"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."
So a transmission grating was simultaneously recorded with reflection image?
I think the self referenced card do the job for this strange and fascinating hologram, could you 'geometrically' analyse it?
(Sorry for the english salad .)
Interesting colors
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Dinesh
Interesting colors
One possibility is that the light went through to the card. part of the beam reflects back onto the plate through Lambertian reflection and part of the beam hits the mirror, either through Lambertian reflection, or if the card were a stiff, shiny card, through Fresnel. That is, looking at the diagram, the beam goes from the card straight up, hits the mirror at 45 degrees and reflects at 45 degrees back onto the plate. This is direct non-imaging light, not image carrying reflected light. Now the direct difuse reflection of the card and the indirect, possibly Fresnel, reflection from card to mirror hits the plate. The ratio would be weak but the transmission grating may be stronger than the reflection image anyway and so appear brighter. The card also may have had a slight tilt towards the plate to it, causing more light to hit the plate directly.
"Sorry for the english salad"
You never need to be sorry for English salad - it's beyond "sorry". Now, Greek salad...!
"Sorry for the english salad"
You never need to be sorry for English salad - it's beyond "sorry". Now, Greek salad...!
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Anonymous
Interesting colors
Here's the way I would look at it. To make it simpler, let's forget the bottle for now, as it doesn't affect the argument.
You mentioned you should look at the hologram in laser light, and this is a good idea. You will get an image for sure, as it is such a broadband hologram, it will give you an image in any laser color!
I think what you will find, if you look at it in laser light, is that the illumination of card is not uniform, but is concentrated in a band going left to right. So when you look at it you see a band of light on the white card, and you also see its reflection in the mirror. So you will see two horizontal bands of monochromatic light. You can now forget that the mirror is creating the second band, and just regard it as two bands of light.
Let's see what happens when we use white light to reconstruct the image. Well, each band will be created in different colors, and because red bends more, the red images will appear lower than the blue and green images. Each band will produce this kind of image, with red below, and blue above. This is exactly what you are seeing in your picture.
I think the confusion arises because you are expecting the spectrum to be inverted as it is reflected in the mirror. But remember that for each wavelength the position of the mirror is different too, so if you could see the mirror in the red reconstruction, it would be lower than the other wavelengths.
Here is an image I created with HoloPov. Imagine the lower row of points correspond to the light on the card, and top row are the reflection in the mirror. I have used a transmission hologram, as HoloPov doesn't do reflection yet, but the dispersion properties would be identical. Hope this makes sense.
You mentioned you should look at the hologram in laser light, and this is a good idea. You will get an image for sure, as it is such a broadband hologram, it will give you an image in any laser color!
I think what you will find, if you look at it in laser light, is that the illumination of card is not uniform, but is concentrated in a band going left to right. So when you look at it you see a band of light on the white card, and you also see its reflection in the mirror. So you will see two horizontal bands of monochromatic light. You can now forget that the mirror is creating the second band, and just regard it as two bands of light.
Let's see what happens when we use white light to reconstruct the image. Well, each band will be created in different colors, and because red bends more, the red images will appear lower than the blue and green images. Each band will produce this kind of image, with red below, and blue above. This is exactly what you are seeing in your picture.
I think the confusion arises because you are expecting the spectrum to be inverted as it is reflected in the mirror. But remember that for each wavelength the position of the mirror is different too, so if you could see the mirror in the red reconstruction, it would be lower than the other wavelengths.
Here is an image I created with HoloPov. Imagine the lower row of points correspond to the light on the card, and top row are the reflection in the mirror. I have used a transmission hologram, as HoloPov doesn't do reflection yet, but the dispersion properties would be identical. Hope this makes sense.
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JohnFP
Interesting colors
Guess I need to go back and look at the set-up again.
Here are a few answers to some of your posts and I know it is not fair trying to make conclusions without actually seeing the hologram.
Illumination was done solely with a quartz halogen light about 4 feet away. The hologram looks exactly the same in sunlight.
I know from a fact that the white card has a matt side and a shiny side, so I will have to look at again it to see which side was up. Knowing what I was aiming for I would say the matt side was up but I will have to confirm.
The white card did move in 3 out of the 5 holograms as there are interesting fringes and void area on the three but the rainbow colors are exactly the same both on the card and the mirror. I will try to take some more photos and show this.
If the dispersion would depend on the distance behind the image plane then the back of the card and the bottom of the mirror would be the same as their distance is the same.
The illumination of the card if very even. I used a meter to measure the intensity of the beam at the four corners of the plate and adjusted until they were even. The light coming through and shining on the card should follow that unless densities of AmDi in the emulsion or the emulsion thickness was different from one side to the other.
