The laser is a pulsed ruby in the long wooden box on the right. Its a JK lasers system 2000, described elsewhere. That is not the original case. The laser is sitting on top of its power supply, which is mostly obscured in this shot.
The subject sits on the left side, under the PVC gantry facing the black card under the angled diffuser. The plate goes in front of the black card and the reference beam shines down on it from the mirror on the gantry, behind the subject.
The subject is illuminated by the diffuser. My math indicates it is eye safe, as defined by ANSI. However it is only eye-safe for the subject. Everyone else in the room may get a stray specular reflection. I verify the various alignments by taking pictures.
The diffuser itself is a piece of ground glass. They don't sell pieces of ground glass that big... I bought some aluminum oxide abrasive off ebay and ground it myself. Its remarkably easy, should you need a piece of ground glass. I also tried grinding plexiglass with it. While the plexiglass looked OK, the laser was not quite diffused by it. An un-diverged beam from a laser pointer could make it through the diffuser, though it was attenuated. The glass did not let any of the beam through.
Most of the optics are on a piece of plexiglass directly in front of the laser. The laser comes out of the box, goes through a half wave plate, and then hits a prism. The prism is the beam splitter for the reference beam. The main beam continues to the left, while the reference beam goes through a diverging lens (in the white plastic holder) and then a steering mirror which bounces it to one of the large mirrors on the PVC gantry.
The main beam then bounces off another steering mirror, through a second diverging lens, and a second steering mirror to the PVC gantry and then to the diffuser to illuminate the subject.
That steering mirror gets nearly the entire output of the laser, so its a nice dichroic mirror (the original aluminum one got burnt). The beam is large enough after the lens to use a more reasonably priced aluminum mirror.
The illumination diverging lens caused some excitement. Its a meniscus lens, convex on one side, and concave on the other. I had it in backwards, with the concave side facing the laser. The problem was that the reflection off the lens focused to a point, and ionized the air (pulsed lasers eliminate the vibration problem, but you trade for other problems, like spatial filtering is hard). I figured out what was happening from the snapping sound, and eventually found it by taking pictures of the apparatus. Reversing the lens (convex towards the laser) fixed the problem.
There are a couple of unused optics laying around. The cube beam splitter didn't have enough extinction to get the reference beam dim enough. I tried using the dove prism for the wave plate, but unless the prism is perfectly centered the beam doesn't stay coaxial when you rotate it.
There is a continuous frequency doubled YAG on the top right corner of the optics platform. It has its own diverging lens and steering mirror, such that it goes through the illumination beam optics. Its a safe-light modeling light to compose before firing the laser.
This is my attempted entry in the 2015 shmoocon barcodeshmarcode contest. It was unfortunately not readable by the bar-code scanner so it didn't count. However it show the green modeling light, as well as the ruby laser's red light.
I put a piece of foam-core in the plate holder (my usual alignment test article.). The actual plate looks like a plain piece of glass, the emulsion is clear.