Aerial Image Display Optics for Wide Viewing Angle and Luminance
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Solution Overview
Problem
Aerial image display apparatuses using retroreflection suffer from low light use efficiency, resulting in dark and less visible images due to diffusing light in the vertical direction, necessitating high-luminance displays like LCDs or LEDs.
Innovation Solution
The apparatus incorporates a retroreflecting layer with designed openings, a light source directly below, a diffusion layer, and a beam splitter, enhancing light use efficiency by reducing diffused reflections with a light absorbing layer or protrusions in the openings, and utilizing a polarizer and λ/4 phase film to improve luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a light guide and light diffuser are used to achieve low profile and wide viewing angle, then the viewing angle is improved, but light use efficiency deteriorates resulting in dark aerial image
Solution Approach 1:
The patent extracts the light diffuser from the conventional light guide structure and replaces it with a retroreflecting layer containing microlens arrays. This extraction eliminates the need for horizontal light diffusion while maintaining vertical light extraction, thereby improving light use efficiency without sacrificing viewing angle performance
Solution Approach 2:
The patent changes the optical parameters by using microlens arrays with specific focal lengths and aperture ratios to control light direction. By adjusting the lens parameters and arrangement density, the system achieves both wide viewing angle and high light efficiency simultaneously, resolving the contradiction between these two parameters
2Ease of operation
If a light diffuser is used to diffuse horizontal light in vertical direction, then viewing angle is improved, but light use efficiency deteriorates
Solution Approach 1:
The patent replaces the mechanical light diffusion process (using diffusers to scatter light) with an optical focusing mechanism (microlens arrays that precisely control light direction). This substitution allows light to be directed vertically with minimal loss, improving energy efficiency while maintaining the desired viewing angle through controlled light extraction
3Reliability
If conventional retroreflection structure is used, then aerial image is formed, but light use efficiency is low requiring high-luminance displays
Solution Approach 1:
The patent employs a composite structure combining retroreflecting layer with microlens arrays, beam splitter, and polarizing elements. This composite optical system efficiently guides light from the display through the beam splitter, reflects it via the retroreflecting layer, and extracts it vertically, achieving high light use efficiency (improving energy efficiency) while maintaining reliable aerial image formation
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 increases luminance and visibility of aerial images, allowing for a compact, high-luminance display with a wide angle of view using cost-effective LEDs, suitable for various equipment.
Implementation Method 1
The retroreflecting member 20 is an optical element that reflects the incident light L in the direction opposite to the incident light
Implementation Method 2
The half mirror 40 is an optical element that partly reflects and partly transmits the incident light
Implementation Method 3
The light guide 30 has, at the bottom, a light diffuser P for diffusing the light L in the vertical direction
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~4
AI summary
An aerial image display apparatus according to an embodiment of the present invention includes a retroreflecting layer in which a design including an opening for generating an aerial image is formed, a polarizer on the bottom side of the retroreflecting layer, a diffusion layer disposed below the polarizer, a light source disposed below the diffusion layer, and a polarizing beam splitter on the upper surface side of the retroreflecting layer, wherein the aerial image of the design is displayed above a polarizing beam splitter using the light source located directly below.