Full Color Optical Combiner Using PVH and PIF Layers
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Solution Overview
Problem
Current optical combiners in AR, VR, and HUD devices face challenges in providing a full-color display due to chromatic aberration caused by wavelength-sensitive deflection, where light of different colors is deflected into different angles, leading to color crosstalk and reduced efficiency when trying to maintain a wide angle of acceptance and narrow spectral bandwidth.
Innovation Solution
The use of a combination of polarization volume holograms (PVH) and polarization interference filters (PIF) is employed, where each PVH layer is designed to deflect a specific color, and PIFs switch the polarization of light to ensure that light of different colors is deflected to the same angle, overcoming the limitations of wavelength-sensitive deflection and achieving wide angle acceptance and low chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single polarization volume hologram (PVH) is used to deflect light, then the device structure is simple, but chromatic aberration occurs because light of different colors is deflected into different angles
Solution Approach 1:
The patent divides the single PVH into multiple PVH layers, each designed to deflect a specific primary color (red, green, blue) at the correct angle. This segmentation allows each layer to be optimized for its specific wavelength range, preventing chromatic aberration while maintaining overall system simplicity
Solution Approach 2:
Each PVH layer is designed with local quality tailored to its function - the first PVH layer is optimized for red light deflection, the second for green, and the third for blue. This localized optimization ensures that each color is deflected precisely without affecting the deflection of other colors, eliminating chromatic aberration
2Manufacturing precision
If a PVH is designed for a single wavelength, then the spectral bandwidth is narrow, but the angle of acceptance becomes limited when trying to accommodate wide viewing angles
Solution Approach 1:
The patent segments the wavelength range into three distinct bands (red, green, blue) handled by separate PVH layers. Each layer is optimized for its specific wavelength band, achieving narrow spectral bandwidth and high wavelength selectivity for that band, while the combination of all three layers provides wide overall angle of acceptance
Solution Approach 2:
The patent adds the dimension of multiple layers stacked in the optical path. Instead of trying to make a single layer handle both wide angle and narrow bandwidth, the solution moves to a multi-layer structure where each layer contributes to a different color channel, achieving both wide angle of acceptance and narrow spectral bandwidth simultaneously
3Manufacturing precision
If multiple PVH layers are used to deflect different colors, then chromatic aberration is reduced, but the device complexity increases
Solution Approach 1:
The patent merges three separate PVH layers into a single integrated combiner assembly. The layers are stacked together with precise spacing, creating a unified optical element that handles all three primary colors. This merging approach maintains color alignment precision while presenting a relatively simple overall structure
Solution Approach 2:
The multi-layer PVH combiner serves multiple functions simultaneously - it deflects red, green, and blue light at the correct angles, acts as a beam combiner for the projector, and provides wide angle of acceptance. This multi-functionality justifies the increased complexity by delivering comprehensive performance in a single device
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 solution allows for a full-color optical combiner that effectively reduces chromatic aberration and maintains high deflection efficiency over a wide range of incident angles, accommodating the movement of the projector in Maxwellian view optical systems, thereby enhancing the display quality in AR and VR applications.
Implementation Method 1
a first polarization volume hologram (PVH) configured to deflect light of a first color
Implementation Method 2
In the case of volume holograms, the optical effect is based on the Bragg reflector concept. (A Bragg reflector is a material that has a periodically modulated index of refraction)
Implementation Method 3
a first polarization interference filter (PIF) configured to switch light of the first color from a polarization that is not deflected by the first PVH to a polarization that is deflected by the first PVH
Data Source
AI summary
An optical combiner includes first, second, and third polarization volume holograms (PVHs) configured to deflect light of a first color, a second color, and a third color, respectively. The optical combiner further includes a first polarization interference filter (PIF) configured to switch light of the first color from a polarization that is not deflected by the first PVH to a polarization that is deflected by the first PVH. The optical combiner may further include a second PIF configured to switch light of the second color from a polarization that is not deflected by the second PVH to a polarization that is deflected by the second PVH. The optical combiner may further include a third PIF configured to switch light of the third color from a polarization that is not deflected by the third PVH to a polarization that is deflected by the third PVH.