Monitors on cathode ray tubes (well, including TVs)
- probably the only devices in everyday life that contain a radio tube
(the kinescope is just that), and are increasingly being squeezed out
similar devices with an LCD matrix. Let's take a look and see
what is inside the monitor.

The first problem that arises is how to disassemble. Like all screws
unscrewed - but does not open. It turned out it was all a malicious latch in
cover, which must be pressed with a thin screwdriver, and it is enough
strongly, and I was afraid to break it, I pressed it lightly, that's why I scratched
surface:

Having removed the top plastic cover, we can see
electromagnetic screen, made in the form of a casing of a very thick
perforated aluminum foil. Its purpose is not to release
electromagnetic radiation generated by the monitor during operation.
The casing is electrically connected to the chassis, which in turn is grounded.

Let's remove the screen and see the stuffing. Put on the kinescope from left to right:
Anode connection wire (red with an elastic band in the form of a suction cup),
Deflecting system, focusing magnets and controller board, put on
on the end of the kinescope, feeding the cathode.

ATTENTION! DO NOT POWER ON THE MONITOR WITH THE COVER REMOVED!!! An accelerating voltage of +25,000 volts is applied to the anode, the touch is deadly.

How does the monitor work? Briefly, the following will happen. Cathode
looks like a spiral light bulb. When
voltage is applied to the cathode, it heats up, and due to the phenomenon
thermionic emission, electrons begin to fly out from it. Since in
kinescope vacuum then nothing prevents the electrons from moving in
space. The emitted electron begins to move uniformly in
direction of the screen, as it is attracted by the positive charge
anode (let me remind you, the electron has a negative charge) Flying through the focusing
magnets focus a stream of electrons into a thin beam. Next, the beam hits
into the scope of the deflecting system. The deflection system is magnetic and
consists of several coils of a special shape. Feeding on coils
voltage can form a magnetic field that will deflect
electron beam to any point on the screen. Making the magnetic field change
we will make the ray run sequentially through the screen line by line, so
we'll get an image. Electrons hitting the screen bombard
phosphor, a substance that glows when irradiated with electrons. Due
inertia of vision, we see the picture formed on the screen, although
it represents sequentially lit dots. It's a principle
short and simplified work. More detailed material can be found in
the Internet.

Now for some frequently asked questions.

What hums and rustles when the monitor is turned on, and also rustles after the monitor is turned off?

Buzzes when the degaussing loop is turned on. The point is that
directly behind the screen there is an iron mask that allows
build color images. If this mask is magnetized, then the colors on
the monitor will float, so it is demagnetized every time it is turned on
alternating magnetic field. For this, a demagnetization loop is used -
black harness on the widest part of the kinescope. On it when turned on
for a couple of seconds, an alternating current with a frequency of 50 hertz is supplied, which removes
mask magnetization. Now about the rustling. The point is that in the process
dust accumulates inside the monitor. When there is a lot of dust
covers the kinescope. When the monitor is turned on, the anode is supplied with
positive voltage that forms on its surface
static charge. Static charge attracts dust particles, and when all
dust on the kinescope begins to be massively attracted to it and this gives
such a rumble. When the monitor is turned off, the electronics start charging from
kinescope to shoot, and the dust particles come off the monitor under the influence of force
elasticity, and again, when they start doing it en masse, you can hear
rustling.

The monitor emits a lot of harmful fields and it is harmful to sit at it for a long time

As we could make sure by disassembling the monitor - it has
aluminum screen that does not emit electromagnetic radiation
out. The front surface of the monitor is also covered with a thin film of
metal (note that TVs do not have such a coating, therefore
a static charge accumulates on its surface, which cracks if
hold your hand, monitors do not have this). Electrons bombarding
The phosphor emits soft x-rays, but is completely absorbed by the glass
screen. If the monitor is grounded, then it is safe to say that there are no
it does not radiate harmful fields in large quantities. Concerning
harmful to the eyes, the harmfulness lies in:
1) Flickering pictures. A comfortable picture is provided by the refresh rate.
less than 85 Hz, but the OS often defaults to a minimum of 60 Hz,
so check and set your monitor correctly. Otherwise
there will be increased eye fatigue.
2) Constant static load on the eyes. During the hours of the eyes
focused at a distance of half a meter, which again leads to fatigue.
But the design of the monitor has nothing to do with it, the same load and
reading a book.

Is it true that CRT monitors are more harmful than LCD?

No it is not true. A properly configured CRT monitor is similar in terms of damage to an LCD monitor.

I have seen / heard that there are special protective screens that you need
place in front of the screen to protect against harmful effects
monitor.

Yes, indeed, there were such screens, and they were a piece
glass, sprayed with transparent metallization, but they were needed in the 90s
years when the design of monitors was imperfect. As it was said
above on modern monitors, such metallization has already been done on
kinescope, so the need for additional protection missing.

And they also say that cacti next to the monitor absorb harmful radiation and protect the user. it
utter nonsense. Electromagnetic radiation cannot be sucked from
surrounding space, it can be absorbed, but it can be absorbed
only what falls on the body. The myth about cacti is a sustainable household
a myth that regularly pops up in articles "on a note" in the tabloid
press.

And they also sell such special stickers from harmful radiation ...

Stickers of this kind, including for mobile phones- common scam.

LCD monitors appeared in almost every computer store, and reasonable price. Prices have decreased by about half compared to what it was a year ago. And they continue their rapid decline. At the end of 2000, the price for an LCD monitor was about $1100, but now you can buy an average display for $550. Entry-level models are sold even cheaper, sometimes under $300. Some models have already crossed the bottom $250 bar, although they will have to be looked for. Reducing the price is great, but what's even more encouraging is that LCD displays have advanced technologically over the past year. And although LCD monitors still cannot catch up with their CRT counterparts in terms of picture quality, this gap is constantly shrinking.

The first and most important improvement is that the viewing angle has increased in LCD monitors. It was the viewing angle that was the weakest point of LCD monitors. In the best models, the vertical viewing angle has reached values ​​from 90 to 160 degrees. But there are quite a few pitfalls here, so different models differ greatly in viewing angle. More importantly, the number of colors has also improved. In 2000, you could find models that could only display 16-bit color. Now almost any LCD monitor supports 24-bit color. Although from a practical point of view, this 24-bit color is still very far from CRT monitors.

Among the improvements, it will not be superfluous to note the response time of transistors, which has grown significantly over the year. As announced by some manufacturers, the reaction time of the new monitors is twice as fast as the previous generation. As a result, another huge disadvantage of LCD monitors, afterglow, has almost disappeared. So now on the LCD monitor you can quite comfortably work with graphic applications and even play. By the way, we almost forgot to mention the brightness and contrast - they are also constantly improving and approaching the results of CRT monitors.

Despite roughly equal prices and impeccable technology, the LCD monitor has its drawbacks compared to the CRT. Some users will never buy an LCD monitor for many reasons. Let's try to highlight the pros and cons of LCD and CRT monitors.

Liquid crystals or cathode ray tube?

The first advantage of an LCD monitor is that you forget about geometry problems. These monitors are free of distortion, keystone defects, and brightness issues. The picture is geometrically flawless. Designers, fans of precise graphics, are crazy about such monitors. Unfortunately, the LCD monitor has very serious flaws that will make any artist stick to the good old kinescope.

Drawback 1

The contrast ratio of the best CRT monitors is 700:1. The best LCD monitors can boast only 450:1. In addition, models with a contrast ratio of 250:1 or even 200:1 are not uncommon. A low contrast ratio causes dark colors to be displayed as completely black. In this case, the color gradations of the picture are easily lost.

Drawback 2

Almost all manufacturers report support for 16 million colors. However, the matrix in most of them is capable of displaying 260,000 colors, and the Neovo F-15 succeeded in this. The result is a 16-bit color display, although the monitor is advertised as supporting 24 bits. However, to be fair, LCDs have evolved significantly in recent years, although they still haven't come close to the CRT color spectrum. Instead of displaying all the colors fading into one another, the image has a grainy, mottled texture. You will get the same effect if you reduce the number of colors in Windows.

Drawback 3

If you buy a new CRT display, you won't even try to use a refresh rate below 85Hz. But if for a CRT display the refresh rate is a good criterion quality, the same cannot be transferred directly to the LCD. In a cathode ray tube, an electron beam scans an image on a screen. The faster the scan, the better the display, and the higher the refresh rate. Ideally, your CRT display should run between 85 and 100 Hz. In an LCD display, the image is created not by an electron beam, but by pixels consisting of red, green, and blue sub-pixels (a triad). Image quality depends on how quickly the pixels turn on and off. Pixel turn-off speed is often referred to as response time. For the monitors we tested, it ranged from 25ms to 50ms. In other words, the maximum number of images displayed per second is between 20 and 40, depending on the model.

