KR100565711B1 - Signal Detecting Method and Apparatus Thereof in Magneto-optical Disc - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting a magneto-optical disk for improving the level of a reproduction signal read out by a pulsed laser readout method.

The method and apparatus for detecting a magneto-optical disk of the present invention focuses light on a recording medium, converts light reflected from the recording medium into an electrical signal, detects peak values of the signal converted into electrical signals, and detects peaks. Low pass filtering the signal.

According to the present invention, the signal level of the data reproduction signal can be improved by performing low pass filtering after peak detection of the first and second high frequency signals detected by the pulsed laser readout method. Accordingly, the signal-to-noise ratio of the data reproduction signal can be improved.

Description

Signal Detecting Method and Apparatus Thereof in Magneto-optical Disc

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting a signal of a magneto-optical disk, and more particularly, to a signal detecting method and apparatus for a magneto-optical disk to improve the level of a reproduction signal read out by a pulsed laser readout method. It is about.

Recently, ASMO (Advanced Storage Magneto Optical), which is an optical magnetic recording medium capable of having an excellent recording capacity compared to an existing optical recording medium, has been developed. The magneto-optical recording medium records information in a recording method using magnetic field modulation using a magnetic head, and adopts a method of detecting a change in polarization angle according to a photo-magnetic conversion characteristic by using an optoelectronic device when information is reproduced. . Such a magneto-optical recording medium is expected to increase in capacity from 6GB to 14GB in the future.

Magneto-optical discs adopting the CAD-MACR method are reproduced by a so-called "Pulsed Laser Readout" reproduction method. This method reproduces the information recorded on the disc by detecting a change in the polarization angle by using a photoelectric element that irradiates a laser pulse to the disc recording surface and receives the light beam reflected from the disc as shown in FIG.

1 is a block diagram schematically showing a signal detection method and apparatus of a conventional magneto-optical disk. In the configuration of FIG. 1, a conventional method and apparatus for detecting a signal of a magneto-optical disk includes a pickup 30 for irradiating light to the disk and converting the reflected light reflected from the disk into an electrical signal, and a light source of the pickup 30. A laser driver 32 for supplying a laser pulse to the signal, and a signal detector for detecting the tracking error signal Te, the focusing error signal Fe, and the high frequency signal RF from the photoelectrically converted signals from the pickup 30. 40 and I / V conversion & low pass filter (hereinafter, " LPF ") for low-pass filtering as well as current / voltage conversion of tracking error signal Te, focusing error signal Fe, and high frequency signal RF. 34, a servo driver 36 for performing tracking servo and focusing servo by the low pass filtered tracking error signal LTe and the focusing error signal LFe, and a low pass filtered high frequency signal Amplifying LRF to a Gain and Equalizing RF amplification & equalization section 38 is provided.

The pickup 30 includes a light source 2 for generating light as shown in FIG. 2, an objective lens 10 for condensing incident light beams on a signal track of the disk 100, and a reflected light beam reflected from the disk 100. A four-segment photodetector 14 for photoelectric conversion and photodetectors 24 and 28 for RF detection, a collimating lens 4 for converting light incident from the light source 2 into parallel light, and a collimating lens 4 And a first beam splitter 6 provided between the objective lens 10 and the second beam splitter 8 provided between the first beam splitter 6 and the objective lens 10 and a second beam splitter ( 8) and a phase delay unit 18 and a third beam splitter 20 which are provided between the first and second RF detection photodetectors 24 and 28, respectively. The light source 2 generates light by the laser pulse LDP as shown in FIG. 3 supplied from the laser driver 32. The collimating lens 4 is installed between the light source 2 and the first beam splitter 6 so as to convert the light generated from the light source 2 into parallel light and transmit it toward the first beam splitter 6. The light beam transmitted through the collimating lens 4 is sequentially transmitted through the first and second beam splitters 6 and 8 and collected by the objective lens 10 on the disk 100. The light beam focused on the disk 100 is reflected to back the optical path. The reflected light beam is partially reflected by the second beam splitter 8 and transmitted by the others. The reflected light beam reflected by the second beam splitter 8 is delayed in accordance with the polarization direction by the phase delay unit 18. The light beams passing through the phase delay unit 18 are incident on the third beam splitter 20 as two light beams out of phase with each other. The light beam incident on the third beam splitter 20 is transmitted or reflected according to the polarization direction and is incident on each of the first and second RF detectors 24 and 28. Accordingly, the first and second RF detectors 24 and 28 receive reflected light having respective polarization directions out of phase by the phase delayer 18 and are converted into electrical signals. These phase delayed signals are differentially amplified by the signal detector 40 and used to detect the boundary portion in which the magnetization direction changes in the recording film of the disc 100.

