Preprocessing and Screen-Cursor Mapping for a Virtual TouchScreen on a Projected Area Smita Das Asst. Prof., Dept. of Computer Sc. & Engineering National Institute of Technology, Agartala Agartala, Tripura (w), India Dwijen Rudrapal, Anupam Jamatia, Lalita Kumari Asst. Prof., Dept. of Computer Sc. & Engineering National Institute of Technology, Agartala Agartala, Tripura (w), India Abstract— Virtual Touch Screen, on a projected area, is a system in which the projection on any ordinary flat surface provides us a graphical work-field for controlling specific kind of operations without any sophisticated touch sensors. Moreover, an ordinary screen area can be transformed into virtual touch screen with the use of a webcam and a projector. The webcam can take the picture of an indicator which may be a human finger with LEDs on its tip and then the touch screen is simulated by locating the indicator’s tip position on the picture to the position on the projected screen by the use of a Projector. As per the indicator’s tip movement on the picture, the cursor then moves on the projection surface. When the on screen picture is captured by the camera, several distortions may occur in the shape of the projection area due to the primitiveness of the captured picture and the picture may be more or less indistinct. Also if some parts of the picture are out of frame or out of focus then also the quality of picture may be compromised. Therefore, this paper focuses on preparing a model which, I) preprocesses the frames captured by the webcam and II) perfectly maps the indicator to the actual screen cursor by using bilinear transformation. Simulation results’, using the above proposed model, verifies the suitability of choosing such preprocessing and screen-cursor mapping in this paper. Keywords- bilinear transformation, screen-cursor mapping, virtual touch screen, touch sensors, frame preprocessing, human computer interaction. I. INTRODUCTION Virtual Touch Screen is an implementation of augmented reality [1] . Its purpose is to add virtual objects in real world or transforming the real world objects by enlarging its application areas. This leads to intensive research in area of human computer interaction (HCI) [2] . Virtual Touch Screen using projector [3] and webcam is an alternative, low cost gadget for real touch screen. The user can convert an ordinary screen into touch screen using webcam and projector to get the virtual flavor [4] of a touch screen. A beam of light is projected with a projector on an ordinary surface from some indicator tip. The projected surface can be controlled by the LEDs attached with the indicator [5] , say, our hand. To launch the proposed system, a mapping is done between the cursor and the LED’s position in the projected screen. The frame captured by the webcam is preprocessed to remove the noise and then segmentation is done to differentiate between background projections and foreground LEDs attached with indicator. II. BACKGROUND An interactive white board has massive use in education, in corporate board rooms and work groups, in training rooms for professional sports coaching, in broadcasting studios and more. A projector projects the computer's display onto the board's surface where user can control the computer using a pen, finger or other device. The board is typically mounted to a wall or floor stand. But to facilitate the system in a classroom or in any other location, we need a lot of sensors on the white board, depending on the size of the Smita Das et al. / International Journal on Computer Science and Engineering (IJCSE) ISSN : 0975-3397 Vol. 3 No. 6 June 2011 2420