LCD vs CRT: A Quick Comparison

We have tried to summarize in a table the main differences between LCD and CRT monitors.

	LCD (TFT)	CRT (CRT)
Brightness	(+) from 170 to 300 cd/m2	(~) 80 to 120 cd/m2
Contrast	(-) 150:1 to 450:1	(+) 350:1 to 700:1
Viewing angle	(~) 90° to 170°	(+) over 150°
Convergence defects	(+) no	(~) 0.0079 to 0.0118" (0.20 to 0.30 mm)
Focusing	(+) very good	(~) fair to very good
Geometry	(+) flawless	(~) possible errors
"Dead" pixels	(-) up to 8	(+) no
Input signal	(+) analog or digital	(~) analog only
Possible permissions	(-) hard-fixed resolution or interpolation	(+) set
Gamma (the representation of colors to the human eye)	(~) satisfactory	(+) photographic quality
uniformity	(~) often lighter around the edges	(~) often lighter in the center
Color purity, color quality	(-) poor to average	(+) very good
flicker	(+) no	(~) invisibly at refresh rates over 85Hz
Exposure to magnetic fields	(+) not affected	(-) dependent on shielding, can be heavily affected
Pixel response time	(-) 20 to 50 ms	(+) not noticeable
Energy consumption	(+) 25 to 40 W	(-) 60 to 160 W
Dimensions/weight	(+) minimal	(-) large dimensions, high weight

(+) - advantage, (~) - mediocre, (-) - disadvantage

Basic Principles of LCD Monitor Operation

Three different liquid crystal technologies are implemented in LCD monitors - TN + film, IPS and MVA. But regardless of the technology used, all LCD monitors rely on the same fundamental principles of operation.

One or more neon lights provide a backlight to illuminate the display. The number of lamps is small in cheap models, while up to four are used in expensive ones. In fact, using two (or more) neon lights does not improve image quality. It's just that the second lamp serves to ensure the fault tolerance of the monitor in the event of a breakdown of the first. Thus, the life of the monitor is extended, since a neon lamp can only last 50,000 hours, while electronics can withstand from 100,000 to 150,000 hours.

To ensure a uniform glow of the monitor, the light passes through a system of reflectors before hitting the panel. The LCD panel is, in fact, an extremely complex device, although it is not noticeable at first glance. A panel is a complex device with many layers. Note two layers of polarizers, electrodes, crystals, color filters, film transistors, etc. In a 15" monitor, there are 1024 x 768 x 3 = 2,359,296 subpixels. Each sub-pixel is driven by a transistor that produces its own voltage. This voltage can vary greatly and causes the liquid crystals in each subpixel to rotate through a specific angle. The rotation angle determines the amount of light that passes through the subpixel. In turn, the transmitted light forms an image on the panel. The crystal actually rotates the polarization axis of the light wave, as the wave passes through the polarizer before reaching the display. If the polarization axis of the wave and the polarizer axis coincide, the light passes through the polarizer. If they are perpendicular, no light can pass through. More detailed information about the essence of the polarization effect can be found in the 11th grade physics textbook.

Liquid crystals - average state

Liquid crystals are a substance that has the properties of both a liquid and a solid. One of the most important properties of liquid crystals (it is used in LCD displays) is the ability to change its orientation in space depending on the applied voltage.

Let's delve a little into the history of liquid crystals, as it is quite interesting. As is usually the case in science, liquid crystals were discovered by accident. In 1888 Friedrich Reinitzer, an Austrian botanist, studied the role of cholesterol in plants. One of the experiments involved heating the material. The scientist found that the crystals become cloudy and flow at 145.5°, and then the crystals turn into a liquid at 178.5°. Friedrich shared his discovery with Otto Lehmann, a German physicist who discovered the properties of a liquid in a crystal in relation to light. Since then, the name "liquid crystals" has gone.

The illustration shows a molecule that has the properties of a crystal - methoxybenzidine butylanaline (methoxybenzilidene butylanaline).

Enlarged image of liquid crystal

TN+Film (twisted crystal + film)

Figure 1: In TN+film panels, the liquid crystals line up perpendicular to the substrate. The word "film" in the name comes from an additional layer that serves to increase the viewing angle.

TN+film is the most simple technology, since it is based on the same twisted crystals. Twisted crystals are years old and have been used in most of the TFT panels sold in the past few years. To improve the readability of the image, a film layer has been added to increase the viewing angle from 90° to 150°. Unfortunately, film does not affect contrast levels or reaction times, which remain poor.

So, at least in theory, TN+film displays are the cheapest, budget solutions. The process of their production is not much different from the manufacture of previous panels on twisted crystals. Today there are no cheaper solutions than TN+film.

Let's briefly dwell on the principle of operation: if the transistor applies zero voltage to the subpixels, then the liquid crystals (and, accordingly, the axis of polarized light passing through them) rotate 90 ° (from the back wall to the front). Since the axis of the polarizing filter on the second panel differs from the first one by 90°, the light will pass through it. If the red, green and blue sub-pixels are fully utilized, together they will create a white dot on the screen.

If, however, a voltage is applied, in our case a field between two electrodes, then it will destroy the spiral structure of the crystal. The molecules will line up in the direction of the electric field. In our example, they will become perpendicular to the substrate. In this position, light cannot pass through the sub-pixels. white dot turns black.

The twisted-chip display has a number of disadvantages.

First, engineers have been struggling for a very long time to get liquid crystals to line up strictly perpendicular to the substrate when the voltage is turned on. This is the reason why older LCDs could not display sharp blacks.

Second, if a transistor burns out, it can no longer apply voltage to its three subpixels. This is important because zero voltage means a bright dot on the screen. For this reason, dead LCD pixels are very bright and visible.

As for 15 "" monitors, only one technology has been developed for them to replace TN + film - MVA (about it a little later). This technology is more expensive than TN+film, but it outperforms TN+film in almost every way. However, we mention "almost" because in some cases TN+film performs better than MVA.

IPS (In-Pane Switching or Super-TFT)

Figure 2: If a voltage is applied, the molecules line up parallel to the substrate.

IPS technology was developed by Hitachi and NEC. It was one of the first LCD technologies to overcome the shortcomings of TN+film. But, despite the expansion of the viewing angle to 170 °, the rest of the functions did not budge. The response time of these displays varies from 50 to 60 ms, and the display of colors is mediocre.

If no voltage is applied to the IPS, then the liquid crystals do not rotate. The polarization axis of the second filter is always perpendicular to the axis of the first one, so no light passes through in this situation. The screen shows almost flawless black color. So in this area IPS has a clear advantage over TN + film displays - if the transistor burns out, then the “dead” pixel will not be bright, but black. When a voltage is applied to the subpixels, the two electrodes create an electric field and cause the crystals to rotate perpendicular to their previous position. After which the light can pass through.

The worst thing is that creating an electric field in a system with such an arrangement of electrodes consumes a lot of energy, but even worse, it takes some time for the crystals to line up. For this reason, IPS monitors often, if not always, have faster response times than their TN+film counterparts.

On the other hand, the precise alignment of the crystals improves the viewing angle.

MVA (Multi-Domain Vertical Alignment)

Some manufacturers prefer to use MVA, a technology developed by Fujitsu. As they say, MVA provides the best compromise in almost everything. Both vertical and horizontal viewing angles are 160°; response time is half that of IPS and TN + film - 25 ms; colors are displayed much more accurately. But why, if MVA has so many advantages, is it not widely used? The point is that theory is not so good in practice.

The MVA technology itself evolved from the VA introduced by Fujitsu in 1996. In such a system, the unenergized crystals are aligned vertically with respect to the second filter. Thus, light cannot pass through them. As soon as a voltage is applied to them, the crystals rotate 90°, allowing light to pass through and creating a bright spot on the screen.

The advantages of such a system are speed and the absence of both a helical structure and a double magnetic field. Thanks to this, the reaction time was reduced to 25 ms. Here you can also highlight the advantage that we already mentioned in IPS - very good black color. The main problem of the VA system was the distortion of shades when viewing the screen at an angle. If you display a pixel of any shade, for example, light red, then half the voltage will be applied to the transistor. In this case, the crystals will only turn halfway. On the front of the screen, you will see a light red color. However, if you look at the screen from the side, then in one case you will look along the direction of the crystals, and in the other - across. That is, on one side you will see a pure red color, and on the other, a pure black color.

