JP2565214B2 - Magneto-optical disk recorder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk recorder, and more particularly to a magneto-optical disk for magnetic field modulation and signal irradiation by irradiating a recording light beam. The present invention relates to a magneto-optical disk recorder for recording. 2. Description of the Related Art An example of a technique for recording / reproducing a signal on an optical recording medium is disclosed in Japanese Patent Publication No. 58-45096. This is because it is necessary to control the energy of the recording light beam at the time of recording in order to optimally record / reproduce information on / from the optical recording medium. The aim is to get light of average intensity. Specifically, an optical recording medium is irradiated with a recording light beam to change the light transmittance or the light reflectance in the information recording portion of the optical recording medium to record information.
The auxiliary light beam is applied to a recorded information recording track near the recording light beam to detect the recorded information signal by the light receiving element, and the energy of the recording light beam is controlled according to the detected signal. As a result, control is performed to eliminate the difference in rotational speed between the outer circumference and the inner circumference, the difference in the frequency of the recording information, the difference in the energy of the recording light beam caused by the fluctuation in the power of the light source, and the like. Optimal playback. The above-mentioned change in the light transmittance or the light reflectance is gradually changed from the initial vapor deposition state to the vaporization state of the amorphous semiconductor layer deposited on the recording medium substrate by the irradiation of the recording light beam. It is generated by changing the state. However, in the prior art disclosed in the above publication, in order to record a signal stably and surely, the state of the recorded information signal is always fed back and recorded by irradiation of the auxiliary light beam. It was necessary to control the energy of the light beam for use. For this reason,
The recording light beam and the auxiliary light beam must be placed close to each other, and the track must always be tracked by two beams, which complicates the overall configuration of the device such as the optical device, servo device, and various circuits, resulting in high cost. There was a problem. By the way, the technique disclosed in the above publication is
It is a so-called write-once type that cannot be rewritten. Therefore, there has been proposed a technique for improving the above-mentioned problems and enabling signal rewriting. This uses a magneto-optical disk as a recording medium, and applies a weak magnetic field to the recording magnetic film side surface of the magneto-optical disk in the vertical direction by an electromagnet or the like, and corresponds to the magnet on the disk substrate side surface of the magneto-optical disk. The position is irradiated with laser light as a recording light beam. When a magnetic field is applied immediately after the temperature of the irradiated portion rises to the Curie temperature due to the irradiation of laser light, only the magnetic domain portion (hereinafter referred to as a pit) is magnetized with its polarity reversed in the vertical direction. become. In this way, the polarity of each pit is determined in accordance with the change in the polarity of the magnetic field or the on / off of the laser beam, and a digital signal is recorded for each bit. For this reason, the magneto-optical disk has the characteristics that the above-mentioned problems are solved and the rewriting of signals is relatively easy. However, if the surface of the magneto-optical disk (that is, the surface of the disk substrate on which the laser beam is irradiated) is dirty, for example, a fingerprint is attached, there is a problem that a signal cannot be recorded. In the case of a compact disc for reproduction only, it is sufficient to wipe off the fingerprint, but when the recording itself cannot be performed, wiping off the fingerprint later does not solve the problem. As shown in FIG. 5, if there is a fingerprint-attached portion 50 on the surface of the magneto-optical disk, the laser light is diffused, and the power level L _P on the laser light emitting side is constant. The power level L _P ′ of the laser light on the recording film corresponding to the fingerprint adhered portion 50 is drastically reduced, and the threshold value Th required for recording a signal is not exceeded, and recording becomes impossible. As shown in FIG. 5, recording cannot be performed with the laser light amount below the threshold value Th, so that the reproduction signal S _M at the time of reproduction is reproduced.
