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Thread: Introduction + "help me pick a laser"

  1. #1
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    Default Introduction + "help me pick a laser"

    Hello all,

    My name is Erik and I'm an addict. It all started about 10 years ago when I got my first red laser pointer. It wasn't long until I disassembled it to find a tiny potentiometer to screw on. I was very excited to find that I could make it even brighter. At the time however, I was quickly cycling through different hobbies until I found chemistry. This was even more dangerous than lasers because you could make things go PFSSST, BANG or BOOM, so I set aside my little laser pointer.

    Fast forwarding to present time I'm now on my 4th year of university studies (chemical engineering) and have rediscovered the joy of lasers. On a leisure trip to china I found some very intriguing (and cheap!) 532 nm DPSS laser pointers at the toy market(!). I bought 2 and brought them home.

    Having recently built a lumenlab style video/computer projector I thought maybe you could do something fun or even useful with these lasers as well, so I took a hard drive platter and cracked it for some decent FS mirrors and glued two of them to a speaker. The result was not very spectacular.

    Then I realized a potentially better way to get that beam moving; off-axis mounted mirrors on motors. So I bought 2 cheap computer fans and a fan controller to go with them. Chopped off all the wings and glued the mirrors on and... voila! Hypotrochoid patterns! Better yet, the fan controller uses PWM, so I could use that to modulate my laser pointer as well.

    Now I am sitting here with a recently purchased LW-45k galvo set realizing that modulating the laser pointer at the required frequencies will not be an easy task and thus I am currently in the process of upgrading to a proper laser.

    That is why I'm so happy to have found you!

    Now here's my first question:
    What's a good laser to start with? My bugdet is fairly limited being a student (this is such a stupid time to start this hobby, but I can't help it ), so I was thinking about maximum $500. I plan to go RGB sometime, but maybe I should still buy a TTL model to begin with.

    The one I'm looking at now is a laserworld 250 mW TTL laser:
    http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=150169683578

  2. #2
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    Hello Erik;

    Welcome to PhotonLexicon! I understand your problem; lasers are an expensive hobby, so being a student is going to be a real disadvantage for you. (Look on the bright side though - soon you will graduate and get a better job, and then you'll be able to afford more expensive equipment!)

    The laser you linked to appears to be a nice unit, and the price is reasonable. It's TTL only, which means you'll probably want to replace it at some point with an analog model, but at 250 mw of power it will otherwise serve you well for a long time. (To compare, my first true projector only had a 100 mw TTL green laser in it, and I had a *ton* of fun with it.) You probably should purchase some laser safety goggles before you buy that laser though. 250 mw is more than capable of causing eye damage, and you will probably be spending a lot of time experimenting with different layouts and alignments with this laser. Safety is important!

    Recognize, too, that you still need a controller (DAC) and some software to complete your projector, so that will add to your expenses. (I'm assuming you already have a box to mount everything in.?.) There are a few free and/or low cost solutions out there (poplescan, Norms laser show DAC, etc), but if you really want to get started right, I suggest the LA Freak kit from Pangolin. Yeah, it costs $500, but you get a complete software suite with it plus a very high quality controller (the FlashBack 3) that supports full analog blanking. (See how expensive this gets?)

    Buying a TTL laser isn't a big deal... There are lots of things you can do with TTL, even when you decide to upgrade to a full-color rig. Of course, you'll be limited to just 7 colors if you do RGB with TTL-only lasers, but that still looks pretty cool...

    Remember, however, that if you buy an analog laser right from the start, you can still use it even if your controller only supports TTL. Then, if you decide to upgrade to a controller that supports full analog blanking in the future, you won't need to replace the laser. And, of course, analog blanking will give you lots more colors, especially with an RGB rig.

    Still, you pay a price premium for analog blanking, so if money is tight I can see why you'd want to stick with a TTL laser to start with. But I prefer to buy the best I can right from the start, rather than trying to "trade up". Of course, I'm not a university student either...

    Adam

  3. #3
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    Welcome to the club Erik!

    Adam is the guy to listen to, he's got some great advice. He's helped me a LOT (among many others) to get my projector to the level that it is... well... errr... was (I just ripped it apart to rebuild).

