| 摘要 |
PURPOSE:To suppress the generation of the comaabberation of the light spot to a little when a skew is generated by setting an N, A, value in a first diameter direction of an objective lens smaller than the N, A, value in a second diameter direction of the objective lens. CONSTITUTION:Constitution is executed so that the N, A, value (Numerical Aperture) of an objective lens 1 in the first diameter direction in accordance with the vertical direction of the signal track of an light beam radiated onto a signal recording medium is smaller than the N, A, value of the objective lens 1 in the second diameter direction in accordance with the jitter direction of the signal track perpendicular to the first diameter direction. Concretely, one whose N, A, value is 0.53 is used, in the second diameter direction, this N, a, value is left as it is and in the first diameter direction, the N, A, value is made about 0.45 by a limit piece 2a of a lens holder 2. Thus, when the skew is generated, the generation of the comaabberation of the light spot can be suppressed to a little. |