On the other hand, the reflected light beam transmitted from the second beam splitter 8 is totally reflected toward the four-segment photodetector 14 by the first beam splitter 6. The reflected light beam reflected by the first beam splitter 6 is incident on the quadrant photodetector 14 and converted into an electrical signal.

In the signal detecting method and apparatus of the magneto-optical disk of FIG. 1, the signal detecting unit 40 is composed of the servo signal detecting unit 41 shown in FIG. 4 and the high frequency signal detecting unit 42 shown in FIG.

Referring to Fig. 4, a first addition amplifier 43 connected to second and fourth photodetector pieces B and D in a diagonal direction with respect to the track direction, and first and third in a diagonal direction with respect to the track direction. A second adder amplifier 44 connected to the photodetector pieces A and C, a first differential amplifier 47 commonly connected to the output terminals of the first and second adder amplifiers 43 and 44, and A third adder amplifier 45 connected to the second and third photodetector pieces B and C, a fourth adder amplifier 46 connected to the first and fourth photodetector pieces A and D, and A servo signal detector 41 is shown having a second differential amplifier 48 commonly connected to the output terminals of the third and fourth adder amplifiers 45 and 46. The first addition amplifier 43 sums the output signals of the second and fourth photodetector pieces B and D, and the second addition amplifier 44 is the first and third photodetector pieces A and C. The output signals are summed. The first differential amplifier 47 differentially amplifies the output signals of the first and second addition amplifiers 43 and 44 to generate the focusing error signal Fe. The third addition amplifier 45 sums the output signals of the second and third photodetector pieces B and C, and the fourth addition amplifier 46 is the first and fourth photodetector pieces A and D. The output signals are summed. The second differential amplifier 48 differentially amplifies the output signals of the third and fourth add amplifiers 45 and 46 to generate the tracking error signal Te. The focusing error signal Fe and the tracking error signal Te are supplied to the I / V conversion & LPF 34.

Referring to FIG. 5, a high frequency signal detector 42 includes a differential amplifier 49 for differentially amplifying an output signal of the first RF detection photodetector 24 and an output signal of the second RF detection photodetector 28. ) Is shown. The output signal of the first RF detector photodetector 24 is a first high frequency signal whose phase is not delayed, and the output signal of the second RF detector photodetector 28 is delayed a predetermined time from the first high frequency signal to provide a phase difference. Branch is a signal. The differential amplifier 49 differentially amplifies the first and second high frequency signals, outputs a high frequency signal RF of FIG. 3, and supplies the same to the I / V conversion & LPF 34.

The I / V conversion & LPF 34 removes the noise component of the high frequency band by converting the focusing error signal Fe, the tracking error signal Te, and the high frequency signal RF supplied to the voltage signal and performing low pass filtering. Done. Here, the low pass filtered high frequency signal LPF is shown in FIG. 3.

The servo driver 36 controls the actuator 11 by the low pass filtering focusing error signal LFe so that the light spot condensed from the objective lens 10 falls within the depth of focus. In addition, the servo driver 36 controls the actuator 11 by the low pass filtered tracking error signal LTe so that the light spot collected from the objective lens 10 follows the track center. The RF amplification & equalizing unit 38 amplifies and equalizes the low pass filtered high frequency signal LRF to read out the reproduction signal.

As shown in FIG. 6, the conventional method and apparatus for detecting a signal of a conventional magneto-optical disk include an average of peak values of a low pass filtered high frequency signal (LRF), a focusing error signal (LFe), and a tracking error signal (LTe). There is a problem that the power value is significantly lowered. This causes the signal-to-noise ratio (S / N) of the reproduction signal and the servo signal detected by the signal detection device of the magneto-optical disc to drop.

