Optical disk unit

#1. Field of the Invention

#This invention relates to an optical disk unit which reads information from a recording medium, such as an optical disk and a opto-magnetic disk, or reads and writes information relative to such a recording medium.

#2. Description of Related Art

#FIG. 1 is a plan view of a first embodiment of an optical disk unit of the present invention;

#FIG. 2 is a perspective view of the optical disk of the first embodiment;

#FIG. 3 is an exploded perspective view of the optical disk unit of the first embodiment;

#First Embodiment

#A first embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a plan view of the first embodiment of an optical disk unit of the present invention, FIG. 2 is a perspective view of the optical disk unit of the first embodiment, FIG. 3 is an exploded perspective view of the optical disk unit of the first embodiment, and Figs. 4, 5, 6, 7 and 8 are cross-sectional views taken along the lines IV--IV, V--V, VI--VI, VII--VII and VIII--VIII of FIG. 1, respectively. In FIGS. 1, 2 and 3, reference numeral 21a denotes a bobbin. A laser unit 20 for emitting and detecting a laser beam as shown in FIG. 4, an objective lens 22 for converging the laser beam onto an optical disk 1, and a pair of reflecting mirrors 23 (FIG. 4) for directing the laser beam, emitted from the laser unit 20, to the objective lens 22, are mounted on the bobbin 21a. Even if only one or none of the reflecting mirrors 23 is provided, a layout of the laser unit 20 and the objective lens 22 is possible. Two guide shafts 25 are mounted on a carriage base 24, and extend in a direction radially of the optical disk 1. Actuator magnets 26 for moving the bobbin 21a are mounted on the carriage base 24 in parallel relation to the guide shafts 25. A back yoke 27 made of a ferromagnetic material is fixedly secured to each of the actuator magnets 26 in contiguous relation thereto. In this embodiment, the guide shafts 25 are made of a ferromagnetic material, and with this construction, the guide shaft 25, the actuator magnet 26 and the back yoke 27 constitute a magnetic circuit. Focusing coils 28a for moving the bobbin 21a in a focusing direction (direction of an arrow C) are fixedly mounted on the bobbin 21a in opposed relation to the actuator magnets 26, as shown in FIG. 5. Tracking and feed coils 29a for moving the bobbin 21a in a tracking/feed direction (direction of an arrow D) are fixedly mounted on the bobbin 21a, and are disposed in opposed relation to the actuator magnets 26, respectively, as shown in FIG. 6, the guide shafts 25 passing through the tracking and feed coils 29a, respectively. Main shaft sliders 30 and guide sliders 31 are supported on the guide shafts 25, respectively. As shown in FIG. 7, the main shaft sliders 30 are slidable along one guide shaft 25, and the guide sliders 31 are slidable along the other guide shaft 25, and are movable along the surface of the optical disk 1 in a direction perpendicular to the axis of this guide shaft 25. Suspension springs 32a are fixedly secured to the bobbin 21a and the main shaft sliders 30 and the guide sliders 31, as shown in FIG. 7, and the bobbin 21a is resiliently supported by these suspension springs 32a for movement in the focusing direction (direction of the arrow C (FIG. 2)). A signal flexible cable 33 for transferring an electrical signal between a control board for controlling the disk unit and the laser unit 20 is connected to the laser unit 20, and is fixed to the carriage base 24. An actuator flexible cable 34 for transferring signals from the control panel to the focusing coils 28a and the tracking and feed coils 29a is connected to the focusing coils 28a and the tracking and feed coils 29a, and is fixed to the carriage base 24. As shown in FIG. 8, a spindle motor portion for rotating the optical disk 1 comprises a bearing 35 mounted on the carriage base 24, a spindle coil 36 provided around the bearing 35, a spindle shaft 37 rotatably supported by the bearing 35, a turntable 38 fixedly mounted on the spindle shaft 37 for supporting the optical disk 1, and a spindle magnet 39 mounted on the turntable 38 in opposed relation to the spindle coil 36.

#The operation of the optical disk unit of the above construction will now be described. First, a laser beam, emitted from a semiconductor laser provided at the laser unit 20, is reflected by the pair of reflecting mirrors 23, and is fed to the objective lens 22, as shown in FIG. 4. The laser beam is converged or decreased in diameter by the objective lens 22 so that data can be read from the optical disk 1. Reflection light from the optical disk 1 passes through the objective lens 22, and is reflected by the reflecting mirrors 23 to a photo detector provided at the laser unit 20, and is outputted as an electrical signal.