Head-Mounted Display Optical Element for Focal Length Alignment
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Solution Overview
Problem
Conventional see-through head-mounted display apparatuses cause eyestrain due to differing focal lengths for images displayed in front of the user and backgrounds behind the device, leading to parallax issues.
Innovation Solution
A head-mounted display apparatus featuring a substrate with display and light-transmitting portions, combined with an optical element such as a Fresnel lens or holographic optical element, which focuses light from the display elements onto a preset point, allowing for reduced parallax and improved image perception without increasing the device's volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional see-through head-mounted display apparatus is used, then the user can perceive both displayed images and background, but the user experiences eyestrain due to different focal lengths for images and background
Solution Approach 1:
The optical element is configured with different regions: a first region corresponding to display portions that focuses light from display elements onto the retina, and a second region corresponding to light-transmitting portions that allows background light to pass through without focusing. This local differentiation enables the system to provide different optical functions in different areas, allowing users to perceive both displayed images and background at similar focal lengths, thereby reducing eyestrain
Solution Approach 2:
The optical element is divided into multiple discrete regions (first region and second region) with distinct optical functions. The first region handles displayed image light paths while the second region handles background light paths. This segmentation allows independent optimization of each region's optical properties to address the focal length conflict between displayed images and background
2Object-affected harmful factors
If an optical element is added to focus light onto a preset point, then parallax is reduced and eyestrain is minimized, but the device volume increases
Solution Approach 1:
The optical element is implemented as a thin film or shell structure that can be integrated into the head-mounted display apparatus without significantly increasing its volume. This thin-film approach maintains the focusing functionality while minimizing the space required, allowing the device to remain compact and wearable
Solution Approach 2:
The optical element is positioned in the optical path between the display unit and the user's eye, utilizing the z-dimension (depth) rather than expanding the x-y plane dimensions. This strategic placement in the optical path allows the optical element to perform its focusing function without increasing the overall device volume in a noticeable way
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 reduces user eyestrain by minimizing the difference in focal lengths for displayed images and background perception, enhancing comfort and clarity while maintaining a compact device design.
Implementation Method 1
an optical element in an optical path of light that is emitted from the display unit and having through-holes that respectively correspond to the plurality of light-transmitting portions
Implementation Method 2
The optical element may be configured to focus light emitted from the display elements onto a preset point
Implementation Method 3
The optical element may be a Fresnel lens having the through-holes
Implementation Method 4
or may be a holographic optical element (HOE) having the through-holes
Data Source
AI summary
A head-mounted display apparatus includes a display unit including a substrate and display elements, and an optical element. The substrate includes a plurality of display portions and a plurality of light-transmitting portions, and the display elements are on the plurality of display portions of the substrate. The optical element is in an optical path of light that is emitted from the display unit and has through-holes that respectively correspond to the plurality of light-transmitting portions.