Optical Structure with Dual Phase Retardation for VR Ghosting
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Solution Overview
Problem
Existing VR display devices with folded optical paths suffer from ghosting and stray light due to unsatisfactory conversion of polarization states caused by material dispersion effects and beam splitting properties, leading to reduced imaging quality.
Innovation Solution
An optical structure comprising a transflective film, a reflective polarizing layer, and a first phase retardation film group with specific phase retardations and included angles between the slow axes of the phase retardation films and the reflection axis of the reflective polarizing layer, enhancing the conversion efficiency between circularly and linearly polarized light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a folded optical path design is used to achieve short-focus optical design, then the total optical length is compressed and the device becomes suitable for lightweight head-mounted display, but ghosting and stray light occur due to unsatisfactory polarization state conversion
Solution Approach 1:
The phase retardation film is divided into multiple layers with different phase retardation values (first phase retardation film with 200-280nm, second phase retardation film with 80-170nm). This segmentation allows each layer to contribute differently to the overall polarization conversion, achieving better color compensation and reducing ghosting effects while maintaining the compact folded optical path design.
Solution Approach 2:
The patent optimizes specific parameters including the phase retardation values of each film layer, the included angles between slow axes and reflection axis (first film: 90-180 degrees, second film: 135-315 degrees), and the thickness of each layer. These parameter changes enable effective polarization state conversion across different wavelengths, reducing chromatic dispersion and eliminating ghosting while preserving the compact optical path length.
2Device complexity
If material dispersion effects and beam splitting properties are present in the folded optical path, then the optical path can be folded back between lens, phase compensation film, and reflective polarizer, but the polarization state conversion becomes unsatisfactory leading to reduced imaging quality
Solution Approach 1:
The patent uses a composite structure of multiple phase retardation films with different optical properties. The first phase retardation film (200-280nm) and second phase retardation film (80-170nm) work together as a composite system to compensate for material dispersion effects. This composite approach enables accurate polarization state conversion despite the complexity of the folded optical path and beam splitting operations.
3Device complexity
If a single phase retardation film is used, then the structure is simple, but the conversion efficiency between circularly and linearly polarized light is insufficient and ghosting persists
Solution Approach 1:
Instead of using a single phase retardation film, the patent segments the function into multiple films with different phase retardation values. The first film (200-280nm) and second film (80-170nm) are positioned at specific orientations (90-180 degrees and 135-315 degrees respectively relative to the reflection axis). This segmentation enables each film to address specific wavelength ranges and polarization states, significantly improving conversion efficiency and eliminating ghosting while keeping the overall structure manageable.
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
Effectively reduces ghosting and stray light, improving imaging quality by optimizing the conversion of polarization states and achieving achromatic dispersion.
Implementation Method 1
The first phase retardation film has a phase retardation R01 of 200 to 280 nm, and the second phase retardation film has a phase retardation R02 of 80 to 170 nm
Implementation Method 2
a reflective polarizing layer, and a first phase retardation film group... the reflective polarizing layer is located on a second surface of the at least one lens
Data Source
AI summary
An optical structure and a display device are provided. The optical structure includes a lens, a transflective film, a reflective polarizing layer, and a first phase retardation film group. The first phase retardation film group includes a first phase retardation film and a second phase retardation film. The second phase retardation film is between the first phase retardation film and the transflective film. The first phase retardation film has a phase retardation of 200 to 280 nm, and the second phase retardation film has a phase retardation of 80 to 170 nm. An included angle between a slow axis of the first phase retardation film and a reflection axis of the reflective polarizing layer ranges from 90 to 180 degrees, and an included angle between a slow axis of the second phase retardation film and the reflection axis of the reflective polarizing layer ranges from 135 to 315 degrees.