ORWO spectral plates
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JohnFP
ORWO spectral plates
I'd love to try some. The reason I don't do DCG as much is the whole gelatin fabrication process. With this, strip, store and sensitize as needed. Or strore then strip and sensitize as needed. If you are serious, drop me an e-mail (in my profile) and I will send you my address.
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Ed Wesly
ORWO spectral plates
Etched into my memory is the basic grating formula:
n * lambda = d * sin theta,
n = order number, lambda = wavelength, d = fringe spacing, theta the intra-beam angle.
For the material in question, with 125 line pairs per millimeter resolution, recording at He-Ne red of 633 nm, the question that needs to be answered seems to be “what is the intra-beam angle that is at the limits of this film’s resolution?”
Since we are solving for theta, the equation needs to be rearranged to:
sin theta = (n * lambda)/d (We will set n = 1, more on that below. Plus the line pairs per mm, which is a spatial frequency, needs to be changed to a measure of fringe spacing, the distance from one bright (or dim) fringe to the next; if there are 125 lp/mm, then the distance between each fringe is 1/125 mm = .008 mm = 8 microns = 8000 nm so that all units are the same.)
plugging in:
sin theta = 633/8000 = .079125. The last digit tells us that the sin of theta = .079125, so I enter .079125 into the calculator and hit inverse sin to get the angle that .079…is the sine of, which = 4.538272491, or 4.5 degrees. Pretty shallow angle! Might not be able to get two spatial filters that close together in a short distance!
The n number in this equation is the order number; with these low frequency gratings when a laser beam encounters them, there are more than one beam in the diffraction pattern. If an undiverged beam is incident on a grating made with a spatial frequency of 125 lp/mm, then another beam comes out at 4.5 degrees separate from the replay beam.
A second beam will also appear, its angle will be given by replacing the n with the value of 2, so we solve sin theta = 2 * (633/8000) = .15825, inverse sine of the latter = 9.105334539 degrees.
Third order beam: sin theta = 3 * (633/8000) = .237375, inverse sine of the latter = 13.73166236 degrees.
Keep plugging in order numbers until the sine is greater than or equal to unity. Now I can’t stop myself!
4th order, 18.45 degrees; 5th order, 23.30495941 degrees; 6th order, 28.3430738 degrees; 7th order, 33.63326249; 8th order, 39.27180555, 9th order, 45.40807524; 10th order, 52.30247984 degrees, 11th order, 60.5022462 degrees, 12th order, 71.71360336 degrees, and when n = 13, we get 13 * (633/8000) = 1.028625, which has no inverse sine since sines are restricted to numbers including and between 1 and -1.
So there would be 25 beams coming out of a grating with this coarse of a fringe spacing; the straight through or zero order beam, the dozen orders just calculated, plus their twins of the negative first through twelve orders reflection symmetric to the positive orders!
Aren’t you glad you asked? And if you want to know what the intra-beam angle would be if you recorded at 532 nm, well, that exercise, is left to you, the reader, as they always say in the math books!
Footnote: resolutions should technically be given in “line pairs per millimeter”, as the bars in the resolution target are black and white, like bright and dim fringe pairs, and there needs to be a distinct contrast between the two to show that the material resolves the difference.
I have made gratings with Kodak Technical Pan film, I think it was rated at either 200 or 400 lp/mm, and it wasn’t all that efficient. But it did bring up the extra orders as predicted. My suggestion on what to do with this ORWO stuff would be to fix out the silver and use the gelatin for dichromating or diffusing, same with the T-Max.
n * lambda = d * sin theta,
n = order number, lambda = wavelength, d = fringe spacing, theta the intra-beam angle.
For the material in question, with 125 line pairs per millimeter resolution, recording at He-Ne red of 633 nm, the question that needs to be answered seems to be “what is the intra-beam angle that is at the limits of this film’s resolution?”
Since we are solving for theta, the equation needs to be rearranged to:
sin theta = (n * lambda)/d (We will set n = 1, more on that below. Plus the line pairs per mm, which is a spatial frequency, needs to be changed to a measure of fringe spacing, the distance from one bright (or dim) fringe to the next; if there are 125 lp/mm, then the distance between each fringe is 1/125 mm = .008 mm = 8 microns = 8000 nm so that all units are the same.)
plugging in:
sin theta = 633/8000 = .079125. The last digit tells us that the sin of theta = .079125, so I enter .079125 into the calculator and hit inverse sin to get the angle that .079…is the sine of, which = 4.538272491, or 4.5 degrees. Pretty shallow angle! Might not be able to get two spatial filters that close together in a short distance!
The n number in this equation is the order number; with these low frequency gratings when a laser beam encounters them, there are more than one beam in the diffraction pattern. If an undiverged beam is incident on a grating made with a spatial frequency of 125 lp/mm, then another beam comes out at 4.5 degrees separate from the replay beam.
A second beam will also appear, its angle will be given by replacing the n with the value of 2, so we solve sin theta = 2 * (633/8000) = .15825, inverse sine of the latter = 9.105334539 degrees.