    I understand the monetary issue. I am also still in school (in fact right now I should be studying for my international business exam which I have tomorrow, the book is open in front of me). Like you realized and Adam reiterated it will be difficult to stay with this hobby with a really low budget. So in the mean time plan wisely and make precise moves. Mistakes can cost more than doing things RIGHT the first time and they can be really discouraging!

    I think the move towards a TTL green isn't a bad one. But from experience I would just go straight to analog. I FINALLY just replaced my TTL green, and in my opinion it was a mistake from the beginning.

    Like Adam mentioned, Safety is a big thing to consider! You can find some very nice goggles on eBay for a fairly low cost. I would also look into buying a laser power meter. It will be invaluable to you, as you can check to make sure your laser is still operating at or above specs(I learned that lesson the hard way).

    Keep the questions flowing, someone will always be around to help out.
    -Max

  4. #4
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    Thanks for the replies. My reasoning behind getting a TTL laser is that even if I replace it in my main projector design it can still be used for other things. Then there's the price of course. If I could find a reasonably priced analog from the start I would get that one. Finding a blue to match a 250mW green will be fun... ugh. Think that'll have to wait until after I graduate.

    Laser goggles is probably a good idea indeed. I already got zapped by my ~20 mW green in the eye once (was testing a random beam coordinates generator at 5 pps). That was unpleasant enough, I wouldn't want to do it with 250 mW. I've also been looking at laser power meters, but they have some really silly prices here in Sweden. For one that can measure up to 100 mW you'd have to pay 2300.

    I do have a DAC actually. I started by using the sound card without any external amplification. MATLAB works great for generating patterns; you just create some position vectors and convert them to sound directly in the program. The problem was that even at max size on the galvo drivers the scan angle was not that great because of the weak signal. So I built an amp using those nifty NE5532 op-amps. At the time I assumed the output would be centered around 0V, because that would be the logical thing for a sound signal, right? Well, never having used op-amps before I did lose some hair before figuring out why the output was offset so far from 0V with no signal. The worst part was that I had seen LaserBoy's site before that, but missed this picture explaining pretty much everything:
    http://www.akrobiz.com/laserboy/p_laserboy_95.html

    I might pick up on the sound card DAC idea again, but I'd need a multichannel sound card for my laptop first. Adding blanking with just 2 channels is tricky! For now I'm using Norm's PLL port DAC. It does have some limitations like very heavy CPU utilization and 8-bit output. Both are very noticable. Eventually I will have to upgrade and the FB3 looks very tempting. It does cost a lot, but comparing it to the other solutions it seems like good value for the money.

    One question about analog lasers: If I buy fairly powerful green and a lower power blue, is it easy to tune them so that the output looks color balanced? Is it possible to optimize a show for maximum laser power utilization (i.e. the greenie is only tuned down when it's required to achieve the desired color and otherwise operating at full effect)?

  5. #5
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    Quote Originally Posted by tocket View Post
    My reasoning behind getting a TTL laser is that even if I replace it in my main projector design it can still be used for other things.
    Yep - I agree. I still have my original 100 mw TTL green, and I still use it for beams and stuff. So yeah, you'll probably find uses for that 250 mw green long after you've upgraded to analog...
    I've also been looking at laser power meters, but they have some really silly prices here in Sweden. For one that can measure up to 100 mW you'd have to pay €2300.
    You can get a Coherent Lasercheck wand from Edmund Optics for around $330. Figure in another $40 for shipping and you're all set. If you run into problems with Edmund wanting to charge you an outrageous sum of money just because you're located in Europe, contact me via PM and we'll work something out. Worst case, I'll buy it and have it sent to my house, then I can re-box it and ship it to you. You'd pay double shipping that way, but it might still end up being cheaper...
    One question about analog lasers: If I buy fairly powerful green and a lower power blue, is it easy to tune them so that the output looks color balanced?
    This is mostly a function of the controller you use. If you use something like the Flashback 3, then yes, it's very easy to adjust your color balance in software. If you're using a sound card as a DAC, then it's going to be more difficult. And if you're using a controller that only supports TTL blanking (Full Auto, Alphalite, Norm's Parallel Port Laser Show DAC, etc), then you'll have to build some sort of biasing circuit into the projector itself. That's a pain in the ass, but even so it can be done...

