JPS6459110A - Angle of rotation measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the measuring of relative and absolute angles of rotation with high resolutions, by detecting a phase difference between an output signal from an optical type fine vibration sensor and an excitation signal for exciting a surface wave transducer. CONSTITUTION:A rotor 1 with a fixed radius rotates together with a rotating object to generate an elastic surface wave propagation path 2 in an internal wall thereof 1. A surface wave transducer 3 is fixed on the propagation path 2. A signal generation circuit 4 generates an excitation signal to be sent to the transducer 3 through an amplification circuit 5. The elastic surface wave generated is propagated along the surface of the propagation path 2. An optical type micro-oscillation sensor body 6 is fixed statically on the rotor 1 and a probe laser light beam 7 always irradiates the surface of the propagation path 2 through a condenser lens 8. A phase difference detection circuit 10 receives a reference signal 11 from the circuit 4 to detect a phase difference between the reference signal and a displacement signal S picked up with the sensor 6 and a central processing section 12 can calculate a relative angle of rotation and an absolute angle of rotation with high resolutions.