Total Noob... Which laser?

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geek

Total Noob... Which laser?

Post by geek »

Hi all,

Total noob to this stuff, and I've got a quick question (I hope).

I can get 2 laser diodes and drivers etc for about $85, a LPC-815 red 650nm ~250mW and a PHR-803T blue/violet 405nm ~ 100mW. This is the diodes, housings, driver boards, heat sink, and dummy test board for the driver, all for $85. This seems like a decent deal to me.

OR....

I can get a 2mW NeHe laser for about the same price.

I'm interested in doing some other experiments etc with the laser/s, but I'd like to eventualy do some holography. I'm just buying the lasers now, not any plates or chemicals yet.

Basically just want to know if those laser diodes would be any good at all for holography when I get ready. Also just what to expect from diodes vs NeHe as far as the beam output goes.


EDIT: Well, seems I found part of the answer here http://www.holographyforum.org/phpBB2/v ... f=2&t=6493

Sorry I didn't search better first. My bad...
wler

Total Noob... Which laser?

Post by wler »

Get the HeNe, I guess for that money you could get a nice 5mW one. Those diodes work only with luck if at all. As a beginner you would like to avoid any unnecessary stumbling block. Even with a perfect laser, you will find that doing holograms is difficult as first. So don't make your life more difficult as necessary by having too many unreliable factors in the game. Once you have all the other factors under control, you may try to get a more tricky laser.
geek

Total Noob... Which laser?

Post by geek »

Well dang, my window ran out on the HeNe. So I bought the diodes. I'll start looking for another HeNe now.

Please forgive the dumb question, but... Assuming you have a good laser, a good film/plate and no vibrations what is it that makes this so difficult? I can tell that it is, I'm not questioning that. It's just I can't quite figure out why? or what it is that makes it so?

I'm glad this is going to be a bit of a challenge. Should make an interesting hobby.

Thanks for the advice.
rzeheb

Total Noob... Which laser?

Post by rzeheb »

Well, in part the difficulty lies in controlling all the interacting variables including (for split beam holography): relative beam intensities, beam polarization, angle of beam to object and to plate (both vertically and horizontally), quality of optics, exposure times, development times, temperature of developing reagents, choice of developing reagents, age/sensitivity of light sensitive media, and don't underestimate the importance of a stable, vibration-free table. I'm sure I missed a few. All can be overcome, but it really is important to have a good, stable laser to start with.

Ron
wler

Total Noob... Which laser?

Post by wler »

geek wrote:... a good laser, a good film/plate and no vibrations what is it that makes this so difficult?
....plus proper exposure (beam ratios) plus good chemistry.... The words are simple.. but just doing it well is not so simple, and there can be a zillion ways a hologram can fail and all what I am saying is that it is best to avoid pitfalls beforehand as much as possible. Imagine you shoot a holo and nothing is seen on it.. where do you go from there? If you can be sure it wasn't due to the laser, makes your life somewhat easier. You first need to have full control over every single factor, and only then you can try tuning lasers etc. And laser diodes are expecially tricky, I guess the low-power ones (<5..10mW) tend to be well-behaved, but the high power ones almost certainly won't work off-hand unless you are very lucky.
geek

Total Noob... Which laser?

Post by geek »

Ok, I suck at chemistry. Good at electronics (my trade E.E.).

So, lots of variables to deal with. Seems I can eliminate some if I do single beam (SBR maybe), but still need a good laser, good isolation table (although if i understand correctly SBR mitigates this some, along with setting the beam ratio in stone) and good film. And I'm going to buy plates from a commercial suppier along with the developer. Not going to try and roll my own yet.

Then I get to muck with some chemistry which should be real interesting for me.

That still leaves, quality of optics (Does SBR setup have any optics other than in the laser itself and the plate?), exposure times, development times, temperatures of reagents, choice of reagents(i thought I'd just use what the manufacture suggested for the plates i bought? am I wrong here?), then age/sensitivity of the media (totaly unsure about this except I know the media ages and loses sensitivity. Using new plates doesn't eliminate this?).

SO even with the "good laser, plates, and table", I see now theres still a lot of other stuff. Thanks for the advice, seems eliminating as many variables as possible is the way to go (unless you just like chaos lol).
Imagine you shoot a holo and nothing is seen on it.. where do you go from there?
Well, knowing I suck at chemistry, that would be my first suspect. I see now there is more to it than just that....

Is there a way to verify the laser setup before you do a shot? So that you know the everything but the plates and developing variables? This is going to be tedious.

Being an EE I am used to dealing with many variables and details and was fairly confident I could do this, now I'm not so sure....
rzeheb

Total Noob... Which laser?

Post by rzeheb »

Geek,
I have no doubt that you will make holograms, probably without much difficulty. But if you are anything like me, the thrill you get after making that first hologram will fade and you will need "more" to get your "fix." Pretty soon you'll find that single beam set-ups just aren't flexible enough anymore. Then you will start to see defects and imperfections that used to be acceptable..... not anymore! Of course you will want to get the brightest possible image. Soon you'll be trying new techniques...... yup, its an addiction.

Ron
geek

Total Noob... Which laser?

Post by geek »

Thanks for the advice guys. I think the only thing for me to do at this point is to just give it a shot. I've got a bead on 3 HeNe heads and a power supply for a good price. The diodes should be here later this week. My plan is to get all that running and play around with it a bit. Then I'll get together an isolation table (I'm familiar with the concept, we used to use them on coordinate measuring machines that I designed motion controllers for). Basically somthing heavy floating on a cushion of air. Once I get all that done I'll order one of the plate kits (plates + developer). Then I think I'll be ready to give it a try for the SBR anyway. I'm perfectly happy starting there and working up to fancier stuff later. And ya, I already have the feeling I'm about to get hooked on a very expensive hobby. I always have that drive that makes me want to do something as good or better than anyone else can. I often fail, but thats another story lol...

Anyway, does that plan sound like it has a decent chance of success? or is there something big I've missed?
rzeheb

Total Noob... Which laser?

Post by rzeheb »

Sounds like a plan to me. Best of luck and keep us informed on your progress.

Ron
Colin Kaminski

Total Noob... Which laser?

Post by Colin Kaminski »

To just try things out you don't need to have a large table. The laser need not be on the table and for Single beam wrok the optics don't either. If you simply have the plate touching the object a piece of 12"x12" tile will suffice as a table. I put mine on a thin sheet of plastic packaging but I doubt if it makes any difference other than to make sure it does not wobble. The cheapest way to start would be to get some 2.5" plates, a laser pointer and a small double concave lens. As long as the plate is touching the object and you make a reasonable effort to keep things from rocking you can make a hologram. Make sure to pick a diffuse white object as your first object.

Once you introduce a beam splitter then a good isolation table starts to be much more important.
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