An Optical Tangible Interface by Prisms with Multilayer Light-Guiding Plates

Abstruct

The conventional transparent TUI uses optical fibers to extend the imagery from flat displays. However, since optical fiber displays only at the endpoints, images can only be displayed on the surface. In this study, we propose a “The Multilayered light-guiding prism” that uses refraction, light guiding, and diffusion. The prism makes it possible to show an imager as if it is floating inside of that. And it allows a user to show view-dependent images horizontally.

https://gyazo.com/d9b65e2e003961c75e115970f196e525

Introduction

There have been many studies using Tangible User Interface (TUI). Projection method using projector has been commonly used

in the past, but in recent years, the method using the Tabletop display which is horizontally placed has become more popular. With the Tabletop display, due to advantages in visual design, there are many examples of TUIs using transparent materials. In this study, we focused on acrylic plates, which are transparent materials, and designed a multilayered light-guide prism that can present a pseudo aerial image inside the TUI by utilizing the total reflection and light guiding properties of acrylic plates. The experience with this prism is that several people can simultaneously surround a single display and obtain a view of each user's viewpoint position through the prism.

Related Works

Displaying by Tabletop display on TUIs is easy to see, even in brightly lit environment. The displayed image is not interrupted by user’s movement. When using a tabletop display, transparent TUIs are often used. Transparent TUIs can be made to emit light using Enlighten and can display specific images on any surface of the TUI by using Laser Induced Damage. By using optical fibers, you can change the output direction of an image. Thus, transparent TUIs are capable of rich visual expression. However, transparent TUIs have challenges, such as the inability to display imagery inside the TUIs based on interactions. Since the optical fiber can only display imagery at a single point at the end, it can only display imagery on the surface. This study aims to develop new transparent TUIs in which images that change depending on the interaction appear to float inside the TUI.

Multilayer Light-guide Prism

The multilayer light-guiding prism is formed by stacking acrylic plates. This prism introduces imagery from the side of the acrylic plate, reflects it internally by total internal reflection, and outputs the imagery from the opposite side. Since the light is totally reflected inside does not go out, the stacked acrylic plates do not affect the output imagery. When multiple users place this multilayer light-guiding prism on the table-top display from their respective viewing positions, the images inside the prism are displayed in the correct perspective for each user's viewpoint. As a result, virtual 3D objects on the screen can be viewed from various angles, enabling interaction with both 2D and 3D imagery.

Design of the Multilayerd Prism​

We aims to develop new transparent TUIs, the multilayer light-guiding prism, which images that change depending on the interaction appear to float inside the TUI. The prism is 30mm-depth by 60mm -width at the bottom surface, and 8mm-depth by 60mm-width on the top. The acrylic plates are stacked slanted in such a way that the depth of the prism decreases by 2mm from the bottom surface to the top surface, for total of 12 plates stacked in a center aligned manner. In addition, an AR marker is placed on the side opposite the display surface. An acrylic material has a refractive index of 1.49. Except for the critical angle, light incident from the bottom of the prism enters the prism at all angles. the light enters the acrylic from the flat bottom of the prism and is repeatedly reflected at an angle of 30​.

https://gyazo.com/6a04a9c8e6984e4b4c0ad8bc610037f7

System

Based on the position of the prism, an image to be displayed in the prism is generated, and based on the direction of the prism, an image of the angle from the prism is generated. As a result, the final output image is determined. The output image is projected onto the prism through the tabletop display. When multiple users place this multilayer light-guiding prism on the table-top display from their respective viewing positions, the images inside the prism are displayed in the correct perspective for each user's viewpoint. As a result, virtual 3D objects on the screen can be viewed from various angles, enabling interaction with both 2D and 3D imagery.​

https://scrapbox.io/files/65786d19be6fb500240f1111.mp4