| 摘要 |
PROBLEM TO BE SOLVED: To provide a read/write pickup head for reducing the number of optical elements without losing two characteristic functions of forming a beam in a circular shape and for separating an incidence beam branch and a reflection beam branch. SOLUTION: The pickup head includes a birefringence prism 50 and a 1/4 wavelength plate 70. The birefringence prism 50 is made of a birefringence material with a different refractive index for different polarization and is used to separate the incidence beam and the reflection beam of the pickup head and to form the beam in a circular shape. The polarization of the incidence beam and the reflection beam becomes a right angle by the 1/4 wavelength plate 70. |
