Types of Touch Screens

A touch screen is any display that can be manipulated by touching it. These screens are used in everything from smartphones to GPS devices and video rental kiosks.

When a finger or another object touches the surface of the screen, it changes the voltages across the conductive and resistive layers. This signals the processor to register the touch.

Capacitive

Capacitive touch screen technology is the most popular and widely used type of touchscreen today. It has become the standard in most consumer mobile devices, and is now increasingly in use in commercial/industrial applications as well.

In general, these types of touch screens work by detecting the touch commands sent from a conductive object like your finger or a conductive pen. A common example is a swiping gesture or zooming in to increase text size.

To do this, a surface capacitive screen generates a consistent electrostatic field across its display interface and measures it to find where your conductive finger or conductive pen is located in the device’s electrostatic field.

Once the touch command has been detected, the sensor circuits in the touchscreen send the information to the controller. The processor then performs the appropriate action.

Some capacitive touchscreens use a single electrode layer, whereas others may contain multiple layers that operate by switching between them. These designs also allow for more complex input.

Other varieties of capacitive touchscreens can be based on mutual capacitance or grid capacitance. Both methods create a capacitor on a grid of electrodes that are arranged along the glass.

Each electrode layer has a small spacer that separates it from the next layer, which prevents them from touching each other while the touch panel is not in use. When your conductive finger or conductive pen touches the touch panel, the spacer dots disappear and the two layers detect the resistance change that they cause.

The resulting electrical current is then passed through the grid of electrodes and sensed by the sensors. The processor then calculates the coordinates and sends them to the display’s controller.

Another benefit of capacitive touch screen technology is that they are able to sense the application of pressure and are more responsive than resistive touchscreens. This can lead to fewer accidental touch inputs and less lag time between the touch command being sent and the action occurring.

These benefits make capacitive touch screens more desirable for business applications that require high levels of reliability and durability. They are prone to damage from dirt and fingerprint smudges, but can be minimized or prevented with surface treatments such as AG, AR, and AF.

Resistive

Resistive touch screens are the most common type of monitor in use today. They are a great fit for industrial environments, especially manufacturing, ATMs and kiosks, or medical devices that require user input.

This technology works by registering the voltage on a surface when a conductive object, like a finger or stylus, comes into contact with it. There are a few different ways to do this, but the most popular uses a transparent conductive material with a uniform resistance value over its surface.

The screen consists of two transparent conducting layers, usually ITO (Indium Tin Oxide), facing each other with a small air gap between them. When pressure is applied to the top surface of the screen, these layers meet and generate an electrical flow that the controller interprets as a touch.

When the controller sees this change in voltage, it will then convert it into X and Y coordinates and send those to the processor. The processor will then be able to understand how much force was used and what the specific touch point is on the display.

Another advantage of resistive touchscreens is that they Touch screen can operate with almost anything – gloves, pens, or even bare fingers. They also have a low production cost and are durable enough to be used in rugged environments.

They have a lot of advantages over other touch technologies, but their shortcomings must be considered carefully when choosing between them. For example, their transparency is less transmissive than glass, so they are prone to reduced brightness and a certain level of haze.

Additionally, they can be more susceptible to scratches and wear. This can cause them to lose accuracy over time.

While resistive touch screens can be useful for low-cost applications involving rugged environments, indirect sunlight and simple touch features, they are not as common as capacitive options. Capacitive touchscreens are more durable and are easier to use with gloves or styluses, but they are more complicated and can be more expensive.

Surface acoustic wave (SAW)

The surface acoustic wave (SAW) touch screen is a type of touchscreen that makes use of ultrasonic sound waves to detect touch commands. They are typically found in ATMs, amusement parks, public information kiosks, computer-based training, and other high traffic indoor environments.

These types of touchscreens are usually made out of glass, but plexiglass or polycarbonate are also common choices. The SAW touch screen works by transmitting and receiving ultrasonic sound waves that bounce off reflectors along the edges of the panel. The resulting change in the wave causes an electrical signal to be registered and sent to the controller for processing.

SAW touch screens are ideal for many applications. They have a superior image clarity and resolution, light transmission and are durable enough for repeated use without coatings, plastic films or moving parts. They can withstand chemicals such as acetone, toluene, methyl ethyl ketone, isopropyl alcohol, methyl alcohol, ethyl acetate, ammonia-based glass cleaners, gasoline and kerosene.

A SAW touch screen typically consists of a glass plate with two transmitting transducers, two receivers and reflectors placed along the edges. Each of the four transducers generates ultrasonic waves that travel over the surface of the touchscreen.

The SAW signal is reflected off each of the reflectors and back toward the transducers to produce a measurable amount of energy. This energy is detected and processed by a control unit to provide information about the current position of the user’s finger or other touch device.

In some SAW touch screens, a liquid impermeable skin or membrane is used to form a liquid impermeable, and preferably non-liquid retaining barrier extending between the touchscreen and housing. This liquid impermeable membrane can be of the same material as the closed cell foam body and preferably is formed as an integral part of the foam by molding or extruding.

The seal is mounted in a channel located in the escutcheon Touch screen 40 of upper housing 30A so that it contacts the touchscreen 10 just inside the location of reflector arrays 14. Adhesive may be used to secure the seal 32; however, adhesive should not be applied to the touchscreen because this may cause unacceptable absorption of SAW energy.

Optical

Optical touch screens are an emerging technology that is slowly making its way into the market. The technology works by using multiple sensors and lights to detect the user’s point of touch. These devices can be used for a variety of applications, including point-of-sale systems, kiosks and medical equipment.

The sensors detect a change in signal voltage, whereas the lights illuminate a particular part of the screen. This means that the technology is more accurate than other touchscreen technologies, although it’s not perfect yet.

Another advantage of optical imaging is that it is less likely to clog up with fingerprints. This is especially important on high-resolution touchscreen displays. Most of the newer models have oleophobic coatings that help reduce the amount of oil residue on the display.

Other benefits of optical imaging include a low power consumption, ease of use and high resolution. However, this technology has a few disadvantages, as well. For one, it doesn’t support multi-touch commands, such as pinch to zoom.

Additionally, the technology requires an overlay, which adds to its cost and complexity. This is a major concern for many users who prefer to keep their touchscreen devices sleek and uncluttered.

In contrast, light-based touch screen systems use infra-red or near infra-red LEDs and photo receptors arranged along the perimeter of a screen, without an overlay. These systems can be configured to operate in a wide range of conditions, including ambient light levels and temperatures.

An example of a light-based touch screen system in accordance with an embodiment of the present invention is shown in FIG. 18. This device uses four LEDs that project a beam of infra-red or near-infra-red light, substantially parallel to the surface of the screen. PDs positioned along the perimeter of the screen are activated by the LEDs to detect light reflected from the LEDs.

A touch-sensitive sub-area of the screen is designated by a user interface designer, and PDs are positioned and oriented accordingly. The PDs can be activated by a single LED or by a group of LEDs, and thereby determine the location of a pointer that touches a portion of the screen.