Specs for solid prisms
Does anyone know the specs for the solid versions of the prisms?
What are the Prismasonic dimensions and angles?
There is a company in the UK (and probably one in the US) that will make solid glass prisms based on specs provided.
But what specs?
Is there a formula that could be used?
Does anyone know the specs for the solid versions of the prisms?
What are the Prismasonic dimensions and angles?
There is a company in the UK (and probably one in the US) that will make solid glass prisms based on specs provided.
But what specs?
Is there a formula that could be used?
Here's a downloadable program for calculating optics:
http://www.astrion.de/download/download.html
I downloaded it but couldn't make much sense of it, but I haven't tried very hard either.
Tor Arne
http://www.astrion.de/download/download.html
I downloaded it but couldn't make much sense of it, but I haven't tried very hard either.
Tor Arne
What do you think of the concept of using a solid prism over a water/oil prism.
If I had a 2 special blocks of glass that could be cut with a standard knife and then cut them at some angle, is that a prism?
Is it just the glass that is bending the light?
If so, what about using a optically clear liquid plastic and form a prism?
Or have a prism manufacturer create the prisms?
Is it all about the angles involved or are the materials special?
Last question, have you ever tried putting the prisms on their sides and see if that makes an expansion lens?
If I had a 2 special blocks of glass that could be cut with a standard knife and then cut them at some angle, is that a prism?
Is it just the glass that is bending the light?
If so, what about using a optically clear liquid plastic and form a prism?
Or have a prism manufacturer create the prisms?
Is it all about the angles involved or are the materials special?
Last question, have you ever tried putting the prisms on their sides and see if that makes an expansion lens?
The reason that two prisms are normally used (oil/water) is the same reason that good quality optics use doublet lenses (glass/flint).
It is to correct for chromatic aberation.
The prism is the simplest way to demonstrate this - hold a classic glass prism up to white light and it will disperse it into its constituent colours. A lens is just a curved prism, and will also disperse light into its constituent colours. The shorter the focal length, the more the dispersion.
This is due to the refractive index actually being different for different wavelengths of light.
In optics, an achromatic converging lens is produced by matching a glass converging lens with a flint diverging lens. If the lenses are matched for chromatic distortion (the flint cancels out the chromatic distortion of the glass), the overall produced lens is still converging (glass has a more consistent overall refractive index than flint).
Thus, you get the classic achromatic doublet.
That is all that is going on with the two prisms (oil and water): their chromatic distortion properties cancel while allowing for an overall bending of the light.
You could do it with any two refractive media - as long as a balance can be achieved where the two prism materials cancel out the chromatic dispersion while giving an overall converging effect.
Thus if you could get the correct formulae and find appropriate materials from amongst the liquid plastics, transparent epoxies, glass etc. you would be able to make your prisms without TOO much trouble (people are able to grind their own reflectors for telescopes, which are FAR more difficult to do acurately than plane surfaces...)
Bill.
It is to correct for chromatic aberation.
The prism is the simplest way to demonstrate this - hold a classic glass prism up to white light and it will disperse it into its constituent colours. A lens is just a curved prism, and will also disperse light into its constituent colours. The shorter the focal length, the more the dispersion.
This is due to the refractive index actually being different for different wavelengths of light.
In optics, an achromatic converging lens is produced by matching a glass converging lens with a flint diverging lens. If the lenses are matched for chromatic distortion (the flint cancels out the chromatic distortion of the glass), the overall produced lens is still converging (glass has a more consistent overall refractive index than flint).
Thus, you get the classic achromatic doublet.
That is all that is going on with the two prisms (oil and water): their chromatic distortion properties cancel while allowing for an overall bending of the light.
You could do it with any two refractive media - as long as a balance can be achieved where the two prism materials cancel out the chromatic dispersion while giving an overall converging effect.
Thus if you could get the correct formulae and find appropriate materials from amongst the liquid plastics, transparent epoxies, glass etc. you would be able to make your prisms without TOO much trouble (people are able to grind their own reflectors for telescopes, which are FAR more difficult to do acurately than plane surfaces...)
Bill.
Thanks for the response, makes sense.
The transmission of the light would probably be lower too through a plastic. However, maybe not too much.
So the trick is getting the correct data to apply to a prism of different refractive indexes.
I still don't understand why 2 glass prisms would be all that expensive. I just can't figure out the sizes and angles for them.
I was hoping someone would have documented the details much like the Oil/Water version.
I'm still a little uncomfortable with liquid being so close to the projector.
The transmission of the light would probably be lower too through a plastic. However, maybe not too much.
So the trick is getting the correct data to apply to a prism of different refractive indexes.
I still don't understand why 2 glass prisms would be all that expensive. I just can't figure out the sizes and angles for them.
I was hoping someone would have documented the details much like the Oil/Water version.
I'm still a little uncomfortable with liquid being so close to the projector.
Generally, prisms are made to very accurate tolerances for optical instruments. Anything specialised is very expensive.
If you wanted to make them yourself, or have blanks made to rough spec and finish them yourself, the price and quality would not be anywhere near the commercial ones, but that is not necessary for projectors.
