Abstract:
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.

Description:
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. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing a schematic configuration of a rotation correcting apparatus according to a first embodiment of the present invention. 
       FIG. 2  is a circuit diagram showing one example of detailed configuration of a tracking servo control circuit and a focus servo control circuit. 
       FIG. 3  is an equalize characteristic diagram of the tracking servo control circuit. 
       FIGS. 4A-4D  are characteristic diagrams of the tracking servo system. 
       FIG. 5  is a circuit diagram showing one example of a detailed configuration of the feed motor control circuit. 
       FIGS. 6A and 6B  are characteristic diagrams of the feed motor control circuit. 
       FIGS. 7A-7H  are waveform diagrams showing an eccentric component of the rotation correcting apparatus according to the present embodiment. 
       FIG. 8  is a block diagram showing an example of carrying out eccentricity correction to the feed motor control system based on eccentricity data stored in the memory. 
       FIG. 9  is a waveform diagram showing an eccentric component shown in  FIG. 8 . 
       FIG. 10  is block diagram showing a schematic configuration of a rotation correcting apparatus according to the second embodiment of the present invention. 
       FIG. 11  is a circuit diagram showing one example of detailed configurations of the tracking servo control circuits. 
       FIG. 12  is a circuit diagram showing one example of a detailed configuration of the motor control circuit. 
       FIG. 13  is a waveform diagram showing the operation of the variable coefficient multipliers  13   a  and  33   a  shown in  FIG. 10 . 
   

   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. 1  is 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 in  FIG. 1  is 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 in  FIG. 1  has 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 in  FIG. 1  includes a disk motor  2 , a pickup  3 , a motor  4 , an RF amplifier  5  (RF Amp), a tracking servo control circuit  6 , a focus servo control circuit  7 , and A/D converter  8 , a memory  9 , and FG PLL  10 , a memory address control circuit  11 , a D/A converter  12 , an adder  13 , a system controller  14 , lens drive signal generating circuits  15  and  16 , an adder  17 , an adder  18 , a feed motor control circuit  19 , a motor driver  20 , actuator drivers  21  and  22 , a disk motor control circuit  23 , a disk motor driver  24 , an MPEG video decoder/encoder &amp; audio decoder/encoder processing circuit or data buffer circuit  25 , a CD/DVD data signal processing circuit  26 , a record control circuit  27 , a data extracting circuit &amp; synchronization detaching circuit  28 , a disk address decoder  29 , a correcting RAM  30 , switch circuits  31  and  32 , and an adder  33 . 
   The disk motor  2  rotates an optical disk  1 . The pickup  3  irradiates an optical beam spot to the optical disk  1 . The motor  4  shifts the pickup  3  to a radial direction of the optical disk  1 . The RF amplifier  5  amplifies an RF signal as an information signal read from the optical disk  1 . The tracking servo control circuit  6  controls a tracking actuator of the pickup  3  based on a tracking error signal output from the RF amplifier  5 . The focus servo control circuit  7  controls a focus actuator of the pickup  3  based on a focus error signal output from the RF amplifier  5 . The A/D converter  8  conducts A/D conversion with respect to outputs from the tracking servo control circuit  6  and the focus servo control circuit  7 . The memory  9  stores data indicating wobbling or eccentricity output from the A/D converter  8 . The FG PLL  10  generates a clock signal synchronous with an FG signal output from the disk motor  2 . The memory address control circuit  11  generates an address based on a clock signal generated by the FG PLL  10 . The D/A converter  12  reads data corresponding to the address generated based on the memory address control from the memory  9 , and D/A converts the read data. The adder  13  adds an analog signal output from the D/A converter  12  to an output signal from the tracking servo control circuit  6 . The system controller  14  controls the whole apparatus shown in  FIG. 1 . The adder  17  adds an output from the lens drive signal generating circuit  15  to an output from the adder  13 . The adder  18  adds an output from the lens drive signal generating circuit  16  to an output from the focus servo control circuit  7 . 
   The RF amplifier  5  extracts 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 disk  1  with the pickup  3 . 
   The tracking error signal TE is input to the tracking servo control circuit  6 . The tracking servo control circuit  6  includes a high-pass filter (HPF)  41 , a low-pass filter (LPF)  42 , and an adder  43  that combines outputs from filters together, of which detailed configuration is as shown in  FIG. 2 . The high-pass filter  41  is an active filter that includes an operational amplifier  44 , resistors R 1  to R 4 , and a capacitor C 1 . The high-pass filter  41  is used to advance a phase of the tracking error signal, that is, for phase compensation. The low-pass filter  42  is an active filter that includes an operational amplifier  45 , resistors R 5  and R 6 , and a capacitor C 2 . The low-pass filter  42  is mainly used to obtain a gain, that is, for gain compensation. The adder  43  includes an operational amplifier  46 , and a resistor R 7  connected between a negative input terminal and an output terminal of the operational amplifier  46 . 
