| 摘要 |
PURPOSE:To improve the performance of the optical pickup by an inexpensive device by arranging a parallel flat plate between a semiconductor laser and a collimator lens slantingly to the optical axis. CONSTITUTION:The parallel flat plate 4 is arranged between the semiconductor laser 1 and collimator lens 3 slantingly to the optical axis. When the laser 1 is seen in directions (a) and (b), light beams emitted at positions O1 and O2 travel as if they were emitted at positions O1' and O2' through the operation of the flat plate 4. At this time, the positions O1 and O1', and O2 and O2' are difference and the differences are varied optionally according to the thickness and inclination of the flat plate 4, so the positions O1' is made coincident with the position O2' to compensate astigmatism. Thus, no expensive cylindrical lens is used, so the cost is reduced and the overall aberrations are reduced. |
