Accurate length change measurement by laser beam timing - uses polygonal rotating mirror array to split pulsed beam into reflected and reference beams

摘要

Appts. measuring changes in length in test pieces structures or surfaces uses a laser beam timing technique. This gives accurate results for a wide range of applications down to test pieces of under 1mm in length. The laser beam is focused and transformed into a pulsed sequence by a polygonal rotating array of mirrors. The pulsed beam is split into two beams, one of which is reflected from a surface on the object to be measured, then detected by a photosensitive detector. The other, which is a reference beam, is directly detected by a photosensitive detectors. The two detector output signals are processed by a substraction integrating and division processing network to produce the measurement required.