• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The present invention relates to a servo control method for an optical disc having a high speed of arithmetic processing. The servo control method of the optical disc of the present invention comprises the steps of initializing the sampling frequency to the reference sampling frequency to correspond to the reference double speed, optionally lowering and changing the reference sampling frequency, optionally reducing to the reference sampling frequency, and Performing the servo by the sampled frequency. The servo control method of the optical disc of the present invention can perform a time-consuming operation such as automatic gain adjustment using a conventional digital servo controller.
    公开号:KR19990015116A
    申请号:KR1019970037021
    申请日:1997-08-01
    公开日:1999-03-05
    发明作者:김규진；민병훈
    申请人:구자홍；엘지전자 주식회사；
    IPC主号:
    专利说明:

    Servo control method of optical disc
    BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for an optical disc, and more particularly, to a servo control method for an optical disc having a high computational processing speed.
    In an optical disc system, in order to read a signal recorded on the disc and reproduce data, a process of irradiating a light beam to a signal track of the disc and converting the reflected signal into an electrical signal by a photodetector is required. This requires focusing, tracking, and spindle control. In particular, focusing and tracking servos require different servo bands depending on the type of disc and the disc's double speed playback. It is necessary to change the gain by automatically detecting its characteristics according to the type and speed of the disc, which is called automatic gain adjustment. However, if the automatic gain adjustment is performed during normal playback, the algorithm processing for the automatic gain adjustment causes a lot of computational processing to be performed in a limited time. Therefore, high speed hardware (especially a digital servo controller; DSP) is inevitably required to perform all the computations within a limited specific time. Since this results in an increase in the cost of the system, a system control method that does not result in an additional increase in cost is required.
    A control circuit of an optical disc using a digital servo controller according to the prior art will be described with reference to FIG. 1.
    1 is a block diagram showing a control circuit of an optical disc according to the prior art, in which the control circuit of the conventional disc according to the prior art is connected to the LD output control unit 14 under the control of the LD output control unit 14. An optical pickup 2 for irradiating a light beam to the signal track of the optical disc 1 and converting the light beam reflected from the signal track into an electrical signal roll; a preamplifier unit 3 connected in series to an output terminal of the optical pickup 2; A signal processor 4 connected to the output terminal of the preamplifier 3, an analog / digital converter 5 commonly connected to the preamplifier 3 and the signal processor 4, and an analog / digital converter 5 And a digital servo controller 6 commonly connected to the microcomputer 8 and controlled by the microcomputer 8, a digital / analog converter 7 connected to an output terminal of the digital servo controller 6, and a digital / analog. Focusing / Tit Commonly Connected to Output of Transducer 7 The king driver 9, the sled driver 10 and the spindle driver 11, the transport device 12 connected to the sled driver 10 and the optical pickup 2, and the optical disk 1 are mounted thereon. The motor 13 is connected to the output terminal of the spindle driver 11 in series.
    The light source from the laser diode is condensed on the signal track of the optical disc 1 by the objective lens OL, and the light is reflected on the signal track and passes through the objective lens OL. Photodiode (PD). In the photodiode PD, the received optical signal is converted into an electrical signal and supplied to the preamplifier 3. The preamplifier 3 detects the focus error signal, the tracking error signal, and the high frequency signal RF from the signals from the optical pickup 2 and supplies them to the signal processor 4 and the analog / digital converter 5. In this case, the high frequency signal RF is processed by the signal processor 4 to undergo error correction, decoding, and the like.
    The analog / digital converter 5 samples the focus error signal, the tracking error signal, the high frequency signal RF, and the like from the preamplifier 3 at a sampling frequency and converts the analog signal into a digital signal. The signal in digital form from the analog / digital converter 5 is supplied to the digital servo controller 6. The digital servo controller 6 then processes the signal from the analog-to-digital converter 5 under the control of the microcomputer 8 and performs signal processing such as filter operation and supplies it to the digital-to-analog converter 7. The digital / analog converter 7 converts a signal from the digital servo controller 6 into an analog signal and supplies it to the focusing / tracking driver 9, the sled driver 10, and the spindle driver 11 in common. . By the signal supplied to the focusing / tracking driver 9, the focusing / tracking driver 9 causes the light beam from the objective lens OL to fall within the depth of focus in the signal track of the optical disc 1. And a tracking servo for causing the light beam from the objective lens OL to follow the center of the signal track of the optical disc 1. In response to the signal input to the sled driver 10, the sled driver 10 drives the feeder to remove the direct current (DC) component of the tracking error to move the optical pickup 2 in the radial direction of the optical disc 1. Control to move linearly. By the signal supplied to the spindle driver 11, the spindle driver 11 controls to make the rotation speed of the motor 13 which mounted the optical disc 1 constant.
