Rotation correcting apparatus and optical disk apparatus

A rotation correcting apparatus has a tracking servo controller which generates a tracking signal to perform a tracking servo control for guiding an optical beam spot outputted from a pickup to tracks of an optical disk and a track jump control for moving the optical beam spot to a certain track; a feed motor controller which controls a feed motor for moving the pickup to radius direction of the optical disk; a storage which stores signal component with a prescribed frequency band including a rotation frequency of the optical disk, the signal component being included in an output signal of the tracking servo controller; and a combination unit which combines the signal component stored in the storage with the tracking signal to generate an ultimate tracking signal for the tracking servo control and the tracking jump control, wherein the feed motor controller controls the feed motor based on the tracking signal generated by the tracking servo controller without using the signal component stored in the storage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority under 35USC§119 to Japanese Patent Application No. 2003-399773, filed on Nov. 28, 2003, the entire contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotation correcting apparatus and an optical disk apparatus that is used to record or reproduce data from an optical disk.

2. Related Art

In recent years, along the increase in rotation speed such as a CD-R/RW or a DVD-Drive, a drive unit that rotates a disk at near a limit rotation number of a disk motor and a pickup mechanism is being developed progressively. For example, techniques of increasing the data reading performance of a wobbling disk or an eccentric disk during a high-speed rotation and improving the accuracy of track jump and layer jump in a DVD double-layer disk is proposed (see Japanese Patent Application Laid-open Publication No. 2003-263760).

According to the technique described in the above document, a signal that follows the eccentricity or wobbling of the optical disk is A/D converted, and is stored in the memory. Based on the data stored in this memory, a pickup or a feed motor that shifts the pickup to a radial direction of the optical disk is controlled.

According to the above document, both a tracking servo system and a feed motor control system are subjected to eccentricity correction. However, the output from a feed motor control circuit that controls the feed motor makes no change irrespective presence or absence of eccentricity correction. A phase of a control signal from the feed motor control system is delayed from that of a control signal of the tracking servo system due to a phase delay in the feed motor control circuit. Therefore, when eccentricity correction is carried out in both the tracking servo system and the feed motor control system, the operation of the feed motor becomes unstable, because the actual eccentricity of the optical disk and the operation of the feed motor are not in the same phase. As a result, the servo control of the tracking servo system is not convergent.

SUMMARY OF THE INVENTION

A rotation correcting apparatus according to one embodiment of the present invention, comprising:

a tracking servo controller which generates a tracking signal to perform a tracking servo control for guiding an optical beam spot outputted from a pickup to tracks of an optical disk and a track jump control for moving the optical beam spot to a certain track;

a feed motor controller which controls a feed motor for moving said pickup to radius direction of the optical disk;

a storage which stores signal component with a prescribed frequency band including a rotation frequency of the optical disk, said signal component being included in an output signal of said tracking servo controller; and

a combination unit which combines the signal component stored in said storage with the tracking signal to generate an ultimate tracking signal for the tracking servo control and the tracking jump control,

wherein said feed motor controller controls said feed motor based on the tracking signal generated by said tracking servo controller without using the signal component stored in said storage.

DETAILED DESCRIPTION OF THE INVENTION

Hereafter, a rotation correcting apparatus and an optical disk apparatus according to the present invention will be described more specifically with reference to the drawings.

FIRST EMBODIMENT

FIG. 1is a block diagram showing a schematic configuration of a rotation correcting apparatus according to a first embodiment of the present invention. The rotation correcting apparatus shown inFIG. 1is used to record data onto or reproduce data from an optical disk (CD, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD±R, DVD-RAM, DVD±RW, etc.). The rotation correcting apparatus shown inFIG. 1has at least one of a reproduction function of reading data recorded on the optical disk and reproducing the data, and a recording function of recording data onto the optical disk.

The rotation correcting apparatus shown inFIG. 1includes a disk motor2, a pickup3, a motor4, an RF amplifier5(RF Amp), a tracking servo control circuit6, a focus servo control circuit7, and A/D converter8, a memory9, and FG PLL10, a memory address control circuit11, a D/A converter12, an adder13, a system controller14, lens drive signal generating circuits15and16, an adder17, an adder18, a feed motor control circuit19, a motor driver20, actuator drivers21and22, a disk motor control circuit23, a disk motor driver24, an MPEG video decoder/encoder & audio decoder/encoder processing circuit or data buffer circuit25, a CD/DVD data signal processing circuit26, a record control circuit27, a data extracting circuit & synchronization detaching circuit28, a disk address decoder29, a correcting RAM30, switch circuits31and32, and an adder33.

