What does a touchscreen consist of? Features of different types of touchscreens

Before considering a capacitive or resistive screen, you need to decide what it is touch technology at all. Everything is clear here: this is the screen that determines the coordinates of the press. In scientific terms, this refers to a method of controlling the interface with which the user can click directly on the place of interest. At the moment, there are several methods for implementing touch screens. It is worth considering each separately.

Resistive technology

To decide which type of screen, capacitive or resistive, is best for you, you need to consider them. The second option involves using a certain production technology. At the bottom there is a glass panel, on top of which there is a transparent flexible membrane. There is a conductive coating on the panel and membrane, that is, resistive. When you press the screen, a short circuit occurs at a certain point. If you know the voltage on the electrodes on one side and measure it on the membrane, you can track one coordinate. Two coordinates will require turning off one group of electrodes to turn on another. It's all in automatic mode is done by the microprocessor as soon as the voltage on the membrane changes. Resistive screens do not allow multi-touch.

Features of resistive technology

Like any other type of implemented device, there are certain features that are positive or negative depending on the situation. The advantages are usually low-cost production, as well as the ability to press with anything, since you only need to push the membrane. Positioning accuracy is increased through the use of styluses.

Negative points

The main disadvantages include the low degree of light transmission, high speed the appearance of scratches on the surface, the ability to click on one point no more than 35 million times, the inability to implement multi-touch. If you can't decide whether to choose a capacitive or resistive screen, then it is also important to note that it is impossible to use gestures such as sliding, since you need to press your finger on the screen and drag it without releasing it. In devices with such controls, it is better to use software that requires minimal use of “swipe” gestures.

Understanding the features of this technology, it is worth noting that it can be implemented in several ways that have certain differences. A capacitive touchscreen can be simply capacitive or projected capacitive. The first option involves the use of certain elements. A transparent resistive material, such as an alloy of tin oxide or indium, is placed on top of the glass panel. Electrodes are placed in the corners, which supply a small AC voltage to the conductive layer. If the screen is touched by a conductive object, a leakage occurs, and the closer this object is to the electrode, the lower the screen resistance, that is, the current strength increases noticeably. And this is all called a capacitive screen, since alternating current is conducted by an object with a larger capacitance. More often we're talking about about the finger.

Features of capacitive screens

Like other types of technologies, in this case We are talking about a combination of advantages and disadvantages. The advantages over others include high light transmittance, significant click life, simplicity and ease of operation using the “flipping” method. There are also disadvantages here: you only need to use your fingers or specialized styluses. A regular capacitive screen does not support multi-touch technology. There are often accidental clicks. For example, the system can recognize a gesture as “scrolling” even when it is not intended, since it is difficult to keep the finger strictly in one place after pressing.

Projected capacitive touch screen

In this case, the device differs quite greatly from the previous ones. The inner side of the screen is a grid of electrodes. If an object of greater capacitance touches the electrode, a capacitor is formed with a constant capacitance. Such screens are used outdoors, as they allow the installation of glass with a thickness of up to 18 mm, which not only produces the hardest possible surface, but also ensures vandal resistance.

Features of projected capacitive sensors

In this case, as in all others, there are certain advantages and disadvantages that you should be aware of. The advantages include the ability to implement multi-touch, respond to pressure while wearing a glove, high degree light transmission, as well as the durability of the screen itself. Such screens are able to respond to the approach of fingers without actually pressing. The threshold for when a touch completes occurs is usually software configurable. The extreme point is usually the screen itself, since pushing through it is completely useless.

If we consider a projective-capacitive screen, it also has certain disadvantages, which are usually called complex and rather expensive electronics, the inability to use a regular stylus, and the likelihood of accidental clicks.

Multi-touch technology

It is impossible to determine the appropriate type of touch screen, capacitive or resistive, without addressing the issue regarding the implementation of this technology. Multitouch is the ability to make multiple touches. This implementation involves tracking the coordinates of several clicks simultaneously. If such technology is implemented in a smartphone or tablet, then it can be used to imitate playing a musical instrument, for example, a guitar. This needs to be looked into in more detail.

You can take a regular capacitive or resistive screen. If you press first, for example, on the left top corner, and then, without lifting your finger, press the lower right with the other, then the electronics will determine the center of the screen as coordinates, that is, the middle of the segment between these pair of touches. This will be visible if you run special application, which tracks the coordinates of the click. However, the question arises: how is image scaling implemented if only one click is recognized anyway?

