for some weird reason, spacehey did not like it when I kept the formatting on this. So now it looks ugly. This is so sad, as I spent a lot of time making it not ugly. This is basically the dumbed down version of the wikipedia page for CRT monitors. It's my own version. :P
Anyways, I got bored during class, so i made this.
How in the world does it work?:
Vacuum Tube takes an electric current(stream of charged particles), and controls them in a vacuum(space devoid of matter), which connects to electrodes(electrical conductor that makes contact with non-metal part of circuit) with a voltage (what’s needed to move a charge between two points) applied.
One or more electron guns produce Cathode Rays, also known as electron beams. These beams are observable electrons, and can be “projected” onto a glass tube that has charged electrodes attached.
The Cathode Rays of the CRT are collimated, or parallel.
These cathode rays are displayed on a phosphorescent screen. Phosphorescence is a type of photoluminescence. In other words, it emits light after absorbing photons. Although not exactly the same, the type of photoluminescence in cathode rays is related to the absorption of electromagnetic radiation, or fluorescence, as we call it.
The phosphorescent being exposed to radiation in short wavelengths causes the substance to glow. The substance absorbs the light radiation and reproduces it in a longer wavelength.
The difference between phosphorescence and fluorescence would be that the phosphorescent substance will not immediately reproduce the radiation absorbed. Phosphorescent substances absorb the radiation, and reproduce it much longer after the source of the radiation is removed from contact.
That phosphorescent screen is what displays the images of the CRT.
In 1890, Arthur Schuster and William Crookes demonstrated how Cathode Rays could be deflected by electric and magnetic fields.
1st CRT (Cathode Ray Tube) demonstrated in 1897
J.J. Thompson showed us all about the negatively charged things in them. Things smaller than atoms. Electrons.
In the same year, Ferdinand Braun displayed the “Braun Tube”. It was an interesting little fellow, and was the first usage of the CRT to display things.
In 1922, John Bertrand Johnson and Harry Weiner Weinhart developed a hot-cathode tube, which was the first of its kind. It was commercialized the same year.
In 1926 Kenjiro Takayanagi made history by displaying a 40 line resolution with a mechanical camera, and in 1927 the madman did it again, with a 100 line display.
German company Telefunken made the first manufactured CRT sets in 1934.
In 1947, the CRT amusement device was created. It was basically the first video game.
In 1954, RCA made color CRTs, and those were basically the first color television sets ever.
Although it never went into production, the Aiken Tube of 1960 was a flat panel display. It used only one electron gun. It was never released because of some dumb patent problems, but I think it’s because flat screens are dumb.
In 1987, Zenith made some flat screens. But they were expensive! They tried to make them with cheaper methods, but that didn’t really sort itself out until the early 2000’s.
The late 90’s to early 2010’s saw the sun set on our beloved tubes. The newer, more conventional LCD screen quickly overtook the market.
Thus closed the curtain on CRT displays. In 2015, the last recycled CRTs stopped production, and the technology was considered obsolete.
This would be the case, if it weren’t for two specific groups. Airlines, who use them for cost related reasons, or GAMERS, who use them for a variety of benefits that come only with the tube.
As of January 2023, there is still a community of people who love CRT monitors. Subreddits, forums, and videos on the displays are still active to this day. Niche internet communities are often the saving grace of a lot of otherwise dead technology. CRT monitors are a great example of that.
Internally coated with aluminum, which evaporates inside the vacuum and condenses inside the CRT.
This means that ion traps, which basically prevent everything going boom, aren’t needed.
Previously, magnets were needed for ion traps, but in the 1950’s, aluminum ended that all.
Magnets may be used to adjust the display’s geometry. I would go on about that, but I HATE geometry, so that’s a no for me.
Emit red, green, and blue light.
Aperture grille designs pack this light together in stripes. This is one of two main manufacturing methods for CRTs.
Shadow Mask is the other main method.