The disk motor2rotates an optical disk1. The pickup3irradiates an optical beam spot to the optical disk1. The motor4shifts the pickup3to a radial direction of the optical disk1. The RF amplifier5amplifies an RF signal as an information signal read from the optical disk1. The tracking servo control circuit6controls a tracking actuator of the pickup3based on a tracking error signal output from the RF amplifier5. The focus servo control circuit7controls a focus actuator of the pickup3based on a focus error signal output from the RF amplifier5. The A/D converter8conducts A/D conversion with respect to outputs from the tracking servo control circuit6and the focus servo control circuit7. The memory9stores data indicating wobbling or eccentricity output from the A/D converter8. The FG PLL10generates a clock signal synchronous with an FG signal output from the disk motor2. The memory address control circuit11generates an address based on a clock signal generated by the FG PLL10. The D/A converter12reads data corresponding to the address generated based on the memory address control from the memory9, and D/A converts the read data. The adder13adds an analog signal output from the D/A converter12to an output signal from the tracking servo control circuit6. The system controller14controls the whole apparatus shown inFIG. 1. The adder17adds an output from the lens drive signal generating circuit15to an output from the adder13. The adder18adds an output from the lens drive signal generating circuit16to an output from the focus servo control circuit7.

The RF amplifier5extracts a tracking error signal TE, a focus error signal FE, and an RF signal as an information signal, from a signal read from the optical disk1with the pickup3.

The tracking error signal TE is input to the tracking servo control circuit6. The tracking servo control circuit6includes a high-pass filter (HPF)41, a low-pass filter (LPF)42, and an adder43that combines outputs from filters together, of which detailed configuration is as shown inFIG. 2. The high-pass filter41is an active filter that includes an operational amplifier44, resistors R1to R4, and a capacitor C1. The high-pass filter41is used to advance a phase of the tracking error signal, that is, for phase compensation. The low-pass filter42is an active filter that includes an operational amplifier45, resistors R5and R6, and a capacitor C2. The low-pass filter42is mainly used to obtain a gain, that is, for gain compensation. The adder43includes an operational amplifier46, and a resistor R7connected between a negative input terminal and an output terminal of the operational amplifier46.

FIG. 3is an equalize characteristic diagram of the tracking servo control circuit6, where a solid-line waveform “a” is a characteristic diagram of the high-pass filter41, a solid-line waveform “b” is a characteristic diagram of the low-pass filter42, and a dotted-line waveform “c” is a characteristic diagram of a total characteristic. As shown inFIG. 3, gains become high in a low frequency area and a high frequency area. However, a rotation frequency of the optical disk1needs to be within a passage of the low-pass filter42.

FIGS. 4A-4Dare characteristic diagrams of the tracking servo system, whereFIG. 4Ais a characteristic diagram of the tracking actuator,FIG. 4Bis a diagram showing a transmission function of the tracking servo control circuit6,FIG. 4Cis an open loop characteristic diagram of the tracking servo system, andFIG. 4Dis a closed loop characteristic diagram of the tracking servo system.

As is clear fromFIG. 4D, the tracking servo system controls such that a gain in the low frequency area becomes 0 dB. Because wobbling or eccentricity occurs in the low frequency area, according to the present embodiment, eccentricity is corrected based on a low-frequency component of the tracking error signal.

The adder17adds the tracking error signal to an output signal from the lens drive signal generating circuit15during a track jump operation. An output signal from the adder17is input to the actuator driver21, thereby driving the tracking actuator of the pickup3. The output signal from the tracking servo control circuit6is also sent to the feed motor control circuit19, thereby driving the feed motor4via the motor driver20.

FIG. 5is a circuit diagram showing one example of a detailed configuration of the feed motor control circuit19. The feed motor control circuit19shown inFIG. 5includes an operational amplifier51, a resistor R8connected between an input terminal and a negative input terminal of the operational amplifier51, and a capacitor C3and a resistor R9connected in series between the negative input terminal and an output terminal of the operational amplifier51.