Everything is simple here. This is the most common software trick. You pressed the capacitive screen - the electronics detected this. This will be point "A". Now, without releasing your finger, you press in another place, which will be point “B”, it turns out that at this moment the point of pressure moved instantly to the side, forming “C”. It was at this moment, when there was no actual release of the finger, but the pressing point instantly moved, that is processed in software as a multi-touch. Further, if point “C” becomes closer to “A”, then the movement of the fingers is determined, that is, in the case of an image, the picture must be reduced, and vice versa. One more point: if point “C” describes an arc around one of the points, then the program defines this as the rotation of one finger around the other, which necessitates rotating the picture in the appropriate direction.

Using resistive and capacitive screens

Professional developers traditionally use the first type, since it allows you to control any object under different conditions. weather conditions. Resistive technology uses a larger number of sensors per square centimeter compared to capacitive technology, so the display can display tiny icons that can be pressed with a needle. For example, the operating system Windows Mobile was developed taking into account this feature, so it works well with resistive screens. Such displays are almost insensitive to random presses. However, many developers are now aiming to create applications that target capacitive touch screens. This is already becoming a problem for devices made using resistive technology.

Degree of protection

It is important to understand that for tablet computers and communicators, the display is the most vulnerable part. A capacitive screen is a more preferable option in terms of reliability. Its performance in any conditions is noticeably higher, and resistive models may fail, for example, if you carry them downwards with glass. Capacitive screen is a fail-safe option. Even if it is broken, it will continue to perform its functions. If you are deciding whether to choose a capacitive or resistive screen, it is worth noting that in field conditions the first will be the best option.

conclusions

To summarize, it can be noted that both display implementation options have their advantages and disadvantages. While a capacitive screen is a whole set of possibilities, a resistive screen is focused on use in certain situations. Usually it all depends on the interface used in the gadget. easy to use, its pressing area is noticeably smaller than that of a finger, however, with good responsiveness of the surface, it is convenient to do without this device. The constant improvement of resistive displays has led to the emergence of models that are quite hard, that is, resistant to scratches, but also responsive. Such options have become very convenient to use.

The need to use a special stylus for capacitive screens sometimes causes considerable inconvenience, since it usually does not come with the device. And resistive technology involves both accompaniment with a special device and the ability to press with any hard object. One of the reasons many people choose a capacitive touchscreen is multi-touch, however it is worth noting that most often this is a software implementation, as already described, and with the right approach it can be applied to a resistive one. Projected capacitive technology has not yet become as accessible as we would like.

A touch screen is a device for input and output of information through a touch- and gesture-sensitive display. As you know, screens modern devices not only display an image, but also allow you to interact with the device. Initially, familiar buttons were used for such interaction, then the equally famous “mouse” manipulator appeared, which significantly simplified the manipulation of information on the computer display. However, the “mouse” requires a horizontal surface to work and mobile devices not very suitable. This is where an addition to the regular screen comes to the rescue - Touch Screen, which is also known as Touch Panel, touch panel, touch film. That is, in fact, the touch element is not a screen - it is additional device, installed on top of the display from the outside, protecting it and serving to enter the coordinates of touching the screen with a finger or other object.

Usage

Today, touch screens are widely used in mobile electronic devices. Initially, the touchscreen was used in the design of pocket personal computers(PDA, PDA), now the championship is held by communicators, mobile phones, players and even photo and video cameras. However, finger control technology virtual buttons on the screen turned out to be so convenient that almost all payment terminals, many modern ATMs, electronic information kiosks and other devices used in in public places.

Laptop with touch screen

It should also be noted that laptops, some models of which are equipped with a rotating touch screen, which gives the mobile computer not only wider functionality, but also greater flexibility in controlling it on the street and in weight.

Unfortunately, there are not many similar laptop models, popularly called “transformers,” but they do exist.

In general, touch screen technology can be described as the most convenient when you need instant access to control the device without prior preparation and with amazing interactivity: controls can change each other depending on the activated function. Anyone who has ever worked with touch device, the above is perfectly understandable.

Types of touch screens

There are several types of touch panels known today. Naturally, each of them has its own advantages and disadvantages. Let us highlight four main structures:

• Resistive
• Capacitive
• Projected capacitive

In addition to the above screens, matrix screens and infrared, but due to their low accuracy, their scope of application is extremely limited.

Resistive

Resistive touch panels are among the most simple devices. At its core, such a panel consists of a conductive substrate and a plastic membrane that have a certain resistance. When you press the membrane, it closes with the substrate, and the control electronics determines the resulting resistance between the edges of the substrate and the membrane, calculating the coordinates of the point of pressure.

The advantage of a resistive screen is its low cost and simplicity of design. They have excellent resistance to stains. The main advantage of resistive technology is sensitivity to any touch: you can work with your hand (including gloves), a stylus (pen) and any other hard, blunt object (for example, the upper end of a ballpoint pen or the corner of a plastic card). However, there are also quite serious disadvantages: resistive screens sensitive to mechanical damage, such a screen is easy to scratch, so a special protective film, protecting the screen. In addition, resistive panels do not work very well at low temperatures, and also have low transparency - they transmit no more than 85% of the display's luminous flux.

