Thanks all. I tried a mirror and as predicted the reflected beam still looks clean.
Steering with a kinematic mount is pretty slow, I'll look into alternative ways.
It was really fast and nice to steer using the x-y on the 40X objective. Very intuitive.
As far as using steering using the spatial filter I will have to see. At this point it
takes quite some time to center the pinhole. Maybe with the Jodon mount it
will be faster.
I am really hoping to see a noticeable difference with the spatial filter. All this
fuss and cost is a bit annoying since I am just fooling around. The holograms I
expect to make will just be demos of concept, not state of the art...
Cheers.
Spatial Filter
Re: Spatial Filter
Leave the pinhole out of the spatial filter until you're done with the set-up. Putting it in last saves you the trouble of keeping it aligned while changing things.
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Alan Sailer
- Posts: 63
- Joined: Thu Sep 12, 2024 5:24 pm
Re: Spatial Filter
Makes sense. The pinhole is by far the most sensitive mechanical adjustment I've ever made.
Cheers.
Cheers.
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Alan Sailer
- Posts: 63
- Joined: Thu Sep 12, 2024 5:24 pm
Re: Spatial Filter
I got the Jodon filter today. It is missing the magnetic pinhole mount. Do I need to
return it or is there an after market replacement/hack.
Cheers.
return it or is there an after market replacement/hack.
Cheers.
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Alan Sailer
- Posts: 63
- Joined: Thu Sep 12, 2024 5:24 pm
Re: Spatial Filter
Thanks.
I'll make an offer.
Cheers.
I'll make an offer.
Cheers.
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Alan Sailer
- Posts: 63
- Joined: Thu Sep 12, 2024 5:24 pm
Re: Spatial Filter
So after a lot of kerfuffle I finally got a Jodon 10um pinhole to go with the spatial filter I bought. It's a clever design,
basically a magnet with two orthogonal flats holding the pinhole. The magnet has a teflon coated side that slides on
another teflon coated washer on the filter. The magnet attracts the shafts of two micrometer heads so that either
turning the micrometers in and out makes the pinhole follow the micrometers.
Getting the filter to work took about three minutes thanks to teh practice I got from my homebrew filter. It's a lot
more stable and much to my surprise I can still move the laser and move the cleaned up beam to a limited extent.
The final beam has a very clean look. The first reflection hologram I tried looked much nicer than I expected. I'm
guessing the diffraction artifacts from the unfiltered beam make the resulting hologram more noisy and thus less
crisp looking.
Anyhow, thanks for all the advice. After this exercise I can see why spatial filters are a needed part of fine holography.
Cheers.
basically a magnet with two orthogonal flats holding the pinhole. The magnet has a teflon coated side that slides on
another teflon coated washer on the filter. The magnet attracts the shafts of two micrometer heads so that either
turning the micrometers in and out makes the pinhole follow the micrometers.
Getting the filter to work took about three minutes thanks to teh practice I got from my homebrew filter. It's a lot
more stable and much to my surprise I can still move the laser and move the cleaned up beam to a limited extent.
The final beam has a very clean look. The first reflection hologram I tried looked much nicer than I expected. I'm
guessing the diffraction artifacts from the unfiltered beam make the resulting hologram more noisy and thus less
crisp looking.
Anyhow, thanks for all the advice. After this exercise I can see why spatial filters are a needed part of fine holography.
Cheers.
Re: Spatial Filter
To get the input beam going straight into that spatial filter, I always held a little piece of glass against the input face of the lens holder and retro-reflect the Fresnel reflections off it. I usually have an iris diaphram mounted upstream (my reference for beam height on the table) to make that easier.