Rapid technological advancements which started during the industrial revolution are now regarded as the most potent instrument in environmental developments. In fact, the invention of computer paved the way to the emergence of other electronic gadgets which are used by today’s generation. As it has been inculcated in our mind, computers really help us accomplish variety of things in least possible time. It is apparent that all societal and environmental sectors use computers in almost all of their transactions since according to an article; computers are ubiquitous and that they find a wide variety of applications in different spheres of life (1).
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In the fast moving life of the modern world of today, another advancement has been introduced which according to the Wikipedia, plays a prominent role in the design of digital appliances such as the personal digital assistant (PDA), satellite navigation devices, mobile phones, and video games. This advancement is what we know, the Touchscreen technology. Mary Bellis, the author of the article Touchscreen, stated that touchscreen is one of the easiest to use and most intuitive of all interfaces, making it the interface of choice for a wide variety of applications. This technology is defined as an electronic visual display that can detect the presence and location of a touch within the display area.
Touchscreen allows the user to interact directly to the interface displayed over the monitor, rather than indirectly with a cursor controlled by a mouse or touchpad. Such interface navigation does not require any intermediate device that would need to be held in the hand. This technology is associated with a variety of touch detections which are considered as the core of its emergence such as the resistive, capacitive, surface acoustic wave, infrared matrix and others. Hence, this paper mainly focuses on these touch sensors and discusses how each sensor contribute to the implementation of this advancement.
Touchscreen Technology History
Touch screens started making its account by mid-1960s by the researches of IBM at Ottawa Canada and the University of Illinois. In 1971, Elographics,Inc was founded by ten stockholders headed by Dr. Samuel Hurst, which aimed in producing a Graphical Data Digitizers to be used in research and industrial applications. It was then with this works of Hurst that started the development of the first “touch sensor” called Elograph.
The continued evolution of the PLATO computers starting from the 1970’s brought Touch Screens to the public. With the operation of PLATO III, its developers decided to scale up the system. By 1972, the new PLATO IV entered selected grade-school classrooms. This computer’s display included a 16-by-16 grid infrared touch panel allowing students to answer questions by touching anywhere on the screen.
In 1974, the first true touch screen incorporating a transparent surface came on the scene in extend to Hurst’s Elograph. In 1977, Elographics developed and patented five-wire resistive technology, the most popular touch screen technology in use today called “AccuTouch”.
The emergence of Tactile Array Sensors amounted into the beginning of multi-touch. This technology was designed for robotics in detecting shape, orientation and others. However, it was the Flexible Machine Interface, in 1982, that was considered the first multi-touch system designed for human input to a computer system. It was then developed by Nimish Metha as a part of his part of his MSc thesis at the University of Toronto. This allowed multi touch input picture drawing and many others with simple image processing.
By 1983, what was considered to be the first commercial touch screen computer was invented by Hewlett Packard. He called this HP-150 which was Intel 8088-based non-IBM compatible MS-DOS computer. One of its main interesting characteristic is its “touch sensitive screen”. Actually, it’s not a true touch screen, however has a lot of infra red transmitters and receivers around the screen that detect the position of anything on the screen: a finger of course but a pencil too.
A remarkable feature of touch screens that is evident with our present technology is being able to shift forward or backward from one image to another by a touch of the image and quickly sliding the finger left or right on the screen. This technique was then similar with what was called the Portfolio Wall in 1999. This product was a digital cork-board wherein images could be presented as a group or individually. It allows images to be sorted, interpreted and exhibited in sequence. A user can instigate an event depending on the finger’s movement direction. This finger gestures is just an example of the technique called radial menus. Radial menus, as quoted from Bill Buxton’s A Touching Story: A Personal Perspective on the History of Touch Interfaces Past and Future, “is a class of interaction where the reaction to an action is a function of both where you touched and the direction that you move after that touch”. It is then this technique which is used by some of our today’s touch screen technology such as in mobile phones and many other devices.
