PhotoelasticTouch: Transparent Rubbery Tangible Interface on an LCD and Photoelasticity

PhotoelasticTouch is a tabletop system designed to facilitate touch-based interaction with real objects made from transparent elastic material. The elastic material provides a realistic haptic interface, which when combined with the visual content displayed on the LCD tabletop, enables a coupling of the physical world and digital content. The system utilizes the photoelastic properties of transparent rubber to detect when a user pushes, pulls, or pinches the object, while the LCD provides appropriate visual feedback in accordance with the stress applied to the rubber.

The technical contribution of this work is the use of the transparent photoelastic material to detect stress applied to tangible objects on the LCD. Previous force-sensitive rubbery interfaces require special markers to be embedded inside the elastic material, which impose restrictions on the shape of the object. PhotoelasticTouch does not require any markers and does not place any restrictions on the shape of the object. Therefore, the proposed system enables intuitive haptic interfaces for various interactive applications like video games and digital signage using a free-form tangible interface.

PhotoelasticTouch is composed of an LCD and an overhead camera, both fitted with a quarter-wavelength filter. When a user applies pressure to the elastic material on the LCD by pinching or pushing, the deformed area transforms incoming light into elliptically polarized light that is captured as a high-intensity region by the camera. The orientation and power of the force can be calculated by monitoring the position and size of the high-intensity region.

We have developed an entertainment application using a transparent elastic face. The user can interact with the 2.5-dimensional face model by (for example) pinching the cheek or squeezing the nose. In response to these inputs, the system displays changes in facial expression.