Today, touch screens have become ubiquitous: they’re used on all manner of devices we encounter in our everyday lives: touch screen monitor, kiosk display, all in one tablet…
With this ever-growing surge of touch technology, it’s rather easy to miss the many uses and variations in touch screens and how each configuration actually works. Because touch technology has been in use for so long, it should come as no surprise that some of the variations have been deemed “obsolete” or are only used for very specific display applications. We present here a listing of some of the most touch screen technologies to summarize their features, benefits and Applications.
Infrared Touch
The Infrared Touch Screen is a touch frame which is usually installed in front of the display screen. The infrared touch technology depends on the interruption of an infrared light grid. The frame is integrated with a printed circuit board which contains a row of infrared LEDs and photo transistors hidden behind the bezel of the touch frame. Each of the infrared LED has a corresponding photo transistor set on the opposite end, creating a grid of invisible infrared light beams.
The frame shields the electronics from the operating environment while allowing the IR beams to pass through. The Infrared Touch Screen controller sends light pulses sequentially through the LEDs. When a user touches the screen with his finger or other styli, the infrared light beams will be interrupted. The photo transistors from X and Y axes simultaneously detect the absence of the infrared light and register the X and Y axes coordinates.
Infrared touch technology doesn’t rely on an overlay or a substrate to register a touch, so it cannot physically “wear out”, thus ensuring a long product life cycle. Possessing superior optical performance and excellent gasket-sealing properties, an infrared touch screen is ideal for harsh industrial environments and outdoor kiosks. They work with a finger, gloved hand, stylus, and almost any object wider than 1/10″. They adjust to changing light conditions, even direct sunlight. In addition, they benefit from stable, no-drift calibration performance.
Features:
- Unlimited stylus
- Single/Multi-touch
- High clarity and light transmission
- No touch pressure required
- Reliable and durable without drift-off
- Wide range of sizes from 42″ to 70″
Applications:
- Kiosk
- Interactive digital signage
- Education
- Self-service terminals
- Gaming/Amusement machines
Surface Acoustic Wave
A SAW touchscreen consists of a glass panel, transducers, reflection strips and cables. The transducers, cables and the reflection stripes are located on the front surface. The SAW controller sends electrical signals to transmitting transducers of both the X and Y axes. The transducers convert these electrical signals from the controller into ultrasonic waves which are then reflected by the reflector arrays and sent across the front, rear and side surfaces. These waves are then reflected back to the receiving transducers by another set of reflector array on each opposite side of the surface. The receiving transducers will convert the waves into electrical signals and feed them back to the controller.
Featuring pure glass construction, Surface Acoustic Wave (SAW) touch screens will almost never physically “wear out” due to a superior scratch-resistant coating. Excellent light transmission ensures that the image clarity of the display remains sharp and vibrant. The stable, “drift-free” operation means that the touch response is always accurate. These touch screens work well with a finger, gloved hand or a soft stylus. And SAW touch screens have a sensitive touch response—they recognize the touch location and the amount of pressure applied.
When the screen is touched, the finger absorbs a portion of the wave passing across the surface of the panel. The resulted change in ultrasonic wave frequency will be detected and a coordinate is calculated. This process happens independently for both the X and Y axes.
Features:
- High clarity and resolution
- Drift-free operation
- Free of maintenance
- Durable and scratch-resistant
- Sizes ranging from 5.4″ to 42″
- Sealable, anti-vandal, anti-glare optional
- Do not get affected by external electric noise
Applications:
- Gaming/Amusement machines
- Automations
- Medical equipment
- Automated cash dispenser
- Financial Field
Zero-bezel SAW
The Surface Acoustic Wave (SAW) touch screens technology is based on the proven Surface Acoustic Wave (SAW) technology. All the reflection stripes are moved to the back surface of the touchscreen. The areas where the transducers are located must flush with the front, rear and side surfaces of the glass panel so that the surfaces are continuous and even. The back surface of the glass panel where the arrays of reflectors are situated should have an opaque coating to keep the transducers and the cables from being visible at the front. The completely flat screen makes the surface perfect and easy to be integrated into monitors and other devices.
Though different from the conventional SAW technology, the iSurface touch technology delivers the same superior touch performance. With a completely flat screen, the iSurface has achieved esthetic appearance and top-notch functionality. GeneralTouch iSurface features quick and accurate responses without any drift-off. Since reflection strips are located on the back surface, it is easier to integrate iSurface touchscreen into your total solutions.
