Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2001-01-04
2002-10-01
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
Reexamination Certificate
active
06459665
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 89103353, filed Feb. 25, 2000.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method for compensating digital signal. More particularly, the present invention relates to a method for compensating the digital signal produced by a high speed of optical storage device.
2. Description of Related Art
Due to the rapid development of multimedia systems, optical storage device has become standard equipment in personal computers. To process ever-increasing quantities of image and audio data, rotating speed of the optical storage device has gone up tremendously. In general, part of the error signal from an optical device comes from the rotating frequency signal of the motor. When the optical disk spins fast, magnitude resulting from side effects also increases significantly. Hence, the error signal must be compensated properly.
FIG. 1
is a block diagram showing the architecture of a conventional focus and track servo system. The focus and track servo system includes an optical sensor
10
, a signal pre-amplifier
12
, a compensator
14
, a power amplifier
16
and an actuator & lens module
18
. The optical sensor
10
picks up focus error (FE) signal and lens position signal fed back from the lens of the optical pickup head to generate a plurality of signals to the signal pre-amplifier
12
. Output signal from the signal pre-amplifier
12
is combined with the disk wobble & vibration signal before feeding into the compensator
14
. Signal compensation is conducted inside the compensator
14
. The compensated signal is transferred to the power amplifier
16
, for amplification. The amplified signal is then transferred to the actuator & lens module
18
for producing lens position signal that drives the optical pickup head.
In general, error signal is compensated by a lead compensator and a lag compensator. Typically, the lead compensator is a differentiator circuit such as a high frequency filter capable of stabilizing any input signal. In contrast, the lag compensator is an integrator circuit capable of lowering the steady state error of low frequency signals.
FIGS. 2A and 2B
are two different conventional lead-lag compensator architectures.
FIG. 2A
is a block diagram of a serially connected lead-lag compensator while
FIG. 2B
is a block diagram of a parallel-connected lead-lag compensator. As shown in
FIG. 2A
, the error signal is input into a lead compensator
20
and then a lag compensator
22
. The output signal from the lag compensator
22
is passed to a power amplifier and then transferred to an actuator
24
. On the other hand, as shown in
FIG. 2B
, the error signal is sent to a lead compensator
20
′ and a lag compensator
22
′ concurrently. Output signals from the lead compensator
20
′ and the lag compensator
22
′ are summed before passing to a power amplifier. output signal from the power amplifier is transferred to an actuator
24
′.
As the rotating speed of an optical storage device increases, problems caused by insufficient bandwidth are more serious. Because the motor turns very fast, the rotating frequency may be too high for the lag compensator. Hence, when the aforementioned architectures are used to compensate for the error signal, the lead compensator and the lag compensator can hardly lower the steady state error at rotating frequency (the rotating frequency of the spindle motor for driving the optical storage device).
In addition, due to the high rotating frequency of the driving motor and the non-overlapping of amplified frequency bandwidths between the lead compensator and the lag compensator, suitable compensation is difficult to generate.
In the design of actuator for an optical disk system, secondary resonance problem may persist. Consequently, the lead compensator may be limited by second resonance, resulting in the inability to produce higher amplification of frequency and magnitude by the lead compensator. With a poor lead compensator design, a high frequency noise may be produced by the actuator. In the meantime, since the lead compensator can only amplify localized frequency, frequency bandwidth from the lag compensator may be compressed. Hence, conventional lead-lead compensator architecture can hardly meet the specification of optical device, especially in high speed optical storage device.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a signal compensation device for a high-speed optical storage device capable of processing the error signal at the high-speed rotating frequency.
A second object of this invention is to provide a signal compensation device for a high-speed optical disk system capable of processing the error signal at high-speed rotating frequency portion so that stead state error within the error signal is lowered.
A third object of this invention is to provide a signal compensation device for a high-speed optical disk system capable of processing the error signal at high-speed rotating frequency portion so that stead state error within the error signal is lowered, wherein the high-speed rotating frequency portion of the signal is processed by a bandpass filter.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a signal-compensating device for an optical storage device. The compensation device includes a lead compensator, a lag compensator, and a bandpass filter. The lead compensator picks up error signal from the optical system. The lag compensator is connected to the lead compensator for receiving signal from the lead compensator. The bandpass filter (BPF) also picks up error signal from the optical system and then amplifies the rotating frequency portion of the error signal. Finally, signal generated by the lag compensator and the amplified signal produced by the bandpass filter is summed and then transferred to the actuator of the optical system, thereby lowering stead state error of the error signal. Since the rotating frequency portion of the error signal is processed by a bandpass filter, problems generally associated with a conventional optical system due to insufficient frequency bandwidth are eliminated.
The invention provides an alternative signal-compensating device for an optical storage device. The compensation device includes a lead compensator, a lag compensator, and a bandpass filter. The lead compensator picks up an error signal from the optical system to produce a first output signal. Similarly, the lag compensator picks up the error signal from the optical system to produce a second output signal. The bandpass filter picks up the error signal from the optical system and amplifies the rotating frequency portion of the error signal to produce a third output signal. The first, the second and the third output signals are summed to produce a resulting signal. Finally, the summed signal is transferred to the actuator of the optical system. The rotating frequency portion of the error signal is processed by a bandpass filter. Hence, problems generally associated with a conventional optical system due to insufficient frequency bandwidth are eliminated.
This invention also provides a method for compensating the signal of an optical storage device. Error signal produced by the optical storage device is fed to a lead compensator, a lag compensator and a bandpass filter. The bandpass filter processes the error signal in the rotating frequency portion. Output signals from the lead compensator, the lag compensator, and the bandpass filter are summed into a compensated error signal for lowing a steady state error of the error signal
This invention also provides another method for compensating the signal of an optical storage device. Error signal produced by the optical storage device is fed to a lead compensator and a bandpass filter. The bandpass filter processes the error signal in the rotating
Huber Paul W.
J.C. Patents
Via Technologies Inc.
LandOfFree
Signal compensation for high-speed optical storage device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Signal compensation for high-speed optical storage device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Signal compensation for high-speed optical storage device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2977407