FIGS. 6A and 6Bare characteristic diagrams of the feed motor control circuit19, whereFIG. 6Ais a characteristic diagram showing a relationship between a frequency and a gain of the feed motor4, andFIG. 6Bis a characteristic diagram showing a relationship between a frequency and a phase of the feed motor4. FromFIG. 6AandFIG. 6B, it is clear that a phase is delayed in the rotation frequency (eccentric frequency) band of the disk motor2. Due to the characteristics and the mechanical phase delay of the feed motor4system as shown inFIG. 6, the actual eccentricity does not coincide with the move of the feed motor4, and therefore, the move of the feed motor4cannot be set ideal relative to the eccentricity. According to the present embodiment, the eccentricity is not corrected in the feed motor control system.

The focus error signal FE is input to the focus servo control circuit7. The focus servo control circuit7also has a high-pass filter52and a low-pass filter53having a configuration similar to that shown inFIG. 2. The A/D converter8conducts A/D conversion with respect to a low-frequency component of the focus servo control circuit7, and stores the converted result into the memory9.

During a focus searching, the adder13adds the focus error signal and the output of the lens drive signal generating circuit16, and the added result is sent to the actuator driver22, thereby driving the focus actuator of the pickup3.

To read and reproduce data from the optical disk1, the RF signal is sent to the data extracting circuit & synchronization detaching circuit28. The data extracting circuit binarizes the RF signal, extracts a bit clock, extracts a synchronization signal, and sends data to the CD/DVD data signal processing circuit26.

The CD/DVD data signal processing circuit26demodulates the data, and corrects the data using the correcting RAM30. The synchronization signal is sent to the disk motor control circuit23, which controls the disk motor2via the motor driver24. In the case of the CAV control, the FG signal from the disk motor2is input to the disk motor control circuit23. To reproduce a video with a device like a DVD video recorder, the data corrected by the CD/DVD data signal processing circuit26is sent to the MPEG video decoder and audio decoder processing circuit25, and a video signal and an audio signal are output.

To record data onto the optical disk1, the MPEG encoder25converts the video signal and the audio signal into digital data. The CD/DVD data signal processing circuit26converts the data into a data format which can record it on the optical disk1, and modulates the data. In the case of the DVD recording/reproducing drive, the data buffer25exchanges data with the host computer, and the CD/DVD data signal processing circuit26modulates/demodulates the data. The system controller14controls the control timing of each control circuit and the total set.

The system controller14can read address information of the optical disk1from the CD/DVD data signal processing circuit26.

The FG PLL10generates a multiplied clock synchronous with the FG signal, based on the FG signal output from the disk motor2. Most of motors recently used for the optical disk1are hall motors. A signal of a hall sensor within the motor is fetched as the FG signal, thereby generating the FG signal. In most cases, number of poles per one rotation of the motor is relatively small. The FG PLL10generates a multiplied clock of a high frequency synchronous with the FG in order to increase the resolution in the rotation direction. The memory address control circuit11controls the data memory9based on this clock. The data memory9is controlled in the clock based on the FG signal, and fetches data in synchronism with the rotation. Data can be read from the memory9.

FIGS. 7A-7Hare waveform diagrams showing an eccentric component of the rotation correcting apparatus according to the present embodiment.FIG. 7Ais a waveform diagram showing a displacement of the lens of the pickup3from the mechanical center,FIG. 7Bis a waveform diagram of an output from the low-pass filter42within the tracking servo control circuit6,FIG. 7Cis a waveform diagram of an input to the actuator driver21,FIG. 7Dis a waveform diagram of an output from the feed motor control circuit19,FIG. 7Eis a waveform diagram of an output from the A/D converter8,FIG. 7Fis a waveform diagram of an output from the D/A converter12, andFIG. 7Gis a waveform diagram of a tracking signal that is input to the pickup3.

As shown inFIGS. 7A-7H, the rotation correcting apparatus according to the present embodiment has two operation modes of a calibration cycle period p1during which an eccentric component of the optical disk is stored in the memory, and a rotation compensation operation period p2during which data is recorded onto or reproduced from the optical disk while carrying out eccentricity correction. During the calibration cycle period p1, the switch circuits31and32shown inFIG. 1are in the off state, and the adder13and33do not carry out the add processing.

As shown inFIG. 7A, the lens of the pickup3is shaken largely due to eccentricity. An output signal from the low-pass filter42within the tracking servo control circuit6shown inFIG. 7Bis a signal that follows eccentricity. This signal determines a position of the lens of the pickup3from the mechanical center. This signal is converted into a digital signal and is stored into the memory9, and, at the same time, is input to the actuator driver21as shown inFIG. 7C.