Features:
- Completely flat touchscreens
- High clarity and resolution
- Drift-free operation
- Durable and scratch-resistant
- Sizes ranging from 5.4″ to 42″
- Sealable, anti-vandal, anti-glare optional
- Easy to be integrated into monitors and other devices
Applications:
- Gaming/Amusement machines
- Automations
- Medical equipment
- Automated cash dispenser
- Financial field
- Interactive Digital Signage
Optical Imaging Touch
The conventional optical touch system uses an array of infrared light-emitting diodes (LEDs) on two adjacent bezel edges of a display, with photosensors placed on the two opposite bezel edges to analyze the system and determine a touch object. The LED and photosensor pairs create a grid of light beams across the display. An object (such as a finger or a pen) that touches the screen interrupts the light beam, causing a measured decrease in light at the corresponding photosensors. The measured photosensors outputs can be used to locate a touch point coordinate. Usually, the controller scans through the array of photosensors rather than measuring all of them simultaneously. In a more advanced version of the technology, each photosensor measures light from more than one LED, which allows the controller to compensate for light blockage caused by nonmoving debris on the screen.
The traditional type of optical touch has been used primarily in niche applications of touch market. However, its broader use has been hampered by two reasons: the primitively high cost of the touch technology compared to other competing touch technologies. The latter problem is that the background light increase the noise floor at the optical sensor, sometimes to such a degree that the touch screen’s LED light cannot be detected at all, causing a temporary failure of the touch screen. This is most pronounced in direct sunlight conditions where the sun has a very high energy distribution in the IR region.
Features:
- Multi-touch
- High light transmission
- Unlimited touch stylus and no touch pressure required
- Stable, drift-off
Applications:
- Education and training
- Retail
- Interactive digital signage
- Healthcare automations
- Kiosk
Projected Capacitive Touch
With the recent explosion in popularity of the smart phones, projected capacitive touch has grown extremely rapidly from obscurity to the top-notch touch technology.
Designed for “full multitouch” capabilities, this touch screen technology goes beyond the traditional zoom, pinch, expand and rotate functionality. It offers an interactive tool of 20 resolvable touches at less than 6 millisecond point speed. This kind of responsiveness overcomes latency issues associated with software filtering factors and/or a slow touch response rate. The anti-stiction glass surface enhances simple and advanced gestures, even with nitrile, latex or vinyl gloves. With over 3300 touch sensing points, optimal precision and accuracy are simply “business as usual”.
Projected capacitive, the touch technology used in the iPhone touch screen, has become the first choice for many small-to-medium, generally smaller than 10 inches, touch-equipped products now in development.Projected capacitive technologies detect touch by measuring the capacitance at each addressable electrode. When a finger or a conductive stylus is near the electrode, it disturbs the electromagnetic field and changes the capacitance of the electrode. This change in capacitance can be measured by the electronics and then converted into X, Y locations that the system can use to detect touch. There are two main types of sensing methods, self-capacitance and mutual capacitance.
Features:
- High durability
- Excellent optical performance (high transmissivity)
- Unlimited multi-touch (controller-dependent)
- Ease of integration
Applications:
- Small-and-medium size applications (3.5″ to 10.4″), mainly smart phones
- Embedded systems and applications
5-Wire Resistive Touch
5-Wire resistive touch technology can be used in various applications and environments. The Analog Resistive touchscreen is a sensor consisting of two opposing layers, each coated with a transparent resistive material called indium tin oxide (ITO). The ITO has a typical sheet resistivity between 100 and 500 ohms per square. The layers are separated by a pattern of very small transparent insulating dots. Silver ink bus bars (~50mW/sq) make an electrical connection to the surface of the ITO at the outside edges, spanning the desired axis of the given layer. Silver ink traces (~50mW/sq) connect the bus bars to an electromechanical connector used for interfacing to the sensor. The cover sheet has a hard, durable coating on the outer side, and a conductive coating on the inner side. When touched, the conductive coating makes electrical contact with the coating on the glass, and a touch is registered by the analog controller.
Resistive touchscreens deliver cost-effective, consistent and durable performance in environments where equipment must stand up to contaminants and liquids, such as in restaurants, factories, and hospitals. Disadvantages of Resistive technology include only 75% optical transparency and the fact that a sharp object can damage the resistive layers.
Features:
- 5 wire resistive touchscreen
- Durable plastic construction
- Simplicity of Interface Electronics
- Finger or stylus to activate touchscreen
Applications:
- Industrial Control
- Retail & Hospitality
- Healthcare
- Gaming & Amusement
- Transportation