JP3461133B2 - Information recording / reproducing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus for a magneto-optical recording medium which reproduces a signal by expanding a magnetic domain.

[0002]

2. Description of the Related Art Magneto-optical recording media have been attracting attention as rewritable recording media having a large storage capacity and high reliability, and are being put to practical use as computer memories and the like. In addition, recently, the recording capacity is 6.1 Gby.
The standardization of tes magneto-optical recording media is also in progress.

Further, a magnetic domain expansion reproducing technique has been developed in which an alternating magnetic field is applied in reproducing a signal from a magneto-optical recording medium and a magnetic domain transferred from the reproducing layer to the recording layer is expanded by the alternating magnetic field to reproduce a signal. A magneto-optical recording medium capable of recording and / or reproducing a signal of 14 Gbytes by using this technique has also been proposed.

In signal reproduction using the magnetic domain expansion reproduction technique, the magnetic domain of the recording layer in which the signal is recorded is transferred to the reproduction layer, and the transferred magnetic domain is expanded and reproduced by an alternating magnetic field applied from the outside. It is what is done. In this case, a low frequency “waviness” occurs in the reproduction waveform 280 as shown in FIG. 28 due to the influence of the birefringence distribution of the substrate of the magneto-optical recording medium, the tilt of the substrate, and the like. Conventionally, a high-pass filter has been used to remove such low-frequency "waviness".

[0005]

However, there is a problem that the high-pass filter cannot sufficiently remove the low frequency component.

Therefore, the present invention solves such a problem, and even if the birefringence of the substrate of the magneto-optical recording medium has a distribution,
An object of the present invention is to provide an information recording / reproducing apparatus capable of outputting a reproduction signal which does not include a low-frequency "waviness" even if the substrate is tilted.

[0007]

Means and Effect of the Invention for Solving the Problems claims
1 reproduces a signal by expanding a magnetic domain from a magneto-optical recording medium
The present invention relates to an information recording / reproducing device.

The information recording / reproducing apparatus uses the magneto-optical recording
The first magnetic field that expands the magnetic domain in the medium and the expanded magnetic domain
Magnetic head for applying a second magnetic field to be erased at a predetermined cycle
And irradiating the magneto-optical recording medium with a laser beam,
An optical head for detecting reflected light from the magneto-optical recording medium,
Generates an external sync signal based on the output from the optical head.
And an external synchronization signal generation circuit for generating the external synchronization signal
Delay circuit that delays the external synchronization signal from the circuit by a fixed amount
And input the external synchronization signal delayed by the delay circuit
And the frequency of the delayed external synchronization signal is multiplied
And a reproduction signal detection circuit.

The reproduction signal detecting circuit is the optical head.
The playback signal detected by the
The A / D converter for converting into a signal and the A / D converter
Synchronize the signal converted to digital signal with the sync signal
Shift register for delaying by a certain amount, and the A / D converter
The signal output by the converter and the shift register
And the signal output by the shift register
Output from the signal output by the A / D converter
And a subtractor for subtracting the received signal.

Further , the reproduction signal detecting circuit includes the first
The magnetic field of, and when the second magnetic field is applied
Received the signal detected by the optical head and received it
, In synchronization with the sync signal input from the multiplier circuit,
The strength when the first magnetic field is applied and the second magnetic field
And the strength when the voltage is applied, and the detected strength
Is output as a reproduction signal.

According to the invention described in claim 1, the magnetic domain
Was detected at the timing when the magnetic field for enlarging
Mark the playback signal and the magnetic field to erase the magnified domains.
Calculate the difference with the playback signal detected at the added timing
However, since the difference is output as a reproduction signal,
Swelling of reproduced signal caused by tilt of recording medium
Can be removed.

The multiplier circuit inputs the external synchronizing signal delayed by the delay circuit and multiplies the frequency of the delayed external synchronizing signal.

According to a second aspect , the magnetic domain is expanded from the magneto-optical recording medium.
The invention relates to an information recording / reproducing apparatus for reproducing a signal.
It

The information recording / reproducing apparatus is the magneto-optical recording device.
The first magnetic field that expands the magnetic domain in the medium and the expanded magnetic domain
Magnetic head for applying a second magnetic field to be erased at a predetermined cycle
And irradiating the magneto-optical recording medium with a laser beam,
An optical head for detecting reflected light from the magneto-optical recording medium,
Generates an external sync signal based on the output from the optical head.
And an external synchronization signal generation circuit for generating the external synchronization signal
First delay for delaying the external synchronization signal from the circuit by a fixed amount
Circuit and external synchronization delayed by the first delay circuit
Input signal and multiply the frequency of delayed external sync signal
And a reproduction signal detection circuit.

The reproduction signal detecting circuit is the optical head.
Second delay circuit for delaying the reproduction signal detected by
And the signal output by the second delay circuit
The synchronization signal output by the external synchronization signal generation circuit
An A / D converter for synchronously converting into a digital signal;
The signal converted to a digital signal by the A / D converter is forwarded
A shift register that delays a fixed amount in synchronization with the synchronization signal
And a signal output by the A / D converter,
Input the signal output from the
A / D conversion from the signal output by the shift register
And a subtractor that subtracts the signal output by the converter.

Further , the reproduction signal detection circuit includes the first
The magnetic field of, and when the second magnetic field is applied
Received the signal detected by the optical head and received it
, In synchronization with the sync signal input from the multiplier circuit,
The strength when the first magnetic field is applied and the second magnetic field
And the strength when the voltage is applied, and the detected strength
The difference is output as a reproduction signal.

According to the invention described in claim 2, the magnetic domain
Was detected at the timing when the magnetic field for enlarging
Mark the playback signal and the magnetic field to erase the magnified domains.
Calculate the difference with the playback signal detected at the added timing
However, since the difference is output as a reproduction signal,
Swelling of reproduced signal caused by tilt of recording medium
Can be removed.

According to a third aspect, the magnetic domain is expanded from the magneto-optical recording medium.
The invention relates to an information recording / reproducing apparatus for reproducing a signal.
It

The information recording / reproducing apparatus is the magneto-optical recording device.
The first magnetic field that expands the magnetic domain in the medium and the expanded magnetic domain
Magnetic head for applying a second magnetic field to be erased at a predetermined cycle
And irradiating the magneto-optical recording medium with a laser beam,
An optical head for detecting reflected light from the magneto-optical recording medium,
Generates an external sync signal based on the output from the optical head.
The external sync signal generation circuit and the reproduction signal detection circuit
Including.

The reproduction signal detecting circuit is the optical head.
First delay circuit for delaying a reproduction signal detected by a certain amount
And the reproduction signal detected by the optical head and the first reproduction signal.
Calculates and amplifies the difference from the signal delayed by the delay circuit
Differential amplifier and a signal output by the differential amplifier
And a comparator that
A fixed amount of the signal that is compared by the comparator
A second delay circuit for delaying and a second delay circuit
Output the delayed signal from the external sync signal generation circuit.
The D-floor that holds in synchronization with the applied external synchronization signal
Including lip flop.