Using a touch pen

Application

• Communicators
• Cell Phones
• POS terminals
• Tablet PC
• Industry (control devices)
• Medical equipment

Communicator

Capacitive

Capacitive touchscreen technology is based on the principle that a large capacitive object (in this case a person) is able to conduct electricity. The essence of capacitive technology is to apply an electrically conductive layer to the glass, while a weak alternating current is supplied to each of the four corners of the screen. If you touch the screen with a grounded object of large capacity (finger), current will leak. The closer the point of contact (and therefore the leakage) is to the electrodes in the corners of the screen, the greater the strength of the leakage current, which is recorded by the control electronics, which calculates the coordinates of the point of contact.

Capacitive screens are very reliable and durable, their service life is hundreds of millions of clicks, they perfectly resist pollution, but only those that do not conduct electric current. Compared to resistive ones, they are more transparent. However, the disadvantages are still the possibility of damage to the electrically conductive coating and insensitivity to touch with non-conductive objects, even with gloved hands.

Information kiosk

Application

• In secured premises
• Information kiosks
• Some ATMs

Projected capacitive

Projective-capacitive screens are based on measuring the capacitance of a capacitor formed between the human body and a transparent electrode on the surface of the glass, which in this case is a dielectric. Due to the fact that the electrodes are applied to the inner surface of the screen, such a screen is extremely resistant to mechanical damage, and taking into account the possibility of using thick glass, projective capacitive screens can be used in public places and on the street without any special restrictions. In addition, this type of screen recognizes pressing with a gloved finger.

Payment terminal

These screens are quite sensitive and distinguish between finger and conductive pen presses, and some models can recognize multiple presses (multi-touch). Features of a projective capacitive screen are high transparency, durability, and immunity to most contaminants. The disadvantage of such a screen is its not very high accuracy, as well as the complexity of the electronics that process the coordinates of the press.

Application

• Electronic kiosks on the streets
• Payment terminals
• ATMs
• Laptop touchpads
• iPhone

With determination of surface acoustic waves

The essence of the operation of the touch panel with the determination of surface acoustic waves is the presence of ultrasonic vibrations in the thickness of the screen. When you touch the vibrating glass, the waves are absorbed, and the point of contact is recorded by the screen sensors. The advantages of the technology include high reliability and touch recognition (unlike capacitive screens). The disadvantages are poor protection from factors environment, therefore, screens with surface acoustic waves cannot be used outdoors, and in addition, such screens are afraid of any contamination that blocks their operation. Rarely used.

Other, rare types of touch screens

• Optical screens. The glass is illuminated with infrared light; as a result of touching such glass, light scatters, which is detected by a sensor.
• Induction screens. Inside the screen there is a coil and a grid of sensitive wires that respond to touch. active pen, powered by electromagnetic resonance. It is logical that such screens respond to touches only with a special pen. Used in expensive graphics tablets.
• Strain gauges – react to screen deformation. Such screens have low accuracy, but are very durable.
• The infrared ray grid is one of the very first technologies that allows you to recognize touches on the screen. The grid consists of many light emitters and receivers located on the sides of the screen. It reacts to the blocking of the corresponding rays by objects, on the basis of which it determines the coordinates of the press.

• Move two fingers together – zoom out the image (text)
• Spread two fingers to the sides – increase (Zoom)
• Movement of several fingers at the same time - scrolling text, pages in the browser
• Rotate with two fingers on the screen – rotate the image (screen)

About the benefits and disadvantages of touch screens

Touch screens have been around for a long time in handheld devices. There are several reasons for this:

• Possibility to do minimal amount governing bodies
• Simplicity of the graphical interface
• Ease of control
• Ease of access to device functions
• Expanding multimedia capabilities

However, there are more than enough disadvantages:

• Lack of haptic feedback
• Frequent need to use a pen (stylus)
• Possibility of screen damage
• The appearance of fingerprints and other dirt on the screen
• Higher energy consumption

As a result, it is not always possible to completely get rid of the keyboard, because it is much more convenient to type text using familiar keys. But the touch screen is more interactive, thanks to faster access to menu items and settings of modern gadgets.

We hope this material will help you when choosing a touch screen device.

Discuss on the forum

Today, no one can be surprised by a phone with a touch screen. Manual controls have become fashionable, but few people think about what happens when you touch the display. I'll cover how the most common types of touch screens work. Convenience and productivity of working with digital technology depend primarily on the information input devices used, with the help of which a person controls the equipment and downloads data. The most widespread and universal tool is a keyboard that is currently widespread. However, it is not always convenient to use it. For example, dimensions mobile phones do not allow you to install large keys, as a result of which the speed of information entry is reduced. This problem was solved through the use of touch screens. In just a few years, they made a real revolution in the market and began to be implemented everywhere - from mobile phones and e-books to monitors and printers.

