Kinescopic screen. Analysis of electrical monitors. What is cleanliness
Manufacturers of electron-ray tubes have not yet exhausted their potential and as if only trying forces, holding a long time tested in their hands, but is still an expensive component, the technological progress of which is painfully slow in the background of rapidly developing new products. Professional monitors are becoming cheaper, and this fact is undoubtedly very pleased with users who need high quality pictures on the screen. If earlier they preferred only Brand Name monitors (from Sony or ViewSonic) - good, of course, but quite expensive, now there are more and more models on the market, which sometimes even higher characteristics and to save a tangible amount.
How the electron beam tube is arranged
The electron beam tube (CRT; Cathode Ray Tube, or CRT) is the traditional image forming technology at the "bottom" of hermetically sealed glass "bottle". Monitors receive a signal from the computer and convert it into a shape, perceived by an electron-radial cannon located in the "neck" of a huge flask. The gun "shoots" in our side, and the wide bottom (where we, in fact, and look) consists of a "shadow mask" and a luminescent coating on which an image is created. Electromagnetic fields are controlled by a bunch of electrons: the deflecting system changes the direction of the particle stream in such a way that they reach the desired location on the screen, passing through the shadow mask, falling onto the phosphorescent surface and form an image (activated by an electronic beam. The screen sector emits the light visible to the eye; Fig.1 ). This technology is called "emission". The monitor. The monitor is a matrix consisting of nest-triads, a certain structure and form (depending on the specific manufacturing technology - see below). Each such a socket consists of three elements (points, strips or other structures) forming the RGB triad in which the main colors are located as close to each other that individual elements are indistinguishable for the eye.
Thus, the electron beam tubes used in modern monitors have the following main elements:
- electronic guns (one on each color RGB triads or one, but emitting three beams);
- deflecting system, that is, a set of electronic "lenses" forming electron beam;
- a shadow mask that ensures accurate email from the gun of each color in "your" screen points;
- luminofor layer forming the image when the electrons enter the corresponding color point.
With these elements and the continuous struggle of manufacturers for image quality is connected.
The electron cannon consists of a heater, a cathode emitting the flow of electrons, and a modulator, accelerating and focusing electrons.
In modern kinescopes, oxide cathodes are used, in which electrons are emitted by an emission coating of rare-earth elements applied to a nickel cap from the heat thread inside it. The heater ensures the heating of the cathode to a temperature of 850-880 ° C, at which the emitting (emission) of the electrons from the surface of the cathode occurs. The remaining pipe electrodes are used to accelerate and generate electron beam.
Accordingly, each of the three electron guns creates an electron beam to form its color. At the same time distinguish the CRT with deltoid and planar arrangement of guns.
In the case of deltoid arrangement, electron guns are placed in the tops of the equilateral triangle at an angle of 1 ° to the axis of the kinescope.
An error in the value of the angle of inclination should not exceed 1 '. The tilt of the guns is chosen in such a way that the electronic rays intersect at a certain point (point of convergence) and further, refraction to a certain angle, formed a small circle on the mask, within which only one hole of the shadow mask and one RGB triad may be at the same time (three points Luminofor main colors). Accordingly, the luminofor's points are also placed on the vertices of the equilateral triangle, which forms this triad. The center of each hole in the shadow mask is located opposite the axis of the symmetry of this triad of the points of the luminofora.
Electronic rays, diskette after the shadow mask, fall on the points of the luminofor of the corresponding color and make them glow.
Shadow mask
The electronic beam reaches the screen, passing through the shadow mask, which can have a different (point or linear) structure. A shadow mask made of thin alloy sends an electronic beam to a fluorescent material of a certain color.
At the same time, the mask detains 70-85% of all electrons emitted by cathodes, as a result of which it heats up to a high temperature.
Previously, masks were made from iron-based alloys, and with strong heating they were deformed, as a result of which the holes were displaced relative to the fluidophore. To compensate for the displacements, the mask was attached to the screen using the "locks" system from the material with a specially selected coefficient of temperature expansion; When heated, these "locks" moved the mask along the axis of the CRT towards the screen.
In modern models, a shadow mask from Invar is used - a special alloy with a very very coefficient of temperature expansion, so the displacement of masks when heated remains minimal.
In the kinescopes with a planar arrangement of guns, a slot mask is used, and the phosphor of three main colors is applied to the screen in the form of vertical alternating strips in such a way that its RGB triad corresponds to one sliding hole. In such ELT, all three electronic guns are coaxially coaxially located in one vertical plane and tilted at a low angle to the horizontal plane. Such a location largely allows you to compensate for the effects of Earth magnetic field electron beams and simplify the reduction of rays.
Discalcated after the point of convergence, the rays form an ellipse, covering simultaneously only one hole of the slit mask and, accordingly, the three rins of phosphor, respectively. The hole of the slit mask is located opposite the middle (green) strip of the phosphor.
The ratio of the area of \u200b\u200bholes to the total mask area in electron-radial tubes of this type is significantly higher than that of the shadow mask, therefore the same brightness of the glow can be achieved with a significantly lower power of electron beams and, therefore, the service life of such kinescopes is significantly larger.
Monitor screen
Upon reaching the surface of the screen, the beam interacts with it, while the electron energy is converted into light. The screen is a glass surface with special optical properties, on which a special phosphorescent material is sprayed. High quality image is achieved correctly choosing materials and technology. The phosphorescent material should provide the required energy efficiency, resolving the ability, durability, accurate color reproduction and afterglow.
Anti-reflective panel (AR Panel)
Special anti-glare panels are used to minimize the reflective screen properties. Not worsening images, they weaken glare, as well as reduce the electromagnetic radiation of the monitor. However, due to the high cost of such panels, they are used in expensive monitors with a large resolution, for example in 21-inch. Recently, instead of an anti-glare panel on monitors with a diagonal of 21 inches and less use an anti-reflective coating. Such a coating, like the panel, limits the radiation in accordance with the TSO standards. New technologies allow you to go to the commercial use of monitors with anti-reflective coating.
Antistatic coating
Antistatic screen coating is provided by spraying a special chemical composition to prevent the accumulation of electrostatic charge. It is required in accordance with a number of safety and ergonomics standards, including MPR II.
