Touch screens have become widespread due to their convenience.
The term Touch Screen is formed from two English words. The first stands for "touch" and the second stands for "screen". This phrase fully conveys the principle of operation of this type of display, which consists in responding to the touch of a person's fingers and performing certain actions. Despite the fact that this type of technology seems modern to us, the date of the invention of the first touch screen is considered to be 1970. It was then that a professor at the University of Kentucky, Samuel Hurst, was the first to decide to simplify the process of reading information from recorder tapes. The result of the development of the scientist was the appearance of the world's first screen that supports touch input technology.
NOTE!
The novelty used the most primitive type of work: a four-wire resistive method for determining the coordinates of the touch point.
Computers were the first devices that received such an information input system, and only in 1998 the first cell phone was born, which used touch dialing. It was the brainchild of Alcatel. Following its version of the touchscreen in a mobile device was offered by Ericsson. But these prototypes had little resemblance to modern versions of 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 possibility of Multitouch or a response to the 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 minus - the devices became more “gentle” and required careful handling, since damage to the glass could disable the entire sensor.
One of the areas of application of the touchscreen are graphic tablets, the use of which simplifies the process of creating animation.
What is a sensor and where is it used
Modern man can no longer imagine his life without devices with touch input, this invention has become so firmly established in life. According to statistics, more than 90% of the entire population of the Earth at least once encountered a touchscreen, which is used in a variety of electronic devices and gadgets:
- smartphones;
- tablets and tablet computers;
- bank or payment terminals;
- devices for purchasing electronic tickets;
- displays (computer, in refrigerators, household appliances).
The development of touch input technology is not limited to mobile devices. There are developments where the touchscreen is embedded in a large surface area.
NOTE!
Not so long ago, a smart table was announced, the surface of which is one large touchscreen. A similar tabletop can be used as a multimedia center in a "smart home". Also, a whole sensory wall was introduced a few years ago, by clicking on any area of \u200b\u200bwhich you can call up various functions.
The interactive wall is the technology of the future, which also involves the touchscreen
Some people who are ignorant of technology are wondering what a touchscreen is on a tablet 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 of our portal, we will talk in detail about low-cost touch smartphones. You will find out whether a budget smartphone can be good: advantages and disadvantages, how to choose a smartphone according to its parameters: display, memory, processor.
How the touch screen works
To fully understand what a touchscreen is on a phone, you need to understand what the smartphone screen consists of and how the sensor works. The main elements of the touch screen are:
- A matrix consisting of a layer of liquid crystals. A similar display surface technology is used in a TV or computer monitor.
- Microdiodes, which are located in the second layer under the matrix and serve to illuminate the working surface.
- Diodes located on the surface of the display layer, which are the main touch processing tool.
- The glass that covers the screen itself and prevents it from being damaged.
- Anti-reflective coating that prevents glare and allows you to comfortably view the screen in sunny weather.
The simplest scheme of the touchscreen device
Based on how the touchscreen works, there are a number of advantages and disadvantages of such a technology for a user dialogue with an electronic device, which are divided into pros and cons for stationary devices and mobile technology.
| pros | Minuses |
| Stationary devices | |
| Increased level of reliability. | Lack of tactile feedback. |
| High wear resistance, dustproof and immunity to small shocks. | Placing the device at the level of the human body leads to fatigue of the hands during prolonged work. |
| A small keyboard can cause errors or typos. | |
| Mobile devices | |
| Ease of use. | Lack of tactile sensations. |
| With a small size of the device itself, it is possible to create the largest possible screen. | Some matrices consume a large amount of energy during a long glow, which leads to the need for frequent charging. |
| Ease of typing even large amounts of text. | Mechanical damage can lead to breakage of the touchscreen. |
| The evolution of touch input technology is observed, which leads to the emergence of qualitatively new devices with better capabilities every year. | Lack of the required level of hygiene. |
NOTE!
Many manufacturers, especially stationary devices that use a touchscreen in their work, based on shortcomings, have taken the path of duplicating the possibility of entering mechanical keys. This is necessary when the touch screen fails.
The dimensions of modern touchscreens depend on the needs of the manufacturer and the device in which they will be used.
Touch screen types
The general classification of touchscreens that are on the market implies a division into varieties according to the type and design features. The most used are resistive and capacitive types, which are used in most mobile gadgets. Also exist:
- matrix;
- infrared;
- projective-capacitive;
- optical;
- DST sensors;
- wave;
- induction.
