TOUCH SCREEN TECHNOLOGY
1.TOUCH SENSOR
A touch screen sensor is a clear glass panel with a touch responsive surface. The touch sensor/panel is placed over a display screen so that the responsive area of the panel covers the viewable area of the video screen. There are several different touch sensor technologies on the market today, each using a different method to detect touch input. The sensor generally has an electrical current or signal going through it and touching the screen causes a voltage or signal change. This voltage change is used to determine the location of the touch to the screen.
2.CONTROLLER
The controller is a small PC card that connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into information that PC can understand. The controller is usually installed inside the monitor for integrated monitors or it is housed in a plastic case for external touch add-ons/overlays. The controller determines what type of interface/connection you will need on the PC. Integrated touch monitors will have an extra cable connection on the back for the touchscreen. Controllers are available that can connect to a Serial/COM port (PC) or to a USB port (PC or Macintosh). Specialized controllers are also available that work with DVD players and other devices
3.SOFTWRE DRIVER
The driver allows the touchscreen and computer to work together. It tells the computer's operating system how to interpret the touch event information that is sent from the controller. Most touch screen drivers today are a mouse-emulation type driver. This makes touching the screen as same as clicking your mouse at the same location on the screen. This allows the touchscreen to work with existing software and allows new applications to be developed without the need for touchscreen specific programming
TYPES OF TOUCH SCREEN
1. Capacitive touch screen
Capacitive touch screen technology is a popular and durable technology that is used in a wide range of applications. It has a higher clarity than resistive technology, but it only responds to finger contact and will not work with a gloved hand or pen stylus. A capacitive touch screen consists of a glass panel with a capacitive (charge storing) material coating its surface. Circuits located at corners of the screen measure the capacitance of a person touching the overlay
Capacitive touch screen technology is often recommended to customers who would like the confidence of a brand name LCD such as NEC, which the capacitive touch screen would then be retrofitted to.
Limitations of capacitive touch screen technology:
Capacitive touch screen technology is often recommended to customers who would like the confidence of a brand name LCD such as NEC, which the capacitive touch screen would then be retrofitted to.
Limitations of capacitive touch screen technology:
- Can not be used with a gloved hand
- Can not be used with stylus
- Requires periodic recalibration
- Often retrofitted to standard non-touch LCD monitors which may not be as stable when touched
- Not usually fitted to monitors when applications require dust, water, scratch or impact resistance
2. Resistive touch screen
Resistive touch screen technology consists of a glass or acrylic panel that is coated with electrically conductive and resistive layers. The thin layers are separated by invisible separator dots. When operating, an electrical current moves through the screen. When pressure is applied to the sAlthough clarity is less than with other touch screen types, resistive screens can be highly accurate and have the advantage of being pressure sensitive so it responds to any input device, including finger, gloved hand, or pen stylusResistive touch screen technology is the most cost effective technology on the market today.
It is recommended when budgets do not allow more robust solutions.
Limitations of resistive touch screen technology:
It is recommended when budgets do not allow more robust solutions.
Limitations of resistive touch screen technology:
- Can be relatively easily damaged by scratching
- Can be relatively easily damaged by poking
- Can be relatively easily damaged by impact
- Not recommended for public access applications
- Requires periodic recalibration
- Can wear through regular use over time
3. Surface Acoustic Wave (SAW) Touch
The Surface Acoustic Wave (SAW) touchscreens consist of a glass overlay with transmitting and receiving piezoelectric transducers for the X and Y axes.
The controller sends a five-megahertz electrical signal to the transmitting transduce, which converts the signal into ultrasonic waves within the surface of the glass. These eaves are directed across the touchscreen by an array of reflectors.
Reflectors on the opposite side gather and direct the waves to the receiving transducer, which reconverts them into an electrical signal. The process is repeated for each axis.
When you touch the screen, you absorb a portion of the waves traveling across it. The received signals for X and Y are compared to the stored digital maps, the change is recognized, and a coordinate is calculated.