Page 2 of 2 FirstFirst 12
Results 11 to 20 of 20

Thread: A "Help Me Build A Laser" sub forum

  1. #11
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,488,814

    Default Terms defined...

    Quote Originally Posted by Evolve
    What is a cube, dichro, trichro? And what is an optic table breadboard?
    Let me take a stab at some of these.

    A "cube" is shorthand for a polarizing beam-splitting cube. Basically it's a hunk of glass about the same size as a sugar cube. (say, oh, about 1 cm high.) If you send a randomly polarized laser beam into it from one side, it will split the beam into two separate beams that have opposite polarization. (one will be horizontal, the other vertical). One beam will continue in the same direction as the incoming beam, while the other beam will be "split off" at a 90 dree angle.

    However, you can also use a polarizing beam-splitting cube to COMBINE two laser beams of the SAME wavelength into a single beam. The trick is that the two incoming beams have to be of opposite polarization. (One vertical, one horizontal.) You end up with a randomly polarized beam that is about 90% as strong as the sum of the power output of the two lasers. (The rest is lost due to internal reflections and other losses inside the cube.)

    If you look at this picture (from Liteglow's gallery) you can see the two red lasers just up and to the left of the output. The top laser bounces off a mirror set at a 45 degree angle, and enters one face of the polarizing beam-splitting cube. The other red laser goes straight in to another face on the cube. The resulting output beam has nearly all the power of the two separate red lasers. (And the resulting beam next strikes a "dichro", where it is mixed with the blue beam... What a perfect lead-in to your next question!) 8)

    A "dichro" is shorthand for a dichroic mirror. That is, a mirror that reflects light at some wavelengths, and passes light at other wavelengths. These are used to combine two laser beams that are of different wavelengths into a single beam. For example, a dichro that reflects green but passes red will allow you to mix the red and green beams, producing a yellow beam. (You can also get just red or just green by turning off the other laser.) Likewise, there are dichros that reflect blue but pass red and green. By using two dichros in series, you can add green to red, and then blue to the red-green beam, ending up with all three primary colors. (This is how most low power white-light projectors work.)

    At higher power levels you'll often find one large multi-line ion laser (these are *big* gas lasers with mixtures of krypton and argon that lase at many wavelengths at the same time) rather than three single-line lasers inside the projector. These large ion laser-based projectors use something called a Poly-chromatic Acoustic Optical Modulator (PCAOM) to select individual colors from the rainbow of wavelengths produced by the laser. However, PCAOM's are expensive, difficult to align, and they waste 15% or more of the output power of the laser. Plus they require that all the light be polarized int he same direction. (Not a problem when you're dealing with just one big gas laser, but more of an issue if you're trying to combine beams from several lasers...) Anyway, you rarely see PCAOM's in small projectors. Most people use individual lasers for each color, and dichros to mix the colors together into a single beam. (The color control is done by varying the intensity of each of the three lasers...)

    A "Trichro" is simply a carefully constructed optical component that combines two dichros together in a single unit. It has three optical ports on one side where the red, green, and blue beams go in, and a large output port where the resulting white light beam exits. (Note that they also work in reverse... If you send a white light beam in through the output port, you'll get a red beam, a green beam, and a blue beam out each of the respective ports as well.) Have a look here in the gallery for some pictures of a trichro all set up.

    Most trichros are surplus units that were harvested from 3CCD cameras. These cameras needed to separate the incoming light into red, green, and blue components before sending each component to it's own CCD. That's what the trichro does. So really, using it to COMBINE three beams into a white light beam is actually using it in reverse from it's original application, but like I said, they're reversable.

    An optical breadboard is a flat, stable surface (usually metal, but dense plastic or even wood has been used by some) that has holed drilled and tapped at regular intervals (usually every inch) to make it easy to mount optical components. The optical table is the sturdy, stable surface that the breadboard sits on, though sometimes the terms are used interchangeably.

    There are several ways to make a stable optical table, but unless you're going to be making holograms, you don't need that sort of stability. On the other hand, even for a basic laser projector you'll still need some sort of breadboard to mount all your optics on. (Lasers, bounce mirrors, dichros, and galvos all need to be mounted to the same flat surface so you can align them.) You can start with a metal plate and drill the holes as you need them, or just buy a sheet of aluminum and drill all the holes in advance. If you have a PERFECT layout plan, you can just drill the holes you need. But most people like having the flexibility of extra holes if you need to move something, thus the convention of having holes drilled every inch.

    Guides such as how to make your own fiber optic cable attachment to a laser diode would be sweet.
    There, I can't help you. Fiber optic mounts are a little tricky. I haven't had much experience with this, but perhaps some other members here can help you out.
    In addition, a guide that explain how to take single laser input from diode and split it into two outputs would be sweet too.
    Well, after the "cube" paragraph above, you already know how to do that... All you need is a beam splitter. You don't even need a polarizing beam splitter, since you don't care about the resulting polarization. In fact, in a pinch, even a simple pane of glass will work as a beam splitter. Place it at a 45 degree angle, and you'll get a beam reflected off it, plus the main beam will pass straight through. Unfortunately, you'll get reflections of both the near and far side of the glass, which means your reflected beam will have a "ghost" beam right next to it. Try using a cover slip for a microscope slide. (These are *REALLY THIN* sheets of glass that are only about 1 inch square.) They work really well, and because they are so thin, the second reflection off the back of the glass is barely visible. But they break really easily, so be careful.

    Hope that helps... Feel free to ask more questions. (Have you looked at Sam's Laser FAQ? Lots of good info in there as well.)

