Call it an effort of the human mind or a miracle of the human heart. But all of this is happening with technology. We have reached an era in which everything that can be thought can also be put into practice. And that is also quite reasonable..!! Just move your hand or run your fingers over something and it works. Yes, I'm talking about gesture-based interactive technology.
Figure 1: Pictorial representation of Touch Screen technology
What is touchscreen technology?
Touchscreen technology is technology based on direct manipulation type gestures. Direct manipulation is the ability to manipulate the digital world within a screen without using command line commands. A device that works on touchscreen technology is called Touchscreen. A touchscreen is an electronic visual display capable of effectively 'detecting' and 'locating' a touch within its display area. It is sensitive to the touch of a human finger, hand, pointed fingernail, and passive objects like a pen. Users can simply move things on the screen, scroll, enlarge them, and more.
Saluting History..!!
The first touch screen was developed by EA Johnson at the Royal Radar Establishment, Malvern, United Kingdom, in the late 1960s. Evidently, the first touch screen was of the capacitive type; the one widely used in smartphones nowadays. In 1971 , a landmark touchscreen technology was developed by Dr. Sam Hurst, an instructor at the University of Kentucky Research Foundation. It was a touch sensor called 'Elograph'. Later, in 19 74, Hurst, in association with his company Elographics, created the first real touch screen with a transparent surface. In 1977, Elographics developed and patented resistive touchscreen technology, one of the most popular touchscreen technologies in use today.
Since then, touch screens are widely used in computers, user interactive machines, public kiosks, point-of-sale applications, game consoles, PDAs, smartphones, tablets, etc.
Types of touchscreen technology
Let's now take an engineer's look at this revolutionary technology. A touch screen is a two-dimensional sensing device made of 2 sheets of material separated by spacers. There are four main touchscreen technologies:
1) Resistive
two) Capacity
3) Surface acoustic wave
4) Infra-red
1. Resistive touchscreen technology
The resistive touch screen consists of a flexible top layer made of polyethylene (PET) and a rigid bottom layer made of glass. Both layers are coated with a conductive compound called indium tin oxide (ITO) and then spaced with spacers. While the monitor is operational, an electrical current flows between the two layers. When a tap is made, the flexible screen presses down and touches the bottom layer. A change in electrical current is therefore detected and the touch point coordinates are calculated by the controller and analyzed into readable signals for the operating system to react accordingly.
Figure 2: Graphical presentation explaining resistive touchscreen technology
Some of the popular devices that use resistive touchscreen are Nintendo DS, Nokia N97, HTC Touch Pro2, HTC Tattoo, Sony Ericsson Satio, etc.
These systems transmit only 75% of the monitor's light. Resistive touch screen is divided into 4, 5, 6, 7 and 8 wire resistive touch screen. Although the constructive design of all these modules is similar, there is a major distinction in each of their methods for determining touch coordinates.
The Four-Wire Resistive Touchscreen uses both layers to calculate touch axis information. Touch measurement on the 4 wire is a 2 step process. The x-coordinate of the contact point is calculated by creating a stress gradient across the flexible layer, and the y-coordinate is determined by creating a stress gradient across the bottom layer.
Pros and cons: Consequently, the 4-wire resistive touchscreen is less durable, not very accurate, and may vary with environmental changes. However, these negatives are only released with large touch screens. These are relatively cheap, easily available and consume little energy.
The 8-wire resistive touchscreen is simply a variation of the 4-wire with the addition of 4 sensor wires, two for each layer. Detection points help reduce environmental drift to increase system stability. 8-wire systems are used in sizes 10.4” and larger, where deviation can be significant.
The Five-Wire Resistive Touchscreen does not use the cover sheet (flexible layer) to determine the touch coordinate. All position sensing is employed on the stable glass layer. In this design, one wire goes into the cover sheet and four wires are deployed at the four corners of the bottom sheet. The cover sheet only acts as a voltage measuring probe. The touchscreen operation remains unharmed even with changes in the uniformity of the conductive coating on the cover.
Pros and cons: Highly durable, accurate and reliable. This technology involves complex electronic components and is expensive. However, it can be used in sizes up to 22”.
The six- and seven-wire resistive touchscreen is also a variant of the 5-wire and 4-wire technology, respectively. In 6-wire resistive touch screen, an extra grounding layer is added behind the glass plate, which improves system performance. While the seven-wire variant has two detection lines on the bottom plate. However, these technologies are just as prevalent as their counterparts.
The resistive touchscreen works well with almost all pen-like objects.
