KR20060020816A - Servo control characteristic fixing method for optical disc apparatus - Google Patents

Abstract

According to the present invention, when the side beam signal of the digital multi-function disk is weak, it is possible to adjust the tracking error signal gain value of the main beam by following the tracking error signal gain value of the side beam to thereby adjust the optimal side beam tracking error signal gain. A method of setting servo control characteristics of an optical disk device to find a value is provided. To this end, the present invention provides a method for adjusting the characteristics of a tracking servo, the method comprising: detecting a first tracking error signal and a second tracking error signal while biasing an incident beam to a recording medium from side to side, and detecting the detected first tracking Adjusting a first gain of the first tracking error signal and a second gain of the second tracking error signal together so that a value at an arbitrary position of the incident signal of the error signal and the second tracking error signal does not differ. Characterized in that made.

Optical record carrier, tracking error signal, MPP, SPP, offset, gain

Description

SERVO CONTROL CHARACTERISTIC FIXING METHOD FOR OPTICAL DISC APPARATUS}             

1 is a diagram showing a configuration of an apparatus for reproducing an optical recording medium to which the method of the present invention is applied;

2 is a view showing a detailed configuration of the gain adjustment unit shown in FIG.

3 is a view showing a state in which an auxiliary photodetector is disposed in front and rear ends of a main photodetector for tracking error detection by the DPP method applied to the present invention;

4 is a diagram illustrating a state in which a center voltage of a tracking error signal varies according to an amount of deviation of an objective lens;

5A and 5B are views exemplarily illustrating a state in which the center voltage of the tracking error signal is adjusted by adjusting a gain value of the MPP tracking error signal downward with respect to the tracking error signal of the SPP system according to an exemplary embodiment of the present invention;

7 is a flowchart for explaining the operation of the servo control characteristic setting method of the optical disk apparatus according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: optical record carrier, 12: optical pickup,

14: RF processor, 16: MPP generator,

18: SPP generation unit, 20: gain adjustment unit,

22: digital signal processing unit (DSP), 24: servo control unit,

26: pickup drive unit, 28: servo drive unit.

The present invention relates to a method for setting a servo control characteristic of an optical disk device, and more particularly, to a method for setting a tracking servo control characteristic for shortening the tracking tracking time of an optical pickup lens during seek or access on an optical recording medium. It is about.

As is well known, Digital Versatile Disc Read Only Memory (DVD-ROM) or Rewritable Digital Versatile Disc (DVD-RW, DVD-RAM), Recordable Digital Versatile Disc In the case of reproducing a digital versatile disc (DVD) such as a (Recordable Digital Versatile Disc; DVD-R) through a playback device, the playback device generates a tracking error signal from the reflected beam for tracking control.

There are three beam generation methods, a push pull method, a differential phase detection (DPD) method, and the like, for generating a tracking error signal from the digital multifunction disk. A pair of tracking side beam spots are arranged before and after the main beam spot for reading information, and the main light detecting element detecting the light amount of the main beam and the light amount of the side beam are detected. The reflection beam is split by the side photodetector to generate a tracking error signal.

In addition, in the case of the phase difference detection method, the change of the reflected light intensity according to the relative left and right shift of the track fit of the disk with respect to the light beam is used by using the photodetection element divided into four, and thus the signal track direction (ie, Four photodetectors, which are divided into four directions in the general direction) and the radial direction, are arranged to detect the phase difference of the electrical signal according to the amount of light obtained from each photodetector to obtain a tracking error signal.

In the case of the push-pull method, a photodetector for detecting the reflected light from the digital multifunction disk is divided into two along the track direction of the disk, and arranged back and forth with respect to the four divided photodetectors. In order to generate the tracking error signal from the light quantity balance, the intensity distribution of light diffracted and reflected by the track pit and incident through the objective lens is changed by the relative positional change between the pit and the light spot.

However, in the case of generating a plurality of tracking error signals TE1 and TE2 of the digital multifunction disc through the three-beam method and the push-pull method and performing tracking based on the difference signals TE1 to TE2, the side of the optical pickup is provided. Since the side beam signal is weak, the signal level of the tracking error signal component detected by the side photodetector becomes small, so that even if the gain of the tracking error signal caused by the side beam is adjusted, the difference signal between the two error signals is reduced. The tracking is out of the tracking following range and the tracking is delayed.

Accordingly, the present invention has been made to solve the above-described conventional problems, and its object is to control all of the plurality of tracking error signals by the disc recording medium to eliminate the bias voltage of the tracking signal, thereby enabling fast tracking during seek or access. It is to provide a method for setting servo control characteristics of an optical disk device to start this operation.

