| 摘要 |
PROBLEM TO BE SOLVED: To provide a condensing optical system capable of relatively simply forming a micro spot. SOLUTION: The intensive filter 2 in which transmissivity is gradually increased as the U axial direction is left from the center of the optical axis is disposed between a laser beam source 1 and an objective lens 3. The intensive filter 2 is arranged so that the narrow direction of the radiating angle of the laser beam emitted from the laser beam source 1 coincides with the U axis. In the laser beam transmitting the intensive filter 2, the difference of optical intensity between the vicinity of the center of the optical axis and both end parts is reduced, the distribution of the radiating angle being enlarged is obtained, and the distribution of intensity near the radiating angle in the V axial direction orthogonal to the U axial direction is formed. Thus, the distribution of intensity in the aperture of the objective lens 3 is equalized in both directions, and a nearly circular micro spot is easily formed by correcting asymmetry of the radiating angle of a semiconductor laser without changing the distance and the arrangement of the objective lens 3 and the laser beam source 1.
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