Touchscreen technology is used in electronic visual displays. Touch panel technology is widely used and seen across the world in this day and age. From computers, mobile phones to bank ATMs, information kiosks, digital menu boards, public transport ticket machines and more.

Given its varied uses, it is not surprising that there are several different types of touchscreen technology that enable a screen to sense human touch. We’ll explore this in more detail below.

Introduction to touch panel technology

What is touch panel technology? This technology, often found in touch panel PCs, enables a user to interact with a computer/ digital device or visual display without the need to use a keyboard or mouse. Instead, users can control the device or digital display by simply touching the screen with one or two fingers, or using a special stylus.

To simplify this definition even further, touchscreens are any display that a user interacts with by directly touching it.

While it is commonplace to see and use touchscreens in our everyday lives, you may be wondering, how exactly does the touch panel technology work?

Let’s delve a little deeper into the technical aspects of this technology, beginning with what a touchscreen is made up of. A touch screen is the combination of both an input (touch panel) and output (display) device. The touch panel is normally placed on top of an electronic visual display (e.g. LCD or OLED).

On the display screen, a user can directly control the system by touching the screen with their finger or a special stylus and thus allowing the user to interact directly with what is being displayed. 

The visual display a user can interact with could be as simple as allowing the user to order food and drink via a digital menu board, or it could involve allowing the user to search their location and assist with wayfinding around a shopping centre.

Currently, there are 6 different types of touchscreen technologies and methods used for sensing touch.

1. Resistive film

2. Surface capacitive

3. Projected capacitive

4. Surface Acoustic Wave (SAW)

5. Optical imaging

6. Infrared

Resistive film 

This technology is the most widely used method for sensing touch. Resistive film detects touch through where pressure is applied to the screen. 

How can the screen detect variations in pressure? It is because resistive film touch panel technology is composed of two crucial elements: a glass panel and a film screen. Both of which are covered with a metallic layer and separated by a narrow gap. It is in the separation where pressure and touch can be detected.

For example, when a user touches the screen, the two layers (e.g. the glass panel and film screen) are pressed together due to the pressure from the user’s finger; this results in an electrical flow. The contact between the two elements closes the gap and causes a change in voltage, which is how the point of contact is then detected on the screen.

Benefits of resistive film:

• Cost-effective

• Remains fully functional, even when water is spilt on the screen

• Single-point touch reliance

• Often found in supermarkets or where digital signatures are required after card purchases

Surface capacitive 

Typically, this type of touch panel technology is used in large panel displays. This technology works due to reactions to the electrical current on the screen surface.

This touchscreen tech is made up of a transparent electrode layer being placed on top of a glass panel. They are covered with an outer protective cover. Alongside this, there are also electrode sensors located in the four corners of the screen.

This means that when a user’s finger touches the surface of the monitor screen, it reacts to the static electrical capacity of the human body. 

The reaction between the screen surface and human touch causes a decrease in capacitance (e.g. amount of electrical charge). It is the four sensors that detect the decrease and then determine the exact touchpoint. This also means that capacitive touch screens can only be activated by human touch as they hold an electrical charge.

Benefits of surface capacitive:

• Excellent surface resistance to handle spills, fingerprint grease and dust

• Highly durable and scratch proof

Projected capacitive 

Project capacitive technology is often used for smaller screens, such as mobile devices. This type of touch panel detects touch by electrical changes on the panel. It has two strong advantages: it can be activated with a finger but also when wearing certain gloves AND, it is enabled for multi-touch activation.

This method for sensing touch is composed of a sheet of glass with embedded transparent electrode films and an IC chip. These components help create a three-dimensional electrostatic field that is used to detect touch on the screen.

Benefits of projected capacitive:

• Enabled for multi-touch use

• Known for high-speed response time and precision

• Often found in smartphones, tablets and GPS devices

Surface Acoustic Wave (SAW) 

This method was developed to address the drawbacks of low light transmittance in resistive film touch panels.

SAW technology is made of a series of transducers and receivers along each of the sides of the touch panel monitor’s glass plate. These elements along the side create an invisible grid of ultrasonic surface waves on the top of the panel. 

When the surface panel is touched by a finger or stylus, a section of the surface wave is absorbed and causes the wave transmission to change. This absorption and change then allow the receiving transducer to locate the exact touchpoint and send that data to the computer.

Benefits of this technology:

• Can be activated by a finger, gloved hand or soft-tip stylus

• Easy to use

• Scratch-resistant

Infrared (IR)

Infrared (IR) touch panels fall under the common saying that some will ‘love it, or hate it’. They project a set of grid infrared beams across the panel and the touchpoint is determined by disruption to the grid.

Compared to the other touch technologies listed here, infrared touch screens do not overlay the display panel with an additional screen. As mentioned above, this technology creates an invisible grid of light beams across the screen through the infrared monitor using an IR emitter and receiver.

When an object (such as a finger or stylus) interrupts the invisible grid beam, the sensors are triggered and able to locate the touchpoint.

Benefits of this technology:

• Enabled for multi-touch functionality

• Scratch-resistant

• Optimal for indoor settings and darker areas

Optical imaging

A newer form of touchscreen technology, optical imaging senses touch through image sensors placed around the edges of the screen that emit infrared light. When the screen is touched by a finger or stylus, the touchpoint is determined by the disruption caused by the sensors and light strips.

Benefits of optical imaging:

• Versatile option for durability and multi-touch use

• Universal input options

Contact AOPEN

AOPEN supplies and manufactures a wide range of touch panel PCs. Call us today at +31 (0)73 646 6400, or email us at request@aopen.com and we’ll be in touch with you shortly.