VR Eyepiece Optical Module With Polarization Folding and Low Ghosting
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Solution Overview
Problem
The Pancake optical architecture in VR eyepieces suffers from high light loss due to exponential attenuation during refraction and reflection, and ghost images are a significant issue, limiting its upgrade and development.
Innovation Solution
An optical module design featuring a cemented lens group with symmetrical plano-convex lenses, transflective films, quarter-wave plates, and polarizing reflective films, along with a refraction and reflection assembly, to enhance optical energy utilization and reduce system length while minimizing ghost images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If Pancake optical architecture is used to reduce system length, then the optical path is folded and system length is reduced, but light loss increases due to exponential attenuation in refraction and reflection processes
Solution Approach 1:
The patent applies preliminary action by pre-converting linearly polarized light into circularly polarized light using quarter-wave plates before the light enters the refraction and reflection process. This preliminary conversion ensures that when the light undergoes multiple reflections in the Pancake optical path, it maintains consistent polarization characteristics, preventing energy loss that would occur with repeated linear polarization-reflection cycles. The quarter-wave plates are positioned at specific locations (eye-side of cemented lens group and image-side of refraction-reflection assembly) to perform this preventive conversion in advance.
Solution Approach 2:
The patent changes the polarization state parameter of light from linear to circular through the use of quarter-wave plates. This parameter transformation allows the light to interact with the refraction and reflection surfaces in a manner that minimizes energy attenuation. By altering the fundamental polarization parameter, the system achieves multiple reflections necessary for optical path folding while maintaining higher light transmission efficiency compared to traditional linear polarization-based Pancake designs.
2Length of stationary object
If multiple refraction and reflection films are arranged in the lens assembly to fold the optical path, then the optical system length is reduced, but ghost images are generated due to multiple reflections
Solution Approach 1:
The patent changes the polarization state parameter of light from linear to circular through the use of quarter-wave plates. This parameter transformation allows the light to interact with the refraction and reflection surfaces in a manner that minimizes energy attenuation. By altering the fundamental polarization parameter, the system achieves multiple reflections necessary for optical path folding while maintaining higher light transmission efficiency compared to traditional linear polarization-based Pancake designs.
Solution Approach 2:
The patent converts the potentially harmful effect of multiple reflections (which cause ghost images) into a beneficial feature by using circularly polarized light. The multiple reflections that would normally create ghost images are transformed into useful optical path folding mechanisms when the light maintains circular polarization. The refraction and reflection films, which could generate ghost images with linearly polarized light, instead contribute to compact optical path design when working with circularly polarized light, as the polarization state prevents the formation of interfering reflection patterns.
3Loss of energy
If cemented lens group with symmetrical plano-convex lenses is used, then optical energy utilization is improved, but manufacturing complexity increases
Solution Approach 1:
The patent employs asymmetry in the arrangement and configuration of the cemented lens group. The symmetrical plano-convex lenses are arranged in an asymmetric configuration relative to the optical axis and other optical elements. This asymmetric arrangement optimizes the optical path for circularly polarized light, improving energy utilization by reducing unwanted reflections and refractions. The asymmetric design allows each lens surface to be optimized for specific functions, enhancing overall optical efficiency while managing manufacturing complexity through deliberate asymmetric configuration rather than requiring perfectly symmetric 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
The design increases optical energy utilization, reduces the optical system's length, and improves imaging performance, providing a lighter and more comfortable VR eyepiece system with enhanced field of view and reduced production complexity.
Implementation Method 1
the linearly polarized light is incident from the first polarizing reflective film and the first quarter-wave plate which are located on the image side, and is divided into two parts of light in the first transflective film
Implementation Method 2
one part of light is respectively reflected back at the first transflective film and the first polarizing reflective film which are located on the eye side
Implementation Method 3
a pair of first quarter-wave plates respectively arranged outside of the pair of plano-convex lenses
Implementation Method 4
a pair of first polarizing reflective films respectively arranged outside of the pair of first quarter-wave plates
Implementation Method 5
a cemented lens group, including a pair of plano-convex lenses which are symmetrically arranged and have mutually cemented flat surfaces
Data Source
AI summary
The disclosure provides an optical module and a VR eyepiece system. The optical module sequentially includes along an optical axis from an eye side to an image side: a cemented lens group, including a pair of plano-convex lenses, a first transflective film located between the pair of plano-convex lenses, a pair of first quarter-wave plates respectively arranged outside of the pair of plano-convex lenses, a pair of first polarizing reflective films respectively arranged outside of the pair of first quarter-wave plates; a refraction and reflection assembly, including a third lens, and a second quarter-wave plate and a second transflective film which are respectively arranged at an eye-side surface and an image-side surface of the third lens. In this way, light achieves multiple reflections within the cemented lens group, which is also able to increase an optical energy utilization of the cemented lens group while achieving folding of an optical path.