How Does It Work?
Most of the technologies discussed here operate on the principle of dividing the screen image area into a predetermined grid (dependent upon screen size and resolution capabilities). Touching one of the quadrants, of the menu selection, causing a subroutine to execute in the same manner as typing the command at the prompt line or you would with a mouse.
The first touchscreen was created by adding a transparent surface to a touch-sensitive graphics digitizer and sizing it to fit a computer monitor. The purpose was to increase the speed data could be entered into a computer.
Today, the touchscreen has been transformed into a more user-friendly and environmentally robust replacement for the computer keyboard and mouse. Because of that, touch is changing the world. With a touchscreen, people with little or no computer experience can instantly work with complex software programs, without even being aware they're doing it. And computers can go to work in places where a keyboard or mouse would too cumbersome, fragile, or impractical. There are five basic components associated with touch technology.
1. Touch Sensor: Capacitive, Resistive, SAW, WAV, etc.
2. Monitor: Either Cathode Ray Tube (CRT), LCD or Plasma on which the sensor can be fitted.
3. Controller: Which enables the sensor to work like any other peripheral.
4. Software Drive: Which allows the controller and the computer-operating system to communicate and helps the controller recognize input.
5. A computer (usually a PC) which is interfaced to the touch panel and will run the selected option for the enduser when accessed. Of course, a software application is needed which will enable you to develop new or customize existing touch applications to meet specific applications.
What are some Touch Technologies currently available?
CAPACITIVE
Capacitive touchscreens are ideal for harsh environments like retail displays, gaming, vending, public kiosks and industrial applications.
Capacitive is noted for providing a unique combination of superior durability, optical clarity and sensitivity to touch. Resistive provides exceptional touch flexibility, responding to a wide range of touch input.
Analog capacitive touchscreens are made by adding conductive coatings to a clear glass sensor. Voltage is applied to the four corners of the screen along an X-Y axis. When the screen is not in use, electrodes spread the voltage, creating a uniform field. When a finger touches the screen, the field recognizes a disturbance. The X-Y coordinate of the touch is sent from the controller to the PC serial port.
Because the glass and the bezel that mounts it to the monitor can be sealed, the touchscreen is both durable and resistant to contaminants like water, dust, dirt and grease. This makes all capacitive touchscreens ideal for harsh environments like gaming, vending, retail displays, public kiosks and industrial applications.
Analog capacitive touchscreens are made adding conductive coatings to a clear glass sensor.
Voltage is applied to the four corners of the screen along an X-Y axis.
When the screen is not in use, electrodes spread out the voltage, creating a uniform field.
When the screen is touched by a finger, the field recognizes a disturbance.
The X-Y coordinate of the touch is then sent from the controller to the PC serial port. Because the glass and the bezel that mounts it to the monitor can be sealed, the touchscreen is both durable and resistant to contaminants like water, dust, dirt and grease. This makes all capacitive touchscreens ideal for harsh environments like retail displays, gaming, vending, public kiosks and industrial applications.
RESISTIVE TOUCH
The versatility of this resistive technology makes it ideal for many industrial, point-of-sale and medical applications.
Overlaying a hard-coated, conductive polyester top sheet 1/10,000-inch on a conductive clear glass sensor makes resistive touchscreens. When the surface of this flexible, polished-finished polyester sheet is touched, it's compressed into contact with the stable glass sensor. When contact is made, voltage flows to each of the four corners in proportion to the distance from the edge. As in capacitive technology, the controller uses the current flows from along the X-Y axis to calculate the position of the touch, and via the software driver, communicates this as input to the computer's serial port.
The flexible top sheet enables the touch to be registered by any input: including gloved hand, fingernail, stylus, or credit card. And because the touch is actually registered on the stable glass bottom layer, the touchscreen continues to operate even of the top sheet is accidently torn. The versatility of this resistive technology makes it ideal for many industrial, point-of-sale and medical applications.
INFRARED
Infrared touchscreens are fabricated by adding a custom bezel (usually) to the front of a CRT utilizing Infrared Light Emitting Diodes (LED) along the horizontal and vertical X-Y axis. A touch breaks the X-Y LED beams and the sensors pass this coordinate information to the computer serial port. While infrared was once used extensively as a touch solution, short comings of this technology, i.e., low resolution, parallax problems and premature touchdown detection has led developers to employ other touch technologies utilizing the Windows3.1/95.98/NTTM operating systems.
SAW (SURFACE ACOUSTIC WAVE) / GAW (GROUNDED ACOUSTIC WAVE)
The IntelliTouch™ touch screen is a glass overlay with transmitting and receiving piezoelectric transducers for the both X and Y axis. The touchscreen controller sends a five-megahertz (5 MHz) electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the glass. These waves are directed across the front surface of 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 - a digital map of the touchscreen surface. When you touch the screen, you absorb a portion of the wave travelling across it. The received signal is then compared to the stored digital map, the change recognized, and a coordinate calculated. This process happens independently for both the X and Y axis. By measuring the amount of the signal absorbed, a Z-axis is also determined. The digitized coordinates are transmitted to the computer for processing.
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