hi everyone.
i am trying to build a time-varying holography setup. i have always read some texts but couldn t find a drawing. i have searched all university databases which contains more than 50 sources and thousands of texts. but i only have informations. can anyone provide a scheme or drawing, or share his/her experiences? and i don t know what is the differences between time-avarage,time-varying and realtime holography? there are lots of studyings using one of these names. any explanation?
merry christmas!
vibration analysis by using realtime holography
vibration analysis by using realtime holography
I have done all the above, and the possible reason that there are no drawings available is that the set ups are generally of the split beam transmission type, although I have made time-averaged single beam reflections.
The categories revolve around the exposure; time varying takes two exposures on the same plate, one before and one after the object is stressed. Deformations become apparent, but analyzing them quantitatively is not for the week of math.
Real time requires exposing, then developing the hologram in place or replacing it precisely in position (and is not impossible, but not easy, either!), then reconstruct the virtual image while still illuminating the object so that real object's wavefront interferes with the stored holographic wave and creates interference fringes that indicate the change in shape due to stress. This real-time analysis could be used to find the resonant nodes of a vibrating object, like a speaker, useful for making a time-averaged hologram, which is exposed while the object is ringing! Hard to believe this works, but the nodes of the waves are stationary, so that part of the object comes out nice and right, and the anti-nodes are moving, so they come out black!
I answered a help wanted ad in the Chicago Tribune in 1984 placed by a company called Magnaflux, inventors of the Magnafluxing technique for non-destructive testing. Being the '80's, they wanted to broaden into new technology, and holographic non-destructive testing was one avenue. I got the job because of all the people they interviewed, Ph.D.'s and engineering types, I was not only the only one who had ever even made a hologram, but brought one made in my basement lab to the interview! So I got hired because they saw that this bohemian-artist-educator type knew what he was doing, plus they didn’t have to pay me so much since I didn’t have an advanced degree! But I didn’t realize that at the time, I was making the most $ in my life!
I revived their ancient Spectra-Physics 124, the original model, by placing it in a bag of helium for a while. This trick does work, but usually not for long. I made a time varied single beam reflection hologram of a hard-boiled egg in a C-clamp, just giving the smallest amount of torque to the clamp screw to induce fringes on the egg shell! They showed the board the progress I had made and I was the Golden Boy! Got a Laser Technology (John Newman) in place developing holo-camera, looked at a test object of an aircraft composite skin that had 23 typical defects built-in, found them all, X-rays only caught 21, got a first generation Coherent Innova Argon laser and built an 8 foot by 8 foot isolation table, to inspect really big stuff, but the plug got pulled when they were being put up for sale, as it didn’t look like holography, although they believed in it and me, wasn’t going to make a profit for them for a few years. They blamed their demise on not getting into new technologies earlier.
To further add to my “street cred” in holographic NDT, I got to sit in on the Interferometry Workshops as a fringe benefit for working as the lab manager for the hands-on part of Dr. Jeong’s Holography Workshops. There I got to rub elbows with some of the greats in the world in the world of NDT, Chuck Vest, Nils Abramson, (should get the books authored by both of them!), Rich Pryputniewic, John Newman, TJ himself, etc.
Maybe if you do come to Chicago we could do some experiments in the above domains!
The categories revolve around the exposure; time varying takes two exposures on the same plate, one before and one after the object is stressed. Deformations become apparent, but analyzing them quantitatively is not for the week of math.
Real time requires exposing, then developing the hologram in place or replacing it precisely in position (and is not impossible, but not easy, either!), then reconstruct the virtual image while still illuminating the object so that real object's wavefront interferes with the stored holographic wave and creates interference fringes that indicate the change in shape due to stress. This real-time analysis could be used to find the resonant nodes of a vibrating object, like a speaker, useful for making a time-averaged hologram, which is exposed while the object is ringing! Hard to believe this works, but the nodes of the waves are stationary, so that part of the object comes out nice and right, and the anti-nodes are moving, so they come out black!
I answered a help wanted ad in the Chicago Tribune in 1984 placed by a company called Magnaflux, inventors of the Magnafluxing technique for non-destructive testing. Being the '80's, they wanted to broaden into new technology, and holographic non-destructive testing was one avenue. I got the job because of all the people they interviewed, Ph.D.'s and engineering types, I was not only the only one who had ever even made a hologram, but brought one made in my basement lab to the interview! So I got hired because they saw that this bohemian-artist-educator type knew what he was doing, plus they didn’t have to pay me so much since I didn’t have an advanced degree! But I didn’t realize that at the time, I was making the most $ in my life!
I revived their ancient Spectra-Physics 124, the original model, by placing it in a bag of helium for a while. This trick does work, but usually not for long. I made a time varied single beam reflection hologram of a hard-boiled egg in a C-clamp, just giving the smallest amount of torque to the clamp screw to induce fringes on the egg shell! They showed the board the progress I had made and I was the Golden Boy! Got a Laser Technology (John Newman) in place developing holo-camera, looked at a test object of an aircraft composite skin that had 23 typical defects built-in, found them all, X-rays only caught 21, got a first generation Coherent Innova Argon laser and built an 8 foot by 8 foot isolation table, to inspect really big stuff, but the plug got pulled when they were being put up for sale, as it didn’t look like holography, although they believed in it and me, wasn’t going to make a profit for them for a few years. They blamed their demise on not getting into new technologies earlier.