Further , the reproduction signal detecting circuit is provided with the first
The magnetic field of, and when the second magnetic field is applied
Received the signal detected by the optical head and received it
The same as the external sync signal from the external sync signal generation circuit.
In addition, the intensity when the first magnetic field is applied and the
The strength when the second magnetic field is applied and the
The difference in the output intensity is output as a reproduction signal.

According to the invention described in claim 3, reproduction is performed.
The signal detection circuit is an external synchronization signal generated by the external synchronization signal generation circuit.
The calculation for removing the undulation is performed in synchronization with the synchronization signal. Obey
The timing of the calculation for removing the swell.
It is possible to output a playback signal that is accurate and surely removes undulations.
It According to the invention described in claim 3,
The signal detected by the monitor is delayed by a certain amount and then delayed
Binarize the signal. And with a D flip-flop
The timing of dropping the binary signal becomes "1".
And the timing at which it becomes “0”.
Input the external sync signal generated by the sync signal generator
The swell can be accurately removed from the reproduced signal only by performing.

According to a fourth aspect, the magnetic domain is expanded from the magneto-optical recording medium.
The invention relates to an information recording / reproducing apparatus for reproducing a signal.
It

The information recording / reproducing apparatus is the magneto-optical recording device.
The first magnetic field that expands the magnetic domain in the medium and the expanded magnetic domain
Magnetic head for applying a second magnetic field to be erased at a predetermined cycle
And irradiating the magneto-optical recording medium with a laser beam,
An optical head for detecting reflected light from the magneto-optical recording medium,
Generates an external sync signal based on the output from the optical head.
The external sync signal generation circuit and the reproduction signal detection circuit
Including.

The reproduction signal detection circuit is the optical head.
First delay circuit for delaying a reproduction signal detected by a certain amount
And the reproduction signal detected by the optical head and the first reproduction signal.
Calculates and amplifies the difference from the signal delayed by the delay circuit
Differential amplifier and a signal output by the differential amplifier
And a comparator that
The external sync signal from the external sync signal generator is delayed by a certain amount.
A second delay circuit for delaying the delay, and the second delay circuit
To the comparator in synchronization with the delayed external synchronization signal
D-flip to hold more compared signals
Including the flop.

Further , the reproduction signal detection circuit includes the first
The magnetic field of, and when the second magnetic field is applied
Received the signal detected by the optical head and received it
The same as the external sync signal from the external sync signal generation circuit.
In addition, the intensity when the first magnetic field is applied and the
The strength when the second magnetic field is applied and the
The difference in the output intensity is output as a reproduction signal.

According to the invention described in claim 4, reproduction is performed.
The signal detection circuit is an external synchronization signal generated by the external synchronization signal generation circuit.
The calculation for removing the undulation is performed in synchronization with the synchronization signal. Obey
The timing of the calculation for removing the swell.
It is possible to output a playback signal that is accurate and surely removes undulations.
It In addition, the D flip-flop outputs a fixed amount of external synchronization signal.
A binarized playback signal synchronized with the delayed sync signal
Hold, so hold with D flip-flop
By adjusting the timing, it is possible to ridge from the reproduced signal.
Can be reliably removed.

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[0080]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. With reference to FIG. 1, a cross-sectional structure of a magneto-optical recording medium targeted by the information recording / reproducing apparatus of the present invention will be described. The magneto-optical recording medium 1 includes a translucent substrate 2 made of polycarbonate or the like, an interference layer 3 made of SiN formed on the substrate 2, and GdFeC provided on the interference layer 3.
a reproducing layer 4 made of o, and SiN provided on the reproducing layer 4.
A non-magnetic layer 5 made of, and Tb provided on the non-magnetic layer 5.
The recording layer 6 made of FeCo, the protective layer 7 made of SiN provided on the recording layer 6, and the P provided on the protective layer 7.
and a heat dissipation layer 8 made of a metal such as Au. SiN forming the interference layer 3 and GdFeC forming the reproducing layer 4
Metals such as o, SiN forming the non-magnetic layer 5, TbFeCo forming the recording layer 6, SiN forming the protective layer 7, and Pt and Au forming the heat dissipation layer 8 are formed by magnetron sputtering. The interference layer 3 has a thickness of 30 to 100 nm, the reproducing layer 4 has a thickness of 5 to 100 nm,
The non-magnetic layer 5 is 1 to 100 nm, and the recording layer 6 is 50 to 300 nm.
nm, the protective layer 7 is 5 to 100 nm, and the heat dissipation layer 8 is 1 nm.
It is 0 to 100 nm. The interference layer 3 is provided to improve the magnetic characteristics of the reproducing layer 4 as compared with the case where the reproducing layer 4 is directly deposited on the substrate 2. In addition, the heat dissipation layer 8 has a small area in which the magnetic films of the reproducing layer 4 and the recording layer 6 are heated to a predetermined temperature or more when the signal is recorded on and / or reproduced from the magneto-optical recording medium 1. It is provided for recording or reproducing at a high density. The magneto-optical recording medium 1 is used as a medium for reproducing the magnetic domain of the recording layer 6 by transferring / enlarging the magnetic domain of the recording layer 6 to the reproducing layer 4, as will be described later.

The mechanism of magnetic domain expansion reproduction will be described with reference to FIG. When the magneto-optical recording medium 1 is irradiated with the laser beam 9 from the reproducing layer 4 side, the temperature of the region of the magnetic domain 50 of the recording layer 6 rises, and the leakage magnetic field from the magnetic domain 50 becomes stronger as the temperature rises. Normally, the magnetic domain 50 of the recording layer 6 is irradiated with a laser beam having such an intensity that it is transferred to the reproducing layer 4 via the non-magnetic layer 5 by a leakage magnetic field. However, in the present invention, the magnetic domain 50 is irradiated to the reproducing layer 4. Irradiate with a laser beam having an intensity that is not transferred. Therefore, in FIG. 2A, if the magneto-optical recording medium 1 is simply irradiated with the laser beam 9,
Since the magnetic domain is not transferred to the reproducing layer 4, the magnetic domain 30 having the magnetization in the same direction as the magnetization 51 of the magnetic domain 50 is indicated by a dotted line. Further, the reproducing layer 4 has an initialization magnetization 20 which is initialized in a predetermined direction in advance. Referring to FIG. 2B, in the alternating magnetic fields 10 and 11 from the outside in the same direction as the magnetization 51 of the magnetic domain 50 in a state where the region of the magnetic domain 50 is heated to a predetermined temperature or higher by irradiation with a laser beam. When the magnetic field 10 is applied, the enlarged magnetic domain 31 having the magnetization in the same direction as the magnetization 51 of the magnetic domain 50 appears in the reproducing layer 4. That is, the magnetic domain 50 is not transferred to the reproducing layer 4 by only irradiating the laser beam 9, but when the external magnetic field 10 is applied, the transfer and expansion of the magnetic domain 50 to the reproducing layer 4 occur continuously. The reproduced signal is detected in this expanded state. Next, referring to FIG. 2C, after detecting a signal from the expanded magnetic domain 31, a magnetic field 11 in the opposite direction to the magnetic field 10 used for transferring / enlarging the magnetic domain is applied to transfer / enlarge. The erased magnetic domain 31 is erased. Through the steps of (a), (b), and (c) of FIG. 2, the magnetic domain of the recording layer is transferred / enlarged to the reproducing layer 4 and reproduced.