According to the present invention for achieving the above object, there is provided a method of adjusting the characteristics of a tracking servo, comprising the steps of: detecting a first tracking error signal and a second tracking error signal while biasing an incident beam to a recording medium from side to side; The first gain of the first tracking error signal and the second of the second tracking error signal so that a value at any position of the incident beam of the detected first tracking error signal and the second tracking error signal does not differ. A method of setting a servo control characteristic of an optical disk device, comprising adjusting gains together.

In one embodiment of the present invention, the gains of the first tracking error signal by the main quadrant beam and the second tracking error signal by both side beams are adjusted together so that the difference between the two signals does not have a bias voltage equal to or greater than the center voltage.

Further, in the above embodiment, the gain of the second tracking error signal is first adjusted to an adjustable upper and lower limit to adjust the gain of the first tracking error signal when the bias voltage still occurs in the difference between the two error signals. Do not occur.

Hereinafter, the present invention configured as described above will be described in detail with reference to the accompanying drawings.

That is, FIG. 1 is a diagram showing the configuration of a reproducing apparatus of an optical recording medium to which the method of the present invention is applied.

As shown in FIG. 1, the optical recording medium reproducing apparatus includes an optical recording medium 10, an optical pickup 12, an RF processor 14, a digital signal processor (DSP) 22, and a servo controller. 24, the pickup driver 26, and the servo driver 28. As shown in FIG. 6 is a flowchart of a preferred embodiment of the servo control characteristic setting method according to the present invention.

Hereinafter, the flowchart according to the present invention of FIG. 6 will be described in detail in parallel with the operation of the apparatus of FIG. 1.

The optical pickup 12 is configured to turn on the laser (S11) after the initial offset adjustment (S10), and the light beam focused on the objective lens through the driving of the pickup driver 26 under the control of the servo controller 24 is It is irradiated on the information recording track of the optical recording medium 10, and the light reflected from the information recording track is focused through the objective lens to be incident on the optical detection element for the detection of the focus error signal and the tracking error signal.

The RF processor 14 filters and binarizes an electrical signal converted by the optical pickup 12, and includes a plurality of optical detection elements to generate a focus error signal and a tracking error signal. To this end, the MPP generator 16, the SPP generator 18, and the gain adjuster 20 are configured.

The MPP generation unit 16 is an MPP tracking error signal (MPPe = (A + D)-(B + C)) based on signals detected from four main photodetectors for the four-split main beam. The SPP generator 18 generates a tracking error signal of the SPP method SPPe = (E + G)-(F by a signal detected from a side photodetector disposed before and after the main photodetector. + H)).

In addition, the gain adjuster 20 detects a voltage difference of the voltage value MPPe from the MPP generator 16 with respect to the voltage value of the SPP tracking error signal SPPe from the SPP generator 18. The gain value of the MPP signal is adjusted in accordance with the adjustment range of the SPP gain.

As shown in FIG. 2, the gain adjusting unit 20 may include a first low pass filter (LPF) 30 which low-pass filters the MPP tracking error signal MPPe from the MPP generator 16, and A second low pass filter 32 for low-pass filtering the SPP tracking error signal SPPe from the SPP generator 18, an MPP voltage detector 34 for detecting the voltage of the MPPe signal, and a voltage of the SPPe signal. The slope difference value is obtained by estimating the slope of each error signal from the detected MPPe voltage and the SPPe voltage with respect to the bias applied voltage for lens bias from the SPP voltage detector 36 and the pickup driver 26. A voltage difference detector 38 for adjusting the gains of the MPP gain adjusting amplifier 40 and the SPP gain adjusting amplifier 42 in the subsequent stages, the MPP tracking error signal k1 * MPPe and the SPP tracking, respectively, in which the gain values are adjusted. Synthesis by subtracting the error signal (k2 * SPPe) It is configured to include a 44. The output signal DPPe = k1 * MPPe-k2 * MPPe of the synthesizer 44 is used as the final error signal for tracking.

FIG. 3 is a schematic diagram of a photodetector for splitly outputting a reflected beam. The MPP generator 16, as described above, is divided into four A, B, C, four divided into a tangential direction and a radial direction of an optical recording medium. The MPPe signal is generated and output from the D photodetecting device, and the SPP generating unit 18 divides the E, F photodetecting device and the G, H photodetecting device into two divided portions in the track direction arranged before and after the main photodetecting device. The SPPe signal is generated and output from the side photodetector.

As shown in FIG. 4, the MPP tracking error signal MPPe from the MPP generator 16 and the SPP tracking error signal SPPe from the SPP generator 18 generate a center voltage (offset voltage). Since the biased center voltage fluctuates according to the deviation of the objective lens, the DPPe signal, which is the output signal of the synthesizer 44 described above, is used to prevent the offset from being generated. Is called). By using this method and properly adjusting the gains of k1 and k2, the voltage biased to the center voltage does not occur even when the lens is biased.

