| US 7,485,845 B2 | ||
| Photoelectric encoder capable of effectively removing harmonic components | ||
| Toru Yaku, Kawasaki (Japan); and Tetsuro Kiriyama, Kawasaki (Japan) | ||
| Assigned to Mitutoyo Corporation, Kawasaki-shi (Japan) | ||
| Filed on Dec. 04, 2006, as Appl. No. 11/566,433. | ||
| Claims priority of application No. 2005-352397 (JP), filed on Dec. 06, 2005. | ||
| Prior Publication US 2007/0125939 A1, Jun. 07, 2007 | ||
| Int. Cl. G01D 5/34 (2006.01) | ||
| U.S. Cl. 250—231.13 [250/231.16; 250/237 G; 356/616] | 12 Claims |
| 1. A three-grating type photoelectric encoder comprising:
a light source for outputting light;
a first grating, disposed to directly receive the outputted light from the light source;
a second grating disposed to reflect the outputted light after the outputted light passes through said first grating;
a third grating, disposed to receive the outputted light reflected from said second grating, and
a detector, wherein
the second grating is formed on a scale and the first and third gratings are disposed on a side of the detector, wherein
a part of at least the first grating is shifted in a direction of a measurement axis by P/(2n) (wherein P is a grating pitch,
n is the order of a harmonic component to be removed) in order to remove a harmonic component of the nth order.
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