So the company came to the need to solve the problem of color distortion and a year later, the MVA technology appeared.

This time, each subpixel was divided into several zones. Filter-polarizers also acquired a more complex structure, with tuberculate electrodes. The crystals of each zone line up in their own direction, perpendicular to the electrodes. The task of this technology was to create the necessary number of zones so that the user always sees only one zone, no matter from which point on the screen he looks.

Before buying a monitor

There are several factors to consider when purchasing.

The maximum viewing angle should be as large as possible, ideally greater than or equal to 120° vertically (the horizontal angle is not that important).

Although the reaction time is often not specified, the shorter it is, the better. The response time of the best modern LCD monitors is 25 ms. But be careful, because manufacturers are often tricky here. Some indicate the turn-on time and turn-off time of the pixel. If the on time is 15 ms and the off time is 25 ms, then the reaction time is 40 ms.

Contrast and brightness should be as high as possible - at least higher than 300:1 and 200 cd/m2.

Another significant problem with LCDs is dead pixels. Moreover, it is impossible to fix these light (TN + film) or dark "dead" pixels. Located in bad places, "dead" pixels can seriously get on your nerves. So before buying an LCD monitor, make sure that there are no “dead pixels.” Especially since a few “dead” pixels are by no means considered a marriage.

Don't be fooled by the ability to rotate the display vertically. Yes, indeed, you can rotate the display by 90°, but for a 15"" monitor, such a function is doubtful, if not useless. You can use rotation in the following situations:

• creation office documents. Indeed, the rotate function can be of great help here;
• editing images that are larger in height than in width. However, CRT monitors are much better suited for image editing because they display truer colors with better contrast levels;
• web browsing. A rotated 15" monitor has a horizontal resolution of 768 pixels. However, most web pages are calculated for a resolution of at least 800 horizontal pixels.

Let's talk about monitors - LCD and CRT, about which is better. Previously, when there were still black and white convex monitors, working at a computer was always unsafe for the eyes. But now the time has changed and the progress of monitors is visible to the naked eye.

Comparison of LCD and CRT

Today, monitors have already changed a lot, they have become completely different - LCD monitors have replaced CRTs, they are not large compared to CRTs and no longer take up a lot of space on the table. They also use less electricity. But which is better today, CRT or LCD? Regular Users they will answer in chorus that LCD, but is it really so?

The monitor, as there is a lot in this word, often we look at it more time than at relatives or children, therefore, unfortunately, the choice of a monitor must be approached very seriously and responsibly.

CRT or cathode ray tube

A CRT monitor is a glass tube filled with vacuum. The front part of the monitor is a phosphor. For the phosphor, complex compositions based on rare earth metals, such as yttrium, erbium, are used. In simple terms, a phosphor is a substance that forms light when charged particles are applied to it. In order for a CRT monitor to display an image, an electron gun is used, it passes a stream of electrons through a metal mask (grid) to the inner surface glass screen monitor, which is covered with multi-colored phosphor dots.

If we take for example a new CRT-type monitor, then of course it will show very well (if necessary, the image can be corrected). The CRT monitor has one strong point that only expensive LCDs have - it's color reproduction. Like it or not, but CRT is much better than LCD. Only IPS matrices in LCD monitors can match the color reproduction of a CRT.

Conventional CRT monitors use three electron guns, while the old black-and-white monitors used only one.

The human eye can only respond to the three primary colors, which are red, blue and green and their combinations, and they create a huge number of colors or shades. The front part of the monitor is a phosphor, or rather its layer, and it consists of dots - so small that they are almost impossible to see. They literally reproduce the primary colors of RGB.

RGB (Red, Green, Blue) is an additive color model that describes a color synthesis method for color reproduction.

In addition to the cathode ray tube, there is also electronics that processes the incoming signal from the computer's video card. Electronics is engaged in optimizing the displayed image - it amplifies the signal and stabilizes, which is why the picture on the monitor is stable, even if the signal is unstable.

The disadvantage of CRT monitors is that they are harmful to the eyes, and also take a lot of light. And at the same time, over time, they become cloudy, today it is almost impossible to find a CRT monitor that shows like an LCD, and if it is also more than 17 inches, then its “soapiness” will be immediately noticeable.

LCD or LCD monitors

Liquid crystals, on which LCD monitors are based, are characterized by a transition state of matter between solid and liquid, while maintaining the crystalline structure of the molecules and ensuring fluidity. The matrix of such a monitor is indeed liquid in a sense, for example, if you lightly press your finger on a working monitor, you will see how the liquid that is inside shifts. This is a liquid crystal solution. At first, liquid crystals were used in the displays of calculators, as well as digital watches, then they switched to PDAs and computer monitors.

Today, not almost, but completely, CRTs have been replaced by LCD monitors.

LCD is two panels, they are made of very thin and pure glass (substrate), between these panels there is a thin layer of liquid crystals (called pixels), they are involved in the construction of the image. Unlike CRT monitors, LCDs have such a thing as "native" resolution - this is the one on which the monitor is desirable to work. It is this extension that will allow the monitor to display the picture with the highest quality. If you set another extension, the image will either be stretched (sharpness deteriorates, there are slight distortions), or vice versa - the extension will be changed, but part of the screen will be filled with black in order to maintain quality.

The contrast of monitors is determined by the ratio of brightness between white (as the brightest) and black (the darkest) color. A good indicator is 120:1. Monitors with a contrast ratio of 300:1 can give an accurate image of halftones.

Comparison of LCD and CRT

LCD monitors are good because they are completely flat, the picture is sharper than a CRT monitor, and the color saturation can also be higher. There are no distortions, as well as the eternal problem of "soap" (cloudy image) - all this is absent from "thin" monitors, which is why they are ahead of the CRT.

Here in this picture is additional information about the difference between monitors, but the interesting thing is that the picture is a little muddy, blurry, that's exactly how many CRT monitors now show (since new ones are not being released anymore and they are old):

Therefore, we can conclude that the LCD monitor is better, and CRTs are not just a thing of the past, but if possible, then buy an expensive monitor, they are less harmful to the eyes when working at a computer for a long time.

Here's a note for you. Many 15-inch LCD monitors consume about 20-40 watts in operation (less than 5 watts in standby mode), you can compare this with a 17-inch CRT monitor, which consumes 90 to 120 watts in operation (in standby mode - 15 watts). Can you imagine? I’ll also calculate for you - if the monitor works for about eight hours a day and so the whole working week, then a 17-inch CRT will consume 300 kW per year, this is taking into account the standby mode of an hour or two, while 15 inches LCD - 60 kW (17 inches, I don’t think it will be much more). These are trifles for you, but if there are a hundred, two hundred, three hundred computers in the company, then there is a reason to think about a new type of monitor.

But CRT monitors also have strengths, as a rule, they are of interest to designers for the most part - color reproduction. If you work on an LCD for a while and then look at a CRT, you will notice the difference between color reproduction and image volume.

Monitors: LCD or CRT?

How many of those who come to the store or to any computer company to buy a monitor already know exactly what they need?
Yes, someone may have collected information on the Internet, magazines or other media for a long time, someone relies on the arguments of friends, and someone solely on their own experience. It is clear that all of us, having decided to buy, are guided by something. But will we be able to defend our preferences in a dispute with the manager of the company, with a friend, wife, or just with a random "expert" who met us in the store?
In any case, it never hurts to practice defending your arguments or to look at such a discussion from the outside and think about how you would behave in a similar case.
After all, the problem of choosing technologies for visual display of information used in computer monitors is still not so simple as to have an unambiguous solution ...

CRT monitors are yesterday, all manufacturers are gradually curtailing their production and switching to LCD. It is not for nothing that you will not see new models of CRT monitors at any computer exhibition, and what else you can find in stores is either a sale of randomly lying around in a warehouse, or samples of such quality that you will not look without tears.

Well, with the manufacturers, everything is just clear. The profitability of the production of budget (that is, the most massive) models of CRT monitors has already fallen to almost zero. And on professional models, even with a decent margin, you won’t earn much - there is too little demand and no prospects for expanding the market. It is the decrease in profitability (and not at all a drop in demand, as one might assume) that is the main reason for curtailing the production of CRT monitors. By the way, a similar situation developed two or three years ago in the CD-RW drive market, when HP, Yamaha and other large manufacturers left the market and took up the development of a more promising direction of DVD recording.

