| 摘要 |
PROBLEM TO BE SOLVED: To provide a wavelength plate suitable for the optical pickup device having an excellent jitter characteristic by suppressing fluctuation in a return light receiving quantity by a photodetector and also maintaining the light receiving quantity at a constant level. SOLUTION: 1st and 2nd phase difference regions A and B are formed in a prescribed pattern in a light transmitting surface 201 of a substrate 2 in the wavelength plate 1. In the 1st phase difference region A, the direction Ha of a crystal optical axis is set to make an angle of π/3 with a polarization declination Ho of incident light. Meanwhile, in the 2nd phase difference region B, the direction Hb of the crystal optical axis is set in parallel to the polarization orientation Ho of the incident light. Consequently, when the wavelength plate 1 is used in the optical pickup device, the return light receiving quantity in the photodetector can be kept constant or fluctuating width of this light receiving quantity can be diminished by adjusting the directions of the crystal axes of the 1st and 2nd phase difference regions A and B. Consequently, the optical pickup device having excellent jitter characteristic without being influenced by double refractivity of an optical recording medium is realized by using the wavelength plate 1. |
