Ok...This solution, NASA Polarization Recycling Technique, seems TOO GOOD not to build into our DIY projectors....
I know many of us have read the article, and many of us have talked about building it, but I haven't so far seen anybody actually do it.
So this thread is for specifically this technique.... Any ideas, comments, results, problems, parts pricing etc...
My first comment is that it seems the 1st design in the linked article would be the one for us since the 2nd design seems to rely on a fluorescent backlight.
But it seems at first that the 1st design would need a smaller sized LCD panel than the 15"chers. For many reasons:
- Large sized polarizing beam splitter and half-wave retarders more expensive?
- Would need single fresnel instead of double so maybe would be too difficult to make parabolic reflector big enough to cover 15"cher fresnel, or maybe will lose too much light at larger sized DIY parabolic reflector, or certainly large sized parabolic reflector and large sized beam splitter mirror and regular mirror and half-wave retarder would be difficult to fit into OHP
That's pretty much all I can think of...
As for the large sized parabolic reflector, that would actually be easy to make.
And as for fitting the stuff into an OHP, well, might have to get rid of the OHP box and build a custom box (not a big deal, just some wood and screws).
So as for the benefits of building this design, what I can see is:
- Actually use the 50%+ of the light that is being lost as heat without this design.
- Get rid of the heat generated by the unused light.
Also there would be some loss of light from all the reflecting but this should be far outweighed by the benefits.
Please comment.
I will start looking at polarizing beam splitter and half-wave retarder prices, but other people interested please do the same....
Also i think there is a link for a more technical brief on the page.
I know many of us have read the article, and many of us have talked about building it, but I haven't so far seen anybody actually do it.
So this thread is for specifically this technique.... Any ideas, comments, results, problems, parts pricing etc...
An externally hosted image should be here but it was not working when we last tested it.
My first comment is that it seems the 1st design in the linked article would be the one for us since the 2nd design seems to rely on a fluorescent backlight.
An externally hosted image should be here but it was not working when we last tested it.
But it seems at first that the 1st design would need a smaller sized LCD panel than the 15"chers. For many reasons:
- Large sized polarizing beam splitter and half-wave retarders more expensive?
- Would need single fresnel instead of double so maybe would be too difficult to make parabolic reflector big enough to cover 15"cher fresnel, or maybe will lose too much light at larger sized DIY parabolic reflector, or certainly large sized parabolic reflector and large sized beam splitter mirror and regular mirror and half-wave retarder would be difficult to fit into OHP
That's pretty much all I can think of...
As for the large sized parabolic reflector, that would actually be easy to make.
And as for fitting the stuff into an OHP, well, might have to get rid of the OHP box and build a custom box (not a big deal, just some wood and screws).
So as for the benefits of building this design, what I can see is:
- Actually use the 50%+ of the light that is being lost as heat without this design.
- Get rid of the heat generated by the unused light.
Also there would be some loss of light from all the reflecting but this should be far outweighed by the benefits.
Please comment.
I will start looking at polarizing beam splitter and half-wave retarder prices, but other people interested please do the same....
Also i think there is a link for a more technical brief on the page.
OOps, I guess the technical brief is only available for free to U.S. residents....
Any volunteers?
Any volunteers?
Ok, I came up with a few designs that may eliminate the need for a polarizing beam splitter. Some of them may be able to fit in an standard OHP case.
They basically mix the 2 different schemes pictured above.
I did very little costing for the components seen in the NASA pictures. Basically i sent emails to a couple of places and attached the 1st pic above with some dimensions and asked them if they carry the parts I need and how much it would cost. But as it is sunday, will have to wait.
From looking at edmondoptics it seems that we may be able to expect that the polarizing beam splitter in the size needed may be very expensive.
However the half-wave retarder may be fairly cheap and i'm not sure on the price for reflecting polarizer.
Also, I'm not sure if for the reflecting polarizer to work, the light has to hit it perpendicularly or if it's ok for light to hit the reflecting polarizer at different angles. Depending on the answer to this, 2 of the designs below may not work.
They basically mix the 2 different schemes pictured above.
I did very little costing for the components seen in the NASA pictures. Basically i sent emails to a couple of places and attached the 1st pic above with some dimensions and asked them if they carry the parts I need and how much it would cost. But as it is sunday, will have to wait.
From looking at edmondoptics it seems that we may be able to expect that the polarizing beam splitter in the size needed may be very expensive.
However the half-wave retarder may be fairly cheap and i'm not sure on the price for reflecting polarizer.
Also, I'm not sure if for the reflecting polarizer to work, the light has to hit it perpendicularly or if it's ok for light to hit the reflecting polarizer at different angles. Depending on the answer to this, 2 of the designs below may not work.
Attachments
Hmmmm. this sounds familiar!
Property:
Gee...where have I seen this before?????
Seems your buddy Proto has "been there, done that"
http://www.diyaudio.com/forums/showthread.php?postid=166462#post166462
This is a GOOD IDEA...., and I have the materials to do a "theory test" at least. The mirror and 1/4 wave retarder cannot be at an angle though....and I'm not sure yet if the fresnel will mess things up. But ANY IDEAS on "light recycling" need to be explored. Getting only 10% of my 49,000 lumens to the screen really SUCKS.
Who would've ever thought.....A Proto/Property collaboration?
🤐 
Property:
Gee...where have I seen this before?????
Seems your buddy Proto has "been there, done that"
http://www.diyaudio.com/forums/showthread.php?postid=166462#post166462
This is a GOOD IDEA...., and I have the materials to do a "theory test" at least. The mirror and 1/4 wave retarder cannot be at an angle though....and I'm not sure yet if the fresnel will mess things up. But ANY IDEAS on "light recycling" need to be explored. Getting only 10% of my 49,000 lumens to the screen really SUCKS.
Who would've ever thought.....A Proto/Property collaboration?
🤐 PROTO5 i'm glad you read this thread...YUP this thread is thanks to your efforts....However I don't think your preliminary design that you posted in the other thread is the right one....The one you designed is based on a fluorescent backlight tube as seen on the nasa site i think....
You are right about the fresnel...bouncing the light back and forth through the fresnel will not do what we want because of the spherical aberration introduced on one of the sides of the fresnel (see the fresneltech.com pdf---i'll post the link later). This was pointed out to me in a fruitful discussion with CHBRIGHT.
The good news is that there is an easy fix for that.
I will post schematics of the new and improved designs that came thanks to help from chbright later tonight.
Proto5 based on this I think what we need is the 1/2 wave retarder instead of the 1/4 wave retarder....I will post more tonight.
You are right about the fresnel...bouncing the light back and forth through the fresnel will not do what we want because of the spherical aberration introduced on one of the sides of the fresnel (see the fresneltech.com pdf---i'll post the link later). This was pointed out to me in a fruitful discussion with CHBRIGHT.
The good news is that there is an easy fix for that.
I will post schematics of the new and improved designs that came thanks to help from chbright later tonight.
Proto5 based on this I think what we need is the 1/2 wave retarder instead of the 1/4 wave retarder....I will post more tonight.
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