LCD monitors have ceased to be something outlandish, but a certain effect of technological novelty still remains. Plus, the reserves of LCD technology are not fully exhausted and manufacturers have room to improve. Thanks to this, at this stage, you can get quite a decent profit, even producing relatively small batches of entry-level LCD monitors - to say nothing of the giant leaders.

But pay attention to retail prices: if you take an LCD monitor with a screen of 15-17 inches, you can find a CRT model that is not inferior to it in key parameters and at the same time costs almost half as much.

Well, about "find" I strongly doubt it. You'll have to really strain to find something worthwhile. Yes, and with the key parameters you still need to figure it out. After all, one of the main advantages of LCD monitors is their small size and weight. They can be easily placed on any table, they can even be mounted on the wall. And in this sense, no model of CRT monitors can compare with them.

Yes, CRT monitors, in comparison with LCD models, are larger and heavier. But let's find out if these are such important advantages. For example, is the weight of the monitor really important for the average user?

By and large, the only time you will worry about weight is when transporting the monitor from the store to your home. Plus, force majeure circumstances like moving or rearranging furniture, which are extremely rare in the lives of most users.

Well, I do not! I remember my last CRT monitor (17-inch ViewSonic), under which my desk sagged. Yes, and moving and even moving the monitor from place to place is not so rare! So weight is important.

As for the sagging table - so it was necessary to pay attention to this when choosing furniture. After all, even if you are an adherent of LCD monitors, then in this case the computer desk should be designed for serious loads. And maybe tomorrow you need to bet on it laser printer or MFP - how then to be?

Now about the dimensions. If the system unit is located under the table, then the compact LCD monitor allows you to free up some space between the monitor and the keyboard. How to use this area more efficiently is an open question, since when working with a computer, reaching for something located behind the keyboard is hardly convenient.

And in the case when the monitor is installed on a system unit of a horizontal layout (desktop type), there is no gain at all - the case covers a deliberately large area, so there can be no talk of any savings in working space. Hanging a CRT monitor on the wall is also not a problem. To do this, you can use the TV bracket, which are now sold everywhere.

Well, I don’t know how convenient it is to use a TV bracket, in any case, I don’t really want such a “coffin” to hang over the desktop. As for saving the working space - after all, not only the keyboard lies on the table. And when using the LCD monitor at the table, you can also write, and there is a place to put a mug of coffee. No, of course, for a CRT monitor you can even buy a specialized computer desk with a special niche for the monitor, but such squalor will definitely not decorate the interior of an apartment.

So no one says that each user should hang the monitor on the wall. But if such a need arises, it will not be difficult to implement it. And this problem is not so urgent - how many users of LCD monitors hang them on the wall? For example, I don't know such people.

Speaking of convenience, one cannot help but recall how vulnerable the LCD screen is. It’s not so easy to even wipe off dust from it, not to mention fingerprints (and you try to clearly explain to your child that you can’t poke your finger at the screen). If you press hard, the consequences can be even more serious - you can accidentally push through the elastic surface and damage the screen area.

So after all, you can throw dumbbells into a CRT monitor. He'll get sick of it too.

Well, if you think like that, then the LCD monitor will not withstand such a crash test either. However, one cannot deny the fact that the screens of CRT monitors are protected much more reliably: their surface is a powerful glass shield that can be easily and quickly cleaned even from greasy fingerprints.

I must say that LCD monitors come with a glass coating. And as for the fact that you can’t explain to a child where you can poke and where not, you can put your fingers into the socket. If everything is so neglected, then it’s better not to buy a computer at all (by the way, it’s better to throw away the TV too). Well, there are even special brushes to remove dust from the LCD screen. By the way, CRT monitors are also not eternal - the phosphor burns out over time ...

The resource of a good CRT monitor (which will still cost less than an LCD model with the same screen size), even with intensive use, will last at least five years - during this time you will not even notice a picture deterioration with the naked eye.

And one more thing: the backlight lamp of the LCD screen also uses a phosphor, which, as mentioned above, tends to gradually burn out ...

So after all, the resource of an LCD monitor, and not even a very good one, will last at least five years. Well, besides, in five years it will already be so outdated that it will still have to be changed, if only simply to keep up with life.

If we talk about the advantages of an LCD monitor, then let me remind you that LCD monitors are safe for health, while CRT monitors give their users a whole bunch of harmful radiation. No wonder many users complain about the deterioration of their health and try to somehow protect their health with the help of special screens and glasses ...

Yes, the tales of “computer radiation” are immediately vividly recalled, which, after reading the inscription on the monitor “Low Radiation”, became stronger than in a nuclear reactor! Such misconceptions spawned a highly lucrative business in the production of all kinds of goggles and screens that could be "sold" for any money - a contingent of their consumers was never able to do their own analysis and marketing. It is enough to look at the price of these products to make everything fall into place: just as ten years ago the “best protective equipment” cost about $50 (budget ones cost about $5-10), and now they cost the same. Since then, technology has changed radically, the computer has fallen in price three times, and the monitor at least twice, but the price of goggles and screens remains unchanged, which suggests that it is determined only by specific demand, and not by real need. As a result, manufacturers of protective screens and special glasses continue to frighten users of CRT monitors with the same “evidence”, which in fact is a chaotic set of quasi-scientific facts that have not been verified by anyone in practice, which the “experts” of the respective companies cleverly use for their own purposes.

However, many users of CRT monitors report less fatigue when working with special goggles that absorb blue and harmful ultraviolet radiation. And skipping the predominantly yellow region of the spectrum, they increase efficiency and relieve the feeling of fatigue.

Well, yes, the so-called placebo effect, that is, the suggested effect, has not yet been canceled. Many users even note the beneficial effects of cacti, and rumors about a decrease in radiation due to planting them around monitors still cannot be eradicated.

As for the powerful UV radiation (with which the manufacturers of miracle glasses intimidate us), this is generally a myth: as is known even from the school physics course, the most ordinary window glass effectively absorbs UV spectrum radiation, not to mention the thick shield of special glass, made of which the CRT bulb is made. In addition, if CRTs really were a source of powerful UV radiation, then the monitor screen should have become very hot during operation.

But it cannot be denied that, in terms of the level of electromagnetic and other radiation, CRT monitors are less safe for users than LCD models.

Yes, but this does not mean that they are dangerous and that you should definitely protect yourself with anything. The kinescope of the monitor really emits radiation, like any electrical device, including a coffee maker. The human body is able to "magnetize" and this causes a change in metabolism. Variable electromagnetic fields cause fluctuations of ions in the human body, which also does not always benefit him. However, these same fields are used in medicine (for example, in physiotherapy).

But in medicine, everything is dosed and calculated. As you know, poison differs from medicine only in dosage. After all, an LCD monitor also emits, but its effect is incomparable with a kinescope.

But we “grab” no lesser dose of electromagnetic radiation from a TV, a vacuum cleaner, a trolley bus, and if there is electrical wiring near your bed, then its effect is even worse. At the same time, it is worth paying attention to the fact that any CRT monitor (even released ten years ago) is much safer than a household TV. Many of our fellow citizens spend 2-3 hours a day watching TV screens, and practically none of them associate their illnesses with the harmful effects of a cathode ray tube.

The surfaces of the screens used in modern CRT monitors, instead of simple glass, as before, have a special multi-layer coating of glass, phosphor and metals, which performs exactly the same functions as external protective screens - for this reason, the use of the latter loses all meaning today .

Moreover, as a result of the joint efforts of a number of large manufacturers of CRT monitors, many new technical solutions, which helped to secure the monitor as much as possible. For example, the cases began to be shielded: from the inside, a metal layer a few microns thick is sprayed onto the case, which, however, is equivalent to a whole metal sarcophagus. There was also a revolution in the design of cathode ray tubes. Displays made using new technologies give almost no electromagnetic radiation and are practically harmless to health.

However, according to the current GOST, the maximum duration of continuous work on a CRT monitor is 20 minutes. At the same time, adolescents aged 12-15 years can spend at the computer no more than one hour a day: first half an hour, then a break of 15 minutes and another half an hour. Even students should be in front of a CRT monitor for no more than two hours. And although many refer to these GOSTs as complete nonsense (which is absolutely true), all the same, when working with an LCD monitor, the eyes get tired less than in the case of a CRT monitor.

