Polarization Optical System for Compact AR Display
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Solution Overview
Problem
Existing optical see-through type observation apparatuses are large and heavy due to the use of a large combiner in wide-angle schemes, with a focal length of the eyepiece optical system being longer than or at least twice the distance between the eyepiece optical system and the combiner, and a larger display element, making them cumbersome.
Innovation Solution
The apparatus includes a first polarization separating element, a first optical unit with a reflective surface and power for incident light, and a second optical unit with a half-transmissive reflective surface and phase plates, allowing external light to pass through while display light is reflected and forms an intermediate image, enabling compact design by overlapping optical paths and reducing aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a large combiner is used in a wide angle scheme, then the field of view is improved, but the apparatus becomes larger and heavier
Solution Approach 1:
The optical system is divided into multiple functional units: a first optical unit with a reflective surface, a second optical unit with a half-transmissive reflective surface, and multiple polarization separating elements. This segmentation allows each component to be optimized independently, reducing the overall size while maintaining wide-angle performance.
Solution Approach 2:
The patent implements folded optical paths where light rays are reflected multiple times through nested optical units. The first optical unit reflects light to the second optical unit, which further reflects it through polarization separating elements, creating a compact nested arrangement that reduces the physical footprint of the apparatus.
2Measurement precision
If the focal length of the eyepiece optical system is longer than or at least twice the distance between the eyepiece optical system and the combiner, then image quality is improved, but the apparatus becomes larger
Solution Approach 1:
The patent transitions from a linear optical path to a multi-dimensional folded path using polarization separating elements. Light rays are separated into different polarization components and directed through different optical units, effectively adding spatial dimensions to the optical path and achieving long focal length equivalent in a compact form factor.
Solution Approach 2:
The optical system dynamically routes light based on polarization state. The polarization separating elements selectively transmit or reflect light depending on its polarization, allowing the system to adaptively guide different light components through optimized paths that maintain image quality while reducing overall length.
3Area of stationary object
If the display element is made larger in the wide angle scheme, then the display area is improved, but the apparatus becomes larger and heavier
Solution Approach 1:
The patent employs curved or aspheric surfaces in the optical units to expand the effective display area. The reflective surfaces and half-transmissive reflective surfaces are designed with specific curvatures that widen the field of view and increase the apparent display area without requiring a physically larger display element, thereby reducing weight.
4Measurement precision
If multiple optical units with polarization separating elements are used, then aberration suppression is improved, but device complexity increases
Solution Approach 1:
The polarization separating elements serve multiple functions simultaneously: they separate s-polarized and p-polarized light, act as beam splitters, and guide light through different optical paths. This multi-functionality reduces the need for separate components for each function, thereby suppressing aberrations while limiting the increase in overall device complexity.
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 allows for a compact optical system that effectively superimposes displayed images on the external world, suppressing aberrations and unnecessary light, while maintaining clear observation of both external and displayed content.
Implementation Method 1
a first polarization separating element, configured to separate s- and p- polarized light comprising: a first polarizing beam splitter configured to transmit the s- polarized light and to reflect the p- polarized light
Implementation Method 2
a first optical unit that includes a reflective surface and has a power for incident light
Implementation Method 3
a second optical unit that includes a half-transmissive reflective surface
Implementation Method 4
a second optical unit that includes a half-transmissive reflective surface, a phase plate, and a second polarization separating element
Data Source
AI summary
An apparatus includes a display element, and an optical system configured to guide to an exit pupil the display light and external light. The optical system includes a first polarization separating element, a first optical unit, and a second optical unit that includes a half-transmissive reflective surface, a phase plate, and a second polarization separating element. The external light transmits through the first polarization separating element and the second optical unit toward the exit pupil. The display light transmits through the first polarization separating element, is reflected by the first optical unit and the first polarization separating element, is twice reflected by the second optical unit, and travels to the exit pupil. The display light forms an intermediate image in an optical path from the first optical unit to the second optical unit.