The beginning of the sensory boom

Buying new smartphone, the body of which does not have a single button or joystick, you are unlikely to think about how you will control it. From the user's point of view, there is nothing complicated in this: just touch the icon on the screen with your finger, which will lead to some action - opening a window for entering a phone number, SMS or address book. Meanwhile, 20 years ago one could only dream of such opportunities.

The touch screen was invented in the USA in the second half of the 60s of the last century, but until the early 90s it was used mainly in medical and industrial equipment to replace traditional input devices, the use of which is fraught with difficulties under certain operating conditions. As the size of computers decreased and PDAs appeared, the question arose about improving their control systems. In 1998, the first handheld with a touch screen and an input and handwriting recognition system appeared Apple Newton MessagePad, and soon communicators with touchscreens.

In 2006, almost everyone large manufacturers began producing smartphones with touch screens, and after the appearance Apple iPhone in 2007, a real touch boom began - displays of this type appeared in printers, e-readers, various types of computers, etc. What happens when you touch a touch screen, and how does the device “know” where exactly you pressed?

Working principle of resistive touch screen

Over the 40-year history of touch screens, several types of these input devices have been developed, based on different physical principles that are used to determine the location of the touch. Currently, two types of displays are most widespread - resistive and capacitive. In addition, there are screens that can register multiple clicks simultaneously ( Multitouch) or just one.

Screens made using resistive technology consist of two main parts - a flexible upper layer and a rigid lower layer. Various plastic or polyester films can be used as the first, and the second is made of glass. On the inner sides of both surfaces layers of a flexible membrane and resistive (possessing electrical resistance) material that conducts electric current. The space between them is filled with a dielectric.

At the edges of each layer there are thin metal plates - electrodes. In the rear layer with resistive material they are located vertically, and in the front layer - horizontally. In the first case, they are served constant pressure, and an electric current flows from one electrode to another. In this case, a voltage drop occurs proportional to the length of the screen section.

When you touch the touch screen, the front layer bends and interacts with the back layer, which allows the controller to determine the voltage on it and calculate the coordinates using it touch points horizontally (X axis). To reduce the influence of the resistance of the front resistive layer, the electrodes located in it are grounded. Then the reverse operation is performed: voltage is applied to the electrodes of the front layer, and those located in the rear layer are grounded - this is how it is possible to calculate the vertical coordinate of the touching point (Y axis). This is the operating principle of a four-wire (named after the number of electrodes) resistive touch screen.

In addition to four-wire ones, there are also five- and eight-wire touch screens. The latter have a similar operating principle, but higher positioning accuracy.

The operating principle and design of five-wire resistive touch screens are somewhat different from those described above. The front resistive coating layer is replaced by a conductive layer and is used solely for reading the voltage value on the rear resistive layer. It has four electrodes built into it at the corners of the screen, the fifth electrode is the output of the front conductive layer. Initially, all four electrodes of the rear layer are energized, and on the front layer it is zero. As soon as such a touch screen is touched, the top and bottom layers are connected at a certain point, and the controller senses the change in voltage on the front layer. This is how it detects that the screen has been touched. Next, the two electrodes in the back layer are grounded, the X-axis coordinate of the touch point is calculated, and then the other two electrodes are grounded, and the Y-axis coordinate of the touch point is calculated.

Working principle of capacitive touch screen

The operating principle of capacitive touch screens is based on the ability of the human body to conduct electrical current, which indicates the presence of electrical capacitance. In the simplest case, such a screen consists of a durable glass substrate on which a layer of resistive material is applied. Four electrodes are placed at its corners. The resistive material is covered with a conductive film on top.

A small alternating voltage is applied to all four electrodes. The moment a person touches the screen electric charge flows over the skin onto the body, generating an electric current. Its value is proportional to the distance from the electrode (panel corner) to the point of contact. The controller measures the current strength across all four electrodes and, based on these values, calculates the coordinates of the touch point.

The positioning accuracy of capacitive screens is almost the same as that of resistive screens. At the same time, they transmit more light (up to 90%) emitted by the display device. And the absence of elements subject to deformation makes them more reliable: the capacitive screen can withstand more than 200 million clicks at one point and can operate at low temperatures (down to -15 ° C). However, the front conductive coating used for position determination is sensitive to moisture, mechanical damage, and conductive contaminants. Capacitive screens They are triggered only when they are touched by a conductive object (with a hand without gloves or a special stylus). Screens of this type made using classical technology are also not capable of tracking multiple clicks at the same time.

