Touchscreen Technologies
What touchscreen technologies are available and what type makes sense for my application?
Resistive
Resistive is the most common type of touch screen technology. It is a low-cost solution found in many touch screens, including hand-held computers, PDAs, consumer electronics, and point-of-sale-applications. The resistive screen is popular because of its relatively low price (at smaller screen sizes), and ability to use a range of input objects (fingers, gloves, hard and soft stylus).
How it works
A resistive touch screen uses a controller and a specially-coated glass overlay on the display face to produce the touch connection. The touch screen panel consists of two thin, electrically conductive layers separated by a narrow gap. When an object, such as a finger, presses down on a point on the panel’s outer surface the two layers become connected and then cause a change in the electrical current which is registered as a touch event.
Considerations
Versatility: Because resistive technology is based on pressure, you can use nearly any type of pointing device, including a finger (gloved or not), pen, or stylus
Accuracy: Resistive Touchscreens are extremely accurate, particularly when use with a stylus…since the touchscreen’s accuracy is a single display pixel. This makes it ideal for handwriting recognition and for working with small control elements.
Fewer Inadvertent Touches: Because they rely on pressure for activation, resistive touchscreens won’t typically register light touches, such as when liquids (such as rain) fall on the touchscreen.
Low Cost: Resistive touchscreens offer a more affordable alternative than other touchscreen options.
Glass-Film-Glass (GFG) Resistive
The GFG touch screen structure employs 0.2mm thin glass on top of the resistive touch screen. Thin glass features anti-scratch properties. When applying thin glass with a clear surface finish, hardness will reach 5 Mohs. GFG touch surface coatings include clear and Anti-Glare finishes. GFG touch screens are not only resistant to scratches and abrasion but also to most chemicals.
How it works
Like the standard resistive touch screen, the GFG resistive touchscreen uses a controller and a specially-coated glass overlay on the display face to produce the touch connection. The touch screen panel consists of two thin, electrically conductive layers separated by a narrow gap. When an object, such as a finger, presses down on a point on the panel’s outer surface the two layers become connected and then cause a change in the electrical current which is registered as a touch event.
Considerations
Superior Durability: The surface of a GFG panel is even more resistant to scratches and high temperatures, making it more suitable for harsh conditions.
Versatility: Because resistive technology is based on pressure, you can use nearly any type of pointing device, including a finger (gloved or not), pen, or stylus
Accuracy: Resistive Touchscreens are extremely accurate, particularly when use with a stylus…since the touchscreen’s accuracy is a single display pixel. This makes it ideal for handwriting recognition and for working with small control elements.
Fewer Inadvertent Touches: Because they rely on pressure for activation, resistive touchscreens won’t typically register light touches, such as when liquids (such as rain) fall on the touchscreen.
Infrared
Infrared technology relies on the interruption of an infrared light grid in front of the display screen. The touch frame contains a row of infrared LEDs and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light. The frame assembly comprises printed wiring boards, on which the electronics are mounted and is concealed behind an infrared-transparent bezel. Infrared touch screens are often used in manufacturing and medical applications because they can be completely sealed and operated using any number of hard or soft materials.
How it works
The bezel shields the electronics from the operating environment while allowing the infrared beams to pass through. The infrared controller sequentially pulses the LEDs to create a grid of infrared light beams. When a stylus, such as a finger, enters the grid, it obstructs the beams One or more phototransistors detect the absence of light and transmit a signal that identifies the x and y coordinates.
Considerations
High Image Clarity: This makes the infrared touchscreen well suited for large displays.
Durability: Because touches are activated by the interruption of the infrared beam grid, the infrared touchscreen isn’t affected by scratches, fingerprints and other forms of minor damage.
Versatility: Infrared touchscreens can be activated with a bare finger, gloved finger, stylus and more.
Considerations: Infrared touchscreens are susceptible to erroneously triggered commands, for example, if a foreign object comes into contact with the screen. Infrared touchscreens are more sensitive to water and moisture, as even small amounts of moisture may interfere with their operation.
Projected Capacitive
Also known as P-Cap, projected capacitive touchscreens are a variant of the capacitive touch technology. P-cap touchscreens work with gloves and are best suited for outdoor applications, as it works well in rain, snow, ice and dust.
How it works
P-Cap touchscreens are made up of a matrix of rows and columns of conductive material layered on sheets of glass. The outer layer of vandal-proof glass can be up to 18mm in thickness. When the touchscreen is energized and a conductive object such as a finger comes into contact with the glass touch panel, it distorts the electrostatic field at that specific point. Even if the glass is scratched or broken it will still function properly.
Considerations
Durability: P-Cap touchscreens are strong and durable. Functionality is typically not affected by dirt and fingerprint smudges. With no moving parts and no front coatings, projected capacitive touchscreens are extremely durable.