The resistive sensor is considered the "last century" due to the imperfection of the technology
Resistive touch screen
Speaking about what Touch Screen is, the first thing to mention is resistive screens, which were the first in mass production. Such screens consist of two transparent plates made of plastic, on which the thinnest conductive mesh is applied. A dielectric layer is installed between the plates, which is required to capture the pressure on the desired area of the screen by the user.
When an action is performed by the smartphone owner (for example, by clicking on the desired area of the screen), the dielectric moves apart in this place, which leads to the contact of the two plates with each other. A current appears, which is registered by a special controller that determines a specific point of pressing on the grid of coordinates. Further, these data are sent to the processing program, which, according to a previously 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 are, in turn, divided into two subtypes:
- Four-wire sensor. They are made from just one panel, made of glass and a plastic membrane, on which the resistive support of the screen itself is applied. All free space between glass and plastic is filled with insulators. When pressing, the circuit is closed, which leads to the appearance of the coordinates of the point of contact.
- Five-wire. A distinctive feature of this type is the lack of resistive support of the membrane, the presence of a conductive layer. This provides greater reliability, because even after damage to the matrix, it continues to work. The pressure point is tracked by the degree of change in the membrane voltage.
NOTE!
There are also 8-wire resistive shields that improve the accuracy of touch processing, but do not increase the reliability of this type of sensor.
The disadvantage of the resistive sensor is the lack of multi-touch support
Speaking of resistive touch screens, one should note their low cost, the ability to press with a finger, a stylus, and even a gloved hand. Among the shortcomings can be identified:
- low degree of conductivity of light rays;
- susceptibility to scratches and cracks due to impact;
- lack of multitouch;
- short service life, which averages no more than 34 million clicks;
- the impossibility of implementing the function of sliding on the screen, since the resistive matrix responds only to pressing.
Capacitive touch screen
A modern type of matrix is a capacitive screen type. What it is? The essence of the work of this variety is to follow the laws of elementary physics, namely, the property of an object of greater capacity to conduct alternating current.
The operation of the capacitive type is based on the rule of the difference in electrical potentials
According to its structure, this type of matrix is a glass plate, on the surface of which a layer of resistive material is deposited.
NOTE!
In this case, alloys of indium oxide and tin oxide are used as the best resistors.
At the corners of the screen are electrodes that apply a small voltage to the entire surface of the matrix. Upon contact with a human 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 a long service life, which is more than 200 million clicks, increased transparency, and the ability to not let liquid through. But the surface of this sensor still remains vulnerable to mechanical impact, so these types of matrix are used in stationary devices located in a place protected from external factors.
Most modern mobile devices use projected capacitive sensors.
Projective-capacitive sensors
Speaking about what a touch screen is, one should definitely note the type of matrix that is used in most modern smartphones and tablet computers. This is a projection-capacitive sensor. A design of this type is represented, in addition to the usual panel, by a grid of electrodes that are applied to the reverse side of the matrix. The existing electrodes, together with the human body, form a capacitor, and the built-in electronics is required to measure the capacitance of the resulting system.
NOTE!
One of the leaders in the production of screens, Samsung, managed to fit pressure-sensitive electrodes between sub-pixels, which made it possible to simplify the design and increase transparency.
Increased transparency, the ability to use thick glass (up to 19 mm) - all this reduces the risk of damage to projective-capacitive screens, so they are installed in devices located in an open area.
In an infrared sensor, the principle of operation is to interrupt the infrared rays at the point of contact
Matrix and infrared touch screens
Among the varieties of sensors, two not the most common types can be mentioned - matrix and infrared screens. Matrix ones work on the general principles of resistive designs, but their distinguishing feature is simplicity. Vertical conductive strips are applied to the surface of the membrane, and horizontal strips are applied to the glass surface. When pressed, the strips touch, and the controller calculates the place of contact and determines the coordinates of the point. A significant disadvantage is the impossibility of providing a high resolution of the sensor due to the simplicity of the design.
The infrared types apply a similar principle of intersecting bands, which are infrared rays. When touching the screen with any object, the grid of rays is interrupted at this point. This type is used on devices that require high-definition image transmission, for example, e-books. The disadvantage of the IR sensor is its susceptibility to contamination.
Interactive maps use 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 up to 100% reflection of light within itself. When touched with a finger, dispersion occurs. Electronics only needs to create a dispersion pattern to determine the point of pressure. This is done in the following ways:
- installing the camera next to the projector;
- the introduction of an auxiliary sub-pixel.
