Understanding Touchscreen Technology

Overview of 6 different types of touch panel technology:

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.