Prism Relay Optical System for Compact HMD Design
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Solution Overview
Problem
Existing head-mounted displays (HMDs) face challenges in reducing protrusion from the head while maintaining a wide angle of view and correcting aberrations, leading to suboptimal appearance and image quality.
Innovation Solution
The virtual image display device incorporates a relay optical system with a prism, a concave surface mirror, and a prism member with a flat surface and curved surface, which refracts and reflects image light to reduce protrusion and enhance aberration correction, allowing for a more compact and aesthetically pleasing design while providing high-resolution, less distorted virtual images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the relay optical system is disposed along the head of the observer to reduce protrusion amount, then the appearance is improved, but the ability to generate high resolution enlarged virtual image deteriorates
Solution Approach 1:
The relay optical system is divided into multiple functional components: a first relay lens for initial image formation, a second relay lens for further image processing, and a prism for optical path deflection. This segmentation allows each component to be optimized for specific functions while collectively achieving both compact positioning along the head and high image resolution.
Solution Approach 2:
The prism introduces a dimensional change in the optical path by deflecting light at specific angles. This allows the optical system to achieve compact protrusion by routing light through three-dimensional space rather than requiring a linear extension, thus reducing the protrusion amount while maintaining image quality through proper optical path management.
2Shape
If the eccentric prism is used to deflect optical path and reduce protrusion, then the appearance is improved, but aberration correction deteriorates
Solution Approach 1:
The patent combines multiple optical elements (first relay lens, second relay lens, and prism) into a unified relay optical system. This merging allows the system to achieve aberration correction through the collective action of all components, with the prism handling optical path deflection while the lenses handle image formation and aberration compensation, thereby maintaining both compact appearance and optical performance.
Solution Approach 2:
The system utilizes the refractive index and geometric parameters of the prism and lenses to control optical path deflection and aberration correction. By carefully selecting and adjusting these parameters, the system achieves both reduced protrusion and effective aberration correction, overcoming the limitations of using a prism alone.
3Shape
If the relay optical system is made compact to reduce protrusion, then the appearance is improved, but the angle of view deteriorates
Solution Approach 1:
The optical system is designed with dynamic optical path routing through the prism, which can deflect light at different angles to accommodate various viewing directions. This dynamic capability allows the compact system to maintain a wide angle of view by adaptively routing optical paths rather than being constrained by a fixed linear arrangement.
Solution Approach 2:
The prism serves as an intermediary element that mediates between the compact relay optical system and the eye. It deflects optical paths to extend the effective field of view despite the compact overall size, allowing the system to achieve both reduced protrusion and wide angle of view through this intermediate optical path manipulation.
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 reduces the protrusion amount of the ocular optical element, improving the appearance of the HMD and enabling the user to see a high-resolution, enlarged virtual image with a wider angle of view without contacting the head, while maintaining a compact and lightweight design.
Implementation Method 1
a first bending surface including a bending surface and serving as an incident surface
Implementation Method 2
a reflecting surface configured to reflect, toward the second bending surface, the image light incident from the first bending surface
Implementation Method 3
an ocular optical element configured to reflect the intermediate image toward a position assumed to be a position of an eye of an observer to generate an enlarged virtual image
Data Source
AI summary
A virtual image display device of the invention includes an image display element configured to emit image light, a relay optical system configured to generate an intermediate image of the image light emitted from the image display element, and an ocular optical element configured to reflect the intermediate image toward a position assumed to be a position of an eye of an observer to generate an enlarged virtual image. The relay optical system includes a prism, and the prism includes a first bending surface including a bending surface and serving as an incident surface, a second bending surface including a bending surface and serving as an emission surface, and a reflecting surface configured to reflect, toward the second bending surface, the image light incident from the first bending surface.