Optical Imaging is a process for touch-sensitive multi-touch screens. In contrast to the various other processes that work with diffuse infrared light (IR) and detect and evaluate the light reflection, optical imaging works with optical sensors, digital cameras
, which evaluate the resulting shadows. In optical imaging, digital cameras are located at the corners of the multitouch surface; there are systems with two, three and four cameras. The entire surface is illuminated from behind with infrared light so that a uniform infrared radiation field builds up above the multitouch surface. When the screen
is touched, the resulting shadow is detected and evaluated by the optical sensors. From the shadow, the coordinates of the touch point, but also the size of the object with which themulti-touch screen
was touched, can be determined. This optical imaging technology is becoming increasingly important because it is extremely flexible and scalable and can be used especially in large displays with screen diagonals of up to 120". Optical imaging is suitable for single touch and dual touch, four-camera systems also for triple touch, and can detect two or three touch points simultaneously. An advantage is that scratched and worn surfaces have no influence on the results, a disadvantage is that moving liquids and dirt affect the results.