These were just some of the important innovations of touch screen technology and thus, paved the way for its continued advancements. What has then been started years ago has prompted every complex developments of the present, extending its influence to the future.
Common Components of Touch Screen
One component of a touch screen technology is a clear glass panel with a touch responsive and pressure sensitive surface which is known as the touch sensor. This is set over a display screen so that it will cover the area viewable to the user. In this manner, the maximum area of the screen would be able to sense a touch and deliver output appropriately.
Touch sensor generally has a constant signal voltage or electrical current across the display screen. When a portion on the screen is touch, the signal passing through it changes. This mechanism determines touch on the screen and the most basic one.
The controller serves as the communication link between the sensor and the device’s processor. It is a small computer card that takes data input from the sensor and converts it to information the computer system could understand. For integrated monitors, it is usually installed inside while for external touch overlays, it is housed in a plastic case.
The touch screen driver is a software update for the touchscreen device that allows the gadget and the touch screen to work together. It tells the operating system of the computer on how to interpret the touch event information that is send from the controller. Because of this, it is possible for touchscreen to be utilized with the existing software and develop new application without the need for touchscreen specific programming. Yet, there is still some equipment such as thin client terminals, DVD players and specialized computer systems that do not use software drivers or they already have a built-in one.
Figure 1: Common components of touch screen mechanism
Types of Touchscreen Technologies
In the market today, manufacturers use different mechanisms to detect touch. These touchscreen technologies that are available now are:
The resistive system is one of the prevalent systems used in detecting a person’s touch in the world of touch screen devices. In this, the resistive panel is consists of several layers in which the two opposing ones are electrically conductive and metallic. Insulating dots which are transparent and very small serve as the space of the two essential layers. When a finger or a stylus touches the screen specifically on the conductive outer surface of it, the primary layer flexes towards the inner layers making the opposed layers to link up. The pressure of the outer layer to the inner ones lets the electric current runs through producing outputs. These outputs cause the environment of electric field to change which registers a touch event. Marking up the said change followed by the determining of the coordinates of the touch location are executed. If the coordinates are already calculated, then a registered touch will be translated by a controller and be processed.
Figure 2: Resistive system mechanism to sense the touch point.
The capacitive system is also a common system used in touch screen technologies like of the resistive system. In this, the capacitive touch screen has an insulating glass panel transparently coated with a conductive material like indium tin oxide. This panel also consists a two-layer grid of electrodes and an integrated circuit(IC) in the opposed side of the panel that are being connected. The upper layer and the lower layer include vertical electrode strips and a horizontal electrode strips for the latter. Both these two said electrodes are used by the IC in calculating their mutual capacitance when a finger touches the screen. Not by the pressure of the outer surface but because a change of the electrostatic field has occurred for the fact that a finger has a dielectric properties. As the screen detects a touch, some of the charge is diverted to the person who did the event that makes a potential difference on the screen letting the controller to distinguish the location of the touch. As the location is determined, the system will translate the touch event to the desired output of the user.
Figure 3: Capacitive Touch-screen technology way of detecting touch.
Surface Acoustic Wave (SAW)
This type of technology came in existence in the late 90’s and uses sound waves to detect the position you have pressed. The screen used in a Surface-Wave touch technology has a glass overlay with transmitting and receiving piezoelectric transducers for both X and Y axes designed for sending and reflecting back sound waves.
Ultrasonic sound waves which too high pitched for human to hear, pass over the touchscreen panel and are generated at the edges of the screen and reflected back and forth. Whenever the panel is touched, a portion of the wave is absorbed. This sound beam interruption registers the position of the touch event and sends information to the controller for processing. The user’s finger absorbs some of the acoustic wave and the microchip controller figures out the exact location of where the event occurred.
The pure glass construction of Surface-Wave touch technologies provides superior image clarity, resolution and higher light transmission. However, since it cannot be sealed, it can easily be affected by contaminants and water disallowing to be used in EX-zones especially in oil industry. “Dead” spots would then be created if these technologies would be exposed to contaminants for these will absorb their acoustic waves.
