Sorry to be a pain and please bear with me but...
What are the four lines coming in from the back? 3 blue and 1 red? What is the rainbow set of lines coming from or going to the object on the right?
I have some thought problems before I actually do some experiments.
If I remove the mirror which is at a 45 degree angle running from the top of the plate to the back of the white card on the "floor" and replace it with another white card that is parallel to the plate and 5 inches away as a back wall (where the virtual image of the white card seems to be in the mirror) will it be rainbow colored?
If I remove the mirror and move the bottle back to the place of the virtual image of the white card in the mirror (which seems to be a back wall), lets say about 5 inches, will it be rainbow colored? Why not?
I know the card itself as a floor with no mirror produces the rainbow color as the last of my 5 holograms is made this way and this is evident. But I believed that to be a function of the distance from the plate. But if this is true then I should be able to place the object 5 inches back and get blue and 1 inch back and get red, right? Or will the object look to be rainbow colored with greater color separation the further from the plate?
So if I have a white card side will it be red to blue from near to far away from the plate or will it be red to blue from bottom to top of plate? And is the latter a function of the replay light angle.
Not sure if I am gaining more understanding or getting more confused.
Must be this dual nature thingy acting in there somewhere!
Peace!
Interesting colors
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Kaveh Bazargan
Interesting colors
Sorry to be a pain and please bear with me but...
You are not getting close to being a pain. Try harder. The more you ask, the happier I am, because that is when I learn most, trying to explain something.
What are the four lines coming in from the back? 3 blue and 1 red?
Oh, those are supposed to show the direction of the recording and reconstruction beams. The coloring is a bug with the program. It just shows that the reference and reconstruction beams are coming from 45 degrees above.
What is the rainbow set of lines coming from or going to the object on the right?
OK. For each image, the program is drawing a line from the eyes to the geometric center of the image. The line is solid till it hits the plate, then continues as a dotted line.
I have some thought problems before I actually do some experiments.
In my experience, the more 'thought problems' you solve before experimenting the better. I try to imagine the whole setup, and the result I expect to get and why, and then the experiment becomes just a confirmation. It takes longer in the short term, but pays off as you understand the fundamentals better.
If I remove the mirror which is at a 45 degree angle running from the top of the plate to the back of the white card on the "floor" and replace it with another white card that is parallel to the plate and 5 inches away as a back wall (where the virtual image of the white card seems to be in the mirror) will it be rainbow colored?
Yes. If it looks the same to you when recording, then it will have the same effect when you reconstruct the image. Of course you will have to change your lighting, as now you have to light both cards. There might be a coherence length issue, too.
If I remove the mirror and move the bottle back to the place of the virtual image of the white card in the mirror (which seems to be a back wall), lets say about 5 inches, will it be rainbow colored? Why not?
Yes. It will be a rainbow blur, but just as blurred as the card was, so you probably won't even know it's a bottle. It might not be as bright as the rainbows you are getting now, and of course narrower in width, i.e. the width of the bottle.
I know the card itself as a floor with no mirror produces the rainbow color as the last of my 5 holograms is made this way and this is evident. But I believed that to be a function of the distance from the plate. But if this is true then I should be able to place the object 5 inches back and get blue and 1 inch back and get red, right? Or will the object look to be rainbow colored with greater color separation the further from the plate?
The latter is true. You will always get the full spectrum, and the further back you go the greater the separation of the colors. Look at your bottle. The front, where the writing is, is almost touching the plate, so there is no dispersion. But if you look at the edges of the bottle, say 1-2" away from the plate, you are beginning to get the colors separating. As you go back, these colors split up more and more.
So if I have a white card side will it be red to blue from near to far away from the plate or will it be red to blue from bottom to top of plate?
All good and relevant questions. Answer is it will be red to blue in both ways. Look at the picture I generated, particularly the set of points away from the plate. The hologram was made with green light. You can see that the green image is replaying just like two cubes, undistorted. The blue points seem higher, and further away too. The red are lower, and closer. So the spectrum is tilted with respect to the plate. But often this is not noticeable, because the whole thing is blurred, and the eye can't focus on any point, and hence can't see the distance changing. So you just see it as 'lateral' dispersion, and ignore the longitudinal dispersion. However, if you were to use just two laser beams simultaneously, you would see this effect clearly.