I will have to measure if the mirror over the object was exactly at 45 degrees or less or more.
Here is what I observed in the laser light.
1. When I put the hologram in its original location it is very bright as a reflection, it seems brighter then the object actually. As a reflection I see nothing out of the ordinary, EXCEPT... if I try to look from the bottom of the plate to the top just inside the hologram (the top of the mirror) guess what I see? The glass plate itself behind the bottle, although it would be the emulsion side of the plate (Plate 1). What kind of reflection would you get off of DCG emulsion?
2. If I look at the hologram as a transmission at the replay angle and if I get my face right in the plate I see an image of the reflection hologram very high and just under what seems to be a round edge of a collimator but I did not use a collimator.
3. If I put the hologram in the unexpanded laser beam at the replay angle I get nothing but if I put it in at a very steep angle I get a pretty bright real image projected on a card, just as an H1.
Looking more closely in sun light I observed something interesting. The cap of the bottle has a clear plastic covering on it, I guess to insure it has not been opened yet. At a very steep angle I see the reflection off the top of the clear plastic cover cause a ring of reflected light that reflects off the mirror and propagates down the plate (Plate 2). Also I can not see this but it might also be that the front of the clear plastic cover is reflecting a diverging beam back to the plate (Plate 3).
The last hologram made without the mirror has the rainbow visible exactly the same on the white card.
There sure is a lot going on in this hologram.
Dinesh, Can I send you one for observations and analysis? I will let you keep it.
I may do just the mirror and card this weekend as part of my session just to see if taking the bottle out of the equation effects the outcome.
Plate 1
Plate 2
Plate 3
Here are a few answers to some of your posts and I know it is not fair trying to make conclusions without actually seeing the hologram.
Illumination was done solely with a quartz halogen light about 4 feet away. The hologram looks exactly the same in sunlight.
I know from a fact that the white card has a matt side and a shiny side, so I will have to look at again it to see which side was up. Knowing what I was aiming for I would say the matt side was up but I will have to confirm.
The white card did move in 3 out of the 5 holograms as there are interesting fringes and void area on the three but the rainbow colors are exactly the same both on the card and the mirror. I will try to take some more photos and show this.
If the dispersion would depend on the distance behind the image plane then the back of the card and the bottom of the mirror would be the same as their distance is the same.
The illumination of the card if very even. I used a meter to measure the intensity of the beam at the four corners of the plate and adjusted until they were even. The light coming through and shining on the card should follow that unless densities of AmDi in the emulsion or the emulsion thickness was different from one side to the other.
I will have to measure if the mirror over the object was exactly at 45 degrees or less or more.
Here is what I observed in the laser light.
1. When I put the hologram in its original location it is very bright as a reflection, it seems brighter then the object actually. As a reflection I see nothing out of the ordinary, EXCEPT... if I try to look from the bottom of the plate to the top just inside the hologram (the top of the mirror) guess what I see? The glass plate itself behind the bottle, although it would be the emulsion side of the plate (Plate 1). What kind of reflection would you get off of DCG emulsion?
2. If I look at the hologram as a transmission at the replay angle and if I get my face right in the plate I see an image of the reflection hologram very high and just under what seems to be a round edge of a collimator but I did not use a collimator.
3. If I put the hologram in the unexpanded laser beam at the replay angle I get nothing but if I put it in at a very steep angle I get a pretty bright real image projected on a card, just as an H1.
Looking more closely in sun light I observed something interesting. The cap of the bottle has a clear plastic covering on it, I guess to insure it has not been opened yet. At a very steep angle I see the reflection off the top of the clear plastic cover cause a ring of reflected light that reflects off the mirror and propagates down the plate (Plate 2). Also I can not see this but it might also be that the front of the clear plastic cover is reflecting a diverging beam back to the plate (Plate 3).
The last hologram made without the mirror has the rainbow visible exactly the same on the white card.
There sure is a lot going on in this hologram.
Dinesh, Can I send you one for observations and analysis? I will let you keep it.
I may do just the mirror and card this weekend as part of my session just to see if taking the bottle out of the equation effects the outcome.
Plate 1
Plate 2
Plate 3
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JohnFP
Interesting colors
You know I posted the results and went back and re-read your post and at first I could not follow you but then it clicked and it seems to be very logical. So two different beams and red alway reconstructs lower. Great! But where did the coherent reference beam come from? I guess a lot depends on if that card was shiny side up or not and what angle the mirror actually was at. At least I feel I understand the inverted color thingy.
This is so exciting. I now want to incorporate rainbow colors in more of my holograms. Maybe even controll, filter, stear and separate those different colors where I want them.
