Resistive screen.
The simplest type is a four-wire, which consists of a special glass panel, as well as a plastic membrane. The space between the glass and the plastic membrane must be filled with micro-insulators, which can reliably isolate conductive surfaces from each other. Electrodes, which are thin plates made of metal, are installed over the entire surface of the layers. In the back layer, the electrodes are in a vertical position, and in the front layer, in a horizontal position so that coordinates can be calculated. If you press the display, the panel and the membrane will automatically close, and a special sensor will perceive the pressing, converting it into a signal. Eight-wire displays are considered the most advanced type, which have a high level of accuracy. However, these screens are characterized by a low level of reliability and fragility. If it is important that the display is reliable, it is necessary to stop the choice on its five-wire form.
1 - glass panel, 2 - resistive coating, 3 - microinsulators, 4 - film with conductive coating
matrix screens.
The design is similar to a resistive display, although it has been simplified. Vertical conductors were specially applied to the membrane, and horizontal conductors were applied to the glass. If you press the display, then the conductors will definitely touch, close crosswise. The processor can keep track of which wires are shorted, and this helps to detect the coordinates of the click. Matrix screens cannot be called high-precision, so they have not been used for a long time.
capacitive screens.
The design of capacitive screens is quite complex, and it is based on the fact that the human body and the display together form a capacitor that conducts alternating current. Such screens are made in the form of a glass panel, which is covered with a resistive material so that electrical contact is not hindered. The electrodes are located at the four corners of the display and are supplied with an alternating voltage. If you touch the surface of the display, then there will be an alternating current leakage through the aforementioned "capacitor". This is recorded by sensors, after which the information is processed by the microprocessor of the device. Capacitive displays can withstand up to 200 million clicks, they have an average level of accuracy, but, alas, they are afraid of any influence of liquids.
Projective-capacitive screens.
Projection-capacitive screens can, unlike the previous types considered, be able to detect several clicks at once. On the inside there is always a special grid of electrodes, and during contact with them a capacitor will be formed. In this place, the electric capacitance will be changed. The controller will be able to determine the point at which the electrodes crossed. Then the calculations take place. If you immediately press the screen in several places, then not one capacitor will be formed, but several.
Screen with a grid of infrared rays.
The principle of operation of such displays is simple, and to some extent it is similar to the matrix. In this case, the conductors are replaced with special infrared rays. Around this screen there is a frame in which there are built-in emitters, as well as receivers. If you tap on the screen, then some beams will overlap and they cannot reach their own destination, namely the receiver. As a result, the controller calculates the contact point. Such screens can transmit light, they are durable, since there is no sensitive coating and mechanical touch does not occur at all. However, such displays currently do not meet high accuracy and are afraid of any contamination. But the diagonal of the frame of such a display can reach 150 inches.
Touch screens on surface-acoustic waves.
This display is always made in the form of a glass panel, in which piezoelectric transducers are embedded, located at different angles. There are also reflective, receiving sensors along the perimeter. The controller is responsible for generating signals whose frequency is high. After that, the signals are always sent to piezoelectric transducers, which can convert the received signals into acoustic vibrations, which are subsequently reflected from reflective sensors. The waves can then be picked up by receivers, resent to piezoelectric transducers, and then converted into an electrical signal. If you press the display, the energy of the acoustic waves will be partially absorbed. Receivers are receptive to such changes, and the processor can calculate touchpoints. The main advantage is that touch screens based on surface acoustic waves track the coordinates of the pressing point, the pressing force. Displays of this type are durable, because they can withstand 50 million touches. Most often they are used for slot machines, reference systems. It should be taken into account that the operation of such a display may be inaccurate in terms of ambient noise, vibration, acoustic pollution.
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 University professor from 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 impacts. | 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. When a person touches a finger, a leak occurs, which is registered 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:
- standard means of the 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.
Our eyes are the main source of information received by the brain. Because the screen is the most important part of the mobile phone and tablet. It is from it that we read information and manage the interface. In this issue of the column, we will figure out how the screens of mobile devices work, what they are and how to choose the right smartphone, starting from this parameter.
If the screens of televisions and computer monitors at the dawn of technology used the principle of a cathode ray tube (CRT), then for mobile devices this approach to imaging was unacceptable due to their small size. In the 70s of the last century, the first liquid crystal monochrome screen was introduced. At first, it was used mainly in calculators and electronic watches. With the advent of mobile phones, the technology for the production of displays based on liquid crystals migrated to them. After a while, new technologies based on organic light-emitting diodes appeared, the screens became touch-sensitive, flexible.
Almost any liquid crystal screen (LCD or in English LCD) consists of the following components:
- Layers of liquid crystals that let light through.
- Active matrix responsible for image formation. Its most common variety is TFT, which is controlled by thin layer transistors.
- Light filters for obtaining a color image. As a rule, this is an RGB system - red, green and blue.
