Patent ID: 8624810

Claim:
A multi-touch system to which an LCD is applied, comprising: the LCD including a back light in which a plurality of lamp light sources and a plurality of IR light sources are repeatedly arranged in column and row directions, an LCD panel provided on the back light to display an image using light incident from the back light, and a touch panel attached onto the LCD panel; a plurality of cameras that are provided at upper edges of the LCD and in which IR light incident from the IR light sources provided in the LCD is reflected by a touch object and the reflected IR light is incident to create a touch sense image; and an IR light transmission filter provided at the front of each of the cameras, wherein the IR light transmission filter provides only the IR light transmitted from the IR light sources into the cameras, wherein the lamp light source is selected from a light emitting diode (LED), electroluminescence (EL), a cold cathode fluorescent lamp (CCFL), and an external electrode fluorescent lamp (EEFL), and wherein the LCD senses touch using a principle in which the image incident on the camera varies, the IR light transmitted from the IR light sources of the back light to the surface of the LCD is reflected by the touch object to be incident into the camera through the IR light transmission filter, and only a touch surface region by the touch object is extracted from an entire image so that the touch surface region undergoes a signal processing process and a clear touch sense image is created.