The relationship between the alternating magnetic field applied to the magneto-optical recording medium 1 and the reproduced signal will be described with reference to FIG. Of the applied alternating magnetic field 12, the magnetic field indicated by reference numeral 10 is a magnetic field used for transferring and expanding the magnetic domain, and the magnetic field indicated by reference numeral 11 is a magnetic field used for erasing the magnetic domain. Alternating magnetic field 12
In the reproduced signal 13 detected corresponding to, a strong point 130 and a weak point 131 appear.

An information recording / reproducing apparatus according to the present invention will be described with reference to FIG. The information recording / reproducing apparatus irradiates the magneto-optical recording medium 1 with a laser beam and detects the reflected light thereof, an optical head 40, a reproducing signal amplifier circuit 41 for amplifying a signal from the optical head 40 to a predetermined value, and reproducing The servo circuit 42 receives the error signal from the signal amplification circuit 41, sends the focus error signal and the tracking error signal to the servo mechanism 43, and rotates the spindle motor 44 at a predetermined rotation speed and the magneto-optical recording medium 1 to a predetermined rotation. Spindle motor 44 that rotates by a number and optical head 40
Servo mechanism 43 for performing focus servo and tracking servo of the objective lens inside, and reproduction signal amplification circuit 4
1, a reproduction signal detection circuit 45 that detects a reproduction signal by a method described later, an external synchronization signal generation circuit 46 that generates an external synchronization signal based on the signal from the reproduction signal amplification circuit 41, and an external synchronization signal. A delay circuit 47 for delaying the external synchronizing signal from the generating circuit 46 for a fixed time, a delay circuit 57 for further delaying the external synchronizing signal delayed by the fixed time from the delay circuit 47 for a fixed time, and a delay from the delay circuit 57. A frequency multiplication circuit 58 that multiplies the frequency of the synchronization signal and outputs the multiplied synchronization signal to the reproduction signal detection circuit 45, and an application pattern of an alternating magnetic field that is applied to the magneto-optical recording medium 1 based on the signal from the delay circuit 47. , And a timing pulse generation circuit 48 for determining an irradiation pattern of a laser beam with which the magneto-optical recording medium 1 is irradiated, and a timing pulse generation circuit 4 The magnetic head 5 based on the signal from the
2, a magnetic head drive circuit 49 for driving the magneto-optical recording medium 1, a magnetic head 52 for applying an alternating magnetic field to the magneto-optical recording medium 1, and an optical for irradiating the magneto-optical recording medium 1 with a laser beam based on signals from the timing pulse generating circuit 48. And a laser drive circuit 56 for driving the semiconductor laser in the head 40.
Further, the timing pulse generating circuit 48 synchronizes with the signal from the delay circuit 47 on the basis of the recording signal modulated by a predetermined modulation method at the time of recording the signal.
Generate a timing signal for driving 2.

Referring to FIGS. 5, 6, 7, 8, 9, and 10,
Generation of the external synchronization signal in the external synchronization signal generation circuit 46 will be described. With reference to FIG. 5, a magneto-optical recording medium 1
The track has a groove 53 and a land 54, and the groove 53 is provided with discontinuous regions 55 at regular intervals. With reference to FIG. 6, the photodetection section 60 provided in the optical head 40 is divided into four regions, that is, an A region 61, a B region 62, a C region 63, and a D region 64, and is indicated by an arrow 65. The direction is set to the track direction, and the direction indicated by the arrow 66 is set to the tracking direction. The laser beam causes the groove 53 and the land 54 of the magneto-optical recording medium 1.
The reflected light is irradiated to the A area 61, the B area 62, and the C area.
It is detected in the area 63 and the D area 64. The sum [B + C] of the intensity [B] of the reflected light detected in the B region 62 and the intensity [C] of the reflected light detected in the C region 63 is input to one terminal of the adder 67, and the A region 61 Intensity [A] of the reflected light detected in step D and intensity [D] of the reflected light detected in area D 64
The sum [A + D] of and is input to the other terminal of the adder 67. Then, the adder 67 calculates the sum of the input [B + C] and [A + D], and [A + B + C + D] (a)
Is output. Referring to FIG. 7, since grooves 53 of magneto-optical recording medium 1 include discontinuous areas 55 at regular intervals, optical head 40 of FIG. The signal shown in (a) is output. The signal (a) output from the optical head 40 is amplified to a predetermined value by the reproduction signal amplification circuit 41, and then input to the external synchronization signal generation circuit 46. The external synchronization signal generation circuit 46 compares the input signal (a) with a predetermined reference to generate a binarized signal (b) and
An external synchronization signal (c) that is synchronized with the rising edge of the binarized signal (b) is generated. In this case, the external synchronization signal (c) is 2
There are 512 timings between the signal 70 and the signal 70 of the binarized signal (b).

In the above, the sum of the intensities of the reflected light detected in the four areas (A area 61, B area 62, C area 63, D area 64) of the photodetector 60 in the optical head 40 is detected. Although it has been described that the discontinuous area 55 provided in the groove 53 is detected by the above, the present invention is not limited to this, and FIG.
9 may be used. That is, referring to FIG.
Of the four areas of the light detection unit 60, the sum [B + C] of the reflected light intensity [B] detected in the B area 62 and the reflected light intensity [C] detected in the C area 63, and the A area The difference [[B + C] between the sum [A + D] of the reflected light intensity [A] detected at 61 and the reflected light intensity [D] detected at the D area 64.
A method of calculating − [A + D]] may be used. In this case, the sum signal [B + C] is input to one terminal of the subtractor 68, the sum signal [A + D] is input to the other terminal of the subtractor 68, and the difference signal [[B + C] − [A + D]] (aa) is input. Is calculated. As shown in FIG. 8, the sum [B + C] of the intensity [B] of the reflected light detected in the B region 62 and the intensity [C] of the reflected light detected in the C region 63, and the intensity detected in the A region 61. The method of calculating the difference between the sum [A + D] of the intensity [A] of the reflected light and the intensity [D] of the reflected light detected in the D area 64 can eliminate the influence of noise or the like, and the discontinuous area 55 This is because the position of can be detected more accurately. The difference signal (aa) detected by the method shown in FIG.
After being amplified to a predetermined value by the external synchronizing signal generating circuit 46
Sent to. Referring to FIG. 9, external synchronization signal generation circuit 4
Reference numeral 6 compares the sent difference signal (aa) with a predetermined reference to generate a binarized signal (b) and an external synchronization signal (c) synchronized with the rising edge of the binarized signal (b). ) Is generated. Also in this case, as in the case of FIG. 7, there is a signal 51 between the signal 70 and the signal 70 of the binarized signal (b).
External sync signal (c) so that there are two timings
Is generated.

