| 摘要 |
PROBLEM TO BE SOLVED: To noncontactly determine the moving direction of a moving object. SOLUTION: A beam L1 emitted from an interfering light source 11 brought into a substantially parallel beam L2 by a lens 12, gets incident into a polarization beam splitter 13, and passes through aλ/4 wavelength plate 14 to be emitted to the moving object S. A beam L3 is emitted to the moving object S and brought thereafter into scattered light L4. One portion of a circular polarized light L4' out of it returns back through the optical path same to the irradiation direction toward aλ/4 wavelength plate 14, is reflected by the polarization beam splitter 13 to be get incident into a beam splitter 15, and is split into scattered lights L5a, L5b on a light splitting face. The scattered light L5a is transmitted through a slit grating 16a having a period of pitch p and effecting a role a spatial filter to get incident into a photoreceiving element 17a, and the scattered light L5b is transmitted through similar slit grating 16b to get incident into a photoreceiving element 17b. The moving direction is informed by determining an advancing condition of a phase, because an obtained photoelectric signal is shifted by 1/4 of period by shifting the slit gratings 16a, 16b by (1/4)p along the moving direction, so as to generate alternating current signals A, B having V/p of frequency to a moving speed V. COPYRIGHT: (C)2004,JPO&NCIPI
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