A couple of steps forward (I hope) this evening.
First, I built a better rotation grid, I had a few thou out on my printed version and although it ran perfectly, I wasn't 100% happy with it.
This one works perfectly.. and the runout is better than my ability to measure !
The process might be useful to others.... !
3mm Acrylic, matted off with 600 wet and dry, sprayed with matt black paint
extra thickness glued to the back where it needs to fit the nozzle fitting on the head (I don't have any 6mm acrylic !)
The white dots were laser ablated, leaving the white matt of the acrylic.
the disc was laser cut and finally, the hole chamfered to protect the "O" rings.
I could have used this method for the main head grid, it would give a cracking result, but my laser is nowhere near large enough
Second, I started building a rig to test my hypothesis regarding the camera and reverse.
I started looking at fitting a composite video camera to the rotating part of the head
The gap between the camera and the test grid is quite limited, and the only useable image I got from any of the composite video cameras I have was from a pinhole board camera. It fits nicely in the gap and can be mounted using a similar mount to my rotation grid.
Its not yet mounted to the head, but connected to the digitiser through the Fiducial connection it images and finds the centers of the grid dots OK... I picked up the power from the upward facing camera power plug as it was convenient.
It has the same number and orientation Red LEDs for illumination as the fid cam.
Work is now getting in the way and I probably won't get back to this for a few days.
ps, yes I know the camera is old fashioned ! its been in a drawer for 20 years !
