Alignment help for an SP-107 35 mw He-Ne.

[Vidal Wolf]

I traded a laser for a couple of He-Ne heads.
One ionizes, but does not lase. its an oem version of the 127 which is the 107 I believe.
I would like to get some information or ideas on how to do an alignment on one of these beasts. =)
Its going to be a bit more challenging than doing my 60 x argon
thanks. =)
Nate.

[Laser Ben]

Be careful with that deathtrap they call a power supply! ZAAP!

[Vidal Wolf]

Oh i am! i actually tore the whole power supply apart and cleaned the whole thing, shortened the bundled hv wires,and then tore down the good head ,cleaned the tube,frame,and chassis.
it was flickering and the power level was going up and down.
I figured that the dust and dirt that had accumulated on the whole mess had changed the capacitance of the tube resulting in the unstable output after warmup.
Its rock solid stable now.
Now I want to see if I can align the other head and get it to show some color.

[Laserman532]

First ,make sure yo have a very secure mounting for your shooting laser and the victim. Second, you will only be successful if you remove both mirrors (not the mounts) shoot the bore for a clean through shot, install hr and get a perfect reflection, install the OC and get a perfect reflection. I would assume the bore straightners are very close and hopefully someone hasnt effed with the endplates too much. Those are a real PITA to get going.

[Eidetic]

If it's not lasing, you're gonna' need to start from the beginning and send another laser beam down the bore from the OC end with both mirrors out. Be sure to use a beam that stays smaller diameter than the bore while it's going through it! Make sure the beam goes through cleanly, and there's no grazing incidence reflections off the inside of the tube. Take your time. Adjust the bore supports if necessary. be sure that the beam is going through very near the center of the holes for the OC and HR.

Put the HR in and reflect the alignment beam back on itself. Look for flash, the retroreflection modulation that happens when everything is nearly perfect. Put the OC in and reflect the beam back on itself again. Do all the above as perfect as you possibly can! Turn the tube on and see how close you got. Do a small search pattern with the HR to find it. Be careful with those adjuster nuts, they're course. Use the set screws on the sides of the mirror mounts for very fine tuning after you get it to lase with the nuts.

Sorry, Pat pecks faster on the keyboard!

[mixedgas]

Put a sticker on the alignment hene over the output hole. Very carefully poke a hole in the sticker to let the alignment beam out. Now you have a target for the retro reflected beams from the mirror you are aligning. This way your not guessing where your reflected beams hit the aligmnet hene's mirror. Keep in mind the OC optic has wedge built in to prevent ghost beams, so you have to pick the right dot that is reflected off the OC.

If you can, bolt down the target laser, gently..

Big henes take a large amount of patience, and watch, as Ben said, those PSUs will sting you. The PSUs also die quickly if you short or arc them.

Steve

[Eidetic]

That's right ... mount both lasers and the two steering mirrors rigidly or you'll never get it. To make a small target hole for the front of the alignment laser, I poke a wood toothpick through a business card to about 1/2 its diameter. Then, trim the paper deflected around the toothpick with a razor blade. Makes a nice small round hole!

[Vidal Wolf]

*listens and reads intently*
First off. Thank You for the information!
Its really great to be getting advice from some of the best minds in the industry!
Im really looking forwards to sinking my teeth into this project.

A question about the bore. it looks like its maybe 2 mm. now to get a laser to run thru the bore without it grazing the insides is going tto be tricky at best.
Is the purpose of covering the operating laser with a paper disk with a hole thru it to reduce the diameter of the beam? or is it to be able to see the reflection from the HR / reflector setup.
I have a handfull of cylindrical 5~7 mw He-Nes from smelly Melles,and a few of the lab style rectangular Uniphase lasers (the 155SL)and a couple of the pencil sharpener rectangle styles from JDSU. What ones would yield the best or lowest divergence? all are random polarization.
would i want to consider using the big 107 for the job? as it seems to have a very tight beam.
also.
Would it be possible to use a green laser to do the bore alignment? I have a Melles green 1 mw cylindrical head.

[Laserman532]

do not use green you will get very little reflection off of the mirrors. use the laser with the smallest beam, the highest power and the smallest divergence...only you know what you have in your inventory.

line them all up on a table and shoot them across the room...that will tell you which one to use, good luck!

[Eidetic]

The mask with the hole is to be able to see the reflection when it's closer to the alignment beam. The output aperture of typical lasers is large to accommodate mechanical positioning of the laser in the head. You want it as small as possible without causing diffraction rings.

Use the laser with the smallest diameter beam, that diverges least. Don't use a 107 to align a 107. I'd choose the smallest he-ne.

Again, Pat with the fast fingers!