Improving Red (Maybe ALL) Beams

[planters]

So what Laserwave is proposing is that I "upgrade" to their 637nm single mode laser with a claimed 4x4mm beam size. This is $2500 FOB China

Gasp! Your existing module is out of spec (some pictures will do more than just satisfy my curiosity) and the solution is to purchase another module? Did you get the 638 directly from them?

Are you sure your 506's have 5mm aperture mirrors on them ? (Actual mirrors should be around 7mm x 12mm to fit a 5mm beam size)

The 506 mirrors are substantially larger than even that 7mm x 12mm. They really do accommodate a true 5mm SQUARE (harder than round) beam without vignetting.

It seems a shame to enlarge the other beams in order to match them to a poor red beam. I would focus all my effort on generating the tightest red out of the box and then these techniques can be used to dial everything in.

[resunltd]

Planters,

Gasp! Your existing module is out of spec (some pictures will do more than just satisfy my curiosity) and the solution is to purchase another module? Did you get the 638 directly from them?

Yes, all three lasers direct from Laserwave after a few emails to Bridge. Gasp! is a good word for my feelings at the moment as well. I will post a few pics tomorrow.

On the mirror size issue, what size should the 5mm beam mirrors be? Justin told me that my 506's were paired with the larger mirrors but just to confirm. Does anybody have the dimensions of the standard 3mm mirrors for comparison? Even if I was using "giant" DT40 mirrors and grabbing the entire 6 x 6mm, the red 638 simply does not match up well in size to the 520 and 460 beams.

[m0f]

Please post some pics, as I question whether it really is out of spec. It's possible you may have just been expecting too much

DT40 "large" mirrors (there are only two sizes) are good for a 5mm beam just barely, definitely not 6mm and are about the smallest I would ever use if building a laser to fit the modern multimode diodes, so if your 506 mirrors are smaller than 7x12mm then it likely wouldn't fit the mirrors. (As Planters mentioned above, the 506's are available with mirrors larger than the dt40 large mirrors, so it's possible you received the wrong mirrors)

A beam corrected 638nm built using Dave's 2mm fl lenses w/ cylindricals will barely fit dt40 large mirrors, and it's generally considered one of the better setups for the 638nm. A smaller initial beam could be had, but would be giving up far field divergence to get it.

There's no perfect solution, however for beam show purposes most find the 638nm to be a good compromise at a low cost. If a smaller beam with lower divergence is needed, 637nm / 640nm is the way to go.

As for not being able to combine, that is simply untrue. Sure if looking at it on the dichro it may not appear so, but if the divergence matches then you will not see it in the projected beamshow.

EDIT : Just wanted to add, if looking at it in the near field, even a perfectly setup 638nm will not match up well with 520nm and 445 / 462nm, as if corrected enough they are simply larger in the near field. This however does not affect far field performance much at all. Divergence is by far the most important characteristic to match up.

While it would be nice if they both matched, it's not really an option with 638nm aside from telescoping, etc as mentioned above (which would only be useful if using them for graphics or if building to use with the safety scan lenses for audience scanning as any differences in near field will affect how much divergence they add)

[planters]

Even if I was using "giant" DT40 mirrors and grabbing the entire 6 x 6mm, the red 638 simply does not match up well in size to the 520 and 460 beams.

The minor dimension of the "5mm" mirror for the 506 is 8.0mm

EDIT : Just wanted to add, if looking at it in the near field, even a perfectly setup 638nm will not match up well with 520nm and 445 / 462nm, as if corrected enough they are simply larger in the near field. This however does not affect far field performance much at all. Divergence is by far the most important characteristic to match up.

I agree. With my best projector, shown in the video:
http://www.youtube.com/watch?v=nMonZHMTra4

The red is a little bigger in the near field and the divergence is slightly higher than the blue, but the match is very reasonable at each end. My red is A LOT better than the Laserwave module you have and you can copy this layout (without the extreme cooling) and get over two watts of 638nm.

If the laser they sold you is out of spec then they should take it back, fix it, exchange it or something, but not up-sell to another module. This is why the pics are so important.

Also look at this thread. This is really nice.
http://www.photonlexicon.com/forums/...P73-quad-build

[resunltd]

OK, here are some pics and measurements. The far field is done at 30 ft. no optics. The X is about 21.5mm and the Y is about 7.5mm. The near field X is 7.38mm and the Y is 5.92mm. Seems too good in the Y direction?

As for the 506's, the X mirror is 7 x 7mm including the portion blocked by the shaft mounting. The Y mirror is 5 X 11mm.

[planters]

The far field looks almost square to me as in about X=9mm by Y=7.5mm. The "wings" in the far field are just what spatial filtering is designed to eliminate. Your divergence is actually quite low. The problem is in the near field. Those numbers are not acceptable. You might also try measuring the very bright near field by taking a dielectric coated mirror and reflecting almost all of the beam straight down to the base and then projecting the 1% or so that leaks through on to a surface that you can measure against. If the numbers still hold up and you have some good images that verify that then send that to bridge. You should not be forced to use a scanner designed for a Laserscope for a 2W red module.


You have the 3mm aperture 506 scanner mirrors, but even the 5mm aperture mirrors will not handle the beam you seem to be showing.

[resunltd]

Planters, good idea, I will try the dielectric mirror technique in a few minutes.

The beam looks a lot better on camera than in person. At 30ft the Y is noticeably weaker horizontal lines after about 7.5mm. Regarding the wings, I have tried the 75/75mm spatial filter as per your video. Can't seem to kill the wings significantly without changing the central spot.

[planters]

If you position the blades at the exact focus between the two lenses and this takes a little time then you can remove any far field component you want. You are actually interacting at a focus. On either side of focus, you loose the ability to block a particular feature. If you could find a small transparency and set the power down to avoid burning it, you could project an image at the far field. At 30 feet, the weaker Y spread I am talking about are the wings. They continue to get even weaker yet and then spread well beyond 21mm.

[tribble]

Curious... if the spot in the far field is smaller than the spot in the near field, does this indicate that the primary collimator is not adjusted for collimation, but rather an extreme focus distance of, say, 30 feet? How can you tell if your beam is perfectly (or nearly) collimated vs. focused at some distance?

If you're measuring at 1" and 30', I can imagine a situation where you actually focus for 15' and just think you've gotten great collimation with low divergence, because the spot sizes might be the same, all other things being equal ( which they aren't, given the assymetrical divergence of diodes).

[resunltd]

Here is a better far field pic using a dielectric mirror to reduce the intensity. Also operating at about 35% power. Size is about 20.5mm X by 2.5mm Y. As you can now see, there is a lot of flotsam above the main beam. This makes it look more square in the earlier pics. The near field is about 7.2mm X by 6.2mm Y.

I will contact Justin tomorrow and see about getting a 506 set with the larger mirrors. But first I need to get this red problem solved. What do you think would be the best course of action with Bridge?