Can a hologram work as a concave/convex mirror

holobuddy · Post by **holobuddy** » Fri Aug 28, 2009 5:23 am

I am beginner in the field of holography.
I want to know what will be the reconstruction from a rainbow hologram of a concave/convex mirror (as an object)? :think:
Whether it will work as a mirror? Is it an Holographic Optical Element?

Please provide some information or links. Thanks in advance.

JohnFP · Post by **JohnFP** » Fri Aug 28, 2009 10:07 am

Sure, but it will act as a lens/mirror combined with a prism (the rainbow part).

BobH · Post by **BobH** » Fri Aug 28, 2009 2:07 pm

True for a transmission hologram, John. A reflection hologram will act like a lens/mirror combined with a filter.

favalora · Post by **favalora** » Sat Aug 29, 2009 12:31 pm

Bob, John - Interesting. I did some Google searching (e.g. "holographic mirror") and did find references to physics papers in which people have made them. But I had trouble understanding it. So, really, you can make a hologram that acts as a mirror, in that if you held an object up to it, you would see an image of that object reflected in the hologram? You've done that?

g

BobH · Post by **BobH** » Sat Aug 29, 2009 2:17 pm

If you make an off axix reflection hologram, for example with the reference beam collimated and at 50 degrees and the "object" beam diverging from a point source on the axis, you'll essentially have a combined curved mirror/grating/filter. In laser light, it will act just like that, by bending a focusing filtered reflection.

If, however, you look at your own reflection in it at the bisector of the two beam angles (25 degrees in this case), you'll see your own reflection. The image will be either magnified or reduced, depending on which side you're looking in to, and will also be filtered. Since you're looking at the broad face of the tilted fringes, your reflection comes straight back toward you. The reflection off the first surface of the plate is reflected away.

There are other ways to see a hologram work as a mirror for real world objects, but I'd have to think a bit before I could describe them easily. Need ... coffee ... first ...................

favalora · Post by **favalora** » Sat Aug 29, 2009 2:58 pm

Woah. I have a lot to learn. I wonder if that's how the the cover of the Guinness Book of World Records book worked...? A hologram firm made it.

g

Colin Kaminski · Post by **Colin Kaminski** » Sat Aug 29, 2009 3:22 pm

I still like the proof that a hologram can not reproduce a corner cube. Sorry to drift off topic.

JohnFP · Post by **JohnFP** » Mon Aug 31, 2009 1:10 pm

Thanks Bob, missed that part. :doh:

dave battin · Post by **dave battin** » Mon Aug 31, 2009 1:58 pm

BobH wrote:If you make an off axix reflection hologram, for example with the reference beam collimated and at 50 degrees and the "object" beam diverging from a point source on the axis, you'll essentially have a combined curved mirror/grating/filter. In laser light, it will act just like that, by bending a focusing filtered reflection.

If, however, you look at your own reflection in it at the bisector of the two beam angles (25 degrees in this case), you'll see your own reflection. The image will be either magnified or reduced, depending on which side you're looking in to, and will also be filtered. Since you're looking at the broad face of the tilted fringes, your reflection comes straight back toward you. ......

Wow Bob, you took the words right from my mouth, heres a picture of a DCG HOE i made showing the exact effect you are talking about .............

dave battin · Post by **dave battin** » Mon Aug 31, 2009 2:24 pm

oops uploaded the thumbnail picture!