Has a zero amplitude, and the reproduced signal S _M is defective. In the case of a fingerprint, this duration is more than 10 msec, and if recording is performed in such a state, so-called muting, unpleasant noise (so-called buzzing sound), etc. occur at the stage of reproducing the magneto-optical disk. There was a problem. In order to solve such a problem, the disc should be handled more carefully, or the disc should be stored in a case called a caddy to prevent the attachment of dirt. However, in that case, there are many problems in terms of easiness of handling and cost increase. Therefore, an object of the present invention is to provide a magneto-optical disk recorder which can record a signal even if dirt such as fingerprints is attached to the surface of the magneto-optical disk. According to the present invention, in a magneto-optical disk recorder for recording a signal by irradiating a magneto-optical disk with a magnetic field modulation and a recording light beam, a recording light beam is recorded. The peak level of the return signal is detected and the output of the recording light beam is controlled to keep the peak level constant. A weak magnetic field is applied in the vertical direction from the recording magnetic film side of the magneto-optical disk, and a recording light beam is emitted from the disk substrate side. In response to the change of the polarity of the magnetic field or the on / off of the recording light beam, the polarity in the vertical direction of each pit is determined and the signal is recorded. When the signal is recorded as described above, the return signal is detected by the recording light beam, and the peak level of the return signal is held by the peak hold circuit. The return signal of reflected light is reduced due to stains such as fingerprints
Even if it is a little, the level-reduced part of the return signal is held by the peak hold circuit and is output as a stable peak level return signal. The return signal is compared with the reference voltage by the error amplifier, and the output of the light beam is controlled according to the degree of the difference with respect to the reference voltage. That is, when the peak voltage of the return signal is lower than the reference voltage due to the fingerprint adhered, the power of the light beam is increased according to the difference between the two voltages, and the power of the light beam on the recording film is adhered to the fingerprint. It will be made to the same level as if it had not been done, and the recording will be made surely. An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to a magneto-optical disk recorder as shown in FIGS. As shown in FIG. 1, this magneto-optical disk recorder is composed of a magnetic field modulation system 1, a pickup unit 2, a return signal detection unit 3, a peak hold circuit 4, and a current control circuit 5. The magnetic field modulation system 1 is arranged on the recording magnetic film 7 side of the magneto-optical disk 6. In order to invert the polarity of a specific pit 9 of the recording magnetic film 7 according to a digital modulation signal applied from the terminal 8, a magnetic field is applied to the pit 9 in the vertical direction (V direction shown in FIG. 1). is there. The magnetic field modulation system 1 includes a driver circuit 10 and the driver circuit 10
Mainly from the coil 11 connected to the. The driver circuit 10 drives the coil 11 according to the digital modulation signal applied from the terminal 8 and causes the coil 11 to generate a magnetic field. The pickup unit 2 is the surface 1 of the disk 6.
2, that is, on the side of the disk substrate 13 and at a position facing the coil 11, irradiates the above-mentioned specific pit 9 with the laser light L _L as a recording light beam, and at the same time detects reflected light as a return signal. This leads to Part 3. The pickup unit 2 includes an objective lens 14 and a collimator lens 1
5, beam splitter 16, laser diode 17
Mainly consists of and. The laser diode 17 is a light source of the laser light L _L. The laser light L _L emitted from the laser diode 17 travels straight through the beam splitter 16 and then reaches the collimator lens 15. The collimator lens 15 converts the laser light L _L into parallel light and reaches the objective lens 14. The laser light L _L is focused on the pit 9 by the objective lens 14. The return signal detector 3 includes a beam splitter 1
Return signal S _R from the reflected light from the disk 6 that has passed through
Is detected and a control signal and a return light amount signal S _L are obtained from the return signal S _R , the control signal is supplied to a servo circuit (not shown), and the return light amount signal S _L is supplied to the peak hold circuit 4
Is supplied to. The return signal detector 3 includes a lens 18 and
It is mainly composed of detectors 19 and 20, amplifiers 21 and 22, a differential amplifier 23, and an adder 24. The detectors 19 and 20 are connected to the amplifiers 21 and 22, respectively,
Further, the amplifiers 21 and 22 are the differential amplifier 23 and the adder 2
4 are each connected. The lens 18 focuses the reflected light from the disk 6 on the detectors 19 and 20. The detectors 19 and 20 output return signals S _R based on the reflected light collected by the lens 18, respectively. Amplifier 2
Reference numerals 1 and 22 amplify the return signals S _R output from the detectors 19 and 20, and output the amplified return signals S _R to the differential amplifier 23 and the adder 24, respectively. The differential amplifier 23 takes the difference between the return signals S _R and outputs it as a control signal. This control signal is supplied to the servo circuit and is for performing tracking servo, focus servo, etc. via the actuator. The adder 24 adds the return signal S _R and outputs it as a return light amount signal S _L to the peak hold circuit 4. The current control circuit 5 maintains the power level L _P of the laser light L _{L at} an appropriate level and limits the current flowing through the laser diode 17 so that the laser diode 17 is not destroyed. It is provided in. As shown in FIG. 2, the current control circuit 5 includes an error amplifier 25, a reference voltage Vref, and a PNP type transistor 2.
