| Author | Message | ||
     clyde Rating: N/A |
Hi I wanted to know.. (after much dabbling with anaglyph 3d).. .. How does a silver screen (rear projection coated) retain or transmit light in the same direction it came from? I mean if i rear project polarized light from two projectors onto the screen material, im assuming the "silver" coating is on the rear side of the screen right? so how does a view in front of the screen see a correctly polarized image vai PASSIVE 3d glasses? Any help appreciated Clyde | ||
| M.H. Rating: N/A |
Simple answer on your question YES. The silver coated screen surface relfect the light without changing the polarization ... This is all . | ||
| clyde Rating: N/A |
erm...MH. thanks for the answer  But read my question a little more slowly..ok I'll break the question down... I have a 2 projectors (with polarizing filters for left view/rightview) mounted "behind" the screen. IF the Silver Coating is on the front surface of the screen....Ie. facing the audience, HOW does it retain the polariziation of light hitting it from behind? What I want to know is, Is there a "special" kind of Silver Screen for Rear Projection?? and if so , How exactly does it work?? Thanks and Regards Clyde | ||
| M.H. Rating: N/A |
I overloked the you speak about rear ... For rear you do not use silver coating, but material with pass trhough light ... The best material are special desk made from glass fibres ... But most standard rear screen materials works O.K. - but should be tested ... | ||
| clyde Rating: N/A |
hmm.. ok I kind of understand now. For a rear-projection setup, you just use a good quality rear projection material thats all? wow! this sounds good then. I'm assuming you mean taht the light will just pass thru the material and into the passive polarized glasses that a viewr will be wearing . and so the light coming from the projector wouldnt be altered or deflected by the rear screen material right? If this is true, then it eliminates teh need for a silver coated screen altogether Regards Clyde | ||
| M.H. Rating: |
Most good rear projection amterial do not depolarize ... But with the rear projection - you have some other problems - you must have a lot of space behind the screen ... If you will use projectors with short lences - you will fall in problems with sweetspot and direction fo the light going out form the screen ... Soution is using a mirror tho shorten the distance ... But this makes problems related to non-doparzing on the miror + you will need realy big mirror. | ||
| clyde Rating: N/A |
thanks again MH. You obviously know a lot about the practical problems one might face with polarized projection (particularly rear-projection). I would appreciate if in your spare time you can write me about your setup (if you have a rear projection setup) or some resources on the internet realting to technical considerations for dealing in polarized projection. One other thing: Between Circular and linear polarization, the only difference is that in liner you cant tilt your head right? regards Clyde | ||
| itsikw Rating: N/A |
Clyde, do not assume that a rear projection screen preserves polarization unless approved by manufacturer or tested. There are a few materials that serve this function well, but many screens are unsuitable for rear passive 3D display. Regarding your polarization question, you are right, but there are three 'buts': 1. The crosstalk (ghostins) with circular polarizers is much higher 2. Circular polarizers are much more expensive 3. It is true that the performance of circular polarizers is independent of angle, but the 3D display quality is degraded by head tilt. In particular, if you tilt your head (theoretically) by 90 deg, the parallax will become purely perpendicular, and 3D perception will be replaced by headache. Therefore, it is generally recommended to use planar polarizers. Circular polarizers are preferred only in special circumstances. | ||
| clyde Rating: N/A |
Hi Itsikw, Thank you for these little pieces of advice. Im making a small document of such advice from you and MH and maybe will post it soon along with other information on Polarized stereo for newbies/beginners. from previos posts by MH , I've learnt about a company Berezin Stereo. are there any other such companies offering a reasonable turnkey system to do polarized stereo? for example: a cheap source for passive polarized glasses (linear) Supplier of Polarizing filters for projectors (and do these come in a standard lens filter that screws on to a projector) or do the polarizers come in sheets and can simply be cut with scissors and taped to the front of a projector lens. Most important: whats the best recommended supplier of Backprojection screens for Polarized stereo. and whats the biggest size available for front projection screens (actually I could just place to front projection silver screens side by side to make a bigger screen right?) Regards Clyde | ||
| itsikw Rating: N/A |
I personally make and sell passive 3D projection displays. I also make and sell filters with mounting accessories for such displays. My filters are marketed in www.silverfabric.com. In this site you will also find excellent screens, both for front and for rear projection. Other brands for rear projection that I have tested are Stewart and DNP. You are invited to drop me an e-mail (itsikw at advisol.co.il) and visit my site (www.advisol.co.il). | ||
| M.H. Rating: N/A |
Clyde: There is a small problem related to information exchange - most companies prefer to sell to the user a complet solution, instead of giving him exact specification how to make everything itself :-(. My information are based on consultations with several comapnies witch put together stereo setup - but they usualy do not give you exact specification of the material used + precise optic characteristic. In addition there are very great diferences in the material quality - e.g. the silver screen light gain and ghosting. You can have a silver screen alost for free by painting something by silver spray can, on you can have sphisticated materials as the SilverFabric or Stewart one ... I do not have rear setup. I have SilverFabric material based front screen. I was participating in making several rear based projections setups - but in all cases the suplier refuse to give the material characteristics. | ||
| Anonymous Rating: N/A |
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| Anonymous Rating: N/A |
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| Anonymous Rating: N/A |
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