| 摘要 |
PURPOSE:To positively identify reflected light from a targeted or non-targeted reflective object by providing a means for detecting polarized reflected light from the target reflected object and a means for detecting polarized light which is different from the reflected light. CONSTITUTION:A linearly polarized light beam emitted from a laser light source 17 is changed to circularly polarized light beam by lambda/4 birefringence member 24 and is applied to a reflection part 100, where it is changed to a circularly polarized light beam in reverse rotation and is reflected, is returned to a linearly polarized light beam by the member 24 again, and is transmitted through a polarized beam splitter (for transmitting polarized compact within a surface including the optical axis 18 and the reflection optical axis 34) 36 and then is applied to a first photodetector 40. The reflected light beam from a part other than the reflective part 100 is a circularly polarized light beam in the same direction as that of incidence circularly polarized beam, is converted into a linearly polarized beam with a polarization surface crossing the linearly polarized beam emitted from a light source 17 by the member 24 so that it is reflected by the splitter 36 and is applied to a second photodetector 42. A control part 44 calculates the difference between output peaks of the detectors 40 and 42 and judges that the object is not a target reflective object if the difference is equal to or less than a specific value.
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