last stages of my laser completion help

[DZ]

I'll be up in Atlanta the week after Thanksgiving. If you're still having problems, let me know, I'll get it fixed up for ya.

[tommylee333]

that would be great, be nice to work with someone who knows what they are doing.

I'll be up in Atlanta the week after Thanksgiving. If you're still having problems, let me know, I'll get it fixed up for ya.

[tommylee333]

---Quote (Originally by tommylee333)---
buffo i have read all the post the pdf files everything on how to alighn a lazer. but i just can't get mine to line up right,
i get the red, the green, the blue, all on the screen, but one is above the other, and one is below the other. and when i turn the adjustments, they start to move together, but before they make it all the way they always get to dim. and then i can only see the one in the middle.
---End Quote---
Hmmm... Ok, this might take a while. Alignment is a big pain, but you only have to do it once.

First, once you have your blue laser mounted, make sure the beam from the blue is passing through the other two dichros and is hitting the center of the scanner mirrors. This blue beam will be your reference beam that you'll match the others to. You may need to adjust your blue laser and/or your scanners in order to get the beam centered on the scanner mirrors. But you need this reference beam to be correct first, before you mess with the other two.

Now, for the other two lasers, it's important to remember the difference between near-field and far-field alignment. Near-field is how close to perfectly overlapping the beams are at the dichro face. (That is, where the reflected beam bounces off the dichro.) For near field to be perfect, the two beams need to be concentric. (That is, they must overlap perfectly and be centered on each other.) You adjust this by moving the 2nd laser (or 3rd laser, if you're adjusting the last dichro). Remember: you *can't* adjust the near-field alignment by playing with the dichro mount. It has to be adjusted by moving the laser.

This near-field adjustment is where most people make their mistakes. They look at the spot on the dichro where the two beams meet and figure it looks close enough. But if it's even a tiny bit off, you will end up with the beams separating from each other as they travel away from the projector. So make *certain* that your near-field alignment is perfect. Use sunglasses and run the lasers at low power so you can really see the overlap spot on the dichro. Make sure everything is perfect. You may have to shim the lasers, or twist them slightly in their mounts in order to get this alignment right. (Note that you don't ever mess with the blue laser. It's your reference beam. You only need to adjust the red and the green.)

Also remember that you need to get the green laser (which is the one in the middle of the chain) dialed in first before messing with the red. Once the near-field alignment on your green is perfect, you should be able to get the far-field alignment adjusted by simply turning the thumbscrews on the dichro mount. This tilts the dichro, which will move the reflected beam but will allow the transmitted beam to pass through unchanged. Thus you "steer" the reflected beam until it perfectly overlays the blue reference beam.

In practice, this is easier to do if you have a long throw (distance between the scanners and a wall). Set it up so you have a good 30 feet or so between the projector and a wall, and look at the dots on the wall. As you adjust the dichro mount, the green beam should move towards the blue. When you end up with a perfect cyan dot, you've got your alignment nailed. Then it's time to move to the red laser.

And again, with the red laser, you must first start with the near-field alignment. So once again, you'll be moving the laser trying to match the red beam with the green and blue beams so that the red perfectly overlaps the green and blue at the dichro face. And once this is perfect, you can adjust the dichro mount to get the far field alignment dialed in.

I can't stress how important the near-field alignment is. It is the *most* crucial alignment in your projector, so don't be afraid to spend an hour or more getting it just right. Near-field alignment is what will make or break your projector, so you want it to be perfect. By comparison, far-field alignment is easy as pie to adjust.

Some people actually install a second bounce mirror in their projector for the red and green lasers so that it's easier to adjust the near-field alignment. With an extra bounce, it gives you a second set of mounts that you can adjust to alter the near-field alignment. This arrangement has extra losses from the extra bounce mirrors, but it makes alignment very easy, since you have adjustable mounts for everything. Here is a link to a drawing of one such layout (http://www.photonlexicon.com/gallery...ayout.gif.html), if you're having trouble visualizing it. I'm not saying that you need to do this with your projector, mind you. You can get the alignment correct just by moving and/or shimming the lasers. But using extra bounce mirrors does make it a lot easier... (Keep that in mind for your next projector build!)

Adam
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[tommylee333]

To reduce the power level, you need to apply a lower voltage to the modulation inputs. Most people do this by hooking up a separate power source to the ILDA plug for the three color signals (red, green, and blue) and then dialing the voltage back until the lasers are just barely on.

If that's too much hassle, you can probably go into your software and reduce the overall brightness of the projected image that way. Or you could temporarily disconnect the modulation wires from the ILDA connector and connect them to a constant source of low voltage. (Something like a 1.5 volt battery will work rather well.)

As for sunglasses, any pair will work, but dark ones are better. The idea is to reduce the amount of light entering your eye so you can see the spot on the dichro better. If you have a set of RGB-rated laser safety goggles, that would be ideal. But if not, sunglasses are better than nothing. (Try wearing two pair...) And remember: reducing the laser power really helps.

Worst case, if you just can't get it, see if DZ will take a look at it when he's in Atlanta the week after next. He's got to go to Atlanta for some training, and he'll be there for several days. He's already offered to have a look at your projector, and he does great work. So if you can't get it aligned by then, let him take a look. I guarantee he'll be able to get it adjusted correctly for you.

Adam

[buffo]

Hehe... Glad to help buddy.

Like I said, if you absolutely can't get it to work, let DZ take a crack at it. I'm sure he can get you up and running, and he works cheap! (Buy him lunch and a beer, and he's good to go!) Plus he'll teach you about tons of other things too. He's a great resource (and is at the top of my go-to list when I have problems)!

In all seriousness though, alignment is not easy, especially the first time you try it. It takes patience. So if you find you're getting frustrated, take a break. But once you get it dialed in, you should be good to go from then on. (Alignment never changes, unless you drop your projector or hit it hard enough to knock something loose.)

Adam

[swamidog]

tommylee333,

pardon the photoshop slap job, but here's another example of using bounce mirrors to help with alignment. in my setup all the lasers (including the green reference beam) hit bounce mirrors before the dichros.

an arrangement like this makes alignment very easy. it also greatly reduces the future work if you replace a laser with a different beam height.

disadvantages are a more complex beam path, mirror loss, and a larger layout.