Interesting colors

JohnFP · Post by **JohnFP** » Mon May 17, 2004 9:24 am

Sorry, I wanted to start a new thread as I believe this topic should prove to gain some interesting explainations.

If you look at the Vodka bottle hologram you see that the bottom, which is a white card, goes from red in the foreground to blue in the background. Then you see that the reflection of those colors in the mirror reflect the opposite colors, that is, in the far corner where the bottom white card is blue, its reflection in the mirror is red. Distance from the plate is the nearly the same at that corner. Remember, the light does not hit the mirror directly anywhere. This is puzzling to me. I have to give this some thought as to why it is happening and how it can be used to my benefit for multi color holograms. The more I look at that hologram the more I like it.

JohnFP · Post by **JohnFP** » Mon May 17, 2004 10:36 am

Here is the set up with the colors (approximately) drawn.

JohnFP · Post by **JohnFP** » Mon May 17, 2004 1:17 pm

I cannot figure it out.

Why would the wavelength change at the bottom of the mirror to the longer visible wavelength then get shorter up the mirror.

Am I not getting answers because it is a real puzzle.

JohnFP · Post by **JohnFP** » Mon May 17, 2004 1:33 pm

This drawing is a little more accurate. The mirror, being on a 45 causes one to be able to see the back of the bottle as if its reflection was overhead.

Danny Bruza · Post by **Danny Bruza** » Mon May 17, 2004 1:44 pm

email me so i can send you keys for the
http://www.4c-s.org/v-web/gallery i dont have your email

JohnFP · Post by **JohnFP** » Mon May 17, 2004 1:49 pm

Just click on my logon link at the top of any of my posts!

Arturo · Post by **Arturo** » Mon May 17, 2004 3:16 pm

I, for one, cannot even understand why rainbow colors are seen on the white card... much less why their reflection is "inverted"... Might be spurious interference between the light refected at the card and at the mirror?

JohnFP · Post by **JohnFP** » Mon May 17, 2004 3:30 pm

Got me?

I think somehow I have a transmission hologram in there somewhere. Might be the mirror to card bottom. But why the opposite spread for the two? Neither moves pseudoscopically when You tilt the plate back and forth.

JohnFP · Post by **JohnFP** » Mon May 17, 2004 3:32 pm

That gives me an Idea. I need to look at this holo in the laser. Working with Single beam reflections, I forget to do that some times. I will try looking at it as a reflection and a transmission and see what hidden secrets I can unlock.

Dinesh · Post by **Dinesh** » Mon May 17, 2004 4:34 pm

"That gives me an Idea. I need to look at this holo in the laser."
Now, you're thinking!
Was the white card truly white? In other words, did it reflect diffusely or was it partly Fresnel? How was it attached? A white card just on it's own would have moved unless it was either very stiff or was held down by a piece of glass or some other transparent material? In either case it may have produced a flat wavefront which, when reflected off the mirror, created a grating with the incoming beam. Did it have creases, bends or folds on it? The white card, being at least partly lambertian, would have reflected in the mirror and produced another white card. You effectively had an 'L' of white cards. If the card was even partly Fresnel, you've got a grating.
How are you illuuminating the hologram? Those bands look a lot like a fluorescent light sideways. If there is a fluorescent light illuminating the hologram, this would disperse in the grating. The dispersion would depend on the distance behind the image plane. The bands don't look like braodband 'object' dispersion, they look like 'source' dispersion. I suspect either the card and/or the mirror created a grating.