Virtual Image Display Device Folded Optical Path
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Solution Overview
Problem
Existing virtual image display devices face challenges in miniaturization and preventing defects such as dead pixels due to temperature issues, while maintaining effective optical path lengths and avoiding interference, which are not adequately addressed by current technologies.
Innovation Solution
The virtual image display device incorporates a projection optical system with a final reflector having a concave reflection surface and specific inclination angle constraints (10°≤|θz max−θz min≤30°) to ensure a virtual image distance of at least 2,500 mm, along with additional optical elements like lens elements to correct aberrations and prevent interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the optical path length is increased to prevent interference and maintain effective image projection, then the device size increases, but miniaturization is hindered
Solution Approach 1:
The patent employs a foldable optical path design using reflectors that bend the light path at multiple angles, transforming a linear optical path into a three-dimensional folded structure. This allows the optical path length to extend in multiple spatial dimensions rather than requiring a long linear distance, thereby achieving effective optical path length while maintaining compact device footprint.
Solution Approach 2:
The optical components including reflectors, lens elements, and the projection member are arranged in a nested configuration where components are positioned within or alongside each other along the folded optical path. This nesting approach maximizes the utilization of available space, allowing long optical paths to be contained within a compact device volume.
2Reliability
If temperature control measures are implemented to prevent dead pixel defects, then device complexity increases, but reliability is improved
Solution Approach 1:
The patent introduces a heat-resistant layer as an intermediary component between the projection member and the optical path. This layer acts as a thermal barrier that protects temperature-sensitive components from excessive heat while maintaining optical functionality, thereby preventing dead pixel defects without requiring complex active cooling or heating systems.
3Manufacturing precision
If multiple optical elements are added to correct aberrations and prevent interference, then manufacturing complexity increases, but image quality is improved
Solution Approach 1:
The reflectors in the optical system are designed to serve multiple functions simultaneously: they fold the optical path to achieve compactness, correct optical aberrations through their specific geometric shapes, and position subsequent optical elements to prevent interference. This multi-functionality reduces the need for separate dedicated components, thereby improving image quality while limiting the increase in manufacturing complexity.
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 enables a compact virtual image display device that prevents defects and interference, ensuring effective image projection while maintaining a suitable virtual image distance and optical path length.
Implementation Method 1
a reflection surface of a final reflector that is included in the at least one reflector and finally reflects a light ray
Data Source
AI summary
A virtual image display device includes: a projection member that projects an image; and a projection optical system that forms a virtual image. A virtual image distance from an observer to the virtual image is not less than 2,500 mm. The projection optical system has one or more reflectors. A reflection surface of a final reflector that is included in one or more reflectors and finally reflects a light ray satisfies the following Conditional Relation 1:10°≤|θz max−θz min|≤30° Conditional Relation 1where θz is an angle between a normal vector perpendicular to a tangent plane passing through an origin of the final reflector and a normal vector with respect to a tangent plane at any given point on the final reflector, θz max is a maximum value of θz, and θz min is a minimum value of θz. This arrangement provides a small-size virtual image display device.