With reference to FIG. 10, the structure and operation of external synchronizing signal generating circuit 46 will be described. The external synchronization signal generation circuit 46 is a comparator 461 that binarizes a signal input according to a predetermined reference, and a synchronization signal that generates an external synchronization signal that is synchronized with the rising edge of the binarized signal binarized by the comparator 461. And a generation circuit 462. The comparator 461 binarizes the input signal of FIG. 7A or FIG. 9Aa by a predetermined reference, outputs a signal (b), and sends it to the synchronization signal generation circuit 462. The synchronization signal generation circuit 462 generates the external synchronization signal (c) in synchronization with the rising edge of the input signal (b).

Referring to FIG. 11, delay circuit 4 shown in FIG.
7, the signals generated by the delay circuit 57, the multiplication circuit 58, and the timing pulse generation circuit 48 will be described.
The external synchronization signal (c) generated by the external synchronization signal generation circuit 46 is sent to the delay circuit 47, and the delay circuit 47
The timing pulse generation circuit 4 generates the synchronization signal (d) delayed by the fixed time T1 with respect to the external synchronization signal (c).
8 and the delay circuit 57. In the delay circuit 47, the synchronizing signal (d) delayed by a predetermined time T1 with respect to the external synchronizing signal (c) is generated by recording an alternating magnetic field and a laser beam by the signal of the magneto-optical recording medium 1 as described below. This is for accurately applying or irradiating the current position. That is, when the magneto-optical recording medium 1 is irradiated with a laser beam and a magnetic field is applied to form a magnetic domain, the magnetic domain is not always formed from the position where the laser beam irradiation is started, and actually, the magnetic domain is formed.
A magnetic domain is formed at a position slightly displaced from the position where the laser beam irradiation is started. Therefore, when reproducing a signal, the delay time T1 is set in order to accurately irradiate the position of the formed magnetic domain with the laser beam and apply the magnetic field.

The delay circuit 57 has a period (T / T) of the synchronizing signal (d) with respect to the transmitted synchronizing signal (d).
4) The synchronization signal (dd) delayed by 4) is generated and output to the multiplication circuit 58. The multiplication circuit 58 uses the synchronization signal (d
The synchronizing signal (dd2) having the frequency of d) doubled is generated and output to the reproduction signal detecting circuit 45.

The timing pulse generation circuit 48 synchronizes with the synchronization signal (d) sent thereto, and the magnetic head 52 applies a magnetic field application timing pulse (e) for applying an alternating magnetic field to the magneto-optical recording medium 1 and an optical signal. A semiconductor laser in the head 40 generates a laser beam irradiation timing pulse (f) for irradiating the magneto-optical recording medium 1 with a pulsed laser beam. In this case, the timing pulse generating circuit 48 applies the magnetic field application timing pulse (e) for applying the magnetic field for expanding the magnetic domain transferred to the reproducing layer 4 of the magneto-optical recording medium 1 and the time T2. The time T3 in which a magnetic field for erasing the generated magnetic domain is applied is set to have a predetermined ratio. Normally, T2 / T3 is set in the range of 0.2 to 1.5. Further, the timing pulse generating circuit 48 is irradiated with a laser beam after a magnetic field for expanding the magnetic domain transferred to the reproducing layer 4 of the magneto-optical recording medium 1 is applied, and a magnetic field for expanding the magnetic domain is applied. The time T4 is set so that the laser beam irradiation is completed before the laser beam irradiation is completed, and the laser beam irradiation timing pulse (d) is generated. This is because even if the laser beam is irradiated in the transition region where the alternating magnetic field is switched from one direction to the other direction, the magnetic domain transferred to the reproducing layer of the magneto-optical recording medium 1 is not sufficiently expanded and good reproduction is achieved. This is because no signal can be obtained.

Referring to FIG. 12, reproduction signal detecting circuit 45
The detection of the reproduction signal in will be described. Domain 1 recorded in groove or land of magneto-optical recording medium 1
An alternating magnetic field is applied based on the magnetic field applying timing pulse (e) that coincides with the position of 21, and the reproduction signal (g) is detected by the photodetector in the optical head 40. The reproduction signal (g) has peaks 122 and 12 corresponding to the expansion of the magnetic domain.
2, ... The detected reproduction signal (g) is amplified to a predetermined value by the reproduction signal amplification circuit 41 and then input to the reproduction signal detection circuit 45. Playback signal detection circuit 45
Is A / D-converts the input reproduction signal (g) in synchronization with the synchronization signal (dd2) to generate the signal (h), and at the same time, for one cycle of the synchronization signal (dd2) with respect to the signal (h). Generate a delayed signal (i). Then, the reproduction signal detection circuit 45 calculates a difference between the generated signal (h) and the signal (i) to generate a reproduction signal (j). The signal (h) is a signal corresponding to the magnetic domain expanded by the alternating magnetic field, and the signal (i) is the signal (h) for one cycle of the synchronization signal (dd2), that is, the magnetic field applying timing pulse (e). ) Is delayed by a half cycle, the subtraction of the signal (i) from the signal (h) means that the difference between the reproduction signal at the time when the magnetic domain is erased and the reproduction signal at the time when the magnetic domain is erased. It is equivalent to calculating. Specifically, at one timing 123 of the synchronization signal (dd2), the signal (h) has a peak 125 when the magnetic domain is expanded, and the signal (i) has a value 124 when the magnetic domain is erased. Subtracting signal (i) from signal (h) at timing 123 results in subtracting value 124 from peak 125. This corresponds to subtracting the value at the time when the magnetic domain is erased from the peak when the magnetic domain is expanded.
As a result, the reproduction signal (j) generated as described above is
The influence of the birefringence and tilt of the substrate of the magneto-optical recording medium 1 can be eliminated, and a reproduced signal without fluctuation as shown in FIG. 28 can be detected. Here, the magnetic field applied to expand the magnetic domain is referred to as a first peak magnetic field, and the magnetic field applied to erase the expanded magnetic domain is referred to as a second peak magnetic field. Therefore, in the present invention, the reproduction signal intensity is subtracted from the reproduction signal intensity at the time when the magnetic domain is transferred / expanded to the reproduction layer 4 of the magneto-optical recording medium 1 Is detected.

Referring to FIG. 13, reproduction signal detecting circuit 45
The first embodiment of will be described. In the first embodiment, the reproduction signal detection circuit 45 includes an A / D converter 451 that converts an analog signal into a digital signal, and a shift register 452 that delays the digitally converted signal for a certain time.
And a differencer 453 that calculates the difference between the two signals. The A / D converter 451 receives the input reproduction signal (g).
Is digitally converted to generate a signal (h), which is input to the shift register 452 and the difference unit 453. A / D converter 4
Reference numeral 51 digitally converts the reproduction signal (g) in synchronization with the synchronization signal (dd2). The shift register 452 delays the input signal (h) by one cycle of the synchronization signal (dd2) input from the multiplication circuit 58, generates the signal (i), and inputs the signal (i) to the difference unit 453. The subtractor 453 subtracts the signal (i) from the input signal (h) to generate a reproduction signal (j).

