Virtual Image Display Device with Asymmetric Concave Mirrors
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Solution Overview
Problem
Existing virtual image display technologies require a large viewing distance to minimize double images, which is not ideal and affects visibility regardless of the viewing distance.
Innovation Solution
A virtual image display device using a projection optical system with a main concave mirror and an auxiliary concave mirror, where the image display light is incident on both mirrors in specific orientations to reduce double images and improve visibility, by configuring the optical system such that the second focal distance is shorter than the first focal distance and the display unit is positioned between the focal points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large viewing distance is used to reduce double images, then the occurrence of double images is reduced, but the visibility and ease of viewing the virtual image deteriorates
Solution Approach 1:
The patent divides the single optical path into two separate optical paths (first light path L1 and second light path L2) by using two distinct reflection surfaces of the presentation plate. Each path is independently controlled through specific mirror arrangements, allowing separate optimization of image quality and double image suppression without requiring large viewing distances
Solution Approach 2:
The patent introduces intermediate mirrors (first intermediate mirror 18 and second intermediate mirror 20) as mediators to redirect and control the light paths. These intermediaries enable precise control over the orientation and convergence of light beams, allowing the system to achieve proper image focus and reduce double images without requiring the user to maintain a large viewing distance
2Ease of operation
If the viewing distance is reduced for better visibility, then the ease of viewing improves, but double images occur more frequently
Solution Approach 1:
The patent employs asymmetric optical path design where the first light path L1 and second light path L2 have different geometries and reflection angles. The main concave mirror 16 and auxiliary concave mirror 17 are positioned at different locations with different orientations, creating asymmetric light paths that converge at different focal points, thereby suppressing double images while maintaining good visibility at reduced viewing distances
Solution Approach 2:
The patent changes the optical parameters by creating two distinct focal points (first focal point F1 and second focal point F2) at different positions along the optical paths. By adjusting the positions of mirrors and presentation plate, the system optimizes the focal distances to ensure both paths deliver sharp images to the user's eye at a comfortable viewing distance, eliminating the need for large viewing distances while preventing double images
3Device complexity
If a single concave mirror is used to simplify the optical system, then the device complexity is reduced, but the ability to control multiple light paths and reduce double images deteriorates
Solution Approach 1:
The patent segments the optical system into distinct functional components: a main concave mirror 16 for collecting and directing light, an auxiliary concave mirror 17 for additional path control, and a presentation plate 22 with specifically oriented reflection surfaces. This segmentation allows each component to be optimized for its specific function, achieving superior double image reduction while maintaining reasonable system complexity through modular design
Solution Approach 2:
The patent utilizes the third dimension (spatial orientation) by arranging the first and second reflection surfaces of the presentation plate at different angles and positions. The light paths are separated in three-dimensional space, with each path having its own vertical and horizontal orientation. This dimensional separation allows independent control of multiple light paths, enabling effective double image suppression while keeping the optical system configuration manageable
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 occurrence of double images and enhances the visibility of the virtual image, providing a clearer and more stable display for the user.
Implementation Method 1
a main concave mirror 16 that reflects the image display light L toward the virtual image presentation plate 22 and an auxiliary concave mirror 18 that reflects the image display light L toward the main concave mirror 16
Implementation Method 2
The image display light includes a first display light reflected by a first principal surface of the virtual image presentation plate 22 and traveling toward the user and a second display light refracted by the first principal surface, reflected by a second principal surface of the virtual image presentation plate opposite to the first principal surface
Data Source
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AI summary
A virtual image display device 10 includes: a display unit 12 that generates an image display light by modulating an illumination light; and a projection optical system 14 that reflects the image display light L toward the virtual image presentation plate 22. The projection optical system 14 includes a main concave mirror 16 that reflects the image display light L toward the virtual image presentation plate 22 and an auxiliary concave mirror 18 that reflects the image display light L toward the main concave mirror 16. Defining a plane along both a direction of incidence and a direction of output of the image display light L on the virtual image presentation plate 22 as a reference plane, the main concave mirror 16 is provided in an orientation that causes the image display light L to be incident on the main concave mirror 16 in a direction along the reference plane, and the auxiliary concave mirror 18 is provided in an orientation that causes the image display light L to be incident on the auxiliary concave mirror 16 in a direction intersecting the reference plane.