US 9,810,521 B2
Displacement detection apparatus
Akinori Suzuki, Isehara (JP); Masayuki Niiya, Isehara (JP); Kenji Matsushita, Isehara (JP); Terukazu Nishida, Isehara (JP); Hideaki Tamiya, Isehara (JP); and Kayoko Taniguchi, Isehara (JP)
Assigned to DMG MORI SEIKI CO., LTD., Yamato-Koriyama (JP)
Filed by DMG MORI SEIKI CO., LTD., Yamato-Koriyama, Nara (JP)
Filed on Jan. 27, 2016, as Appl. No. 15/8,086.
Claims priority of application No. 2015-016553 (JP), filed on Jan. 30, 2015.
Prior Publication US 2016/0223317 A1, Aug. 4, 2016
Int. Cl. G01B 11/00 (2006.01); G01B 9/02 (2006.01); G01D 5/38 (2006.01)
CPC G01B 11/002 (2013.01) [G01B 9/0209 (2013.01); G01D 5/38 (2013.01)] 5 Claims
OG exemplary drawing
 
1. A displacement detection apparatus, comprising:
a low-coherence laser light source that has a resonator, emits light and has a plurality of oscillation spectra associated with a resonator length Lcav of the resonator;
a lens that condenses the light from the laser light source;
a polarization maintaining fiber that transmits the light condensed by the lens, the polarization maintaining fiber having a length selected so as to avoid interference between a beam via an X polarization mode axis and a beam via a Y polarization mode axis, by being not equal to 2m×neff×Lcav×Lbeat/λ, where:
m is a positive integer,
neff is a refractive index of the resonator,
Lcav is the resonator length,
Lbeat is a beat length obtained from a difference between propagation constants of two polarization modes, and
λ is a wavelength of the light source; and
a displacement detector that divides a beam transmitted by the polarization maintaining fiber into two beams and converts the respective beams to an interference signal by causing the respective beams to interfere with each other, in order to set a variation of a phase applied to each of the divided beams to an amount of displacement.