    Adam

  2. #12
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    4,382

    Default

    I was re-looking at this thread and being a projector noob too I got a question.. Can I build a DAC that works with popelscan? I've seen some schematics on other threads and talk about bare boards (supply your own components) and what about building your own galvo amps? --Or, do the scanners/galvos almost always come w/ amps? What about a PC-less system. I'd hate to buy a laptop and find it missing during an intermission :? Maybe something that you program at home, disconnect the PC then take it to the show (it holds the program internally)? Is there any such thing?
    Thanx,
    Steve

  3. #13
    Join Date
    Aug 2006
    Location
    North West England
    Posts
    1,148

    Default

    I think Pangolin has a controller that uses a flash card to store the show on.
    As for having a lappy go walk-about, get a kensington lock and cable, they are pretty cheap.

    Jim

  4. #14
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,488,814

    Default

    Hey Steve-o!

    You can indeed build your own DAC. There are plans on the internet for a couple different types. The Bilda DAC is one, and there is this one for poplescan that people were talking about right here on PhotonLexicon a while back.

    Building your own DAC can be educational, and it certainly is economical, but bear in mind that you will have "issues" with the output of most of these DACs... Timing glitches, hot spots, and other issues will plague nearly all parallel-port designs. If you're doing it just for the fun of building something, you'll love it. But if you really want clean output, you're going to want to purchase a DAC rather than build your own.

    Likewise, it is possible to build your own scanner amp, and you can even build your own galvos from scratch if you want. But it is going to require a lot of work, and you aren't going to be able to match the quality of a commercial set. This is why nearly everyone buys a set of galvos with amps. (That is how they are normally sold: an X-Y pair of galvos in a mount with the amps and a power supply.)

    As far as a stand-alone solution, the Pangolin Flashback is probably what you are looking for. Though if you are worried that your computer will get stolen, I'd be just as worried about the PROJECTOR being stolen as well. (The projector is more expensive than your average laptop!) There are some lower-cost laptop solutions (old IBM thinkpads with docking stations, for example) that will give you all the features you need while not being so new and shiney as to attract the casual thief.

    Adam

  5. #15
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    4,382

    Default

    Adam,
    Thanx. Iwaz thinking of trying to get away from a PC altogether. Using a USB DAC with streaming data (as if coming out of PC) but not, going to the DAC. I wonder if this can be done. (I wasn't really worried about having my laptop stolen 'cause I don't have one )
    Steve
    PS-I'm not trying to build a pro setup; just something small and amuzing.

  6. #16
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,488,814

    Default

    Steve-o..

    Ok, I see where you're going with this. The Flashback product from Pangolin is actually a stand-alone playback device, so it's probably what you're looking for. You can store ILDA frames on a compact flash memory card, plug the card into the Flashback unit, and then play the files on the card through the Flashback unit. No other hardware is needed. (Well, apart from the laser, the galvos, and the amps of course!)

    As far as building your own DAC - we've covered that above, but if you go that route you are going to need a PC. (The DAC get's its signals from the PC.)

    To build a stand-alone product that can display graphics is going to require some "pro" hardware, in that you'll need a commercial product that can store and playback ILDA files, of which the Pangolin Flashback is probably the best value out there right now.

    On the other hand, if you're looking for a bare-bones setup that doesn't cost a lot of money, then your original plan to use Poplescan and build your own DAC will be cheaper. (Like, almost free - except for the trivial cost of the parts needed to build the DAC) But then you're going to need a PC to drive it.

    Adam

  7. #17
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    4,382

    Default

    Yeah, that little Flashback unit looks good. They say on their website "sold to OEMs and dealers only" tho.
    Whats up with that?

  8. #18
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,488,814

    Default

    Hey Steve-o...

    I'm not associated with Pangolin, so I can't speak for the company, *BUT*, I have a hunch that you can probably buy that thing with no problems. In fact, I'm pretty sure that the new "hobbyist product" that Bill Brenner has been talking about will use the Flashback 3 board as the playback device, so there you go.

    Besides, if you are building your own projector, doesn't that make you an OEM by default? That would be my arguement!

    I'm hoping that we'll all have some answers soon about the new unit. (Read: I wouldn't spend any money on *anyone* else's DAC for the next couple months - better to wait and see what info is released about the new Pangolin unit first.)

    Adam

  9. #19
    Join Date
    Nov 2005
    Location
    Melbourne, Australia
    Posts
    3,694

    Default

    Buffo is pretty much on it here.

    The FB3 was intended as a standalone, smart media based player. the smart media holds all the laser shows. these can be triggered via DMX, from a lighting desk or what not. I think they can also be triggered via the fb3's serial port as well, not 100% sure on this as i have never had the need to do so

    Pangolin compresses the data, to make better use of the smart media memory, so you can not simply copy a ilda to the card. Instead, bundled with the FB3USB you get a piece of software called LiveQuick. You download to the card from this software.

    LiveQuick also contains a simple drawing/animation portion, so you can create custom frames and animations. Essentially its the same software that has been renamed to CypherLiteUSB shown here (minus the beam effects section, this is customized for neo):

    http://www.neo-laser.com.cn/product.asp?classid=55#

    As a added bonus, LivePRO will also run on the FB3USB hardware, and i believe there is a hobbyist software package in the pipelines that will also use this platform. LivePRO is great, and what i have seen of the new software looks great too

    Hope this helps,

    Dave
    KVANT Australian projector sales
    https://www.facebook.com/kvantaus/

    Lasershowparts- Laser Parts at great prices
    https://www.facebook.com/lasershowparts/

  10. #20
    Join Date
    Jan 2007
    Location
    Anaheim, CA
    Posts
    387

    Default more info

    this thread is great for the newbs... any one have good sites or anything for newbs to find out about building a projector.
    - instinct

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •