| 摘要 |
PROBLEM TO BE SOLVED: To facilitate an optical axis alingment by providing a condenser lens having a light converging point in the vicinity of a light-emitting surface and enabling the position of the light converging point to be known physically and visually. SOLUTION: A condenser lens 15 has the light converging point in the vicinity of the light-emitting surface of the lens and a pinhole 16 is provided on the light-emitting point. When a laser beam is made incident on a beam splitter 5, it is condensed with the condenser lens 15 to pass through the pinhole 16. At this time, the laser beam at the light converging point is in a conjugate relation with a laser spot on a disk surface and only a main spot is made to be transmitted by shielding the reflected light of a side spot by the pinhole 16 while utilizing this characteristic. Thus, the optical axis alignment is facilitated by allowing the light converging point of the condenser lens 15 to be in the vicinity of the light-emitting surface of the reflected light made incident on the lens 15 and also by integrally providing the pinhole 16 on the light- emitting surface and an optical axis deviation is prevented from occurring even when a secular change and an environmental change are generated. |
