Patent ID: 9689665
Date: 2017-06-27
CPC Classifications: B82Y,G01B,G03F

Claim:
1. A position detection apparatus that illuminates diffraction gratings formed on two objects with light from a light source and receives diffracted light from the diffraction gratings to acquire relative positions of the two objects, the position detection apparatus comprising: an optical system configured to cause plus n-th order diffracted light and minus n-th order diffracted light from each of the diffraction gratings to interfere with each other, where n is a natural number; a light receiving unit; and a processing unit, wherein the optical system is configured to cause the plus n-th order diffracted light and the minus n-th order diffracted light from the diffraction gratings incident on the light receiving unit at different angles; wherein the light receiving unit receives an interference fringe of the plus n-th order diffracted light and the minus n-th order diffracted light from each of the diffraction gratings formed on the two objects, and frequency of the plus n-th order diffracted light and frequency of the minus n-th order diffracted light are the same, and wherein the processing unit acquires the relative positions of the two objects by using a phase difference between the interference fringes at an area where interference fringes of the diffracted light from the respective diffraction gratings do not overlap each other among the interference fringes of the diffracted light from each of the diffraction gratings formed on the two objects, received by the light receiving unit.