Uses a metal plate with many small holes. This is so the beam only projects on the right phosphors on the tube.
Creating the screen is a lot of work.
You need to create the dot matrix, so the light doesn’t get everywhere.
You can coat the screen in dichromate sensitive polyvinyl alcohol photoresist, which you dry, and then coat in colloidal graphite, which creates carbon film. Then you use hydrogen peroxide to remove excess photoresist. Phosphor filled the holes in.
Another way would be to suspend phosphors in aromatic diazonium salt, which adhered to the screen. This created a dot matrix in which you needed polymer, or sometimes black chromium, not to mention other methods…
Wow, that’s a lot. A lot that I will NOT remember, because I’m not good at science. I’m just a little computer boy.
Anyway, have you ever wanted to align phosphors with photolithography? CRTs are your ticket, baby!
Another point is that you can BAKE them. In a Lehr Bake. Don’t try this at home, please.
Color convergence is really just an issue involving the alignment of colors.
If the shadow mask or Aperture Grille gets magnetized, the magnetic field goes out of whack, and displays the wrong color phosphors.
The earth’s magnetic field messes with this, so measures such as a magnetic shield made of soft iron/steel, including a degaussing (demagnetizing) coil.
Most CRTs have this built in, though.
Dot pitch refers to the maximum resolution of the CRT display. If it gets to that maximum, displaced lines may appear. These lines are called moiré fringes. These are displayed because what is trying to be displayed is beyond the shadow mask’s capabilities.
Aperture grille screens do not have this problem vertically, as they are not arranged that way.
This problem is reduced by arranging the shadow masks’ holes in a honeycomb pattern.
Video Projectors and Rear Projection Televisions (RPTVs) are types of projection CRTs.
Beam Index Tube
Also known as Uniray, Apple CRT, and Indextron.
These types were originally brought up in the 1950’s by Philco, and they were just all around better. They required less energy, it was immune to Earth’s magnetic field, and it was simple. Sadly, the idea was rejected due to how difficult it was to make.
The idea was revived by Sony in the 1980’s as Indextron, but the development of LCD technology was more important, so that got trashed.
These screens may not be entirely flat.
LG Flatron, Sinclair TV80, TV Watchmans, and Video Doorbells.
Was a circle screen. Scanned from the center to the edges of the screen.
Electrostatic deflection is used, which is a way of modifying the path of particles.
Microchannel plates make the display brighter on these screens.
Graticules are basically guidelines placed in the monitor, like a grid.
Image Storage Tubes
Mainly a part of analog phosphor storage oscilloscopes, which are different from digital storage oscilloscopes, which use SSDs.
The brief display on this is where the phosphor does good. As mentioned earlier, phosphor contains radiation for a much longer time than fluorescence, and that allows images projected on an Oscilloscope to be captured and displayed later on.
A hurdle in this is that the phosphor can only display this for a few seconds. This can be overcome with the use of a direct view storage tube, which will display until you don’t want it to.
A storage tube is basically the same as the conventional tube, except it has a metal grid coated in dielectric layer, which is an insulator that can be polarized when an electric field is applied. So when you apply an epic amount of voltage, the mesh screen is constantly at a state of potential.
Used in computer design systems.
Used in 70’s and 80’s arcade games like Asteroids.
They draw by each point, instead of a scan.
Data Storage Tubes
The Williams Kilburn Tube stored binary data. It was mainly used in the 40’s as a random access digital storage device.
This one was not a display device. It couldn’t be viewed due to a big metal plate in the way.
Also known as a “Magic Eye Tube”.
This assisted in the tuning of the receiver, which altered the shadow. This was also used on tape recorders in recording level meters.
Used mainly in early computers. Displays a lot of text, or anything that requires a high photographic output.
A stencil is used for specific character selection.
They had very long necks, because there were multiple deflection systems needed to correctly display the image.
Trademarked line of small CRTs. They were created by Industrial Electronic Engineers.
