The present invention relates to a pickup actuator, and particularly to a pickup actuator having an improved magnetic circuit design which enables the sliding mechanisms to be made light in weight.
Disk players such as video disk and CD players employ optical pickups for reading out information stored on an optically encoded disk. The pickup is provided with a magnetic circuit which is made capable of finely driving an objective lens along a focal axis for focusing, and in the direction of the encoded information (pits) for tracking. A carriage mechanism for driving the pickup for moving the same in the radial direction of the disk is also provided.
The carriage mechanism is provided with magnetic circuits together with a guide rail which guide the pickup along its stroke. The number of magnetic circuits is three or more in all, together with the magnetic circuit provided in the pickup. The magnetic circuits in the past have been made large and long, making the carriage mechanism overly long and heavy.
An example of a conventional device is shown in FIG. 5. In this device, the pickup 1 is integrated with a frame 3, which forms a linear motor, via a stay 2. Yoke plates 4 constituting a magnetic circuit pass through openings provided in the frame 3. The frame 3 is disposed in an air gap 6 formed by magnets 5, and is movably supported by a guide bar 7 for linear movement.
The pickup apparatus of the conventional type includes 3 independent magnetic circuits. The magnetic circuits of the carriage mechanism are so long that the total weight is made quite heavy. The power supply system for driving the coils is extremely complicated and requires a large driving current.