Hello NotMrX!
I see this is something of an antique post, and I hope it not too late to lend some insight as far as cobbling together a functional holography table.
First off let me say welcome to the wonderful world of holograms!
A little background on me: I'm just some guy. I'm a regular cat who got into burning holograms a couple of years ago after developing something of a pop-culture fascination with lasers. I'm certainly no professional scientist nor much of an expert at anything at all. I have, however, slaved over a hot laser for long enough to have gained some practical experience with what works and what does not as far as making basic holograms.
As far as building your first isolation table is concerned:
Sand is a great way to get started, but falls way short of ideal for a variety of reasons.
I'll address first the pros of burning 'grams in a sandbox, then move on the cons.
Bear in mind these three basic tenets of a holography table: Mass, rigidity and isolation.
Why sand is cool:
Sandboxes are easy. They are quick to put together and easy to use. Given enough room, a sandbox is highly versatile - steering beams with mirrors staked in sand is a piece of cake. Setups can be torn down and rebuilt in a short amount of time. They are also very inexpensive to assemble/accumulate.
Why sand is not cool:
*Takes deep breath*
A sandbox alone is not sufficient to isolate from ambient vibration. Any sandbox you use will need to be isolated in the same fashion as any other mass you use. It will take a lot of sand to have sufficient mass. A sandbox is messy and dusty. A sandbox will sag. A sandbox is dusty. Beams will wander and drift over a surprisingly short period of time. A sandbox is dusty. If you plan to incorporate a spatial filter into your setup (highly recommended), it will only stay dialed-in for minutes at a time. Oh, and a sandbox is dusty.
Please don't think that I am against you building a sandbox to get started in holography. It truly is the simplest way to get started. A sandbox will not, however, be the table you want to stick with for the long haul. At some point in the future, if the holobug has found a suitable host in your bloodstream, you will find yourself desiring a rigid table with a steel top upon which you can magnet your optics. Your rigid steel-topped table will most likely be isolated from vibration by means of inner tubes inflated soft.
Other issues to address if you plan for success with holography:
Your laser - In your posts so far you have not given much information as far as the particulars of what you are lasing with. Not all lasers are created equal. Yes, a laser does, by nature of it's basic operation, emit a single wavelength of light, but many lasers do not maintain a stable frequency. You laser is likely to operate in multiple longitudinal modes, and if those modes do not remain "locked in" inside the cavity, you will see mode hops. If your laser hops modes during an exposure, your hologram will forever be marked with "sliced bread" - an irritating phenomenon of fine parallel stripes washing over the surface of your image. You want to avoid mode hops. One way of doing this is to perform your holography with a SLM (single longitudinal mode) laser. This option is expensive. HeNe lasers operate in multimode but are stable after sufficient warm up time. HeNe's are reasonably affordable and a good way to get started, though are bulky and fickle. In an ideal world, you could obtain some green-sensitive film and find a Coherent Compass at a great price. ;)
A baffling deal on a single mode laser is unlikely, of course, so simply get to know your lasers and find one with a stable output.
A really helpful hint (and listen up now, hear?) - Don't leave beam ratios or exposure times to chance or think you can eyeball it. Obtain an accurate light meter. If you have the dough, purchase a Coherent LaserCheck. You will never regret this. Just stick that hog in front of your dummy plate (both sides for reflection or one side with beams blocked in turn for transmission) to see exactly how much light your film is seeing. Never regret it, I say. The LaserCheck is AWESOME - it will give you numbers in microwatts (microjoules per second), and calculating accurate exposure times is the kind of math you can do in your head with that tool in your arsenal.
A final note: I noticed in your previous posts that you are hunting for a beam splitter and I commend this. Split-beam holography is the real deal - but - know this: you will not be successful with split-beam reflection holography until you have a very very stable table.
Best of luck good sir!