    I guess the moral of the story here is to buy a controller that supports automatic color balance control and you'll be just fine. Then you can put whatever power lasers you can afford into the projector and still be assured that you can get a perfect white out of it. (And when you don't care about color balance, you can run all the lasers at full power and get super-bright beams!)

    I'm not completely familiar with the LA Studio software that comes with the Flashback 3 controller, but I know that the software that comes with the QM-2000 board actually allows you to set up different projection zones within a show, and each zone can have a different color balance setting. So if you want a graphic to be displayed with perfect color balance, you assign it to a track that is in the graphics zone. But if you ALSO want a bright green fan to be displayed above the graphic, you assign that fan to a track that is in the full-power beam zone, and it will be displayed at full power. Cool, eh?

    Adam

    PS: Thanks for the kudo's, Max!

  6. #6
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    Starting to rethink my choice of the green laser now. I made a $300 offer for that 250 mW TTL, but the seller wouldn't take it even though he's sold them at that price before. To hell with it then I say.

    So, I started looking at those obscenely priced analogs and noticed they're probably CNI. This is a good thing, right? Their prices are still obscene, but this time I provided some good arguments (like the price from lasershowparts ) with my bargaining attempt. This is the model I'm focusing at now:
    http://www.laserworld.com/en/laser-s...odulation.html

    As for the red, it looks like I'm doing like mliptack and building it myself. I ordered some Sony SLD1236VL diodes (130 mW CW according to the specs) that I'm going to power with die4drives. I'm willing to bet they can do more than 130 mW CW, especially with the aid of TEC.

  7. #7
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    Cool

    You might want to have a look at the prices on LaserShowParts.com for the new Laser Wave line of OEM lasers. They're a little cheaper than CNI, yet many people here have purchased them and been quite pleased with the results. (And if nothing else, it's yet another hammer you can use on that other supplier to get them to drop their prices!)

    Adam

  8. #8
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    Ok, now I've picked a laser. I have a 400mW unit on its way from Laserwave. Bridge is a very nice guy to deal with.

    I have also bought the FB3 eval kit, but have not heard anything about it being shipped or so. I ordered it last weekend and the last communication I received was the receipt from paypal. Is this normal for Pangolin? I want tracking numbers!

    This is all very exciting. Already managed to kill 2 of my red diodes though... and my green DPSS from a laser pointer.

  9. #9
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    Don't worry the FB3 will get to you. I personally cant remember if I had a tracking number or not, but I've got mine safe and sound

    Sorry to hear about the lasers you lost. It will happen to the best of us, but hopefully the lesson is learned

    And of course - We want to see pictures when you fire up the 400mw!!!!!

  10. #10
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    Ok, I received the laser this Monday. Pretty amazing considering bridge sent it on Friday.

    The unit came very carefully packed. There was so much tape and bubble wrap around it that it took me a good 5 minutes to reach the box inside of it containing the laser.

    Damn, this thing is powerful! I'm usually not afraid of potentially dangerous things, but I certainly treat this beast with respect, because I know it will fuck my eyes up if they get caught in the beam. Even diffuse reflections make you visually impaired for a few minutes. It's a good thing bridge sent me a pair of safety goggles. Already managed to get burnt on my hand too (painted a black spot and stuck it in the beam for a second; apparently a bad idea).

    Now I need to get a power meter. Bridge says it does at least 450mW, but it would be nice to have a power vs time plot and some tests with modulation.

    Ok, so this thread is also worthless without pics, but behold... it's not worthless anymore. One of the pictures shows a nice comparison between my old and new green laser. Quite an upgrade eh?

    I also have a video clip of it in action here (link might be NSFW because of the ads): http://hidebehind.com/F24071

    Unfortunately it seems the FB3 will be delayed as Pangolin had some trouble with the customs. Hopefully I'll have it next week though.
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