Dennisyuk Question

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Dutchelm05

Dennisyuk Question

Post by Dutchelm05 »

Good to hear from you John,

I was hoping to bring the discussion back to the idea of moving the routing mirror during exposure and of that can smear the reference beam without effecting the return object beam. This would at least for Dennisyuk set ups reduce the need for a spatial filter.

Dave says he moves the beam slightly. This is done when he exposes a plate for a while then the shutter is closed, the mirror is moved and then the exposure resumes.

I guess I just find it strange that it would not cause a new fringe to occur causing a flawed hologram.

I tryed a different curved mirror, less magnification, and it too has some smaller rings. I will try Joe's suggestion again with a regular lens. I did not see the rings when I first set up, but it may have been because the resulting expanded beam was small (not a very fast lens). If I see it with a normal negative lens then I could have some small burns on debris on my 458nm laser window.

Hope you all are having a fine weekend!!
JohnFP

Dennisyuk Question

Post by JohnFP »

I was hoping to bring the discussion back to the idea of moving the routing mirror during exposure and of that can smear the reference beam without effecting the return object beam.
That's a good technique. I wonder if it would work with a multimode laser? make an exposure half of what it is supposed to be, then when you move you beam you have a slight chance of moving it where the light would overlap the dark fringes from the mulimode interference.

I will give it a try and see if it reduces the sliced bread.
dave battin

Dennisyuk Question

Post by dave battin »

Hi guys. The reason to move the beam slightly is to help erase the darkbanding seen sometimes (as if to overlap the darkbanding), if the beam is moved only and not the mirror the ref beam angle will still appear the same, if you redirect the mirror you will end up with two referance points,causing doubleimaging. Its important to have the concave mirror placed as far away from laser as possible,(taking advantage of the laser's divergence), causing the beam to spread nicely. Check this, set your mirror up close to laser and see the spread,then set you mirror back a good distance ( 20 feet with my 315 laser)and see the divergence difference ...................
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