Laserscope Modification Just Finished!

[Photonbeam]

I don't think you can chop the beam fast enough without focusing / recollimating the beam and chopping at the focal point or by using an optical lever.

[weartronics]

I don't think you can chop the beam fast enough without focusing / recollimating the beam and chopping at the focal point or by using an optical lever.

I agree. Of the two methods, I recommend the optical lever, because it's possible to achieve full analog modulation this way, it's more versatile than simple blanking.

[dave]

I agree. Of the two methods, I recommend the optical lever, because it's possible to achieve full analog modulation this way, it's more versatile than simple blanking.

You have retro reflector pictured Nic

[mixedgas]

You need some OLde SKool technology..... Requires thinking on the tuning.......

see attached. Can be done as very nearly inline. Make the distance from the galvo to the lollypop as long as possible. Actually gives good intensity control.

A friend and I got tired of aligning 3 arms into telescopes in a split and recombine color system, yes 5 dichros to do RGB color with argon/hene. Direct diode modulation only worked in the IR back then.

Use a small mirror.

Tune the blanking amp by replacing your Y galvo with the blanking galvo, load the "rainbowed" square wave torture test pattern that comes with pangolin. It consists of a lot of ups and downs in one scan. The X axis galvo scans across, set it to a wide scan., The blanking galvo scans up/down. Make the Y axis size about 5 degrees and tune for least ringing on the sharp square waves. Alternate between a set of triangle waves and sqaure waves for final tuning. We had about 12 sharp little waveforms in our patterns. Very close together. Set the scan rate for 65% of the desired final speed, ie about 22K for 30K pps etc. Your using your X galvo to make a oscilloscope this way. We did it with g124s, your milage may very with cambridges depending on the amplifier topology.

Matt came up with the use the galvos as a scope/nasty sharp waveform tuning trick. When I first saw the pattern he was tuning on, I nearly slammed the power off. But Darn if it didn't work quite well, once explained. Key is to keep the blanking drive small signal and small angle.

See attached.

Steve

[Laserman532]

the problem with retro reflector - beam too big, mirrors too big, speed too slow, lever arm too long - FREAKIN SCATTER EVERYWHERE

the problem with lollypop - beam is too big, hole would be too big any deviation of beam through lollypop will cause walk off of scanners especially if lever arm too long, *EDITED: This techinque works fine with very tiny beams with little beam walking characteristics.*

there is the cylindrical lens method as well as the 2" focal length method with flag - both of those have problems worse than the two methods above.

blank with q-switch gets 90% depth of modulation - and is lightning fast FPS might be an issue

you may also consider no blanking at all because in q-switch mode ya gots dots any way and to blank with a q-sw in CW mode... as far as I know....only weartronics and I know how to do it and I aint talkin (it is really more trouble than it is worth and you still have to deal with FPS BIGTIME) Keep in mind I use to make earrings out of BLOWN KTP Crystals

but then again...maybe you should try all of those methods and report back

basically...yags are a bitch to blank

[Laserman532]

note blanking control on top left of cobra controller

it was not easy to get to work great...but IMHO it is the ONLY way to go

[weartronics]

You have retro reflector pictured Nic

I sure do! Both mirror/pinhole blanking and retro reflector blanking rely on the same optical lever effect. I think these are the two main techniques, but if you know some other good configuration please share it! The only references I know on this topic are the L. Michael Roberts book, and two sentences on the OSLS site.

Mirror/pinhole is easier to make than retro reflector, but you will see some artefacts because you are steering the beam as you blank it - it comes out at a different angle! The purpose of the retro reflector is to eliminate those artefacts.

A further refinement of the retro reflector idea I learned from Eye Magic. If you can build an adjustable retro reflector less than 90 degrees, you can use a conventionally sized and rotated galvo mirror, so the speed and tuning of the blanking galvo will match your X/Y galvos. That's what is shown in that picture.

[prodjallen]

Well You guys might laugh at this, but I was trying to blank by cutting the beam using the right most tip of the mirror like by hardly touching the beam and deflecting the blanks to a beam dump... Would this work? If not why? and how can i fix that? Another issue is that EVEN if i do the pinhole method, at low powers like at 18amps, i get a thin beam, then when i go to higher powers, my beam gets thicker by about 1.5mm. What do you guys think i should do? I want to do the pinhole method if the tip of the mirror idea wont work lol

[weartronics]

What do you guys think i should do?

If you only need beams, the mirror/pinhole method should be fine. If you want graphics, I recommend the retro reflector method to eliminate the blanking artefacts.

If you decide to use the retro reflector method, you can use a fixed 90 degree retro reflector with a larger or rotated mirror on the galvo, as described in Laser FX and elsewhere. If you want to use a conventional mirror, so that the blanking speed will match the X/Y speed, you need an angle-adjustable retro reflector mount slightly less than 90 degrees.

[prodjallen]

Would text be considered graphics? the most i would be doing with the laserscope is tunnels, circles, text some simple graphics, can i use the pinhole method for that?

-Allen