To do this, first, the first order, that is, the slope of the MPPe signal and the SPPe signal are grasped. Gradient grasp is performed by the servo control unit 24, and the pickup driving unit 26 controls the size of the MPPe and SPPe signals at each position when the pickup driver 26 places the lens in two left, right, left, right, and three center points. Is detected by the voltage difference detector 38 to determine the characteristics of the signal (i.e., first-order graph or first-order slope) (S12). Then, the gains k1 and k2 of the MPP and the SPP gain adjustment amplifiers 40 and 42 are adjusted so that the inclination (when the voltage at the center is viewed from the origin) is the same. If both of the slopes are the same, the bias voltage based on the center voltage does not occur even if the lens skew occurs, so that tracking can resume quickly after seeking or access.

In order to make the slope after the gain adjustment of both error signals SPPe and MPPe equal, first, the gain k1 of the MPP error signal MPPe is set to 1 (S13), and an appropriate gain value (k2) for the SPP error signal SPPe is obtained. (S14) to see if k2 * SPPe is equal to the slope of MPPe (S15). Otherwise, if the slope of the SPP tracking error signal SPPe is not equal to the slope of MPPe even by the adjustable range of the k2 gain value, for example, 0 <slope (k2 * SPPe graph) <7), and the slope ( If MPPe) = 10, the gain k1 of the MPP signal MPPe is additionally adjusted (S16).

5a graphically illustrates an example thereof. As shown in FIG. 5A, when the gain is set to k2 of the maximum adjustment range with respect to the slope dS of the SPP tracking error signal SPPe, the gain falls short of the slope dM of the MPP tracking error signal MPPe. That is, when k2 * dS <dM, as shown in FIG. 5B, the gain value k1 of the MPP error signal is lowered to 1 or less to match the slope of the SPP error signal. That is, k1 * MPPe = k2 * SPPe. In this way, the DPPe signal does not generate a bias voltage higher than the center voltage even by the lens bias.

In another embodiment, the voltage difference detector 38 detects the magnitude of each signal in a biased state to the left or right of the objective lens instead of detecting the slopes of the SPPe and MPPe signals ('a' or FIG. 5A). 'b'), one or more gains k1 and k2 of the respective gain adjusting amplifiers 40 and 42 may be adjusted in a direction in which the difference between the detected magnitudes becomes zero.

On the other hand, the present invention is not limited to the above-described typical preferred embodiment, it can be carried out in various ways without departing from the gist of the present invention various modifications, changes, substitutions or additions in the art Anyone who has this can easily understand it. If the implementation by such improvement, change, replacement or addition falls within the scope of the appended claims, the technical idea should also be regarded as belonging to the present invention.

According to the present invention as described above, when the side beam signal of the optical pickup for reproducing the optical recording medium is weak and it is difficult to adjust the center voltage of the tracking error signal to a reference value by adjusting the gain of the SPP tracking error signal, the SPP tracking is performed. The gain value of the MPP tracking error signal can be adjusted up or down in accordance with the upper and lower limits of the adjustment range of the gain value of the error signal. The optimum alignment is possible, and the data access speed is improved because the fast tracking is performed even when the objective lens is shifted from the center to the left and right during seek or access operation.

Claims (6)

In the method of adjusting the characteristics of the tracking servo, A first step of detecting the first tracking error signal and the second tracking error signal while biasing the incident beam to the recording medium from side to side; The first gain of the first tracking error signal and the second gain of the second tracking error signal so that a value at any position of the incident beam of the detected first tracking error signal and the second tracking error signal does not differ. The servo control characteristic setting method of the optical disk device, characterized in that the second step of adjusting together. The method of claim 1, And the first tracking error signal is a signal generated by the left and right size difference of the main reflection beam caused by the incident beam. The method of claim 1, And the second tracking error signal is a signal generated by a left and right size difference of a side reflected beam caused by the incident beam. The method of claim 1, And the second step adjusts the first gain to an upper limit value or a lower limit value of the variation limit value, and then adjusts the second gain within a range of the variation limit value. The method of claim 1, In the second step, the first linear expression is generated from the values of the first tracking error signals detected at the plurality of bias positions of the incident beam, and the values of the second tracking error signals detected at the plurality of bias positions of the incident beam. And generating a second primary equation from the first gain and then adjusting the first gain and the second gain together in a direction in which the difference between the inclinations of the first and second primary equations becomes “0”. How to set the servo control characteristics. The method of claim 1, In the second step, the first gain and the second gain in a direction in which the difference between the value of the first tracking error signal and the value of the second tracking error signal detected at the left or right of the incident beam is zero. A method for setting servo control characteristics of an optical disk device, wherein the gain is adjusted together.

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