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 Posted: Mon Nov 17, 2008 5:27 pm Post subject: Whit Colour Holography |
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I have done an experiment for making a white color holography. In this
experiment I put a coin on the back side of the holography film and
exposed He-Ne laser (which is red in color- 632nm) on the film. After
development, I find that the coin is in green color instead of red.
It would be so much appreciated if anybody helps me to find the
reason. |
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Boxman
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| Posted: Mon Nov 17, 2008 7:05 pm Post subject: Re: Whit Colour Holography |
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On Nov 17, 11:27 am, sl.phys...@gmail.com wrote:
[quote]I have done an experiment for making a white color holography. In this
experiment I put a coin on the back side of the holography film and
exposed He-Ne laser (which is red in color- 632nm) on the film. After
development, I find that the coin is in green color instead of red.
It would be so much appreciated if anybody helps me to find the
reason.
[/quote]
It sounds like you have made a reflection hologram. Most likely the
reason you are getting a green image instead of a red image is due to
the shrinkage of the emulsion on your film during the chemical
processing. The shrinkage of the emulsion can be thought of as
modifiying the spacing between Bragg planes which in turn causes a
wavelength shift towards a shorter wavelength when viewing it with a
white light source.
To verify this you could try viewing the hologram illuminated by a red
laser and the image should still be viewable, although it will be at a
different angle than the green image from the white light source.
I don>t know if it can be corrected, but you might try different films
and different processing to see if you can keep the image closer to
red if that is what you need. |
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Fleetie
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| Posted: Tue Nov 18, 2008 1:58 am Post subject: Re: Whit Colour Holography |
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"Boxman" <boxman@voyager.net> wrote
[quote]It sounds like you have made a reflection hologram. Most likely the
reason you are getting a green image instead of a red image is due to
the shrinkage of the emulsion on your film during the chemical
processing. The shrinkage of the emulsion can be thought of as
modifiying the spacing between Bragg planes which in turn causes a
wavelength shift towards a shorter wavelength when viewing it with a
white light source.
To verify this you could try viewing the hologram illuminated by a red
laser and the image should still be viewable, although it will be at a
different angle than the green image from the white light source.
I don>t know if it can be corrected, but you might try different films
and different processing to see if you can keep the image closer to
red if that is what you need.
[/quote]
Yes, it>s caused by shrinkage of the emulsion. When I did reflection
holograms, there was a certain chemical recommended to cause the
emulsion to swell back again. It was 21 years ago when I used the chemical
though, so I forget what it was. It _might_ have involved glycerine.
To the OP:
You should find that if you breathe moist air ("hurrrrrr!") onto the
emulsion side of the film (or plate), then the colour will
TEMPORARILY shift back through yellow (best colour for brightness IMO),
then orange, towards red, as the humidity swells the emulsion.
I also found that the fix solution seemed to cause the shrinkage,
or at least, leaving it in the fix for longer seemed to exacerbate the
problem. Could you try shortening the fix dip a little?
Let us know how you get on. I>ve cross-posted to alt.lasers too.
Martin
--
Manchester, UK http://fleetie.livejournal.com |
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John Sutter
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| Posted: Tue Nov 18, 2008 5:44 am Post subject: Re: Whit Colour Holography |
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sl.physics@gmail.com wrote:
[quote]I have done an experiment for making a white color holography. In this
experiment I put a coin on the back side of the holography film and
exposed He-Ne laser (which is red in color- 632nm) on the film. After
development, I find that the coin is in green color instead of red.
It would be so much appreciated if anybody helps me to find the
reason.
[/quote]
That takes me back. Around 1990 to made a few Denisyuk reflection
holograms in a cave in West Virginia. I should have known better
but didn>t figure the swelling would be that great.
When I got back to the motel to process the plates all went well until
the final rinses when I could clearly see the reconstructed images
while the plates were still submerged. As the plates dried up the
images went from red to gold to green, blue, gone...
Whenever I wanted to show them I needed to soak them I tried a few
things to permanently swell them, but nothing kept.
Should have made transmission masters and then transferred them.
Oh well...
http://www.sutters.com/CaveHolography/index.html |
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