Referring to FIG. 14, reproduction signal detecting circuit 45
A second embodiment will be described. In the second embodiment, the reproduction signal detection circuit 45 includes an A / D converter 451.
And a DSP 454. The A / D converter 451 is
The inputted reproduction signal (g) is digitally converted in synchronization with the synchronization signal (dd2) to generate the signal (h), and the DSP 45
Output to 4. The DSP 454 receives the input signal (h)
The signal (i) delayed by one cycle of the synchronizing signal (dd2) is generated based on the above, and the calculation for subtracting the signal (i) from the signal (h) is performed to output the reproduction signal (j). That is, in the second embodiment of the reproduction signal detecting circuit 45, the shift register 452 and the difference unit 453 in the first embodiment are combined with the DSP.
The configuration is replaced with 454.

The information recording / reproducing apparatus according to the present invention is shown in FIG.
The information recording / reproducing apparatus shown in FIG. 15 is not limited to the one shown in FIG. The information recording / reproducing apparatus shown in FIG.
Of the information recording / reproducing apparatus shown in FIG.
The delay circuit 57 and the multiplication circuit 58 are replaced with an external synchronization signal generation circuit 460.

Referring to FIG. 16, external synchronization signal generation circuit 460 includes comparator 461 and synchronization signal generation circuit 4
62, a delay circuit 463, and a multiplication circuit 58.
The comparator 461 binarizes the input signal of FIG. 7A or FIG. 9Aa by a predetermined reference, outputs a signal (b), and sends it to the synchronization signal generation circuit 462. The synchronization signal generation circuit 462 generates the external synchronization signal (c) in synchronization with the rising edge of the input signal (b). The synchronization signal generation circuit 462 outputs the generated external synchronization signal (c) to the delay circuit 47 and the delay circuit 463. Delay circuit 4
Reference numeral 63 denotes a time T1 shown in FIG. 11 for the input external synchronization signal (c) and a quarter cycle (T / T) of the external synchronization signal (c).
4) The synchronizing signal (dd) delayed by the sum (T1 + T / 4) of the time corresponding to 4 minutes is generated and output to the multiplying circuit 58. The multiplication circuit 58 generates a synchronization signal (dd2) whose frequency is doubled based on the input synchronization signal (dd), and outputs the synchronization signal (dd2) to the reproduction signal detection circuit 45.

Even if the external synchronizing signal generating circuit 460 is used, the reproduction signal detecting circuit 45 outputs the reproduction signal (j) according to the flow of the signal processing described in FIG. As a result,
The information recording / reproducing apparatus shown in FIG. 5 can also output the reproduced signal shown in FIG. In addition,
In the information recording / reproducing apparatus shown in FIG. 15, the reproduction signal detecting circuit 45 has the configuration shown in FIG. 13 or 14.

A third embodiment of the reproduced signal detecting circuit 45 will be described with reference to FIGS. In the third embodiment, the reproduction signal detection circuit 45 is composed of a delay circuit 450.
And an A / D converter 451, a shift register 452,
And a differentiator 453. The delay circuit 450 generates a reproduction signal (gg) by delaying the reproduction signal (g) by one cycle of the synchronization signal (cc) obtained by doubling the frequency of the external synchronization signal (c), and generates the A / D converter 451. Output to. A / D converter 4
The reference numeral 51 digitally converts the reproduction signal (gg) in synchronization with the synchronization signal (cc) to generate a signal (hh).
h) is output to the shift register 452 and the difference unit 453. The shift register 452 receives the input signal (hh)
Is delayed by one cycle of the synchronization signal (cc) to obtain the signal (ii)
Is generated and input to the differentiator 453. The differentiator 453 is
The reproduced signal (j) is generated by subtracting the signal (ii) from the input signal (hh).

Even when the reproduction signal detecting circuit 45 shown in FIG. 17 is used, the signal detected at the timing when the magnetic domain is erased is subtracted from the signal detected at the timing when the magnetic domain is expanded, and the reproduction signal (j) is output. Therefore, the swell shown in FIG. 28 can be removed.

The third embodiment of the reproduction signal detecting circuit 45 does not detect the reproduction signal (g) in synchronization with the synchronization signal (dd2) obtained by delaying the phase of the external synchronization signal (c). , The phase of the reproduction signal (g) is delayed to have the same phase as the external synchronization signal (c), and the synchronization signal (c
This is a circuit for detecting a reproduced signal in synchronization with c).

Further, the reproduction signal detecting circuit 45 shown in FIG.
The information recording / reproducing apparatus including as a constituent element has the configuration shown in FIG. 15, and the external synchronization signal generation circuit 460 outputs the generated external synchronization signal (c) to the delay circuit 47 and also outputs the external synchronization signal (c). To generate a synchronization signal (cc) that is twice the frequency of, and output the generated synchronization signal (cc) to the reproduction signal detection circuit 45.

Referring to FIG. 19, reproduction signal detecting circuit 45
A fourth embodiment of will be described. In the fourth embodiment, the reproduction signal detecting circuit 45 includes a delay circuit 450 and an A
The / D converter 451 and the DSP 454 are provided. The reproduction signal detection circuit 45 of the fourth embodiment is the same as the shift register 452 and the difference unit 45 of the reproduction signal detection circuit 45 of the third embodiment.
3 has a configuration in which 3 and 4 are replaced by a DSP 454. Therefore,
The delay circuit 450 and the A / D converter 451 operate in the same manner as described with reference to FIG. 17, and the DSP 454 controls the A / D converter 45.
Based on the signal (hh) input from 1, the synchronization signal (c
The signal (ii) delayed by one cycle of c) is generated, the signal (ii) is subtracted from the signal (hh), and the reproduction signal (j) is output.

By using the reproduction signal detecting circuit 45 shown in FIG. 19, the reproduction signal from which the swell shown in FIG. 28 is removed can be output.

Further, the reproduced signal detecting circuit 45 shown in FIG.
The information recording / reproducing apparatus including as a constituent element has the configuration shown in FIG. 15, and the external synchronization signal generation circuit 460 outputs the generated external synchronization signal (c) to the delay circuit 47 and also outputs the external synchronization signal (c). To generate a synchronization signal (cc) that is twice the frequency of, and output the generated synchronization signal (cc) to the reproduction signal detection circuit 45.

A fifth embodiment of the reproduced signal detecting circuit 45 will be described with reference to FIGS. In the fifth embodiment, the reproduction signal detection circuit 45 is composed of a delay circuit 450.
A differential amplifier 455, a comparator 456, a delay circuit 458, and a D flip-flop 459.
The delay circuit 450 generates a signal (gg) obtained by delaying the reproduction signal (g) by a half cycle of the external synchronization signal (c) and outputs the signal (gg) to the inverting terminal (−) of the difference amplifier 455. Further, the differential amplifier 455 has a non-inverting terminal (+) with a reproduction signal (g).
Is input, the signal (gg) is subtracted and amplified from the reproduction signal (g) to generate a signal (gs), which is output to the (+) terminal of the comparator 456. The comparator 456 compares the signal (gs) at a predetermined level L and outputs the signal (h
2) is generated. The resistor 457 is used for the comparator 4
A resistor for determining the comparator level L of 56. The delay circuit 458 inputs the signal (h2), generates a signal (hh2) obtained by delaying the phase of the input signal (h2) by a predetermined value, and outputs the signal (hh2) to the D flip-flop 459. The D flip-flop 459 receives the input signal (h
h2) is held in synchronization with the external synchronizing signal (c) and the reproduced signal (j) is output.

