Being that the holograms are reflection they are probably wavelength selective. So if they want to replay in a color (wavelength) that is not of your laser you will see nothing. You can confirm this by looking at them in white light. If your laser is red and the hologram is red in white light it will be bright in the laser. If the laser is red and the hologram is orange in white light it will look dim. If the laser is red and the hologram is green or blue in white light it may not show up at all.
Peace, have a great day!
I had just made my first hologram!!
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Dinesh
I had just made my first hologram!!
"Which would be better for interferometry? A transmission type or a reflection?"
Transmission, I'd think. It sort of depends on the aim of the interferometry. If you want to do it as a thesis, ie show that you can make an interferogram, then it doesn't matter. You can make a double exposure on an H1, transfer to an H2 and still see fringes and so demonstrate a "proof of concept". However, if you want to show that you can measure fairly accurately using the technique of holographic interferometry, then the exact fringe spacing and width (of the interferometric lines, not the holographic fringes) is fairly important. By making an H2, you'll probably be introducing aberrations. Just the act of viewing a hologram in white light causes small aberrations due to mismatch in reconstruction frequencies and angular spread of the reconstruction beam. These are usually pretty small and don't much matter for a well-made and well-lit display hologram, but will matter when you're actually trying to measure detail down to micron levels by fringe counting and measuring. There is another technique in interferometry where you make the original, flip it to show the pseudoscopic and then replace the object inside the pseudoscopic image. By illuminating the object with the same wavelength as the reconstruction beam of the H1, you now have a beat frequency between the pseudoscopic, holographic image and the wavefront of the light emanating from the object itself. If you now distort the real object slightly, there'll be fringes across it's surface. Of course, with this technique, you have to use a laser illumination hologram and cannot copy to an H2. You might also look up "shearography".
Transmission, I'd think. It sort of depends on the aim of the interferometry. If you want to do it as a thesis, ie show that you can make an interferogram, then it doesn't matter. You can make a double exposure on an H1, transfer to an H2 and still see fringes and so demonstrate a "proof of concept". However, if you want to show that you can measure fairly accurately using the technique of holographic interferometry, then the exact fringe spacing and width (of the interferometric lines, not the holographic fringes) is fairly important. By making an H2, you'll probably be introducing aberrations. Just the act of viewing a hologram in white light causes small aberrations due to mismatch in reconstruction frequencies and angular spread of the reconstruction beam. These are usually pretty small and don't much matter for a well-made and well-lit display hologram, but will matter when you're actually trying to measure detail down to micron levels by fringe counting and measuring. There is another technique in interferometry where you make the original, flip it to show the pseudoscopic and then replace the object inside the pseudoscopic image. By illuminating the object with the same wavelength as the reconstruction beam of the H1, you now have a beat frequency between the pseudoscopic, holographic image and the wavefront of the light emanating from the object itself. If you now distort the real object slightly, there'll be fringes across it's surface. Of course, with this technique, you have to use a laser illumination hologram and cannot copy to an H2. You might also look up "shearography".
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Colin Kaminski
I had just made my first hologram!!
"There is another technique in interferometry where you make the original, flip it to show the pseudoscopic and then replace the object inside the pseudoscopic image. By illuminating the object with the same wavelength as the reconstruction beam of the H1, you now have a beat frequency between the pseudoscopic, holographic image and the wavefront of the light emanating from the object itself."
Getting the film back in the exact same place is very important. One would need to develop te plate without moving it or make a film holder that returns the plate to the exact same place. One way to do this is to design a plateholder from 6 ball bearings to restrict the plate in six degrees of motion. Such a plate holder is described in Practical Holography, Saxby.
Getting the film back in the exact same place is very important. One would need to develop te plate without moving it or make a film holder that returns the plate to the exact same place. One way to do this is to design a plateholder from 6 ball bearings to restrict the plate in six degrees of motion. Such a plate holder is described in Practical Holography, Saxby.
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javamiggs
I had just made my first hologram!!
There something wrong with the link of the image last post. The image wouldnt show up.
My holograms were not that good looking I think. But I want to show it anyway (Im very proud of them really). I know the good people of this forum could "diagnose" how bad it is. =)
Im not really doing display holography (hopefully someday). I just want to learn how to make a hologram, do a holographic interferometry, and study fringe analysis.
My holograms were not that good looking I think. But I want to show it anyway (Im very proud of them really). I know the good people of this forum could "diagnose" how bad it is. =)
Im not really doing display holography (hopefully someday). I just want to learn how to make a hologram, do a holographic interferometry, and study fringe analysis.