Tablet, smartphone, information desk, ticket machine or touch table – touch technology has made its way into all areas of life. There are a variety of touch technologies available that work in different ways, tracking touches using infrared light, pressure or even sound waves.
But which technology is the best? Of course, there are pros and cons to each type of touch screen, and each type can be suitable for a variety of application scenarios. In this article, we present the most widely used single- and multi-touch technologies and list the pros and cons of each.
Resistive touch displays use pressure for input. They consist of two panels covered with electrically conductive layers and separated by a small air gap. When someone applies pressure to the panel, whether by touching it with a finger, stylus or by placing something on the screen, the two layers touch. The resistance between the two layers is measured, which can then determine the location on the display where the contact takes place.
The advantages of resistive touch panels include very low production costs, flexibility in the type of touch (gloves, prosthetics or styluses can be used) and the durability of the screens to water and dust.
Resistive touchscreens cannot support multi-touch - only one touch point is recognised. This not only means that the screens are unsuitable for multiple users, but also that certain gestures are not recognised, such as pinching with two fingers to zoom. Due to the conductive layers, it is also often difficult to see the content on the display in bright light conditions such as direct sunlight. These screens often show more wear and tear during use, as users must apply pressure to the screen for a touch to be recognised.
In infrared touch displays, infrared light emitters and receivers are installed in a frame around the screen in front of the monitor glass. This creates a grid of infrared rays on the surface of the screen. When an object or finger touches the screen, the infrared light in this area is blocked and the position of the touch or object is then calculated using triangulation.
Infrared touch technology is robust because the display does not need to be touched or pushed for touch input, and any type of glass can be used for the monitor. IR touch displays do not rely on capacitance, so these optical devices work just as well with gloves or a plastic stylus as they do with a bare finger or metal object. The sensors are also very accurate, responsive, and comparatively inexpensive.
Touch input is dependent on the light situation and can be disturbed when exposed to sunlight or halogen light. Dust or dirt on the sensors can also lead to malfunctions. Furthermore, the number of simultaneous touch points is limited by the structure of the light barrier network. Infrared touchscreens support multitouch use, but not with the quality and accuracy that users are familiar with from their smartphones. Infrared screens can have blind spots, areas that do not register a touch, if the light sources and sensors do not properly cover the entire display. Multitouch object recognition is also not possible, as everything that breaks through the infrared rays is only evaluated as a touch point – rotation, for example, can’t be measured.
InGlassTM technology works in a similar way to classic infrared touch technology: sensors that transmit and receive infrared light are built in and form a kind of light curtain. However, they sit behind the glass pane of the display so that the light is guided directly through the glass. When the glass is touched, the light is disturbed and shows the sensors where the finger is.
The technology is characterised by high input precision, which makes it well suited for writing with passive pens or styluses. It also automatically distinguishes between pen, finger, and palm, which offers usability advantages when using touchscreen whiteboards. It also enables pressure strength detection with the finger, which means that an additional interaction level can be used, e.g. for zooming in and out. Multitouch use with 40 simultaneous touch points is also possible with InGlassTM displays. Ambient light is no longer a critical factor with this type of infrared touch recognition, so it works well in most light conditions.
Unfortunately, InGlassTM technology does not allow multitouch object recognition and is not optimally suited for multitouch tables. Capacitive and non-capacitive objects or dirt can equally cause a disturbance of the light network and thus lead to errors. Greasy fingers, for example, can leave a stain that is briefly recognised as a finger and triggers the corresponding touch effect.
Unlike resistive touchscreens, capacitive touchscreens use the electrical properties of the human body as input. In today's PCAP touchscreens, there is a conductive layer in the form of a wafer-thin grid on the back of the glass panel. It projects a capacitive field through the pane. If an electrically conductive object or finger touches the glass pane, the capacitance at the intersection points of the conductive layer changes, allowing the position of the touch to be calculated. PCAP technology is now the most widely used touch technology, as it is used in virtually all tablets and smartphones, as well as in many large-format touchscreens.
If you are looking for a wear-resistant solution that combines high screen contrast and clarity with high and fast input accuracy, state-of-the-art capacitive touchscreens are the preferable option. Capacitive screens are exceedingly accurate, can handle multi-point input, and enable an unmatched range of functionality with object recognition and gesture recognition. Additionally, because the sensor is behind the glass, the displays are extremely robust. Changes in the ambient light situation have no effect on the sensors.
Due to the technical advantages, high-quality capacitive touchscreens can be a little more expensive than other options. They also generally react to capacitive, i.e., electrically conductive, materials. For example, liquid in the form of raindrops on a PCAP display results in touch input, which is why capacitive displays are not well suited for outdoor use. Gloves, which limit conductivity, can also make touch input difficult.
We'll have to go with the classic lawyer's answer on that one: It depends. What is your budget? In what context will it be used? Should there be expansion possibilities? Multitouch, single touch, token recognition, pen recognition? Should the display only be used on the wall or also horizontally? Are there changing environmental conditions?
Capacitive touch technology has certainly evolved in recent years. Thanks to their widespread use, especially in mobile devices, they continue to make the greatest and most promising strides in terms of performance and cost. Through the use of artificial intelligence, capacitive displays are becoming more and more accurate and even enable completely new input possibilities that expand the usage potential of touch surfaces.
At Interactive Scape, we only use projected capacitive (PCAP) touchscreens because they are by far the best and most robust solution for horizontal use such as multi-touch tables with object recognition. Also because of the vivid images and the independence from the lighting conditions in the environment.
Still not sure which touch technology would be best for your project? We will be happy to advise you on your choice of touchscreen!