The delay amount in delay circuit 458 is determined as follows. When the phase difference between the timing pulse (e) for applying the magnetic field and the external synchronization signal (c) is α and the phase difference between the signal (h2) and the signal (hh2) is β,
α + β = 3π / 2 holds. Therefore, the phase difference β between the signal (h2) and the signal (hh2) can be determined by determining the phase difference α between the external synchronization signal (c) and the timing pulse (e).

Using the reproduction signal detecting circuit 45 shown in FIG. 29, the reproduction signal from which the swell shown in FIG. 28 has been removed can be output.

Further, the reproduction signal detecting circuit 45 shown in FIG.
The information recording / reproducing apparatus including as a component has the configuration shown in FIG. 15, and the external synchronization signal generation circuit 460 outputs the generated external synchronization signal (c) to the delay circuit 47 and the reproduction signal detection circuit 45.
And output to.

A sixth embodiment of the reproduced signal detection circuit 45 will be described with reference to FIGS. In the sixth embodiment, the reproduction signal detection circuit 45 is composed of a delay circuit 450.
A differential amplifier 455, a comparator 456, a D flip-flop 459, and a delay circuit 4588. The delay circuit 450, the difference amplifier 455, and the comparator 456 perform the same operation as described in FIG. The delay circuit 4588 receives the external synchronization signal (c), generates a synchronization signal (c2) obtained by delaying the phase of the external synchronization signal (c) by π / 2, and outputs the synchronization signal (c2) to the D flip-flop 459. The D flip-flop 459 receives the input signal (h2)
Is held in synchronism with the synchronization signal (c2), and the reproduction signal (j) is output.

Although the delay amount in the delay circuit 4588 is set to π / 2 in the above description, the external synchronization signal (c)
, The timing difference between the timing pulse (e) and γ, the delay circuit 4
When the delay amount at 588 is δ, generally γ + π /
Delay by δ determined by 2 = δ. Therefore, the delay amount δ in the delay circuit 4588 is determined by determining the phase difference γ between the external synchronization signal (c) and the timing pulse (e).
Can be determined.

Using the reproduction signal detecting circuit 45 shown in FIG. 31, the reproduction signal from which the swell shown in FIG. 28 has been removed can be output.

Further, the reproduced signal detecting circuit 45 shown in FIG.
The information recording / reproducing apparatus including as a component has the configuration shown in FIG. 15, and the external synchronization signal generation circuit 460 outputs the generated external synchronization signal (c) to the delay circuit 47 and the reproduction signal detection circuit 45.
And output to.

The information recording / reproducing apparatus is not limited to the configuration shown in FIGS. 4 and 15, and may be the information recording / reproducing apparatus having the configuration shown in FIG. The information recording / reproducing apparatus shown in FIG.
The information recording / reproducing apparatus shown in FIG.
0 and the control circuit 201 are added. In the information recording / reproducing apparatus shown in FIG. 20, after detecting the level of the alternating magnetic field at which the magnetic domain transferred / enlarged in the reproducing layer 4 of the magneto-optical recording medium 1 is sufficiently erased, the level is determined according to the level of the alternating magnetic field. The timing pulse generating circuit 48 is characterized in that it sets a time for erasing the magnetic domain and generates a magnetic field applying timing pulse.

The level of the alternating magnetic field with which the magnetic domains are sufficiently erased is determined in the practice area provided in the magneto-optical recording medium. The planar structure of the magneto-optical recording medium 1 will be described with reference to FIG. The magneto-optical recording medium 1 has spiral tracks 213 each composed of a land and a groove, and a TOC (Table Of Content) from the outer peripheral portion.
s) It has an area 210 and a data area 211. In the magneto-optical recording medium 1, since the track 213 progresses from the outer circumference to the inner circumference, the practice area 212 is provided at the beginning of the data area 211 after the TOC area 210 is completed.

Details of the practice area 212 will be described with reference to FIG. The practice area 212 includes a first practice area 2121 and a second practice area 2122.
The shortest domains 220, 220, ... Are recorded in advance in the second practice areas 2121 and 2122 at predetermined intervals. In the first practice area 2121 a laser beam having an intensity that does not transfer the magnetic domain from the recording layer 6 of the magneto-optical recording medium 1 to the reproducing layer 4 is determined, and in the second practice area 2122 the magnetic domain transferred / expanded in the reproducing layer 4 is determined. Determines a level of alternating magnetic field sufficient to eliminate the

Referring to FIG. 23, recording layer 6 to reproduction layer 4
The determination of the laser beam having the intensity in which the magnetic domain is not transferred will be described. The first practice area 2121 is irradiated with a laser beam of varying intensity and a reproduction signal is detected. When the intensity of the laser beam is high, signals 230 and 2 with peaks are present.
31 is detected, and a signal 232 having no peak is detected when the intensity of the laser beam is weak. In this case, the presence of the peak in the detected signal means that the magnetic domain was transferred to the reproducing layer 4, and the absence of the peak in the detected signal means that the magnetic domain was not transferred to the reproducing layer 4. To do. Therefore, the intensity of the laser beam is signal 2
The intensity at which 32 is detected is determined as the intensity of the laser beam. After the laser beam having such an intensity that the magnetic domain is not transferred to the reproducing layer 4 is determined, the level of the alternating magnetic field that can sufficiently erase the magnetic domain transferred / expanded to the reproducing layer 4 in the second practice area 2122 is determined. Referring to FIG. 24,
The alternating magnetic field applied in the second practice area 2122 will be described. The alternating magnetic field 240 has a maximum value 242 and a minimum value 241, changes in a predetermined cycle, and has a maximum value 24.
The magnetic domains are transferred / expanded in the reproducing layer 4 at the timing when the magnetic field of 2 is applied, and the transferred / expanded magnetic domains are erased at the timing when the magnetic field of the minimum value 241 is applied. Therefore, in the second practice area 2122, the reproduced signal is detected by applying an alternating magnetic field having various levels of the minimum value 241. That is, the level of the applied alternating magnetic field 240 is the first
Level 243, second level 244, third level 2
45, can be changed to the fourth level 246. Referring to FIG. 25, when a reproduction signal is detected by applying a laser beam and an alternating magnetic field, the reproduction signal has a maximum value 2 corresponding to the timing at which a magnetic field having a maximum value 242 of the alternating magnetic field 240 is applied.
50 appears, and the read signal has a minimum value 25 corresponding to the timing when the magnetic field having the minimum value 241 of the alternating magnetic field 240 is applied.
1 appears. After the reproduction signal is detected by applying the laser beam and the alternating magnetic field, in the second practice area 2122,
A signal is detected by irradiating the reproducing layer 4 only with a laser beam having an intensity that does not transfer magnetic domains. In this case, since the alternating magnetic field for erasing is insufficient, that is, the minimum value 241 of the alternating magnetic field 240 is insufficient, the magnetic domain transferred and expanded in the reproducing layer 4 remains as shown in FIG. Like peak 260
Is detected. When the alternating magnetic field for erasing is sufficient, a peakless signal as shown in FIG. 27 is detected. Therefore, the alternating magnetic field having the level of the minimum value 241 when the signal shown in FIG. 27 is detected is determined as the reproducing alternating magnetic field.

