Found a paper of the TRIUMF E614  experiment : "Quality control during mass production of wire chambers",
were they mention some details about the wire scanner (see attachment for the full paper):

"Each glass ruler is observed by CCD camera with attached zoom
lenses and images of wire and grooves are controlled on monitors. 
...
Typical magnification is about of 250 and it allows us to control and 
correct position of each wire in the grooves during wiring and before fixing 
of all wires with epoxy glue on the PCB.
...
The travelling microscope consists of two CCD cameras with zoom lenses mounted on
a precision linear bearing and rail, and attached to a digital readout system Acurite. Each
camera has it’s own monitor. One camera points down at the wires and measure X position
of each wire directly. The other camera points at 45 degree angle and difference between two
measurements provides Z position. The rail and bearing is a ultra-precision grade THK rail
with overall straightness tolerance of ±2 µm over the lenght of the rail. The digital readout
is an Acurite glass scale with a resolution of 1 µm and accuracy of ±2 µm over all."