And is the latter a function of the replay light angle.
It sure is. If we assume recording and replay angles are the same, then the sharper the angle, i.e. the bigger the recording and replay angles, the greater the dispersion. This is true both for transmission and for reflection holograms.
Not sure if I am gaining more understanding or getting more confused.
You are getting there I think because your questions are crystal clear. Don't stop now. Cross examine me with no pity. This is what you should do to anyone explaining something. If they don't like it, it's a bad sign. Please persevere till it's all clear. It'll all suddenly click into place, I assure you.
Must be this dual nature thingy acting in there somewhere!
Maybe, but that's not my department. Hope the above is clear. Next time you're in the lab do some really basic holograms and keep looking at them. By understanding the nature of light, you will become more creative as you can predict effects, not just use trial and error.
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The holographer's home page:
http://www.holographer.org/
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You are not getting close to being a pain. Try harder. The more you ask, the happier I am, because that is when I learn most, trying to explain something.
What are the four lines coming in from the back? 3 blue and 1 red?
Oh, those are supposed to show the direction of the recording and reconstruction beams. The coloring is a bug with the program. It just shows that the reference and reconstruction beams are coming from 45 degrees above.
What is the rainbow set of lines coming from or going to the object on the right?
OK. For each image, the program is drawing a line from the eyes to the geometric center of the image. The line is solid till it hits the plate, then continues as a dotted line.
I have some thought problems before I actually do some experiments.
In my experience, the more 'thought problems' you solve before experimenting the better. I try to imagine the whole setup, and the result I expect to get and why, and then the experiment becomes just a confirmation. It takes longer in the short term, but pays off as you understand the fundamentals better.
If I remove the mirror which is at a 45 degree angle running from the top of the plate to the back of the white card on the "floor" and replace it with another white card that is parallel to the plate and 5 inches away as a back wall (where the virtual image of the white card seems to be in the mirror) will it be rainbow colored?
Yes. If it looks the same to you when recording, then it will have the same effect when you reconstruct the image. Of course you will have to change your lighting, as now you have to light both cards. There might be a coherence length issue, too.
If I remove the mirror and move the bottle back to the place of the virtual image of the white card in the mirror (which seems to be a back wall), lets say about 5 inches, will it be rainbow colored? Why not?
Yes. It will be a rainbow blur, but just as blurred as the card was, so you probably won't even know it's a bottle. It might not be as bright as the rainbows you are getting now, and of course narrower in width, i.e. the width of the bottle.
I know the card itself as a floor with no mirror produces the rainbow color as the last of my 5 holograms is made this way and this is evident. But I believed that to be a function of the distance from the plate. But if this is true then I should be able to place the object 5 inches back and get blue and 1 inch back and get red, right? Or will the object look to be rainbow colored with greater color separation the further from the plate?
The latter is true. You will always get the full spectrum, and the further back you go the greater the separation of the colors. Look at your bottle. The front, where the writing is, is almost touching the plate, so there is no dispersion. But if you look at the edges of the bottle, say 1-2" away from the plate, you are beginning to get the colors separating. As you go back, these colors split up more and more.
So if I have a white card side will it be red to blue from near to far away from the plate or will it be red to blue from bottom to top of plate?
All good and relevant questions. Answer is it will be red to blue in both ways. Look at the picture I generated, particularly the set of points away from the plate. The hologram was made with green light. You can see that the green image is replaying just like two cubes, undistorted. The blue points seem higher, and further away too. The red are lower, and closer. So the spectrum is tilted with respect to the plate. But often this is not noticeable, because the whole thing is blurred, and the eye can't focus on any point, and hence can't see the distance changing. So you just see it as 'lateral' dispersion, and ignore the longitudinal dispersion. However, if you were to use just two laser beams simultaneously, you would see this effect clearly.
And is the latter a function of the replay light angle.
It sure is. If we assume recording and replay angles are the same, then the sharper the angle, i.e. the bigger the recording and replay angles, the greater the dispersion. This is true both for transmission and for reflection holograms.
