Patent ID: 7301140

Claim:
A position measuring device comprising: a scale graduation that is a cross-grid graduation and comprises a first reference marking and a second reference marking; a scanning device for scanning said scale graduation for detecting relative movements of said scanning device with respect to said scale graduation, said scanning device comprising: a first primary sensor field and a second primary sensor field used for detecting relative movements along a first spatial direction; a first secondary sensor field and a second secondary sensor field for detecting relative movements along a second spatial direction, which is linearly independent of said first spatial direction, wherein said first primary sensor field, said second primary sensor field, said first secondary sensor field and said second secondary sensor field are arranged point-symmetrically in relation to a mid-point in a plane a first sensor module assigned to said first and second primary sensor fields for scanning said first reference marking of said scale graduation and generating a first defined output signal from said first reference marking when said scale graduation and said scanning device are in a defined position with respect to each other; a second sensor module assigned to said first and second secondary sensor fields for scanning said second reference marking of said scale graduation and generating a second defined output signal from said second reference marking when said scale graduation and said scanning device are in said defined position with respect to each other; and wherein said first sensor module, said first primary sensor field and said second primary sensor field are each arranged on a first common straight line; and said second sensor module, said first secondary sensor field and said second secondary sensor field are each arranged on a second common straight line.