Patent ID: 7271920

Claim:
A position-measuring device, comprising: a measuring graduation arranged around a material measure arranged in a ring shape; and a scanning unit configured to optically scan the measuring graduation by electromagnetic radiation, the scanning unit including: a scanning plate including a periodic scanning graduation arranged in a beam path of the electromagnetic radiation and arranged so that the electromagnetic radiation interacts with the scanning graduation and the measuring graduation; and a detector including a detector surface configured to detect the electromagnetic radiation after interaction with the scanning graduation and the measuring graduation in a stripe pattern with a period; wherein the following condition is satisfied: 1/(1 /P A −1 /P M ) <P D ; P M representing a period of the measuring graduation, P A representing a period of the scanning graduation, and P D representing the period of the stripe pattern; wherein the period of the measuring graduation satisfies the condition: P M >1/(1/P A −1/P D ); and wherein a deviation of the period of the measuring graduation from a value of 1/(1/P A −1/P D ) is between 0.1% and 1%.