Sensual monitor
The ratio of useful light energy pasted through the front glass of the monitor, to the emitted inner phosphorescent layer is called the lighting coefficient. As a rule, the darker it looks like the screen when the monitor is turned off, the lower this coefficient. With a high freight ratio to ensure the desired brightness of the image, a small level of video signal is required and schematic solutions are simplified. However, the difference between the radiating sites and adjacent, which entails the deterioration of clarity and decrease the contrast of the image and, as a result, deterioration of its overall quality. In turn, at a low light ratio, the image focus and color quality improves, however, a powerful video signal is required to obtain sufficient brightness and the monitor scheme is complicated. Usually 17-inch monitors have a light ratio of 52-53%, and 15-inch - 56-58%, although, depending on the specifically selected model, these values \u200b\u200bmay vary. Therefore, if necessary, the exact value of the transmission coefficient should be referred to the manufacturer's documentation.Horizontal scan
The time of horizontal movement of the beam from the left to the right edge of the screen is called a horizontal scanning period. The value is inversely proportional to this period, called the horizontal sweep frequency, or simply the horizontal scan (sometimes there are the "LCD frequency", or "string frequency"), and is measured in kiloherts (kHz). For example, for a monitor with a resolution of 1024 x 768 pixels, the horizontal scan is inversely proportional to the time for which the ray scans 1024 pixels. With an increase in the resolution during the same period of time, a larger number of pixels should be scanned. With increasing frame rate, the frequency of the horizontal sweep should also be increased.
Vertical scan, or frame rate
The monitor with an electronic radial tube updates the image on the screen dozens once a second. This number is called the frequency of the vertical sweep, or the frequency of the screen update, and is measured in Hertz (Hz).
The 60 Hz vertical scan monitor has a flicker frequency as daylight lamp in the US (somewhat higher than in Europe, where the frequency of the network 50 Hz). Usually at frequencies above 75 Hz flickering imperceptibly for the eye (no flicker mode). The standard VESA recommends working at a frequency of 85 Hz, considering it an important consumer indicator of the monitor ergonomics.
The horizontal sweep frequency calculation based on the frame rate: horizontal scan \u003d (row number) x (vertical sweep) x 1.05. For example, the desired horizontal scan with a vertical frequency of 85 Hz and a resolution of 1024 x 768 is: 768 x 85 x 1.05 \u003d 68 500 Hz \u003d \u003d 68.5 kHz.
Resolution
Resolution characterizes the quality of the image playback by the monitor. To obtain high resolution, first of all, the qualities must be a video signal. Electronic chains should process it in such a way as to ensure the correct levels and combinations of focusing, color, brightness and contrast. The resolution is characterized by the number of points, or pixels (DOT) by the number of strings (Line). For example, a monitor resolution of 1024 x 768 means the ability to distinguish up to 1024 points horizontally with the number of rows up to 768.
Pixel frequency
For example, if a horizontal resolution of 820 points, and the period of displaying data horizontally 10.85 ns \u003d 10.85 x 10-6 s, then the pixel frequency is required (Pixel Rate) about 76 MHz. A high-resolution monitor can display 24 times more information, rather than television.
Contrast, uniformity
Contrast characterizes the brightness of the screen compared to the dark zone in the absence of a video signal. Contrast can be adjusted by adjustment "Strengthening", affecting the input video signal.
Under uniformity it is understood as the constancy of the level of brightness over the entire surface of the monitor screen, which provides the user with comfortable conditions for work. Temporary non-uniformity of color can be eliminated by the screening of the screen. It is customary to distinguish the "uniform distribution of brightness" and "white uniformity".
Minimal: Static, Dynamic
To obtain a clear image and clean colors on the monitor screen, red, green and blue rays, emanating from all three electron guns, should fall into exactly the specified location on the screen. The term "non-ray exchange" means the deviation of red and blue from the centering green.
Under static disreglating it is understood to disregard three colors (RGB), the same on the entire surface of the screen caused by a slight error when assembling an electron gun. The image on the screen can be corrected by adjusting static information.
While in the center of the monitor screen, the image remains clear, in its edges there may be unloaded. It is called errors in windings or when they are installed and can be eliminated by magnetic plates.
Dynamic focus
Electronic beam, unless special measures are taken, defocivers (increase in diameter) as it removes it from the center of the screen. To compensate for distortion, a special compensating signal is formed. The value of the compensating signal depends on the properties of the CRT and its deflecting system. To eliminate the focus offset caused by the difference in the pathways of the beam (distance) from the electron beam gun to the center and to the edges of the screen, it is necessary to increase the voltage with increasing the beam deviation from the center using a high-voltage transformer, as shown in Fig. four.
Purity images
The purity and clarity of the image is achieved when each of the RGB electronic rays falls on the screen surface in a strictly defined point. From here it follows that the verified relationship is required between the electron gun, the holes of the shadow mask and the points of the phosphorescent surface (phosphor) of the screen. The impaired purity and clarity of the image may be due to the following reasons:
- anointing electron gun or beam offset;
- displacement of the center of the gun forward or backward;
- deviation of the beam caused by the influence of external magnetic fields, including the magnetic field of the Earth.
Flicker
Monitor is characteristic of flicker. It is due to the fact that after a certain time expires, weakening the radiation of light by phosphorus occurs. To maintain the glow, the screen should be susceptible to the periodic exposure to the beam from the electron beam tube. The flicker becomes noticeable if the time interval between the impacts is too large or the time for the afterglow of the phosphorescent substance of the screen.
The effect of flicker may also be exacerbated by a bright screen and a large angle of view to it. Eliminating the flickering as the problem of ergonomics recently pays more attention - the flickering of the screen is thus becoming a key commercial indicator of the goods. Reducing decrease is achieved by increasing the frequency of regeneration (update) of the screen at each resolution level. The VESA standard recommends using a frequency of at least 85 Hz.
