Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
1999-04-29
2001-11-27
Tran, Thang V. (Department: 2651)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S053140
Reexamination Certificate
active
06324140
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to an optical disk device, and in particular to an eccentric disk detection apparatus for detecting eccentricity of an optical disk inserted within an optical disk device and controlling revolution of the disk accordingly.
2. Description of the Related Art
The development of high performance personal computers has led to optical disk devices which provide high-speed disk revolution to an optical disk, such as a CD-ROM (Compact Disk-Read Only Memory), CD-R (CD-Recordable), CD-RW (CD-ReWritable), and DVD-RAM (Digital Video Disk-Random Access Memory), inserted within the optical disk device. High-speed disk revolution can cause an eccentric disk, e.g., a disk which is not precisely flat or round, etc., to vibrate. The vibration can adversely affect the personal computer, including the optical disk device, by creating unnecessary noise, by causing failure in the reproduction of the data stored within the optical disk, or by causing failure in writing data to the optical disk.
To prevent the eccentric disk from vibrating, methods have been suggested in order to counteract the eccentricity of the disk. In one method, an automatic balancing device having a circular guide and a sphere rotating over the guide is provided to a spindle motor. During the rotation of the spindle motor, the sphere is automatically positioned in a location where eccentricity is compensated for. Another method calls for the use of an acceleration sensor during revolution of the eccentric disk to detect vibrations.
An unreliable compensation for eccentricity is typically made by using the automatic balancing device due to the slide friction between the sphere and the slide. Further, a non-eccentric disk could be made eccentric by the rotating sphere. Further still, the requirement for a highly precise guide and sphere mechanism can increase the cost of the automatic balancing device. The method utilizing the acceleration sensor also leads to an increase in cost.
A need therefore exists for an eccentric disk detection apparatus for an optical disk device which provides a reliable compensation for eccentricity, protects non-eccentric disks, provides high performance, and is inexpensive.
SUMMARY
An eccentric disk detection apparatus for an optical disk device is provided. The optical disk device includes a pickup mounted to a base for reading or writing data stored within or to the disk. The base includes a disk rotating device, such as a spindle motor, for mounting the disk thereon and for rotating the same. The base is elastically supported by rubber members which are vibrated due to the eccentricity of the disk during revolution of the disk. The eccentric disk detection apparatus detects the vibrations by sensing a reverse electromotive force generated by a pickup actuator coil in proximity to the pickup.
The pickup has a lens driver supported by a spring formed of wire. A magnetic circuit including a coil for focus control, a yoke, and a magnet in the lens driver experience a relative vibration during operation, thereby generating the reverse electromotive force in proportion to a rotational speed in the coil. The pickup actuator coil also generates or senses the reverse electromotive force and eccentricity can be detected by the eccentric disk detection apparatus, as well as whether the eccentricity is high or low.
A pickup driver and an amplifier are connected in parallel to both ends of the pickup actuator coil. And analog-to-digital (A/D) converter converts the output of the amplifier to a digital signal. A central processing unit (CPU) controls the number of revolutions of the spindle motor according to a reverse electromotive force represented by the digital signal received from the A/D converter. The CPU detects the amplitude of the digital signal representing the reverse electromotive force. If the obtained amplitude value exceeds a predetermined reference value, the CPU determines the disk to be highly eccentric.
Upon detection of eccentricity, the eccentric disk detection apparatus can adjust or decrease the maximum number of revolutions of the disk in accordance to the sensed reverse electromotive force, thereby compensating for the eccentricity of the disk. That is, by decreasing the number of disk revolutions in accordance to the eccentricity of the disk, the vibrations can be reduced. Also, upon sensing the reverse electromotive force, the pickup actuator coil temporarily stops to differentiate the reverse electromotive force from a driving signal flowing through the coil. It is preferred for the disk to revolve at a constant velocity during the sensing of the reverse electromotive force to increase sensing accuracy.
The resilient supporting members of the base can be influenced by temperature. Consequently, the vibrations transferred to the pickup can be altered according to the temperature within the disk device and not because of the disk's eccentricity. Thus, the sensed reverse electromotive force can be changed to appropriately correspond to a temperature reading measured by a temperature sensor. It is noted that detection of eccentricity can be omitted to reduce operation time for low-speed disks, such as an audio disk, since these disks do not require control of their revolution based on their eccentricity.
REFERENCES:
patent: 5701284 (1997-12-01), Lee
patent: 5886966 (1999-03-01), Ota et al.
patent: 5963517 (1999-10-01), Nakagaki et al.
patent: 6097680 (2000-08-01), Yen et al.
patent: 6111826 (2000-08-01), Minase
Kgami Shin
Tomishima Yuichiro
Dilworth & Barrese LLP
Samsung Electronics Co,. Ltd.
Tran Thang V.
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