Optical measuring system

US6552810B1 · kind B1 · utility

Assignee

• DR. JOHANNES HEIDENHAIN GMBH · DE

Inventors

• Michael Hermann · Tacherting, DE
• Walter Huber · Traunstein, DE
• Wolfgang Holzapfel · Obing, DE
• Volker Hofer · Traunreut, DE

Key dates

• Filing date: Feb 2, 2000
• Grant date: Apr 22, 2003
• Expiry date: Feb 2, 2020

Classification

• Technology area (CPC G): Physics
• CPC primary: G01D5/36
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

An optical position measuring system for determining the relative position of a first object which can be moved with respect to a second object along a measuring direction includes at least one periodic measuring graduation, which is connected to the first object and a scanning unit which is connected with the second object. The scanning unit includes a light source emitting beams of light, at least one scanning graduation and a detector arrangement in a detector plane. The detector arrangement includes several radiation sensitive detector elements for scanning a periodic fringe pattern resulting from the interaction of the beams of light emitted by the light source with the at least one periodic measuring graduation and the at least one scanning graduation, wherein the detector plane is arranged spaced at a distance Zn from the last graduation passed and the distance Zn is calculated from the following equation:1/Zn+1/ZQ=1/((n+&eegr;)*dVTO),wherein:ZQ: is the distance of the last graduation passed from a real and virtual source point of the periodic fringe pattern,n=0, 1, 2, 3, . . . ,&eegr;: is the phase shift in fractions of 360° of the periodic fringe pattern exiting at the…