Third order beam: sin theta = 3 * (633/8000) = .237375, inverse sine of the latter = 13.73166236 degrees.
Keep plugging in order numbers until the sine is greater than or equal to unity. Now I can’t stop myself!
4th order, 18.45 degrees; 5th order, 23.30495941 degrees; 6th order, 28.3430738 degrees; 7th order, 33.63326249; 8th order, 39.27180555, 9th order, 45.40807524; 10th order, 52.30247984 degrees, 11th order, 60.5022462 degrees, 12th order, 71.71360336 degrees, and when n = 13, we get 13 * (633/8000) = 1.028625, which has no inverse sine since sines are restricted to numbers including and between 1 and -1.
So there would be 25 beams coming out of a grating with this coarse of a fringe spacing; the straight through or zero order beam, the dozen orders just calculated, plus their twins of the negative first through twelve orders reflection symmetric to the positive orders!
Aren’t you glad you asked? And if you want to know what the intra-beam angle would be if you recorded at 532 nm, well, that exercise, is left to you, the reader, as they always say in the math books!
Footnote: resolutions should technically be given in “line pairs per millimeter”, as the bars in the resolution target are black and white, like bright and dim fringe pairs, and there needs to be a distinct contrast between the two to show that the material resolves the difference.
I have made gratings with Kodak Technical Pan film, I think it was rated at either 200 or 400 lp/mm, and it wasn’t all that efficient. But it did bring up the extra orders as predicted. My suggestion on what to do with this ORWO stuff would be to fix out the silver and use the gelatin for dichromating or diffusing, same with the T-Max.
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holo_cyware
ORWO spectral plates
Nice intelectual exercise Ed, you really know your stuff.
But, the gelatin layer on these plates seems to be quite thick: a broken plate would stay togeter due to the gelatin that holds the glass pieces. Also, the gelatin seems to be very hard, like a plastic foil. In fact, it gives the impression that a thin plastic foil was laminated onto a side of the glass plate. I didn't measure the thickness of the gelatin yet, but it definately seems to be thick, maybe as muck as 50-100 microns.
Will it work for holography? (DCG/silver). Is there a "superior" limit for the gelatin thickness for a hologram to work?
But, the gelatin layer on these plates seems to be quite thick: a broken plate would stay togeter due to the gelatin that holds the glass pieces. Also, the gelatin seems to be very hard, like a plastic foil. In fact, it gives the impression that a thin plastic foil was laminated onto a side of the glass plate. I didn't measure the thickness of the gelatin yet, but it definately seems to be thick, maybe as muck as 50-100 microns.
Will it work for holography? (DCG/silver). Is there a "superior" limit for the gelatin thickness for a hologram to work?
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JohnFP
ORWO spectral plates
Ed, I just love you man....
Thanks for your time on that.
WOW, that is kinda thick. It would be nice if you could verify that, if not I will try to when I receive some plates. If you broke a plate could a piece be peal off to use micrometers on?
Thanks for your time on that.
WOW, that is kinda thick. It would be nice if you could verify that, if not I will try to when I receive some plates. If you broke a plate could a piece be peal off to use micrometers on?
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Ed Wesly
ORWO spectral plates
Thicker might be better for some uses, although it will shrink somewhat when the silver is removed. Sounds kind of hard, but what the heck give it a try, based on the suggestions in a similar thread in Gen Holo.
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holo_cyware
ORWO spectral plates
I started to test the ORWO plates for DCG.
In theory, for the DCG to work properly a hard gelatin is recomended (type B, cattle, high bloom).
ORWO is AGFA and I guess that the companies tend to use and go on with the same gelatin for years, in order to ensure a continuity in the quality. I may be derailing here, but I highly suspect they may use the same gelatin for all the films/plates/whatever. Someone please corect this if I'm not right!
Now, we all know that AGFA used very hard gelatin (quote from holowiki/gelatin section):
"AGFA 8E75HD plates had a swelling factor of 25. (Very hard)
Kodak 649F plates had a swelling factor of 200.
According to the authors of the article, this was why the Kodak plates were so much better for adaptation to DCG"
So a too-hard gelatin won't work properly for DCG.
This is what I'm apparently getting. Basically I can get the plates "milky" playing with the hardening step (after the dark reaction), but if the gelatin get's fully cross linked it becomes so hard that it would play mostly in deep red with some green specks and in would appear after a long drying (in the last alcohol bath there is no red interference visible).
If I understand correcty, this is how the DCG works from the gelatin thickness point of view:
1. Plate ready to shot - must be fully dried [gelatin layer as thin as possible]
2. Plate is exposed - [no change in the thickness]
3. Plate is fixed - [no change, maybe slightly "gonflated"]
4. Plate is washed in the water, different water temperatures vs time controlling the amount of thickening [the gelatin layer gets much thicker, if too thick it becomes milky on drying]
5. Alcohol baths - these would remove the water from the gelatin "interstices" [thickness is preserved to the optimum level after the alcohol evaporation, just under getting milky]
So basically a process of inflating the gelatine in a controlled manner in order to play the hologram optimaly. Just like making aerogel, by getting the water out of the silica gel with carbon dioxide, so the structure won't collapse, leaving a very porous structure.
