| 摘要 |
PURPOSE:To reduce a crosstalk noise and to reduce an error occurrence rate in a signal component frequency multiplexed on a low band of a video signal by forming a beam spot converged on a disk in an elliptic shape and making the major axis direction coincide with a linear velocity direction. CONSTITUTION:A direction parallel to a polarization direction is made to coincide with the linear velocity direction (pit arrangement direction) of the disk D by turning and arranging a semiconductor laser 1 around a beam by 90 deg.. At this time, the length in the major direction of the ellipse is about 1.07mum, and the length in the minor direction is about 0.95mum. In such a case, when the length in the linear velocity direction is set to the same extent of length as the conventional extent of length, since the beam spot is converged more sufficiently since a wavelength is short as 630(nm), a numerical aperture NA of a collimate lens 2 is enlarged more than the conventional NA, and the utilization efficiency in the laser is improved. |