Jitter (Jitter)
The image shake occurs due to high-frequency vibrations of the holes of the monitor mask caused by both network mutual influence, video, displacement, microprocessor chain control block, and incorrect grounding organization. The term "jitter" refers to oscillations with frequencies above 30 Hz. At frequencies from 1 to 30 Hz, the term "swimming" is often used, and below 1 Hz - "Draif". Shivels in one degree or another are characterized by all monitors. Although minor trembling can remain unnoticed for the user, it still causes the eye fatigue and must be adjusted. In part 3 ISO 9241 (orders for ergonomics), a diagonal deviation of a point of no more than 0.1 mm is allowed.
Classification of Mask Type Monitors
Modern monitors with any mask have a practically flat form of the screen, due to which the distortion of geometry is significantly reduced, especially in the corners. Therefore, the type of mask on the shape of the screen is not so simple.
To date, three main technologies for the formation of matrices and masks for RGB-triad are used in the ELT displays:
- three-point shadow mask (Dot-Trio Shadow-Mask CRT);
- slit Aperture Grating (Aperture-Grille CRT);
- nest mask (Slot-Mask CRT).
Manufacturers of various models talk about the great advantages of precisely their technology, but the fact that several models are offered on the market and, moreover, many manufacturers of monitors produce models with various types of matrices, shows that the unambiguous choice does not happen. Preferences are defined only by the tastes of the user and its tasks.
CRT monitors with a three-point shadow mask
The oldest and widely used technology with the so-called shadow mask uses a perforated metal plate placed in front of the luminophore. It masks three separate beams, each of which is controlled by its own e-gun. The masking ensures the necessary concentration of each beam and provides it only to the desired color of the phosphor. However, the practice shows that none of the monitors ensures the perfect implementation of this task over the entire surface of the screen.
Early ELT-displays with a shadow mask had a pronounced curvilinear (spherical) surface. This allowed to achieve better focus and reduced unwanted effects and deviations caused by heating. Currently, most professional and specialized monitors have a practically flat rectangular screen (type FST).
Monitors with a shadow mask have their advantages:
- the text looks better (especially with a small amount of points);
- colors "natural" and more accurate (which is especially important for computer graphics and in printing);
- the debt technology provides a better value ratio and performance.
Of the disadvantages, you can note the smaller brightness of such monitors, insufficient image contrast and a shorter service life, compared with other types of displays.
ETT monitors with a slit aperture grid
The new CRT-displays manufacturing technology is with an aperture grid instead of a traditional point mask - for the first time, Sony was offered, having released monitors with TRINITRON tube. In the electron guns of these tubes, dynamic quadrupole magnetic lenses are used, allowing to form a very thin and precisely directed electron beam.
Due to this solution, astigmatism is significantly reduced - the dispersion of the electron beam, leading to insufficient sharpness and contrast of the image (especially horizontally). But the main difference from technology with the shadow mask here is that instead of a metal plate with round holes that performs the mask function, a vertical wire mesh (aperture grille) is used here and the phosphor is not applied in the form of points, but in the form of vertical strips.
Aperture grid monitors have the following advantages:
- in the thin grid, less metal, which allows the use of more energy of electrons to the reaction with the phosphor, and therefore, it is less dissipated on the lattice and goes into heat;
- the increased area of \u200b\u200bthe coating with the phosphor allows to increase the brightness of the radiation at the same intensity of the electron beam;
- due to a significant general increase in brightness, you can use a darker glass and receive a more contrast image on the screen;
- the monitor screen with a aperture lattice is flatter than that of the displays with the shadow mask, and in the last models it is not even cylindrical, as before, and almost absolutely even, which is much more convenient in operation and reduces the amount of glare and reflections.
From the disadvantages, only "unpleasant" horizontal threads can be noted - the limiters used in such monitors to give the wire mesh additional rigidity. Although the wires in the aperture lattice are tightly stretched, during operation they can vibrate under the influence of electron beams. The damper thread (and in large-sized screens - two threads) serves to reduce oscillations and vibration damping. According to these threads, monitors with TRINITRON tube can be distinguished from other models. In addition, if during the operation of such a monitor it is slightly swing, the fluctuations of the image will be visible even with the naked eye. That is why monitors with these tubes are not recommended to put on Desktop system blocks.
It remains to add that in the Sony Trinitron electron-ray tubes, a system of three beams of electrons emitted by one cannon is used, and in the tubes with a similar aperture lattice of Mitsubishi - Diamondtron - a system of three rays with three cannons.
CRT monitors with a nesting mask
And, finally, the last, combined type of electron beam tube, the so-called CromaClear / Opticlear (first proposed by the NEC) is a variant of the shadow mask, in which there are not round holes, but slits, as in an aperture lattice, only short - "dotted line ", And the phosphor is applied in the form of the same elliptic strips, and the nests thus obtained for greater uniformity are located in the" chess "order.
Such a hybrid technology allows you to combine all the advantages of the above-described types in the absence of their shortcomings. Clear and clear text, natural, but rather bright colors and high contrast of the image invariably attract all user groups to these monitors.
The article uses some materials from the Russian-speaking Web site of Samsung Electronics (http://www.samsung.ru).
ComputerPress 5 "2000
The personal computer monitor is a truly important component for each type of computer.
Without a monitor, there is no possibility to assess fully characteristics, as well as functions, the capabilities of the software provided, because no type of information will be displayed visually. Only through the monitor used can be obtained up to 100% of information.
Currently, monitors with an electron beam tube ceased to be conventional and common. Such technique can be seen only from rare users. ELT successfully replaced liquid crystal monitors.
Despite this situation, there is a need to understand all important advantages and nuances of manufactured equipment, because in this case it is possible to appreciate the former products and understand why it has lost the relevance. Is the reason only lies in large dimensions and excessively significant weight, high power consumption and potentially harmful emission for users? 
What were the previous CRT monitors?
All CRT monitors can be divided into three types.
- Electron-rays monitors with a shadow mask. This option turned out to be one of the most popular and truly worthy of manufacturers. The technique possessed a convex monitor.
- LT with an aperture grid, which includes several vertical lines.
- Monitors with a slit mask.
What specifications of the ELT monitors need to be taken into account? How to figure out how much the technique of its application is?