Figure 4: Surface Acoustic Waves technology processes.
Infrared touchscreen technology is based on “legacy” technology and is increasingly replaced by Capacitive and Resistive touch systems. This touchscreen technology relies on an array of Infrared (IR) light emitting diodes (LED) on two adjacent bezel edges of a display which also contains phototransistors, each mounted on two opposite sides to create a grid of invisible light. When the display screen is touched, the light beams would then be obstructed causing the decrease in the amount of light in a corresponding photosensor. The measured photosensor outputs would then be the bases of the x and y coordinate of the touch event.
Infrared touchscreens are usually used in medical and manufacturing areas because of its property to be sealed and covered with hard or soft materials. Another desirable feature of touchscreen is the digital nature of the sensor it uses unlike other touchscreen systems that rely on analog-processing system to sense and locate touch events making it more accurate and precise. However, the spread of this technology has been hindered by two factors: the high cost of manufacturing bezel and the issue of performance under bright ambient light. In addition, the seating of its touch frame is slightly above the screen causing its susceptibility in early activation before the actual touch in the surface.
Figure 5: Infrared system process .
Projected Capacitive Touch (PCT) technology is a capacitive technology that uses embedded microfine wires within a glass laminate composite. Each wire has a diameter of about one third of a human hair making it almost invisible to human eye when projected in a powered display. It permits more accurate and flexible operation by etching the conductive layer. This type of technology produce X-Y array by etching a single layer to form a grid pattern of electrodes, or by etching two separate, perpendicular layers of conductive material with parallel lines or tracks to form the grid. When voltage is applied to the array, grid of capacitors would then be established. Furthermore, oscillation frequency is produced by each wire which is connected to an integrated controller board.
When part of the screen is touched, change of electrostatic field occurs which results in a measurable oscillation frequency change in the wires surrounding the touch point. The integrated controller will be responsible of calculating the new capacitive values then it will be transmitted to a host controller. The sensor contact point will be translated to an absolute screen position by software.
Since PCT uses grids, it has a higher resolution compared to the resistive technology and it allows multi-operation. Even if without direct contact, this can still operate effectively because of its resolution; thus, permitting conducting layers to be coated with insulating materials and screen protectors, or behind weather and vandal-proof glass.
Figure 6: PCT technology mechanism.
Optical imaging is another type of system used in touch screen devices. In this new development, the screen mostly in the corners consists of two or more optical sensors. In the other side of the screen wherein the sensors field of view is distinguish, infrared backlights are being situated. This is done in order to cast a similar field of infrared light above the glass surface. When the user touches the screen using a finger, pen, stylus or other things, the touch shows as a shadow. This event lets the pair of optical sensors to locate the point of that touch event. Not just they simply locate but they measure the size of the object that does the said event. In addition to that, the user can apply a single touch, a dual touch or multi-touch because of the reason that the touch event is already registered before the physical touch on the screen’s surface. One good thing about this optical imaging sensor is that any scratches on the screen will not disturb the touch-detecting operation because the coated surface has nothing to do with the touch screen panel.
Figure 7: Optical imaging touch screen technology.
Strain-gauge is a device used to measure the strain that occurs in an object. It is consists of a foil of resistive characteristics, which is safely mounted on backing material. The foil’s resistance alters consequently when a known amount of stress is subjected to the resistive foil.
Thus, this device was used to measure the deflection of touch event in a touch screen. This pressure sensor is placed at the four corners of the display device. A touch in the display event would be converted to force in the platform’s base corners. The ratio of the four readings would then specify the touch point coordinate which is calculated by the platform’s controller. This controller detects static forces such as gravity and repetitive force like that of vibration.
This type of technology does not utilize panel construction, enhancing the visibility of display. Typically, this is commonly used in public places such as ATM machines and ticket machines due to its resistance to damage.
Dispersive Signal Technology (DST)
Dispersive Signal Technology is said to be developed for interactive signage application and was introduced in around 2002. It also sets new large-format touch standard for fast, accurate repeatable touch.