    The control circuit for controlling the optical disc 1 using the digital servo controller 6 depends on the processing speed of the digital servo controller 6. The frequency of disturbance changes according to the increase in the speed of the optical disk 1 or the type of the optical disk 1, and it requires more execution time to automatically adjust the gain of the servo system corresponding to the frequency of the disturbance. Digital servo controller is required. However, since the digital servo controller having such a high speed of operation is usually manufactured at high cost, the recording / reproducing apparatus of the optical disc employing the same has a low price competitiveness. Therefore, it is desirable to use a conventional digital servo controller without increasing the cost and to perform a computationally intensive operation in a limited time.
    Accordingly, it is an object of the present invention to provide a servo control method of an optical disc capable of performing many time-consuming computational processes such as automatic gain adjustment using a conventional digital servo controller.
    1 is a block diagram showing a control circuit of a conventional optical disc.
    2 is a characteristic diagram showing a relationship between a sampling frequency and a gain or phase when the sampling frequency is divided by a and stored in the servo control method of the optical disc according to the embodiment of the present invention.
    FIG. 3 is a characteristic diagram showing a relationship between a sampling frequency and a gain or phase when the gain value is lowered in FIG. 2. FIG.
    4 is a sampling frequency waveform diagram of a digital servo controller in a servo control method of an optical disc according to an embodiment of the present invention.
    Fig. 5 is a flowchart showing the processing procedure of the servo control method of the optical disc according to the embodiment of the present invention step by step.
    * Description of the symbols for the main parts of the drawings *
    1: optical disc 2: optical pickup
    3: preamplifier section 4: signal processing section
    5: analog to digital converter 6: digital servo controller
    7: digital to analog converter 8: microcomputer
    9: Focusing / Tracking Driver 10: Sled Driver
    11: spindle driver 12: feeder
    13: motor 14: LD output processing unit
    In order to achieve the above object, the servo control method of the optical disk according to the present invention comprises the steps of initializing the sampling frequency to the reference sampling frequency to correspond to the reference double speed, optionally lowering and changing the reference sampling frequency, and optionally the reference sampling frequency Reducing to and performing servo by the variable sampling frequency.
    The servo control method of the optical disk of the present invention comprises the steps of initializing the gain to the reference gain value to correspond to the reference double speed, selectively lowering and varying the reference gain value, optionally reducing to a reference gain value, and Performing servo by the gain value.
    Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.
    Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 2 to 5.
    2 and 3 are characteristic diagrams illustrating changes in a servo band according to a decrease in sampling frequency and a gain compensation method according to a sampling frequency reduction through simulation in a servo control method of an optical disc according to an embodiment of the present invention.
    In Figures 2 and 3, the horizontal axis represents the change in frequency (Hz), and the vertical axis in Figures 2 (A), 3 (A) and 2 (B), and 3 (B) shows gain (dB), respectively. And change of phase (deg).
    The first graph 1 is indicated by a solid line in the drawing, and is a servo transmission characteristic when the digital servo controller 6 is configured with a sampling frequency of fs. The second graph 2 is indicated by a dotted line, and in the case where the sampling frequency fs is lowered to 1 / a (a = 2 in the example of the figure), that is, when the digital servo controller 6 is configured with 1/2 x fs. Servo transmission characteristic.
    Referring to the first and second graphs (1, 2), lowering the sampling frequency to 1 / a increases the gain frequency at 0 (dB) (in FIG. 2 (A)), and the phase is 180 (deg). It can be seen that the frequency is lowered. The important thing is how much phase margin is when the sampling frequency is lowered.
    To this end, when the sampling frequency is lowered to 1 / a as shown in the second graph 2 in FIG. 3 and the loop gain is lowered in proportion to the reduced rate, the phase margin is affected by one servo. Decreases to a value that cannot be given.
    Therefore, operation processing that consumes a long time that is difficult to calculate at the basic sampling frequency fs lowers the sampling frequency and also reduces the loop gain in proportion to the sampling frequency. There is no difference except to give a little room.
    Here, the DC gain decreases at low frequencies by lowering the loop gain, but this area does not need to be considered because it does not significantly affect the servo band. In this case, a method of reducing the sampling time variably (by changing the value of a at 1 / a × fs) may be effectively applied to obtain more accurate characteristics, although there is no significant effect according to the DC gain reduction.
