Method of and apparatus for measuring small gaps.

摘要

A method of measuring a small gap, in particular the clearance gap between the lobes of the rotors of a screw compressor, comprises directing light (39) through the gap (65) and measuring (41) the amount of paraxial light passing through the gap, the gap width being related to the measured amount of light. The apparatus disclosed directs the light at the pitch line helix angle into the rotor clearance gap and measures the paraxial light by means of an area scan camera.