Pancake Lens Ghost Effect Reduction via PVH IR Reflection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Head-Mounted Displays (HMDs) with pancake lenses face challenges in achieving compact size and high optical quality while minimizing ghost effects and maintaining infrared light reflection capabilities for eye tracking and image focusing.
Innovation Solution
Incorporating a polarization volume hologram (PVH) layer configured to reflect infrared light, along with an IR absorbing structure or additional PVH layer, to address the ghost effect and enhance optical performance in HMDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a pancake lens is used to achieve compact size and light weight, then the HMD form factor is improved, but ghost effects increase due to multiple reflectors and partial reflectors
Solution Approach 1:
The patent extracts and removes the harmful ghost reflections from the optical system by introducing an IR absorbing structure that selectively absorbs infrared light before it can create ghost effects, while preserving the compact pancake lens design
Solution Approach 2:
The patent introduces an intermediary IR absorbing structure (including quarter-wave plate and linear absorptive polarizer) between the pancake lens and PVH layer to mediate the interaction between infrared light and the optical system, preventing ghost effects while maintaining eye tracking functionality
2Reliability
If a PVH layer is added to reflect IR light for eye tracking, then eye tracking capability is improved, but the optical system complexity increases
Solution Approach 1:
The patent merges the IR reflection function into the existing optical system by integrating a PVH layer with the pancake lens assembly, allowing the same optical structure to serve both imaging and eye tracking functions simultaneously
Solution Approach 2:
The patent makes the optical system multi-functional by enabling the PVH layer to reflect IR light for eye tracking while the same optical path handles visible light imaging, allowing one system to perform multiple functions without proportionally increasing complexity
3Manufacturing precision
If multiple optical elements are used in the lens system for focusing, then image quality is improved, but the number of components increases leading to larger size
Solution Approach 1:
The patent nests the PVH layer and IR absorbing structure within the existing pancake lens assembly, embedding additional functional layers within the compact lens structure rather than adding separate external 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 solution effectively reduces or eliminates ghost effects and improves the optical system's compactness and field of view by utilizing PVH layers to reflect IR light, enabling efficient eye tracking and image focusing while maintaining image clarity.
Implementation Method 1
The PVH layer being configured to reflect infrared (IR) light
Implementation Method 2
The IR absorbing structure includes a quarter-wave plate (QWP) arranged between the optical lens and the PVH layer
Implementation Method 3
The linear absorptive polarizer is configured to absorb IR light
Data Source
AI summary
An optical system includes an optical lens, a polarization volume hologram (PVH) layer arranged over the optical lens, and an IR absorbing structure arranged between the optical lens and the PVH layer. The PVH layer being configured to reflect infrared (IR) light. The IR absorbing structure includes a quarter-wave plate (QWP) arranged between the optical lens and the PVH layer and a linear absorptive polarizer arranged between the QWP and the optical lens. The linear absorptive polarizer is configured to absorb IR light.