Accordingly, it is an object of the present invention to provide a signal detection method and apparatus for an optical magnetic disk to improve the signal level of a data reproduction signal.

It is another object of the present invention to provide a signal detection method and apparatus for an optical magnetic disk to improve the signal level of a servo signal.

In order to achieve the above objects, a signal detecting method of a magneto-optical disk according to the present invention comprises the steps of condensing light on a recording medium to convert the light reflected from the recording medium into an electrical signal, and the conversion of the signal converted into an electrical signal Detecting a peak value and low pass filtering the peak detected signal.

A signal detecting apparatus for a magneto-optical disk according to the present invention includes a light source / optical system for condensing light on a recording medium, a light detecting device for converting light reflected from the recording medium into an electrical signal, and a peak value of the signal converted into an electrical signal. And a low pass filter for low pass filtering the peak detected signal.

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. 7 to 17.

7 is a block diagram illustrating an apparatus for reproducing data and detecting a servo signal of an optical magnetic disc according to an exemplary embodiment of the present invention.

7, the data reproducing and servo signal detecting apparatus of the magneto-optical disk according to the present invention includes a pickup 30 for irradiating light to the disk and converting the reflected light reflected from the disk into an electrical signal; A laser driver 62 for supplying a laser pulse to the light source of the light source 30, a peak detector 90 for peak detection of signals photoelectrically converted from the pickup 30, and a peak detector 90 of the peak detector 90. A signal detector 70 for detecting the tracking error signal Te, the focusing error signal Fe and the high frequency signal RF by signal processing the output signal, the tracking error signal Te, the focusing error signal Fe, Tracking servo by I / V conversion & LPF 64 for low pass filtering as well as current / voltage conversion of high frequency signal RF, and low pass filtered tracking error signal LTe and focusing error signal LFe And a servo driver for performing focusing servo And an RF amplification & equalization unit 68 for amplifying the low pass filtered high frequency signal LRF to a predetermined gain value and equalizing the same.

Pick-up 30 is substantially the same as in Fig. 1, detailed description thereof will be omitted. The laser driver 62 generates a laser pulse LDP according to a reference clock supplied thereto, and supplies the laser pulse LDP to a laser diode which is a light source of the pickup 30. The signal detection unit 70 includes a servo signal detection unit 71 shown in FIG. 8 and a high frequency signal detection unit 72 shown in FIG. The peak detector 90 is connected between the pickup 30 and the signal detector 70 to output the four-segment photodetector 14 of the pickup 30 and the first and second RF detectors 24 and 28. The peaks are detected by the signals and supplied to the signal detector 70. The peak detector 90 includes a servo signal peak detector 91 and a high frequency signal peak detector 92.

FIG. 8 is a circuit diagram illustrating in detail the servo signal peak detector and the servo signal detector of the signal detector shown in FIG. 7.

In the configuration of FIG. 8, the servo signal peak detector 91 includes a first peak detector 93 connected to the second photodetector B and a second peak detector (connected to the first photodetector A). 94), a third peak detector 95 connected to the fourth photodetector piece D, and a fourth peak detector 96 connected to the third photodetector piece C. The servo signal detector 71 includes a first addition amplifier 73 connected to the first and third peak detectors 93 and 95 and a second addition amplifier connected to the second and fourth peak detectors 94 and 96. (74), a first differential amplifier (77) commonly connected to the output terminals of the first and second adder amplifiers (73, 74), and a first connected to the first and fourth peak detectors (93, 96). The third addition amplifier 75, the fourth addition amplifier 76 connected to the second and third peak detectors 94 and 95, and the output terminals of the third and fourth addition amplifiers 75 and 76 in common. A second differential amplifier 78 is connected. The first peak detector 93 detects the peak of the output signal of the second photodetector B. The second peak detector 94 performs peak detection on the output signal of the first photodetector piece A. FIG. The third peak detector 95 performs peak detection of the output signal of the fourth photodetector piece D. FIG. The fourth peak detector 96 detects the peak of the output signal of the third photodetector C. When the output signals of the first to fourth light detecting pieces A to D are as shown in FIG. 10, the signal is as shown in FIG. 11 when the first to fourth peak detectors 93 to 96 are detected.

