Optical torque detector

Claim 1

An optical torque detecting apparatus for a rotating shaft of which torsional torque is to be detected, comprising a pair of rotary plates disposed as to face one another connected to the shaft with a predetermined interval between the positions where each is connected to the shaft, each plate having a radial optical grid thereon, so that a Moire fringe pattern may be created in accordance with change of relative turning between the two rotary plates caused by torsion of the shaft, and detecting means for detecting a shift of the Moire fringe pattern between radially outer and inner sections of the optical grids so that the torsional torque of the shaft may be detected thereby; each line of the optical grid formed on one of the two rotary plates being a radially extended straight stepless line, and each line of the optical grid formed on the other of the two rotary plates being a stepped one comprising a radial directional inner half portion and a radial directional outer half portion which are different in phase one from another by 1/4 of the pitch of the optical grid, the detecting means comprising a pair of optical detecting means for detecting respective light rays transmitted through the radial directional outer portion and the radial directional inner portion of the two rotary plates so that the number of times of the shift of the Moire pattern between the foregoing two sections and the direction of the shift thereof may be reliably detected by output signals from the two optical detecting means.