Type2: Capacitive
two. Capacitive touchscreen technology
Capacitive touchscreen technology is the most popular and durable touchscreen technology used around the world. It consists of a glass panel coated with a capacitive (conductive) material Indium Tin Oxide (ITO). Capacitive systems transmit almost 90% of the monitor's light. Some of the devices that use capacitive touchscreen are Motorola Xoom, Samsung Galaxy Tab, Samsung Galaxy SII, Apple iPad. There are several capacitive technologies available, as explained below.
Capacitive Surface Screens, in this technique only one side of the insulator is coated with a conductive layer. While the monitor is operational, a uniform electrostatic field is formed over the conductive layer. Whenever a human finger touches the screen, electrical charges are conducted over the uncoated layer, which results in the formation of a dynamic capacitor. The computer or controller then detects the position of the touch by measuring the change in capacitance at the four corners of the screen.
Pros and cons: The surface capacitive touchscreen is moderately durable and needs calibration during manufacturing. Since a conductive material is required to operate this screen, the passive stylus cannot be used for surface capacitive touch screens.
Figure 3: Schematic presentation of capacitive touchscreen technology
In projected capacitive touchscreen technology, the ITO conductive layer is etched to form a grid of multiple horizontal and vertical electrodes. It involves detection along the X and Y axes using a clearly engraved ITO pattern.
Figure 4: Detection of ITO conductive layer along the X and Y axes
The projective screen contains a sensor at each intersection of the row and column, thus increasing the accuracy of the system. There are two types of projected capacitive touchscreen: Mutual Capacitance and Self Capacitance
Type3: Acoustic Surface
3. Surface Acoustic Wave Touchscreen Technology
Surface Acoustic Wave Touchscreen technology contains two transducers (transmit and receive) placed along the X-axis and Y-axis of the monitor glass plate along with some reflectors. The waves propagate through the glass and are reflected back to the sensors. When the screen is touched, the waves are absorbed and a touch is detected at that point. These reflectors reflect all electrical signals sent from one transducer to another. This technology offers excellent performance and image clarity.
Pros and cons: 100% clarity is obtained as there are no metallic layers present on the screen and can be operated using passive devices such as a pen, glove or fingernail. The screen can become contaminated with too much exposure to dirt and oil that can hinder its proper functioning.
Figure 5: Surface Acoustic Wave Touchscreen Technology
Type4: Infrared
4. Infrared touchscreen technology
In infrared touchscreen technology, a series of X and Y axes are equipped with pairs of infrared LEDs and photodetectors. The photodetectors detect any change in the light pattern emitted by the LEDs whenever the user touches the monitor/screen.
Figure 6: Graphical presentation of infrared touchscreen technology
Assets marked with a star..!!
Potential touchscreen technology for beginners has many advantages over the conventional QWERTY keyboard and monitor. It is very flexible unlike its physical counterparts, as digital displays can be configured at any time at the user's discretion according to the features. The touchscreen allows users to customize the interface, for example by changing the language and size. By adjusting the size of the keyboard, the user can utilize the free area for display and other uses. With the increasingly smaller size of computers and tablets these days, a touch screen is an added advantage. Multiple functions must be performed on a small screen, the touch screen allows switching to a function as per the user's desire. For example, the virtual keyboard which is a touch screen application is displayed on the screen only when the user allows it.
However, there is also the other side of the coin where there are some functionalities that cannot be performed using a normal touchscreen, such as cut and paste, right-click menu options, and drop-down menus.
Plural Technology
Plural Touch Technology..!!
Plural touch technology or Multitouch is a variant of touchscreen technology that can detect two or more touches on the display area at the same time. Some of the common features that require multi-touch interface are zooming in, zooming out, rotating objects, scrolling through a document, virtual keyboard, etc. Multi-touch app technology is found in smartphones like iPhone, Samsung Galaxy, Nokia N8, Nexus S, Microsoft Touchtable, Apple iPad and more.
Apple iPhone: 'Multi-touch' is now a registered trademark of Apple, who rightly proved this with the most successful first multi-touch device ever; The iPhone. The first iPhone was launched on January 9, 2007. The iPhone is nothing short of a revolution in the touch screen industry with its maestro features and apps. It uses mutual capacitance technology as a touch screen. The capacitive touchscreen can only be operated with a bare finger or with multiple fingers for multi-touch.
Microsoft Surface: is a multi-touch product from Microsoft that allows multiple users to manipulate digital content through surface computing. The main feature of this product is the Surface interface: direct interaction, multi-touch contact, object recognition and multi-user experience. It is not based on or limited by conventional touch technology. The surface uses Frustrated Total Internal Reflection and projectors below for its display operation. In fact, it is a milestone in the multitouch scene.