The projected capacitive touch screen, which is used in iPhone phones and similar devices. It has a more complex structure compared to conventional capacitive screens. Two layers of electrodes are applied to a glass substrate, separated by a dielectric and forming a lattice (the electrodes in the lower layer are located vertically, and in the upper layer - horizontally). The grid of electrodes together with the human body forms a capacitor. At the point of contact with the finger, a change in its capacitance occurs, the controller detects this change, determines at which intersection of the electrodes it occurred, and calculates the coordinate of the point of contact from this data.

Such screens also have high transparency and are capable of operating at even lower temperatures (down to -40 °C). Electrically conductive contaminants affect them to a lesser extent; they react to a gloved hand. High sensitivity allows the use of a thick layer of glass (up to 18 mm) to protect such screens.

Working principle of four-wire resistive touch screen

1. The upper resistive layer bends and comes into contact with the lower one.
2. The controller detects the voltage at the touch point on the bottom layer and calculates the X-axis coordinate of the touch point.
3. The controller detects the voltage at the touch point on the top layer and determines the coordinate of the touch point along the Y axis.

Working principle of five-wire resistive touch screen

1. The screen can be touched with any hard object.
2. The top conductive layer flexes and comes into contact with the bottom, which indicates touching the screen.
3. Two of the four electrodes of the lower layer are grounded, the controller determines the voltage at the point of contact and calculates the coordinate of the point along the X axis.
4. The other two electrodes are grounded, the controller determines the voltage at the point of contact and calculates the coordinate of the point along the Y axis.

Advantages

• Low cost
• High resistance to stains
• Can be touched by any hard object

Flaws

• Low durability (1 million clicks at one point for a four-wire, 35 million clicks for a five-wire) and vandal resistance
• Low light transmission (no more than 85%)
• Does not support Multitouch

Device examples

• Phones (for example, Nokia 5800, NTS Touch Diamond), PDAs, computers (for example, MSI Wind Top AE1900), industrial and medical equipment.

Principle of operation

1. The screen is touched with a conductive object (finger, special stylus).
2. Current flows from the screen to the object.
3. The controller measures the current at the corners of the screen and determines the coordinates of the touch point.

Advantages

• High durability (up to 200 million clicks), ability to operate at low temperatures (down to -15 ° C)

Flaws

• Susceptible to moisture, conductive contaminants
• Does not support Multitouch

Device examples

• Phones, touchpads (for example, in the iRiver VZO player), PDAs, ATMs, kiosks.

Principle of operation

1. A conductive object is touched or brought close to the screen, forming a capacitor with it.
2. At the point of contact, the electrical capacitance changes.
3. The controller registers the change and determines at which electrode intersection it occurred. Based on this data, the coordinates of the touch point are calculated.

Advantages

• High durability (up to 200 million clicks), ability to operate at low temperatures (down to -40 °C)
• High vandal resistance (the screen can be covered with a layer of glass up to 18 mm thick)
• High light transmittance (more than 90%)
• Multitouch supported

Flaws

• React to the touch only of a conductive object (finger, special stylus)

Device examples

• Phones (for example, iPhone), touchpads, laptop and computer screens (for example, HP TouchSmart tx2), electronic kiosks, ATMs, payment terminals.

Windows 7

It became possible to control the computer using the “Scroll”, “Forward/backward”, “Rotate” and “Zoom” gestures. The Windows 7 operating system is much better adapted to work with touch displays than everything previous versions. 06 this is evidenced by the modified interface and the taskbar, in which in place of rectangular buttons symbolizing running programs, square icons have appeared - they are much more convenient to press with your finger. In addition, a new feature has appeared - jump lists, allowing you to quickly find recently opened files or frequently launched items. To activate this feature, simply drag the program icon onto the Desktop.

For the first time in operating system Windows has added an option to recognize touch gestures, which are associated with the execution of individual functions. Thus, in Windows 7, touch scrolling appeared and, the same as, for example, in the Apple iPhone, the ability to enlarge pictures or documents by moving two fingers different sides. There was also movement responsible for rotating the image. Operations such as copy, delete, and paste can also be assigned separate gestures. The onscreen keyboard buttons light up when touched, making it easier to use on a touchscreen. And the ability to recognize handwritten text allows you to quickly enter small messages.

There is constant debate about which phone has the better screen. Especially between owners Apple technology and those who prefer devices on the Android platform.

This simple infographic beautifully breaks down all the benefits of each type of touchscreen. I hope that when you buy your next smartphone, it will help you do right choice and don’t overpay a tidy sum.

So, there are three types of touch screens: Resistive, Capacitive and Infrared.

Resistive

Phones with resistive screens: Samsung Messager Touch, Samsung Instinct, HTC Touch Diamond, LG Dare

How do they work? Small dots separate several layers of material that transmit current. When the upper flexible layer presses on the lower layer, the electric current changes and the location of the impact, that is, the touch, is calculated.