     FIG. 3  is an equalize characteristic diagram of the tracking servo control circuit  6 , where a solid-line waveform “a” is a characteristic diagram of the high-pass filter  41 , a solid-line waveform “b” is a characteristic diagram of the low-pass filter  42 , and a dotted-line waveform “c” is a characteristic diagram of a total characteristic. As shown in  FIG. 3 , gains become high in a low frequency area and a high frequency area. However, a rotation frequency of the optical disk  1  needs to be within a passage of the low-pass filter  42 . 
     FIGS. 4A-4D  are characteristic diagrams of the tracking servo system, where  FIG. 4A  is a characteristic diagram of the tracking actuator,  FIG. 4B  is a diagram showing a transmission function of the tracking servo control circuit  6 ,  FIG. 4C  is an open loop characteristic diagram of the tracking servo system, and  FIG. 4D  is a closed loop characteristic diagram of the tracking servo system. 
   As is clear from  FIG. 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 adder  17  adds the tracking error signal to an output signal from the lens drive signal generating circuit  15  during a track jump operation. An output signal from the adder  17  is input to the actuator driver  21 , thereby driving the tracking actuator of the pickup  3 . The output signal from the tracking servo control circuit  6  is also sent to the feed motor control circuit  19 , thereby driving the feed motor  4  via the motor driver  20 . 
     FIG. 5  is a circuit diagram showing one example of a detailed configuration of the feed motor control circuit  19 . The feed motor control circuit  19  shown in  FIG. 5  includes an operational amplifier  51 , a resistor R 8  connected between an input terminal and a negative input terminal of the operational amplifier  51 , and a capacitor C 3  and a resistor R 9  connected in series between the negative input terminal and an output terminal of the operational amplifier  51 . 
     FIGS. 6A and 6B  are characteristic diagrams of the feed motor control circuit  19 , where  FIG. 6A  is a characteristic diagram showing a relationship between a frequency and a gain of the feed motor  4 , and  FIG. 6B  is a characteristic diagram showing a relationship between a frequency and a phase of the feed motor  4 . From  FIG. 6A  and  FIG. 6B , it is clear that a phase is delayed in the rotation frequency (eccentric frequency) band of the disk motor  2 . Due to the characteristics and the mechanical phase delay of the feed motor  4  system as shown in  FIG. 6 , the actual eccentricity does not coincide with the move of the feed motor  4 , and therefore, the move of the feed motor  4  cannot 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 circuit  7 . The focus servo control circuit  7  also has a high-pass filter  52  and a low-pass filter  53  having a configuration similar to that shown in  FIG. 2 . The A/D converter  8  conducts A/D conversion with respect to a low-frequency component of the focus servo control circuit  7 , and stores the converted result into the memory  9 . 
   During a focus searching, the adder  13  adds the focus error signal and the output of the lens drive signal generating circuit  16 , and the added result is sent to the actuator driver  22 , thereby driving the focus actuator of the pickup  3 . 
   To read and reproduce data from the optical disk  1 , the RF signal is sent to the data extracting circuit &amp; synchronization detaching circuit  28 . 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 circuit  26 . 
   The CD/DVD data signal processing circuit  26  demodulates the data, and corrects the data using the correcting RAM  30 . The synchronization signal is sent to the disk motor control circuit  23 , which controls the disk motor  2  via the motor driver  24 . In the case of the CAV control, the FG signal from the disk motor  2  is input to the disk motor control circuit  23 . To reproduce a video with a device like a DVD video recorder, the data corrected by the CD/DVD data signal processing circuit  26  is sent to the MPEG video decoder and audio decoder processing circuit  25 , and a video signal and an audio signal are output. 
   To record data onto the optical disk  1 , the MPEG encoder  25  converts the video signal and the audio signal into digital data. The CD/DVD data signal processing circuit  26  converts the data into a data format which can record it on the optical disk  1 , and modulates the data. In the case of the DVD recording/reproducing drive, the data buffer  25  exchanges data with the host computer, and the CD/DVD data signal processing circuit  26  modulates/demodulates the data. The system controller  14  controls the control timing of each control circuit and the total set. 
   The system controller  14  can read address information of the optical disk  1  from the CD/DVD data signal processing circuit  26 . 
   The FG PLL  10  generates a multiplied clock synchronous with the FG signal, based on the FG signal output from the disk motor  2 . Most of motors recently used for the optical disk  1  are 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 PLL  10  generates 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 circuit  11  controls the data memory  9  based on this clock. The data memory  9  is controlled in the clock based on the FG signal, and fetches data in synchronism with the rotation. Data can be read from the memory  9 . 
     FIGS. 7A-7H  are waveform diagrams showing an eccentric component of the rotation correcting apparatus according to the present embodiment.  FIG. 7A  is a waveform diagram showing a displacement of the lens of the pickup  3  from the mechanical center,  FIG. 7B  is a waveform diagram of an output from the low-pass filter  42  within the tracking servo control circuit  6 ,  FIG. 7C  is a waveform diagram of an input to the actuator driver  21 ,  FIG. 7D  is a waveform diagram of an output from the feed motor control circuit  19 ,  FIG. 7E  is a waveform diagram of an output from the A/D converter  8 ,  FIG. 7F  is a waveform diagram of an output from the D/A converter  12 , and  FIG. 7G  is a waveform diagram of a tracking signal that is input to the pickup  3 . 
