This document describes several touch screen technologies: - Resistive touch screens use two conductive layers that make contact when touched to detect the touch location. - Capacitive touch screens detect touches by measuring changes in electrical charge on a capacitive layer when a finger touches the screen. - Surface acoustic wave technology uses ultrasonic waves that are partially absorbed when the screen is touched. - Infrared touch screens project an invisible light grid and detect touches by the absence of light signals. - Optical touch screens use line scanning cameras and infrared backlights to detect finger shadows and locate touches.

2. Components
Touch sensor
Controller
Software driver

3. RESISTIVE
 Two layers-conductive &resistive metallic
layers
 When a user touches the screen, the two
layers make contact in that exact spot.
 The change in the electrical field is noted
and the coordinates of the point of contact
are calculated by the computer

4. Capacitive
 In the capacitive system, a layer that stores
electrical charge is placed on the glass panel of
the monitor.
 When a user touches the monitor with his or her
finger, some of the charge is transferred to the
user, so the charge on the capacitive layer
decreases.
 A bare finger draws current from each corner of
the electric field, creating a voltage drop that is
measured to determine touch location.

5. Surface acoustic
wave
 Surface acoustic wave(SAW) technology
uses ultrasonic waves that pass over the
touch screen panel.
 When the panel is touched, a portion of the
wave is absorbed.
 This change in the ultrasonic waves registers
the position of the touch event and sends
this information to the controller for
processing.

6. Infrared Touch Screen
Technology
 Infrared touch screens are based on light-
beam interruption technology.
 It project an invisible grid of light a small
distance over the surface of the screen.
 When a beam is interrupted, the absence of
the signal at the collector is detected and
converted to an X/Y touch coordinate.

7. Optical
 Optical touch screen technology uses two line
scanning cameras located at the corners of the
screen.
 Infrared back lights are placed in the camera's
field of view on the other side of the screen.
 A touch shows up as a shadow and each pair of
cameras can then be pinpointed to locate the
touch or even measure the size of the touching
object

9. -rohith raj