How much does it cost to manufacture? The cost of manufacturing resistive touch screens is not very high - $ .

Screen material. A layer of flexible material (usually a polyester film) is placed on top of the glass.

Tools of influence. Fingers, gloved fingers or stylus.

Visibility on the street. Poor visibility in sunny weather.

Possibility of multi-gestures. No.

Durability. For its price, the screen lasts quite a long time. Easily scratched and susceptible to other minor damage. It wears out quite quickly and requires replacement.

Capacitive

Phones with capacitive touch screens: Huawei Ascend, Sanyo Zio, iPhone, HTC Hero, DROID Eris, Palm Pre, Blackberry Storm.

How do they work? The current is broadcast from the corners of the screen. When a finger touches the screen, it changes the direction of the current and thus the location of the touch is calculated.

How much does it cost to manufacture? Quite expensive - $$ .

Screen material. Glass.

Tools of influence. Only fingers without gloves.

Visibility on the street. Visibility on a sunny day is good.

Possibility of multi-gestures. Eat.

Durability.

Infrared

Phones with infrared touch screens: Samsung U600 (heat), Neonode N2 (optical).

How do they work? In order for the heat-sensitive screen to react, you need to touch it with a warm object. Optical screen uses a grid of invisible sensors directly above the screen. The touch point is calculated based on the point where x-y axis was violated.

How much does it cost to manufacture? Very expensive - $$$ .

Screen material. Glass.

Tools of influence. Optical - fingers, gloves and stylus. Heat-sensitive - warm fingers without gloves.

Visibility on the street. Visibility in sunny weather is good, but strong sunlight affects productivity and accuracy.

Possibility of multi-gestures. Yes.

Durability. Lasts quite a long time. Glass breaks only from serious damage.

Touch screens have become widespread due to their convenience.

The term Touch Screen is formed from two English words. The first means “touch”, and the second means “screen”. This phrase fully conveys the principle of operation of this type displays, which consists of responding to the touch of a person’s fingers and performing certain actions. Although this type technology seems modern to us; the date of invention of the first touch screen is considered to be 1970. It was then that a university teacher from Kentucky, Samuel Hurst, was the first to decide to simplify the process of reading information from recorder tapes. The result of the scientist’s development was the appearance of the world’s first screen that supports the technology touch input.

FOR YOUR INFORMATION!

The new product used the most primitive type of operation: a four-wire resistive method for determining the coordinates of the touch point.

The first devices to receive similar system computers began to enter information, and only in 1998 the first cell phone was born that used touch-sensitive dialing. It was the brainchild of Alcatel. Next, Ericsson offered its version of a touchscreen in a mobile device. But these prototypes had little resemblance to modern versions touch screens.

The panel was monochrome, small in size and only allowed the user to dial a number. The first model where the touch screen acquired a modern shape was the communicator from HTC Qtek 1010/02 XDA, released in 2002. And the idea of ​​using a touchscreen in mobile devices was brought to a qualitatively new level by Apple, which implemented the Multitouch feature or response to simultaneous touching of the screen with two or more fingers.

IMPORTANT!

The invention and mass introduction of touchscreens brought a large number of positive aspects for the user and increased the usability of the smartphone. But this led to one significant drawback - the devices became more “delicate” and required careful attitude, since damage to the glass could destroy the entire sensor.

One of the areas of application of the touchscreen is graphics tablets, the use of which simplifies the process of creating animation

What is a sensor and where is it used?

Modern people can no longer imagine their lives without devices that have touch input, this invention has become so firmly established in life. According to statistics, more than 90% of the entire population of the Earth has at least once encountered a touchscreen, which is used in a variety of electronic devices and gadgets:

• smartphones;
• tablets and tablet computers;
• banking or payment terminals;
• devices for purchasing electronic tickets;
• displays (computer, in refrigerators, household appliances).

The development of touch technology is not limited to mobile devices. There are developments where the touchscreen is embedded in large surface areas.

FOR YOUR INFORMATION!

Not long ago, a smart desk was announced, the surface of which is one large touchscreen. A similar tabletop can be used as multimedia center V " smart home" Also, a few years ago, an entire touch wall was introduced, by pressing any area of ​​which you can call up various functions.

The interactive wall is a technology of the future that also uses a touchscreen

Some non-technical people wonder what a touchscreen on a tablet is and how it differs from a similar input device on a smartphone. The answer to this question is simple - nothing, since the principle of operation of the touch screen is similar, regardless of the device in which it is used.

In a special publication on our portal we will talk in detail about sensory inexpensive smartphones. You will find out whether a budget smartphone can be good: advantages and disadvantages, how to choose a smartphone based on parameters: display, memory, processor.

How does the touch screen work?