Here it is appropriate to recall that in the civilized world for more than ten years, security standards for computer monitors (TCS) have been in effect. As technology develops, the requirements of this standard become more stringent, and every four years a new edition of the TCO specification (TCO'95, TCO'99, TCO'2003) is released. At the same time, the standard is the same for all types of manufactured monitors. Thus, the design of TCO'99 certified LCD and CRT models provides the same high level of safety for the user's health.

And what do you object to the fact that during the operation of the cathode-ray tube of the monitor, the surface of the screen accumulates a positive charge and, as a result, dust begins to be attracted to it, and after a while around the operating monitor, the concentration of dust per unit volume increases compared to the rest of the room? So next to such a monitor, we also inhale more dusty air than in the rest of the room. In addition, dust, in turn, settles on the skin of the face, clogs pores, the skin does not breathe, which leads to the appearance of wrinkles and premature aging of the skin.

The mystical science of Kabbalistics prescribes, when invoking evil spirits, to outline with a pentagram exactly the area where they should appear. That is, you need to wash your face more often, clean the room, wipe the monitor and open the window for ventilation.

It's time to ask another question: why, in fact, the consideration of safety issues in most cases is reduced to the measurement of harmful radiation? Yes, because it is a very powerful trump card in the hands of supporters of LCD technology. But if we talk about security in a broad sense, then it should be noted that many other factors also affect user fatigue. So, for example, one of the serious drawbacks of LCD monitors is the pronounced pixelization of the image (well-marked jagged edges of letters, slanted lines, etc.), the negative effect of which is especially noticeable when working with text documents.

…This problem has been solved for a long time. To get rid of pixelation, just activate the ClearType option.

ClearType is a half measure, since this technology is applicable only when working with fonts. For graphical objects, it is useless. In addition, the use of ClearType on a PC with relatively low-powered processors leads to a significant decrease in the speed of displaying a screen image, which, in turn, can create significant discomfort for the user.

I agree. If you have a 486th processor, then ClearType will not help you much. By the way, it doesn't work in DOS 6.22 either. Only it is not very clear why in this case we should talk about a graphic image at all?

If we talk about comfort, then we need to mention the flickering of the frame scan of CRT monitors. With a frame rate of 75 Hz, it only seems to us that we do not notice this - in fact, our eyes get tired.

The LCD monitor has virtually no flicker at the frame rate, and this does not depend on whether the frequency is set: 65, 75 or 87 Hz. Due to the inertness of pixels, the brightness of a pixel simply does not have time to change before the next frame.

Yes, there is flicker in CRT monitors, but it should be noted that modern models of CRT monitors and video cards allow you to set such values ​​\u200b\u200bof the vertical scan (100 Hz or higher) at which flicker becomes almost imperceptible. By the way, most household TVs have a scanning frequency of only 50 Hz - and nothing, many people can absorb their favorite TV shows from the blue screen for hours. (TV models with a 100Hz scan have appeared on the market relatively recently and have not yet become widespread due to their high price.)

Moreover, many LCD monitors and laptop screens also flicker the backlight, and at a frequency that is clearly visible to the eye - 50 Hz.

As for the TV with its 50 Hz, this is, of course, correct. But keep in mind that few people watch TV from a distance of half a meter from the screen. And from a distance of 2-3 meters - it's a completely different story.

So after all, monitors (unlike household TVs) are developed precisely with the expectation that a person will sit at arm's length. There are other aspects as well.

CRT monitors are limited only by the maximum resolution, allowing you to equally well reproduce the picture with any resolution that does not exceed the maximum. In the LCD monitor, each pixel of the image corresponds to a pixel of the matrix, that is, such a monitor is able to provide quality image when working with a single (!) resolution, the value of which corresponds to the dimension of the LCD matrix (for example, 1024X768).

LCD monitors allow you to interpolate an image that has a resolution different from the matrix dimension.

But the image quality is significantly degraded. Try, for example, to work with small text or even just look at photos in interpolation mode. It is unlikely that such a result can be called satisfactory.

When watching movies or playing games, changing the working resolution of the matrix has practically no effect on image quality. Well, you can work with text at native resolution.

In addition, on some LCD monitors, you can reduce the image size (while maintaining the correspondence "one pixel of the image - one pixel of the screen") and provide high quality for a lower resolution signal.

But in this case, you will have to sacrifice effective screen area. For example, take a typical LCD monitor with a screen size of 15 inches diagonally and a matrix resolution of 1024x768 pixels. When displaying an image with a resolution of 800X600 pixels in 1:1 mode, the image size will be only 11.7 inches diagonally, that is, a little more than 60% of the screen area will be used.

If we talk about watching video on the LCD screen, then there is one serious problem. The inertia of the pixels of the LCD matrix leads to the fact that a smeared loop is observed behind moving objects, and the video is not played clearly enough.

Nothing like this! It is possible that something similar was observed in the first generation LCD matrices, but the new matrices do not have these shortcomings. Firstly, they have a much shorter pixel response time, and secondly, it must be taken into account that this effect of pixel inertia is noticeable only when switching white and black colors (transition from a fully on state of a pixel to a completely off state). When we watch a movie or play a game, the pixel color switches between halftones and it is simply impossible to notice any inertia.

Yes, but it should be noted that the decrease in inertia has its downside - namely, the deterioration of color reproduction. And in general, if we talk about color reproduction, then LCD technology is much less perfect compared to CRT.

The LCD screen pixel allows you to display approximately 260 thousand shades. Meanwhile, a video signal with 24-bit color depth can transmit more than 16 million colors, that is, 60 times more. Thus, accurate color reproduction in the case of an LCD monitor is generally out of the question. The maximum that can be obtained is a very rough approximation to the original picture.

260 thousand shades! Where can you find such an LCD monitor now? This is the last century. New LCD matrices reproduce 24-bit color and are capable of reproducing more than 16 million shades, and the human eye is no longer capable of distinguishing more.

However, the accuracy of human vision is quite enough to see that the LCD monitor screen mercilessly distorts colors. The fact is that the palette of the monitor is linear, and the sensitivity of human vision in different parts of the spectrum varies. For example, in the area of ​​​​neutral grays and skin tones, the eye is able to pick up even the slightest deviations. Pay attention to the fact that bright cars, landscapes, etc. are used as demonstration screensavers for monitors in computer salons - but you almost never see portraits there. If you put a CRT and LCD monitor side by side and display a well-shot portrait on the screen, then the comparison will clearly not be in favor of LCD technology. In addition, rich hues on any LCD screen take on a distinct metallic sheen, which also does not add to the naturalness of the image.

You should also not forget about a significant change in colors on the screen when the head deviates from the center line. The notorious “departure” of colors due to heating of the CRT monitor mask (and monitors equipped with CRTs with an aperture grille, such as Trinitron, by the way, are deprived of this drawback) turns out to be simply imperceptible in comparison with color distortions caused by even a slight change in the viewing angle of the LCD -monitor.

Again, this is outdated information. LCD viewing angles, once considered one of the weaknesses of LCD technology, have long ceased to be a problem. However, let's first define what is meant by such a characteristic as the viewing angle of an LCD monitor. Speaking in the language of physics, then the viewing angle is understood as the angle formed between the perpendicular to the surface of the monitor and the direction for which the measured contrast is 10%. Of course, such a strict definition says little to the inexperienced user. If we translate this into everyday language, then the viewing angle is the angle at which the image remains normally visible.

So, the new matrices provide fairly wide viewing angles (up to 170°) both horizontally and vertically.

When using the conventional method of measuring the viewing angle by changing the contrast, color distortion not taken into account at all, so for the end user such a characteristic is by and large useless.

In addition, the Achilles' heel of LCD monitors is the screen backlight. It is extremely rare for manufacturers to achieve uniform illumination of the entire screen area. To verify this, you can conduct a simple experiment: first display a white field and then a black field on the LCD monitor screen and evaluate the uniformity of the screen glow. In the vast majority of cases, the middle of the screen will be brighter than its edges (especially on a black box).

First of all, I cannot but admit that you are right about the complete uselessness of such a formal characteristic as the viewing angle. Indeed, the formalized method for measuring the viewing angle does not take into account color distortion. But modern matrices have not just large viewing angles in terms of changing the contrast - within these angles, color reproduction is also not disturbed. It's just that the LCD monitor does not have such a characteristic that would determine this parameter.

Well, about the uneven glow of the backlight - I absolutely disagree with you. Indeed, LCD monitors are inherently uneven in illumination, measured as the ratio of the maximum brightness of the monitor, which is usually achieved in the center, to the minimum brightness. Ideally, this ratio is equal to one, but in practice it is always greater. But the unevenness of modern LCD matrices is such that it is simply impossible to fix it with the naked eye. The fact is that the nature of the perception of the brightness of human vision is non-linear. If visually it seems to a person that the brightness of one object is twice the brightness of another, then from a physical point of view, their brightness should differ by almost ten times! This example clearly shows that the brightness unevenness on the screen can be quite high, but you just won’t notice it by eye.

