KR100255727B1 - Waveform equalization method of optical disc drive - Google Patents

Abstract

PURPOSE: A method for equalizing a waveform of an optical disk drive is provided to control an amplitude control coefficient according to a disk radius, so as to compensate a reproductive signal regardless of the disk radius in which signals are recorded. CONSTITUTION: The first delayer(10) delays an input signal 'Vi' as tau. The second delayer(20) delays an output signal of the first delayer(10) as the tau. The first amplitude controller(30) controls an amplitude of the input signal 'Vi', and inverses the amplitude. The second amplitude controller(40) controls the amplitude of the output signal of the first delayer(10). The third amplitude controller(50) controls an amplitude of an output signal of the second delayer(40), and inverses the amplitude. An adder(60) adds the output signals of the first amplitude controller(30) and the second amplitude controller(40) to an output signal of the third amplitude controller(50). A controller(100) controls the first and the third amplitude controller(30,50).

Description

Waveform Equalization Method of Optical Disc Drive

1 is a block diagram showing a conventional waveform equalizing device for an optical disc drive.

2 is a diagram showing the frequency characteristics of the waveform equalizer shown in FIG.

3 is a block diagram of a waveform equalizing device for explaining a waveform equalizing method of an optical disk drive according to the present invention;

* Explanation of symbols for main parts of the drawings

10, 20: 1st, 2nd delay part 30 ~ 50: 1st ~ 3rd amplitude adjustment part

60: adder 70: digital / analog converter

80: microprocessor or ROM 100: control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc drive, and more particularly, to a waveform equalization method for correcting inter-symbol interference caused by characteristics between a recording medium and an optical system, and between an optical system and an electrical system during reproduction of recorded data.

In general, an optical disc recording and reproducing system can be thought of as a kind of low pass filter, as can be easily imagined from the OTF of an objective lens, the response characteristics of a recording medium, and the like. Increasing the recording density of the recording medium increases the density of the pit to be recorded, affecting adjacent marks, and each reproduction waveform is likely to cause interference, thereby causing a reading error. This phenomenon is called inter-symbol interference.

In an optical disk drive using a laser beam, when a high frequency signal and a low frequency are mixed due to an inter-symbol interference of a disk, a high frequency signal is interrupted by a low frequency signal, and thus the signal level is reduced and jitter is generated. There was a problem.

Therefore, conventionally, a cosine waveform equalizer is used to remove such inter-signal interference, and its block diagram is shown in FIG.

Briefly summarizing the principle of the cosine waveform equalizer, the amplitude adjustment coefficient and the time delay coefficient are appropriately selected to sharpen the waveform of the input wave to remove the intersymbol interference.

First, in FIG. 1, the time delay coefficients of the first delay unit 10 and the second delay unit 20 are denoted by τ, and the first amplitude adjusting unit 30, the second amplitude adjusting unit 40, and the third amplitude are shown. The amplitude adjustment coefficient of the adjustment unit 50 is referred to as k.

Therefore, if the input signal A V _i = x (t), the output signal B of the first delay unit 10 becomes x (t−τ), and the output signal of the second delay unit 2 ( C) becomes x (t-2τ).

The first amplitude adjustment unit 30 and the third amplitude adjustment unit 50 respectively adjust and invert the amplitudes of the output signals of the input signal _Vi and the second delay unit 20 by the amplitude adjustment coefficient k, and invert the second amplitude. The adjusting unit 40 adjusts only the amplitude of the output signal of the first delay unit 10 by the amplitude adjusting coefficient k.

Therefore, the output signal g (t) of the adder 60 can be expressed as follows.

g (t) = B- (A + C)

= X (t−τ) −k {x (t) + x (t−2τ)}... … ①

In addition, the transfer function E (jw) for each frequency domain of the cosine waveform equalizer

E (jw) = {1-k (e ^jwτ + e ^-jwτ ) e ^-jwτ

= (1-2 kcosw?) E ^-jw ? … ②

It is expressed as Therefore, the frequency characteristics of the cosine waveform equalizer have cosine characteristics.

Considering τ = T here, it can be seen that since the maximum recording frequency of the signal recorded in NRZ is (1/2) T, the high pass signal has a large gain and the low pass signal has a small gain. In other words, the cosine waveform equalizer plays a role of emphasizing the high frequency signal using this characteristic.

The delay coefficient τ of the first delay unit 10 and the second delay unit 20 controls the frequency of the signal to be corrected, and the first amplitude adjusting unit 30, the second amplitude adjusting unit 40, and the third amplitude The amplitude adjustment coefficient k of the adjustment unit 50 acts as an element for determining the correction amplitude of the signal. 2 shows the correction amplitude of the signal for the case where k is 0, 1/2, 1/4.

However, the conventional cosine waveform equalizers have fixed amplitude adjustment coefficient k and time delay coefficient τ, so that the absolute correction of the same amount is performed in both the inner and outer parts of the disk. When rotating in the form of Angular Velocity (CAV), the intersymbol interference occurs in the inner circumference rather than the outer circumference of the disk. There was a problem that the noise of the increased.

Accordingly, in order to solve the above problems, the present invention provides a waveform equalization method of an optical disc drive for performing waveform equalization by adjusting the amplitude adjustment coefficient according to the radius of the disc to faithfully reproduce the original signal when the recorded data is reproduced. It is.