    4 is a timing diagram illustrating an interrupt cycle of a sampling frequency of a digital servo controller in the servo control method of the optical disc of the present invention.
    4A shows an interrupt period when the sampling frequency is a basic sampling frequency of fs. Here, the normal arithmetic processing time t normal of the digital servo controller is an absolutely necessary time for performing normal arithmetic processing, for example, arithmetic processing for focusing servo and tracking servo. However, when a separate calculation process such as automatic gain adjustment other than normal arithmetic processing such as focusing servo or tracking servo is required, and a separate calculation process such as automatic gain adjustment other than normal arithmetic processing is required, In order to perform arithmetic processing, the sampling frequency should be lowered so that the interrupt cycle is added to the normal arithmetic processing time t normal and a separate arithmetic processing time t auto such as automatic gain adjustment. That is, it should be more than normal operation processing time t normal + separate operation processing time t auto .
    Importantly, as described with reference to Figs. 2 and 3, gain selection is performed to secure an abnormal margin (stability) and automatic gain adjustment is performed to determine an optimum gain for the current disk and system.
    Fig. 5 is a flow chart showing the processing procedure of the servo control method of the optical disc of the present invention step by step, which is controlled by the microcomputer 8 shown in Fig. 1 and is performed by the digital servo controller 6.
    In the first stage, when the power supply is turned on or the optical disc is loaded, the system including the digital servo controller 6 is initialized (first stage). It is initialized at the basic sampling frequency fs to correspond to the double speed, and the loop gain is also initialized to the basic loop gain value G to correspond to the 1x speed. (Second step) Next, various servos in the normal mode are operated. The first task to the third task performing the operation processing to be performed is performed. At this time, the focusing servo for controlling the light beam from the objective lens to fall within the depth of focus of the signal track, unless it is in the automatic gain adjustment mode in the first task, which is an operation for focusing servo and tracking servo, and the liquid of the optical pickup 2. A tracking servo is driven to drive an actuator to control the objective lens to follow the center of the signal track. Tracking auto gain adjustment is performed after focusing tracking servo is performed. When the automatic gain adjustment mode is performed, the computation time is inevitably increased compared to the normal mode, and thus it cannot be calculated using the basic sampling frequency fs.
    Therefore, as described with reference to FIGS. 2 and 3, when setting the autofocus gain adjustment mode, the sampling frequency is divided by the basic focus sampling frequency fs by an arbitrary value a to be the frequency of fs / a (converted focus sampling frequency fs'). Lower it. In addition, the loop gain value is proportional to the focus sampling frequency fs 'converted to secure the phase margin by dividing the basic focus loop gain value G by an arbitrary value a and the basic focus loop gain value / a (converted focus loop gain value G'). To adjust it (Step 4).
    After performing the fourth step, it is determined whether the focus auto gain adjustment has been completed. (Step 5) If it is determined that the focus auto gain adjustment has been completed, it is recalibrated to the basic focus sampling frequency fs and the basic focus loop gain value G. The resetting of the basic focus sampling frequency fs is reset by adjusting to the converted focus sampling frequency fs' × a using an arbitrary value a in the fourth step. The reset of the default focus loop gain value G is reset to the converted focus loop gain value G '× a using the random value a in the fourth step. If it is determined that the adjustment is not completed, the fifth step is repeated.
    After performing the sixth step, the tracking automatic gain adjustment mode is set. At this time, the basic tracking sampling frequency fs is divided by an arbitrary value a, and the conversion tracking sampling frequency fs' = fs / a is adjusted, and the loop gain value is the basic tracking loop gain value G divided by an arbitrary value a. Adjust by decreasing the value of G '= basic loop gain value / a (step 7).
    After performing the seventh step, it is determined whether the tracking automatic gain adjustment is completed. (Step 8) If it is determined that the tracking auto gain adjustment is completed, the sampling frequency is the tracking sampling frequency fs' × a converted using the random value a in the seventh step, and the loop gain value is the converted tracking loop. The default tracking sampling frequency and the default tracking loop gain value are reset to the gain value G '× a. (Step 9) In step 8, if it is determined that focus auto gain adjustment is not completed, step 8 is repeated. .