- Screen diagonal. This parameter is considered from opposite angles from the upper and lower part: the lower right angle is the left upper. The value must be measured in inches. In most cases, the models have a diagonal of 15 and 17 inches.
- Screen Grain Size Monitorbut. In this case, it is assumed to consider special holes located in the monitor flowheling mask at certain distances. If this distance turns out to be less, you can count on improving image quality. The size of the grain should indicate the distance between the nearest holes. For this reason, you can navigate the following indicator: a smaller characteristic is the proof of high quality computer display.
- Power consumptionb, measured in W.
- Display coverage type.
- Presence or absence of a protective screen. Scientists managed to prove that radiation produced is harmful to human health. For this reason, the ELT monitors began to be offered with special protection, which can be glass, film, grid. The main task was the desire to reduce the level of radiation.
Advantages of CRT Monitors
Despite the features and specifics of the monitors, the possibility of assessing the advantages of the previous products offered:
- ELT models can operate with switching (gate) stereo. At the same time, even the most advanced LCD displays did not acquire such skills. If a person dreams of note how multifaceted and perfect can be a full-fledged 3D stereo video, it is best to give the preference of the CRT model, which will be 17-inch. With this approach to the purchase, you can allocate 1500 - 4500 rubles, but you can get the opportunity to enjoy from 3D in switching stereoons. The most important thing is to check this, focusing on the passport details of the released technology, its characteristics: permission should be 1024x768. Personnel frequency sweep - from 100 Hz. If this data is not met, the risk of flickering of stereo imagery appears.
- CRT monitor When installing a modern video card can successfully display images of various permissions, including thin lines and inclined letters. This characteristic depends on the resolution of the phosphor. The LCD display will correctly and qualitatively play the text only if the resolution setting is equal to the number of rows and columns of the LCD monitor itself, standard permission, because other versions will be interpolated by electronics used by the technique.
- High-quality CRT monitors can please dynamic (transient) characteristics to enjoy the observation of dynamically changing plots in games and films. It is assumed to be able to successfully and easily eliminate the unwanted grease from the details of the image that change quickly. This can be explained by the following nuance: the transitional response time in the phosphor of the ELT cannot exceed 1 - 2 ms by the decay criterion of full brightness to a few percent. The LCD displays have a transition response of 12-15 ms, and 2, 6, 8 ms are a purely advertising trick, as a result of which in dynamic plots there may be a lubricant of fast-mounted parts.
- CRT monitors that meet high criteria and properly configured by colors can guarantee the correct color transmission of the observed scenes. Artists and designers appreciate this characteristic. LCD monitors can not please the perfect color transmission.
Disadvantages of ELT monitors
- Large dimensions.
- High power consumption.
- The presence of harmful electromagnetic radiation.
Perhaps LCD displays according to its technical characteristics and catch up with CRT, because modern manufacturers try to combine convenience and practicality, functionality in the proposed products.
Let's talk about monitors - LCD and CRT, about what is better. Previously, when there were still black and white convex monitors - then work at the computer for the eyes was always unsafe. But now the time has changed and the progress of monitors is visible with the naked eye.
Today, the monitors have already changed very much, they became completely different - the LCD monitors came to the change of ELT, they are not large compared to CRT and on the table no longer occupy a huge place. And also they consume less electricity. But what is better today, CRT or LCD? Ordinary users of the choir will answer that the LCD, but is it really?
The monitor, as much in this word, often we just look at it more time than your relatives or children, so unfortunately to the selection of the monitor it is necessary to approach very seriously and responsibly.
CRT or electron beam tube
CRT monitor is a glass tube, which is filled with vacuum. The frontal part of the monitor is the phosphor. For phosphor, complex compositions based on rare earth metals, such as Yttria, Erbia. If simple words, the phosphor is a substance that forms light when charged particles are supplied. So that the ELT monitor displays the image, the electron gun is used, it passes the flow of electrons through a metal mask (grid) on the inner surface of the monitor glass screen, which is covered with multi-colored phosphor points.
If you take a new CH type monitor for example, of course it will show very well (if necessary, the image can be adjusted). The monitor has one strong side that only expensive LCD is a color rendition. No matter how cool, but Elt has it much better than the LCD. Only IPS matrices in the LCD monitors can be equal to the color reproduction of the CRT.In conventional electrical monitors, three electronic guns are used, when only one was involved in the old, still black and white.
The human eye can only react on three main colors, it is red, blue and green and on their combinations, they create a huge number of colors or shades. The front part of the monitor is a luminophore, or rather its layer, and it consists of points - so small that they are almost impossible to see. It is they who in the literal sense reproduce the main colors of RGB.
RGB (Red, Green, Blue) is an additive color model that describes the color synthesis method for color-playback.
In addition to the electron beam tube, electronics are also present, with which the incoming signal is processed from the computer video card. The electronics is engaged in optimizing the displayed image - enhances the signal and stabilizes, that is why the picture is stable on the monitor, even if the signal is unstable.
The disadvantage of Elt monitors is that they are harmful to the eyes, and also take a lot of light. And at the same time, over time, they are nervous, today it is almost not to find the monitor of the CRT which shows how the LCD, and if he is also more than 17 inches, then his "mitigation" will be noticeable immediately.LCD or liquid crystal monitors
Liquid crystals on which LCD monitors are based, the characteristics of the substance between solid and liquid, and the crystalline structure of molecules is preserved and the fluidity is provided. The matrix of such a monitor is indeed in a sense of liquid, for example, if you easily push your finger over a working monitor, then you will see how the liquid is displaced, which is inside. This is a liquid crystal solution. At first, liquid crystals were used in the displays of calculators, as well as digital clock, then switched to PDAs and computers monitors.
Today it is not almost almost, but completely elite is ousted by LCD monitors.
LCD - these are two panels, they are made of very thin and pure glass (substrate), between these panels - a thin layer of liquid crystals (called pixels), they are involved in building an image. Unlike Elt monitors, the LCD has such a concept as "native" permission is the on which the monitor is preferably worked. It is such an extension will allow the monitor to bring the picture the most qualitatively. If you set another extension, the image will be either elongated (sharpness deteriorates, there are small distortions), or vice versa - the extension will be changed, but part of the screen will be filled with black to keep quality.