Literally, with the correct materials, they would not be TOO difficult or expensive to make (or have made...)
Bill.
If you wanted to make them yourself, or have blanks made to rough spec and finish them yourself, the price and quality would not be anywhere near the commercial ones, but that is not necessary for projectors.
Literally, with the correct materials, they would not be TOO difficult or expensive to make (or have made...)
Bill.
Anamorphic squeeze
ap0the0sis,
The anamorphic lens does indeed squeeze the image. The reason they're used by owners of 4:3 projectors is that they allow all of the pixels in your projector to be used in generating the image.
The trick to avoid distortion in your squeezed image is to pre-apply a distortion in the opposite direction. There are two means generally employed to do this. One way is to use an external scaler or PC to re-scale a 16:9 image to fill your whole 4:3 panel.
If you viewed this image without an anamorphic lens, it would show people tall and skinny and all things stretched vertically. Now placing an anamorphic lens in front of your projector causes the image to be squeezed back to 'normal' geometry. The big advantage is you are now using many more pixels to create the picture giving you a better resolution.
The second way of doing this is using a DVD player that allows aspect ratio settings. If you tell the player the aspect ratio is 16:9 and tell the projector it is 4:3 then the picture takes on that tall and skinny people look.
Hope that helps.
Regards,
Glenn
ap0the0sis,
The anamorphic lens does indeed squeeze the image. The reason they're used by owners of 4:3 projectors is that they allow all of the pixels in your projector to be used in generating the image.
The trick to avoid distortion in your squeezed image is to pre-apply a distortion in the opposite direction. There are two means generally employed to do this. One way is to use an external scaler or PC to re-scale a 16:9 image to fill your whole 4:3 panel.
If you viewed this image without an anamorphic lens, it would show people tall and skinny and all things stretched vertically. Now placing an anamorphic lens in front of your projector causes the image to be squeezed back to 'normal' geometry. The big advantage is you are now using many more pixels to create the picture giving you a better resolution.
The second way of doing this is using a DVD player that allows aspect ratio settings. If you tell the player the aspect ratio is 16:9 and tell the projector it is 4:3 then the picture takes on that tall and skinny people look.
Hope that helps.
Regards,
Glenn
ahh, i see. make some sense to me now. i dont think this lens setup would work well for someone that is switching between tv viewing (4:3) and movie (16:9) right? This is more like one time setup and leave it for movies
got another question. how come these lenses are filled with fluid? Wouldnt it be better to use a solid piece of plexiglass and grind the prizm shapes from that? This way you can get the right curves to compensate for distortion?
justa thought
ap0the0sis
got another question. how come these lenses are filled with fluid? Wouldnt it be better to use a solid piece of plexiglass and grind the prizm shapes from that? This way you can get the right curves to compensate for distortion?
justa thought
ap0the0sis
The long and short of it is that each method of expansion/compression has it's good points and it's bad points.
My pref is solid glass prisms, the company Prismasonic uses 2 acrylic prisms for their anamorphic lens and it's a nice design.
I don't like the idea of having liquid filled prisms getting hot and expanding next to my projector.
I am trying to figure a cost effective way of creating an anmorphic prism with either curved mirrors or 2 (30,60,90) prisms.
I haven't been able to find someone to tell me exactly how they have done it, so it's an experiment that is moving slowly.
However, panavision and other big movie lens makers have used prisms for a long time. And it's very common to expand an elliptical laser so that it is circular. But noone is able to tell me if the angles of the prisms need to be changed for light in the visible wavelengths!!
I even found a guy that has made his own prisms so I'm going to try that route also.
We'll see.
My pref is solid glass prisms, the company Prismasonic uses 2 acrylic prisms for their anamorphic lens and it's a nice design.
I don't like the idea of having liquid filled prisms getting hot and expanding next to my projector.
I am trying to figure a cost effective way of creating an anmorphic prism with either curved mirrors or 2 (30,60,90) prisms.
I haven't been able to find someone to tell me exactly how they have done it, so it's an experiment that is moving slowly.
However, panavision and other big movie lens makers have used prisms for a long time. And it's very common to expand an elliptical laser so that it is circular. But noone is able to tell me if the angles of the prisms need to be changed for light in the visible wavelengths!!
I even found a guy that has made his own prisms so I'm going to try that route also.
We'll see.
Hi ap0the0sis,
New ones or video projection can cost $$$.
Ebay usually carries used 16mm film ones for between $30 and $70, but their diameter is limited, and they would need additional optical components to get them to work with the large panel projectors most people here are using.
it COULD be done, though, with a little ingenuity.
Bill.
New ones or video projection can cost $$$.
Ebay usually carries used 16mm film ones for between $30 and $70, but their diameter is limited, and they would need additional optical components to get them to work with the large panel projectors most people here are using.
it COULD be done, though, with a little ingenuity.
Bill.
Using aluminum foil on water prism
I read an interesting technic for making water prisms. The long and short of it is that this lady used aluminum foil on each edge and then used silicone. She then used solder to close the joint. She was making the prisms to create rainbows in her home. However she had never been able to make one that didn't leak. Until now.