A very hard gelatin would leave very little room for playing with it's thickness, maybe as low as it won't play properly. A too soft may not even hold up the differents baths.
So, saying this gelatin is on the hard side, what would you recomend me (besides "get a softer gelatin", because that's the point of getting these already coated plates)?
In theory, for the DCG to work properly a hard gelatin is recomended (type B, cattle, high bloom).
ORWO is AGFA and I guess that the companies tend to use and go on with the same gelatin for years, in order to ensure a continuity in the quality. I may be derailing here, but I highly suspect they may use the same gelatin for all the films/plates/whatever. Someone please corect this if I'm not right!
Now, we all know that AGFA used very hard gelatin (quote from holowiki/gelatin section):
"AGFA 8E75HD plates had a swelling factor of 25. (Very hard)
Kodak 649F plates had a swelling factor of 200.
According to the authors of the article, this was why the Kodak plates were so much better for adaptation to DCG"
So a too-hard gelatin won't work properly for DCG.
This is what I'm apparently getting. Basically I can get the plates "milky" playing with the hardening step (after the dark reaction), but if the gelatin get's fully cross linked it becomes so hard that it would play mostly in deep red with some green specks and in would appear after a long drying (in the last alcohol bath there is no red interference visible).
If I understand correcty, this is how the DCG works from the gelatin thickness point of view:
1. Plate ready to shot - must be fully dried [gelatin layer as thin as possible]
2. Plate is exposed - [no change in the thickness]
3. Plate is fixed - [no change, maybe slightly "gonflated"]
4. Plate is washed in the water, different water temperatures vs time controlling the amount of thickening [the gelatin layer gets much thicker, if too thick it becomes milky on drying]
5. Alcohol baths - these would remove the water from the gelatin "interstices" [thickness is preserved to the optimum level after the alcohol evaporation, just under getting milky]
So basically a process of inflating the gelatine in a controlled manner in order to play the hologram optimaly. Just like making aerogel, by getting the water out of the silica gel with carbon dioxide, so the structure won't collapse, leaving a very porous structure.
A very hard gelatin would leave very little room for playing with it's thickness, maybe as low as it won't play properly. A too soft may not even hold up the differents baths.
So, saying this gelatin is on the hard side, what would you recomend me (besides "get a softer gelatin", because that's the point of getting these already coated plates)?
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JohnFP
ORWO spectral plates
Gosh, if you're getting red with a green or blue laser then the gel is full swollen and it sounds like it is a soft gelatin, IMHO.
I partially agree with Danny.
It kinda depends what you want.
If you want a gold hologram, then higher fixer, water and alcohol temps but short times in the alcohols (15 seconds).
If you want a white hologram, flip the emulsion toward the reference beam and process as above.
If you want a green or blue narrow band hologram. Fix longer, use cool temperatures in all baths and soak longer in alcohols (2 minutes each). Also, add more alcohol concentrations. In other words use more baths with more gradual inceases in concentration like 35, 70, 91, 100.
What is it your are trying to achive? Color, brightness, broadband, narrowband???
I partially agree with Danny.
It kinda depends what you want.
If you want a gold hologram, then higher fixer, water and alcohol temps but short times in the alcohols (15 seconds).
If you want a white hologram, flip the emulsion toward the reference beam and process as above.
If you want a green or blue narrow band hologram. Fix longer, use cool temperatures in all baths and soak longer in alcohols (2 minutes each). Also, add more alcohol concentrations. In other words use more baths with more gradual inceases in concentration like 35, 70, 91, 100.
What is it your are trying to achive? Color, brightness, broadband, narrowband???
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holo_cyware
ORWO spectral plates
Wow, never thought there are so many things to play with. And the toybox is not nearly open yet!
This is the best I got with these ORWO plates. I leave the rest for the master
Question: are the lines visible on the hologram "sliced bread lines", thus my laser was hiccuping during the exposure (4 mins)?
This is the best I got with these ORWO plates. I leave the rest for the master
Question: are the lines visible on the hologram "sliced bread lines", thus my laser was hiccuping during the exposure (4 mins)?
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JohnFP
ORWO spectral plates
It looks more like the polarization and brewsters were not controlled. Is that light reflection from the camera or the illuminating light source?
Excellent hologram, simply grand for your first few steps. You're doing great!!! :dance:
Also, put a black background behind it. And if the reflection is from the camera, shoot off perpendicular and adjust light so you get no light reflection.
Excellent hologram, simply grand for your first few steps. You're doing great!!! :dance:
Also, put a black background behind it. And if the reflection is from the camera, shoot off perpendicular and adjust light so you get no light reflection.