Virtual Image Display Apparatus With Inclined Optical Axis
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Solution Overview
Problem
Conventional virtual image display apparatuses for head-mounted displays face challenges in providing a compact, lightweight design while maintaining a sufficient information display area, especially when used for tasks that require viewing video while performing other activities, as they often compromise on display size and weight, leading to limited information capacity and potential shielding of the viewing field.
Innovation Solution
A virtual image display apparatus that employs a light guiding member with a vertical display range greater than its horizontal display range, where the optical axis is inclined relative to the sight line reference axis, allowing the image to be biased towards the corner of the observer's eye, enabling control over the viewing field and maintaining a large display area despite size and weight constraints. This design includes a light guiding member with multiple surfaces for aberration correction and a posture adjustment mechanism to optimize the display range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the apparatus is designed to be small and light for watching video while doing something else, then the size and weight are reduced, but the display screen size is limited and information amount is insufficient
Solution Approach 1:
The patent changes the display orientation from horizontal to vertical, making the display screen extend in the vertical direction (up-down) rather than horizontal direction (left-right). This dimensional change allows the display to fit within the compact HMD form factor while providing sufficient information display area for watching videos while performing other tasks.
Solution Approach 2:
The patent employs asymmetric optical design with the optical axis inclined at an angle (5°-30°) relative to the sight line reference axis, and the light guiding member having different width dimensions in vertical versus horizontal directions. This asymmetric configuration optimizes the display field of view and information capacity within the constrained physical dimensions of the HMD.
2Volume of moving object
If a small-sized prism is used to guide video light to reduce size and weight, then the apparatus size is reduced, but the entire apparatus becomes large and difficult to design
Solution Approach 1:
The patent divides the light guiding function into multiple surfaces (first surface, second surface, third surface, fourth surface) with distinct functions: light incident surface, light guiding surfaces with specific curvature radii, and light emitting surface. This segmentation allows each surface to be optimized independently for aberration correction and compact design.
Solution Approach 2:
The patent specifies precise parameter ranges for the light guiding member, including curvature radii (R1, R2, R3, R4) and inclination angles (5°-30°), to achieve optimal optical performance in a compact configuration. These parameter optimizations enable reduced apparatus size while maintaining design feasibility through systematic control of optical characteristics.
3Area of stationary object
If the optical axis is aligned with the sight line reference axis for direct viewing, then the viewing field is maximized, but the display range is limited in vertical direction
Solution Approach 1:
The patent intentionally misaligns the optical axis with the sight line reference axis by introducing an inclination angle of 5°-30°. This asymmetric arrangement shifts the display range toward the corner of the observer's eye, expanding the vertical display area while maintaining ease of operation through the optimized light guiding surfaces.
Solution Approach 2:
The patent expands the display range primarily in the vertical dimension by orienting the light guiding member to emit light in the vertical direction with greater width than horizontal width. This dimensional emphasis provides abundant information display capacity while the inclined optical axis configuration maintains operational ease by directing information to the peripheral corner vision area.
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 allows for a compact, lightweight apparatus that provides abundant information display with controlled viewing field shielding, ensuring easy access to video information while performing other tasks, and maintains a large display area even with stringent size and weight requirements.
Implementation Method 1
a light guiding member which guides the video light from the video element toward the eyes of the observer
Implementation Method 2
when a central axis of a ray of light, which is generated from the center of the video element, passes through the light guiding member, and reaches the center of the pupil
Data Source
AI summary
With respect to an emitting side optical axis, which is an optical axis on a first surface, a sight line reference axis which is assumed as a sight line axis of the eyes of an observer extends in a slightly inclined direction. In particular, the emitting side optical axis with respect to the sight line reference axis is configured to approach the eyes from the outside (that is, a corner of the eyes) of the eyes. In addition, a long image in a vertical direction which is perpendicular to an alignment of the eyes rather than in the horizontal direction which corresponds to the alignment of the eyes, is displayed.