Head-Mounted Display Optical Module With Flat Wavelength Plates
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Solution Overview
Problem
Existing head-mounted displays face challenges in achieving accurate deposition and attachment of wavelength plates with curved shapes, leading to potential polarization unevenness and luminance or color unevenness in image light due to manufacturing difficulties.
Innovation Solution
The optical module employs a flat first and second wavelength plate configuration between the display element and optical member, converting image light between different polarization directions to circular and back, with a simple optical design that includes a combiner to reflect the light, reducing polarization unevenness and luminance/color unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a curved wavelength plate is used to match the reflective polarization plane, then the optical system can function, but manufacturing precision deteriorates due to difficulty in depositing and attaching curved surfaces
Solution Approach 1:
Instead of making the wavelength plate curved to match the reflective polarization plane, the patent inverts the approach by using a flat wavelength plate and designing the reflective polarization plane to be flat as well. This inversion simplifies the manufacturing process while maintaining the required optical function, as flat surfaces are much easier to deposit and attach with high precision compared to curved surfaces.
2Ease of operation
If a curved wavelength plate is used, then the optical path can be managed, but device complexity increases due to difficulty in producing the desired curved surface
Solution Approach 1:
The patent simplifies the device complexity by inverting the conventional design. Rather than producing a complex curved wavelength plate surface, it uses flat surfaces for both the wavelength plate and the reflective polarization plane. This inversion dramatically reduces the complexity of surface production while still achieving the necessary optical path control through the arrangement and orientation of the flat components.
3Adaptability or versatility
If a curved wavelength plate is used, then the optical system can be configured, but manufacturing precision deteriorates leading to polarization unevenness
Solution Approach 1:
The patent resolves the contradiction between optical configuration flexibility and polarization uniformity by inverting the design approach. It uses flat wavelength plates and flat reflective polarization planes instead of curved surfaces. This inversion ensures manufacturing precision and polarization uniformity because flat surfaces can be manufactured with high precision, while the optical configuration adaptability is maintained through the strategic arrangement and orientation of these flat 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
This design ensures accurate optical characteristics with reduced polarization unevenness, resulting in improved image quality with minimized luminance and color inconsistencies.
Implementation Method 1
a first wavelength plate that is disposed on an optical path between the display element and the optical member and that makes the image light in the first polarization direction into the image light of circular polarized light
Implementation Method 2
a second wavelength plate that is flat, that is disposed between the incident portion and the emission portion of the optical member, and that makes the image light of the circular polarized light into image light in a second polarization direction
Implementation Method 3
the emission portion reflects the image light in the second polarization direction toward the incident portion
Implementation Method 4
the incident portion reflects the image light reflected by the emission portion toward the emission portion
Data Source
AI summary
An optical module includes a display element that emits image light of P-polarized light, an optical member including an incident portion on which the image light emitted is incident and an emission portion that emits the image light, a first wavelength plate that is disposed on the optical path between the display element and the optical member and that makes the image light of the P-polarized light into image light of circular polarized light, a second wavelength plate that is flat, that disposed between the incident portion and the emission portion of the optical member, and that makes the image light of the circular polarized light into image light of S-polarized light and make the image light of the S-polarized light into image light of P-polarized light, and a combiner that reflects the image light emitted from the optical member.