Diffractive Light Guide Optics for Compact See-Through Aerial Displays
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Solution Overview
Problem
Existing image display apparatuses that form aerial images are bulky due to the need for tilted components, and they obstruct the view of scenery behind the reflective elements, preventing augmented reality displays.
Innovation Solution
An optical element comprising a light guide plate with incidence and emission diffraction elements and a positive lens, allowing components to be arranged parallelly, reducing volume and enabling transparent background viewing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reflective plane-symmetric imaging element is used to form an aerial image, then the aerial image can be displayed, but the total volume of the apparatus increases due to tilted components
Solution Approach 1:
Instead of using a reflective plane-symmetric imaging element that requires tilted components, the patent inverts the approach by using a light guide plate with diffraction elements that can operate with parallel component arrangement. The light guide plate diffracts light at specific angles to form the aerial image, eliminating the need for tilted reflective surfaces and reducing the overall apparatus volume.
Solution Approach 2:
The patent replaces the mechanical tilted arrangement of reflective components with an optical diffraction-based system. The diffraction elements on the light guide plate use optical principles to achieve the same aerial image formation function without requiring physical tilting of components, thereby reducing the mechanical complexity and volume of the apparatus.
2Reliability
If a reflective plane-symmetric imaging element is used to form an aerial image, then the aerial image can be displayed, but the scenery behind the reflective element cannot be recognized
Solution Approach 1:
The light guide plate has different local properties: the front surface contains diffraction elements for aerial image formation, while the back surface is transparent to allow scenery viewing. This local differentiation enables the same component to serve dual functions - displaying aerial images while maintaining visibility of the background scenery.
Solution Approach 2:
The light guide plate acts as an intermediary between the aerial image display function and the scenery viewing function. It diffracts light to create the aerial image while simultaneously allowing light from the scenery to pass through, mediating between these two previously conflicting requirements.
3Volume of stationary object
If components are arranged parallelly to reduce volume, then the apparatus size decreases, but achieving aerial image formation becomes difficult
Solution Approach 1:
The patent changes the operational parameters of the light guide plate by incorporating diffraction elements with specific pitch values and refractive indices. These parameter changes enable the light guide plate to diffract light at the required angles for aerial image formation even when components are arranged parallelly, thus maintaining image formation capability while reducing apparatus volume.
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 apparatus achieves a compact design while allowing simultaneous display of aerial images and scenery, facilitating augmented reality applications.
Implementation Method 1
the incidence diffraction element diffracts incident light such that the diffracted light is incident into the light guide plate
Implementation Method 2
the emission diffraction element emits light propagating in the light guide plate from the light guide plate
Implementation Method 3
the positive lens collects the light that is emitted from the light guide plate by the emission diffraction element
Data Source
AI summary
Provided are an optical element and an image display apparatus that display an aerial image, in which the total volume of the apparatus is small, a reduction in size can realized, and a scenery can be recognized. The optical element includes: a light guide element including a light guide plate, an incidence diffraction element, and an emission diffraction element, the incidence diffraction element being disposed on a main surface of the light guide plate and the emission diffraction element being disposed on the main surface of the light guide plate; and a positive lens that is disposed at a position overlapping the emission diffraction element in a view from a direction perpendicular to the main surface of the light guide plate, in which the incidence diffraction element diffracts incident light such that the diffracted light is incident into the light guide plate, the emission diffraction element emits light propagating in the light guide plate from the light guide plate, and the positive lens collects the light that is emitted from the light guide plate by the emission diffraction element.