Touch screens are ubiquitous. We use them at the grocery store to check out, and at the airport to check in. They’re at visitor center kiosks, our banks, our homes and even in our cars. And today, because they’re the primary interface of smartphones, touch screens are literally in our faces for 4.2 hours every day. They are the “Black Mirror” that fans of the series will know as that part of device that reflects our image back towards us.
But despite their prevalence, few know how touch screens work. It’s not because they’re a “new” technology (they’ve been around for roughly six decades). Instead, it’s likely a failure of users to fully appreciate the ingenuity that goes into solving the unique problem of connecting humans and computers through touch. To that end, here’s a quick look on the four basic types of touch screens and how they function. But first, a little touch screen 101.
All touch screens work by creating a predictable X and Y grid pattern on the surface of the screen (Think back to the coordinate plane of your primary math class). As our fingers or stylus interacts with the grid, we introduce a disturbance. The disturbance might be a fluctuation in electrical resistance, capacitance, heat or even acoustical wave flow. The screen’s sensors then detect these changes and use them to triangulate our finger/stylus position. Finally, the sensors translate our clicks and gestures to the CPU, which executes the appropriate command (e.g., “open the app”). Simple in theory, but complex in practice.
Like any technology, touch screens have several cost-benefit factors, and manufacturers tailor their products to maximise specific benefits for different consumer needs. One common tradeoff for touch screens is accuracy vs cost. Typically, the more accurate the screen, the more expensive, due to the extra components or more expensive materials used. Screen clarity is another consideration. Some screen designs provide 100% screen illumination, while others adopt layered screens, which can dampen resolution and brightness. Other common screen characteristics include:
Consumers and businesses often trade less-needed features for more desirable ones. For example, facility access screens require more durability and “touch life,” with less consideration towards clarity and multi-touch, while smartphone makers need both (and more!) to compete.
Resistive touch screens work like an electric switch, with users pressing layers to make contact and complete the circuit.The most straightforward touch screen design is the resistive touch screens (RTS). These screens employ a multi-layered design, which includes glass covered by a thin plastic film. In between these two layers is a gap with two metallic electrodes, both resistive to electricity flow. The gap is filled with a layer of air or inert gas, and the electrodes are organized in vertical and horizontal grid lines. Essentially, resistive touch screens work like an electric switch. When the user presses the screen, the two metallic layers come into contact and completes the circuit. The device then senses the exact spot of contact on the screen.
RTS are low-cost and use little power. They’re also resistant to contaminants like water and oil, since droplets can’t “press” the screen. Almost any object can interact with the screen, so even thick gloved hands are usable. However, RTS usually offer low screen clarity and less damage/scratch resistance.
Capacitive touch screens use small electrical charges to indicate where users are pointing.One screen type you’ll find on almost every smartphone is the capacitive touch screen (CTS). These screens have three layers: a glass substrate, a transparent electrode layer and a protective layer. Their screens produce and store a constant small electrical charge or capacitance. Once the user’s finger touches the screen, it absorbs the charge and lowers the screen capacitance. Sensors located at the four corners of the screen, detect the change and determine the resulting touch point.
Capacitive screen come in two types: surface and projected (P-Cap), with the latter being the common screen type for today’s smartphones and tablets. P-Cap screens also include a thin layer of glass on top of the protective film and allows for multi-touch and thin gloved use. So, they’re popular in health care settings where users wear latex gloves.
Having fewer layers, CTS offer high screen clarity, as well as better accuracy and scratch resistance. But their electrified designs put them at risk of interference from other EMI sources. Plus, their interaction is limited to fingers and/or specialised styluses.
SAW touch screens transmit soundwaves, which are disrupted by finger touches and used to locate precise points on the screen.Surface Acoustic Wave (SAW) touch screens use sound waves instead of electricity. SAWs have three components: transmitting transducers, transmitting receivers, and reflectors. Together, these components produce a constant surface of acoustic waves. When a finger touches the screen, it absorbs the sound waves, which, consequently, never make it to their intended receivers. The device’s computer then uses the missing information to calculate the location of touch.
SAWs have no traditional layers, so they tend to have the best image quality and illumination of any touch screen. They have superior scratch resistance, but are susceptible to water and sold contaminants, which can trigger false “touches.”
Infrared touch screens are similar to SAWs; only they use infrared light (IR) instead of sound waves to detect disruptions.Infrared (IR) touch screens are like SAW screens; in that they contain no metallic layers. However, instead of producing ultrasonic sounds, IRs use emitters and receivers to create a grid of invisible infrared light. Once a finger or other object disrupts the flow of light beams, the sensors can locate the exact touch point. Those coordinates are then sent to the CPU for processing the command.
IR screens have superior screen clarity and light transmission. Plus, they offer excellent scratch resistance and multi-touch controls. Downsides include high cost and possible interference from direct sunlight, pooled water, and built-up dust and grime.
Today’s Wonder of the Day was inspired by Cohen. Cohen Wonders, “ How does touch screen work? ” Thanks for WONDERing with us, Cohen!
From mall kiosks to smartphones to tablet computers, touch screens are everywhere you look these days. As technology advances, keyboards and mice are quickly becoming a thing of the past. Why be burdened with cords when you can have what you want with just a touch?
Touch screens are electronic visual displays that allow a user to interact directly with what is displayed on the screen, rather than using a pointing device, such as a mouse. Touch screens are designed to respond to the touch of a finger, although an object — like a stylus — can also be used.
Touch screens are used in all sorts of modern electronic devices, including personal digital assistants (PDAs), satellite navigation systems and video games. Their popularity has surged recently, but the idea for the touch screen goes back several decades.
The idea for the touch screen was first developed by E.A. Johnson at the Royal Radar Establishment in England. His idea was first described in a short article published in 1965.
Given the many different types of devices that use touch screens, it's no surprise that there are several different types of touch screens. Each type of touch screen works a little differently from the others.
Resistive touch screen systems use two thin metallic layers separated by spacers. An electrical current runs through the two layers. When the screen is touched, the two layers make contact in the exact spot where the screen is touched. This contact creates a change in the electrical field, which a device's computer operating system can understand.
Capacitive touch screen systems feature a special layer that stores an electrical charge. When the screen is touched, some of the electrical charge is transferred to the user. This decreases the charge on the capacitive layer. The device's computer operating system can determine from this change in electrical charge where the screen was touched.
For a capacitive system to work, some of the electrical charge must be able to be transmitted to the user. This is why capacitive touch screens may not work properly if you wear gloves that block the transmission of the electrical charge.
Capacitive systems are newer and tend to be more popular than resistive systems, because they transmit more light and provide a clearer picture. Of course, capacitive systems also tend to be more expensive than resistive systems, too.
Surface acoustic wave touch screen systems use transducers and reflectors to measure changes in the reflection of ultrasonic waves caused when the screen is touched. These systems are the most advanced and offer the clearest picture possible. Unfortunately, they're also extremely expensive.
When touch screens first became popular, they could only sense one point of contact at a time. Technology has advanced greatly in recent years, though. Today, many touch screen devices feature multi-touch technology. This technology allows a touch screen device to interpret multiple points of contact simultaneously.