2 noobie questions

[borgqueenx]

Im ordering 2 new laser modules in about 2 months and im curious if the 3d adjustable dichro's can take a small chance in beam height.One module is 24.8mm and the other one is 26mm.Also im wondering from where the beam height is normally taken. From base plate to inside the laser beam or from base plate to "the outside" of the beam?Thanks!

[michelrietveld]

Hi, from my personal experience it is crucial to start with almost the same beam heights.
This makes it much easier to align and is rather easy to acomplish by taking the highest beam you have and lift all other moduls and the scanhead to match this height.
Beam height is, as far as i know and i am definately not an expert, measured at the heart of the beam to the bottom of the module.

Good to see you enjoy your new hoby so much !
Wish i had the opportunity of putting my build to work.


Michel

[hobbybob]

Hi Borgqueen.

Just get a 1mm metal plate under the 24.8mm high module so to make it 25,8 so it almost matches the 26mm one.
Then you'll be fine. What modules are you buying ?

[taggalucci]

Alternatively use small bounce mirrors mounted on adjustable mounts before each dichro to have ultimate control of near field alignment. I have just reworked my projector this way, as it was way too time consuming trying to get a good near-field alignment using just shims for the vertical axis and correct placement of the dichros to get the perpendicular beams to hit the same point in the horizontal axis. If you have the space, you'll save yourself much hassle using these bounce mirrors. Just mount them on some of Dave's flex mounts or use something like the Newport MM-2 (2-axis mounts).

[laser_freak]

If the laser reflects off of a dichro you only need one mirror. If the laser passes through both dichros, you need two mirrors.

[taggalucci]

If the laser reflects off of a dichro you only need one mirror. If the laser passes through both dichros, you need two mirrors.

Assuming this is an RGB projector you're building...

If you go with the bounce mirror before dichro method, you'll need at least 2 adjustable mounted mirrors. Assuming green is passing straight through both dichros, you'll bounce your red laser into one dichro and bounce the blue laser into the other. The straight-through laser is the only one that needs to be at the correct vertical height to hit the scanners. I used some aluminum sheet metal shims to achieve this. Then you can adjust the dichro and bounce mirror for each additional laser until you get a perfect overlap, first on the dichro using the bounce mirror, then the far field using the dichro. You have to adjust them together as changes to the dichro can affect the near field alignment.

I'll have photos of the revised layout soon.

[LaNeK779]

do as taggalucci says! you can even go the extra mile and bounce the green beam, too, so everything is adjustable. i prefer to have my beams bouncing off some mirrors before hiting the dichros, as this can compensate for imperfections in the built of the projector

you can see some pics here ( http://www.photonlexicon.com/forums/...555#post195555 ) courtesy of sir Norty

[borgqueenx]

Hi Borgqueen.

Just get a 1mm metal plate under the 24.8mm high module so to make it 25,8 so it almost matches the 26mm one.
Then you'll be fine. What modules are you buying ?

okay thanks!
I will probaly buy a DHOM 300mW 532nm and a CNI 1000mW 650nm. both are ofcource a bit overspec. i think these will fit nicely with my 700mW 445nm blue. and else i can always put the lasers a bit down in the software settings.
both 10khz modulation speed.
i wanted a bit more green (like 500mw) but these are really big and wont fit my projector.

[LaNeK779]

why would you need tha ultra fat beam of the 650???

you'll be loosing a lot of power at the galvo mirrors

[norty303]

See this pic for an example of how you can do it. In my case the 637 is fixed, and everything is adjusted to that one. This removes 1 un-needed level of complexity in my opinion.