To further add to my “street cred” in holographic NDT, I got to sit in on the Interferometry Workshops as a fringe benefit for working as the lab manager for the hands-on part of Dr. Jeong’s Holography Workshops. There I got to rub elbows with some of the greats in the world in the world of NDT, Chuck Vest, Nils Abramson, (should get the books authored by both of them!), Rich Pryputniewic, John Newman, TJ himself, etc.
Maybe if you do come to Chicago we could do some experiments in the above domains!
"We're the flowers in the dustbin" Sex Pistols
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holorefugee
vibration analysis by using realtime holography
I have done some of this myself. I was doing vibrational analysis. I have done both time-average and real time. It is a challenge to vibrate something and keep your optics stable. I was able to make Chladni patterns in small diaphrams.
For real time make sure to have a 6 point plate holder. You can make one if you understand the purpose.
For real time make sure to have a 6 point plate holder. You can make one if you understand the purpose.
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tarzan
vibration analysis by using realtime holography
i found a book named'handbook of hologrphic interferometry' authored by thomas kreis. there are some usefull drwaings. if i can manage to build a setup i ll share my experiences here,like how you can t do it:P 
^_^ i couldn t find the books of Chuck Vest, Nils Abramson. i want to ask if any ccd camera can be used for laser vibrometry. do you have any information about it? i have read some texts written in 1994,and i don t think they have incredible cameras when they were studying on it , am i wrong?
^_^ i couldn t find the books of Chuck Vest, Nils Abramson. i want to ask if any ccd camera can be used for laser vibrometry. do you have any information about it? i have read some texts written in 1994,and i don t think they have incredible cameras when they were studying on it , am i wrong?vibration analysis by using realtime holography
I'm using to do real time holograms with Croma photopolymer green sensitive, since the film is almost solid and laminated onto glass plates I did not observe any fringe contrast with the original subject with hologram superimposed, maybe necessary a micrometre to move the object few fringes? The images are designed to be masters for hologram copy onto another emulsion, just photopolymer provides a real time image each shoot.
vibration analysis by using realtime holography
Using CCD's as the recording material would change the realm of the experiment into speckle photography or shearography, since they don't have the resolution to resolve fringes of the holographic spacing size. But using a digital camera to look through the hologram and record real-time experiments is a good idea, most of the experiments I had described above were viewed with a tube CCTV camera looking through the holograms, which were usually small, because the to use holographic NDT you are not concerned necessarily with the 3-D aspect! The LTI device described above made holograms about 25 mm in diameter; the Newport Thermoplastic camera made holos about 30 mm square, for one ey viewing.
If you were doing a quantitative analysis of holographic NDT you would use a fixed viewpoint and count fringes from there.
If you were doing a quantitative analysis of holographic NDT you would use a fixed viewpoint and count fringes from there.
"We're the flowers in the dustbin" Sex Pistols
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tarzan
vibration analysis by using realtime holography
i will try recording realtime hologram, but i have an idea. i want to record it with infrared laser and observe the fringes with a camera. so that i can measure how long the vibrations of different parts will take to calm down, and if i see that everything has been settled, then i can start to exposure of film. i wonder how will effect the fringes, recording with a red laser and illuminate with infrared laser,or vice versa. i have read your message from old holographyforum,mr wesley, you mentioned agfa films which are sensitive to 750 nm.which one do you suggest, recording with red and illuminating with IR, or both recording and ill. with IR?
vibration analysis by using realtime holography
For this type of work, especially if you want to do real-time inspection, the recording and replay should be the same. Switching wavelengths changes the image, size being the most obvious, in proportion to wavelengths, plus the seven deadly aberrations rear their ugly heads. If double-exposed holographic interferograms are looked at with laser wavelengths other than those that were used in the recording, the fringes will be there, but quantitative analysis will be impossible.
The old Agfa emulsions had a sensitizing dye that gave let them see out to 750 nm according to their spec's, and I even shot at 780 nm with them using a big Ti:Sapphire laser, but the sensitivity was about a tenth of that at the He-Ne 633 nm. So you are limited to the Near InfraRed, if you can find any stocks of the Agfa stuff, as it seems most of what is on the market nowadays doesn't work for ruby at 694 nm, much less any NIR.
Oh well, here I go again being the practical pessimist!
The old Agfa emulsions had a sensitizing dye that gave let them see out to 750 nm according to their spec's, and I even shot at 780 nm with them using a big Ti:Sapphire laser, but the sensitivity was about a tenth of that at the He-Ne 633 nm. So you are limited to the Near InfraRed, if you can find any stocks of the Agfa stuff, as it seems most of what is on the market nowadays doesn't work for ruby at 694 nm, much less any NIR.
Oh well, here I go again being the practical pessimist!
"We're the flowers in the dustbin" Sex Pistols