UIST 2009: PhotoelasticTouch

Article: PhotoelasticTouch: Transparent Rubbery TangibleInterface using an LCD and Photoelasticity

Authors: Toshiki Sato, Haruko Mamiya, Hideki Koike, Kentaro Fukuchi

Summary: In this article, the authors present a new idea for a multitouch interface that is capable of a few more means of user interactions than some its competitors. Dubbed "PhotoelasticTouch" by the creators, the new system uses a high speed camera mounted on top of a desk-like device with an LCD panel built into the desk. The camera is mounted directly above the LCD in order to take a top-down picture of the activity occuring on the screen below. The interface uses a couple quarterwave plates and a Hyper-Gel sheet in order to create certain deformities of light that can be detected by the camera above, which uses a polarized lens filter in order to filter the light coming from the LCD, unless the light is caused by a deformity in the Hyper-Gel.

After the user presses on a piece of the hypergel, a deformity is caused which creates a spot of light on the LCD screen below that the camera placed above, detects. The image captured by the camera is then analyzed by the software, which uses a special algorithm to detect the size of light deformities caused in the material in order to judge the amount of force being applied to the touch screen, and from where it originated, the direction it is headed, etc. The authors then go on to describe certain applications to which the new interface is particularly suited, such as a paint application, a pressure sensitive touch panel, and a tangible face.

Shaun's Opinion: In my opinion, the idea proposed by these folks is very unique and potentially useful. However, the current way that it is setup (camera overhead that captures light deformations in the material below) seems to have some inherent flaws. If the user decides to hang their head or part of their body over the same part they are touch, no light deformations will be detected and thus nothing will happen. Not to mention the inherent impracticality of an overhead type system. This system, while unique and appealing, and certainly useful in some applications, would probably never become mainstream simply due to the bulk and size of the equipment needed to make it work properly.