| 摘要 |
PURPOSE:To obtain the best photo detection output and also to carry out focus servo operation with no malfunction by arranging a cylindrical lens and photo detecting element with the distance between the both set adequately. CONSTITUTION:The stop radius of condenser lens 5 and the distance between lens 5 and principal point 20 of cylindrical lens 8 are represented by R and L respectively, and the distance between conjugate point 40 of recording surface 7 to lens 5 and principal point 20 of cylindrical lens 8, the distance between the principal point of cylindrical lens 8 and photo detecting element 9, and the focal distance of the cylindrical surface of cylindrical lens 8 are by Z, D and F. Lengths X and Y of the photo detection shape crossing at right angles on the phoho detection surface of photo detecting element 9 are expressed by equations 1 and 2. length Y is measured in parallel to the generating line of cylindrical lens 8, and X is perpendicular to this generating line. Here, cylindrical lens 8 and photo detecting element 9 are arranged with D greater than F. Setting D to 2F, especially, makes the best servo operation possible. |
