| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optimum regenerative signal by regulating the inclination of a first wavelength plate and diffraction grating to a stable phase difference. SOLUTION: The transmitted luminous flux of the first wavelength plate 7a is separated into zero order light and ±1st order light by the diffraction grating 6. The zero order light is made incident perpendicularly on a second wavelength plate 7b and the phase difference determined by the thickness of the second wavelength plate 7b is given. On the other hand, the ±1st order light is made incident diagonally on the second wavelength plate 7b at an angle determined by a grating pitch of the diffraction grating 6 and is made incident on the second wavelength plate 7b as if the second wavelength plate 7b rotates clockwise or counterclockwise with respect to the crystal optical axis. Consequently, the ±1st order light is long in the pass optical distance of the second wavelength plate 7b and is capable of increasing the phase difference without affecting the rate of ordinary rays and abnormal rays. The respective luminous fluxes past the second wavelength plate 7b are subjected to polarization detection by a Wollaston prism 8 and are further separated to P and S components and are then subjected to photoelectric conversion by a photodetector 10 via a converging lens 9. |