The first addition amplifier 73 sums the output signals of the first and third peak detectors 93 and 95, and the second addition amplifier 74 outputs the output signals of the second and fourth peak detectors 94 and 96. To sum them up. The first differential amplifier 77 differentially amplifies the output signals of the first and second addition amplifiers 73 and 74 to generate the focusing error signal Fe. The third add amplifier 75 sums the output signals of the first and fourth peak detectors 93 and 96, and the fourth add amplifier 76 outputs the output signals of the second and third peak detectors 94 and 95. To sum them up. The second differential amplifier 78 generates a tracking error signal Te by differentially amplifying the output signals of the third and fourth add amplifiers 75 and 76. The focusing error signal Fe and the tracking error signal Te are supplied to the I / V conversion & LPF 64.

FIG. 9 is a circuit diagram illustrating in detail the high frequency signal peak detector of the peak detector and the high frequency signal detector of the signal detector shown in FIG. 7.

In the configuration of Fig. 9, the high frequency signal peak detector 92 has a fifth peak detector 97 connected to the first RF detector photodetector 24, and a second peak detector 97 connected to the second RF detector photodetector 28. 6 peak detector 98 is provided. The high frequency signal detector 72 includes a differential amplifier 79 that differentially amplifies the output signal of the fifth peak detector 97 and the output signal of the sixth peak detector 98. The output signal of the first RF detector photodetector 24 is a first high frequency signal whose phase is not delayed, and the second RF detector photodetector 28 is delayed a predetermined time from the first high frequency signal and has a second phase difference. It is a high frequency signal. The fifth peak detector 97 detects the first high frequency signal and the sixth peak detector 98 detects the second high frequency signal. When the first and second high frequency signals are the same as in FIG. 10, the signal becomes as shown in FIG. 11 when the peaks are detected by the fifth and sixth peak detectors 97 and 98. The differential amplifier 79 differentially amplifies the first and second high frequency signals to generate a high frequency signal RF. This high frequency signal RF is supplied to the I / V conversion & LPF 64.

The I / V conversion & LPF 64 removes the noise component of the high frequency band by converting the focusing error signal Fe, the tracking error signal Te, and the high frequency signal RF supplied to the voltage signal and performing low pass filtering. Done. Here, since the input signals of the I / V conversion & LPF 64 are peak detected by the peak detector 90, when these signals are low pass filtered, signals that are not conventionally peak detected are compared with those of the low pass filtered signals. The noise to noise ratio becomes high. When the output signals of the peak detector 90 are low pass filtered, a waveform as shown in FIG. 12 may be obtained. The LRF, LFe, and LTe are low pass filtered high frequency signals, focusing error signals, and tracking error signals, respectively.

The servo driver 66 controls the actuator 11 by the low pass filtered focusing error signal LFe so that the light spot condensed from the objective lens 10 falls within the depth of focus. In addition, the servo driver 66 controls the actuator 11 by the low pass filtered tracking error signal LTe so that the light spot condensed from the objective lens 10 follows the track center. The servo driver 66 controls the actuator 11 by appropriately adjusting the low pass filtered focusing error signal LFe and tracking error signal LTE. Here, since the peak-detected signals are low-pass filtered for the low-pass filtered focusing error signal LFe and the tracking error signal LTE, the output signals of the conventional four-segment photodetector 14 are directly low-pass filtered and low-pass filtered. The signal-to-noise ratio is improved against the signals. Accordingly, since the noise component is minimized in the low pass filtered focusing error signal LFe and the tracking error signal LTe, the servo driver 66 may drive the servo with the correct focusing error signal and the tracking error signal.

The RF amplification & equalization unit 68 amplifies and equalizes the low pass filtered high frequency signal LRF to serve to read out the reproduction signal. Here, since the low-pass filtered high frequency signal LRF is low-pass filtered, the output signals of the first and second RF detectors 24 and 28 are directly low-pass filtered and low-pass filtered. The signal-to-noise ratio is improved against the signals. Accordingly, the data reproduced by the RF amplification & equalization unit 68 is minimized in noise components.

