| 摘要 |
PURPOSE:To make the number times of generation of track offset small to a degree where practically no problem exists by providing the principal point of a luminous flux polarization lens and the focus of an objective lens on the light incident side when a movable optical system is in the middle position of the movable range on the fixed optical system of the body of a relay lens arranged in a couple. CONSTITUTION:A luminous flux polarization lens 11 is held so that it is movable in one direction orthogonal to the optical axis from a beam splitter 2 for tracking. A relay lens 12 is arranged on the optical path between the luminous flux polarization lens and an objective lens 6, and the image of the principal point position M of the luminous flux polarization lens 11 is formed at the luminous flux incident side focus position F of the objective lens 6 when a movable optical system A is in a middle position of the movable range. At this middle position, the shift of the luminous flux position which is incident to the objective lens 6 is not generated even when the luminous flux polarization lens 11 moves for tracking, and the track off-set is not generated. Outside of this middle position, the shift of the luminous flux incident position is a generated, and the off-set generation can be made small as a whole. Thus, the number of times of generation of track off-set becomes small to a degree where no practical problem exists. |