In order to achieve the above object, the waveform equalization method of an optical disc drive according to the present invention is a method for equalizing a signal read out from an optical disc and reproduced according to which radial portion of the disc is equalized according to which radial portion of the disc has been recorded. An amplitude adjustment coefficient setting process for setting an amplitude adjustment coefficient required for the operation; A delay process for delaying the reproduction signal for a predetermined time and then again for a predetermined time; An amplitude adjustment process for adjusting the amplitudes of the playback signal, the first delayed playback signal and the second delayed playback signal in accordance with the amplitude adjustment coefficient set in the amplitude adjustment coefficient setting process; And an addition process for adding the reproduction signal whose amplitude is adjusted, the reproduction signal that is first delayed in the delay process, and the reproduction signal that is secondary delayed.

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

3 is a block diagram of a waveform equalizing device for explaining a waveform equalizing method of an optical disk drive according to the present invention.

The block diagram shown in FIG. 3 includes a first delay unit 10 for delaying the input signal V _i by τ and a second delay unit for delaying the output signal of the first delay unit 10 by τ again. a second amplitude adjusting section for adjusting an amplitude of the delay section 20 and the input signal V _i, and adjusting the amplitude of the output signal of the first amplitude adjuster 30, a first delay unit (10) for reversing ( 40, the third amplitude adjustment unit 50 for adjusting and inverting the amplitude of the output signal of the second delay unit 20, and the output signal and the second amplitude adjustment unit 40 of the first amplitude adjustment unit 30. And the control unit 100 for controlling the first amplitude adjusting unit 30 and the third amplitude adjusting unit 50. Is done.

In addition, the controller 100 includes a digital / analog converter 70 for converting a digital control signal output from the microprocessor or the ROM 80 into an analog signal.

The operation of the present invention will now be described with reference to FIG.

The basic operation of the present invention shown in FIG. 3 is the same as the conventional one shown in FIG. 1, except that the amplitude adjusting portion is not performed uniformly, but is excessive in the waveform equalizing device by varying the adjustment width according to the radius of the disk. It is characterized by not giving high frequency emphasis.

That is, the degree to which the equalization characteristics of the portion to be read out from the disk, which is the recording medium, is to be extracted from the microprocessor or the ROM 80 and output to the digital / analog converting section 70. ) Is converted into an analog signal and applied to the first amplitude adjusting unit 30 and the third amplitude adjusting unit 50.

In the voltage control amplifier (VCA) in the first amplitude adjusting unit 30 and the third amplitude adjusting unit 50, the input signal V _i and the first delay unit The gain of the output signal of 10 and the output signal of the second vibration unit 20 are adjusted.

In this case, the required gain value should be determined in advance by the pickup of the optical disk drive, and the value should be equalized according to the radius of the disk. That is, in the innermost periphery of the disk C _jn attenuation value is close to 1/2, to be set such that the outer peripheral portion toward the attenuation C _jn value is close to zero. If the attenuation amount C _jn is 0, there is no gain with frequency.

If you know the current track number even during seek, you can see the information stored in the ROM table to see how much the signal level ratio (referred to as modulation) of the track you want to move is the equalizer. How much equalization coefficient is needed to eliminate waveform interference of high frequency and low frequency? If the amplitude of the equalizer is adjusted by outputting data corresponding to the equalization coefficient at this time, signal interference is eliminated without distortion of signal. can do.

As described above, the waveform equalization method of the optical disc drive according to the present invention has the advantage that the reproduction signal can be faithfully corrected regardless of the radius of the disc on which the signal is recorded by adjusting the amplitude adjustment coefficient according to the radius of the disc.

Claims (4)

CLAIMS 1. A method for equalizing a signal read out from an optical disc and reproduced, comprising: an amplitude adjustment coefficient setting step for setting an amplitude adjustment coefficient required for equalization according to which radial portion of the disc the reproduction signal has been recorded; A delay process for delaying the reproduction signal for a first predetermined time and again for a second predetermined time; An amplitude adjustment process for adjusting the amplitudes of the playback signal, the first delayed playback signal and the second delayed playback signal in accordance with the amplitude adjustment coefficient set in the amplitude adjustment coefficient setting process; And an addition process for adding the reproduced signal whose amplitude is adjusted, the reproduced signal delayed first in the delay process, and the reproduced signal delayed second in the delay process. The waveform equalization method of claim 1, wherein the amplitude adjustment coefficient setting process decreases the amplitude adjustment coefficient from an inner circumference to an outer circumference of the disk. The method of claim 1, wherein the amplitude adjustment process stores the amplitude adjustment coefficient according to the radius of the disk in a microprocessor or ROM table and extracts it if necessary, thereby reproducing the reproduction signal and the reproduction signal first delayed in the delay process. A waveform equalization method of an optical disc drive, characterized by adjusting the amplitude of a delayed reproduction signal. 4. The method of claim 3, wherein the amplitude adjustment process adjusts and inverts the amplitudes of the reproduction signal and the second delayed reproduction signal in the delay process, and adjusts only the amplitude of the primary delayed reproduction signal in the delay process. Waveform equalization method of optical disk drive.