Curved Light Guide Member for Wide-Angle Virtual Image Display
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing virtual image display apparatuses face challenges in achieving a wide viewing angle, reducing weight and size, while maintaining high performance and allowing for the simultaneous display of virtual images and external scenes without obstructing the field of view.
Innovation Solution
A virtual image display apparatus featuring a light guide member with non-axisymmetric curved surfaces, including opposite-sign curvature points, which forms an intermediate image and directs video light through a relay optical system to achieve a wide viewing angle and reduce thickness and weight, while allowing external light to be seen through without distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relay optical system with a projection lens is used to form an intermediate image, then the field of view can be covered and video light can be displayed, but the projection lens becomes large in size and obstructs reduction in size and weight
Solution Approach 1:
The patent replaces the conventional projection lens with a light guide member that utilizes optical reflection and refraction principles. The light guide member includes a light incidence surface, light emission surface, and reflection surface that work together to guide video light from the video display device to the observer's eyes without requiring a large projection lens. This substitution of optical components significantly reduces the size and weight of the optical system while maintaining the ability to form and display intermediate images.
Solution Approach 2:
The patent introduces a bent optical path configuration where the light guide member extends in a direction substantially perpendicular to the visual axis. By utilizing the third dimension (depth/thickness direction) to route the optical path, the system achieves compact lateral dimensions while maintaining effective optical functionality. The light guide member's elongated structure perpendicular to the visual axis allows the optical system to be compact in the lateral directions without compromising video light display performance.
2Volume of moving object
If a light guide member with curved emission and reflection surface is used, then the optical path can be bent and compact arrangement is achieved, but a convex portion at the center obstructs the field of view and video light becomes darkened
Solution Approach 1:
The patent divides the light guide member into functionally distinct surfaces: a light incidence surface for receiving video light, a light emission surface for transmitting video light to the observer, and a separate reflection surface for redirecting the optical path. This segmentation allows each surface to be optimized for its specific function, preventing the convex portion problem while maintaining compact size. The reflection surface is designed to reflect light without creating obstructing convex portions that would block the field of view.
Solution Approach 2:
The patent introduces a half mirror as an intermediary element on the reflection surface to enable both video light reflection and external scene transmission. The half mirror allows video light to be reflected toward the observer while simultaneously allowing external light to pass through, preventing the field of view obstruction problem. This intermediary element resolves the conflict between achieving a compact bent optical path and maintaining unobstructed field of view.
3Adaptability or versatility
If a half mirror is used to display external scene, then the external scene can be viewed, but video light is reflected twice and becomes very dark
Solution Approach 1:
The patent applies different optical properties to different regions and surfaces of the light guide member. The light emission surface has high transmittance for video light, while the reflection surface contains a half mirror with specific reflectance and transmittance characteristics. By optimizing the local optical properties of each surface, the system achieves both external scene visibility and bright video light display, avoiding the double reflection darkness problem.
Solution Approach 2:
The patent performs preliminary optimization of the half mirror's optical characteristics before final assembly. The half mirror is designed with specific reflectance and transmittance values that are predetermined to minimize video light loss while enabling external scene transmission. This preliminary design and optimization ensure that when the system is assembled, the video light maintains sufficient brightness even after reflection, while still allowing external scenes to be viewed.
4Device complexity
If the video display device is arranged above the eyes, then the optical system can be simplified, but the fit is poor and the appearance form is less desirable
Solution Approach 1:
The patent repositions the video display device from above the eyes to the side of the face, utilizing the lateral dimension for optimal placement. The light guide member is configured to extend in a direction substantially perpendicular to the visual axis, allowing the optical system to be positioned at the side of the face rather than above the eyes. This dimensional repositioning improves fit comfort and appearance while the bent optical path maintains optical functionality.
5Reliability
If the field of view is completely covered by video light, then video display performance is maximized, but the external scene is not noticed causing uneasiness
Solution Approach 1:
The patent designs the light guide member and half mirror to perform multiple functions simultaneously: guiding video light from the video display device to the observer's eyes, reflecting video light efficiently, and transmitting external light to allow the observer to see the external scene. This multi-functionality enables both video display performance and external scene visibility to be achieved without compromise, eliminating the uneasiness caused by complete field of view coverage with video light only.
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 a bright, high-performance display with a wide viewing angle, reducing the size and weight of the apparatus while maintaining excellent image quality and preventing defocusing or distortion of external light.
Implementation Method 1
a light guide member (10) having a light incidence surface (111) for making the video light (GL) incident, a light emission surface (112) for making the video light (GL) emitted, and a reflection surface (113) for reflecting the video light (GL)
Implementation Method 2
a light guide member (10) having two or more non-axisymmetric curved surfaces... an opposite-sign curvature curved surface which includes at least one opposite-sign curvature point different in sign of curvature depending on direction
Data Source
AI summary
An intermediate image is formed inside a light guide member by a projection lens or the like, whereby a small optical system having a wide viewing angle and high performance is provided. At least one curved surface among curved surfaces forming an optical system is an opposite-sign curvature curved surface having an opposite-sign curvature point different in curvature depending on direction, whereby the optical system is placed in a satisfactory aberration correction state.