| 摘要 |
PURPOSE:To suppress the offset occurring to a tracking error signal by partly varying the reflection factor and the transmission factor on the surface of a 1/4 wavelength plate attached to a beam splitting prism. CONSTITUTION:A 1/4 wavelength plate 21 is adhered to a beam splitting prism 3, and a mirror coating 100 is applied to the emission surface of the plate 21 so as to partly change the transmission and reflection factors. That is, the coating 100 is applied so that a surface 31 of 100% transmission factor is formed in the reflected light intensity pattern areas 51 and 52 where the pattern intensity change due to the shift of a reflected light intensity pattern 50 is decreased. Then only the beams of both areas 51 and 52 where the intensity change due to the shift of the pattern 50 is reduced are made incident on the bisected tracking error detectors 12a and 12b. Thus it is possible to obtain an optical head where the offset occurring to the tracking error signal is reduced. |