The output (FIG. 7E) from the A/D converter8during the calibration cycle period is stored into the memory9. This is an eccentric component. During the rotation compensation operation period after the calibration cycle, the output (FIG. 7F) from the memory9is read, and eccentricity correction is carried out to the tracking signal (FIG. 7G). As a result, the output from the tracking servo control circuit6has no eccentric component, and the output from the feed motor control circuit19has no eccentric component either (FIG. 7D).

FIG. 8shows an example of carrying out eccentricity correction to the feed motor control system based on eccentricity data stored in the memory. According to the rotation correcting apparatus shown inFIG. 8, a connection position of the adder13is different from that shown inFIG. 1. The output from the adder13shown inFIG. 8is also input to the feed motor control circuit19.

FIG. 9is a waveform diagram showing an eccentric component shown inFIG. 8. As shown inFIG. 9, unlikeFIG. 7, the waveform of an output from the feed motor control circuit19includes an eccentric component, during the rotation compensation operation period p2. Therefore, according to the rotation correcting apparatus shown inFIG. 8, the operation of the feed motor4becomes unstable. As a result, it may take a longer time for the operation of the tracking servo to be stabilized.

As explained above, according to the first embodiment, an eccentric component stored in the memory9is not applied to the feed motor control circuit19. Therefore, the operation of the feed motor4is stabilized. Consequently, the operation of the tracking servo can be stabilized, and the time taken for the tracking servo to be converged can be shortened.

SECOND EMBODIMENT

According to a second embodiment, tracking servo is carried out by digital processing.

FIG. 10is block diagram showing a schematic configuration of a rotation correcting apparatus according to the second embodiment of the present invention. InFIG. 10, constituent elements common to those shown inFIG. 1are designated with like reference numerals, and differences between those drawings are mainly explained below.

The rotation correcting apparatus shown inFIG. 10includes an A/D converter61that conducts A/D conversion with respect to the tracking error signal TE output from the RF amplifier5, an A/D converter62that conducts A/D conversion with respect to the tracking error signal FE output from the RF amplifier5, a D/A converter63that is connected to a pre-stage of the motor driver20, and D/A converters64and65that are connected to pre-stages of the actuator drivers21and22, respectively. A tracking servo control circuit6aincludes a high-pass filter41athat extracts only a high-frequency component of a digital tracking error signal output from the A/D converter61, and a low-pass filter42athat extracts only a low-frequency component. The rotation correcting apparatus shown inFIG. 10further includes a variable coefficient multiplier13athat combines an output of the memory9with an output of the tracking servo control circuit6a, and a variable coefficient multiplier33athat combines the output from the memory9with an output from the focus servo control circuit7a.

FIG. 11is a circuit diagram showing one example of detailed configurations of the tracking servo control circuits6aand7a. As shown inFIG. 11, the high-pass filter41aincludes digital coefficients71to74, adders75to77, and one sample delay unit78. The low-pass filter42includes buffers81to84, adders85and86, and one sample delay unit87. An eccentric component is extracted from the output from the low-pass filter42in a similar manner to that according to the first embodiment.

FIG. 12is a circuit diagram showing one example of a detailed configuration of the motor control circuit19a. As shown inFIG. 12, the feed motor control circuit19aincludes digital coefficients91to94, adders95, and one sample delay unit97.

FIG. 13is a waveform diagram showing the operation of the variable coefficient multipliers13aand33ashown inFIG. 10. The variable coefficient multipliers13aand33ashown inFIG. 10gradually increase coefficients to avoid deviation of the tracking servo and the focus servo.

As explained above, according to the second embodiment, tracking servo control and focus servo control are carried out digitally. Therefore, there is little influence of noise, and integration becomes easy.

At least a part of the rotation correcting devices explained in the first and the second embodiments can be prepared in a semiconductor chip. For example, each part is accommodated in one chip, excluding the disk motor2, the pickup3, the feed motor4, the RF amplifier5, the motor driver20, the actuator drivers21and22, and the system controller14shown inFIG. 1. With this arrangement, a circuit area can be reduced, and costs of parts can be reduced. Furthermore, the system controller14and the RF amplifier5can be also incorporated in the chip.