Abstract: An optical pick-up device includes a semi-conductor laser as a laser light-emitting device, a collimator lens, a directional control mirror, an objective lens, a light amount detecting device, a reflecting mirror that reflects leakage light of the laser light onto the light amount detecting device, and a light amount adjusting member that adjusts the amount of light incident on the light amount detecting device, provided between the light amount detecting device and the reflecting mirror. The light amount adjusting member may include a rotatably or slidably-supported baffle of which a rotational angle or slide position is changed so as to adjust the amount of the light.

Abstract: An optical pick-up device includes a semi-conductor laser as a laser light-emitting device, a collimator lens, a directional control mirror, an objective lens, a light amount detecting device, a reflecting mirror that reflects leakage light of the laser light onto the light amount detecting device, and a light amount adjusting member that adjusts the amount of light incident on the light amount detecting device, provided between the light amount detecting device and the reflecting mirror. The light amount adjusting member may include a rotatably or slidably-supported baffle of which a rotational angle or slide position is changed so as to adjust the amount of the light.

Abstract: An apparatus for applying a magnetic field has a permanent magnet, pivotally supported, which has an approximate cylindrical shape, respective semicircles of a circular section thereof being magnetized as N and S poles, and a driving coil, located in the vicinity of the permanent magnet so that the permanent magnet can partially penetrate inside the loops of the driving coil, the rotation and the positioning of the permanent magnet being controlled by the strength and/or directions of current flow in the driving coil. The apparatus is used for a magneto-optical disk storage. Since the driving coil is close to the permanent magnet, the pivoting of the permanent magnet can be controlled with a fast response. In addition, the apparatus can be made relatively small.