There are several different technologies on the market today that comprise the realm of touch screen electronics. The different types of common touch screen technologies that are offered today include: Resistive Touch, Projected Capacitive, SAW, and Infrared Touch.
When you are in the market for a visual solution with touch functionality, a variety of factors should be taken into consideration. Depending on the application of the touch screen, operators may need multi-touch, touch-and-hold functions, or pinch-and-spread options to perform resizing and zooming. Will the operator of the touch screen be wearing gloves? Will the operator always be wearing gloves? Does the system need to work for both gloved and non-gloves operators? Read on for more details.
This section describes the different touch screen technologies and will familiarize you with the pros and cons of each type. ZMicro's dedicated to providing you with the highest quality solutions for your unique challenges. We are your source for next generation computing and display technologies.
Resistive Touch – The resistive touch screen comprises many thin layers (plastic film, polarization layers, insulating spacers, glass, etc.) that are attached on top of the display screen. Most importantly, and where the resistive touch screen adopts its name, is from two electrically-resistive layers with a micro-thin wire grid system built in, that are separated by transparent insulating spacers. When the operator presses the screen, he/she compresses the insulators and narrow gap, conducting a current between these two layers. This transmits the current and communicates a signal with the display. Similar to the pointer of a computer mouse, the display registers the action by way of a USB or other serial host connection.
- Pros: High-resistance to liquid, low cost technology, accommodates gloved & ungloved fingers
- Cons: Apply force to press down, can be damaged by sharp objects, lesser contrast means more layers and more reflections
Surface Acoustic Wave or SAW– This technology sends an ultrasonic acoustic wave along the surface of the touch panel. Sensors register the position of a touch by measuring where waves have been absorbed. Outside elements can damage this type of touch panel, and an unclean display can adversely affect performance.
- Pros: No conductive coatings, high repeatability and reliability, easy to clean and maintain
- Cons: Lower touch resolution, dirt/moisture negatively affects performance, expensive and can be difficult to integrate
Projected Capacitive Touch or PCT – Projected Capacitive touch screens are more accurate and robust than previous touch screen implementations. Underneath a solid piece of glass or polycarbonate, a grid with X and Y-axis is formed by electrodes. This can be done with one interlocking grid layer or two perpendicular systems with parallel lines forming a grid etched into the glass. Then the screen is coated with a transparent conductor-sensing film (generally copper or nanocarbon). Where PCT screens differ is multi-touch. Self-capacitance – Sensors on X and Y-axis operate independently, measuring capacitive load. This produces a stronger signal than mutual capacitance but is unable to accurately pinpoint the capacitive load of an additional finger. Mutual-capacitance – In this implementation there is a capacitor at each intersection of the X-Y grid. By the close proximity of a finger or conductive stylus, the sensor notices a change in the local electrostatic field which reduces the mutual capacitance. This allows for every individual point of the grid to be measured independently and concurrently.
- Pros: Allows mult-touch operations, higher image resolution and clarity, high durability
- Cons: Higher cost technology, must use finger or active stylus (conductive)
Infrared Touch – This touchscreen technology utilizes an array of X-Y grid infrared LED and photo-detector pairings. LED beams cross horizontally and vertically around the edge of the screen to detect the exact location of the touch. This technology will accept any user input (e.g. fingertip, gloved fingertip, stylus, pen, etc.). Infrared Touch technology does not require capacitors or patterning in the touch panel glass providing increased durability and unparalleled optical quality. This solution is arguably the best solution for military applications as it is the most robust and sealed touch solution.
- Pros: Allows mult-touch operations, higher image resolution and clarity, highest durability, no parallax
- Cons: Higher cost technology, require more space in electronics, subject to activation by flying objects
For more information, contact the ZMicro Sales Representative in your region.