The contrast of monitors is determined by the ratio of brightness between white (as the brightest) and black (the darkest) color. Good indicator - 120: 1. Accurately, halftone is capable of giving monitors with a contrast of 300: 1.
Comparison of LCD and CRT
LCD monitors are good because they are completely flat, the picture is clearer than that of the electrical monitor, and the saturation of the color can also be higher. There are no distortions, as well as the eternal problem of "soap" (muddy image) - all this is missing from the "thin" monitors than they go ahead of the CRT.
Here is an additional information about the difference in monitors, but it is interesting that the picture is a little muddy, blurred, that's it now, many CRT monitors are shown (since new ones do not produce older):
Therefore, it is possible to draw conclusions that the LCD monitor is better, and CRT did not just go into the past, but if you have the opportunity, buy an expensive monitor, they are less harmful to the eye during a long-term work at the computer.
Here you note. Many 15-inch LCD monitors in a running mode are consumed about 20-40 watts (in standby mode less than 5 watts), you can compare it with a 17-inch CRT monitor, which in operation consumes from 90 to 120 watts (in standby mode - 15 watts). Can you imagine? I still consider you - if the monitor is working for about eight hours a day and so the entire working week, then a year 17-inch CRT will consume 300 kW, it considers the standby time per hour or two, while 15 inches LCD - 60 kW (17 inches I do not think that it will be much more). This is the little things for you, but if the company has a hundred, two hundred, three hundred, that is, the reason to think about the new type of monitor.But there are also strengths of the ELT monitors, as a rule, they are interesting in large part of the designers - color reproduction. If you work for a while for the LCD, and then look at the CRT, then you will notice the difference between the color reproduction and the volume of the image.
ETT monitor design
Most of the monitors used and manufactured are built on electronic radial tubes (CRT). In English - Cathode Ray Tube (CRT), literally - cathode-ray tube. Sometimes CRT is decrypted as Cathode Ray Terminal, which is no longer the tube itself, and the device is based on it. The electron beam technology was developed by the German scientist Ferdinand Brown in 1897 and was originally created as a special tool for measuring AC, that is, for an oscilloscope. Electron beam tube, or a kinescope, is the most important element of the monitor. The kinescop consists of a hermetic glass flask, inside which vacuum is located. One of the ends of the flask is narrow and long - this is a neck. The other is wide and fairly flat - screen. The inner glass surface of the screen is covered with a luminophore (Luminophor). As phosphors for color ELT, rather complex compositions based on rare earth metals are used - Yttria, Erbia, etc. The phosphor is a substance that, with the bombardment of charged particles, emits light. Note that sometimes phosphorus is called phosphorus, but it is not true, since the phosphor used in the coating of the CRT has nothing to do with phosphorus. Moreover, phosphorus glows only as a result of interaction with air oxygen when oxidation to P2O5, and the price lasts very long (by the way, white phosphorus is a strong poison).
To create an image in the ELT monitor, an electronic gun is used, from where the electron flow occurs under the action of a strong electrostatic field. Through the metal mask or grille, they fall on the inner surface of the monitor glass screen, which is covered with multi-colored luminophore dots. The flow of electrons (beam) can be deviated in the vertical and horizontal plane, which ensures the sequential hit on the entire screen field. The rejection of the beam occurs through a deflecting system. Deviation systems are divided into saddot-toroidal and saddot. The latter is preferable because the low level of radiation is called.
The deflection system consists of several inductance coils placed at the kinescope neck. Using an alternating magnetic field, two coils create a deviation of the electron beam in the horizontal plane, and the other two are in the vertical. The change in the magnetic field occurs under the action of alternating current flowing through coils and varying on a specific law (this is usually a sawdust voltage change in time), while the coils give the beam the right direction. Solid lines are the active move of the beam, the dotted line.
The frequency of transition to a new line is called the frequency of the lowercase (or horizontal) sweep. The frequency of the transition from the lower right angle to the left upper is called the frequency of vertical (or personnel) sweep. The amplitude of overvoltage pulses on the string coils increases with the frequency of strings, so this node turns out to be one of the most intense design places and one of the main interference sources in a wide frequency range. The power consumed by the bottom scan nodes is also one of the serious factors taken into account when designing monitors. After the deflection system, the flow of electrons on the path to the front part of the tube passes through the intensity modulator and the accelerating system operating on the principle of potential difference. As a result, the electrons acquire greater energy (E \u003d MV2 / 2, where E-energy, M mass, V-speed), part of which is consumed on the luminosity of phosphor.
The electrons fall into the phosphoric layer, after which the electron energy is transformed into light, that is, the flow of electrons causes the points of the phosphor to glow. These luminous points of the phosphora form the image that you see on your monitor. As a rule, three electronic guns are used in the color CRT monitor, in contrast to one gun used in monochrome monitors, which are now practically not performed.
It is known that the person's eyes react to the main colors: red (Red), green (green) and blue (Blue) and on their combinations that create an infinite number of colors. The luminophore layer covering the front of the electron beam tube consists of very small elements (so small that the human eye can not always distinguish them). These phosphor elements reproduce the main colors, in fact there are three types of multi-colored particles, whose colors correspond to the main colors of the RGB (hence the name of the group from the luminophore elements - triads).
Luminofor begins to glow, as mentioned above, under the influence of accelerated electrons, which are created by three electron guns. Each of the three guns corresponds to one of the main colors and sends a beam of electrons to various phosphor particles, whose glow the main colors with different intensity is combined and the result is formed with the desired color. For example, if you activate red, green and blue phosphor particles, then their combination will form white color.
To control the electron beam tube, control electronics is also necessary, the quality of which largely determines the quality of the monitor. By the way, it is the difference as a control electronics created by different manufacturers, is one of the criteria for determining the difference between monitors with the same electron beam tube.