- Light source. It can be either active (smartphones, TVs, monitors, etc.) or passive - calculators, electronic watches.
There are many varieties of LCD displays. The easiest and cheapest of them all TN (Twisted Nematic). It has poor viewing angles, contrast and color reproduction, but a high response time. It is used mainly in budget devices and is gradually leaving the market. More advanced technology is IPS (in-plane switching). Unlike TN, it is characterized by high viewing angles, excellent color reproduction, and increased contrast. There are many varieties of IPS, which have different names for different manufacturers. Main:
- Just IPS- gradually dies off, the main disadvantage is the long response time of the active pixel. But it is still very often used in budget smartphones.
- AS-IPS- advanced IPS, characterized by a higher degree of contrast
- IPS pro- the next step in development with higher brightness and color reproduction. This display has mainly found its use in flagship gadgets.
Well known display type retina is a variation of IPS, but with a higher resolution and a reduced sub-pixel and pixel size. But Samsung has pls- the same modification of IPS, which is designed to reduce the cost of production.
In addition to IPS, there are also LCD displays called Super LCD(developed by HTS), Super Clear LCD(Samsung) VA/MVA/PVA(used mainly in monitors).
Another stage in the development of displays is a technology based on organic light emitting diodes - OLED(Organic Light Emitting Diode). Its essence is to use organic LEDs instead of liquid crystals, which need backlighting. They glow on their own.
There are several varieties of OLED displays:
- AMOLED(ActiveMatrixOLED) - uses organic light-emitting diodes which are controlled by a matrix based on thin film transistors (TFT). An interesting feature is the formation of black - the LEDs are simply turned off, and the result is a true deep black, while reducing the power consumption of the device as a whole. That is why dark themes are recommended in smartphones with AMOLED screens.
- SuperAMOLED- improved AMOLED. This technology provides for the absence of an air gap between the screen and the sensor. As a result, the thickness of the display decreases, the color reproduction and brightness increase. Such screens are widely used in their flagships by Samsung, Motorola and others.
- FOLED(Flexible OLED) - a technology that allows you to create flexible displays based on organic crystals. A striking representative of this implementation is Samsung's Edge line of smartphones.
still exists TOLED(TransparentOLED) - transparent displays, SOLED(Staked OLED) - stacked OLEDs, but they may not yet be used in smartphone displays.
In general, OLED technology has a number of advantages over LCD:
- Small screen thickness
- Low power consumption
- Very fast response
- High contrast
- Ability to create flexible displays
But there is a significant drawback - the lifetime of the LEDs. Over time, they die and the image on the screen is distorted. Although, perhaps this is a temporary problem of organic displays. After all, science does not stand still and new durable LEDs are being developed.
The next evolution could be TMOS (Time Division Optical Shutter) displays. Such screens can be brighter, more energy efficient and cheaper to produce than LCD and OLED.
Let's briefly dwell on other features of the screens of modern gadgets.
Today, controlling a smartphone with the help of fingers has already become commonplace for us. The sensor is responsible for this function on the screen. I want to tell you about their main types:
- Resistive sensor- consists of a glass plate and a membrane on which a resistive coating is applied. When we press a finger on the screen, the membrane and plate close and transmit the coordinates of pressing to the microprocessor. Their advantage is that such a sensor will respond to any object. It is also simple and cheap to manufacture. The disadvantages include poor security, light transmission and durability. Widely used in early PDAs and smartphones. Today this is a rarity.
- capacitive sensor- the principle of operation is that when our finger touches the glass on which the electrically conductive layer is applied, current leakage occurs. And the place of the greatest leakage (the point of contact of the finger with the glass) is recorded by a special controller. Such sensors are more transparent than resistive ones, and also withstand more than 200 million clicks. But to touch, for example, in gloves, they do not react. The capacitive sensor is installed mainly in budget smartphones.
- The next step in the development was projective-capacitive touch screens. An electrode grid is applied to the glass of such a screen (you can even see it on cheap Chinese phones), which, together with a person’s finger, forms a capacitor. Special electronics measure its capacitance and determine the point at which there was contact. The advantages are very high durability, sensitivity, and this technology allows you to recognize multiple clicks at the same time, in other words, it supports multitouch. The disadvantage is the need for complex signal processing electronics, and therefore high cost. In so many modern gadgets, this type of sensor is used.
These were the main types of sensors that are used in modern smartphones.
Next we will talk about screen pixel density. This value is the ratio of the screen resolution to its physical size. In other words - the number of pixels per inch of the diagonal of the smartphone. These numbers are usually measured in ppi (pixel per inch). To give an example, a screen with a diagonal of 5.1 inches and a resolution of 2560 × 1440 pixels has a dot density of 577 ppi. The larger this number, the clearer and more detailed the image on the smartphone screen will be. But will our eye be able to distinguish differences, for example, between 400 and 500 ppi? Marketers of development firms are sure that they can, I personally doubt it ....