They were simple, and didn’t require a lot of the crazy things most CRTs did. But they required an insane amount of power, so there weren’t that many of them in use.
These were used for video walls, such as Mitsubishi’s Jumbotrons.
These were first used at the 1980 MLB All-Star Game.
These ones are different, because the electron beam is not displayed in a focused beam. Instead, the electrons are basically sprayed all over the entire phosphor screen.
In other words, each unit is a single light bulb, with each one coated with red, blue, or green phosphor, in order to make up what they couldn’t before.
These displays have been widely replaced by Light-Emitting Diode, or LED displays.
These were used in grind operated stroboscope lamps, or strobe lights, since 1958.
They have also been used in electron-stimulated luminescence (ESL) lamps since 2011.
They have unphosphored glass. Now, if you’ve learned anything, you may be like…WHAT? HOW? Well, that’s because they had little baby wires embedded into it. So no, you could not just take a random piece of glass and make a CRT, unfortunately.
These were basically printers,or electrostatic print heads since the 1960’s.
The unphosphored glass was used so that the electron beam could pass through it, through the wires, and onto a sheet of paper.
The desired areas would be charged with electrons, and then the paper would be near ink with the opposite electron charge, and the two would attract until the ink and the paper basically kissed, thus forming the desired image.
These were another 1990’s-2000’s invention. The idea was experimented by Philips Research Laboratories, but never made it into the market.
Superslim, Ultraslim, Vixslim, and Cybertube were all just brand made slim CRTs.
Advantages over Modern Tech
Clear display. The interlaced lines make the refresh rate way faster than other monitors.
They can also display resolutions that aren’t an option for other displays.
Arcade light guns ONLY work on CRTs, because of the required timing properties that only they have.
Yes, you can use an arcade light gun on a CRT monitor.
There’s a whole retrogaming community! It’s all people who love old school tech.
The retrogaming community is focused on preserving and celebrating the history within these screens.
Disadvantages compared to Modern Tech
Less portable. CRT monitors are HUGE.
Price. Now that there’s a community around them, people who still own them have jacked up the price, making it pretty difficult to sort through.
They are also not too easy to come by. This depends mainly on where you live.
The Dangers of CRT Monitors
CRTs emit amounts of X-Ray radiation.
The electron beam is all over the shadow mask or aperture grille as well as the phosphors. This makes bremsstrahlung, or braking radiation.
Although it sounds scary, the amount of radiation you get from CRTs is pretty cool. It won’t hurt you at all. The FDA says it’s fine, and they always tell the truth (shows them blatantly lying) so it’s fine.
Have you ever been told to stay at least 6ft away from your television at all times? Well this is due to the 1968 Radiation Control for Health and Safety Act!
Older CRTs were manufactured with things like cadmium. Cadmium is a toxin in this context. There’s also leaded glass, which is a total pain in the butt for the environment.
The usage of a vacuum probably leads to some concerns. I would say there’s no reason to worry in this case, but there is. The vacuum restricts the electrons from freely moving.
If you damage the glass, the vacuum will suddenly collapse under the rush of atmospheric pressure. This will cause all the parts to rapidly pull inward, and then proceed to spray all over the place at insane speeds.
In other words, don’t break the glass, or you will experience the third impact.
High-Frequency Audible Noise
The scanning frequencies of CRT monitors are at the upper part of what humans can hear, which means certain people, mainly kids, will hear it. It’s really annoying.
You can get a little shock if you touch the CRT too soon, whether it be on, or off.
It’s not that bad of a shock, and it’s pretty fun to get all that electricity in my fingers and poke people.
The electron guns make it relatively easy to capture the image of the CRT remotely, and reconstruct it on another display. This is known as Van Eck Phreaking.
This happens with electronics in general, which is why the NATO certified TEMPEST shielding can be used to mitigate this effect.
If you try to dismantle it, you may die.
Restrictions require you to take CRT monitors to specific e-waste facilities.
Ok that's all. bye.