So, each gun emits an electronic beam (or flow, or a beam) that affects the luminophore elements of different colors (green, red or blue). It is clear that the electronic beam, intended for red luminophore elements, should not affect the phosphor of green or blue. To achieve such actions, a special mask is used, whose structure depends on the type of kinescopes from different manufacturers, providing discreteness (bit) of the image. CRT can be divided into two classes - three-beam with a delta-like arrangement of electron guns and with a planar arrangement of electron guns. In these tubes, slotted and shadow masks are applied, although it is more correct to say that they are all shadow. At the same time, the tubes with a planar arrangement of electron guns are also called kinescopes with rays, as the effect of the magnetic field of the Earth into three planarly located beams is almost the same and when the position of the tube is changed relative to the Earth field, no additional adjustments are required.
Types of ELT
Depending on the location of electron guns and the design of the flourishing mask, the ELT of the four types used in modern monitors are distinguished:
CRT with shadow mask (Shadow Mask)
CRT with a shadow mask (Shadow Mask) is most common in most monitors produced by LG, Samsung, Viewsonic, Hitachi, Belinea, Panasonic, Daewoo, Nokia. Shadow Mask - the most common type of masks. It is used since the invention of the first color kinescopes. The surface of the kinescopes with the shadow mask is usually spherical (convex). This is done in order for the electronic beam in the center of the screen and at the edges of the same thickness.
A shadow mask consists of a metal plate with round holes that occupy approximately 25% of the area. There is a mask in front of a glass tube with a luminous layer. As a rule, most modern shadow masks are made from Invar. Invar - magnetic iron alloy (64%) with nickel (36%). This material has an extremely low coefficient of thermal expansion, therefore, despite the fact that the electronic rays heat the mask, it does not have a negative effect on the purity of the color of the image. The holes in the metal grid work as a sight (although not accurate), it is precisely that the electronic beam enters only the required phosphor elements and only in certain areas. The shadow mask creates a grid with homogeneous dots (more called triads), where each such point consists of three luminous elements of the main colors - green, red and blue, which are glowing with different intensity under the influence of rays from electron guns. By changing the current of each of the three electronic rays, you can achieve arbitrary color of the image element formed by triad points.
One of the weak places of monitors with the shadow mask is its thermal deformation. In the figure below, as part of the rays from the electron beam gun falls on the shadow mask, as a result of which heating and the subsequent deformation of the shadow mask occurs. What is happening the displacement of the shadow mask holes leads to the effect of the screenshot effect (RGB color displacement). A material mask material has a significant impact on the quality of the monitor. The preferred mask material is Invar.
The disadvantages of the shadow mask are well known: first, it is a small ratio of the transmitted and delayed mask of electrons (only about 20-30% passes through the mask), which requires the use of phosphors with a large light output, and this in turn worsens the monochridity of the glow, reducing the color reproduction range , And secondly, to ensure the exact coincidence of the three rays that are not lying in the same plane with their deviation to large angles are quite difficult. The shadow mask is used in most modern monitors - Hitachi, Panasonic, Samsung, Daewoo, LG, Nokia, ViewSonic.
The minimum distance between the luminophore elements of the same color in the adjacent lines is called dot pitch and is an image quality index. Pitch points are usually measured in millimeters (mm). The smaller the step of the point, the higher the quality of the image playing on the monitor. The distance between two adjacent points horizontally equal to the point of points multiplied by 0.866.
CRT with an aperture grill of vertical lines (Aperture Grill)
There is another type of tubes that use Aperture Grille (aperture grille). These tubes have become known under the name TRINITRON and for the first time were presented on the market by SONY in 1982. In the tubes with an aperture grid, an original technology is used, where there are three radial guns, three cathodes and three modulators, but there is one common focus.
Aperture grille is a type of mask used by different manufacturers in its technologies for the production of kinescopes weighing different names, but the same in essence, for example, Tinitron technology from Sony, Diamondtron from Mitsubishi and Sonictron from ViewSonic. This solution does not include a metal lattice with holes, as in the case of a shadow mask, and has a grid of vertical lines. Instead of points with luminophore elements of the three main colors, the aperture grille contains a series of threads consisting of the phosphor elements of three main colors built in the form of vertical bands. Such a system ensures high contrast of the image and good saturation of colors, which together provides high quality monitors with tubes based on this technology. The mask used in the Sony tubes (Mitsubishi, ViewSonic) is a thin foil, on which thin vertical lines are protruded. It keeps on a horizontal (one in 15 ", two in 17", three or more in 21 ") a wire, a shadow from which is visible on the screen. This wire is used to quench the oscillations and is called Damper Wire. It is clearly visible, especially with a light background Images on the monitor. Some users do not like these lines, other on the contrary are satisfied and used as a horizontal line.
The minimum distance between the luminophore strips of the same color is called a strip pitch (Strip Pitch) and is measured in millimeters (see Fig. 10). The smaller the steps of the strip, the higher the image quality on the monitor. On an aperture lattice, it only makes sense horizontal point size. Since the vertical is determined by the focusing of the electron beam and the deflecting system.
CRT with a slot mask (Slot Mask)
A slot mask (Slot Mask) is widely used by NEC under the name "Cromaclear". This decision in practice is a combination of a shadow mask and aperture lattice. In this case, the luminophore elements are located in vertical elliptic cells, and the mask is made of vertical lines. In fact, the vertical bands are divided into elliptical cells that contain groups of three luminophore elements of the three main colors.
A slit mask is used, in addition to the NEC monitors (where the cells are elliptical), in Panasonic monitors with a PureFlat tube (previously called PANAFLAT). Note that it is impossible to directly compare the step size for the tubes of different types: a step of points (or triads) tubes with a shadow mask is measured diagonally, while the step of a aperture lattice, otherwise called the horizontal pitch of the points, is horizontally. Therefore, with the same step of points, the tube with the shadow mask has a greater density of points than a tube with an aperture grid. For example, the pitch of the bands is 0.25 mm is approximately equivalent to the step of points equal to 0.27 mm. Also in 1997 by Hitachi - the largest designer and manufacturer of the ELT - was developed by EDP - the newest technology of the shadow mask. In a typical shadow mask, the triads are placed more or less equilaterally, creating triangular groups that are uniformly across the inner surface of the tube. Hitachi reduced the distance between the elements of the triad horizontal, thereby creating triads, closer in shape to an equally-aided triangle. To avoid gaps between the triads, the points themselves were elongated, and are rather ovals than a circle.