This is so exciting. I now want to incorporate rainbow colors in more of my holograms. Maybe even controll, filter, stear and separate those different colors where I want them.
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kaveh
Interesting colors
So two different beams and red alway reconstructs lower. Great! But where did the coherent reference beam come from? I guess a lot depends on if that card was shiny side up or not and what angle the mirror actually was at.
As long as there is sufficient coherence length, all reflections in your scene will be recorded. Looking at it in laser light, you should see the reflection, so it is obviously been recorded.
It will be interesting to see how the image looks under laser illumination.
This is so exciting. I now want to incorporate rainbow colors in more of my holograms. Maybe even controll, filter, stear and separate those different colors where I want them.
Yes, you can really do a lot with these colors. As you say, there are just too many things going on in this hologram and it might be better to have a simple hologram to analyse first, then get onto more complex interactions of light. You will find that it is all easy and logical really. So I would say make the simplest scene, for instance just the card and nothing else, and make sure you understand exactly what is going on there. Then move on to more complicated scenes.
You excitement is infectious. Please post any more questions here, but as I say, start simple first, and you will soon find it all fits into place. You can then be really creative because you understand the basics. (Hope I don't sound condescending )
As long as there is sufficient coherence length, all reflections in your scene will be recorded. Looking at it in laser light, you should see the reflection, so it is obviously been recorded.
It will be interesting to see how the image looks under laser illumination.
This is so exciting. I now want to incorporate rainbow colors in more of my holograms. Maybe even controll, filter, stear and separate those different colors where I want them.
Yes, you can really do a lot with these colors. As you say, there are just too many things going on in this hologram and it might be better to have a simple hologram to analyse first, then get onto more complex interactions of light. You will find that it is all easy and logical really. So I would say make the simplest scene, for instance just the card and nothing else, and make sure you understand exactly what is going on there. Then move on to more complicated scenes.
You excitement is infectious. Please post any more questions here, but as I say, start simple first, and you will soon find it all fits into place. You can then be really creative because you understand the basics. (Hope I don't sound condescending )
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JohnFP
Interesting colors
condescending?..... NEVER!!!
I also hope sometimes I do not come off as not believing what someone might know as a fact of physics because of my limited knowledge in physics. I sometimes may question what more advanced studies reveal as fact. But in some ways I like it that way. It gives me a sort of "outside the box" exploration.
I am hungry for this stuff!!!
I also hope sometimes I do not come off as not believing what someone might know as a fact of physics because of my limited knowledge in physics. I sometimes may question what more advanced studies reveal as fact. But in some ways I like it that way. It gives me a sort of "outside the box" exploration.
I am hungry for this stuff!!!
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Dinesh
Interesting colors
"Dinesh, Can I send you one for observations and analysis? I will let you keep it."
Sure. That would make life easier for analysis. There's a lot going on here, as Kaveh says. There are multiple reflections each referencing the other creating all manner of gratings. You also mentioned you had mirrors on the sides. If you could also send me the card and a photo of the bottle and tell me which way up the card was and was it held down in any way. Also diagrams of top view and side view please.
All of this analysis will come at the (very reasonable!) price of a large pint of beer at Churchill's at the next PCGGI.
Sure. That would make life easier for analysis. There's a lot going on here, as Kaveh says. There are multiple reflections each referencing the other creating all manner of gratings. You also mentioned you had mirrors on the sides. If you could also send me the card and a photo of the bottle and tell me which way up the card was and was it held down in any way. Also diagrams of top view and side view please.
All of this analysis will come at the (very reasonable!) price of a large pint of beer at Churchill's at the next PCGGI.
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JohnFP
Interesting colors
If I have the following set up what happens. Will I see the rainbow colors when I view the hologram as a reflection with a point source of white light? What kind of grating will be produced if any?
I always thought I needed a reference beam that was not diffused, I am interested in what would happen in this case.
What about if I did the same thing with blocker, iris and ground glass but put one beam on one side and one beam on the other side for a reflection. What would happen in that instance?
I always thought I needed a reference beam that was not diffused, I am interested in what would happen in this case.
What about if I did the same thing with blocker, iris and ground glass but put one beam on one side and one beam on the other side for a reflection. What would happen in that instance?
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JohnFP
Interesting colors
No mirrors on the sides. Flat black blockers. But I may like to put mirrors on the sides for that really complicated analysis. Trying to figure that one out could be a lifes work.
More info to come.
Pint of Beer? I will buy you that anyway just as a friend.
Peace!
More info to come.
Pint of Beer? I will buy you that anyway just as a friend.
Peace!