This type technology of uses an extra layer of sensor enabled specially-designed glass, which responds for finger and pen touches. DST determines the touch point by calculating the location the “shock” or mechanical energy (bending waves) the motion creates within a glass substrate. The distance from the sensor determines the extent the signal is dispersed. Namely, the further away the “touch point” is from the sensor, the more signal is smeared. This innovation utilizes algorithms which can interpret these chaotic series of waves and the precise location of the touch location providing a highly accurate and sensitive solution.
Figure 8: DST mechanism.
Acoustic Pulse Recognition (APR)
This system uses a new and unique way of sensing touches on a display. It turns mechanical energy of a touch or the vibration into an electronic signal by means of more than two piezoelectric transducers placed at some positions in the display screen. The “touch point” is measured by a screen algorithm and it bases the signal the transducers transmit. This process is similar to the triangulation used in GPS.
The touch screen using this type of type technology is made up of ordinary glass enhancing its durability and optical clarity. Even if exposed with contaminants like dust and has screen scratches, it still works properly. It is also suited to displays that are physically larger.
Advantages and Disadvantages
Although touch screen has become the biggest innovation with regards to technology, mind its disadvantages. Let us consider some of the strengths and weaknesses of this latest technological advance.
Touch screen gadgets usually have simple user interfaces, which are more intuitive.
Touch screen devices have fewer buttons which means no more buttons falling off.
It is so direct. Using your fingers or a pen is very hands on, and manipulating objects on the screen is very similar to manipulating them in the manual world.
Intuitively easy to use.
Without a keypad or mouse attached, touch screen devices provide a much larger display. It also saves desk space since its screen acts as both input and output.
Functions for touch screen devices are novice oriented.
When you particularly touch the screen to run a specific application, it displays and easily adapts to the current application. No other unnecessary buttons are displayed.
At a single touch or two, it displays a different interface which suits the user’s need.
Mostly touch screen devices means screen cannot be read too well in direct sunlight.
Touch screen devices usually have no additional keys such as end keys. For instance, when your device or an application crashes, you are not able to return to the main menu since the screen becomes unresponsive.
Touch screens are not super precise because it cannot immediately and accurately detect the position of a touch.
The screen can get dirty easily from finger prints and sweat.
Mostly touch screen devices such as laptops and cell phones are fragile.
Have to look to touch or requires full attention when making use of it.
Touch screen devices have mostly low battery life.
Nevertheless, touch screen technology would continue to improve and broaden the range of applications it could serve despite the disadvantages stated. Technological innovations, specifically the touchscreen technology apparently dominates electronic interfaces considering the convenience and ease of use it provides to electronic-literate users. It is expected that over a span of time, aided by the technology discussed, more sophisticated technological gadgets would soon emerge. Perhaps, when this time arrives, such gadgets would be of high quality, more durable and less expensive.
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Based on our research, we are able to come up with ideas to what future touch screen technology will be like. Since multi touch screen has been prevalent nowadays, we think of touch screen technology which is combined with biometrics. In other words, the device screen display would not only be able to detect touch but also recognizes if that touch came from a valid source. This may improve security and protection of data.
Moreover, observing the trends of touch screens’ development, we believe that in the near future the life span of this technology would then be improved. From being insusceptible to contaminants and being durable, to those touch screens that are waterproof and those that will last in a freezing point temperature.
Since this gadget had also become thinner and thinner, we believe that time will come that it will become flexible or can be bent making it more portable. To increase its durability, we think of touch screen that when drop at a particular height would only bounce back and can still function efficiently.
We also want to promote “Green Technology”; thus, we imagined of a touch screen components which are recyclable or still useful in making the same product. In this way, they will not be thrown anywhere lessening solid waste pollution.
Lastly, we imagined of a touch screen which is holographic in nature. In other words, what is needed is to project three-dimensional image or a life-like image of a display screen. Though cannot be touched, technology would then make a way to give a somehow tangible image.
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