Another significant disadvantage of LCD monitors is a smaller range of brightness compared to CRT. Take, for example, two monitors - LCD and CRT, display a white field on their screens and set them to the same brightness. Now let's display a black field on the screens - for a CRT monitor it will be really black, and for an LCD it will be dark gray (it's good if it's uniform).

This is due to two "inherent" disadvantages of LCD technology. First, an LCD panel pixel cannot be 100% transparent, if only because its effective area is less than its total area; in other words, there is always a black (opaque) border around each pixel. Because of this, you have to increase the brightness of the backlight. And secondly, even in a completely closed state, the pixel of the LCD matrix has a certain degree of transparency, and it is this circumstance that does not allow you to get a deep black color on the LCD monitor screen.

Once again, I note that the information provided is somewhat outdated. It rather refers to the first TS or IPS matrices. But in the new MVA matrices, everything is somewhat different: in such matrices, black is perfectly black! These matrices have very high contrast, comparable to that of CRT monitors. As for the higher maximum brightness of a CRT monitor - why, in fact, is it needed? Indeed, in the vast majority of cases, when working with LCD monitors, the maximum brightness value is never used.

Of course, LCD technology is developing, and this is good news. But the problem lies in the fact that manufacturers do not indicate on the box, or even in the monitor documentation, which matrix is ​​used in this device. In addition, it is no secret that in different instances of monitors of the same model, even released in the same batch, different models of LCD matrices can be used.

Yes, the matrix type is indeed rarely indicated in the technical documentation. But imagine that the documentation will say that this monitor uses an MVA matrix. For most users, this means absolutely nothing. Ultimately, this is what the concept of a brand is for, so that the user can fully rely on the manufacturing company without delving into technical details.

By the way, brightness is brightness, but let's remember that CRT monitors have geometric distortions that LCDs don't have in principle.

Yes, on this point CRT monitors undoubtedly lose LCD. However, it should be noted that in modern models of CRT monitors there are advanced functions that allow you to successfully compensate for any kind of geometric distortion. Another thing is that it takes time and patience to achieve the optimal result.

Yes, it takes a lot of patience and time. But how many users will mess with the settings? And the LCD monitor can be connected via a digital interface (DVI) - and no settings are needed at all.

It is, of course, so. However, one cannot help but pay attention to the following fact: despite the many obvious advantages of DVI, most LCD monitors currently produced are equipped with only an analog interface. DVI, as a rule, is provided only in rather expensive models.

Meanwhile, connecting an LCD monitor via an analog interface creates another problem - the need to adjust the phase of the video signal. And a phase mismatch (which can occur right during operation, for example, as a result of heating) leads to the appearance of flickering bands in the image, and this annoying defect can only be eliminated using the appropriate setting in the monitor menu.

Well, firstly, now more and more monitors are equipped with a DVI-input, and for monitors with a diagonal size of 17 inches and above, this has already become the de facto standard. Secondly, to adjust the phase (which is extremely rare), as a rule, it is enough to press only one auto-tuning button. And thirdly, the CRT monitor is characterized by the same problem - the instability of the analog signal.

Yes, but at the same time in the menu of the CRT monitor there is also large quantity settings to compensate for these shortcomings.

So after all, LCD models have a lot of settings. And we are not talking about the trivial adjustment of brightness and contrast and phase auto-tuning. With LCD monitors, it is possible to change the color temperature, adjust color channels, and much more. By the way, through these settings, LCD monitors lend themselves to quite professional calibration, allowing the user to create their own color profile. Moreover, such calibration can be done both manually and with the help of special professional calibrators. The latter circumstance indicates that LCD monitors are beginning to encroach on the market for professional monitors.

In addition, let me remind you once again that it is now difficult to buy a good budget-class CRT monitor.

Unfortunately, this is true. As mentioned at the very beginning of our conversation, manufacturers are actively curtailing the production of CRT monitors. And now produced 15- and 17-inch CRT models are typical consumer goods in the worst sense of the word. Therefore, if there is a desire to purchase a really high-quality device, then it makes sense to consider models with a screen diagonal of 19 inches and above.

But if you compare a 17-inch LCD model with a 19-inch CRT monitor, then there is practically no difference in price. And as soon as it comes to professional CRT monitors, the price of an LCD monitor will be much more attractive.

But there is a noticeable difference in image quality, and for many users this is a very important factor. In addition, cheap LCD monitors (which in the vast majority of cases are based on matrices of previous generations) have a number of significant drawbacks, which were discussed above. So the conclusion suggests itself: to get high quality and ensure comfortable work, you will have to shell out a hefty sum - regardless of whether you choose an LCD or a CRT model.

Next year, a significant reduction in prices for LCD monitors is expected. Still, LCD technology is still relatively young and is constantly being improved. More and more perfect types of matrices appear, and soon everyone will forget about the ghostly advantages of CRT monitors.

Given the pace of development of competing display technologies, it can be argued that the period of dominance of LCD monitors will not be long. On the way such promising technologies like OLED, LEP, LCoS. These solutions have a number of fundamental advantages over LCD technology and will really make a qualitative leap in the field of computer displays. Some of them are already used in mass-produced devices - however, so far we are talking about small displays (up to 2 inches diagonally). It is expected that commercial versions of full-size OLED displays (with a screen size of 15 inches diagonally) will appear on the market as early as next year. So maybe it makes sense to wait a little?

What technologies will replace LCDs is still an open question, although it is obvious that in the future this will inevitably happen and LCD monitors will be forgotten in the same way that CRT monitors are forgotten today. But this is in the future, and now it is clear that the era of CRT monitors (at least in the user segment of the market) has ended and CRT technology has been replaced by LCD technology.

Today, the most common type of monitors are CRT (Cathode Ray Tube) monitors. As the name implies, all such monitors are based on a cathode ray tube - a cathode ray tube (CRT). CRT stands for Cathode Ray Terminal, which no longer corresponds to a handset, but to a device based on it.

The technology used in this type of monitor was developed by the German scientist Ferdinand Braun in 1897. and was originally created as a special tool for measuring alternating current, that is, for an oscilloscope.

The design of the CRT - monitor.

The most important element of the monitor is a kinescope, also called a cathode ray tube (see Appendix A, Figure 1.). The kinescope consists of a sealed glass tube, inside of which there is a vacuum, that is, all the air is removed. One of the ends of the tube is narrow and long - this is the neck, and the other - wide and rather flat - is the screen. On the front side, the inner part of the tube glass is coated with a phosphor. Quite complex compositions based on rare earth metals - yttrium, erbium, etc. are used as phosphors for color CRTs. A phosphor is a substance that emits light when bombarded with charged particles. Note that sometimes the phosphor is called phosphorus, but this is not true, because. The phosphor used in the CRT coating has nothing to do with phosphorus. Moreover, phosphorus "glows" as a result of interaction with atmospheric oxygen when oxidized to P 2 O 5 and "glow" occurs for a small amount of time.

To create an image in a CRT monitor, an electron gun is used, from where a stream of electrons comes from under the action of a strong electrostatic field. Through a metal mask or grate, they fall on the inner surface of the glass screen of the monitor, which is covered with multi-colored phosphor dots. The electron flow (beam) can be deflected in the vertical and horizontal planes, which ensures that it consistently hits the entire screen field. The beam is deflected by means of a deflecting system (see Appendix A, Fig. 2.). Deflecting systems are subdivided into saddle-toroidal and saddle-shaped. The latter are preferable because they create a reduced level of radiation.

The deflecting system consists of several inductors located at the neck of the kinescope. With the help of an alternating magnetic field, two coils create a deflection of the electron beam in the horizontal plane, and the other two - in the vertical plane.

The change in the magnetic field occurs under the action of an alternating current flowing through the coils and changing according to a certain law (this is usually a sawtooth change in voltage over time), while the coils give the beam the desired direction. The path of the electron beam on the screen is shown schematically in Appendix B, fig. 3. The solid lines are the active path of the beam, the dotted line is the reverse.

