PhotoelasticTouch: Transparent Rubbery Tangible Interface using an LCD and Photoelasticity

Comments:
Jill Greczek

Summary:
This paper focused on a new method of creating a touch sensitive interface, PhotoelasticTouch, by using the photo elastic properties of a gel like substance. This was accomplished by applying a photo elastic gel with some polarizing filters on top of an LCD screen with a camera positioned above the screen pointing down. Due to the poloraization lenses, at rest no light would be seen by the camera but when pressure was applied to the surface, under the property of birefingence, the light from the LCD would be bent and make its way to the camera. This would allow the system to sense touch. Most importantly however was that the system could sense the pressure applied by observing the amount of light allowed through. If a higher pressure was applied more light would be let through as opposed to a lighter touch. Between the soft gel and the pressure sensing properties the interface gives the user a more tactile approach to interface with the computer.

Discussion:
This paper is significant because it outlines an earnest and successful attempt at providing a more tactile feel to touch interfaces. In mainstream electronics the most tactile feedback a user may receive in response to an input is a small beep or vibrate. With the photo elastic gel however, a user will receive an imediate and genuine tactile response as opposed to the somewhat faked and minorly delayed response given by many touch screens today.

The largest draw back to this project is the fact that there must be a camera mounted above the display. This makes only stationary and larger displays feasible for this technology. With touch displayed prevalent mostly in smaller mobile electronics this technology, for the time being, doesn't have much use. Due to the mounted camera the user must be aware of their head or other parts of their body that may block the camera. Also the lighting in the room must also be taken into account. The researchers used standard lighting and saw good results but this may not be the case in all situations. One of the most worrisome aspects of the project is that when the screen doesn't produce enough light the camera my not recognize a touch. Therefore white text on top of black will most likely not work as a button.

For future improvements to the system there are some key problems that need to be worked out. While the paper highlights some possible fixes such as multiple cameras to compensate for the users head or other objects blocking the view, or flashing a white background every 1/60th of a second to help alleviate the problem of a black background not producing enough light. Assuming those problems are able to be fixed I would begin to explore a method which involved mounting the camera below the screen. This would allow the tables to be moved and require much less set up and calibration.