Similar types of screens are used in interactive school boards. The strain gauge sensor is sensitive to deformation of the screen surface. This type is distinguished by increased resistance to damage, so these matrices are used on ticketing devices, ATMs.
DST technology works on the principle of registering piezoelectric manifestations inside the glass panel when pressed with a finger
Touch screens DST
The basis of this type of work is to fix the piezoelectric phenomenon in the glass panel. The main feature is the ability to respond to touch with any object and function in any dusty conditions. For high-quality operation, the finger must be constantly in motion.
How to do touch screen calibration
Owners of gadgets with a touch screen often face a problem when the sensor stops “listening” or responding correctly to pressing. This can happen due to damage to the matrix, moisture inside the device, or replacement of the display.
If moisture gets inside the smartphone, it may be necessary to calibrate the touchscreen
There are two main ways to calibrate the touch screen:
- regular means operating system;
- using third party software.
The built-in calibration technology is almost the same for all smartphone manufacturers. To carry out customization by regular means, you need:
- go to phone settings;
- find the item "Calibration";
- click at least three times in the center of the target that appears on the screen.
The device independently remembers touches and adjusts the touchscreen.
Touchscreen replacement is best done in a specialized service
The touchscreen is not working - how to determine it
In some cases, the touch screen may fail. In case of mechanical damage to the matrix, it is not necessary to determine the breakdown, 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 screen response to pressing, for example, only a certain area can work;
- touch perception distortions.
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 involve the manufacture of a common display module, in which the touchscreen and display are combined into a single unit. Therefore, the repair requires a complete replacement of the unit if it is impossible to separate the touchscreen. This can only be done in terms of service.
Touchscreen vs Display: What's the Difference?
The difference between these two parts lies in the functions performed. The display is the part of the smartphone that is needed 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 specific function. Modern manufacturers are increasingly producing a kind of "sandwiches", which uses lamination technology, when the display and the touchscreen are combined into a monolithic unit, glued with a transparent sealant. This improves performance, but requires a complete replacement of the part if any component fails.
Now you have a new look at your smartphone or tablet PC. In any case, share in the comments your experience of unlocking the “sleep screen” and ask questions to the author of the article.
Until quite recently, few people could believe that phones with familiar buttons would give way to devices that are controlled by touching the screen. But times are changing and the demand for push-button phones is gradually falling, while for smartphones it is growing.
The term "touchscreen" was formed from two words - Touch and Screen, which is translated from English as "touch screen". Yes, that's right - the touchscreen is the touch screen that you touch when you use your smartphone or tablet. In fact, touch screens are found not only in the world of mobile technology. So, you could see them when depositing funds to the account of a mobile device through a terminal, at an ATM, in ticket devices, etc.
Touch-screen owes its appearance to Western scientists. The very first samples were born in the second half of the 60s of the last century. Based on this, we can conclude that the touchscreen has been used for more than 40 years. Before the advent of smartphones, they were used in ATMs, etc. At the moment, every person who uses cellular communications, car navigators, visits banks and shops, is faced with this technology, sometimes not even guessing what it is called. So, we figured out what a touchscreen is in phones. In fact, this is the same as the display that responds to the touch of your fingers. It is perfectly used instead of the keyboard and is actively used in mobile technologies. The advantages of the touchscreen include protection from dust, moisture and other adverse environmental factors, as well as a high degree of reliability. If our touch device does not always respond to touch, or even refuses to do it at all, for example, does not want to change the brightness on the iPad, it is most likely that the touch-screen has failed. It is relatively inexpensive (especially if we are interested in a resistive display), and it is easy to replace it.
The basis of the touchscreen
The basis of any touchscreen is a liquid crystal matrix, which is actually a reduced copy of the one in the monitor. On the reverse side there are backlight diodes, and on the front side there are a number of layers that detect pressing (resistive screen) or touching (capacitive screen).
A person who is well versed in what a touchscreen is understands that most of the devices manufactured use a resistive touch screen. This follows from their low cost and relative simplicity of design. Many Chinese "smartphones" that have flooded the market have a resistive screen type, the manufacturing technology of which, by the way, appeared earlier than capacitive.
Types of touch screens
Touch screens are divided into resistive, matrix, projective-capacitive, surface-acoustic wave touch screens, infrared, optical, tensometric, DST touch screens and induction.
Resistive touch screens
Subdivided into four-wire and five-wire.
