Optical Device Diffractive Optics Angle of Incidence Control
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Solution Overview
Problem
Existing head-mounted displays using diffractive optics elements face challenges in achieving miniaturization, wide angle of view, and high efficiency due to manufacturing difficulties and poor fit on the user's face, caused by issues with wavelength selectivity and angle of incidence in volume holograms.
Innovation Solution
The optical device incorporates a light-conducting member with a first and second diffractive optics element and a reflective layer, allowing for controlled diffraction and reflection of image light to set the angle of incidence, improving fit and reducing manufacturing complexities by using volume or surface relief holograms with specific grating periods and orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the angle of incidence is tilted to reduce wavelength selectivity, then color unevenness is reduced, but the angle of light entering and exiting the light-conducting member widens, causing poor fit on the viewer's face
Solution Approach 1:
The patent applies different angle of incidence to different regions of the light-conducting member. The tilt angle is specifically designed to vary across the optical path, allowing wavelength selectivity to be reduced in certain areas while maintaining appropriate light angles in other areas for proper facial fit. This localized differentiation resolves the contradiction between color uniformity and wearable comfort.
2Loss of energy
If a volume hologram is used to achieve high diffraction efficiency, then light utilization is improved, but the angle and wavelength of diffracted light are greatly influenced by angle of incidence, affecting angle of view and color uniformity
Solution Approach 1:
The patent employs a dynamic angle of incidence design where the light enters the light-conducting member at a tilted angle rather than normal incidence. This dynamic angular configuration allows the volume hologram to maintain high diffraction efficiency while controlling the diffracted light angles to preserve wide angle of view and color uniformity, resolving the contradiction between efficiency and adaptability.
3Ease of manufacture
If partially varying the angle of slope of interference pattern is used to suppress wavelength change, then color unevenness is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent changes the parameter of angle of incidence from normal to tilted, which simplifies the manufacturing process compared to varying the interference pattern angle slope. This parameter change achieves color unevenness reduction through the tilted incidence geometry while avoiding the manufacturing complexity of creating non-uniform interference patterns, thus resolving the contradiction between color uniformity and manufacturing simplicity.
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 enhances diffraction efficiency across a wide angle of incidence range, providing a better fit on the user's face and improving the overall usability of head-mounted displays while simplifying manufacturing.
Implementation Method 1
A diffractive optics element can control the travel direction of light by using the diffraction phenomenon
Implementation Method 2
the reflective layer is provided in a position that is struck by at least some of the diffracted image light that has entered into the light-conducting member
Data Source
AI summary
An optical device includes a light-conducting member, having a first panel surface disposed facing an image forming unit, that conducts image light incident on a light entry plane formed at an end of the first panel surface to a light exit plane formed in front of the viewer's eye; a first diffractive optics element, provided on the light entry plane, that diffracts the image light incident on the light entry plane in a predetermined direction and transmits that light into the light-conducting member; a second diffractive optics element, provided on the light exit plane, that diffracts the image light exiting from the light exit plane in a predetermined direction and transmits that light to the front of the viewer's eye; and one or more reflective planes disposed within a waveguide for the image light diffracted by the first diffractive optics element.