In fact, when comparing the low pass filtered output signals according to the peak detection of the input signal as follows.

Referring to FIG. 13, there is shown a low pass filter 69 composed of a resistor R1 connected in series to an input signal source Vi, and a capacitor C1 connected between a resistor R1 and a ground voltage source GND. It is. Here, the resistor R1 is set to 50 mA and the capacitor C1 to 2 pF, respectively. The input signal source Vi generates an input pulse of 1.0 V and 40 MHz as shown in FIG. When the input pulse passes through the low pass filter 69, the output node n2 detects a signal having a peak level of approximately 200 mv as shown in FIG.

Referring to FIG. 14, a peak detector including a diode D connected in series to an input signal source Vi, a capacitor C2 and a resistor R2 connected in parallel between the diode D and the ground voltage source GND. (99), a low pass filter (69) consisting of a resistor (R1) connected in series with the output terminal of the peak detector (99), and a capacitor (C1) connected between the resistor (R1) and the ground voltage source (GND). It is. Here, the resistor R2 constituting the peak detector 99 is set to 10 k? And the capacitor C2 is set to 100 pF, respectively. The input signal source Vi generates an input pulse of 1.0 V and 40 MHz as shown in FIG. When the input pulse passes through the peak detector 99, the node n1 detects a signal having a peak level of approximately 500 mV as shown in Fig. 17A. When the output signal of the peak detector 99 passes through the low pass filter 69, the output node n2 detects a signal having a peak level of approximately 400mv as shown in FIG. 17B. Therefore, it can be confirmed that the signal level is approximately two times or more different depending on whether the peak is detected.

As a result, the data reproducing method and apparatus of the magneto-optical disk and the servo signal detecting method and apparatus according to the present invention peak-detect the output signals of the photodetectors 14, 24 and 28 and perform low pass filtering to improve the level of the reproduction signal. The signal-to-noise ratio of the data reproduction signal and the servo signal can be improved by improving the noise component included in the reproduction signal.

As described above, the method and apparatus for detecting a magneto-optical disk according to the present invention by low-pass filtering the first and second high-frequency signals detected by the pulsed laser readout method The signal level of the data reproduction signal can be improved. Accordingly, the signal-to-noise ratio of the data reproduction signal can be improved. The signal detecting method and apparatus of the magneto-optical disk according to the present invention can improve the signal level of the servo signal by performing low pass filtering after peak detection of the output signals of the light splitting pieces of the four-segment photodetectors. Accordingly, the signal-to-noise ratio of the servo signal can be improved.

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.

1 is a block diagram showing a signal detection method and apparatus of a conventional magneto-optical disk.

FIG. 2 shows details of the pickup shown in FIG. 1; FIG.

3 is an output waveform diagram of each part shown in FIG. 1;

4 is a circuit diagram illustrating a servo signal detector in detail in the signal detector illustrated in FIG. 1;

FIG. 5 is a circuit diagram illustrating in detail a high frequency signal detector in the signal detector illustrated in FIG.

FIG. 6 is a voltage waveform diagram illustrating an output waveform of the signal detector of FIG. 1 and an output waveform of an I / V conversion & low pass filter. FIG.

7 is a block diagram showing an apparatus for detecting a signal of a magneto-optical disk according to an embodiment of the present invention.

FIG. 8 is a circuit diagram showing in detail a servo signal detector of a signal detector and a servo signal peak detector of a peak detector shown in FIG.

FIG. 9 is a circuit diagram illustrating in detail the high frequency signal detection unit of the signal detection unit and the high frequency signal peak detection unit of the peak detection unit shown in FIG.

10 is an output waveform diagram of a photoelectric conversion element in the pickup shown in FIG.

FIG. 11 is a waveform diagram illustrating peak detection of output signals of a photoelectric conversion element as shown in FIG. 10.

12 is an output waveform diagram of a peak detector and a signal detector shown in FIG. 7;

13 is a circuit diagram showing a low pass filter for experiments.

