Patent ID: 6151128
Filing Date: 2000-11-21
Classification: G01D

Abstract:
An optical position measuring system for detecting the relative position of a first object and a second object which are movable in respect to each other, comprising:a scale graduation with a graduation period, TP, and connected with a first object;a scanning unit connected to a second object that moves relative to the first object, so that there is a displacement between the scale graduation and the scanning unit, wherein the scanning unit comprises a scanning plate that comprises a first scanning field and a second scanning field that are arranged offset from each other in a measuring direction (x) by a defined distance, D, so that definitely phase-shifted partial signals, which are modulated as a function of the displacement can be associated with the first and second scanning fields;a first deflection element associated with the first scanning field;a second deflection element associated with the second scanning field, wherein the first and second deflection elements spatially separate the phase-shifted partial signals from the first and second scanning fields;a first detector element placed downstream of the scanning plate and associated with the first scanning field;a second detector element placed downstream of the scanning plate and associated with the first scanning field, wherein the first detector element and the second detector element detect the spatially separated phase-shifted partial signals in different spatial directions;a third detector element placed downstream of the scanning plate and associated with the second scanning field;a fourth detector element placed downstream of the scanning plate and associated with the second scanning field, wherein the third detector element and the fourth detector element detect the spatially separated phase-shifted partial signals in different spatial directions; andwherein the first, second, third and fourth detector elements are wired together so that two output signals, which are phase-shifted by 90.degree. relative to one another, are generated at an output side of the optical position measuring system; andwherein the first and second scanning fields are arranged on the scanning plate so that the offset distance D=TP/2*(N+1/4), wherein N=0, 1, 2, . . . .