The resistive screen sensor consists of two transparent plastic plates with a thin conductive mesh, which are located on the surface of a conventional LCD screen. Between the plates is a transparent dielectric layer. The program displays a graphical interactive interface, which is clearly visible due to the transparent materials on the matrix. Responding to a program request, the user clicks on the desired interface point (for example, a button image). - The plastic dielectric diverges, the plastic plates touch, supplying current from the electrode of one to the grid of the other. The appearance of the current is fixed by the registering controller, which, in accordance with the grid of coordinates, will determine the point of pressing. Point coordinates enter the program and are processed according to the established algorithms.
4-wire shield
The resistive touch screen consists of a glass panel and a flexible plastic membrane. Both the panel and the membrane have a resistive coating. The space between the glass and the membrane is filled with micro-insulators, which are evenly distributed over the active area of the screen and reliably isolate conductive surfaces. When the screen is pressed, the panel and membrane are closed, and the controller, using an analog-to-digital converter, registers the change in resistance and converts it into touch coordinates (X and Y). In general terms, the reading algorithm is as follows:
A voltage of + 5V is applied to the upper electrode, the lower one is grounded. The left and right are short-circuited, and the voltage on them is checked. This voltage corresponds to the Y-coordinate of the screen.
Similarly, + 5V and “ground” are supplied to the left and right electrodes, the X-coordinate is read from the top and bottom.
There are also eight-wire touch screens. They improve tracking accuracy, but do not improve reliability.
Five wire shield
The five-wire screen is more reliable due to the fact that the resistive coating on the membrane is replaced by a conductive one (the 5-wire screen continues to work even with the membrane cut through). The rear glass has a resistive coating with four electrodes at the corners.
Initially, all four electrodes are grounded, and the membrane is “pulled up” by a resistor to + 5V. The membrane voltage level is constantly monitored by an analog-to-digital converter. When nothing is touching the touch screen, the voltage is 5V.
As soon as the screen is pressed, the microprocessor detects the change in the membrane voltage and begins to calculate the coordinates of the touch as follows:
+5V voltage is applied to the two right electrodes, the left ones are grounded. The voltage on the screen corresponds to the X-coordinate.
The Y-coordinate is read by connecting both upper electrodes to +5V and both lower electrodes to ground.
Resistive touch screens are cheap and dirt resistant. Resistive screens respond to touch with any smooth solid object: a hand (bare or gloved), a pen, a credit card, a pick. They are used everywhere where vandalism and low temperatures are not excluded: for the automation of industrial processes, in medicine, in the service sector (POS-terminals), in personal electronics (PDA). The best samples provide an accuracy of 4096×4096 pixels.
The disadvantages of resistive screens are low light transmission (no more than 85% for 5-wire models and even lower for 4-wire models), low durability (no more than 35 million clicks at one point) and insufficient vandal resistance (the film is easy to cut).
Matrix touch screens
The design is similar to resistive, but simplified to the limit. Horizontal conductors are applied to the glass, vertical conductors are applied to the membrane.
When the screen is touched, the conductors touch. The controller determines which conductors are shorted and sends the corresponding coordinates to the microprocessor.
They have very low accuracy. Interface elements have to be specially arranged taking into account the cells of the matrix screen. The only advantage is simplicity, cheapness and unpretentiousness. Typically, matrix screens are queried row by row (similar to a matrix of buttons); this allows you to set up multitouch. Gradually replaced by resistive ones.
Capacitive touch screens
A capacitive (or surface capacitive) screen takes advantage of the fact that an object of high capacity conducts alternating current.
A capacitive touch screen is a glass panel coated with a transparent resistive material (usually an alloy of indium oxide and tin oxide). Electrodes located at the corners of the screen apply a small alternating voltage (the same for all corners) to the conductive layer. When touching the screen with a finger or other conductive object, current leakage occurs. At the same time, the closer the finger is to the electrode, the lower the resistance of the screen, which means that the current strength is greater. The current in all four corners is recorded by sensors and transmitted to the controller, which calculates the coordinates of the touch point.
Earlier models of capacitive screens used direct current - this simplified the design, but with poor user contact with the ground, it led to failures.
Capacitive touch screens are reliable, about 200 million clicks (about 6 and a half years of clicks with an interval of one second), do not leak liquids and tolerate non-conductive pollution perfectly. Transparency at 90%. However, a conductive coating located directly on the outer surface is still vulnerable. Therefore, capacitive screens are widely used in machines that are only installed in a weather-protected room. Not responsive to gloved hand.
