Ok I have searched and can't seem to find anything on the amount of light loss you would experience using Front Surface Mirrors to fold the focal distance required by the lenses in a projector. I know that regular mirror cause a lot of light loss but I'm unsure about the front surface variety.
It depends. High quality front surface mirrors can reflect up to 99% of visible light. The supplier should have this info listed on their web site.
WOW!! That's a lot better than I was hoping. I guess FSM are the way to go if you want to incorporate mirrors into your design.
About six or seven years ago I was on the road with a corporate show for Ford Motors. At one gig in Hanover, the laser guys had a bit of a crisis, when one of the local crew pushed the flightcase with all their mirrors in off the back of the truck with no ramp present. They were a little upset, not only because the box contained £5000 worh of laser optics and mirrors, but because the show was next day, and they had no time to get any more shipped out, (BTW, there is a point to this, and I'll get there shortly😉).
So, one of the Ford Demo drivers was walking past as these guys were trying to see if anything was fixable, and pointed out that one of the cars on display, ( unfortunately I can't remember which🙁) used surface silvered wing mirrors and a call was imeadiately sent out to to the local main dealers, and their entire stock of mirrors was called in, and with a little epoxy, the show was up and running!
So, the point, if you're looking for surface silvered mirrors, it might pay to pop down to your local car scrapyard and see what you can find😉
So, one of the Ford Demo drivers was walking past as these guys were trying to see if anything was fixable, and pointed out that one of the cars on display, ( unfortunately I can't remember which🙁) used surface silvered wing mirrors and a call was imeadiately sent out to to the local main dealers, and their entire stock of mirrors was called in, and with a little epoxy, the show was up and running!
So, the point, if you're looking for surface silvered mirrors, it might pay to pop down to your local car scrapyard and see what you can find😉
What's a good useable size for a projection mirror? I was going to use 12"x12" mirrored tile until I found out about the light loss from second surface mirrors.
I've been tooling around Edmund's and prices vary widely depending on size, coating (gold, aluminum) and substrate material (float glass, pyrex, etc).
And, of course, all their FSM's (they call them First Surface Mirrors) are small or cost a small fortune. Their circular ones are typically no larger than 75mm (3") and the affordable rectangular ones are only 85mm x 101mm (3.25"x4").
Their large format FSM's run from $29.80 for 102mm x 127mm to $245.00 for 408mm x 609mm -- closest thing to a 12" square is 254mm x 313mm and tagged at $77.40!
Is there somewhere better to buy from or am I doomed to using an inexpensive SSM?
I've been tooling around Edmund's and prices vary widely depending on size, coating (gold, aluminum) and substrate material (float glass, pyrex, etc).
And, of course, all their FSM's (they call them First Surface Mirrors) are small or cost a small fortune. Their circular ones are typically no larger than 75mm (3") and the affordable rectangular ones are only 85mm x 101mm (3.25"x4").
Their large format FSM's run from $29.80 for 102mm x 127mm to $245.00 for 408mm x 609mm -- closest thing to a 12" square is 254mm x 313mm and tagged at $77.40!
Is there somewhere better to buy from or am I doomed to using an inexpensive SSM?
OK, American Science & Surplus has some FSM's for a more affordable range of $2.00 - $3.75, but the largest of any of them are only 160mm x 183mm and 5"x8"
http://www.sciplus.com/category.cfm?subsection=21&category=190
Surplus Shed only has an oddly cut 7-7/8" x 4" at $28 and a couple others not far off the that size or smaller for a few bucks.
http://www.surplusshed.com/pages/Mirrors.html
My usual search sources are not being very helpful...
http://www.sciplus.com/category.cfm?subsection=21&category=190
Surplus Shed only has an oddly cut 7-7/8" x 4" at $28 and a couple others not far off the that size or smaller for a few bucks.
http://www.surplusshed.com/pages/Mirrors.html
My usual search sources are not being very helpful...
Ok, correct me if I'm wrong here but isn't the size of the mirror needed dictated by where in the design you place it? I mean that the closer to a lens (condensor or projection) you place it the smaller the mirror needs to be. The closer to the lcd you place it, the larger it will need to be. Look at the mirrors they use already in OHP's, their not that big. I have two already and might just use them.
Alright... not sure if this scoop has been posted before, but Front/First Surface Mirrors are commonly used in stained glass and kaleidoscope construction.
So, you can probably find some FSM at your local craft store or glass shop (who can also cut to size if you don't own the proper tools). I sincerely doubt their reflectivity approaches the 94%-97% seen in optical grade products, but it may do just fine in a DIY projector application -- at least it'll be better than SSM.
So, you can probably find some FSM at your local craft store or glass shop (who can also cut to size if you don't own the proper tools). I sincerely doubt their reflectivity approaches the 94%-97% seen in optical grade products, but it may do just fine in a DIY projector application -- at least it'll be better than SSM.
77 bucks for a Front Surface Mirror is a GREAT price... you kidding me!
DONT USE REGULAR MIRRORS!!! PERIOD. Dont cheap out. They're expensive for a reason! 2nd surface mirrors should NEVER be used in projection. If you dont believe me buy one and try it... then try the front surface and tell me if you see a difference.
And yes the size does depend on your case design. If your building it OHP style with the projection lens before the mirror you can get away with a small 4x4". But it your putting it before the projection lens it needs to be much larger, on a 45 degree angle and should be in the shape of a Isosceles Trapezoid. The size and cut depends on your design.
-John
DONT USE REGULAR MIRRORS!!! PERIOD. Dont cheap out. They're expensive for a reason! 2nd surface mirrors should NEVER be used in projection. If you dont believe me buy one and try it... then try the front surface and tell me if you see a difference.
And yes the size does depend on your case design. If your building it OHP style with the projection lens before the mirror you can get away with a small 4x4". But it your putting it before the projection lens it needs to be much larger, on a 45 degree angle and should be in the shape of a Isosceles Trapezoid. The size and cut depends on your design.
-John
jcbklyny -- I get that SSM is inferior (double image, shadow, light loss) but does anyone have any comment on the "surplus grade" or "craft grade" FSM's?
This is a simple mockup of what I'm trying to do -- basically along the lines of DIY Labs' Mark II. So now you can see why $77 FSM's would hurt the wallet!
This is a simple mockup of what I'm trying to do -- basically along the lines of DIY Labs' Mark II. So now you can see why $77 FSM's would hurt the wallet!
An externally hosted image should be here but it was not working when we last tested it.
Just a thought arnt automotive review and side mirrors front surface? I think they are, would that be a cheaper option for some of you? just a thought
possible solution?
I have in my possesion 100 +/- 3in x 3in aluminum plates I lifted from where I used to work they are smooth and flat. they would need to be polished.
The size may not work but for experimental purposes thye may be great and who knows they may actually do great.
I have in my possesion 100 +/- 3in x 3in aluminum plates I lifted from where I used to work they are smooth and flat. they would need to be polished.
The size may not work but for experimental purposes thye may be great and who knows they may actually do great.
Not all automotive mirrors are FSM and the problem with rear view mirrors (the one attached to your windshield) is that while the front surface is mirrored, it allows some light to pass through and the rear (second) surface is at another angle (sort of like a prism) and mirrored as well. That's why you have to flip the little lever that changes the angle of the view.
Hmm....
3" square, eh? . . . i could try to tile them for a reflective array or some other application... maybe I'll just glue them over my bed! 😉
3" square, eh? . . . i could try to tile them for a reflective array or some other application... maybe I'll just glue them over my bed! 😉
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