Head-Mounted Imaging Apparatus with Optical Coupler
Solution Overview
Problem
Conventional head-mounted displays (HMDs) face challenges in achieving sufficient eye relief, pupil size, and field of view while maintaining a compact form factor, which affects viewer comfort and the ability to superimpose virtual images over the real world effectively.
Innovation Solution
The design incorporates a head-mounted imaging apparatus with a frame housing left- and right-eye imaging apparatuses, each comprising a projector, planar waveguide, and optical coupler. The projector is supported by a temple member and emits angularly related beams, with the waveguide expanding the light beam and the optical coupler redirecting it to ensure proper alignment with the eye, allowing for compact and comfortable virtual image presentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optics are used in HMDs, then the system can achieve sufficient eye relief and pupil size, but the device size and weight increase significantly
Solution Approach 1:
The patent uses a planar waveguide to redirect light from a lateral projector position to the forward viewing direction, effectively utilizing the lateral dimension to accommodate projection optics while maintaining a compact forward profile. This allows the projector to be positioned away from the optical path while still delivering light to the waveguide input surface.
Solution Approach 2:
The planar waveguide acts as an intermediary optical element that receives light from the projector, guides it through total internal reflection, and delivers it to the output surface near the eye. This mediator enables compact integration by decoupling the projector position from the output pupil location.
2Shape
If the projection system is located to the side of the viewing path using waveguides, then the device form factor improves, but the alignment precision between projector and waveguide becomes more critical
Solution Approach 1:
The patent incorporates alignment features and mounting structures that pre-establish the correct angular and positional relationship between the projector and waveguide input surface. This preliminary alignment configuration ensures that even with manufacturing tolerances, the optical path remains properly aligned.
Solution Approach 2:
The patent specifies precise angular parameters for the projector orientation relative to the waveguide input surface, and controls the lateral displacement distance. By carefully selecting and controlling these geometric parameters, the system achieves proper optical coupling while maintaining a compact form factor.
3Area of stationary object
If the output aperture of the waveguide is spaced apart from the input aperture, then the field of view increases, but the optical path length increases requiring larger device dimensions
Solution Approach 1:
The patent uses the planar waveguide to guide light laterally across the input surface and then redirects it toward the output surface, utilizing the waveguide's internal reflection geometry to achieve spatial separation between input and output apertures without increasing the overall device length.
Solution Approach 2:
The optical path is segmented into distinct functional zones: the projector position, the waveguide input aperture region, the waveguide internal propagation path, and the output aperture region. This segmentation allows each component to be optimized independently while maintaining compact overall dimensions.
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 enables the use of compact projector optics to provide sufficient brightness and pupil size, enhancing viewer comfort and allowing for a wider field of view, thus improving the overall viewing experience by maintaining a form factor consistent with eyeglasses.
Implementation Method 1
These devices employ a series of optical diffraction gratings and total internal reflection (TIR) to laterally translate the exit pupil of a projection system
Implementation Method 2
The optical coupler receives the central projected light beam along a first axis that is at an obtuse angle with respect to the waveguide surfaces, and the optical coupler redirects the central projected light beam along a second axis that is at an acute angle with respect to the waveguide surfaces
Data Source
AI summary
A head-mounted imaging apparatus includes a frame that houses a left-eye and a right-eye imaging apparatus. Each imaging apparatus forms a virtual image to an eye of an observer and includes a projector, a planar waveguide, and an optical coupler. The projector is supported by a temple member of the frame and emits a central projected light beam along a projection axis. The planar waveguide accepts the projected light beam through an input aperture and forms an expanded light beam that is output from an output aperture and directed toward the observer's eye. The optical coupler receives the central projected light beam along a first axis that is at an obtuse angle with respect to the waveguide surface, and the optical coupler redirects the central projected light beam along a second axis that is at an acute angle with respect to the waveguide surface.