Not sure if I am gaining more understanding or getting more confused.
You are getting there I think because your questions are crystal clear. Don't stop now. Cross examine me with no pity. This is what you should do to anyone explaining something. If they don't like it, it's a bad sign. Please persevere till it's all clear. It'll all suddenly click into place, I assure you.
Must be this dual nature thingy acting in there somewhere!
Maybe, but that's not my department. Hope the above is clear. Next time you're in the lab do some really basic holograms and keep looking at them. By understanding the nature of light, you will become more creative as you can predict effects, not just use trial and error.
- - - - - - - - - - - - - - - - - -
The holographer's home page:
http://www.holographer.org/
- - - - - - - - - - - - - - - - - -
-
JohnFP
Interesting colors
Ahhh, yes it is getting clearer. The acknowledgement of both lateral and longitudinal dispersion helps a lot. I was trying to figure which one not both. Thanks a million.
Yes, now I want to concentrate on using this color separation to the advantage of a visually apealling hologram.
I will put some side mirrors on. I want to see the "mirror maze" effect.
Yes, now I want to concentrate on using this color separation to the advantage of a visually apealling hologram.
I will put some side mirrors on. I want to see the "mirror maze" effect.
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JohnFP
Interesting colors
As the rainbow is visualized because of dispersion of white light how does the rainbow effect look if the hologram was illuminated with 3 narrow band LED's (Red, Green and Blue)?
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Kaveh Bazargan
Interesting colors
As the rainbow is visualized because of dispersion of white light how does the rainbow effect look if the hologram was illuminated with 3 narrow band LED's (Red, Green and Blue)?
Well, normal white light has all visible wavelengths present, so you see a continuous spectrum. The three LEDs will give you three bands of spectra, centered around their peak wavelengths. Of course with a hologram of an extended object, like your card, this might not be obvious, as the spectra from the different areas of card will overlap and blur each other.
If you get the time, make a simple grating, from two point sources. Or, have an object which is very narrow, like a strip of card. If you have an overhead reference, then the strip needs to run horizontally. You can use this grating to find out the spectral spread of any light. For example you will see that fluorescent strips have sharp peaks, but sunlight has a smooth spread.
- - - - - - - - - - - - - - - - - -
The holographer's home page:
http://www.holographer.org/
- - - - - - - - - - - - - - - - - -
Well, normal white light has all visible wavelengths present, so you see a continuous spectrum. The three LEDs will give you three bands of spectra, centered around their peak wavelengths. Of course with a hologram of an extended object, like your card, this might not be obvious, as the spectra from the different areas of card will overlap and blur each other.
If you get the time, make a simple grating, from two point sources. Or, have an object which is very narrow, like a strip of card. If you have an overhead reference, then the strip needs to run horizontally. You can use this grating to find out the spectral spread of any light. For example you will see that fluorescent strips have sharp peaks, but sunlight has a smooth spread.
- - - - - - - - - - - - - - - - - -
The holographer's home page:
http://www.holographer.org/
- - - - - - - - - - - - - - - - - -
-
JohnFP
Interesting colors
Good idea, I could actually replace the white card with two strips, one horizontal and one vertical just to visually see the spread as you speak of. One thing I have been thinking about is putting a black and white checker bottom. The way I built self contained mirror box, I can easily change the floor with design I wanted. I can even remove the card altogether as it has a clear glass bottom. I can use add a mirror or frosted glass or an array of mirrors for an effect. I can also use the mirrored sides or block them. I have two black blocker inserts the fit in the sides, which I used for some of the last 5 holograms.
I am really pursuing this lighting thingy because the Cicadas that we have, which only show up once every 17 years, will be very difficult to illuminate as they have a lot of orange, red and black. I will either have to paint one or try my best to have a lot of ambient light with most of it being a silhouette.
I am really pursuing this lighting thingy because the Cicadas that we have, which only show up once every 17 years, will be very difficult to illuminate as they have a lot of orange, red and black. I will either have to paint one or try my best to have a lot of ambient light with most of it being a silhouette.