DIY Video Projector

[gmshroll]

OK, you want a question - can you get hold of XGA LCD panels from infocus projectors from spare parts? $200 would be fine!

Graham

[Andrew Steele]

lol, gmshroll

hey soje, good to have you here.

with the LED's, the main two problems at the moment with them are; you have to hook up alot at the moment to get enough brightness, and also how the LED's actrually produce the white light, and the way they are doing it now does not produce an even colour spectrum, it just looks white to the human eye, but when you shine it through an LCD panel this is evident as some colours are not produced properly. When LED's are making alot more light and the light is even throughout the colour spectrum I think it will be very worthwhile to look into.

I have a Q. for you... the LCD's used in the projectors, I know the majority use a 3 LCD configuration with Red, Blue, Green. But libht loss throught the LCD... do you guys have the same problems as the guys in this forum? they are speaking of 90% light loss through the LCD panel, or do you have special ones that are made with projection in mind? Also DLP projectors... seing they reflect the light... is there much light loss from them? I imagine not.

thanks for any questions answered...

Reguards, Andrew

[vdi_nenna]

Just what we need, an expert. Can you tell us what area you work in?

The LED idea is still on my wish list. But I think it will be a couple of years til they are strong enough and more effecient to run as a source of light for projectors.

I have a cluster of 48 with 5600 miro candals each or 5.6 mC each. It's bright, but looses force through the LCD.

The guys have a bunch of different ideas and they are starting to come together.


Vince

[soje]

To All,

Ok I understand now that there are many curious people out there.

As I wrote in my first post, I decide what to answere. I you don't get an answere, you take a hint. OK.

Sorry Graham.

Andrew,
Yes you loose a lot of light. Not shur about the %. It varies with the resolution and the size of the panels.

In ex. 1.3" xga has a better throughput than 0.7" xga

So far there are 3 panels in use 1 for each color; red, green and blue.

Dividing the light into three different directions and let it go throug different colorglasses absorbs much light. And the engine itself does too.

Also new LCD technique makes it easier to make panels brighter.

Yes the panels are specially made for projectors and/or projection.
Imagine a panel that are 0.7" and has XGA (1024 x 768) resolution. You need a lot of light.

DLP's reflect the light, thats right. DLP projectors have much of the same light-treatments ( sorry no better word for it, I come from Norway) as LCD does, the difference is the light-wheel in DLP's and the color-glasses and LCD's in LCD-projectors.

Sorry, have to go. Will answere more later on.

Regards, Sondre

[lokost]

Has anyone seen one of these? I'd like to try an opaque projection scheme with it.

http://www.idg.net/idgns/2000/04/25/...DForCell.shtml

[Flagre]

Hah! Soje you're the man! I live in Råde...

[Forrest]

dichroic reflectors anyone?

[soje]

Hello again to all of you!

Vince, my area is electronics(development). I haven't been long in this game, so I'm hardly an expert. YET. Been here for five months, still learning but allready learned a lot. Trying to learn some of the optics too.

Iokost, this seem to be something to come. Reflective LCD's. The size of this particular LCD isn't what you would want in a projector. 720x240 pixels gives 3:1. Widescreen is 16:9 or 1.777....:1, and superwide is 2.35:1. You need a lot of scaling forcing you not to use a alot of the panels. In practice this will give you a grey frame on the side of the picture. But if there is a LCD with 16:9 or 2.35:1 we are talking business.
But as Vince are constantly thinking about, invention. We shouldn't be surprised if the widescreen get's wider in the years to come. I guess this is an invitation for George Lucas.

Flagre, du trenger ikke skrive på engelsk til meg.
In english for everyone that don't understand norwegian: Flagre, you don't have to write in english to me. Where do you go to school Flagre? And what area of interest?

I apologize to anyone that hoped I was an expert, wich I'm not.

Sondre

[vdi_nenna]

Forrest,

Dichrotic reflectors- do you need to know what they are or where to get them?

They absorb all light except one color, the color that is reflected. COuld be a mirror or a lense, I believe.

www.edmundoptics.com sells them.

soje, ok, at least you are in the business...

Vince

[Tim]

I have found a front surface mirror at a local glass shop. It is 22" X 32" for $35.00 not to bad a price. This should be big enough to fold the optics in HALF giving me a 60" rear projection TV that is no more than 2 feet deep.

The rear projection screen I have is 48X36, it is what they call black strip screen, meaning it has black stripes between the vertical lenticular lines(lenses) on the front surface of the screen.
This is to abnsorb the ambient light within the viewing room. It also enhances the dark contrast.
Has anyone been able to use a high gain front projection screen?

IMHO I think that a high gain screen is the key to the whole system. This is apparent in the fact that I am only useing 1 LOA light, 6 inches behind the lcd screen. The screen eliminates all the hot spots. And drastically improves the the dark contrast

thanks