To fully understand what a touchscreen on a phone is, you need to understand what the smartphone screen is made of and how the sensor works. The main elements of the touch screen are:

1. A matrix consisting of a layer of liquid crystals. Similar display surface technology is used in a television or computer monitor.
2. Microdiodes, which are located in the second layer under the matrix and serve to illuminate the working surface.
3. Diodes located on the surface of the imaging layer, which are the main touch processing tool.
4. Glass that covers the screen itself and prevents it from damage.
5. Anti-glare coating prevents glare and allows you to comfortably look at the screen in sunny weather.

The simplest diagram of a touchscreen device

Based on how the touchscreen works, there are a number of advantages and disadvantages similar technology user dialogue with electronic device, which are divided into pros and cons for stationary devices and mobile equipment.

pros	Minuses
Stationary devices
Increased level of reliability.	Lack of tactile feedback.
High wear resistance, dust resistance and immunity to small impacts.	Placing the device at the level of the human body leads to hand fatigue during prolonged use.
	A small keyboard may cause errors or typos.
Mobile devices
Easy to use.	Lack of tactile sensations.
Given the small size of the device itself, it is possible to create the largest possible screen.	Some matrices consume a large amount of energy when illuminated for a long time, which leads to the need for frequent charging.
Convenience of typing even large amounts of text.	Mechanical damage can lead to damage to the touchscreen.
There is an evolution of touch input technology, which leads to the emergence of qualitatively new devices with better capabilities every year.	Lack of the required level of hygiene.

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Many manufacturers, especially stationary devices that use a touchscreen, due to their shortcomings, have taken the path of duplicating the ability to input with mechanical keys. This is necessary if the touch screen fails.

The sizes of modern touchscreens depend on the needs of the manufacturer and the device in which they will be used

Types of touch screens

The general classification of touchscreens that are on the market involves dividing them into varieties based on type and design features. The most commonly used are resistive and capacitive types, which are used in most mobile gadgets. There are also:

• matrix;
• infrared;
• projective capacitive;
• optical;
• DST sensors;
• wave;
• induction

The resistive sensor is considered “last century” due to imperfect technology

Resistive touch screen

When talking about what a Touch Screen is, the first thing we should mention is resistive screens, which were the first to be mass produced. Such screens consist of two transparent plates made of plastic, onto which a thin conductive mesh is applied. A dielectric layer is installed between the plates, which is required to sense the user pressing the desired area of ​​the screen.

When the owner of the smartphone performs an action (for example, clicking on the desired area of ​​the screen), the dielectric in this place moves apart, which leads to the contact of the two plates with each other. A current appears, which is registered by a special controller that determines the specific pressing point using a coordinate grid. Next, this data enters the processing program, which, according to a pre-created algorithm, performs the necessary action.

Special electrodes located at the corners of the matrix are responsible for determining the coordinates of the pressing point.

Resistive screens, in turn, are divided into two subtypes:

1. Four-wire sensor. They are made from just one panel made of glass and a plastic membrane, onto which the resistive supply of the screen itself is applied. All free space between glass and plastic is filled with insulators. When you press, the circuit closes, which leads to the appearance of the coordinates of the point of contact.
2. Five-wire. A distinctive feature of this type is the absence of resistive support for the membrane and the presence of a conductive layer. This provides greater reliability, since even after the matrix is ​​damaged, it continues to work. The pressure point is tracked by the degree of change in membrane voltage.

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There are also eight-wire resistive screens that improve the accuracy of touch processing, but do not increase the reliability of this type of sensor.

The disadvantage of a resistive sensor is the lack of multi-touch support

Speaking about resistive touch screens, it should be noted their low cost, the ability to press with a finger, stylus, or even a gloved hand. The disadvantages include:

• low degree of conductivity of light rays;
• susceptibility to scratches and cracks due to impact;
• lack of multi-touch;
• short service life, which averages no more than 34 million clicks;
• the impossibility of implementing the function of sliding across the screen, since the resistive matrix only responds to pressing.

Capacitive touch screen

The modern type of matrix is ​​a capacitive screen type. What it is? The essence of the work of this type is to follow the laws of elementary physics, namely the property of an object with a larger capacity to conduct alternating current.

At the heart of the work capacitive type lies the rule of electrical potential difference

In terms of its design, this type of matrix is ​​a glass plate, on the surface of which a layer of resistive material is applied.

FOR YOUR INFORMATION!

The best resistors in this case are alloys of indium oxide and tin oxide.

At the corners of the screen there are electrodes that apply a small voltage to the entire surface of the matrix. Upon contact with a person’s finger, a leak occurs, which is recorded by sensors and transmitted to the processing controller, which calculates the coordinates of the point of pressure. Distinctive features of this type of screens are long term service, which is more than 200 million clicks, increased transparency, the ability to not leak liquid. But the surface of this sensor still remains vulnerable to mechanical impact, so similar types of matrix are used in stationary devices located in areas protected from impact. external factors place.

