what about transmissions hologram? because the fringes are recorded on surface of the hologram and not the depth so in that aplication it would apply that you could increase the amout of AD to 4g?a_k wrote:Danny, i can't report own experiences, because i only have made denisyuks with the violet LD so far. What i found was, that even with 0.5% AmDi, when the coating is a bit thicker it already gets difficult to have good results, as the plate appears very dark in 405nm light. I would assume that for single beam reflection and coating thicknesses around 5-6um 1% would be a resonable upper limit.
If you want to use a setup in which beams hit the plates from both sides i would think that above 2% AmDi the transparency of the coating would not be sufficient to get a high DE. Even when the beams come from different sides of the plate they need to meet within the coating. If the plates don't have sufficient transparency, you would get a central plane at half of the coating thickness with the best beam ratio which would quickly get worse in both directions. I think 4% would be too much unless you were using very thin coatings.
Besides that with a higher AmDi content one would expect a larger amount of blueshift. This fear was my main reason for using only 0.5% AmDi.
With 16mW spread to fully illuminate a 8x10 plate you are already getting a sensitivity of 1.16mJ/cm2 if there are no losses at all. 8 times less would mean 144uJ/cm2, which would be great of course
Colin, thanks, i'll go through Phils postings then.
405nm DCG
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Danny Bee
405nm DCG
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JohnFP
405nm DCG
Danny, even with transmisisons, if your film is thicker then about 1/2 micron, then there will be fringe formation in the depth of the emulsion. But because you dont have to worry about losing object beam lighting trying to go through the plate, you could increase the concentration of the AmDi. Same holds true for split beam reflections and spill over lighting.
But I must say, of all the DCG SBR holograms I have made I have never used .5% AmDi, even with using 457nm.
But I must say, of all the DCG SBR holograms I have made I have never used .5% AmDi, even with using 457nm.
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Colin Kaminski
405nm DCG
John, I am a little behind on this conversation. Do you use more or less?JohnFP wrote:Danny, even with transmisisons, if your film is thicker then about 1/2 micron, then there will be fringe formation in the depth of the emulsion. But because you dont have to worry about losing object beam lighting trying to go through the plate, you could increase the concentration of the AmDi. Same holds true for split beam reflections and spill over lighting.
But I must say, of all the DCG SBR holograms I have made I have never used .5% AmDi, even with using 457nm.
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a_k
405nm DCG
Just saw this ECDL kit on ebay, including a single mode 0.5W LD (low reflection coated) and a grating for $44.95:
http://cgi.ebay.com/ECDL-Kit-Extended-C ... 240%3A1318
Unfortunately the wavelengths offered are 790nm and 1000nm, the gratings have 1400 / 1630 lines/mm.
Sergio, Did you mean that a less strict temp control could still be useful for an ECDL system?
http://cgi.ebay.com/ECDL-Kit-Extended-C ... 240%3A1318
Unfortunately the wavelengths offered are 790nm and 1000nm, the gratings have 1400 / 1630 lines/mm.
Sergio, Did you mean that a less strict temp control could still be useful for an ECDL system?
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Danny Bee
405nm DCG
Hi Colins ....Colin Kaminski wrote:John, I am a little behind on this conversation. Do you use more or less?JohnFP wrote:Danny, even with transmisisons, if your film is thicker then about 1/2 micron, then there will be fringe formation in the depth of the emulsion. But because you dont have to worry about losing object beam lighting trying to go through the plate, you could increase the concentration of the AmDi. Same holds true for split beam reflections and spill over lighting.
But I must say, of all the DCG SBR holograms I have made I have never used .5% AmDi, even with using 457nm.
The normal rate for 532nm is about 4 or higher if the chrome dosnt crystalis. Because the yellow layer of the AD lets the light through very nicely. but as you go down to 457nm the amout for leting the light through is about 1 to 2 g
as you hit 405nm the AD real soaks up the light and any where from .25 to 1 seem to be the right mix.
The thickness of the layer plays into this too..but now that Im play around with this 405nm Im wondering how thick does it need to be to do a good trans at 405nm, because if the layer is thinner you could still add more AD and still get the light thro to make a good grading or a trans holo.... I did do my first Trans Holo in dcg 10/11/08.. and the replay is nice and bright at a mix of .5/12/100 2min exposer but if i can increace the level of AD i could decreace the time of the exposer
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JohnFP
405nm DCG
Colin, Danny answered your question.
Danny, with a transmissons you can go down to just a couple microns in thickness and as long as you have a nice object to ref. ratio and you will get great transmission holograms. Take the object light UP to it just gets noisy, then back off the object light amount just a bit for clean.
Danny, with a transmissons you can go down to just a couple microns in thickness and as long as you have a nice object to ref. ratio and you will get great transmission holograms. Take the object light UP to it just gets noisy, then back off the object light amount just a bit for clean.
