Interactive Projector Screen

We have seen lots of Projector Screen hacks over the last few years, this one demos the power of the system quite well. It doesn’t take much hardware to provide some fantastic results! The video game gun use is a natural extension of the technology.

"The basic idea is really simple: a program running on the PC will process the images viewed from the webcam, find the position of the penlight/light spot, and use this position to deternine where to place the mouse cursor on the screen. Now, if we can assume that the light spot/point is always the brightest object in the area, than the detection algorithm will be very simple: find the location of the pixel with the highest intensity level. We make use of two additional useful facts: 1. a normal pocket touchlights (or any incandescent lamp for that matter) actually emits several times more infrared light than visible light, and so works better as IR point source than a visible light source. 2. most webcam are able not only to detect visible lights (red, green and blue, etc) but they can also detect infrared (IR) lights – for example as emitted by the IR LEDs commonly found on TV/Hifi remote controls – which are invisible to the human eyes. So if we can somehow use the webcam to capture only the infrared lights from our light source and reject the surrounding visible lights, we will be ensured of a very reliable system. An additional feature of this system will be it will work if we replace the torchlight with any IR LEDs."