A touch screen is a device placed over or above a display which provides a signal when the screen is mechanically touched. Touch screen data entry systems are becoming increasingly popular because of their ease and versatility of operation. Touch screen systems have been in use for a wide variety of applications, including in particular, computer graphics, computer-aided design and manufacturing systems, as well as for a variety of other applications including control panels for moderately and highly complex process machinery, scientific instruments, and the like. Various types of touch screen monitors have been developed to facilitate user interaction with graphical user interfaces (GUIs). Touch screens are gaining popularity for numerous applications, including point-of-information kiosks, vending, electronic catalogs, in-store locators, corporate training, gaming, lottery, and amusement, multimedia marketing, banking/financial transactions, ticket sales, interactive education, multimedia demos, and museum displays. Touch screens are becoming more prevalent as data input interfaces as computers and other electronic devices become more ubiquitous. Touch screens are frequently used in combination with conventional soft displays such as cathode ray tubes (CRTs), liquid crystal displays (LCDs), plasma displays and electroluminescent displays. Touch screens are widely used in many applications, including computer interfaces, and many of today's small portable devices such as personal data assistants and cellular telephones. Touch screen/LCD combinations are especially useful in such portable devices. Touch screens may now be found in workshops, warehouses, manufacturing facilities, restaurants, on hand-held personal digital assistants, automatic teller machines, casino game-machines, and the like. Touch screens may be used on large size video display units. Touch screens may also be used on small size video display units. The small size video display devices that are most commonly used with touch screen systems are liquid crystal display devices.

A touch screen system is a computer input system capable of receiving input signals for a computer through a pressure sensitive plate. Typically, a touch-screen display is electrically coupled to a computer or other host electronic device that generates images to be shown on the display. The computer is programmed to associate specific locations on the touch screen with certain predetermined input signals. Typically, a computer program generates an option to the user on a monitor underneath the touch screen panel and the conductive electrode pattern assists in detecting which option was chosen when the touch screen panel was touched by the user. A software program is prepared for execution of the touch screen command of the computer user; for instance, the program determines the response of the system when the display screen is touched at a particular X-Y coordinates. A touch sensitive element detects the coordinates of the touch event and the meaning of the touch event is determined by the coordinate location and the corresponding menu or data button displayed on the screen. When an input stylus, or a pen, or a finger touches the pressure sensitive plate at a point on the surface of the touch screen, the touch screen system senses the location of the touch point within the area of the touch screen. The touch screen system sends information concerning the location of the touch point to a computer. The touch screen action of the computer user executes any desired actions for retrieving or displaying information on a display panel. For example, touching one area of the touch screen may instruct the computer to perform a certain function and touching another area of the touch screen may instruct the computer to perform another function. Some of these displayed images can be in the form of different kinds of user controls, such as, buttons, slider bars, pull-down menus, etc. These controls are operable through user contact with the particular image, such as, for example, making finger contact with an image of a button so as to make a computerized menu selection, or to trigger a particular computer-controlled event.

A touch screen generally employs one of four types of touch technologies: capacitive, resistive, infrared, and surface acoustic wave (SAW). These are generally placed above either a CRT screen or LCD screen to provide the required interactive functionality in a single component composed of two parts. With the exception of the infrared method, each of these methods relies on a hard substrate into on onto which various signals and detecting devices are built. In general, capacitive and resistive touch technologies both rely on overlays, whereas infrared and SAW configurations typically do not require overlays. In a capacitive type of touch screen, a glass panel is coated with a conductive coating that is fused into the glass. The coating is connected to electrodes located at edges of the screen. Each electrode is connected to an oscillator circuit. When a user touches the screen, the body capacitance of the user causes a change in the impedance of the screen. The capacitive touch screen requires that the object contacting the display be at least partially electrically conductive so as to detect the contact. A human finger tip satisfies this requirement of capacitive type touch-screen displays. A resistive touch screen works by applying a voltage across a resistor network and measuring the change in resistance at a given point on the network where a screen is touched by an external source. Resistive touch screens are widely used in conventional CRTs and in flat-panel display devices in computers and in particular with portable computers. The IR technology employs an array of infrared (IR) light emitting diode (LED)/photodetector pairs mounted in a frame. In operation, the LED/photodetector array is continuously and sequentially scanned horizontally and then vertically. When a user touches the display breaking one or more of the light beams, the X-Y position of the touch can be transmitted to a controller or host computer. Today, most commercial acoustic touch screen systems employ surface acoustic waves (SAWs) as the acoustic mode propagating in a faceplate.

Resistive touch screens have a conductive coating deposited upon the substrate and a conductive, flexible cover sheet placed over the substrate that is indented by a stylus or finger to create an electrical connection between the conductive flexible cover and the conductive substrate. Resistive wire touch screens are built upon a substrate that is coated with a resistive film, typically indium tin oxide (ITO) at a specified thickness, uniformity and resistivity. The flexible cover sheet extends over the substrate except for a portion where electrical connections are made to the substrate. Electrical connections to touch screens are typically made by soldering a cable having a plurality of wires to the conductive face of the substrate in this exposed area. Resistive matrix-touch screens typically comprise a transparent plastic membrane that overlays a glass substrate. Too and bottom layers are patterned with parallel metal wires that are perpendicularly aligned to form a grid. Pressing on the top membrane forces the wires together to register a touch. Resistive analog touch screens are constructed like resistive matrix screens, but are not etched to define a wire grid. Instead, the entire surface acts as one large active area sensor. Touches are registered by measuring voltage dividers in the X and Y directions. In operation, a voltage is alternately applied along horizontal and vertical axes of the screen. When a user depresses the Mylar overlay so that its conductive layer contacts the energized layer, the resulting voltage is sensed and transmitted to a controller that converts the signal to an indication of touch location. There are three types of resistive touch screens, 4-wire, 5-wire, and 8-wire. The three types share similar structures. The main difference between 4-wire, 5-wire, and 8-wire touch screens is the circuit pattern in the lower circuit layer and the upper circuit layer, and the means for making resistance measurements. The two most popular resistive architectures use 4-wire or 5-wire configurations.

The touch screen is made of transparent material. When the touch screen is placed over a video display device, images from the video display device are visible through the touch screen. Touch screen panels generally comprise an insulative substrate and a resistive layer disposed on the insulative substrate. A pattern of conductive electrodes are then formed on the edges of the resistive layer. The conductive electrodes form orthogonal electric fields in the X and Y directions across the resistive layer. A typical touch screen employs a sheet of glass with a conductive coating such as indium tin oxide with four terminal connections, one at each corner. The touch screen may also be a capacitive or resistive touch screen with a pattern of electrodes made of conductive material. A touch screen typically involves a cathode ray tube monitor (CRT) or liquid crystal display (LCD) monitor and a transparent touch-sensitive overlay that is attached to the front face of the monitor. The touch screens are manufactured as separate devices and mechanically mated to the viewing surfaces of the displays. Touch screens can be activated by many different types of contacts, including by finger, pen, and stylus. The user touches different areas of the touch screen to activate different functions. Touch screens for computer input permit a user to write or draw information on a computer screen or select among various regions of a computer generated display, typically by the user's finger or by a free or tethered stylus.