LASER DISTANCE MEASUREMENT

摘要

Laser distance measuring apparatus has an internal reference beam length determined by a retro-reflector which is movable into and out of the beam path. The retro-reflector is opaque relying on specular reflection. This, together with a light trap arrangement, reduces spurious reflections. The laser and detection optics are carried on a shock proof sub-chassis but the retro-reflector is fixed to the housing to retain alignment with an exterior datum. Each distance measurement is sandwiched between reference measurements to maintain accuracy despite drift in the circuitry.