Introduction to Touch Solutions White Paper Revision 1.0 A August 21, 2007 Densitron Corporation 10400-4 Pioneer Blvd. Santa Fe Springs, CA 90670 562-941-5000 www.Densitron.com Introduction to Touch Solutions Copyright ©2007 DENSITRON CORPORATION All rights reserved. – Proprietary Data

Introduction to Touch Solutions Copyright ©2007 DENSITRON CORPORATION All rights reserved. – Proprietary Data

1.0 Introduction Touchscreens are found in a wide range of applications, from medical and industrial to public access kiosks and retail. The ability to continue operating even when damaged along with the speed of response and whether users will have gloved hands must also be considered. Maintenance is important, as members of the public are highly likely to be dissuaded from using a kiosk if the screen is dirty and/or nonfunctional. For a touchscreen integrated into a terminal that is going to be used in a heavy industrial environment, factors may include adequate levels of protection against...

2.1 4-Wire resistive touch screen The active layers of a 4-wire type touch screen consist of a partially conductive (ITO resistive) coating applied uniformly to the panel. Conductive bus bars are screened with silver ink across opposing edges of the panel. The ridged and flexible panels are mounted with the bus bars perpendicular to each other. Measurements are made by applying a voltage gradient across one of the layers and measuring the voltage on the other layer. This measurement is made twice, once with the gradient across the ridged layer and the measurement taken from the flexible layer...

2.2 8-Wire touch screens 8-wire touch screens compensate for drift by adding 4 additional reference lines. This allows the voltage to be measured directly at the touch screen bus bars. Note: you can use an 8-wire touch screen in 4-wire mode by connecting the drive and reference lines together. Use of this type of touch screen won’t eliminate the need for an initial calibration of the touch screen but should eliminate the need for any subsequent calibrations. Figure 3 shows the construction for making the measurements. 2.3 5-Wire resistive touch screen The 5-wire touch screen differs from the...

MECHANICAL • Input Method: Finger, Gloved Finger or Stylus Pen • Touch Activation Force: Less than 110 grams • Film Surface Hardness: Meets pencil hardness 3H • Surface Durability: 10k times (250gf, pen speed 100±15mm/sec) OPTICAL Light Transmission: 81% (550nm wavelength optimized for flat-panel displays) RELIABILITY -Touch Life: More than 35 million touches in a single location ELECTRICAL • Accuracy: Standard Deviation of error is less than 1.5% on most displays. • Direction "X”: 1.5 % or less, Direction "Y”: 1.5 % or less 2.4 Resistive Touch Screen Calibration The resistance of the coatings...

corner of the display. These two readings now represent the accurate positions of two points on the LCD display. A scaling factor can now be computed for each axis and all subsequent positional measurements can be adjusted using this factor. Initial calibration is still required with an 8-wire touch screen is critical applications but periodic re-calibration is usually not required. 2.5 Resistive Touch Screen Controller The resistive touch screen controller is responsible for: Switching of the drive and sense voltage to the proper layer/axis Routing the sense voltage to the A/D converter input...

3.0 Capacitive Touch Screens • Capacitive overlay technology uses a touch sensor that is a glass overlay with a conductive coating bonded to its surface. A low current flows across the capacitive panel and established the frequencies of four oscillator circuits at the panel's corners. When the screen is touched a conductive stylus, the impedance alters the frequency of the four oscillators. The touch coordinate is calculated from the differential frequency change of the four oscillators. This, in turn, determines the X and Y coordinate of the touch activation. 3.1 Surface Capacitive Touch Screen...

Features Surface scratch hardness of up to 9H durability over 300 million touches life high light transmission rate of 93%, narrow border for easy integration Glass Thickness 1.8mm/2.8mm Accuracy 1.0% based on the diagonal dimension of the screen. Chemical Resistance to chemicals that don't affect panel per ASTM-D-1308-87(1993) and ASTM-F-1958-95. Abrasion Exceeds severe abrasion test per MIL-C-675; Surface Scratch Hardness Can withstand more than 9H 3.2 Surface Capacitive Touch Controller The controller measures the values of the current flow from the four corners and calculates the X, and Y...

It is exceptional in its ability to detect touches made by conductive objects - fingers or a conductive stylus as well as through gloves and other potential barriers (moisture, oil, gels and paints). Sophisticated sensing circuitry generates a precise profile of a touch through highly specialized data acquisition and image processing techniques. Made of strengthened glass and a laminated construction with no mechanically sensitive components, can withstand significant vibration and shock in extreme environments. Projected capacitive technology (PCT) uses embedded microfine wires within a glass...

Unlimited touches life expectancy. No moving parts. High Light Transmission- approaching 90%. Durability & Resistance to Vandalism: Shock, Scratch and Vandal resistant. Debris resistant - Impervious to surface contaminants such as dirt, grease and moisture/ rain water / ice snow. Moisture: Touch panel unaffected by severe levels of moisture or water droplets on the surface. Chemicals: Performance unaffected by cleaning solutions. "Through Glass" feature - can work through shop glass windows or through a piece of sacrificial glass placed in front of the touch sensor; the software has an adjustment...

4.0 Infrared Touch Screens Infrared touchscreens rely on the interruption of an IR light grid in front of the display screen. An opto-matrix frame is integrated into the display bezel that contains a row of LEDs and phototransistors, each mounted on two opposite sides to create a grid of invisible light. The opto-matrix frame is isolated from the outside environment by an IR transparent barrier. The IR controller sequentially pulses the LEDs to create a grid of IR light beams. When a stylus enters the grid, it obstructs the beams, causing one or more of the phototransistors to detect the absence...