JPS6459109A - Moving position measuring apparatus for moving object - Google Patents

Abstract

PURPOSE:To enable highly accurate measurement of relative and absolute movement positions, 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:An elastic surface wave propagation path 2 is bonded securely on a uniaxial moving object 1 and a surface wave transducer 3 is fixed at one dn of 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. An elastic surface wave generated is propagated along the surface of the propagation path 2. An optical micro-oscillation sensor body 6 is fixed independently of the moving object 1 and a probe laser beam 7 is always made to irradiate the surface of the propagation path 2 passing 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 11 and a displacement signal S picked up wit the sensor 6, thereby enabling a central processing section 12 to calculate relative and absolute movement positions at a high accuracy.