Electronics > Projects, Designs, and Technical Stuff
Electron Beam Field
ZeroResistance:
--- Quote from: Nominal Animal on July 30, 2019, 10:33:52 pm ---In a way, wider electron beams work more like a jet of water than a ray of light; their control really is an art.
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Astounding analogy that one!
--- Quote from: coppercone2 ---
try to get a tour of a linear accelerator some time to see how crazy focusing can get
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Thanks for the tip.
dzseki:
--- Quote from: ZeroResistance on July 30, 2019, 09:49:30 am ---
--- Quote from: SilverSolder on July 29, 2019, 10:20:11 pm ---The best CRT computer monitors were capable of resolutions up to 2560x1600, far better than any TV tube, requiring high precision manufacturing of the tube as well as extensive amounts of control and correction of the deflection currents (as well as dynamic focus control) - these monitors were probably the peak of the CRT art. If you think in terms of this number of pixels of resolution, on a 20" monitor, you are probably close to what is realistically possible in terms of dot size and placement.
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Now that you talk about it. I'm just beginning to realise the enormity of the work that the guys at labs like Sony did to get the CRT at the level that it stands today.
I wonder how much time did someone like Sony take to perfect the CRT. I mean the Trinitron was a breakthrough technology at its time. How long would have Sony engineers worked on it. 2 years ? probably more?
Having said that what kind of resolution would that 2560 x 1600 monitor have for its deflection system.
I guess for a TV the information of beam intensity is encoded in the analog signal itself along with the horz and vert sync pulses. So in that way as long as the beam is aligned to the correct spots on screen. the analog signal does its magic. I don't think any digital processing takes place per pixel in a TV. I'm not sure about a PC monitor though.
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Another art were the professional CRT projectors, these could fit 2000 pixels on a ~13cm wide picture tube, while the beam current was approaching 1mA (!) (@ 34kV), without cooling the tube the beam could melt the glass of the tubeface in normal operation!
SilverSolder:
Yes, one of the pleasures of looking under the hood of old equipment is admiring the extreme skill that was used to get the absolute best out of whatever technology was available at the time! At some point, art and science begin to overlap. Of course this principle still applies today...
ZeroResistance:
--- Quote from: dzseki on July 31, 2019, 09:53:20 am ---
Another art were the professional CRT projectors, these could fit 2000 pixels on a ~13cm wide picture tube, while the beam current was approaching 1mA (!) (@ 34kV), without cooling the tube the beam could melt the glass of the tubeface in normal operation!
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What is the significance of the ! sign after the 1mA.
1mA * 34000 = 34W
What caused the glass to melt at these power levels. I would understand that the heat capacity of glass would be very low.
Wouldn't the beam current in a color TV be of similar levels, around 1mA.
dzseki:
--- Quote from: ZeroResistance on July 31, 2019, 11:58:56 am ---
--- Quote from: dzseki on July 31, 2019, 09:53:20 am ---
Another art were the professional CRT projectors, these could fit 2000 pixels on a ~13cm wide picture tube, while the beam current was approaching 1mA (!) (@ 34kV), without cooling the tube the beam could melt the glass of the tubeface in normal operation!
--- End quote ---
What is the significance of the ! sign after the 1mA.
1mA * 34000 = 34W
What caused the glass to melt at these power levels. I would understand that the heat capacity of glass would be very low.
Wouldn't the beam current in a color TV be of similar levels, around 1mA.
--- End quote ---
The significance is two fold:
a.) as the beam current gets higher it is more difficult to keep it in a tight spot. 2000 pixels on 13cm wide tube would suggest 65um "big" beam spot, whereas the typical pixel pitch on a conventional CRT monitor was 0.24mm and the beam current was 100uA at best.
b.) 34W only, yes, concentrated to a 65um spot, that translates to an insane power density...
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