I'm not sure if anyone has tried this or not yet.
After three days of looking through what seems like hundreds of plogs I had this idea.
Basically, the lcd and it's frame are stationary and built onto the sled.
The corners of all three frames have holes drilled through to feed a bolt.
Nuts are put in place to keep the rear fresnel stationary, locked to the lcd frame 15mm away.
A spring in placed between the lcd frame and the forward fresnel frame.
Finally a wingnut is placed after the front fresnel allowing 4 corner adjustments for keystoning.
I would probably install a small metric ruler at the 4 corners with a marker at the center point of the front fresel frame so I could make sure I had at least one side at least 20mm away from the lcd panel.
As you can see from my sketch the ambient light would be blocked, and there should still be plenty of air flow.
My concerns are how much larger do you think I'd need to make the holes in the frame compared to the size of the bolt to allow the frame to lean back without putting pressure on the frame and fresnel.
And do you think this would work?
Thank you in advance for any input.
Full Version: Possible Keystone Adjustment Solution
QUOTE (JCrow @ Sep 1 2006, 01:07 PM) 
I'm not sure if anyone has tried this or not yet.
After three days of looking through what seems like hundreds of plogs I had this idea.
Basically, the lcd and it's frame are stationary and built onto the sled.
The corners of all three frames have holes drilled through to feed a bolt.
Nuts are put in place to keep the rear fresnel stationary, locked to the lcd frame 15mm away.
A spring in placed between the lcd frame and the forward fresnel frame.
Finally a wingnut is placed after the front fresnel allowing 4 corner adjustments for keystoning.
I would probably install a small metric ruler at the 4 corners with a marker at the center point of the front fresel frame so I could make sure I had at least one side at least 20mm away from the lcd panel.
As you can see from my sketch the ambient light would be blocked, and there should still be plenty of air flow.
My concerns are how much larger do you think I'd need to make the holes in the frame compared to the size of the bolt to allow the frame to lean back without putting pressure on the frame and fresnel.
And do you think this would work?
Thank you in advance for any input.
After three days of looking through what seems like hundreds of plogs I had this idea.
Basically, the lcd and it's frame are stationary and built onto the sled.
The corners of all three frames have holes drilled through to feed a bolt.
Nuts are put in place to keep the rear fresnel stationary, locked to the lcd frame 15mm away.
A spring in placed between the lcd frame and the forward fresnel frame.
Finally a wingnut is placed after the front fresnel allowing 4 corner adjustments for keystoning.
I would probably install a small metric ruler at the 4 corners with a marker at the center point of the front fresel frame so I could make sure I had at least one side at least 20mm away from the lcd panel.
As you can see from my sketch the ambient light would be blocked, and there should still be plenty of air flow.
My concerns are how much larger do you think I'd need to make the holes in the frame compared to the size of the bolt to allow the frame to lean back without putting pressure on the frame and fresnel.
And do you think this would work?
Thank you in advance for any input.
I think that would work fine. The holes would probably have to be just slightly oblong (depending on the thickness of the frame). If your holes are 0.25" in diameter I'd bet 0.375" would be long enough if the frame was 0.125".
I'd say that although it would work, it would likely be less user friendly than a pivot point in the middle of the X axis of the field fresnel. With 4 wing nuts you'd have to make the keystone adjustment manually, with the middle pivot you can let gravity do the adjusting...
Looks like a good idea. Regarding the size of the holes for the frame, I don't know if they'd need to be larger, maybe just drilled at an angle, unless you'd need to keystone the other way too, which I don't see happening since you generally don't move your PJ from floor to ceiling that often. EDIT: Hirudin got to it before me and he explained it better too...
One thing I would think about is lining the inside of the holes in the frame with something slick so the threads don't get caught on the wood - that's so annoying - you have to twist your frames or put them back and inch them along.
I had an idea for keystoning too before, but I didn't get much feedback on it so I guess it was dumb; but I liked the smoothness in sliding it presented: http://mohannedhassan.com/ll/keystone_setup.jpg Maybe you can improve upon it: (scroll down a bit: http://www.lumenlab.com/forums/index.php?s...st&p=147771)
Someone else on here was also experimenting with magnets to hold their bulb and reflector. Maybe there's potential in that for keystoning too.
One thing I would think about is lining the inside of the holes in the frame with something slick so the threads don't get caught on the wood - that's so annoying - you have to twist your frames or put them back and inch them along.
I had an idea for keystoning too before, but I didn't get much feedback on it so I guess it was dumb; but I liked the smoothness in sliding it presented: http://mohannedhassan.com/ll/keystone_setup.jpg Maybe you can improve upon it: (scroll down a bit: http://www.lumenlab.com/forums/index.php?s...st&p=147771)
Someone else on here was also experimenting with magnets to hold their bulb and reflector. Maybe there's potential in that for keystoning too.
