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     White Pages - Touchscreen Technologies
Unitronix are VarTech Systems' agent within Australia and New Zealand. VarTech supply a wide range of displays in many sizes, multiple levels of ruggedisation for survival in different environmental conditions from Naval benign to full Military specification. The majority of VarTech's range have the option of a touch screen capability. This page will explain the different forms of touch screen capabilities, these are: Optical Imaging for Large-screen LCD's, Capacitive, Surface Acoustic Wave (SAW), Infrared and Resistive. The page also contains a table comparing the capabilities of each of the touch screen technologies.
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   VarTech's Optical Imaging for Large-screen LCD's:
Optical Imaging touch screen technology revolutionises the way we interface with computer technology. Unlike many touch screen displays, the entire screen, corners included, is sensitive to the touch. This technology uses optical components. No surface coatings are used on the screens - hence images are kept crystal clear. Any method can be used to touch the screen: a finger, a gloved hand or any pointer. Only a light touch is required. Optical imaging technology provides touch sensitivity over the whole screen, including the corners. With over 400,000 touch points, accuracy is guaranteed. Optical imaging technology touch screens are calibrated just once at commissioning time.
The technology provides continuous operation with no drift, no need to recalibrate. Because optical imaging technology solutions don't employ surface coatings, the customer-facing screen is not affected by scratches or contamination. Also, the products can be easily sealed for resistance to dirt, dust and moisture, making them ideal for demanding public environments. The modular touch screen system can be replaced in the event of failure or damage, provides two-touch capability, middle mouse-key scrolling and object size recognition. Diagnostic utilities are also available. VarTech’s optical imaging touch solutions do not require special software drivers; they incorporate HID compliant USB plug-and-play interfaces.
   Capacitive Touch Screen:

Capacitive Touch Screen Workstation
Capacitive touch screen technology is recommended for use within KIOSK applications that require a "finger touch". It will not operate with either a gloved hand or with a mechanical stylus. It is made of glass, which makes it extremely durable and scratch resistant. This glass overlay has a coating that stores the charge deposited over its surface electrically. Capacitive touch screens operate using oscillator circuits that are located in each corner of the glass overlay and measure the capacitance of the area being "touched". Depending on where the person touches the overlay, the oscillators will vary in frequency. Then a touchscreen controller measures the frequency variations to ascertain the coordinates of the person's touch. When used with flat panel displays, capacitive offers drift-free stable performance that is not susceptible to deterioration over time. A capacitive touch screen is impervious to grease, dirt and water, which makes it ideal for frequent use. It can also be gasket sealed for NEMA 4 and NEMA 4X operation. Since a capacitive touch screen is made of glass, it is susceptible to breakage.
   Surface Acoustic Wave (SAW) Touch Screen:
SAW touch screen technology is suggested for use in ATMs, Amusement Parks, Banking and Financial Applications, Gaming Environments, Industrial Control Rooms and KIOSK. SAW touch cannot be used within NEMA environments, as the technology cannot be gasket sealed. It has excellent durability that allows it to continue working if scratched since the overlay for the touch sensor is a solid glass display. The disadvantage to this glass overlay is that is breakable and won't work in washdown conditions. The waves are spread across the screen by bouncing off reflector arrays along the edges of the overlay and are detected by two "receivers". The acoustic wave weakens when the user touches the glass with their finger, gloved hand or soft stylus. The coordinates are then determined by the controller circuitry that measures the time at which the amplitude declines. It is the only technology that can produce a Z-coordinate axis response. SAW technology offers drift-free stable performance that is always precise. SAW offers superior image clarity, resolution and high light transmission.
   Infrared Touch Screen:


Infrared touch screen technology is based on "legacy" technology and is becoming increasingly replaced by Resistive or Capacitive touch systems. Over the years, Infrared bezels have proven to be a very reliable technology for use in ATMs, Food Service and Preparation, KIOSK, Medical Instrumentation, Process Control Systems and Transportation Tracking applications. It does not incorporate any sort of "overlay" that could inhibit screen clarity or brightness, but instead, uses a special bezel of LEDs (light emitting diodes) along with diametrically opposing phototransistor detectors, which surround the glass of the display surface. The controller circuitry scans the screen with an invisible lattice of infra-red light beams just in front of the surface that directs a sequence of pulses to the LED's. It then detects information at the location where the LEDs have become interrupted by a stylus or finger. The infrared frame housing the transmitters can impose design constraints on operator interface products. A few limitations are (1) that they usually require low-resolution output of the monitor, (2) can produce activation without touching the screen and (3) the cost to produce the special Infrared bezel is quite high.
   Resistive Touch Screen:
Resistive touch screen technology is recommended for use in POS (Point of Sale): Grocery Stores, Hotels, Restaurants and Retail Stores; Industrial Applications: MMI (Man Machine Interface), Machine and Process Control; Portable Devices; Personal Information Management Systems; Transportation Solutions; Medical Solutions: Equipment, Instrumentation and Patient Monitoring Systems. Resistive technology generally uses a display overlay composed of layers, each with a conductive coating on the interior surface. Special separator "dots" are distributed evenly across the active area and separate the conductive interior layers. The pressure from using either a mechanical stylus or finger produces an internal electrical contact at the "action point" which supplies the controller with vertical and horizontal analog voltages for data input.

To reduce parallax for older "curved" CRT applications only, resistive touch screens are generally spherical to match the curvature of the CRT (true flat resistive touch overlays are also available for TFT flat panels and/or CRTs). Our resistive touch screens are anti-glare to reduce reflective shine intensity, which will slightly diffuse the light output throughout the screen. Resistive technology offers tremendous versatility in that activation can be initiated by; a gloved hand, fingernail, mechanical stylus or an ungloved finger. Resistive touch screens can be gasket sealed for NEMA 4 and NEMA 4X environments. Limitations include: Low light output, diffused resolution images and the a plastic surface material can be scratched if improperly touched. VarTech offers a variety of resistive touch screen displays many are available with an optional sunlight readable touch screen.
VarTech Table of Touch Screen Capabilities



For further information on our touch screen LCD products from VarTech, please visit one of our product pages: Industrial Displays,
Military Displays or Large Displays.

            

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UNITRONIX Pty Ltd
ABN 79 006 226 115
PO Box 486 Morisset NSW Australia
www.unitronix.com.au  -  sales@unitronix.com.au
 NSW - Ph: 61-2-4977-3511  -  Fax: 61-2-4977-3522
WA - Ph: 61-8-9455-2424  -  Fax: 61-8-9455-2458

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