It is worth noting that due to differences in terminology, surface and projection-capacitive screens are often confused. According to the classification used in this article, the screen, for example, iPhone is projected-capacitive, not capacitive.
Projected capacitive touch screens
A grid of electrodes is applied on the inside of the screen. The electrode together with the human body forms a capacitor; electronics measures the capacitance of this capacitor (applies a current pulse and measures the voltage).
Samsung has been able to install sensitive electrodes directly between the sub-pixels of the AMOLED screen, which simplifies the design and increases transparency.
The transparency of such screens is up to 90%, the temperature range is extremely wide. Very durable (the bottleneck is the complex electronics that process the clicks). Glass up to 18 mm thick can be used on the POSE, resulting in extreme vandal resistance. They do not react to non-conductive pollution, conductive ones are easily suppressed by software methods. Therefore, projective-capacitive touch screens are widely used in personal electronics and vending machines, including those installed on the street. Many varieties support multitouch.
Touch screens based on surface acoustic waves
The screen is a glass panel with piezoelectric transducers (PTs) located at the corners. Along the edges of the panel are reflective and receiving sensors. The principle of operation of such a screen is as follows. A special controller generates a high-frequency electrical signal and sends it to the PET. The PET converts this signal into SAW, and the reflective sensors reflect it accordingly.
These reflected waves are received by the appropriate sensors and sent to the PET. The probes, in turn, receive the reflected waves and convert them into an electrical signal, which is then analyzed by the controller. When you touch the screen with your finger, part of the energy of the acoustic waves is absorbed. The receivers capture this change, and the microcontroller calculates the position of the touch point. Reacts to touch with an object capable of absorbing the wave (finger, gloved hand, porous rubber).
The main advantage of the screen on surface acoustic waves (SAW) is the ability to track not only the coordinates of the point, but also the pressing force (here, rather, the ability to accurately determine the radius or area of pressing), due to the fact that the degree of absorption of acoustic waves depends on the pressure at the point touch (the screen does not bend under the pressure of a finger and is not deformed, therefore, the force of pressing does not entail qualitative changes in the processing by the controller of data on the coordinates of the impact, which fixes only the area that blocks the path of acoustic impulses).
This device has a very high transparency, since the light from the display device passes through the glass, which does not contain resistive or conductive coatings. In some cases, glass is not used at all to combat glare, and emitters, receivers, and reflectors are attached directly to the screen of the display device. Despite the complexity of the design, these screens are quite durable. According to, for example, the American company Tyco Electronics and the Taiwanese company GeneralTouch, they can withstand up to 50 million touches at one point, which exceeds the resource of a 5-wire resistive screen.
SAW screens are mainly used in slot machines, in secure reference systems and educational institutions. As a rule, surfactant screens are divided into ordinary - 3 mm thick, and vandal-resistant - 6 mm. The latter can withstand being punched by an average man or being dropped by a 0.5 kg metal ball from a height of 1.3 meters (according to Elo Touch Systems). The market offers options for connecting to a computer both via the RS232 interface and via the USB interface. At the moment, controllers for SAW touch screens that support both types of connection - combo (data from Elo Touch Systems) are more popular.
The main disadvantage of the screen on SAW are failures in the presence of vibration or when exposed to acoustic noise, as well as when the screen is dirty. Any foreign object placed on the screen (for example, chewing gum) completely blocks its operation. In addition, this technology requires touching an object that necessarily absorbs acoustic waves - that is, for example, a plastic bank card is not applicable in this case.
The accuracy of these screens is higher than matrix ones, but lower than traditional capacitive ones. For drawing and entering text, they are usually not used.
Infrared touch screens
The principle of operation of the infrared touch panel is simple - the grid formed by horizontal and vertical infrared rays is interrupted when you touch the monitor with any object. The controller determines where the beam was interrupted.
Infrared touch screens are sensitive to dirt and therefore are used where image quality is important, such as in e-readers. Due to its simplicity and maintainability, the scheme is popular with the military. Often, intercom keyboards are made on this principle. This type of screen is used in Neonode's abundant phones.
Optical touch screens
The glass panel is supplied with infrared illumination. At the "glass-air" boundary, total internal reflection is obtained, at the "glass-foreign object" boundary, the light is scattered. It remains to capture the scattering picture, for this there are two technologies:
In projection screens, a camera is placed next to the projector.
