| US 7,601,947 B2 | ||
| Encoder that optically detects positional information of a scale | ||
| Susumu Makinouchi, Zama (Japan); Toru Imai, Natori (Japan); and Akihiro Watanabe, Sendai (Japan) | ||
| Assigned to Nikon Corporation, Tokyo (Japan) | ||
| Filed on May 11, 2007, as Appl. No. 11/798,255. | ||
| Claims priority of provisional application 60/808541, filed on May 26, 2006. | ||
| Claims priority of application No. 2006-139658 (JP), filed on May 19, 2006; and application No. 2007-020632 (JP), filed on Jan. 31, 2007. | ||
| Prior Publication US 2007/0267571 A1, Nov. 22, 2007 | ||
| Int. Cl. G01B 9/02 (2006.01) | ||
| U.S. Cl. 250—231.13 [250/231.18; 250/237 G] | 9 Claims |
| 1. An encoder, comprising:
a first optical member on which an illumination light is incident and where a first light and a second light are generated;
a change unit that periodically changes an incident angle of the illumination light with respect to the first optical member;
and
a second optical member that is relatively displaced with respect to the first optical member,
the change unit and the first and second optical members being configured such that
under a condition that the first light and the second light are generated from different positions of the first optical member,
the first light and the second light are made to be incident on a same position of the second optical member and to interfere
with each other, or
under a condition that the first light and the second light are generated from a same position of the first optical member,
the first light and the second light are made to be incident on different positions of the second optical member and to interfere
with each other.
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