DIY Video Projector

[Axeman]

I have the screen re-assembled right now, but I know that the actual glass LCD panel was probably about 1/2cm thick, or for you imperial folk, about 1/4"ish. Very thin.

[fender4]

I like the idea of the reflective LCD for the sake of simplicity, but in my opinion, I think this approach may present a few problems. If I understand the concept correctly, the light will need to enter the LCD and strike the reflective surface at some anygle other than perpendicular to the LCD so the light source isn't obstructing the reflective image. This should be possible if the pixel size is relatively large because the chances of the entering light and exiting light striking the same pixels will be higher. However, with higher resolution LCD, the pixel size is usually relatively small. This could lead to the light striking one pixel as it enters the LCD, reflecting at an angle, and striking a different pixel as it leaves. This would probably give the impression of lower resolution.

This may not be the case, so don't let it discourage anyone from trying it. It would definitely allow the use of many displays that were previously unusable for this purpose, and I am very much in favor of that. Does anyone have any ideas concerning this? I'm hoping someone can prove me wrong, so fire away.

Good luck with everything.

-f4

[xblocker]

fender4,

You gave the answer yourself!

1. Because of the little distance between LCD-panel and fresnel-mirror you will have a setoff for all reflected beams that don't pass exactly the middle of th panel.Make a drawing and consider the lightpath also for the beams at the corners of the panel.
Remember:angle of incidence = angle of output.
2. Consider the loss of brightness through the panel. If the panel let 10% of light transmit the way down it does the same when the light comes up again.
3. There would be a heat trap problem between mirror and panel.

My opinion: forget it!

xblocker

[fender4]

Thanks, xblocker. I had a feeling that would be the case. I didn't think about the heat trapping effect...good call.

Muzzman,
Thanks for the input. The Sharp panel I had was advertised as a TFT, but it was an odd arrangement of pins surrounding the active area of the panel. I'm really not sure what was going on with that. Luckily I was able to return it for a refund. I will look into the PS1 LCD...that resolution should be fine for me as I will mostly be using it for movies on a roughly 60" screen.

-f4

[jjasniew]

And am not sure if I wasted $150...

The metal halide OHPs are quite the complicated beast. Two fans and it roars when in operation. It's got a full fledged power supply, with ICs and chokes and big heat sinks. Daughter cards with more ICs. This giant flyback transformer that hooks to the bulb. A far cry from the Duke 4003 which had a few switches, a couple diodes and a resistor.

It's so bright inside the thing that you cant even look through the big fan, you burn your eyes; not kidding.

The @#%^&()^ arm that holds the overhead mirror and lens is really crappy; I had to like bend it to get the lens at a right angle to the stage. This, from supposedly a multi K$ machine...The Duke, in contrast, has an adjustment to set this.

The light is super bright in high intensity mode, but not perfectly uniform. We'll see if that gets better after a good cleaning.

Aside from this, I did have a bit of luck. The place I bought it from just happened to have a broken Nview Z350. I had em send it along for an extra $40. Only 2/3 of the screen had active pixels when I turned it on. So, I opened it up, poked and prodded and was lucky to see some changes in the LCD when I pushed on this circuit card off to one edge.

I was even luckier when I removed the LCD, took the EMI shield off and noticed that a couple of flex-print conductors that looked like it was connected to a driver chip had desoldered from this PCB. (I could just see the flex print move when touched. The driver chips must get really hot) So I reflow soldered each connection back down, cleaning up my solder bridges with the chem-wick, retouching 15 or so connections. So, soldering these kinds of tiny connections can be done. It's just somehow easier to do on a $40 panel than a $300 panel, you're not quite so nervous.

Even luckier was I when I put this back into the panel, hooked it all up, powered on and the entire LCD now shows an image! I reversed the panel fan, so it blows in the same direction as my other unit. I think this was a problem on these panels, because the fan on my other one blows out through the air filter element, which the manual says to keep clean, so dust doesnt get on the inside panel glass. That's not logical, so they mustve reversed it because the panels were all burning up and maybe that fixed it.

The thickness of this LCD element was appx 1/8". I'd think the newer ones would be even thinner, but, who knows?

Anyway, I'm writing this on a 50" screen, using my new Elmo projector and the repaired Z350.

I cant convince myself that the reflective mode OHP will definitely work, using an LCD panel with the reflector lens mounted right on the back. I cant even crank through how it would work with a transparency! The only part I understand is without any interferance, the fresnel reflector collumnates the light so its equal brightness across the stage area, with the direction being straight up.

[Axeman]

Hey.

jjasniew -

Nice screenshot!! So did you just get a spare panel the same as your existing one? The color looks a little off, but the contrast looks pretty good! I _highly_ recommend a capture card+dscaler to send TV/composite/s-video to your projector. I've been experimenting with it for a few days and it can make TV look better than I ever thought it could. ONly problem is I can't get stereo sound from my TV tuner.

I almost bought a projector from Ebay last night. Don't banish me from the DIY brotherhood!! I'm sure the reason that a lot of us are doing this project is because we just want a projector! This was an 800x600 500 lumen 250:1 contrast ratio projector on ebay- "Buy it now for US$250". Someone got to it before I caved. Mabye it's better that way. Going to either get my $$ back or a new Rad5 hopefully in a few days, don't know where I'll go from there. I'm just a rambling man....

[Axeman]

jjasniew

So does this mean you have an extra Nview panel? Would you be willing to sell it? What are the specs Ie. Contrast, response time, etc. Thanks!

[xblocker]

If you wanna see some easter eggs look here:

http://cgi.ebay.de/ws/eBayISAPI.dll?...tem=1338117492
and here:
http://cgi.ebay.de/ws/eBayISAPI.dll?...tem=1337877173

I never saw such an offer..! (Couldn't resist to show it here)

xblocker

[jjasniew]

Axeman,

Write me off line about this. joejas@ihpc.net

[Bitch]

this is just **** msg...