Both types of masks - a shadow mask and an aperture lattice - have their advantages and their supporters. For office applications, text editors and spreadsheets, more suitable kinescopes with a shadow mask, providing very high clarity and sufficient contrast of the image. To work with raster and vector graphics packages, tubes with aperture grille are traditionally recommended, which are characterized by excellent brightness and contrast of the image. In addition, the working surface of these kinescops is a cylinder segment with a large radius of curvature horizontally (as opposed to CRT with a shadow mask having a spherical surface of the screen), which is essential (up to 50%) reduces the intensity of highlights on the screen.
The main characteristics of the ETT monitors
Monitor screen diagonal
The diagonal of the monitor screen is the distance between the left lower and the upper left corner of the screen, measured in inches. The size of the visible screen of the screen area is usually slightly smaller, on average per 1 "than the size of the tube. Manufacturers may indicate in the accompanying documentation two sizes are diagonally, and the visible size is usually indicated in brackets or marked" Viewable Size ", but sometimes only one is indicated. Size - the size of the diagonal of the tube. Monitors with a diagonal 15 "were highlighted as a standard for PC, which roughly corresponds to 36-39 cm diagonally visible area. To work in Windows, it is desirable to have a monitor size of at least 17. For professional work with desktop publishing systems (NIS) and automated design systems (CAD), it is better to use a 20 "or 21) monitor.
Screen grain size
The grain size of the screen determines the distance between the nearest holes in the flowheeling mask of the type of type. The distance between the mask holes is measured in millimeters. The smaller the distance between the holes in the shadow mask and the more these holes, the higher the image quality. All grain monitors are more than 0.28 mm refer to the category of rough and cost cheaper. The best monitors have a grain of 0.24 mm, reaching 0.2 mm in the most expensive models.
Resolution monitor
The resolution of the monitor is determined by the number of image elements that it is capable of playing horizontally and vertical. Monitors with screen diagonal 19 "support resolution up to 1920 * 14400 and higher.
Power consumption monitor
Screen covering
Screen coverings are needed to give it anti-glare and antistatic properties. The anti-reflective coating allows you to watch on the monitor screen only an image generated by a computer, and do not hinder the eyes by observing reflected objects. There are several ways to produce an anti-glare (non-reflective) surface. The cheapest of them is etching. It gives surface roughness. However, the graphics on such a screen looks nonresko, the image quality is low. The most popular method of applying a quartz coating, scattering falling light; This method is implemented by Hitachi and Samsung firms. Antistatic coating is necessary to prevent sticking to the dust screen due to static electricity accumulation.
Protective Screen (Filter)
The protective screen (filter) must be an indispensable attribute of the ELT monitor, since medical studies have shown that radiation containing rays in a wide range (X-ray, infrared and radio emission), as well as electrostatic fields accompanying the monitor operation, can very negatively affect human health .
By manufacturing technology, protective filters are: grid, film and glass. Filters can be attached to the front wall of the monitor, hang on the top edge, insert into a special groove around the screen or put on the monitor.
Grid filters
Net filters are practically not protected from electromagnetic radiation and static electricity and somewhat deteriorate the contrast of the image. However, these filters looked good glare from external lighting, which is important when working with a computer.
Filter filters
Film filters are also not protected from static electricity, but significantly increase the contrast of the image, almost completely absorb ultraviolet radiation and reduce the level of X-ray radiation. Polarization film filters, such as POLAROID, are able to rotate the polarization plane of the reflected light and suppress the appearance of glare.
Glass filters
Glass filters are produced in several modifications. Simple glass filters remove the static charge, low-frequency electromagnetic fields weaken, reduce the intensity of ultraviolet radiation and increase the contrast of the image. Glass filters Categories "Full Protection" have the highest set of protective properties: practically do not give glare, increase the contrast of the image in one and a half or two times, eliminate the electrostatic field and ultraviolet radiation, significantly reduce the low-frequency magnetic (less than 1000 Hz) and X-rays. These filters are made of special glass.
Pros and cons
|
Legend: (+) Dignity, (~) Admissible, (-) Failure |
||
| LCD monitors
| Elt monitors
|
|
| Brightness | (+) from 170 to 250 cd / m2 | (~) from 80 to 120 kD / m2 |
| Contrast | (~) From 200: 1 to 400: 1 | (+) from 350: 1 to 700: 1 |
| Viewing angle (in contrast) | (~) from 110 to 170 degrees | (+) Over 150 degrees |
| Viewing angle (in color) | (-) from 50 to 125 degrees | (~) Over 120 degrees |
| Resolution | (-) One permission with a fixed size of pixels. Optimally can only be used in this resolution; Depending on the supported extension or compression functions, you can use a higher or lower resolution, but they are not optimal. | (+) Different resolutions are supported. With all supported resolution, the monitor can be used optomically. The restriction is imposed only by the acceptability of the frequency of regeneration. |
| Frequency of vertical sweep | (+) The optimal frequency of 60 Hz, which is DOS-CATCO for lack of flicker | (~) Only at frequencies of more than 75 Hz is obviously noticeable flicker |
| Combining errors Flowers | (+) No | (~) from 0.0079 to 0.0118 inches (0.20 - 0.30 mm) |
| Focusing | (+) Very good | (~) From satisfactory to very good\u003e |
| Geometric / linear distortion | (+) No | (~) possible |
| Non-working pixels | (-) to 8 | (+) No |
| Input signal | (+) analog or digital | (~) Only analog |
| Scaling for different resolutions | (-) There is no interpolation methods that do not require large overhead costs. | (+) Very good |
| Color display accuracy | (~) True Color is supported and imitating the desired color temperature | (+) True Color is supported and at the same time there is a mass of color calibe devices, which is a certain plus |
| Gamma correction (adjustment of colors under the features of human view) | (~) satisfactory | (+) photorealistic |
| Uniformity | (~) Often the image brighter around the edges | (~) Often the image brighter in the center |
| Color Clean / Color Quality | (~) Good | (+) high |
| Flicker | (+) No | (~) imperceptibly at frequency above 85 Hz |
| Time inertia | (-) From 20 to 30 ms. | (+) dismissively small |
| Image formation | (+) The image is formed by pixels, the number of which depends only on the specific permission of the LCD panel. The pixel step depends only on the size of the pixels themselves, but not from the distance between them. Each pixel is formed individually, which provides excellent focus, clarity and clarity. The image is obtained more holistic and smooth. | (~) Pixels are formed by a group of points (triads) or strips. The point of the point or Lii depends on the distance between the dots or lines of the same color. As a result, the clarity and clarity of the image strongly depends on the size of the point or step of the line and the quality of the CRT |
| Power consumption and radiation | (+) There are practically no dangerous electromagnetic emissions. The level of energy consumption is about 70% lower than that of standard CRT monitors (from 25 to 40 W). | (-) Electromagnetic radiation is always present, but their level depends on whether CRT corresponds to any standard of security. Energy consumption in working condition at 60 - 150 W. |
| Sizes / weight | (+) flat design, low weight | (-) Heavy construction, takes a lot of space |
| Monitor interface | (+) Digital interface, however, most LCD monitors have a built-in analog interface for connecting to the most common analog outputs of video adapters | (-) Analog interface |
Hello, my blog readers who are interested in the monitor. I will try to make this article to be interested in everything, and those who have no longer found them, and those who have this device are pleased with the first experience of mastering a personal computer.