   As shown in  FIGS. 7A-7H , the rotation correcting apparatus according to the present embodiment has two operation modes of a calibration cycle period p 1  during which an eccentric component of the optical disk is stored in the memory, and a rotation compensation operation period p 2  during which data is recorded onto or reproduced from the optical disk while carrying out eccentricity correction. During the calibration cycle period p 1 , the switch circuits  31  and  32  shown in  FIG. 1  are in the off state, and the adder  13  and  33  do not carry out the add processing. 
   As shown in  FIG. 7A , the lens of the pickup  3  is shaken largely due to eccentricity. An output signal from the low-pass filter  42  within the tracking servo control circuit  6  shown in  FIG. 7B  is a signal that follows eccentricity. This signal determines a position of the lens of the pickup  3  from the mechanical center. This signal is converted into a digital signal and is stored into the memory  9 , and, at the same time, is input to the actuator driver  21  as shown in  FIG. 7C . 
   The output ( FIG. 7E ) from the A/D converter  8  during the calibration cycle period is stored into the memory  9 . This is an eccentric component. During the rotation compensation operation period after the calibration cycle, the output ( FIG. 7F ) from the memory  9  is read, and eccentricity correction is carried out to the tracking signal ( FIG. 7G ). As a result, the output from the tracking servo control circuit  6  has no eccentric component, and the output from the feed motor control circuit  19  has no eccentric component either ( FIG. 7D ). 
     FIG. 8  shows 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 in  FIG. 8 , a connection position of the adder  13  is different from that shown in  FIG. 1 . The output from the adder  13  shown in  FIG. 8  is also input to the feed motor control circuit  19 . 
     FIG. 9  is a waveform diagram showing an eccentric component shown in  FIG. 8 . As shown in  FIG. 9 , unlike  FIG. 7 , the waveform of an output from the feed motor control circuit  19  includes an eccentric component, during the rotation compensation operation period p 2 . Therefore, according to the rotation correcting apparatus shown in  FIG. 8 , the operation of the feed motor  4  becomes 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 memory  9  is not applied to the feed motor control circuit  19 . Therefore, the operation of the feed motor  4  is 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. 10  is block diagram showing a schematic configuration of a rotation correcting apparatus according to the second embodiment of the present invention. In  FIG. 10 , constituent elements common to those shown in  FIG. 1  are designated with like reference numerals, and differences between those drawings are mainly explained below. 
   The rotation correcting apparatus shown in  FIG. 10  includes an A/D converter  61  that conducts A/D conversion with respect to the tracking error signal TE output from the RF amplifier  5 , an A/D converter  62  that conducts A/D conversion with respect to the tracking error signal FE output from the RF amplifier  5 , a D/A converter  63  that is connected to a pre-stage of the motor driver  20 , and D/A converters  64  and  65  that are connected to pre-stages of the actuator drivers  21  and  22 , respectively. A tracking servo control circuit  6   a  includes a high-pass filter  41   a  that extracts only a high-frequency component of a digital tracking error signal output from the A/D converter  61 , and a low-pass filter  42   a  that extracts only a low-frequency component. The rotation correcting apparatus shown in  FIG. 10  further includes a variable coefficient multiplier  13   a  that combines an output of the memory  9  with an output of the tracking servo control circuit  6   a , and a variable coefficient multiplier  33   a  that combines the output from the memory  9  with an output from the focus servo control circuit  7   a.    
     FIG. 11  is a circuit diagram showing one example of detailed configurations of the tracking servo control circuits  6   a  and  7   a . As shown in  FIG. 11 , the high-pass filter  41   a  includes digital coefficients  71  to  74 , adders  75  to  77 , and one sample delay unit  78 . The low-pass filter  42  includes buffers  81  to  84 , adders  85  and  86 , and one sample delay unit  87 . An eccentric component is extracted from the output from the low-pass filter  42  in a similar manner to that according to the first embodiment. 
     FIG. 12  is a circuit diagram showing one example of a detailed configuration of the motor control circuit  19   a . As shown in  FIG. 12 , the feed motor control circuit  19   a  includes digital coefficients  91  to  94 , adders  95 , and one sample delay unit  97 . 
     FIG. 13  is a waveform diagram showing the operation of the variable coefficient multipliers  13   a  and  33   a  shown in  FIG. 10 . The variable coefficient multipliers  13   a  and  33   a  shown in  FIG. 10  gradually 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 motor  2 , the pickup  3 , the feed motor  4 , the RF amplifier  5 , the motor driver  20 , the actuator drivers  21  and  22 , and the system controller  14  shown in  FIG. 1 . With this arrangement, a circuit area can be reduced, and costs of parts can be reduced. Furthermore, the system controller  14  and the RF amplifier  5  can be also incorporated in the chip.