Ok bad title, but i had something on my mind and just wondering what others thoughts are.
As we all know, our CRT 'projectors' make a picture from 3 gun colors.
Why are there no CRT tubes that have all the colors in them (like in a normal TV) that can emit a picture like ours do and not be just direct view?

:confused:

I bet it has something to do with the shadow mask in a direct view. Look closely at a direct view set, you will see something that looks like pixels. that is the shadow mask needed to properly get the colors to display on the screen, not sure if that is right but it has something to do with separating the three colors on the face of the tube. now imagine magnifying that to a screen, you would see it worse than a digital I would imagine. the tubes on our crt's have no shadow mask, so the size of the phosphor being excited is only limited to how small we can get the electron beam diameter.

I am not completely sure about this someone else can explain it better I am sure.

Athanasios

I look into my lenses all the time, thus explaining the dots that dance in front of my eyes.

:)

From InfoComm Academy:

"Projection CRTs are different from those used in the direct view displays. CRT projectors
use three monochromatic cathode ray tubes – one with red phosphors, one with green,
and one with blue. As an electron beam moves inside each tube, it excites the colored
phosphors lining that tube. No shadow mask is needed because each tube only has one
phosphor on the face of the CRT. A lens in front of each tube focuses the emitted light onto
a screen. These three images containing the red, green, and blue image information are
overlapped one on top of the other, creating a full-color image.
The phosphors used in a projection CRT are different from those used in a CRT monitor.
CRT projectors’ phosphors are designed to put out more light than those in a monitor."

http://www.thompsonet.com/pdf/Teachers_Resource.pdf

Also 3 tubes are brighter than 1. ;)

Sony had a one tube projector, i don't remember the model.

Sony had a one tube projector, i don't remember the model.

I see them on Ebay all the time. Someone around here posted pics of one in action. it didn't look to good, imagine that though. :) I know they had built in betamax player built in to them.

Lots of advantages with going to 3 CRTs:

greater phosphor area = more light. With 1 CRT, not only do the 3 phosphor colors share 1 common space, they need to be separated by a border which takes tube space
a single CRT having the same phosphor area of 3 separate CRTs would have to be more than 3 times larger for the above reason + reduction of light due to shadow mask.
A matching lens of that CRT size would be prohibitively expensive.

Lots of advantages with going to 3 CRTs:

greater phosphor area = more light. With 1 CRT, not only do the 3 phosphor colors share 1 common space, they need to be separated by a border which takes tube space
a single CRT having the same phosphor area of 3 separate CRTs would have to be more than 3 times larger for the above reason + reduction of light due to shadow mask.
A matching lens of that CRT size would be prohibitively expensive.


Somebody should crank the bejesus out of some 27" TV and make a fresnel lens, just to see if it can be done. Would be atrocious quality, though... :D

I look into my lenses all the time, thus explaining the dots that dance in front of my eyes.

:)

Those dots in front of your eyes is what you get for taking a lapdance in trade for projector repairs in strip joints:D

"crank the bejesus out of some 27" TV "

Not a tv but a computer monitor running HD and a flat screen.

Vidimagic, including a model that came complete with an Avon carrying bag.

Hope those Avon weren't dainty little ladies;-).

You don't see those ads anymore for the big screen experience, people being dissapointed to receive just a sheet of 40" or 50" plastic, they have been replaced by ads/spam for plans or plans/old overhead projector fresnelplate, to turn an lcd panel into a projector.

"crank the bejesus out of some 27" TV "

Not a tv but a computer monitor running HD and a flat screen.

Back in the day (~1996, when a teenager with a 486/40 could never hope to own ANY kind of projector) I rolled my own with the fresnel / box technique on my 14" VGA monitor. Aside from being pretty dim (obviously it emitted less light than the actual screen) it worked remarkably well. The only problem was that turning the monitor upside down caused some of the internals to shift, which screwed up the color toward one edge! :D

Those were the days... It's good to remember every once in a while with all the cool stuff I've got now, how amazing it would have been to have then. Now I get to have it!