| 摘要 |
PROBLEM TO BE SOLVED: To obtain a phase plate for two wavelengths which turns the polarization direction of linearly polarized light of 660 nm wavelength band by 45 deg. and converts linearly polarized light of 790 nm wavelength band to circularly polarized light and to obtain an optical head device which ensures a low jitter value of a reproduced signal by using the phase plate. SOLUTION: The phase plate 101 is obtained by overlapping and fixing two birefringent organic thin films 13A, 13B on transparent substrates 11, 14 in such a way that their optical axes cross at 24 deg. angle, the organic thin film 13A has 593 nm retardation value and the organic thin film 13B has 395 nm retardation value. The phase plate 101 is disposed in the light path between the collimator lens and objective of an optical head device. |