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holos
405nm DCG
For a_k at 24 Okt 2008
Very important question for very important parameter – what the temperature of developing DCG plate was in your experiment? The temperature – is one of the main parameter for developing GCG. By change temperature of developing you can very fine change the color of image (and the brightness of image too). And you must flatten the illumination of object and photoplate by laser beam. On your photo of hologram the center of image have green color and rest area have red color. If you made flatten beam and exact calculate the time of exposition and the time of developing and the temperature of developing, you can obtain need result – green or orange or red color of all image. But if you use small exposition and big temperature of developing (very, very fine process), you can get broadband (mother-of-pearl) color of image. For this effect volume of image must be small or else, the sharpen of deep part of image can be bad.
Very important question for very important parameter – what the temperature of developing DCG plate was in your experiment? The temperature – is one of the main parameter for developing GCG. By change temperature of developing you can very fine change the color of image (and the brightness of image too). And you must flatten the illumination of object and photoplate by laser beam. On your photo of hologram the center of image have green color and rest area have red color. If you made flatten beam and exact calculate the time of exposition and the time of developing and the temperature of developing, you can obtain need result – green or orange or red color of all image. But if you use small exposition and big temperature of developing (very, very fine process), you can get broadband (mother-of-pearl) color of image. For this effect volume of image must be small or else, the sharpen of deep part of image can be bad.
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a_k
405nm DCG
Hello Holos
Sorry for the late reply. Thanks for your observations, remarks and suggestions. The range of temperatures for the water bath was between 21C and over 30°C, depending on the batch of plates, their age and the gelatin used. The picture of the hologram i posted was in no way intended to be perfect or close to it, but as a proof of concept of recording DCGs with a cheap bluray LD. The defects which you criticise are likely to be due to a poor coating or drying of the plates, in addition to cheap plastic optics. I've coated such a large amount of plates for tests and the priority was not in obtaining perfect coatings but getting many plates coated with the least amount of time and testing them by varying the recording and processing parameters. Even so everything was very time consuming and time is my most precious resource.
It's not only the water temperature which has an effect on the replay color and bandwidth, but also the concentrations and temperatures of the alcohol baths, the level of exposure, the amount of dichromate used, thickness of the coating, age of the plates, etc. With DCGs recorded with green, color shifting in both directions and bandwidth control is quite easily attained. Not so here.
When using 405nm to record holograms, a large amount of red shift is needed, which is not very easy to obtain and even harder to get consistently and repeatably. None of the usual methods for color tuning of DCG (using green for recording) seemed to give consistent and satisfactory results with 405nm. Some of the holograms recorded disappeared in the UV and others resulted in any color between blue and red, with blue being frequent and red rare. The attempts of postswelling the holograms were not very successful. I'm grateful to anyone for ideas about how to get a large redshift consistently and in a controlled manner and still getting a reasonably narrow band replay.
Holos, did you extrapolate your experiences made with other recording laser colors or did you in fact record holograms with 405nm and were able to master the parameters to such an extent that the results did live up to your expectations? If so, i'm very interested in learning about your methods.
The DCG plates, even with very little dichromate, are extremely sensitive to 405nm, 2mJ/cm2 is no big deal and one gets very high DE. Unfortunately most bluray LDs do not run SLM and hence have a short coherence length. Additional effort is needed, like using an ECDL configuration and an accurate temperature control to improve the characteristics of the light source.
Besides that the problem of getting a large red shift is a big obstacle.
Ahmet
Sorry for the late reply. Thanks for your observations, remarks and suggestions. The range of temperatures for the water bath was between 21C and over 30°C, depending on the batch of plates, their age and the gelatin used. The picture of the hologram i posted was in no way intended to be perfect or close to it, but as a proof of concept of recording DCGs with a cheap bluray LD. The defects which you criticise are likely to be due to a poor coating or drying of the plates, in addition to cheap plastic optics. I've coated such a large amount of plates for tests and the priority was not in obtaining perfect coatings but getting many plates coated with the least amount of time and testing them by varying the recording and processing parameters. Even so everything was very time consuming and time is my most precious resource.
It's not only the water temperature which has an effect on the replay color and bandwidth, but also the concentrations and temperatures of the alcohol baths, the level of exposure, the amount of dichromate used, thickness of the coating, age of the plates, etc. With DCGs recorded with green, color shifting in both directions and bandwidth control is quite easily attained. Not so here.
When using 405nm to record holograms, a large amount of red shift is needed, which is not very easy to obtain and even harder to get consistently and repeatably. None of the usual methods for color tuning of DCG (using green for recording) seemed to give consistent and satisfactory results with 405nm. Some of the holograms recorded disappeared in the UV and others resulted in any color between blue and red, with blue being frequent and red rare. The attempts of postswelling the holograms were not very successful. I'm grateful to anyone for ideas about how to get a large redshift consistently and in a controlled manner and still getting a reasonably narrow band replay.
Holos, did you extrapolate your experiences made with other recording laser colors or did you in fact record holograms with 405nm and were able to master the parameters to such an extent that the results did live up to your expectations? If so, i'm very interested in learning about your methods.
The DCG plates, even with very little dichromate, are extremely sensitive to 405nm, 2mJ/cm2 is no big deal and one gets very high DE. Unfortunately most bluray LDs do not run SLM and hence have a short coherence length. Additional effort is needed, like using an ECDL configuration and an accurate temperature control to improve the characteristics of the light source.
Besides that the problem of getting a large red shift is a big obstacle.
Ahmet