So I finally got my LCD-OP working, and it looked awesome when I first turned it on. However, the image was flipped! So I flipped the screen over, and now I can't see anything at all on my wall, just barely a little bit of ambient light. Is there a film that needs to be removed on the LCD that only allows light to go in one direction?



THanks

Can you post any pictures?
Does flipping it back over (so it's reversed again) produce an image, again?

Well, I investigated with a razor blade. When I turn it on nothing is displayed now. Found out that I removed the polarizer, and the initial prob was that part of the electrical cord was snagged on an internal mirror, so most of the light did not reflect through the screen even though the projector appeared as bright... So now I guess I'll have to by some film polarizer.

On that note, is it possible to attach a small polarizer onto the triplet somehow and produce the same results?

Questionable, depending on the quality of polar film you obtain (check polarization.com) some members have claimed a difference of opinion. The trick is dialing a triplet place polar opposite diagonally to the remaining polar thats on LCD for it work. From there it's the quality of your blacks that's the issue. Look up super high contrast polar.

Thanks for your replies guys.

I've experimented with the piece of polar-ag sandwich I pulled off... It appears to work anywhere as a polarizer, with varying contrast, as long as I orient it correctly. I can even walk up to the wall the image is supposed to be projected to, hold up a piece of polar-ag sandwich and see the intended image, holding it only two inches away from the wall!

I think the drop in contrast is due to somehow interfering unpolarized external light, so the closer I get the sandwich to the LCD panel the better. I think I might grab a polar lens from walmart and do some experimenting near the triplet with that.

The sandwich drastically reduced sharpness near the triplet because of the AG. I used the idea of adhesive tape from an earlier thread to fill in the "pits" of the AG, It helped a lot. Thanks to whomever came up with that.

One thing I really want to investigate is that AG though. As I mentioned before my panel was originally flipped over on the wrong side. So that it was: light, ag, polar, LCD, polar, triplet.... The picture was "flipped over" on the screen. So that "Right" read "thgiR" if that makes sense. But what was surprising was the brightness, as compared to it being flipped over the correct way. I think there might have been a difference. Somehow the AG smooths out the light, makes it softer? Logically it seems the pits would reflect more light back to random directions at it's source instead of passing through. I have a piece of AG i pulled from another panel with no polar on it. I think I'll play with that too.

Um. Unless your projector is folded, the AG surface is supposed to go towards the lamp. Looking at the LCD through the projection triplet, the image should appear to be backwards and upside down. O)h right. OHP projector, so that is a folded build.

The triplet inverts the image when it focuses, and then it reflecting off of the screen reverses it.

In any case, that's irellevant to the issue, which is now the need for a replacement polariser.

I personally feel that the closer the polariser is to the LCD, the better it performs, with the least potential for interference in the image. It does, as you've noted, work just fine anywhere on the correct side of the LCD.

Right, I'm using an OHP.

Stores such as Walmart and Bestbuy carry "Circular Polarizer". In that description, does circular mean the spec of the polarizer, or just the shape of the lens? I understand that I need linear.

Hmmmm...never disected circular polar but basically it's the specification of the type of polar. Circular polar, of course allows light to pass in a circular wave whilst linear in a straight wave. When a linear polar begins to 'grain' the polar itself comes up in frayed strands diagonal to the sheet itself.

Hey thanks for the input guys. I went ahead and bought a circular polarizer at Best Buy. It works okay. Not the kind of contrast that a film polar would have, but it'll do for now, in fact I'm using the OHP right now to type this reply!

Just so I understand what you have Blind. Your saying that your using a circular polar combined with the remaining linear polar that's still on the LCD? And is this circular polar placed at the triplet or butted up against the bare side of the panel? If able, can you also provide us pictures of the setup as well as a visual of your projected image?

That's correct, except the polarizer is simply taped butted up before the triplet, so the order is:

Light-->internal OHP mirror-->original linear polarizer film-->LCD panel-->bare glass of panel-->circular polarizer (camera type)-->triplet-->external OHP mirror--> image.

I was surprised it worked. Glad I didn't have to order some film and hope that it was the right size and right orientation.

I think it might have had something to do with the lucky charms box I used to cover the controller.

Ok, this is a first, for me that is. Never heard of anyone using circular with linear since the AG removal discovery days. I would have expected worst but looking at the pics it's pretty darn watchable. Unless I miss any attempted by others of this kind, I'd consider this a new discovery for the books. Good job Blind.

And here I was, chuckling to myself, waiting for somebody to tell Blindside that a circular polarizer would not work as a replacement. I'm no expert on polarizer, so I decided to let those more knowledgeable chime in.
And now I hear that it works. Go figure.
Congrats on the fix, Blindside.

A circular polariser will work used in this manner. Where it won’t work is if it were used as the rear polariser. If you look at what a circular polariser is, a linear polariser and a ¼ wave retarder, it makes sense. The light leaving the LCD is linear polarised light, it passes through the retarder and it is effectively rotated 45°, it can then pass through the linear polariser if it is aligned correctly. If it were possible to remove the retarder from the circular polariser then you would find that the filter would need to rotate for correct operation again.

Wish I could take the credit for this guys, but its due to pbassjams a few months ago...

I was just lucky to have dug this up:

http://www.lumenlab.com/forums/index.php?showtopic=26371

He gave it a shot even when he was denied!

But if it wasn't clear then it is now...and literally so.