    After all of these automatic gain adjustments are completed, the control signal is supplied from the microcomputer 8 to perform the next command from the microcomputer 8, and is interpreted. (Step 10) As a result of the analysis, the command is an arbitrary servo. If the command is for the first to third tasks corresponding thereto. Then, the digital servo controller 6 performs the tenth step. (Eleventh step)
    Operation processing performed by the digital servo controller 6 under the control of the microcomputer 8 is performed as the first task to the third task in accordance with the performance of each servo, and when the third servo controller 6 performs the normal mode in the third step, In step 11 may be optionally performed in the automatic gain adjustment mode.
    Looking at the processing procedure of each task step by step, the first task is performed arithmetic processing for the focus and tracking servo performed in the third or eleventh step. First, the focus servo is performed (step 12), and it is determined whether the focus auto gain adjustment mode is set (step 13). As a result, it is determined whether the focus auto gain adjustment mode is set. (Step 13) As a result, if the focus auto gain adjustment mode is set, focus auto gain adjustment is performed (step 14). Next, it is determined whether the focus auto gain adjustment has ended (step 15). If it is determined, focus auto gain adjustment completion is set (step 16), and then tracking servo is sequentially performed. (Step 17) Meanwhile, in step 13, the focus auto gain adjustment mode is not set, and step 15 is performed. In step 17, if focus auto gain adjustment is not completed, step 17 is performed.
    Performs tracking servo and determines whether the current mode is the tracking auto gain adjustment mode (step 18). When it is determined that the tracking auto gain adjustment mode is performed, tracking auto gain adjustment is performed (step 19). (Step 20) If it is determined that the tracking auto gain adjustment is completed, the setting returns to the completion of the tracking auto gain adjustment. (Step 21) The tracking auto gain adjustment mode in step 18 If it is determined that the operation is not determined or the tracking auto gain adjustment is not completed in step 20, the method returns without performing the tracking auto gain mode.
    The second task is a processing procedure for performing and returning a spindle servo (step 22) for controlling the rotational speed of the motor 13 on which the disk 1 is seated, and the third task is an optical process in the radial direction of the disk 1. The processing procedure for performing and returning the sled servo for controlling the pickup 2 to linearly move (step 23) is shown.
    As described above, the servo control method of the optical disk of the present invention can perform a time-consuming operation such as automatic gain adjustment using a conventional digital servo controller.
    Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention.
    Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.
    权利要求:
    Claims (9)
    [1" claim-type="Currently amended] Initializing the sampling frequency to the reference sampling frequency so as to correspond to the reference double speed;
    Optionally lowering and varying the reference sampling frequency;
    Optionally reducing to a reference sampling frequency,
    And performing a servo by a variable sampling frequency.
    [2" claim-type="Currently amended] The method of claim 1,
    And the reference sampling frequency is divided by an arbitrary value.
    [3" claim-type="Currently amended] The method according to claim 1 or 2,
    And said variable sampling frequency is selectively multiplied by said arbitrary value and reduced to said reference sampling frequency.
    [4" claim-type="Currently amended] The method of claim 1,
    The lowering and varying of the sampling frequency may be selectively performed in the automatic gain adjustment step.
    [5" claim-type="Currently amended] The method of claim 4, wherein
    And the automatic gain adjustment is performed by a focusing servo that controls a light beam of an optical pickup for converting an optical signal into an electrical signal to fall within a depth of focus in a signal track of the disk.
    [6" claim-type="Currently amended] The method of claim 1,
    And the automatic gain adjustment is such that a light beam of an optical pickup for converting an optical signal into an electrical signal follows a center of a signal track of the disk.
    [7" claim-type="Currently amended] Initializing the gain to a reference gain value to correspond to the reference double speed;
    Optionally lowering and varying the reference gain value;
    Optionally reducing to the reference gain value,
    And performing a servo by the variable gain value.
    [8" claim-type="Currently amended] The method of claim 1,
    And the reference gain value is divided by an arbitrary value.
    [9" claim-type="Currently amended] The method according to claim 1 or 2,
    And said variable gain value is selectively multiplied by said arbitrary value to be reduced to said reference gain value.
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    同族专利:
    公开号 | 公开日
    KR100262958B1|2000-08-01|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1997-08-01|Application filed by 구자홍, 엘지전자 주식회사
    1997-08-01|Priority to KR1019970037021A
    1999-03-05|Publication of KR19990015116A
    2000-08-01|Application granted
    2000-08-01|Publication of KR100262958B1
    优先权:
    申请号 | 申请日 | 专利标题
    KR1019970037021A|KR100262958B1|1997-08-01|1997-08-01|Method for servo control of optical disk|
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