14 is a circuit diagram showing a peak detector and a low pass filter for experiments.

15 is a waveform diagram illustrating input pulses of the circuits of FIGS. 13 and 14.

FIG. 16 is an output waveform diagram of a low pass filter shown in FIG. 13; FIG.

17A is an output waveform diagram of the peak detector shown in FIG.

17B is an output waveform diagram of a low pass filter shown in FIG. 14.

Explanation of symbols for the main parts of the drawings

2: light source 4: collimating lens

6,8,20: beam splitter 10: objective lens

11: actuator 14: 4-split photodetector

16: polarizer 18: phase delay

24,28: RF photodetector 30: pickup

32,62: Laser driver 34,64: I / V conversion & low pass filter

36,66: Servo Driver 38,68: RF Amplification & Equalizer

40,70: signal detector 41,71: servo signal detector

42,72: high frequency signal detector 43-46,73-76: addition amplifier

47-49,77-79: differential amplifier 69: low pass filter

90: peak detector 91: servo signal peak detector

92: high frequency signal peak detector 93 to 99: peak detector

Claims (18)

Condensing light on the recording medium to convert the light reflected from the recording medium into an electrical signal; Detecting a peak value of the signal converted into the electrical signal; And low pass filtering the peak-detected signal. The method of claim 1, The signal is a signal detection of a magneto-optical disc, characterized in that the first and second high-frequency signals phase-delayed by condensing the light on the recording medium, phase-delayed the light reflected from the recording medium, and then converted into an electrical signal Way. The method of claim 2, Differentially amplifying the first and second high frequency signals to detect the high frequency signals; Converting the high frequency signal into a voltage signal; And amplifying the low pass filtered signal by a predetermined gain value to equalize the low pass filtered signal. The method of claim 1, And detecting a focusing error signal indicating a degree to which the focused light deviates from a depth of focus using the peak detected signal. The method of claim 4, wherein The detecting of the focusing error signal may include adding signals in a diagonal direction with respect to a track direction of the recording medium; And differentially amplifying the sum signal in the diagonal direction. The method of claim 4, wherein And driving the objective lens in a focusing direction by using the focusing error signal. The method of claim 1, And detecting a tracking error signal indicating a degree to which the focused light deviates from the center of a track by using the peak detected signal. The method of claim 7, wherein The detecting of the tracking error signal may include summing signals parallel to the track direction of the recording medium; And differentially amplifying the sum signal. The method of claim 7, wherein And driving the objective lens in the tracking direction by using the tracking error signal. A light source / optical system for condensing light on the recording medium, A photodetector for converting light reflected from the recording medium into an electrical signal; Peak detection means for detecting a peak value of the signal converted into the electrical signal; And a low pass filter for low pass filtering the peak detected signal. The method of claim 10, The signal is a signal detection of a magneto-optical disc, characterized in that the first and second high-frequency signals phase-delayed by condensing the light on the recording medium, phase-delayed the light reflected from the recording medium, and then converted into an electrical signal Device. The method of claim 11, A differential amplifier for differentially amplifying the first and second high frequency signals to detect the high frequency signals; A current / voltage converter for converting the high frequency signal into a voltage signal; And an equalizer which amplifies the low pass filtered signal by a predetermined gain value and equalizes the low pass filtered signal. The method of claim 10, And a servo signal detecting means for detecting a focusing error signal indicating a degree to which the focused light is out of a depth of focus by using the peak detected signal. The method of claim 13, The servo signal detecting means includes an adder amplifier for adding up signals in a diagonal direction with respect to a track direction of the recording medium; And a differential amplifier for differentially amplifying the sum signal in the diagonal direction. The method of claim 13, And a servo drive means for driving the objective lens in the focusing direction by using the focusing error signal. The method of claim 10, And a servo signal detecting means for detecting a tracking error signal indicating a degree of deviation of the focused light from the center of the track by using the peak detected signal. The method of claim 16, The servo signal detecting means includes an adder amplifier for summing signals parallel to the track direction of the recording medium; And a differential amplifier for differentially amplifying the sum signal. The method of claim 16, And a servo drive means for driving the objective lens in the tracking direction by using the tracking error signal.