What Is a Touch Screen?
Touch screens are a form of input device that can be found on phones, computers, e-readers, and many other devices. They can be used to select, dial, text, play games and navigate through applications.
There are several different types of touch screen technology, but the three most popular are resistive, capacitive and haptics. Learn about each one and find out how they work by WONDERing with us today!
Capacitive
Capacitive touchscreens use the conductive touch of a human finger or a specialized stylus to control devices. The technology is more durable than resistive touch screens and requires less physical force to register a touch input.
These displays are used in a wide range of consumer and commercial applications including ATMs, kiosks, and mobile phones. They provide a smooth, high-resolution and more precise touch experience.
The capacitive display panel is made of an insulating surface layer (normally glass) that is then coated with a transparent conductive material. The technology works by detecting changes in the conductive layer that are caused by a change in the user’s body electrical conductivity.
When the conductive layer of the panel is touched, it becomes a functional capacitor, which means that it stores a small charge at the point of contact and changes the electrostatic field to signal the location of the touch. This information is then sent to the controller, which processes it and sends commands to the system accordingly.
Capacitive devices can also be equipped with “mutual” capacitance, which allows the display to detect two or more points of touch simultaneously. This can be useful for multi-touch commands that allow users to zoom in or out of web pages, for example.
Projected capacitive touch, or PCT, is a variant of the technology that uses a matrix grid of electrodes embedded in a sheet of glass to detect the location of multiple touches. Typically, this matrix grid is formed by either etching rows or columns into a conducting layer or forming a perpendicular pattern with intersecting rows or columns to create the grid; it’s comparable to the pixel grid found in many liquid crystal displays.
Since a touch on the projected capacitive screen is caused by the change in the conductive layer’s electrical conductivity, this technology does not work with gloves or any object that is not conductive. This is why it’s more popular for public environments like retail, where people will often use their fingers or a stylus.
These are the most common type of touchscreens available for smartphones and tablets. They are also used in many commercial and industrial devices, where they’re a more robust solution than resistive technology.
Infrared
Infrared touch screens use IR light-emitting diodes (LEDs) to recognize and respond to finger or object touch. They are more durable and clear than capacitive touchscreens, but they can be more sensitive to sunlight.
They are used for applications that need a high level of reliability, such as plant control systems, factory automation, and ATMs. They also provide a more intuitive user experience and offer lower energy consumption than other touchscreen technologies.
IR touch screens work by detecting interruptions of uniform infrared beams that are emitted by LEDs embedded in the frame around the overlay. Photodetectors are installed across from the LEDs to detect touch events.
The touchscreen overlay is usually a piece of glass hemmed in by the frame, which includes infrared LEDs and Touch screen photodetectors. IR LEDs emit invisible infrared beams that form grids on the surface of the overlay.
When a human finger touches the screen, the current through the film changes and the signal of X and Y position is transmitted to the computer. The sensor is not affected by dust or scratches, and it is able to distinguish a single finger or multiple fingers on the same touch point.
Because of their low power consumption, IR touch screens are suitable for long periods of operation. They are also resistant to electrical interference, including magnetic and electrostatic noises.
Another advantage of infrared touchscreen technology is that it is less susceptible to damage than capacitive screens. For example, capacitive touch screens often break when dropped, even if they are made with Gorilla Glass. Similarly, infrared screens do not require patterning on the glass, which makes them more durable and clear.
They are also available in smaller sizes than other types of touchscreens. These are particularly useful in kiosks and other portable devices where space is a concern.
Infrared touchscreens are also more flexible than resistive and capacitive screens. They can be customized to fit a specific monitor size by simply adjusting the number of LEDs and photodetectors embedded in the overlay frame.
Infrared touch screens are becoming increasingly popular as interactive flat panel displays (IFPDs) in education. They allow users to operate presentations by a dry or wet finger, pen, or stylus, and they provide excellent image clarity and color reproduction.
Acoustic
Acoustic touch screens use sound waves to detect touch commands. They’re a popular choice in applications where moisture and humidity are a concern, like restaurants and hospitals.
They are also resistant to dust. This means they’ll work regardless of how dirty the surface is.
These panels feature a series of piezoelectric transducers and reflectors along the sides of the monitor’s glass plate, creating an invisible grid of ultrasonic waves on the panel’s surface. When the panel is touched, a portion of these waves are absorbed and this change registers the location of the touch event.
This information is then sent to the controller of the touchscreen. The Touch screen processor uses this information to determine the position of the touch and responds accordingly.
In contrast to capacitive and resistive touch screen technologies, SAW technology is able to recognize the touch location within 20 milliseconds of contact, so there’s no noticeable lag or delay between the touch command and its response. This makes it ideal for multi-touch applications, where multiple fingers need to be activated at the same time.
SAW can be operated with a finger, gloved hand, or passive stylus. Customization capabilities include logos, clear icons, border buttons, and other enhancements.
They’re available in a variety of sizes and resolutions, with performance degradation typically occurring at higher screen resolutions. Elo’s IntelliTouch touch screen technology delivers accurate touch response measured on three axes using a finger, gloved hand, or soft-tip stylus.
These panels are also moisture resistant, so they can be used in humid environments without fear of damage. However, they may be damaged by outside elements, such as dirt or contaminants on the surface.
Resistive touch screens are two layers with conductive connections. Voltage is applied to the top layer, which produces a gradient across the rigid bottom layer. When a user presses the flexible top sheet, the voltage applied causes the two layers to become connected.
When a finger or conductive stylus touches these electrodes, it disrupts the electrostatic field between the two, which alters the capacitance of each one. This changes the capacitance at each addressable electrode and the electronics can measure this to detect touch.
Near Field Imaging
A touch screen is a type of interface for a computer, mobile device or tablet where the user can control functions and interact with data by touching the screen. These touchscreens use a range of different technologies to detect and register touch input. Some of these technologies are infrared-based, while others use acoustic waves to track touches.
One of the most common types of touchscreens uses a resistive technology that allows users to touch or push on an area of a screen to send commands. This is done by creating electrical contact between the top layer and bottom layer of the screen using voltage. When a finger or conductive stylus touches the screen, it disrupts the electromagnetic field created by the electrically charged layers and affects the capacitance of each electrode.
This change in capacitance can be measured by the electronics to convert it into X, Y locations that allow the system to recognize touch. Resistive touch screens are a popular choice for desktop computers and laptops, as well as televisions and other portable devices.
Capacitive touch screens are another popular option, as they provide high-performance, low-power operation. They have a flexible top layer and a rigid bottom layer separated by insulating dots, with the inside surfaces of each being coated with a transparent conductive coating. Voltage is applied across the layers, producing a gradient across each electrode that varies according to how much pressure was applied on each layer.
The ability to track multiple fingers at once allows for many different functions on the touchscreen, and makes the screen more useful for multi-user applications and touch-based controls in general. In addition to resistive and capacitive technology, some touchscreens also use infrared-based touch detection techniques.
These technologies detect touch through an array of sensors positioned underneath the display, interrupting infrared beams as they pass over the surface of the screen. The sensors can detect when a finger is almost touched, and then determine what command should be sent based on the displayed controls at the time and the location of the touch.
Several approaches have been developed to achieve this level of functionality, including planar scatter detection (PSD) and frustrated total internal reflection (FTIR). PSD uses IR light that travels through a wave guide at the TIR condition, but breaks it when a touch occurs on the screen. FTIR enables the use of multiple receivers to collect and process the incoming IR lights, enabling complex analysis of the touch information.
