Pancake Lens Optical Path Folding for Compact XR Displays
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Solution Overview
Problem
Existing display devices face challenges in achieving compact design and high optical performance without excessive physical specifications, particularly in virtual, augmented, and mixed reality systems.
Innovation Solution
An optical system incorporating a pancake lens with a display device that includes a display part, light path converter, and pancake lens part, utilizing components such as quarter wave plates, absorbing polarizing layers, and geometric phase lenses to convert and refract light paths efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional lens system is used in display devices, then optical performance can be maintained, but the device size and physical specifications become excessive
Solution Approach 1:
The pancake lens implements nested folding of the optical path within the lens structure itself. The light path is folded back and forth multiple times through the lens thickness, effectively nesting the optical trajectory inside the compact lens body, thereby achieving long optical path length in a short physical distance
Solution Approach 2:
The invention transitions from a planar optical path to a three-dimensional folded path within the lens thickness direction. By utilizing the thickness dimension of the pancake lens, the optical path is extended in the Z-direction rather than requiring lateral expansion, achieving compactness in the X-Y plane while maintaining optical performance
2Length of stationary object
If the physical specifications are reduced for compact design, then device portability is improved, but optical performance deteriorates
Solution Approach 1:
The pancake lens divides the optical path into multiple segments through internal folding. Instead of a single straight path, the light travels through multiple segmented paths within the lens, each segment contributing to the total optical length while keeping the external dimensions compact
Solution Approach 2:
The patent employs adjustable focus mechanisms within the pancake lens structure, allowing the optical path length and focal position to be dynamically adjusted. This enables the lens to maintain high optical performance across different focusing states while preserving compact form factor
3Volume of moving object
If a pancake lens structure is adopted, then compact design is achieved, but manufacturing complexity increases
Solution Approach 1:
The pancake lens integrates multiple optical functions (focusing, folding, and in some embodiments, polarization control) into a single lens structure. This multi-functionality reduces the need for separate optical components, thereby managing overall system complexity while achieving compact design
Solution Approach 2:
The patent utilizes curved optical paths and spherical or aspherical lens surfaces to achieve the folded optical path. The curved geometry allows the light to bend and fold within the lens without requiring complex mechanical structures, simplifying the overall device complexity while maintaining compact form factor
Data Source
AI summary
According to one or more embodiments of the disclosure, an optical system includes a display part including a display layer including a light-emitting element, a first quarter wave plate (QWP) on the display layer, an absorbing polarizing layer on the first QWP, and a second QWP on the absorbing polarizing layer, a light path converter on the display part, and a pancake lens part on the light path converter, wherein the display part is configured to output first light provided to the light path converter, and wherein the light path converter is configured to receive the first light and is configured to output second light of which a light path is converted based on the first light.