To prevent the screen of our favorite smartphone from being scratched and beaten, all kinds of protective glasses have been developed. One of the most famous in the world is Gorilla Glass. Recently, its fourth revision was presented. According to the developers Gorilla Glass 4 has twice the resistance to damage compared to competing aluminosilicate glass. Less well-known, but not the worst in terms of performance, is Dragontrail high-strength glass. For example, it is widely used in its smartphones by the Chinese manufacturer Xiaomi.
Also, screen glasses are often coated with a special oleophobic coating, which is designed to protect against grease stains.
1. It is better to choose IPS or OLED technology than TN.
2. Much depends on the display manufacturer, beware of Chinese "nonames". Choose screens from LG, Sony, Sharp and other famous brands.
3. The pixel density is not particularly worth chasing. HD resolution is sufficient at a diagonal of 5", FHD - at 5.5".
4. No matter how good the glass is, anyway, stick a protective film over it, or better, special glass.
P.S. The article does not talk about the structure of the display pixel. The topic is interesting and voluminous, we will devote a separate material to it.
A touch screen is a device for input and output of information through a touch and gesture sensitive display. As you know, the screens of 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 a no less famous “mouse” manipulator appeared, which greatly simplified the manipulation of information on a computer display. However, the mouse requires a horizontal surface to work and is not very suitable for mobile devices. This is where an addition to the usual 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 an 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 (PDAs, PDAs), now communicators, mobile phones, players, and even photo and video cameras hold the lead. However, the technology of finger control via virtual buttons on the screen has proven to be so convenient that almost all payment terminals, many modern ATMs, electronic information kiosks and other devices used in public places are equipped with it.
touch screen laptop
It should also be noted that laptops, some models of which are equipped with a swivel touch display, which gives the mobile computer not only greater functionality, but also greater flexibility in managing it outdoors and on weight.
Unfortunately, there are not so many similar models of laptops, popularly called "transformers", but they are.
In general, touch screen technology can be described as the most convenient when you need instant access to device control without prior preparation and with amazing interactivity: controls can change each other depending on the activated function. Anyone who has ever worked with a touch device understands the above perfectly.
Touch screen types
In total, several types of touch panels are known today. Naturally, each of them has its own advantages and disadvantages. We single out four main structures:
- Resistive
- capacitive
- Projected-capacitive
In addition to these screens, matrix screens and infrared screens are used, but due to their low accuracy, their scope is extremely limited.
Resistive
Resistive touch panels are among the simplest devices. At its core, such a panel consists of a conductive substrate and a plastic membrane with a certain resistance. When the membrane is pressed, 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 pressing point.
The advantage of a resistive screen is its low cost and simplicity of the device. They have excellent resistance to dirt. 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 top end of a ballpoint pen or the corner of a plastic card). However, there are also quite serious drawbacks: resistive screens are sensitive to mechanical damage, such a screen is easy to scratch, so a special protective film is often purchased additionally to protect the screen. In addition, resistive panels do not work very well at low temperatures, and also have low transparency - they pass no more than 85% of the display's light flux.
Using the Touch Screen Pen
Application
- Communicators
- Cell Phones
- POS terminals
- Tablet PC
- Industry (control devices)
- Medical equipment
Communicator
capacitive
Capacitive touch screen technology is based on the principle that a large object (in this case, a person) is capable of conducting an electrical current. The essence of the capacitive technology is to apply an electrically conductive layer to the glass, while a weak alternating current is applied to each of the four corners of the screen. If you touch the screen with a grounded large capacitance object (finger), current leakage will occur. The closer the touch point (and hence the leakage) to the electrodes in the corners of the screen, the greater the leakage current, which is recorded by the control electronics, which calculates the coordinates of the touch point.
Capacitive screens are very reliable and durable, their resource is hundreds of millions of clicks, they perfectly resist pollution, but only those that do not conduct electricity. They are more transparent than resistive ones. However, the disadvantages are still the possibility of damage to the electrically conductive coating and insensitivity to touch by non-conductive objects, even with gloved hands.
Information kiosk
Application
- In secure premises
- Information kiosks
- Some ATMs
Projected-capacitive
Projection-capacitive screens are based on measuring the capacitance of a capacitor formed between the human body and a transparent electrode on the glass surface, which in this case is a dielectric. Due to the fact that the electrodes are applied on 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 the pressure of a finger in a glove.
Payment terminal
These screens are quite sensitive and distinguish between finger and conductive pen taps, and some models can recognize multiple taps (multi-touch). The features of the projection-capacitive screen are high transparency, durability, immunity to most contaminants. The disadvantage of such a screen is not very high accuracy, as well as the complexity of the electronics that process the coordinates of pressing.
