Optics for 445 laser show

[lv128]

I'm still in the process of assembling my first projector and I'm using 30K ebay scanners, using a 445, one of jayrob's lens that I originally used for a 405 pointer mounted into an axis module and into a modwerx aluminum heatsinc, and dichros and mounts from LSP.

The two problems I'm running into is the beam shape of the 445 is terrible, no matter how I focus it, the resulting beam is fat and wide, even when I do get a slight dot, there's still alot of splash which doesn't produce a nice dot for drawing.

Are some 445s better than others for beam shape? Are there correcting optics that I need in addition to the lens? Or are there better lenses for shows?

I've read through a number of other people's builds and I'm not finding any mentions of similar problems, unless I'm not searching for the correct terminology.

Second problem, or more of a question is, when I'm adjusting the position of the dot on the galvo, is there some way to set the galvos to a zero position so I know that I'm adjusting the dichro mount correctly?

I apologize if the questions were already addressed, I did try to find some answers on my own, but no luck yet.
tia.

 

[Things]

I installed 445nm in my projector a few months ago. I have a 445nm Aixiz glass lense on order thru Glenn, however I've just been using a regular aixiz acrylic lense in the meantime.

Like you said, the beam is larger than the other lasers, however even with the acrylic lense, it's really not all that bad.

Yes, there are 445nm diodes with much tighter beams than those that came from the Casio projectors, however they'll run you about $500 each from Nichia.

Thats at about 2 metres with the regular acrylic lense.

 

[andy_con]

you need to pop over to PL and get a prism pair to correct the beam

 

[ElektroFreak]

Actually you don't really NEED to, it just depends on how much you're obsessed with the beam shape.. these diodes are plenty good enough for show use as they are with just a simple collimator. I've had one in my projector for awhile now, so I can tell you with absolute certainty that no one in the audience will be able to tell what kind of beam shape these diodes produce when watching a show. I just finished two 445nm satellite projectors, and you'd never know the beam shape when watching a show with them either. Also, the increased divergence on one axis helps a little in terms of safety in the event of an emergency. Normally with show lasers a little bit more divergence is a good thing, so IMO prisms are unnecessary for show use (or pretty much any other use unless you need true TEM00 for some kind of experiment or holography or something). It really is a matter of opinion though.. there's no definite need for prisms like there is with many other types of multimode diodes.

 

[andy_con]

well using an aixiz 405 glass lens i loose alot of the beam off the galvo mirrors so prisims are a must.

 

[ElektroFreak]

When I positioned the beam's line profile diagonally instead of vertically or horizontally I was able to get it all to fit on SP20 mirrors, but it did require very precise positioning and it *just* fit..

 

[andy_con]

indeed hense why prisms are good

 

[ElektroFreak]

Absolutely.. just not worth the effort to me in this case. In my RGB system the blue has the second-best beam after the green.. no need for better when the reds are always so bad most of the time.. only a matter of opinion of course.

 

[andy_con]

i hear what your saying.

im sure you have seen my posts on pl about red beams and trying to get the best beams possible.

im getting to a stage now where i only want perfect quality beams and am happy to go that extra bit to get it

 

[ElektroFreak]

Just don't tear your hair out.. often (in fact the vast majority of the time) with lasers (yes, even diode ones) perfect beams require freakishly expensive scientists and equipment. Even the finest RGB laser projectors that I've seen or heard about that utilize diode arrays have less-than-perfect source beams.. that's not to say they aren't close.. it's the alignment of the laser sources in a projector and beam diameter/divergence of the beams that makes for the best looking output. If all of the lasers in a projector have similar beam diameters (within 1mm or so), divergence, and the alignment is proper (and I mean REALLY proper.. as in if you look at the beam profile of the white beam, it looks like a target with each beam centered perfectly within the other) THAT's where you get your Arctos-like quality. The beam cross-section of each individual source beam is not nearly as important has having the overall alignment right.

Really though I'm just sharing my thoughts. It's your system, and there's nothing wrong with trying to get a system as good as you possibly can, so in no way would I ever discourage that kind of mindset.. but there are limits to what is possible with a home shop.

 

[dnar]

indeed hense why prisms are good

Hi Andy,

Do you mind telling me more about these prisms? The theory, how to mount and align them, how to purchase etc. I tried to find out more at PL, however there appears to be a lot of assumed knowledge in most of the posts there.

I went for the small/standard mirrors on my DT30's, so this will be an issue I will face once my build is complete.

Cheers.