Head-Mounted Display Speed-Based Convergence Adjustment
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Solution Overview
Problem
Head-mounted displays (HMDs) for navigation in low-speed transportation units, such as automobiles, bicycles, or ships, face challenges in maintaining visibility due to frequent changes in viewpoint distance, leading to increased fatigue as operators need to adjust the positions of virtual and real images, and existing solutions that detect eye lines of sight increase device weight and volume.
Innovation Solution
A display apparatus assembly that automatically adjusts the convergence angle and virtual-image distance based on movement speed, using a speed measuring device and a calculation device, and includes a semi-transmissive optical device to ensure the virtual image aligns with the real image, with features like liquid lenses and rotary movement devices to optimize image display parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the virtual image distance is set to infinite to resolve distance difference between real and virtual images, then visibility is improved for high-speed transportation, but operator fatigue increases in low-speed transportation due to frequent viewpoint changes
Solution Approach 1:
The patent applies dynamics by making the virtual image distance adjustable rather than fixed. The system dynamically changes the virtual image distance based on the movement speed of the transportation unit, transitioning from a static infinite distance setting to a dynamic adaptive setting that matches the operator's viewing needs at different speeds
Solution Approach 2:
The patent implements parameter changes by modifying the virtual image distance parameter according to movement speed. A speed measuring device detects the transportation unit's speed, and a calculation device determines the appropriate virtual image distance, which is then adjusted by the image displaying device to reduce operator fatigue while maintaining visibility
2Ease of operation
If eye line of sight detection is added to automatically adjust virtual image distance, then operator fatigue is reduced, but device weight and volume increase
Solution Approach 1:
The patent uses movement speed as an intermediary parameter to indirectly determine virtual image distance. Instead of directly detecting eye line of sight, the system measures the transportation unit's movement speed and uses this information to calculate and adjust the appropriate virtual image distance, achieving automatic adjustment without heavy eye-tracking hardware
Solution Approach 2:
The patent replaces the mechanical/complex eye-tracking system with a simpler speed-based control system. By substituting direct ocular measurement with movement speed detection, the system achieves similar functional outcomes with reduced device weight and complexity
3Reliability
If convergence angle is fixed at zero for infinite virtual image distance, then visibility is improved at high speed, but frequent adjustment is needed at low speed causing fatigue
Solution Approach 1:
The patent implements feedback by continuously monitoring the movement speed of the transportation unit and using this information to automatically adjust the virtual image distance. The speed measuring device provides real-time feedback to the calculation device, which then adjusts the convergence angle and virtual image distance accordingly, eliminating the need for manual adjustment by the operator
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
Improves visual recognition and reduces operator fatigue by dynamically adjusting image parameters to match movement speed, maintaining clear visibility without increasing device weight, volume, or power consumption.
Implementation Method 1
a light guiding plate 121 allowing the incident light to propagate the inside thereof through total reflection and output therefrom
Implementation Method 2
a first deflection unit 130 (for example, configured by a single-layer light reflecting film) reflecting the light incident to the light guiding plate 121 such that the light incident to the light guiding plate 121 is totally reflected inside the light guiding plate 121
Implementation Method 3
a second defection unit 140 (for example, configured by a multi-layer light reflecting film having a multilayered stacked structure) allowing the light that has propagated the inside of the light guiding plate 121 through total reflection to output from the light guiding plate 121
Implementation Method 4
a collimator optical system 112 that makes light emitted from the pixels of the image forming device 111 to be parallel light
Data Source
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AI summary
A display apparatus assembly includes: a display apparatus; and a speed measuring device that measures a movement speed of the display apparatus, wherein the display apparatus includes a glass-type frame that is mounted on a head of an observer and two image displaying devices for left and right eyes that are mounted in the frame, each of the image displaying devices includes an image forming device, an optical system that forms light output from the image forming device to be parallel light, and an optical device to which light output from the optical system is incident and in which the light is guided so as to be output, and a convergence angle is changed based on the movement speed of the display apparatus that is measured by the speed measuring device.