In the present invention, the time during which the magnetic field used for erasing magnetic domains in the alternating magnetic field is determined according to the determined minimum value 241 of the alternating magnetic field. That is, when the minimum value 241 has the first level 243, the time for which the magnetic field used for erasing the magnetic domain is applied is set to be short, and the minimum value 241 has the fourth level 24.
When it has 6, the time for which the magnetic field used for erasing the magnetic domain is applied is set to be long.

Referring to FIG. 20, the second practice area 212 is displayed.
In the practice area 2122, the control circuit 201 changes the minimum value 241 of the alternating magnetic field, that is, the minimum values of the first level 243, the second level 244, the third level 245, and the fourth level 246. A magnetic head drive circuit 49 for applying an alternating magnetic field having 241 to the magneto-optical recording medium 1.
To control. The reproduction signal detected by applying the laser beam and the alternating magnetic field in the second practice area 2122 and the reproduction signal detected by irradiating only the laser beam thereafter are amplified to a predetermined value by the reproduction signal amplifier circuit 41. After that, the reproduction signal level detection circuit 200 detects whether or not there is a peak in the reproduction signal. The reproduction signal level detection circuit 200 receives the minimum value 241 of the alternating magnetic field from the control circuit 201.
Of the first level 243, the second level 244, the third level 245, and the fourth level 246 are transmitted. Therefore, the reproduction signal level detection circuit 200 can determine the level of the minimum value 241 of the alternating magnetic field when the transmitted reproduction signal has no peak, and sends the determined level to the timing pulse generation circuit 48. The timing pulse generation circuit 48 sets the time for which the magnetic field used for erasing the magnetic domain is applied according to the level of the transmitted minimum value 241, and generates the timing pulse for magnetic field application. The subsequent operation is the same as that described with reference to FIG.

In the above description, the practice area 212 is described as one location, but the present invention is not limited to this, and a plurality of practice areas may be provided.

In the information recording / reproducing apparatus shown in FIG. 20, the recorded signal is reproduced after the alternating magnetic field is determined enough to erase the magnetic domain transferred / enlarged in the reproducing layer 4 of the magneto-optical recording medium 1. Since the timing pulse for magnetic field application for applying the alternating magnetic field used for
Since the reproduction signal can be detected in a state where the enlarged magnetic domain is surely erased, the reproduction signal can be detected more accurately by the synergistic effect of the reproduction signal detecting method described above.

[Brief description of drawings]

FIG. 1 is a cross-sectional structural diagram of a magneto-optical recording medium.

FIG. 2 is a diagram illustrating the principle of magnetic domain expansion reproduction.

FIG. 3 is a diagram showing a relationship between an alternating magnetic field applied to a magneto-optical recording medium and a detected reproduction signal.

FIG. 4 is a block diagram of an information recording / reproducing apparatus.

FIG. 5 is a diagram illustrating a detailed structure of a groove and a land of a magneto-optical recording medium.

FIG. 6 is a diagram illustrating a configuration of a photodetector unit in an optical head and signal processing.

FIG. 7 is a diagram illustrating generation of an external synchronization signal.

FIG. 8 is a diagram for explaining another configuration and signal processing of the photodetector section in the optical head.

FIG. 9 is a diagram illustrating generation of an external synchronization signal.

FIG. 10 is a diagram showing a configuration of an external synchronization signal generation circuit.

11 is a diagram illustrating signal processing in the delay circuit, the multiplication circuit, and the timing pulse generation circuit of the information recording / reproducing apparatus shown in FIG.

FIG. 12 is a diagram showing signal processing in a reproduction signal detection circuit.

FIG. 13 is a diagram showing a configuration of a reproduction signal detection circuit in the first embodiment.

FIG. 14 is a diagram showing a configuration of a reproduction signal detection circuit in the second embodiment.

FIG. 15 is another block diagram of the information recording / reproducing apparatus.

FIG. 16 is a diagram showing another configuration of the external synchronization signal generation circuit.

FIG. 17 is a diagram showing the configuration of a reproduction signal detection circuit in the third embodiment.

FIG. 18 is a diagram illustrating signal processing in a reproduced signal detection circuit according to the third embodiment.

FIG. 19 is a diagram showing a configuration of a reproduction signal detection circuit in the fourth embodiment.

FIG. 20 is still another block diagram of the information recording / reproducing apparatus.

FIG. 21 is a plan structural view of a magneto-optical recording medium.

FIG. 22 is a diagram showing a configuration of a practice area.

FIG. 23 is a diagram showing a reproduction signal detected by irradiating only a laser beam.

FIG. 24 is a diagram in which the level of the minimum value of the alternating magnetic field is changed.

FIG. 25 is a diagram showing a waveform of a reproduction signal by magnetic domain expansion reproduction.

FIG. 26 is a diagram showing a reproduction signal detected by irradiating only a laser beam when erasing of a magnetic domain transferred / expanded to a reproduction layer is insufficient.

FIG. 27 is a diagram showing a reproduction signal detected by irradiating only a laser beam when the magnetic domain transferred / expanded to the reproduction layer is sufficiently erased.

FIG. 28 is a diagram showing a conventional reproduced signal waveform.

FIG. 29 is a diagram showing the configuration of a reproduction signal detection circuit in the fifth embodiment.

FIG. 30 is a diagram for explaining signal processing in the reproduction signal detection circuit in the fifth embodiment.

FIG. 31 is a diagram showing the configuration of a reproduction signal detection circuit in the sixth embodiment.

FIG. 32 is a diagram for explaining signal processing in the reproduction signal detection circuit in the sixth embodiment.

