Curved Light Guide with Diverging Structure for HMD Virtual Image
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Solution Overview
Problem
Current Head-Mounted Displays (HMDs) face challenges in generating a virtual image at infinity or a fixed distance in front of the eye using a spherically-concave curved light guide, while maintaining an undisturbed view of the surroundings and avoiding the need for additional optical elements.
Innovation Solution
A curved light guide with a spherical-concave curvature, integrated with a diverging structure such as a diffraction lens, allows light to be coupled and decoupled within the guide, generating a virtual image at infinity or a defined distance without additional optical elements, using diffractive or refractive structures optimized for specific wavelengths and angular spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a spherically-concave curved light guide is used to allow unobstructed view of surroundings, then the HMD can take the shape of ordinary eyeglasses, but it cannot generate a virtual image at infinity or fixed distance
Solution Approach 1:
The patent merges the light guiding function with the image forming function by integrating a diverging structure directly into the curved light guide. This combination allows the single component to both guide light along the concave curvature and generate a virtual image at infinity, eliminating the need for separate optical elements while maintaining the eyeglass-like shape.
Solution Approach 2:
The curved light guide is designed to perform multiple functions simultaneously: it acts as both a light guide for transmitting the imaging beam and as an image forming optical element through the integrated diverging structure. This multi-functionality enables the device to maintain concave curvature for aesthetic reasons while achieving virtual image generation at infinity.
2Manufacturing precision
If multiple coupling structures are used to achieve large output pupil, then imaging quality improves, but device complexity increases
Solution Approach 1:
The patent combines multiple coupling functions into the integrated diverging structure of the curved light guide. The diverging structure inherently provides both light guidance and image forming capabilities, eliminating the need for separate coupling structures while maintaining high imaging quality and large output pupil.
Solution Approach 2:
The curved light guide with integrated diverging structure serves as a universal optical element that performs multiple functions: light guidance, beam expansion, and virtual image generation. This multi-functionality reduces the overall number of components needed while achieving the desired imaging quality without increasing device complexity.
3Manufacturing precision
If additional optical elements are added to correct imaging errors, then image quality improves, but the HMD becomes less compact
Solution Approach 1:
The patent merges correction functions into the integrated diverging structure of the curved light guide. The diverging structure is designed to simultaneously guide light, expand the beam, and correct imaging errors related to the concave curvature, eliminating the need for separate correction elements and maintaining HMD compactness.
Solution Approach 2:
The curved light guide with integrated diverging structure acts as a universal optical element that performs light guidance, beam expansion, and imaging error correction all in one component. This multi-functionality maintains the compactness of the HMD while achieving high image quality without requiring additional optical elements.
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 the generation of a virtual image at infinity or a fixed distance, enhancing the HMD's ability to provide a clear, augmented reality experience with minimal pupil distortion and chromatic aberration, while maintaining an unobstructed view of the surroundings.
Implementation Method 1
an optical fiber through which the imaging beam path for generating the virtual image is guided by internal reflection from an input structure located outside the field of view to an at least partially transparent output structure located within the eye's field of view
Implementation Method 2
Diffractive input and output structures are described, for example, in DE 10 2015 122 055 A1, US 2006/012181 A1, and US 2010/0220295 A1
Implementation Method 3
the optical fiber therefore has a diverging structure whose focal length is less than or equal to the radius of curvature of the optical fiber
Data Source
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AI summary
A curved light guide (1), which can find use as an imaging optical unit or as part of an imaging optical unit for an HMD, is disclosed. When used as intended, the light guide (1) is arranged in front of at least one eye and has a concave curvature, as seen from the eye. It comprises: – a back surface (6) facing the eye and a front surface (4) facing away from the eye, an input coupling structure (3) for coupling light into the light guide (1) in such a way that light is guided through the light guide (1) with reflection at the front surface (4) and/or the back surface (6), and – an output coupling structure (13) for output coupling the light guided through the light guide (1). The light guide (1) has a scattering structure (11), the focal length of which in terms of magnitude is less than or equal to the radius of curvature of the light guide (1).