The frequency of transition to a new line is called the horizontal (or horizontal) scanning frequency. The frequency of the transition from the bottom right corner to the top left corner is called the vertical (or vertical) scan frequency. The amplitude of the overvoltage pulses on the horizontal scanning coils increases with the frequency of the lines, so this node turns out to be one of the most stressed places in the structure and one of the main sources of interference in a wide frequency range. The power consumed by the horizontal scanning nodes is also one of the serious factors taken into account when designing monitors.

After the deflecting system, the electron flow on its way to the front of the tube passes through the intensity modulator and the accelerating system, which operate on the principle of a potential difference. As a result, the electrons acquire more energy, some of which is spent on the glow of the phosphor.

The electrons hit the phosphor layer, after which the energy of the electrons is converted into light, i.e. the flow of electrons causes the dots of the phosphor to glow. These glowing dots of phosphor form the image you see on your monitor. Usually in color CRT monitor three electron guns are used, as opposed to the single gun used in monochrome monitors, which are now practically not produced.

It is known that human eyes respond to the primary colors: red (Red), green (Green) and blue (Blue) and their combinations, which create an infinite number of colors. The phosphor layer covering the front of the cathode ray tube consists of very small elements (so small that the human eye cannot always distinguish them). These phosphor elements reproduce the primary colors, in fact there are three types of multi-colored particles whose colors correspond to the RGB primary colors (hence the name of the group of phosphor elements - triads). The phosphor 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 primary colors and sends a beam of electrons to different phosphor particles, whose glow of the primary colors with different intensities is combined and as a result an image with the required color is formed. For example, if you activate red, green and blue phosphor particles, then their combination will form a white color (see Appendix B, Fig. 4).

To control a cathode ray tube, control electronics is also needed, the quality of which largely determines the quality of the monitor. By the way, it is the difference in the quality of control electronics created by different manufacturers that is one of the criteria that determine the difference between monitors with the same cathode ray tube.

Each gun emits an electron beam (or stream or beam) that affects phosphor elements of different colors (green, red or blue). An electron beam intended for red phosphor elements must not affect a green or green phosphor. of blue color. To achieve such an action, a special mask is used, the structure of which depends on the type of kinescopes from different manufacturers, which ensures the discreteness (raster) of the image. CRTs can be divided into two classes - three-beam with a delta-shaped arrangement of electron guns and with a planar arrangement of electron guns. These tubes use slit and shadow masks, although it is more correct to say that they are all shadow masks. At the same time, tubes with a planar arrangement of electron guns are also called kinescopes with self-convergence of beams, since the effect of the Earth's magnetic field on three planar beams is almost the same, and when changing the position of the tube relative to the Earth's field, no additional adjustments are required.

The most common types of masks are shadow masks, and they come in two types: "shadow mask" (shadow mask) and "slit mask" (slot mask).

The shadow mask is the most common type of mask and has been used since the invention of the first color picture tubes. The surface of kinescopes with a shadow mask is usually spherical (convex). This is done so that the electron beam in the center of the screen and along the edges has the same thickness.

The shadow mask consists of a metal plate with round holes that occupy approximately 25% of the area (see Appendix B, Fig. 5). There is a mask in front of a glass tube with a phosphor layer. As a rule, most modern shadow masks are made from invar. Invar (InVar) - a magnetic alloy of iron (64%) with nickel (36%). This material has an extremely low coefficient of thermal expansion, so even though the electron beams heat up the mask, it does not adversely affect the color purity of the image. The holes in the metal grid work like a sight (albeit not an accurate one), it is this that ensures that the electron beam hits only the required phosphor elements and only in certain areas. The shadow mask creates a lattice of uniform dots (also called triads), where each such dot consists of three phosphor elements of primary colors - green, red and blue - that glow at different intensities when exposed to beams from electron guns. By changing the current of each of the three electron beams, it is possible to achieve an arbitrary color of an image element formed by a triad of dots.

One of the "weak" points of monitors with a shadow mask is its thermal deformation. Part of the rays from the electron beam gun hits the shadow mask, resulting in heating and subsequent deformation of the shadow mask. The ongoing displacement of the shadow mask holes leads to the appearance of a variegated screen effect (displacement RGB colors). The material of the shadow mask 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: firstly, this is a small ratio of electrons transmitted and retained by the mask (only about 20-30% passes through the mask), which requires the use of phosphors with high light output, and this, in turn, worsens the monochrome glow, reducing the color rendering range , and secondly, it is rather difficult to ensure the exact coincidence of three rays that do not lie in the same plane when they are deflected at large angles.

The shadow mask is used in most modern monitors - Hitachi, Panasonic, Samsung, Daewoo, LG, Nokia, ViewSonic.

The minimum distance between phosphor elements of the same color in adjacent rows is called dot pitch and is an index of image quality (see Appendix B, Fig. 6). Dot pitch is usually measured in millimeters. The smaller the dot pitch value, the higher the quality of the image displayed on the monitor. The horizontal distance between two adjacent points is equal to the step of the points multiplied by 0.866.

The slit mask is a technology widely adopted by NEC under the name "CromaClear". This solution in practice is a combination of a shadow mask and an aperture grille. In this case, the phosphor elements are located in vertical elliptical cells, and the mask is made of vertical lines. In fact, the vertical stripes are divided into elliptical cells, which contain groups of three phosphor elements in three primary colors. The slit mask is used, in addition to monitors from NEC (where the cells are elliptical), in Panasonic monitors with a PureFlat tube (formerly called PanaFlat). Note that it is not possible to directly compare the pitch size for tubes different types: The pitch of the dots (or triads) of the shadow mask tube is measured diagonally, while the pitch of the aperture grille, otherwise known as the horizontal dot pitch, is measured horizontally. Therefore, for the same dot pitch, a tube with a shadow mask has a higher dot density than a tube with an aperture grating. For example, a stripe pitch of 0.25 mm is approximately equivalent to a dot pitch of 0.27 mm.

Also in 1997 Hitachi, the largest designer and manufacturer of CRTs, has developed EDP, the latest shadow mask technology. In a typical shadow mask, the triads are placed more or less equilaterally, creating triangular groups that are evenly distributed across the inner surface of the tube. Hitachi reduced the horizontal distance between the triad elements, thereby creating triads that are closer in shape to an isosceles triangle. To avoid gaps between the triads, the dots themselves have been lengthened, and are more ovals than circles.

There is another type of tube that uses an "aperture grille". These tubes became known as the Trinitron and were first introduced to the market by Sony in 1982. Aperture grating tubes use an original technology, where there are three beam guns, three cathodes and three modulators, but there is one common focus (see Appendix B, Fig. 7).

An aperture grille is a type of mask used by different manufacturers in their technologies to produce kinescopes that have different names but are essentially the same, such as Sony's Trinitron technology, Mitsubishi's DiamondTron, and ViewSonic's SonicTron. This solution does not include a metal grid with holes, as in the case of the shadow mask, but a grid of vertical lines. Instead of dots with phosphor elements of the three primary colors, the aperture grille contains a series of filaments consisting of phosphor elements arranged in vertical stripes of the three primary colors. This system provides high image contrast and good color saturation, which together provide high quality monitors with tubes based on this technology. The mask used in Sony (Mitsubishi, ViewSonic) tubes is a thin foil on which thin vertical lines. It rests on a horizontal wire (one in 15", two in 17", three or more in 21") wire, the shadow of which is visible on the screen. This wire is used to dampen vibrations and is called a damper wire. It is clearly visible, especially with a light background images on the monitor.Some users fundamentally do not like these lines, while others, on the contrary, are satisfied and use them as a horizontal ruler.

The minimum distance between phosphor strips of the same color is called the strip pitch and is measured in millimeters. The smaller the stripe pitch value, the higher the image quality on the monitor. With an aperture grille, only the horizontal size of the dot makes sense. Since the vertical is determined by the focusing of the electron beam and the deflecting system. The aperture grille is used in monitors from ViewSonic, Radius, Nokia, LG, CTX, Mitsubishi, all monitors from SONY.

It should be noted that one cannot directly compare the pitch size for tubes of different types: the pitch of dots (or triads) of a tube with a shadow mask is measured diagonally, while the pitch of the aperture grille, otherwise called the horizontal dot pitch, is measured horizontally. Therefore, for the same dot pitch, a tube with a shadow mask has a higher dot density than a tube with an aperture grating. For example: 0.25 mm strip pitch is approximately equivalent to 0.27 mm dot pitch.

