DIY Video Projector

[Myren]

oh, yeah, misread your post on the monitors bitch.

dwalls is totally right, just add a pci video card. i'm running four video cards in my system, one AGP geforce one and three PCI matrox millenium II's.

the matrox milleniums arent fast enough to stream video fullscreen, i'd suggest a PCI LeadTek geforce MX something or other. go for the leadteks, supposedly they have better image quality (better filtering circuitry) than everything else. but the matrox's can be grabbed cheap if your never planning on running a movie on your other monitors agian and their 2d image quality is ****ing awsome. if you've got a really high res monitor though, they wont have enough bandwidth to output to it.

ayup.

[Myren]

if you want to show the same thing on both screens, i think you need to get a single video card that can output to two monitors. they're readily avaiable, matrox makes a really good one for $150, and i think theres a PCI version available. its also capable of displaying different things things to different monitors too.

[The Xung]

@Myren. What shape is your reflector? I've been playing with some math and it seems that with most of our lense setups, an elliptical shaped reflector would concentrate the light best although I haven't tried the shape yet. My main concern is that an elliptical shape would focus more light through just the center of the LCD than a parabola, causing a more hot spotted image.

What material is your custom built reflector made out of? Is much better than the aluminum foil i've been using?

[Bitch]

Hmm.. I'm not too thrilled about buying extra display-card. And I don't need to have them at the same time, so why does not modifying this "KVM" switch work? Change the output connector to an input connector and the two input connectors to output connectors and it's ready?

[Bitch]

Okay, I have even better idea: Without having to modify the switch, just buy three "convertors" that change the "sex" of the connector and there you go. ? I checked already that there are these convertors and don't cost anything.

[Bitch]

I did even some more research. There are several solutions for this at the "local computer store", cheapest one being Y-cable for two monitors. I'm sorry I'm going on about this but I'm quite sure that there will be others facing the same problem too. It's not too nice to get to the back of the computer to switch the cable everytime when you want to use the monitor or the projector.

[Myren]

ellipsoidal is definately the best. it focuses the light where we want, with stunning uniformity too.

getting the right uniformnity is a function of how you form the parabola. i'm still working on this, i'm actually trying to build a piece of software that'll optimize it all for me.

as for actual construction, i'm mainly investigating ways to do it on a repeat scale. i'm looking at finding a way to cast the thing, either that or to stamp press four pieces which can be joined to form the main reflector. the only other option is making a steel mold and electroforming a nickle plating over it, which can then be removed and used as a base for which to line a shinier more reflective metal, which would then have some sort of reflectivity compound further rubbed on. dunno what the final solutions gonna be yet.

all these are pretty complicated solutions, but i think ultimatley it'll be worth while.

still gotta work out the math to insure the best light uniformity. you have to adjust the ellipsoidal shape appropriately to get the best uniformity, its going to take some effort.

bitch: wow, no such clue those things existed. i'm helping my friends build their own systems - friends who incidentally dont really want to have to get a new video card. so, ah, you have both my and especially their thanks. woot.

myren

myren

[jjasniew]

The Xung; what kind of 15" LCD panel are you using, that you cant get enough light through? Is it 300:1 contrast? (another concept I have no practical idea of how it matters beyond a certain point)

I went ahead and ordered the 7K lumen OHP at $150, then found another for $75. Maybe that one's good for just the bulb! I figure these ought to be bright enough...

If some sort of "deinterlacing" is needed to fix the problem I documented last night, I wish someone would come out and spell it out for me, rather than just let me wander around in the dark!

So the "venetian blind" effect has nothing to do with pixel speed, instead, that the video needs to be deinterlaced inbetween the source programme and the panel?

Axeman; How are you going to fix your panel? What happened - did it just "go out" as you were projecting through it? Where's the pictures of it apart? Do these pics show the difficulty getting the one PCB out of the way? I'm an EE; I'd give the repair a shot if you'd like, or, if you're just going to junk it. Write me at joejas@ihpc.net, if you're interested.

I tried rear projecting against a white cloth shower curtain tonight, using the 640X480 infocus panel. Dont laugh - it looked pretty decent! However, I had to angle back the top of the screen and drop the projector down, then angle up the mirror on top to get a square image. Why? because a direct shot has the projector beam source right in the center. How do they do rear projection - and not have this car headlight blasting at you - in the middle of the projected image?

Also, I noticed that the VCR tape I was using as input seemed to give somewhat less of the 'ol venetian blind effect, than did the broadcast programme I was watching last night. If my eyes werent just tricking me, I have no idea why this woud be...If anyone can enlighten me, it'd be much appreciated!

Myren, if you're going to build these professionally, you might not want to share all of it here. You may want to consult a patent attorney, I'm sure you can file for things like "novel light source reflector design for LCD projection systems". Especially is it incorporates some sort of embedded servo control to precisely position the mirrors.

[jjasniew]

http://www.fresnel-optics.com/pdf/te...s_june2001.pdf

[The Xung]

@ jjasniew: The reason why a VCR source doesn't have as bad of a venetian blind effect is because it's only 320x240 versus the 640x480 of TV so, when it was recorded, only every other line was recorded, thus a deinterlacing effect. Take a look at this thing http://www.omegamultimedia.com/produ.../cheesebox.htm though a little expensive, it might help with your interlacing effects (for some reason I have this feeling that it would be possible to find schematics of it online somewhere).

The 15 inch LCD I have is the Envision one that was on sale during presidents day at Staples with a $100 coupon and $70 rebate. It has 250:1 contrast but I think these contrast specs vary from manufacturer to manufacturer as this monitor has pretty sharp contrast.

I know I bought a metal halide bulb and I know metal halides are suppose to be more energy efficient than any other white light source so I don't know why a 175 W metal halide is not as bright as a 65 W LOA, or maybe it is. I know Myren's been using 400+ W bulbs for his LCD but I didn't want to deal with all the heat.

Everyone else who's been using a LOA or a standard projector, have you been using an LCD projection panel or monitor? and what's the contrast spec?

I suspect my problems are coming from a combination of not a bright enough bulb for such a large LCD, a higher contrast LCD than everyone whose used a LOA, and having too high goals for output size. Perhaps I need a screen instead of just a whitewash wall.



What can I get that is more reflective than aluminum foil?