| 摘要 |
PURPOSE:To accurately focus a laser beam on one prescribed point by providing two cylindrical lenses which can adjust the optical path of the laser beam, respectively only for one side where astigmatic difference is generated in two planes. CONSTITUTION:First cylindrical lenses 4, 4', and 4'' and second cylindrical lenses 5, 5', and 5'' are provided so that they can be moved in a direction perpendicular to the plane formed by respective optical axis and the bus of a cylindrical plane. Those two cylindrical optical devices are the ones to refract only an optical component on one side in two directions where the astigmatic difference exists, respectively, and the optical component on one side is focused by first lenses 3, 3', and 3'', the first cylindrical optical devices 4, 4', and 4'', and a focusing optical device, and the optical component on the other side by the first lenses 3, 3', and 3'', the second cylindrical optical devices 5, 5', and 5'', and the focusing optical device. Therefore, it is possible to eliminate dispersion in the focusing position in one beam due to the astigmatic difference. In such a case, it is possible to adjust an optical path automatically by providing a position detecting means 13a, moving means 12, 12', and 12'' for the second cylindrical optical devices, and a control means. |