Hirudin - Thanks for the input. The reason I'm looking at the 4 axis pivot as opposed to a central gravity pivot is versitality in many applications. Currently I'm in an apartment with some space issues, so I may need to have the projector to the side of the screen, not in front of it. So i horizontal keystoning correction. But one day I hope to have a house with space, and if I'm going to build this, I'll probably only want to do it once, so i'd like to be able to use it straight on as well. Of course it may end up on a shorter table, hence I need vertical keystoning correction.
Also i want to make sure that if I set it, it's locked. That way if somone bumps the table I won't have to stop the movei/game to re-aim the lens.
Mohanned - I saw your concept while searching the boards. It's an interesting idea, but I can see some issues.
From what I read, at least one edge of the frensel must be 20mm from the lcd. In your example the bottom of the screen is as far down as it can go, and you'd need to see if that distance was longer than 20mm. Second, i'd be worried about the lens slipping once it was in place. It looks like there are just screws holding the brackets now. Which means every time you would want to readjust it, you'd need to be able to get a screwdriver down in there to loosen and retighten the screws. My last concern would be how far they stick out. I'd be worried they would catch some light and reflect causing artifacts in the lens. I don't think they would directly interupt the projection due to the light path, but they may catch a glare.
Also i want to make sure that if I set it, it's locked. That way if somone bumps the table I won't have to stop the movei/game to re-aim the lens.
Mohanned - I saw your concept while searching the boards. It's an interesting idea, but I can see some issues.
From what I read, at least one edge of the frensel must be 20mm from the lcd. In your example the bottom of the screen is as far down as it can go, and you'd need to see if that distance was longer than 20mm. Second, i'd be worried about the lens slipping once it was in place. It looks like there are just screws holding the brackets now. Which means every time you would want to readjust it, you'd need to be able to get a screwdriver down in there to loosen and retighten the screws. My last concern would be how far they stick out. I'd be worried they would catch some light and reflect causing artifacts in the lens. I don't think they would directly interupt the projection due to the light path, but they may catch a glare.
QUOTE (JCrow @ Sep 1 2006, 04:29 PM)
Hirudin - Thanks for the input. The reason I'm looking at the 4 axis pivot as opposed to a central gravity pivot is versitality in many applications. Currently I'm in an apartment with some space issues, so I may need to have the projector to the side of the screen, not in front of it. So i horizontal keystoning correction. But one day I hope to have a house with space, and if I'm going to build this, I'll probably only want to do it once, so i'd like to be able to use it straight on as well. Of course it may end up on a shorter table, hence I need vertical keystoning correction.
Also i want to make sure that if I set it, it's locked. That way if somone bumps the table I won't have to stop the movei/game to re-aim the lens.
Mohanned - I saw your concept while searching the boards. It's an interesting idea, but I can see some issues.
From what I read, at least one edge of the frensel must be 20mm from the lcd. In your example the bottom of the screen is as far down as it can go, and you'd need to see if that distance was longer than 20mm. Second, i'd be worried about the lens slipping once it was in place. It looks like there are just screws holding the brackets now. Which means every time you would want to readjust it, you'd need to be able to get a screwdriver down in there to loosen and retighten the screws. My last concern would be how far they stick out. I'd be worried they would catch some light and reflect causing artifacts in the lens. I don't think they would directly interupt the projection due to the light path, but they may catch a glare.
Also i want to make sure that if I set it, it's locked. That way if somone bumps the table I won't have to stop the movei/game to re-aim the lens.
Mohanned - I saw your concept while searching the boards. It's an interesting idea, but I can see some issues.
From what I read, at least one edge of the frensel must be 20mm from the lcd. In your example the bottom of the screen is as far down as it can go, and you'd need to see if that distance was longer than 20mm. Second, i'd be worried about the lens slipping once it was in place. It looks like there are just screws holding the brackets now. Which means every time you would want to readjust it, you'd need to be able to get a screwdriver down in there to loosen and retighten the screws. My last concern would be how far they stick out. I'd be worried they would catch some light and reflect causing artifacts in the lens. I don't think they would directly interupt the projection due to the light path, but they may catch a glare.
Well, since you need 4 axis pivot, my idea is not any good to you I guess.
But, I'm not sure what you mean by "the bottom of the screen is as far down as it can go..."
As for the lens/frame slipping there's no chance of that. Those rails are used for lid supports and they're very tightly secured, you have to push a little hard to get them to move so wherever you move them is wherever they stay - that's one of the reasons I thought it would be good - no screwdriver at all.
http://mohannedhassan.com/ll/keystone_lid_support.jpg
As for them sticking out, they could be painted a flat black or sanded to a dull sheen so they won't interfere. I figure they'd be about the same as the threaded rods we all use - those are sticking out in the front half of the PJ too - granted there isn't as much metal.
Anyway, it's not that good of an idea. If I get some time I'll try to mock it up with some foamcore or something, but for now your idea is best for you at least.
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