decreased brightness.
Innovation Solution
The optical system employs lamination type wavelength plates with equal retardance and a reflective polarizer with cholesteric liquid crystal layers, ensuring complete conversion of light wavelengths and minimizing ghost images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional quarter wavelength plates are used in the optical system, then the structure can be simplified, but ghost images are caused and brightness is reduced due to incomplete light conversion
Solution Approach 1:
The patent applies parameter changes by precisely controlling the retardance values of the quarter wavelength plates. Specifically, it sets the retardance of the first quarter wavelength plate to be equal to or greater than that of the second quarter wavelength plate, and controls the retardance difference to be within a specific range (0.01λ-0.1λ at 550nm). This parameter optimization ensures complete light conversion while eliminating ghost images, resolving the contradiction between structural simplicity and image quality.
2Ease of manufacture
If conventional quarter wavelength plates are used, then manufacturing is easier, but polarization function deviates and ghost images occur
Solution Approach 1:
The patent uses parameter changes by establishing specific retardance relationships between the first and second quarter wavelength plates. By controlling the retardance difference within a precise range and ensuring the first quarter wavelength plate has equal or greater retardance than the second, the system achieves reliable polarization function conversion while maintaining ease of manufacture through standardized manufacturing processes.
3Ease of manufacture
If quarter wavelength plates with different retardance are used, then manufacturing flexibility is improved, but light reciprocation fails and main images become dark
Solution Approach 1:
The patent applies parameter changes by defining specific retardance constraints: the first quarter wavelength plate must have retardance equal to or greater than the second quarter wavelength plate, and the difference must be within 0.01λ-0.1λ at 550nm. These parameter specifications ensure proper light reciprocation between the half mirror and reflective polarizer, preventing main images from becoming dark while allowing manufacturing flexibility within the defined ranges.
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 brightness and eliminates ghost images, providing improved image quality in VR head-mounted displays.
Implementation Method 1
retardance of the first quarter wavelength plate and retardance of the second quarter wavelength plate are equal to each other
Implementation Method 2
light is completely converted into circularly polarized light in the quarter wavelength plate through which the light first passes, and is completely converted into linearly polarized light in the quarter wavelength plate through which the light second passes
Implementation Method 3
the light can be completely reflected to the image display device side by the reflective polarizer
Implementation Method 4
a reflective polarizer with cholesteric liquid crystal layers
Implementation Method 5
each of the first quarter wavelength plate and the second quarter wavelength plate is a lamination type wavelength plate consisting of a plurality of optically anisotropic layers
Data Source
AI summary
An object is to provide an optical system capable of improving the brightness of a main image while eliminating a ghost image. In an optical system including: an image display device that emits an image; a linear polarizer through which light associated with the image passes; a first quarter wavelength plate which receives the light from the linear polarizer; a half mirror; a reflective polarizer; and a second quarter wavelength plate provided between the reflective polarizer and the half mirror, retardance of the first quarter wavelength plate and retardance of the second quarter wavelength plate are equal, and thus the object is achieved.