Today, PC displays are flat and thin screens. But in some low-budget organizations, massive kinescopic monitors can be found. The whole epoch in the development of multimedia technologies is connected with them.
The monitors received its official name from the Russian abbreviation term "electron beam tube" from the Russian abbreviation. The English analogue of which is the Cathode Ray Tube phrase with a corresponding CRT reduction.
Before the PC appeared in the houses, this electrotechnical device was represented in our everyday kinescopic TVs. At one time they were even used as displays (count). But about this later, and now let's figure it out a little in principle of the action of CRT, which will allow us to talk about such monitors at the greater level.
Progress of kinescopic monitors
The history of the development of an electron-beam tube and its transformation into CRT monitors with a decent screen resolution are saturated with interesting discoveries and inventions. At first it was an instrument such as oscilloscope, radar screens RLS. Then the development of television presented us more convenient to view the device.
If we talk specifically about the displays of personal computers available to a wide range of users, then the title of the first monica is probably worth sending the vector display station IBM 2250. Created it in 1964 for commercial use with the computer System / 360 series.
IBM has many developments to equip PC monitors, including the design of the first video adapters that have become a prototype of modern powerful and standards transmitted to the display image.
So, in 1987 I saw the light adapter VGA (Video Graphics Array) working with a resolution of 640 × 480 and aspect ratio of 4: 3. These parameters remained basic for most of the manufactured monitors and televisions before the appearance of widescreen standards. In the process of evolution of the ELT monitors, many changes in the technology of their production took place. But I want to stay separately at such moments:
What determines the form of a pixel?
Knowing how the kinescope works, we will be able to figure out the features of the ELT of Monitors. The ray produced by an electron cannon deviates the induction magnet to get exactly in special holes in the mask located in front of the screen.
They form a pixel, and their form determines the configuration of color points and the qualitative parameters of the resulting image:
- Classic round holes whose centers are located on the vertices of the conditional equilateral triangle form a shadow mask. The matrix with uniformly distributed pixels provides maximum quality when playing lines. And perfect for office design applications.
- To increase the brightness and contrast of the screen, Sony used aperture mask. There, instead of points, a number of rectangular blocks glowed. This allowed the maximum to use the area of \u200b\u200bthe screen (Sony Trinitron monitors, Mitsubishi Diamondtron).
- Combining the advantages of these two technologies managed in a slit grille, where the holes had a type of rounded top and bottom of the elongated rectangles. And the blocks of pixels shifted relative to each other vertically. Such a mask was used in the displays of NEC Chromaclear, LG Flatron, Panasonic Pureflat;
But not only the shape of the pixel determined the advantages of the monitor. Over time and its size began to have a determining value. It changed ranging from 0.28 to 0.20 mm, and a mask with smaller, more dense holes allowed to create high-resolution images.
An important and, alas, the characteristic is noticeable for the consumer remained the frequency of the screen update expressed in the flickering of the image. The developers tried with all his might, and gradually instead of the sensitive 60 Hz dynamics of changing the displayed picture reached 75, 85 and even 100 Hz. The last indicator already allowed to work with maximum comfort and the eyes were almost not tired.
Working on improving quality continued. The developers did not forget about such an unpleasant phenomenon as low-frequency electromagnetic radiation. In such screens, this radiation is directed by the electron cannon directly to the user. To eliminate this disadvantage, all sorts of technologies were used and different protective screens and protective coatings were used.
The requirements for security monitors have been tightened and reflected in constantly updated standards: MPR I, MPR II, TCO "92, TCO" 95 and TCO "99.
Monitor who trust professionals
Work on the continuous improvement of multimedia video techniques and technologies with time led to the appearance of high-definition digital video. A little later, thin screens appeared with backlit from economical LED lamps. These displays have become an embodiment of a dream, because they are:
- lighter and compact;
- differed in low power consumption;
- much safer;
- did not have flicker even at lower frequencies (there is flickering of another kind);
- had several supported connections;
And it was not clear to those specialists that the era of CRT monitors was completed. And it seemed that the return to these devices would not be. But some professionals who know all the features of new and old screens have not hurried to get rid of high-quality ELT displays. After all, according to some technical characteristics, they clearly won their LCD competitors:
- excellent viewing angle, allowed to read information by siting on the side of the screen;
- ELT technology allowed without distortion to display a picture with any resolution, even when using scaling;
- the concept of non-working pixels is missing here;
- the time of inertia residual image is negliguously small:
- practically unlimited range of shades displayed and amazing photorealistic color reproduction;
It is the last two qualities that left the chance to once again show themselves. And they still have been in demand from the gamers and, especially, with specialists working in the field of graphic design and photo processing.
Here is such a long and interesting story at the old, kind friend, called the CRT monitor. And if you have at home or at the enterprise there is still such a thing, you can try again in the case and in a new way to appreciate its quality.
On this I say goodbye to you, my dear readers.