Both types of tubes have their advantages and their supporters. Shadow-mask tubes produce a more accurate and detailed image because light passes through the sharp-edged holes in the mask. Therefore, monitors with such CRTs are good for intensive and long-term work with texts and small graphics elements, for example, in CAD/CAM applications. Tubes with an aperture grille have a more openwork mask, it obscures the screen less, and allows you to get a brighter, more contrasting image in saturated colors. Monitors with these tubes are well suited for desktop publishing and other color oriented applications. In CAD systems, monitors with a tube that uses an aperture grille are disliked, not because they reproduce fine details worse than shadow mask tubes, but because the screen of a Trinitron type monitor is flat vertically and convex horizontally, i.e. . has a dedicated direction.

As already mentioned, in addition to the cathode ray tube, there is also control electronics inside the monitor that processes the signal coming directly from the video card of your PC. This electronics must optimize the signal amplification and control the operation of the electron guns, which initiate the glow of the phosphor that creates the image on the screen. The image displayed on the monitor screen looks stable, although, in fact, it is not. The image on the screen is reproduced as a result of a process in which the glow of the phosphor elements is initiated by an electron beam passing sequentially through the lines in the following order: from left to right and from top to bottom on the monitor screen. This process happens very quickly, so it seems to us that the screen is constantly lit. The image is stored in the retina of our eyes for about 1/20 of a second. This means that if the electron beam moves slowly across the screen, we can see this movement as a separate moving bright dot, but when the beam starts moving, quickly drawing a line on the screen at least 20 times per second, our eyes will not see a moving dot, but see only a uniform line on the screen. If we now force the ray to sequentially run over many horizontal lines from top to bottom in less than 1/25 of a second, we will see an evenly lit screen with little flicker. The movement of the beam itself will be so fast that our eye will not be able to see it. The faster the electron beam passes over the entire screen, the less flickering of the picture will be noticeable. It is believed that such flicker becomes almost imperceptible at a frame repetition rate (beam passes through all image elements) of about 75 per second. However, this value is somewhat dependent on the size of the monitor. The fact is that the peripheral areas of the retina contain light-sensitive elements with less inertia. Therefore, the flickering of monitors with large viewing angles becomes noticeable at high frame rates. The ability of the control electronics to form small image elements on the screen depends on the bandwidth (bandwidth). The bandwidth of a monitor is proportional to the number of pixels used by the computer's video card to form an image.

Some parameters that determine the quality of the CRT monitor:

Tube diagonal and apparent diagonal

One of the main parameters of a CRT monitor is the diagonal size. tubes. Distinguish directly between the size of the diagonal of the tube and the visible size, which is usually about 1 inch smaller than the diagonal of the tube, partially covered by the monitor case.

Light transmission coefficient

The light transmission coefficient is defined as the ratio of the useful light energy emitted to the outside to the energy emitted by the inner phosphorescent layer. Typically, this ratio is in the range of 50-60%. The higher the light transmission coefficient, the lower the video signal level required to provide the required brightness. However, this reduces the contrast of the image due to the decrease in the difference between the radiating and non-radiating areas of the screen surface. With a low light transmission coefficient, the focus of the image is improved, however, a more powerful video signal is required and, accordingly, the monitor circuit becomes more complicated. The specific value of the light transmission coefficient can be found in the manufacturer's documentation. Typically, 15-inch monitors have a light transmission coefficient in the range of 56-58%, and 17-inch monitors - 52-53%.

Horizontal scan

The horizontal sweep period is the time it takes the beam to travel from the left to the right edge of the screen. Accordingly, the reciprocal of this is called the horizontal frequency and is measured in kilohertz. As the frame rate increases, the horizontal refresh rate must also be increased.

Vertical scan

Vertical scan is the number of image updates on the screen per second, this parameter is also called the frame rate.

The higher the vertical scan value, the correspondingly less noticeable to the eye is the effect of a frame change, which manifests itself in the flickering of the screen. It is believed that at a frequency of 75 Hz, flicker is almost imperceptible to the eye, but the VESA standard recommends operation at a frequency of 85 Hz.

Resolution

Resolution is characterized by the number of pixels and the number of lines. For example, a monitor resolution of 1024 x 768 indicates the number of dots per line is 1024 and the number of lines is 768.

Uniformity

Uniformity is determined by the constancy of brightness over the entire surface monitor screen. A distinction is made between "brightness uniformity" and "white uniformity". Usually monitors have different brightness in different parts of the screen. The ratios of brightness in areas with maximum and minimum value brightness is called the uniformity of the distribution of brightness. White uniformity is defined as the difference in brightness of white color (when displaying a white image).

Non-convergence of rays

The term "non-convergence of the rays" means the deviation of red and blue from the centering green. Such a deviation prevents obtaining pure colors and a clear image. Distinguish between static and dynamic non-reduction. The first refers to the non-convergence of three colors over the entire surface of the screen, which is usually associated with errors in the assembly of the cathode ray tube. Dynamic non-convergence is characterized by errors at the edges with a clear image in the center.

Image purity and clarity

Optimum image clarity and clarity can be achieved when each of the RGB rays hits the surface at exactly the right point, which is ensured by a strict relationship between the electron gun, shadow mask holes and phosphor dots. Beam displacement, forward or backward displacement of the gun center, and beam deflection caused by external magnetic fields can all affect image clarity and clarity.

Moire- this is a type of defect that is perceived by the eye as undulating image stains associated with incorrect interaction between the shadow mask and the scanning beam. Focus and moiré are related settings for CRT monitors, so some moiré is acceptable with good focus.

jitter

Jitter is usually understood as oscillatory changes in the image. with a frequency above 30 Hz. They can be caused by vibration of the monitor mask holes, which, in particular, may be due to improper grounding. At frequencies less than 30 Hz, the term "swimming" is used, and below 1 Hz - "drift". Slight jitter is inherent in all monitors. In accordance with the ISO standard, a diagonal point deviation of no more than 0.1 mm is allowed.

Mask deformation

All shadow mask monitors are subject to some degree of distortion due to thermal distortion of the mask. Thermal expansion of the material from which the mask is made leads to its deformation and, accordingly, to displacement of the mask holes.

The preferred mask material is Invar, an alloy having a low coefficient of linear expansion.

Screen coating

While the monitor is in use, its screen surface is exposed to intense electron bombardment, which can build up a charge of static electricity. This leads to the fact that the screen surface “attracts” a large amount of dust, and in addition, when a user touches a charged screen with a hand, a weak electric discharge can unpleasantly “click”. To reduce the potential of the screen surface, special conductive antistatic coatings are applied to it, which in the documentation are denoted by the abbreviation AS - anti-static.

The next purpose of coating is to eliminate reflections of surrounding objects in the glass of the screen, which interfere with operation. These are the so-called anti-reflective coatings (anti-reflection, AR). To reduce the reflection effect, the screen surface should be matte. One way to obtain such a surface is to etch glass to obtain not a specular, but a diffuse reflection (Diffuse is a reflection in which the incident light is reflected not at an angle of incidence, but in all directions). However, in this case, the light from the phosphor elements is also diffusely scattered, the image becomes blurry and loses its brightness. Recently, to obtain anti-reflection coatings, a thin layer of silicon dioxide is used, on which profiled horizontal grooves are etched to prevent the reflection of external objects from entering the user's field of view (at its normal position near the monitor). In this case, such a profile of the grooves is selected so that the attenuation and dispersion of the useful signal is maximum.

Another unfavorable factor that is dealt with by processing the screen is glare from external light sources. To reduce these effects, a dielectric layer with a low refractive index, which has a low reflectivity, is applied to the surface of the monitor. Such coatings are called anti-glare or anti-halation (anti-glare, AG). Usually, combined multilayer coatings are used that combine protection against several interfering factors. Panasonic has developed a coating that uses all the described types of coatings, and it has the name AGRAS (anti-glare, anti-reflection, anti-static). To increase the intensity of useful light transmitted between the screen glass and the low-reflection layer, a transition layer is applied, which has a refractive index that is average between the glass and the outer layer (enlightenment effect), which also has conductive properties to remove static charge.

Sometimes other combinations of coatings are used - ARAG (anti-reflection, anti-glare) or ARAS (anti-reflection, anti-static). In any case, the coatings somewhat reduce the brightness and contrast of the image and affect the color reproduction, however, the convenience of working with the monitor, obtained from the use of coatings, pays for these shortcomings. You can check the presence of an anti-reflective coating visually by examining the reflection from an external light source when the monitor is off and comparing it with the reflection from ordinary glass.

The presence of anti-glare and anti-static coatings has become the norm for modern monitors, and some differences in the quality of coatings that determine their effectiveness and the degree of image distortion associated with technological features have little effect on the choice of model.