This is how, for example, Microsoft PixelSense works.
Or an additional fourth sub-pixel of the LCD screen is made photosensitive.
They allow you to distinguish between hand pressing and pressing with any objects, there is a multi-touch. Large touch surfaces are possible, up to the blackboard.
Strain gauge touch screens
Respond to screen distortion. The accuracy of strain gauge screens is not high, but they withstand vandalism very well. The main application is ATMs, ticket machines and other devices located on the street.
Touch screens DST
The touch screen DST (Dispersive Signal Technology) registers the piezoelectric effect in the glass. You can press the screen with your hand or any object.
A distinctive feature is the high reaction speed and the ability to work in conditions of severe screen pollution. However, the finger must move; the system does not notice a fixed finger.
At first, touchscreens (touch screens) were quite rare. They could be found only in some PDAs, PDAs (Pocket Computers). As you know, devices of this kind have not gained wide distribution, since they lacked the most important thing, that is, functionality. The history of smartphones is directly related to touchscreens. That is why at the present time you will not surprise a person with a “smart phone” with a touch screen. The touchscreen is widely used not only in fashionable expensive devices, but even in relatively inexpensive models of modern phones. What are the principles of operation of the 3 types of touch screens that can be found in modern devices.
Touchscreen types
Touch screens are no longer too expensive. In addition, touchscreens (touchscreen) today are much more "responsive" - the user's touch is recognized just fine. It is this characteristic that paved the way for them to a large number of users around the world. At the present time, there are three main designs of touchscreens:
- Capacitive.
- Wave.
- Resistive or simply "elastic".
Capacitive touchscreen: how it works
In touchscreen designs of this kind, the glass base is covered with a layer that acts as a charge storage container. The user releases part of the electric charge at a certain point with his touch. This reduction is determined by chips that are located in each corner of the screen. The computer calculates the difference in electrical potentials existing between different parts of the screen, while information about the touch in detail is transmitted immediately to the touchscreen driver program.
A rather important advantage of capacitive touchscreens is the ability of this type of screen to maintain almost 90% of the original brightness of the display. Because of this, images on a capacitive screen look sharper than on touchscreens that have a resistive design.
Capacitive touch screen video:
The Future: Wave Touch Displays
At the ends of the grid axes of the glass screen there are two transducers. One of them is the transmitter, the second is the receiver. On a glass base, there are also reflectors that “reflect” an electrical signal that is transmitted from one to another transducer.
The receiver-transducer absolutely “knows” whether there was a press, and also at what specific point it happened, since the user interrupts the acoustic wave with his touch. At the same time, the glass of the wave display does not have a metal coating - this makes it possible to preserve 100% of the original light in full. In this regard, the wave screen is the best option for those users who work in graphics with fine details, because resistive and capacitive touch screens are not ideal in terms of image clarity. Their coating delays light, which as a result significantly distorts the picture.
Video about the principle of operation of touch screens on SAW:
Past: about the resistive touchscreen
A resistive system is an ordinary glass, which is covered with a layer of an electricity conductor, as well as an elastic metal "film", which also has conductive qualities. There is an empty space between these 2 layers with the help of special spacers. The screen surface is covered with a special material that protects it from mechanical damage, such as scratches.
An electric charge in the process of a user working with a touchscreen passes through these two layers. How does this happen? The user at a certain point touches the screen and the elastic upper layer is in contact with the conductive layer - only at this point. Then the computer determines the coordinates of the point that the user has touched.
When the coordinates become known to the device, a special driver translates touches into commands known to the operating system. In this case, you can draw analogues with the driver of the most ordinary computer mouse, because it does exactly the same thing: it explains to the operating system what the user specifically wanted to tell her by moving the manipulator or pressing a button. With screens of this type, as a rule, special styluses are used.
Resistive screens can be found in relatively old devices. Just such a touch screen is equipped with IBM Simon - the most ancient smartphone of those that were conscious of our civilization.
Video about the principle of operation of a resistive touch screen:
Features of different types of touchscreens
The cheapest touch screens, but at the same time, the least clearly broadcasting the image are resistive touch screens. In addition, they are also the most vulnerable, because absolutely any sharp object can seriously damage a fairly delicate resistive “film”.
The next type, i.e. wave touchscreens are the most expensive among their kind. At the same time, the resistive design, most likely, refers, nevertheless, to the past, capacitive - to the present, and wave - to the future. It is clear that the future is absolutely unknown to anyone and, accordingly, at the present time, one can only assume which technology has great prospects for its use in the future.
