HMD Display Prism Layout for Angled Image Output
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Solution Overview
Problem
The configuration of display, illumination, and projection optics in head-mounted devices is complicated, leading to challenges in positioning the image output effectively.
Innovation Solution
The use of a prism, specifically an achromatic prism, to decouple the position of the display and optics from the image position, allowing for angled output and addressing chromatic aberrations through materials with varying refractive indexes and optical power adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the display and optics are positioned in a straight line with the image output, then the optical path is simple and alignment is easy, but the image position cannot be displaced from the display position
Solution Approach 1:
The patent introduces a waveguide as an intermediary component between the display/optics and the final image output. The waveguide receives light from the display through an input coupler and guides it to the output coupler, enabling image position displacement while maintaining a manageable optical configuration. This mediator allows the image to be displayed at a location separate from the display device itself.
2Adaptability or versatility
If the light is in-coupled into the waveguide at an angle to displace the image output, then the image position can be adjusted, but the optical alignment becomes more complicated
Solution Approach 1:
The patent employs preliminary action by pre-configuring the waveguide with specific input and output couplers designed for angled light coupling. The waveguide structure is prepared in advance with the appropriate optical interfaces that facilitate angled light entry, thereby enabling image position adjustment without requiring complex real-time alignment adjustments during operation.
3Adaptability or versatility
If a standard prism is used to shift the exit beam angle, then the image position can be displaced, but chromatic aberrations occur due to varying refractive indexes
Solution Approach 1:
The patent employs composite materials by combining multiple prism elements made from different optical materials with varying refractive indexes. These prisms are arranged in a specific configuration where the dispersion characteristics of one prism compensate for the chromatic aberrations introduced by another. This composite approach allows for exit beam angle adjustment while maintaining optical performance quality by correcting chromatic aberrations.
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
Enables flexible fitting of the display system into various head-mounted device form factors while maintaining good optical performance and minimizing chromatic aberrations.
Implementation Method 1
achromatic prism, allowing for angled output and addressing chromatic aberrations through materials with varying refractive indexes
Implementation Method 2
addressing chromatic aberrations through materials with varying refractive indexes
Data Source
AI summary
A display system for a head mounted device (HMD) including a lens comprising a display area on the lens of the HMD, the lens having a base angle and a pantoscopic tilt, a display engine and optics, and a prism to redirect output from the optics to the display area on the lens of the HMD, accounting for the base angle and the pantoscopic tilt.