| 摘要 |
PURPOSE:To miniaturize the titled pickup and to attain ease of adjustment of the member by arranging the 2nd 1/4 wavelength plate and a transparent base provided partly with a full reflection film before or after a condenser lens on an optical axis and arranging respectively a photodetector between polarized beam splitters. CONSTITUTION:A reflected light of a disc 6 passes through an objective lens 5 and the 1st 1/4 wavelength plate 4, is reflected in the polarized beam splitter 3 and incident to a condenser lens 7. Then the light is made incident to the 2nd 1/4 wavelength plate 12 and a transparent base 13, a part reaches a photodetector 8 and it is detected as a tracking error signal, the other part is reflected in a reflecting film 13a and returns to the polarized beam splitter 3. Since the reflected light is subject to polarization two times at the 1/4 wavelength plate 12, the light transmits through the polarized beam splitter 3, incident to a photodetector 10 and detected as a focus error signal. The optical path length up to the photodetector is overlapped by the reflecting means while satisfying the image forming conditions to earn the optical path length so as to miniaturize the space. |