Application
- Electronic kiosks on the streets
- Payment terminals
- ATMs
- Notebook touchpads
- iPhone
With the definition of surface acoustic waves
The essence of the touch panel with the definition of surface acoustic waves is the presence of ultrasonic vibrations in the thickness of the screen. When touching the vibrating glass, the waves are absorbed, while the point of contact is recorded by the screen sensors. The advantages of the technology include high reliability and pressure recognition (unlike capacitive screens). The disadvantages are poor protection from environmental factors, so screens with surface acoustic waves cannot be used outdoors, and in addition, such screens are afraid of any pollution that blocks their work. Rarely used.
Other, rare types of touch screens
- optical screens. Glass is illuminated with infrared light, as a result of touching such glass, light is scattered, which is detected by the sensor.
- induction screens. Inside the screen there is a coil and a grid of sensitive wires that react to touch with an active pen powered by electromagnetic resonance. It is logical that such screens respond to pressing only with a special pen. They are used in expensive graphics tablets.
- Tensometric - react to the deformation of the screen. Such screens have low accuracy, but are very durable.
- The infrared ray grid is one of the very first technologies to recognize touches on the screen. The grid consists of a plurality of light emitters and receivers located on the sides of the screen. Reacts to the blocking of the corresponding rays by objects, on the basis of which it determines the coordinates of pressing.
- Move two fingers together - reduce the image (text)
- Spread two fingers apart - increase (Zoom)
- Movement with 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:
- Ability to make a minimum number of controls
- Simplicity of the GUI
- Ease of control
- Efficiency of access to device functions
- Expansion of multimedia possibilities
However, there are more than enough shortcomings:
- Lack of haptic feedback
- Frequent need to use a pen (stylus)
- Possible screen damage
- 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 the usual keys. But the touch screen is more interactive, thanks to faster access to menu items and settings of modern gadgets.
We hope that this material will help you when choosing a device with a touch screen.
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If you go to a modern mobile phone store and get acquainted with the products offered, then the specifications for most devices in the windows will indicate: "Screen type - capacitive." For those who often change mobile communication devices, this term is well known, but what if a person did not seek to buy everything new, preferring proven solutions?
He can only guess: "Capacitive screen - what is it?"
Data entry technology
The principle of touch typing is now used everywhere. For example, ATMs or machines for making various types of payments, on the panels of which there are a minimum of buttons, and the required numbers are entered by clicking on the corresponding image, can be found in almost every large store. were first proposed back in the seventies, but they did not receive distribution due to the insufficient accuracy of recognition of the pressure zone and the complexity of implementation. But work to improve this solution continued.
Sensors in phones
When models of mobile communication devices with large screens appeared, the question of ergonomics immediately arose. Of course, it was possible to reduce the already small block of buttons, but this would affect the usability in the most negative way. Compromise solutions were used - the so-called "sliders", however, this made the device too thick and made it less reliable due to the need to use a mechanical movable connection. Manufacturers began looking for a solution. And it was found. By that time, they turned out to be significantly improved and ideally suited for phones.
Resisting pressing
The first models of such screens were made according to the resistive principle. Due to a number of features, such sensors are still used today. consists of two completely transparent plates: the outer one, which is pressed, is made flexible, and the inner one, on the contrary, is rigid. The space between them is filled with a transparent dielectric material. A conductive layer is deposited on both plates from the inside by sputtering. It is connected in a special way by conductors to the controller, which constantly supplies low voltage to the layers. All this "sandwich" is fixed on the main display. When a person presses on a section of the screen, the plates touch at a certain point, a current is generated. By determining the resistance values along the two Cartesian axes, it is possible to find out with sufficient accuracy exactly where the pressing occurred. This data is transferred to the running program, which then processes it.
Resistive sensors are inexpensive to manufacture and perform well at low temperatures.
Capacitive screens
Sensors operating on the capacitive principle are much more advanced. Touchpads in laptops are a prime example of such solutions. On foreign sites, in the characteristics of phones with this technology, “Capacity” is indicated. Unlike the resistive solution described above, mechanical pressing is completely irrelevant here. In this case, the property of the human body to accumulate acting as a classical capacitor is used. Capacitive screens are more durable, have excellent "responsiveness". There are two implementation methods: surface and projection. In the first case, a transparent layer of conductive material is applied to the surface of glass or plastic. It constantly has an electric potential from the controller. It is enough to touch the point of the screen with your finger, as the battery leaks into the human body. It can be easily determined, and the coordinates can be transferred to a running program. Projection capacitive screens work differently. Behind the outer glass of the display is a grid of transparent sensor elements (they can be seen at a certain angle and lighting). If you touch the point, then in fact, a capacitor will be formed, one of the plates of which is the user's finger. The capacitance in the circuit is determined by the controller and calculated. This solution allows you to implement the "multi-touch" technology.
