Diffused Illumination (DI) is a technique used in multi-touch screens to determine the touch point. Diffused illumination is based on the change in contrast value that occurs when the display surface is touched with a finger or stylus. In the DI process, the screen is uniformly illuminated with infrared light
(IR). If the illumination is from the front, it is called Front Diffused Illumination, if it is from the back, it is Rear Diffused Illumination. Both methods, front or rear, are the same in principle. With DI methods, the display screen is evenly illuminated with infrared light. Depending on the method, there are IR light sources in front of or behind the display screen that cast the IR light onto the display screen, where it is distributed evenly over the display screen by a diffuser. If the display screen is touched with a finger or a pen, more infrared light is reflected. The reflected light change is detected by a digital camera and the touch coordinates are determined by the camera software. Depending on the design of the diffuser, Diffused Illumination can also detect objects
that hover above the display surface without touching it.resolution, it can be affected in its results by soiling of the display surface and by ambient light, it is suitable for all screen sizes, as well as for glass and acrylic surfaces and can detect any number of touch points simultaneously.