That's a wonderful description of your assembly and QA procedures.

Could be immortalized in the Laser FAQ.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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writes:

BTW, as it happens, Sam's Laser FAQ includes a description of the unit
I was building. I don't recall ever seeing the final assembly, but I
sure recognize the oscillator sub-assembly.

"Photos of Varo Rangefinder Erbium Laser"
http://repairfaq.ece.drexel.edu/sam/...c/varopics.htm

Please refer to the following photo:

http://repairfaq.ece.drexel.edu/sam/...ic/varo-lh.jpg

Notice the gold-colored section in the foreground with wires leading
out of both ends. My job was to assemble at least ten (10) of those
every day. I built them up on a base block, using a special jig that
appeared to be manufactured out of monel. It consists of two eliptical,
gold-plated reflectors; the Cr:Er:Glass rod (bottom of the elipse, and
about the dimensions of an ink pen refill cartridge); the flashlamp
(top of the elipse, about the size of a pencil); two metal support
arms; two sets of rubber grommets for sealing the rod and flashlamp
into the assembly via the metal support arms.

I had to inspect under a microscope each laser rod that I used. First,
I had to ensure that the ends of the rod had no more than an acceptable
number of inclusions (bright stars in the field of view of the
microscope) and scratches. Then, I had to use several types of solvents
and some lens tissue to clean the ends of the rod. I had to use the
microscope to ensure that my cleaning had been satisfactory. I placed
the rod in a V-shaped holder in the jig. The assembly would be built up
around it.

The grommets were tough to put on the laser rod. They were made of
rubber, which meant that they would contaminate the ends of the rod if
they touched each other. It is difficult to slip a grommet over a tiny
glass rod without allowing the grommet to touch the end of the rod. The
grommets, themselves, had to be cleaned prior to use, too, and might be
slippery from the solvents. I had to wear finger cots and use tweezers
to handle the laser rod and grommets, and I had to change out my finger
cots every 10 or 15 minutes to prevent my skin oils from contaminating
the laser rod.

Our materials suffered from various defects. The laser rods cost about
$800, and most were coated by a third party. My employer tried to coat
some of the rods, using our own optical shop up the hall. The results
were horrible. Under the microscope some of the rods had just a few
"stars." I understood those were coated by the third party. Other rods
looked like a sea of stars. I understood those were rejected rods that
our optical department had tried to salvage.

The flashlamps cost about $50. Our electronics shop brazed the
electrodes, but the results were often a brittle connection. If an
electrode broke off during assembly of the laser cavity, the cavity had
to be dis-assembled and rebuilt with a new flashlamp. This counted
against the 10 units that I had to assemble each day.

I found it expediant to bend the wires of the flashlamps "gently" when
I took them out of the supply bin, so I could eliminate the brittle
connections before I began assembly. My supervisor eventually noticed
that I was rejecting a lot of flashlamps, and told me not to test them
so aggressively. Of course, those wires could snap later during
testing, but that would not be my immediate problem. And, as long as
our units made it to out troops, breakage was not our problem at all.
However, very few of our units actually shipped. Most failed in
environmental testing.

After I finished building each laser cavity on its block, I placed the
unit on a cart. The next team took these units into a dark room, where
the optics were tested and aligned. Somewhere along that time, the
units were taken off the block I had used and were mounted on the plate
that you see in the photograph. I remember seeing the rotating mirror
(the Q-switch) and the circuit board, but that was a few yards farther
down the room from my workstation, so I did not see it very often. Most
of the time, I had my head stuck in the flowhood, "putting little
screws into little holes," as I like to put it.