Found this interesting CRT tube cut-away:

http://pic70.picturetrail.com/VOL1851/8120392/15212176/232968101.jpg


Illustration showing the interior of a cathode-ray tube for color televisions and monitors. Numbers in the picture indicates:

1. Electron guns
2. Electron beams
3. Focusing coils
4. Deflection coils
5. Anode connection
6. Mask for separating beams for red, green, and blue part of displayed image
7. Phosphor layer with red, green, and blue zones
8. Close up of the phosphor-coated inner side of the screen

This image was rendered using the Persistence of Vision Raytracer (see http://www.povray.org/) - merged with the close-up insert and numbers added using a graphics software package.
Created by Søren Peo Pedersen (Check out the incredible images they have on this site in their "Hall of Fame")

With the exception of being the full red/green/blue spectrum in one tube, how close is this image to an actual rendering of a PJ's CRT?

Mark S.

On our CRT's it the same except that we don't have a #6 mask and our #7 is a single phosphor color (R, G or B) depending on the tube, and each tube we use is a a single gun #1.

Terry

and 2: since it is a single gun only (per tube), you have one beam only.

The phospor (8) is an even white coating (no matter if the tube is for red, green or blue).

And another thing:
the beams do not have color in real life.

What size relation is there between a well defined electron beam and the phosphor "pixels" ? Is it such that it's impossible to turn on a single "pixel" and that the actual coating would never be a limiting factor in the resolution a pj can resolve ?

I never thought much on it but I'm thinking now that the phosphor coating is rich like film grain, but the electron beam could never get that small.

Hmm.. all making sense now. I was considering moving my pj to the back of the room to mitigate the damn noise it makes, thereby using a smaller raster size. But since the electron beam is static (in size) the ablility to resolve a given resolution would be greatly diminished.

So when the manufacturer determines the max output resolution of a CRT projector is it a function of only beam size and bandwidth capabilities ?

And another thing: the beams do not have color in real life.
No color, huh? That's interesting-- that was a misnomer I've had all these years. Wouldn't it be nice if there was a 3 hour accredited class in "CRT Projectors 101" and one could really get all the info from the beginning?

But then again, only the crowd that lurks on this website would show up. :o

"Originally Posted by kschmit2
And another thing: the beams do not have color in real life."

But, what if the electron beam did have a color?
If the beam were to pass through some gas it would color the beam,
and maybe we could do away with the phospher?

For a projection CRT you would also need a convergence coil between items 3 & 4 ;)
I think it's a misnomer to call it a beam, it's really a stream of individual electrons which are drawn to the Anode plate.

For a projection CRT you would also need a convergence coil between items 3 & 4 ;)
I think it's a misnomer to call it a beam, it's really a stream of individual electrons which are drawn to the Anode plate.
Some serious magic..... One of the 8th wonders of the world , IMO.

I found a pic of this serous German CRT tube! So what kind of hellacious CRT PJ would result from throwing 3 of these things into a box car- :)

http://pic70.picturetrail.com/VOL1851/8120392/15212176/233135741.jpg

Some serious magic..... One of the 8th wonders of the world , IMO.

I found a pic of this serous German CRT tube! So what kind of hellacious CRT PJ would result from throwing 3 of these things into a box car- :)

http://pic70.picturetrail.com/VOL1851/8120392/15212176/233135741.jpg

I don't know but they either need to mow the driveway or turn on the sprinkler. :D

Art