For a resistive touchscreen system, it does not really matter whether the user touches the screen with the rubber tip of the stylus or simply with their finger. It is enough that there is contact between the two layers. At the same time, the capacitive screen recognizes only touches with some conductive objects. Often, users of modern devices work with them using their own fingers. In this respect, the screens of the wave design are closer to the resistive ones. You can give a command with almost any object - you just need to avoid using heavy or too small objects, for example, a ballpoint pen refill is not suitable for this.
The screen of any iPhone can be considered the most important component of the device. Of course, if you do not take into account the amount of memory, the operating system, the overall quality of the device, but judge only by appearance. And since the screen is so important, it should be treated with care. But practice stubbornly shows the opposite. Although it must be admitted that just this part of the smartphone is the least protected and the human factor has almost nothing to do with it. The materials that cover the front of the iPhone can fail, and that's where things get interesting. We run into service center and with a trembling voice, we ask you to replace only the glass and do not touch the display itself.
- So we change the glass or the display?
- Is there a difference?
That's the whole short dialogue, demonstrating our incompetence. And therefore, let's try to find out how glass replacement on the iPhone differs from replacing the display.
There is a difference
First of all, it should be firmly understood that the glass and display of the iPhone is like a chandelier and a light bulb. It makes no sense to change the entire chandelier if only the bulb is burned out, but you can replace the entire chandelier along with the bulbs or leave them from the old chandelier. Did you get the gist? The touch glass and the iPhone display are two parts that we used to call either a screen, or a monitor, or something else. But the essence remains the same: glass and a display are not the same thing, although they are mechanically interconnected and constitute a display module.
In order for our fingers to work wonders on the iPhone screen, the devices are equipped with a sensitive touch glass, which is installed on top of the display. Consequently, each of these parts has its own functions and purpose: the glass is responsible for finger touches, and the display displays an image.
You don't have to be Einstein to guess: you can replace the glass and the display separately if one of them has ceased to fulfill its function. The display may fail, but the touch layer remains fully functional. The situation is similar if you swap parts: the touch glass may be damaged, but the display remains functional.
A spoon of tar
Everything that was said above is the holy truth. But there is one caveat that makes the situation somewhat worse. The fact is that earlier iPhone models did have a display module that could be disassembled into components. Late series iPhones are designed in such a way that the display module does not disassemble and is considered as a whole. Is it good or bad, expedient or not - not for us to decide. So far, for iPhones starting with the 4th model, it is impossible to replace the glass and leave the display the same or vice versa.
But, nothing is impossible. The touch screen and the display are securely glued together, and it will take some effort to separate this pie. Not every master and not every service center will undertake such an operation. It is easier and more reliable, although much more expensive, to replace the entire display module in the event of a breakdown.
However, only original spare parts must be used! Because native, certified and original is the key to long-term use and correct operation. And everything else, of dubious production, is new headaches and a shattered nervous system.
Brief description of the process
Glass replacement on smartphones is approximately 65% of all repair cases. Therefore, the masters of the service centers had to “fill their hands” in order for this operation to be successful. The third-generation iPhone was easy to repair - the display and glass were separate. But already in the next generations of smartphones, glass replacement required the intervention of special tools. The separator (namely, this is the name of the tool) warms up the display so that you can easily separate the glass using a special string.
Important note: spare parts (glass or display) can either be taken from another similar device, or be close in quality to the original ones. The second option does not mean that the glass or display will necessarily be from Apple. You should not be afraid of the first option either: among the cemetery of iPhones there will always be “donors” with a fully working display or a whole glass.
To control modern gadgets, it is no longer necessary to press buttons, just touch the screen. This became possible thanks to the touchscreen (in the environment of experts they simply call it “touch” or “touch panel”), which has become an integral part of smartphones and tablets, including iPhones and iPads. Not surprisingly, due to frequent use, it often fails and becomes a headache for the owner of the device. If you understand what this component is and how it works, you can quickly detect a malfunction and avoid embarrassing situations when contacting a service center.
What is a touchscreen
This term was formed from two English words - touch and screen, which literally translates as "touch screen". The history of its appearance is long and took place in several stages. The world's first finger-operated display was invented and described in his scientific papers by the American E. A. Johnson in 1965. Five years later, Dr. Samuel Hurst, through experiments, developed resistive touch screen, and the physical production of the product began only in 1973.
