DISPLACEMENT DETECTION DEVICE

PROBLEM TO BE SOLVED: To provide a displacement detection device having excellent stability against a wavelength fluctuation of a light source, and suitable for miniaturization and weight reduction. SOLUTION: This device includes a light emitting/receiving complex unit 12 for separating light emitted from a light emitting element 1 into two lights La1, La2 and emitting the lights, forming two once-diffracted lights Lb1, Lb2 diffracted at optional angles by a diffraction grating 8, and detecting an interference signal formed by allowing returned diffracted lights Ld1, Ld2 to interfere mutually; a moving diffraction grating 11 for detecting displacement; the diffraction grating 8 for irradiating the two lights La1, La2 emitted from the light emitting/receiving complex unit 12 toward the diffraction grating 11, and guiding two twice-diffracted lights Ld1, Ld2 from the diffraction grating 11 to the light emitting/receiving complex unit 12; and a reflection optical system 14 for reflecting two once-diffracted lights Lc1, Lc2 from the diffraction grating 11, and irradiating the lights again toward the diffraction grating 11. COPYRIGHT: (C)2005,JPO&NCIPI