On Another related subject I have been trying to get some 30 60 90 prisms and I found 2. Small but enough to test if they would work well to expand the image. And the answer is yes. They cost approx $8.00 each but they are too small and don't let enough light through. So I asked for a quote on 100mm ones and it's very expensive $850 for 2.
My latest attempt at getting these prisms is an optical surplus store on the web.
If I could use 45 45 90 prisms I would be done, so many of those around. But it doesn't work with 45 45 90.
I'm sticking with the solid prism method and hope I can find an inexpensive channel for purchasing them.
I read an interesting technic for making water prisms. The long and short of it is that this lady used aluminum foil on each edge and then used silicone. She then used solder to close the joint. She was making the prisms to create rainbows in her home. However she had never been able to make one that didn't leak. Until now.
On Another related subject I have been trying to get some 30 60 90 prisms and I found 2. Small but enough to test if they would work well to expand the image. And the answer is yes. They cost approx $8.00 each but they are too small and don't let enough light through. So I asked for a quote on 100mm ones and it's very expensive $850 for 2.
My latest attempt at getting these prisms is an optical surplus store on the web.
If I could use 45 45 90 prisms I would be done, so many of those around. But it doesn't work with 45 45 90.
I'm sticking with the solid prism method and hope I can find an inexpensive channel for purchasing them.
Please continue!!!
No, please don't let this discussion die!
I'm a complete DIY newbie so please bear with me. I have a few questions that have gone unresolved in this thread so far.
Has anyone tried using mineral oil? How does it compare to turpentine?
rwhitley, how did the PVC plastic tubing work for you? Can you please post some pictures?
Has anyone else built a working lens?
Tor, are you using your lens? I checked your updated home theater on your web site and I didn't see it in front of your projector.
Please keep talking everyone, I'm learning a ton!!
Tony
No, please don't let this discussion die!
I'm a complete DIY newbie so please bear with me. I have a few questions that have gone unresolved in this thread so far.
Has anyone tried using mineral oil? How does it compare to turpentine?
rwhitley, how did the PVC plastic tubing work for you? Can you please post some pictures?
Has anyone else built a working lens?
Tor, are you using your lens? I checked your updated home theater on your web site and I didn't see it in front of your projector.
Please keep talking everyone, I'm learning a ton!!
Tony
Is anything happening here? What I am looking for is the info to do a 2.35 lens.
Has everyone else just finished their 16:9 lens and been happy enough to just go away satisfied or are you all too busy to experiment further?
I bought the ViSR 2.35 lens but it would only contract and I need to do an expand version. I downloaded the DECinema excel spreadsheet but can't make sense out of it. Does anyone have an english translated version? I tried sending him a PM but got no reply.
TIA,
Phil
Has everyone else just finished their 16:9 lens and been happy enough to just go away satisfied or are you all too busy to experiment further?
I bought the ViSR 2.35 lens but it would only contract and I need to do an expand version. I downloaded the DECinema excel spreadsheet but can't make sense out of it. Does anyone have an english translated version? I tried sending him a PM but got no reply.
TIA,
Phil
Most, if not all, anamorphic lenses use achromatic prisms set at an angle that compresses the image vertically.
If you wanted to expand the image as well, you could go either for a shorter focal length (wider angle) objective lens, or try using a combination of cylindrical lenses instead of prisms.
Good cylindrical lenses are hard to find, though...
Bill.
If you wanted to expand the image as well, you could go either for a shorter focal length (wider angle) objective lens, or try using a combination of cylindrical lenses instead of prisms.
Good cylindrical lenses are hard to find, though...
Bill.
Bill,
You can turn a prism lens into an expander by reversing it and rotating it 90 degrees. Some statements I read claim that the lens actually works better that way. I need an expander so that's how I will mount mine. The main thing I don't know is what are the correct angles for the 2.35 version.
Also, although I have the turpentine prism at 24 degrees, and the water at 30 degrees, I don't know the relationship between the two. The info on Arne's site seems ambiguous since his drawing doesn't seem to agree with the values he has, (-3.2 degrees, 31 degrees). It would be nice if I could get some clarity on these numbers.
TIA,
Phil
You can turn a prism lens into an expander by reversing it and rotating it 90 degrees. Some statements I read claim that the lens actually works better that way. I need an expander so that's how I will mount mine. The main thing I don't know is what are the correct angles for the 2.35 version.
Also, although I have the turpentine prism at 24 degrees, and the water at 30 degrees, I don't know the relationship between the two. The info on Arne's site seems ambiguous since his drawing doesn't seem to agree with the values he has, (-3.2 degrees, 31 degrees). It would be nice if I could get some clarity on these numbers.
TIA,
Phil
I would love for this thread to continue. I have tried making my own but to no success. Both prisms leaked. I could not find a good way to accurately cut both glass and plexiglass. Hopefully Tor will post his plans on how he did it
I'd like to see one based on mirrors like the Prismasonic and see those results of a DIY posted here. I'm off to do a DIY subwoofer and hopefully have that one not leak like my prisms did.
I'd like to see one based on mirrors like the Prismasonic and see those results of a DIY posted here. I'm off to do a DIY subwoofer and hopefully have that one not leak like my prisms did.
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