Currently, urban residents deal with touch panels almost daily: not only smartphones and tablets are equipped with them, but also ATMs, reference terminals and payment acceptance points. touchscreen connects to the display and sensitive to any touch. It can be described as an input device that serves to replace the keyboard.
It is important to know that the touchscreen is only a part of the overall design, responsible only for the sensor. To send an image a display is used, which is a liquid crystal matrix. The unity of these two elements is called the display module, which is practically the main component of any high-tech device.
How the touch panel works
The principle of operation of the touchscreen is simple - any touch on it causes a function or entails certain actions. The physical features of its work directly depend on the type of touch panel. There are seven of them, but the most common today are three of them.
The cheapest in production, resistant to pollution and temperature extremes. Comprises glass panel and plastic membrane between which there are insulators. Any pressing causes the glass to push through the micro-insulator, and the membrane with the panel closes. After that, a special controller reads the changes and converts them into contact coordinates. The weaknesses of this model are low light transmission, short service life and a high risk of damage when dropped. 
Capacitive screen
More reliable and durable, but vulnerable to bad weather, water and pollution. It uses a special touch glass coated with a resistive material. An alternating current passes through it, which is supplied by electrodes located at the corners of the screen. That is, when you touch the touchscreen, current leakage occurs, which is fixed by special sensors. They register these changes and pass them to the controller.
Surface acoustic wave sensor
One of the most complex screens. The peculiarity of his work is that in the thickness of the glass there are ultrasonic vibrations. When you press the touchscreen, the waves are absorbed and converted into an electrical signal, which is then transmitted to the controller. The advantage of this technology is a long service life of at least 45 million touches. The main drawback is that the screen is extremely sensitive to pollution and electromagnetic interference.
In addition to this, there are several more varieties of touch panels. These include:
- Projected-capacitive. On the inside of such screens there is a grid of electrodes, which, when pressed, forms a capacitor, the capacitance of which is measured by electronic sensors.
- infrared. Along their edges are light emitters and receivers in the IR range, when you touch the screen, part of the light overlaps and thereby determines the place of pressing.
- Tansometric. Based on a simple fixation of the screen deformation, they are resistant to damage and are often installed outdoors.
- induction. Inside them there is an inductor and wires, when such a screen is touched with a special tool, the voltage of the existing magnetic field changes.
How to check touchscreen
The touch panel may not work correctly either if the mobile device is physically damaged, or for no apparent reason. The following factors indicate that the problem is in the sensor:
There may be several reasons for such a malfunction:
- Display dirty. If you do not wipe the sensor in a timely manner with special means, then during operation it is abundantly covered with fingerprints and greasy traces, which can reduce its sensitivity.
- Violation temperature regime. Too high or low temperatures, as well as their strong drop, is a common cause of touchscreen malfunction.
- Loop damage. It can peel off the glass in case of mechanical damage, thereby breaking the connection of the latter with the touch coating.
- Moisture ingress. If there is liquid inside the gadget, then oxidation of the contacts may occur. Sometimes the problem can be solved with a hair dryer.
- crash software. In this case, you need to reflash the device, this will require a USB cable and the software itself.
How to replace the touchscreen on your phone
Before removing the touch screen, turn off your smartphone, remove the battery and SIM card. It is important to remember the disassembly sequence, so that later you can assemble the device back and not damage the internal elements. In some models, a complete disassembly of the case may be required, which requires special knowledge. To replace the touch screen on your phone with your own hands, you need to prepare special equipment in advance, namely:
The touchscreen replacement process itself is as follows:
- Take off the back cover of the phone;
- Screwdriver unscrew all bolts along the perimeter of the body;
- Carefully insert spatula between the body mount and pry;
- hair dryer warm up the glue, connecting the sensor to the matrix up to a maximum temperature of 80 °C;
- Attach to display sucker, which will allow you to separate the touchscreen from the matrix;
- Apply thin layer of glue and install a new touch panel;
- Carefully press down it and remove the remaining glue;
- Assemble the device in reverse order.
What is the difference between touchscreen and display
The display is the part of the smartphone that displays the image. It is he who is the conductor of visual information and makes it available to the human eye. The touchscreen is a touch glass, the main purpose of which is to call one or another function. That is, he is only input tool, but no output. 
If the phone crashed and a cobweb appeared on it, but the screen continues to work and you can clearly see the picture, then only the sensor needs to be replaced. When the device distorts the image and shows blots, you will have to change the display, which is a more time-consuming and costly procedure.
