DIY Video Projector

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#241
one more thing...

I read that metal halide bulbs produce very little IR, much less than halogen. so does that mean that you don't need cold mirrors? what exactly are cold mirrors? I'm guessing that they have an IR filter so you don't fry the lcd.
 
#242
Cold mirror is a misnomer. It absorbs the heat; passing on the light. Cold mirrors get very hot.

Whether metal-halides produce more or less IR than halogans, I don't know.

I have read of other person who have tried to make projector out of a slide proj., but the direct light produced too much heat. The LCD pixels do not react to well to excessive heat and they distort somehow.

This is why I went through all the trouble w/ the LEDs. To avoid this problem, UV filtering, and noise.
 
#243
yeah, well I kinda figured the mirrors would get hot because I remember somebody talking about heatsinks on the back of mirrors. but that would make sense in my scheme 🙂 because if the mirror has an IR filter, that would mean it would absorb the IR, therefore getting hot, and pass the rest of the visible light.

also, why are you concerned with a UV filter. I would want to do it for the longevity of my eyes, but is there any other reason?

Thanks,

Evan
 
#244
As for UV light, it could be that simple: For your protection. Could it be to provide for the whitest light possible? I don't know. I do know it was on the Sharp diagram. Maybe the filter takes the place of a cold mirror.
UV is what cooks you in the summer. Right?

I'm not too sure, sorry.

At some point, I'm going to have to gather all this information on to my web site. It's too hard to follow along if you haven't from the beginning.

I need to do this logically, so things are easy to find.
I may be able to start a forum on this specific subject on my site.

I'll start to think about it over Thanksgiving.

later,

Vince

[Edited by vdi_nenna on 11-21-2001 at 03:43 PM]
 
#246
some specs

Hello all, this is the first time that I have posted on this thread so forgive me if I'm a bit behind. Although I have been reading along for a few days. I visited the Runco site tonight(http://www.runco.com/Products/LCD/Default.htm)and I found that they use a 250w metal halide, which produces 2000 ansi lumens. There lcd screen is at 1366 x 768 native res( what the hell is "native"?)at 180 mhz(RGB). The unit seems pretty small, 16.3 x 25.8 x 8.4in at 56lbs, which would be ideal. Not sure how much the bulb costs, but I'm sure it's not cheep(1500hrs).Not sure if any of this will help anyone, but I know everyone is having problems w/lighting.I may be able to get some more info on acctual "blueprints". I have some family that work in the "industry", I'll see what I can do.
THUNTER
 
#247
Native resolution would be what number of pixels the LCD actually has. Pixels: height x width. They can also be compressed for higher resolution. I don't remember how it's done, but it's in digital. Usually through component video. The specs on the Runco are excellent.

Any extra help or knowledge on this subject would be appriecated.

Vince
 
#249
Your best bet for datasheets is the Texas Instrument's website or a Google search for the individual parts. If it is an evaluation kit, you may have to contact their engineering support group for specific questions (I wrote a email about DLP availablity in small quantities and they pretty much asked for a tech brief of my project). I wish that I had seen that item on eBay, I might have "sniped" ya'.
 
#253
Lateral thinking by a Newbie.

Guys and of course Guyettes.

1/ Don't dismiss my post until the you reach the end.

2/ I am a newbie at electonics. but read (1)

3/ I have been following this post for the last couple of
weeks , and the good thing is that I have registered
to DIYAUDIO.COM to submit my idea.



Has anyone considered how a telescope works. ( ie moon
telescopes )

Is there an opportunity to use such a device in this
projector

ie
Big light source at one end of the projector( the moon - the big end of the telescoope) , bouncing light off 2 mirrors to a small lens ( the eyepiece part of the telescope )

This should get rid of the heat problem, especially if the walls for the telescope was reflective. And provide a big light source to the screen matrix.


If I am being stupid in my thinking, then my apologies, but to me if the light source is big and bright enough, it might work.


My $0.02 worth

regards
Gaspode
 
#255
New to the forum.

I'm interested in getting or building a video projector. I have a very low budget so unless I were to get something real cheap it looks like the DIY route is the way to go. I'm nearly complete with my MAME arcade cab so I'm familiar with doing these kinds of things.

Last night I sat down and started searching across the search engines. I came across this page and actually read every post from beginning to end. I'm thrilled at the interest in doing this.

A couple people mentioned it but I don't think anyone really gave any concrete results for it: What about putting a lcd screen on an overhead projector? This seems so simple compared to the other routes people are taking. Am I missing something? This seems so simple to do. To reduce ambient light you could block off the area around the lcd panel so that light only comes through the lcd. You could also build a sort of box that would enclose it. Comments? Keep up the good work.
 
#260
Are you saying the results are bad because of the yellowish tint? If so, I'm sure this can be remedied by using a brighter, whiter bulb inside. Something could be rigged up fairly easily it would seem. If the actual OHP bulb couldn't be replaced by a whiter, brighter one then one could probably still jimmy rig up a light inside using something like a very bright white headlight. The lenses and everything else would still be the same, just change the light source inside. What do you think?

It seems these overhead projection LCD's are very cheap... I mean it looks as though some are going for $50 or less. It looks like there's some good OHP's for about $50 too. Add the cost of replacing the bulb and rigging up something real bright and you easily have a sub $150 project. I'm starting to get pretty excited about the idea of watching dvd's and playing games on a huge *** screen. Darkening the room wouldn't be a problem at all here.
 
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