| 摘要 |
PROBLEM TO BE SOLVED: To improve resolution and to prevent deterioration of an S/N ratio by obtaining an encode having an optical pulse plate and an optical device adequately using the encoder. SOLUTION: A light beam from a light source 1a passes through a polarization beam splitter 2 and a 1/4 wavelength plate 3 to become a circular polarization and to illuminate a circumference of an optical axis A on a pulse plate 4. A reflection light reflected by a refection section 4a of the pulse plate 4 passes through the 1/4 wavelength plate 3 to become an S polarization and to be totally reflected by the polarization beam splitter 2 and it is imaged on the pulse plate 4 as an inverted image by virtue of a lens 5 and a mirror 6. When the image portion is a non-reflection section, it is detected that the portion is a dark one by a light receiving section 1b. Conversely, when it is imaged on the refection section 4a, it is reflected thereby to become the circular polarization passing through the 1/4 wavelength plate 3 to become a P polarization. It totally passes through the polarization beam splitter 2 and is detected by the light receiving section 1b as a bright condition to be converted to an electric signal. |
