1. Field of the Invention
The present invention relates to an optical pickup actuator for reading and writing data from and to an optical recording medium.
2. Description of the Related Art
The optical pickup actuator maintains a relative location between an object lens and an optical recording medium at a predetermined distance by moving a moving part on which the object lens is mounted and reads and writes information from and to the optical recording medium by following a track of the optical recording medium.
The optical pickup actuator has a permanent magnet and a coil. When the electric current is applied to the coil, the optical pickup actuator moves the object lens to a desired location. At this point, the moving part moves in focusing and tracking directions that are perpendicular to each other.
FIGS. 1A and 1B are schematic views of an optical pickup actuator according to the related art.
Referring to FIGS. 1A and 1B, an optical pickup actuator includes a lens holder 102 for mounting an object lens on a central portion thereof and having an outer circumference around which tracking and focusing coils 106 and 105 are wound, magnets and yokes 103 and 104 installed on the base and opposing the tracking and focusing coils 106 and 105 of the lens holder 102, a plurality of wire suspensions 107 each having a first end fixed on a side surface of the lens holder to support the lens holder 102, and a damper holder 109 to which a second end of each wire suspensions 107 is fixed.
Reference numeral 109 denotes fixing plates fixed on the lens holder 102 and the first ends of the wire suspensions 107 are fixed on the fixing plates 109 through a soldering process.
The optical pickup actuator will be now described in more detail.
The object lens 101 is mounted on the central portion of the lens holder 102. The focusing coil 105 for focusing is wound around each corner of the lens holder. The tracking coil for tracking is wound around a center portion of left and right surfaces of the lens holder 102.
The yokes 104 are formed of a ferromagnetism material protrude. The yokes face the focusing and tracking coils 105 and 106. The magnets are fixed on front surfaces of the respective yokes 104. The yokes 104 are fixed on a pickup base (not shown).
The fixing plates 108 are couple to the lens holder 102. The first ends of a pair of wire suspensions 107 parallel to each other are fixed to each fixing plate 108 through the soldering process. The second ends of the wire suspensions are fixedly inserted in a damper of the damper holder 109.
The damper is coupled inside the damper holder 109 so that the wire suspensions each having a rigidity can has a damping property. A main board (not shown) is coupled to an outer surface of the damper holder 109. The second ends of the wire suspensions 107 are actually fixed on the main board.
The lens holder 102 is lifted by the wire suspensions 107 and electric current is applied to the wire suspensions 107.
When electric current is applied to the tracking coil 106, repulsive and attractive forces are generated by an electromagnetic force between the focusing coil 105 and the magnets 103. By the repulsive and attractive forces, the lens holder 102 moves in the focusing direction (in a vertical direction), thereby operating a focusing servo for compensating for a focusing error.
The above-described optical pickup actuator is a moving coil type where the focusing and tracking coils 105 and 106 move together with the lens holder 102 around which the focusing and tracking coils 105 and 16 are wound.
There is also a moving magnet type where the magnets are attached on the outer circumference of the lens holder so as to move together with the lens holder. At this point, the movement using the magnets and the coils uses Lorentz's force of Fleming's left-hand rule.
The above-described optical pickup actuator reads and writes information on an optical recording medium. In recent years, as multimedia systems have been rapidly developed and capacities of multimedia contents such as games and movies has been increased, it has been required that the optical pickup actuator must be reliable to stably drive the multimedia systems for many hours.
When the multimedia system is driven for many hours, heat is generated by the electric current applied to the coils of the optical pickup actuator and transmitted to the object lens through the lens holder.
When the heat generated by the coils is transmitted to the object lens for a long time, the aberration is increased. Furthermore, when excessive electric current is applied to the coils, the object lens may be cracked due to a thermal-stress. Therefore, there is a need for an optical pickup actuator that can improve a driving reliability by reducing the heat transmitted from the coils to the object lens.
Also, in a high speed optical pickup actuator, even when the object lens is attached to the lens holder using adhesive, the lens holder may be different in a frequency response from the object lens since the adhesive force is not enough. That is, a resonance peak of the lens holder may be greater than a resonance peak of the object lens.
Therefore, there is also a need for an optical pickup actuator that can improve the driving reliability by attenuating the resonance characteristics.