Slashdot Mirror
Making Holograms In The Kitchen
Paul writes "Over at www.litiholo.com is a newly launched
hologram kit that lets
you make your own holograms at home. No, it's not Princess Leia asking you for
help, but it's still pretty cool making a hologram on your kitchen table. Particularly
interesting is the instant
hologram film that makes holograms with no developing (kind of a Polaroid
film for holograms). The hologram kit costs $99, including the laser, film, and
everything else."
You can get it from Amazon. It's Shoebox Holography
Has sold holography kits for years. Currently they have a book Showbox Holography which shows how to set up a small lab to shoot holograms with a pen diode laser. They used to have a neat kit with a HeNe laser back in the day, but it wern't no $100 bucks. *cough* I haven't looked at an Edmund Scientific catalog for over a decade, but they seem to have shifted from the home hobby lab market to strictly the teaching market... shame. --M
I am not totally sure, but I think the kits sold at the linked site require the use of a laser to view the hologram, they are not white-light holograms. Instead you might wanna check out this site and their hologram kits, I plan on purchasing the Standard Kit. http://www.holokits.com
Note that the author of the article "Paul" is associated with the company (based on his email address). But at least he's honest in not trying to hide that info.
It is ordinary film (in a sheet film format, I used to use black and white 4x5" film that's about $1/sheet in 25 packs.
Basically, to make a hologram you start with a single source of monochromatic and in phase light (a laser), split the beam into two so they will still be in phase and at the same frequency. Then use one beam to illuminate the film directly (referrence beam) and the other to illuminate the object and then the film after bouncing off the object (subject beam).
The result is that you create an interference pattern of lightwaves on the film, and depending on the shape of the object, the waves in the subject beam are delayed by various amounts.
The result is that when light passes through this interference pattern on the film, it forms a real (3D) image of the original object that caused the interferrence pattern.
Jason
ProfQuotes
This kit uses a laser diode, not a NeNe laser. As far as I know the laser diodes just aren't as good. They also use some sort of instant film, which has its perks; I don't have the time to spend in the darkroom anymore, but I'll believe the quality when I see it, though I am quite interested in seeing it. I wonder if anyone who doesn't have fond memories of making holograms would be at all interested in this kit. It seems to me like more of a nostalgia thing like tbose old video games than a cool new thing.
Jason
ProfQuotes
This kit uses a laser diode, not a NeNe laser. As far as I know the laser diodes just aren't as good.
Yes, laser diodes have a much shorter coherence length than HeNe's, in the order of 10-20cm whereas a HeNe can easily reach coherence lengths in the tens of kilometers range.
The coherence length of a light source determines the maximum path length difference between two beams for which you can still get interference.
It is important for holography since the whole process relies on interfering two beams in the plane of the holographic plate.
But if you carefully adjust the path lengths of both the object and the reference beam (by putting delay lines into your setup - you can simply build them out of two additional mirrors, for example...), you can surely make holograms out of small objects with a diode laser.
why do you want long coherence lengths? because you need to make sure that at every point on the film the path lenth difference between every ray you want to capture and the reference beam is within the coherence length. As a starting point one would say that at a minumim it should not be less than the width of the film or the width/depth/height of the object or scene which ever is greater.
Looking at thepicture of the kit, the film and object are many times the cavity size of the a typical internal cavity diode laser. And dhiode lasers have sucky coherence normally.
are there some clever ways of lighting a scene that can minimize the coherence length requirements?
I note that the systemin use is a single frequency hologram not a white light hologram. thus the play back has to be done by a monochromatic light source. It must be the arrangement they are using is not a thick film hologram but a thin film hologram.
any ideas on the geometry they are using and how they are handling the coherence length issue???
Some drink at the fountain of knowledge. Others just gargle.
There are several types of holograms. The traditional one, AFAIK the first one produced by Gabor, the inventor of holography (BTW... he originally invented holography to make better electron microscopes and not pretty 3D "pictures" :) was a transmission hologram.
;)"
For a transmission type hologram, you split your laser light into two beams, one directly hits the holographic plate and the other one bounces off the object and hits the plate afterwards.
To reconstruct this type of hologram, you need laser light (or light with similar coherence features).
The white light hologram (? "Weisslichthologramm" in german) is even simpler to make and can be reconstructed in white light from a point source.
By positioning the object behind the plate, the part of the beam that is transmitted through the plate hits the object and interferes with the incoming wave in the plate. This type of hologram can be reconstructed in white light because parallel interference stripes form in the plate which act as a colour filter. "The hologram makes the light the way it wants it to be...