Most modern mobile devices use projected capacitive sensors

Projected capacitive sensors

Speaking about what a touch screen is, you should definitely note the type of matrix that is used in most modern smartphones and tablet computers. We are talking about a projective capacitive sensor. A design of this type is represented, in addition to the usual panel, by a grid of electrodes that are applied to reverse side matrices. The existing electrodes, together with the human body, form a capacitor, and built-in electronics are required to measure the capacitance of the resulting system.

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One of the leaders in screen production, Samsung company, managed to fit pressure-sensitive electrodes between sub-piskels, allowing for simplified design and increased transparency.

Increased transparency, the ability to use thick glass (up to 19 mm) - all this reduces the risk of damage to projection-capacitive screens, which is why they are installed in devices located in open areas.

In the infrared sensor, the principle of operation is to interrupt the IR rays at the point of contact

Matrix and infrared touch screens

Among the varieties of sensors, we can mention two not very common types - matrix and infrared screens. Matrix work according to general principles resistive structures, but they distinctive feature is simplicity. Vertical conductive strips are applied to the membrane surface, and horizontal conductive strips are applied to the glass surface. When pressed, the strips come into contact, and the controller calculates the location of contact and determines the coordinates of the point. A significant disadvantage is the impossibility of ensuring high discreteness of the sensor due to the simplicity of the design.

Infrared types use a similar principle of intersecting stripes that represent infrared rays. When you touch the screen with any object, the grid of rays is interrupted at this point. This type is used on devices that require high image clarity, for example, e-books. The disadvantage of the IR sensor is its susceptibility to contamination.

Interactive maps use a strain gauge sensor type

Optical and strain gauge touch screens

The optical type is distinguished by the presence of infrared illumination, which is distributed between the glass and the matrix, and is capable of reflecting up to 100% of light within itself. When touched with a finger, dispersion occurs. The electronics just have to create a scattering pattern to determine the pressing point. This is done in the following ways:

• installing a camera next to the projector;
• introduction of an auxiliary subpixel.

Similar types of screens are used in interactive school boards. The strain gauge sensor is sensitive to screen surface deformation. This type is characterized by increased resistance to damage, so these matrices are used on ticket selling devices and ATMs.

DST technology works on the principle of recording piezoelectric manifestations inside a glass panel when pressed with a finger

DST touch screens

The basis of this type of operation is to capture the piezoelectric phenomenon in the glass panel. The main feature is the ability to respond to touch by any object and operate in any dusty conditions. For high-quality operation, the finger must be constantly in motion.

How to calibrate the touch screen

Owners of gadgets with a touch screen often encounter a problem when the sensor stops “listening” or responding correctly to touches. This can happen due to damage to the matrix, moisture getting inside the device, or replacement of the display.

After moisture gets inside the smartphone, it may be necessary to calibrate the touchscreen

There are two main ways you can calibrate your touchscreen:

• regular means operating system;
• using third-party software.

The built-in calibration technology is almost the same for all smartphone manufacturers. To configure using standard tools, you need:

• go to phone settings;
• find the “Calibration” item;
• press at least three times to the center of the target that appears on the screen.

The device independently remembers touches and adjusts the touchscreen.

It is best to replace the touchscreen at a specialized service center.

The touchscreen does not work - how to determine it

In some cases, the touch screen may malfunction. At mechanical damage There is no need to detect a breakdown of the matrix, since it is visible to the naked eye. Signs indicating the failure of the touchscreen in the absence of external damage are:

• lack of response to touch;
• partial response of the screen to pressing, for example, only a certain area can work;
• distortions in the perception of touch.

The appearance of artifacts on the screen may indicate problems not only with the display itself, but also with the sensor

If the sensor fails, the device will need to be repaired. Modern technologies imply the production of common display module, in which the touchscreen and display are combined into a single unit. Therefore, repairs require a complete replacement of the unit if it is impossible to separate the touchscreen. This can only be done in the terms of service.

Touchscreen and display: what's the difference?

The difference between these two parts lies in the functions they perform. The display is the part of the smartphone that is necessary to display images and information.

Increasingly, manufacturers are combining the touchscreen and display into a single unit

A touchscreen is a touch glass that is used to trigger the device on user actions and respond to pressing to call a certain function. Modern manufacturers have increasingly begun to produce unique “sandwiches” that use lamination technology, when the display and touchscreen are combined into a monolithic unit, glued together with a transparent sealant. This improves performance, but requires complete replacement of the part if any component fails.

Now you will look at your smartphone or tablet PC in a new way. In any case, share your experience of unlocking a “asleep screen” in the comments and ask questions to the author of the article.