| 摘要 |
PURPOSE:To obtain a simple optical head device where retardation is difficult to occur, by specifying the angle of incidence on the collimator lens side and that on the objective lens side. CONSTITUTION:A collimator lens 2 which receives the light beam emitted from a radiation light source and converts it to approximately parallel beams, an objective lens 4 which converges light beams on a recording carrier, an optical element which is arranged between the collimator lens 2 and the objective lens 4 and has two non-parallel faces, and an optical path where the light beam which is reflected on the recording carrier and is transmitted through the objec tive lens again is reflected on the face on the objective lens side of the optical element and is made incident on a photodetector are provided, and the angle alphaof incidence on the collimator lens side of the optical element and that betaon the objective lens side are set to satisfy 45 deg.<beta<alpha<75 deg.. Thus, the beam shape and the astigmatism are corrected when the light beam is transmitted through one wedge prism 3. Further, retardation is avoided. |
