Virtual Image Display Device Using High Refractive Index Adhesive
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Solution Overview
Problem
Existing virtual image display devices face challenges in reducing size or thickness while maintaining a wide angle of view due to total reflection conditions on light incident angles, restricting the adoption of strong curvature lens shapes.
Innovation Solution
A virtual image display device configuration featuring a first planoconvex lens with a convex surface, a second planoconcave lens with a concave surface bonded together, a half mirror in the bonding portion, and a light-guiding portion with a high refractive index adhesive between the image element and the second lens to guide image light, allowing for miniaturization and wide-angle image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a strong curvature lens shape is adopted to reduce device size and thickness, then miniaturization is achieved, but total reflection conditions restrict the light incident angle and limit the angle of view
Solution Approach 1:
A light-guiding portion with high refractive index material is introduced as an intermediary between the image element and the second lens. This mediator enables effective light guidance at wide incident angles by reducing total reflection, allowing the system to maintain strong lens curvature for miniaturization while achieving a wide angle of view of 90 degrees or more
Solution Approach 2:
The refractive index parameter of the light-guiding portion is optimized to be 1.7 or higher. This parameter change enables the system to overcome total reflection limitations and maintain wide-angle performance with compact lens dimensions, resolving the contradiction between miniaturization and angle of view
2Length of stationary object
If a strong curvature lens shape is adopted to reduce device size, then thickness is reduced, but total reflection conditions on light incident angle are restricted
Solution Approach 1:
The light-guiding portion acts as a mediator that enables effective light guidance at wide incident angles within a compact thickness. By using high refractive index material, it reduces total reflection effects, allowing the optical system to achieve thinness while maintaining a wide range of light incident angles for wide-angle imaging
3Volume of moving object
If device miniaturization is pursued, then size is reduced, but maintaining a wide angle of view becomes difficult due to total reflection conditions
Solution Approach 1:
The light-guiding portion with high refractive index material serves as an essential intermediary in the miniaturized device, ensuring reliable image light guidance at wide angles. It overcomes total reflection limitations that would otherwise cause light loss, maintaining high guidance efficiency while enabling compact device volume
Solution Approach 2:
By optimizing the refractive index parameter to 1.7 or higher, the system maintains reliable light guidance efficiency in a miniaturized configuration. This parameter change ensures that total reflection does not compromise image quality while achieving compact device dimensions
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 reliable image light guidance and miniaturization of the device while maintaining a wide angle of view, overcoming the limitations of total reflection conditions and achieving a compact, high-performance optical system.
Implementation Method 1
a light-guiding portion keeping close contact between the image element and the second lens and configured to guide the image light
Implementation Method 2
a transmission/reflection selection member provided at a light emitting side of the first lens and configured to selectively perform transmission or reflection of the light, depending on a polarization state of the light
Implementation Method 3
a half mirror provided in a bonding portion for bonding together the convex surface and the concave surface
Data Source
AI summary
A virtual image display device includes an image element configured to display an image, a first lens disposed in an extraction position of image light and including at the image element side thereof a convex surface, a second lens disposed further toward the image element side than the first lens and including a concave surface bonded to the convex surface of the first lens, a half mirror provided in a bonding portion for bonding together the convex surface and the concave surface, a transmission/reflection selection member provided at a light emitting side of the first lens and configured to selectively perform transmission or reflection of the light depending on a polarization state of the light, and a light-guiding portion keeping close contact between the image element and the second lens and configured to guide the image light.