[Explanation of symbols]

1 ... Magneto-optical recording medium 2 ... Substrate 3 ... Interference layer 4 ... Reproducing layer 5 ... Non-magnetic layer 6 ... Recording layer 7 ... Protective layer 8 ... Heat dissipation layer 9 ... Laser beam 10, 11 ... Magnetic field 12 ... Alternate magnetic field 13 ... Playback signal 20, 51 ... Magnetization 30, 31, 50 ... Magnetic domain 40 ... Optical head 41 ... Reproduction signal amplification circuit 42 ... Servo circuit 43 ... Servo mechanism 44 ... Spindle motor 45 ... Reproduction signal detection circuit 46, 460 ... External synchronization signal generation circuit 47, 57, 450, 458, 463, 4588 ...
Delay circuit 48 ... Timing pulse generation circuit 49 ... Magnetic head drive circuit 52 ... Magnetic head 53 ... Groove 54 ... Land 55 ... Discontinuous area 56 ... Laser drive circuit 58. ..Multiplier circuit 60 ... photodetector 61 ... A area 62 ... B area 63 ... C area 64 ... D area 65 ... track direction 66 ... tracking direction 67 ... Adder 68, 455 ... Difference amplifier 70 ... Discontinuous area detection signal 120 ... Groove or land 121 ... Domain 122 ... Peak intensity 200 ... Reproduction signal level detection circuit 201 ... Control circuit 210 ... TOC area 211 ... Data area 212 ... Practice area 213 ... Track 220 ... Shortest domain 280 ... Playback waveform 2121 ... First practice Area 2122 ... Second practice area 451 ... A / D converter 452 ... Shift register 453 ... Difference calculator 454 ... DSP 456, 461 ... Comparator 459 ... D flip-flop 462 ... Synchronous signal generation circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 11/00-13/08

Claims (4)

(57) [Claims] 1. A signal by expanding a magnetic domain from a magneto-optical recording medium.
An information recording / reproducing apparatus for reproducing a magnetic field, comprising: a first magnetic field for expanding a magnetic domain in the magneto-optical recording medium;
A second magnetic field that erases the enlarged magnetic domain is applied at a predetermined cycle.
The magnetic head and the magneto- optical recording medium are irradiated with a laser beam to
An optical head that detects the reflected light from the air recording medium and an external synchronization signal is generated based on the output from the optical head.
A fixed amount of external synchronization signal from the external synchronization signal generation circuit and the external synchronization signal generation circuit
A delay circuit for delaying and inputting an external synchronizing signal delayed by the delay circuit,
Multiplier circuit for multiplying the frequency of the delayed external synchronization signal
The playback signal detected by the optical head to the synchronization signal.
And an A / D converter for converting into a digital signal
The signal converted into a digital signal by the / D converter is
A shift register that delays a fixed amount in synchronization with a synchronization signal
And a signal output by the A / D converter,
Input the signal output from the
A / D conversion from the signal output by the shift register
And subtractor for subtracting the signal output by the multiplier
A signal detection circuit, wherein the reproduction signal detection circuit includes the first magnetic field, and
The optical head detects when a second magnetic field is applied
Received signal, and from the received signal from the multiplier circuit
The first magnetic field is applied in synchronization with the input synchronization signal.
Strength when applied and the strength when the second magnetic field is applied
And the difference between the detected intensities is used as the playback signal.
An information recording / reproducing apparatus characterized by outputting. 2. A signal obtained by expanding a magnetic domain from a magneto-optical recording medium.
An information recording / reproducing apparatus for reproducing a magnetic field, comprising: a first magnetic field for expanding a magnetic domain in the magneto-optical recording medium;
A second magnetic field that erases the enlarged magnetic domain is applied at a predetermined cycle.
The magnetic head and the magneto- optical recording medium are irradiated with a laser beam to
An optical head that detects the reflected light from the air recording medium and an external synchronization signal is generated based on the output from the optical head.
A fixed amount of external synchronization signal from the external synchronization signal generation circuit and the external synchronization signal generation circuit
A first delay circuit for delaying and an external synchronizing signal delayed by the first delay circuit are input.
Multiplication to multiply the frequency of the external synchronization signal delayed by applying
The circuit and the playback signal detected by the optical head are delayed by a certain amount.
Output by a second delay circuit and the second delay circuit
Signal output by the external synchronization signal generation circuit
A / D for converting to a digital signal in synchronization with the synchronization signal
Converted to a digital signal by the converter and the A / D converter
The delayed signal by a fixed amount in synchronization with the synchronization signal
Output from the shift register and the A / D converter
The signal and the signal output by the shift register.
From the signal input and output by the shift register
Difference for subtracting the signal output by the A / D converter
And a reproduction signal detection circuit including a container, the reproduction signal detection circuit including the first magnetic field, and
The optical head detects when a second magnetic field is applied
Received signal, and from the received signal from the multiplier circuit
The first magnetic field is applied in synchronization with the input synchronization signal.
Strength when applied and the strength when the second magnetic field is applied
And the difference between the detected intensities is used as the playback signal.
An information recording / reproducing apparatus characterized by outputting. 3. A signal obtained by expanding a magnetic domain from a magneto-optical recording medium.
An information recording / reproducing apparatus for reproducing a magnetic field, comprising: a first magnetic field for expanding a magnetic domain in the magneto-optical recording medium;
A second magnetic field that erases the enlarged magnetic domain is applied at a predetermined cycle.
The magnetic head and the magneto- optical recording medium are irradiated with a laser beam to
An optical head that detects the reflected light from the air recording medium and an external synchronization signal is generated based on the output from the optical head.
The external synchronization signal generating circuit and the reproduction signal detected by the optical head are delayed by a certain amount.
First delay circuit and a reproduction signal before Symbol optical head detects
And a signal delayed by the first delay circuit
A differential amplifier that calculates and amplifies
Comparing the output signal with a constant level
Compared by the comparator and the comparator
A second delay circuit that delays the generated signal by a certain amount;
The signal delayed by the delay circuit of the
In synchronization with the external synchronization signal output from the generation circuit,
Playback signal detection time including D flip-flop
And a reproduction signal detecting circuit , the reproduction signal detecting circuit includes:
The optical head detects when a second magnetic field is applied
The external synchronization signal from the received signal.
In synchronization with the external synchronization signal from the generation circuit, the first magnetic
Field and the second magnetic field
And the strength of the detected intensity is detected, and the difference in the detected intensity is reproduced.
Information recording / reproducing apparatus characterized by outputting as a signal
Place 4. A signal obtained by expanding a magnetic domain from a magneto-optical recording medium.
An information recording / reproducing apparatus for reproducing a magnetic field, comprising: a first magnetic field for expanding a magnetic domain in the magneto-optical recording medium;
A second magnetic field that erases the enlarged magnetic domain is applied at a predetermined cycle.
The magnetic head and the magneto- optical recording medium are irradiated with a laser beam to
An optical head that detects the reflected light from the air recording medium and an external synchronization signal is generated based on the output from the optical head.
The external synchronization signal generating circuit and the reproduction signal detected by the optical head are delayed by a certain amount.
First delay circuit and reproduction signal detected by the optical head
And a signal delayed by the first delay circuit
A differential amplifier that calculates and amplifies
Comparing the output signal with a constant level
External sync from the external sync signal generator circuit
A second delay circuit for delaying a signal by a fixed amount;
In synchronization with the external synchronization signal delayed by the delay circuit,
Holds signals that have been compared by a comparator
And a reproduction signal detection circuit including a D flip-flop
And the reproduction signal detection circuit includes the first magnetic field, and
The optical head detects when a second magnetic field is applied
The external synchronization signal from the received signal.
In synchronization with the external synchronization signal from the generation circuit, the first magnetic
Field and the second magnetic field
And the strength of the detected intensity is detected, and the difference in the detected intensity is reproduced.
Information recording / reproducing apparatus characterized by outputting as a signal
Place