Holographic Optical Element for Head-Mounted Display Environmental Visibility
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Solution Overview
Problem
Conventional head-mounted displays obstruct the user's view of the environment due to energy loss of photons when using beam splitters or light guide devices, resulting in an ambiguous image.
Innovation Solution
An optical head-mounted display featuring a holographic optical element supported by an eyeglass frame, combined with a projector that includes a LED light source, beam-splitting polarizer, spatial light modulator, lens set, and a mechanical one-dimensional scanner, which rotates a reflective sheet to project a two-dimensional image onto the holographic optical element with reduced energy loss, allowing clear passage of light through for environmental visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If beam splitters or light guide devices are used to allow environmental visibility, then the user can see around themselves, but the image becomes ambiguous due to energy loss of photons
Solution Approach 1:
The patent extracts the beam splitter component from the optical system and replaces it with a holographic optical element that directly modulates light. This eliminates the energy loss associated with beam splitting while maintaining environmental visibility through the holographic element's ability to selectively reflect display light and transmit environmental light.
Solution Approach 2:
The patent changes the optical parameters by using a holographic optical element with specific wavelength and angle selectivity. This element can differentiate between display light (reflected) and environmental light (transmitted) based on their different optical parameters, thereby achieving both image display and environmental visibility without significant energy loss.
2Ease of operation
If the image is mapped onto the user's eyes using a mapping device, then the user can comfortably view the image, but the user cannot be aware of traffic around themselves
Solution Approach 1:
The patent merges the functions of image display and environmental visibility into a single holographic optical element. This element simultaneously reflects display light to the user's eyes and transmits environmental light, combining previously separate functions into one integrated component that maintains both comfortable viewing and environmental awareness.
Solution Approach 2:
The holographic optical element serves multiple functions: it acts as both a display light reflector and an environmental light transmitter. This multi-functional component replaces the need for separate beam splitters and light guides, providing universal optical control for both display and environmental visibility.
3Adaptability or versatility
If beam splitters are used to overcome the blocking issue, then environmental visibility is improved, but the image becomes ambiguous
Solution Approach 1:
The patent introduces a holographic optical element as an intermediary between the display light source and the user's eyes. This intermediary selectively reflects display light while transmitting environmental light based on wavelength and angle criteria, thereby maintaining image clarity without compromising environmental visibility.
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
The solution enables users to comfortably view digital images while maintaining awareness of their surroundings by minimizing photon energy loss and ensuring clear visibility of objects behind the display, thus overcoming the limitations of conventional head-mounted displays.
Implementation Method 1
the holographic optical element has properties of wavelength selectivity and angle selectivity and allows light to pass through
Implementation Method 2
the holographic optical element has properties of wavelength selectivity and angle selectivity and allows light to pass through
Implementation Method 3
The mechanical one-dimensional scanner includes a pivotable reflective sheet for reflecting the transformed light beam from the lens set onto the holographic optical element
Implementation Method 4
The beam-splitting polarizer is configured to split an incident beam from the LED light source into two light beams of differing linear polarization
Data Source
AI summary
An optical head-mounted display includes an eyeglass frame, a holographic optical element supported by the eyeglass frame to be confronted by an eye of a wearer, and a projector mounted on the eyeglass frame to project image information on the holographic optical element. The projector includes a LED light source, a beam-splitting polarizer, a spatial light modulator, a lens set and a mechanical one-dimensional scanner. The mechanical one-dimensional scanner reflects the transformed light beam from the lens set onto the holographic optical element in one dimension at a time. When the reflective sheet is rotated at a range of angle in a brief moment of time, the holographic optical element receives from the rotating reflective sheet an array of one-dimensional modulated light beams and reflects the latter to form a two-dimensional image in the eye because of persistence of vision.