6, 27 and resistors 28, 29, 30. The error amplifier 25 includes a voltage V _P (hereinafter referred to as a peak voltage) of the return light amount signal S _L and a reference voltage Vref.
And the output terminal of the error amplifier 25 is a resistor 2
8 is connected to the base of the transistor 26. The emitter of the transistor 26 is connected to the power supply line to which the power supply voltage Vcc is supplied via the resistor 29 and the base of the transistor 27. Further, a resistor 30 is provided between the collector of the transistor 26 and the ground.
And a series circuit of laser diode 17 is inserted.
The emitter of the transistor 27 is connected to the power supply line, and the collector is connected to the base of the transistor 26. Next, the operation of this magneto-optical disk recorder will be described. The rotating disk 6 is irradiated with the laser light L _L from the pickup unit 2, and a magnetic field is generated by the coil 11 according to the digital modulation signal. When the specific pit 9 of the disk 6 reaches the irradiation range of the laser light L _L , that is, the beam spot, this pit 9
Is heated by the irradiation of the laser beam L _L. Immediately after the temperature of the pit 9 rises to the Curie point temperature, that is, the threshold value Th, the magnetic field generated by the coil 11 is applied to the pit 9.
Then, the polarity of the pit 9 is inverted in the vertical direction (V direction shown by the arrow in FIG. 1), and the reproduction signal S _{M of} 1 bit is recorded. At this time, the laser light L _L irradiating the pit 9 portion of the disk 6 is reflected and reflected by the beam splitter 16
After being refracted by the lens, the light is focused on the detectors 19 and 20 by the lens 18. The return signal S _R output from the detectors 19 and 20 and amplified by the amplifiers 21 and 22 is the differential amplifier 2
A difference signal is generated by 3 and then amplified and output as a control signal. This control signal reaches the servo circuit and controls various servo operations. The return signal S _R is output to the peak hold circuit 4 as the return light amount signal S _L after the sum signal is generated by the adder 24. The return light amount signal S _L is a table of the optical disc.
As shown in Fig. 4A, due to dirt such as fingerprints attached to the surface
The level lowering portion 31 exists . The peak hold circuit 4 detects the peak level of the return light amount signal S _L ,
The aforementioned les as shown in FIG. 4B by holding
A peak voltage V _P that is not affected by the bell drop portion 31 is generated. The current control circuit 5 compares the peak voltage V _P with the reference voltage Vref to supply a current that corrects the difference between the two to the laser diode 17, and the power level L _P of the laser light L _L. Controlled. As shown in FIG. 3, when the fingerprint adhering portion 32 is present, the level of the returning light amount signal S _L is lowered and the peak voltage V _P supplied to the current control circuit 5 is lowered. Figure 2
The current control circuit 25 shown by increases the drive current supplied to the laser diode 17 when the peak voltage V _P decreases. As a result, the power level L _P of the laser light L _L is increased in the fingerprint attaching section 32, as shown in FIG. On the other hand, the power level L _P ′ applied to the recording film is
Since fingerprints are attached, the level is almost constant. Therefore, according to this embodiment, when the recorded disc 6 is reproduced, the amplitude of the reproduction signal S _M is hardly attenuated even in the fingerprint attaching portion 32. When the spot of the laser beam L _L passes through the fingerprint attaching portion 32, the peak voltage V _P of the return light amount signal S _L rises. As a result, in the current control circuit 5, the drive current supplied to the laser diode 17 is reduced, and a drive current of a normal magnitude is generated. Also, due to the pinhole of the disk 6, etc.
Even if the power level L _P of the laser light L _L may suddenly increase, the current is limited by the action of the current control circuit 5, and the laser diode 17 is prevented from being destroyed. According to this embodiment, since the current control circuit 5 is provided, the power level L _P of the laser light L _L can be corrected according to the level of the return light amount signal S _L , and the pinhole is irradiated. As in the case described above, the protective action of the laser diode 17 can be expected even against a sudden change in the power level L _P. The magneto-optical disk recorder according to the present invention records a signal by applying magnetic field modulation to the magneto-optical disk and irradiating a recording light beam.
The feature is that the peak level of the return signal of the recording light beam is detected and the output of the recording light beam is controlled so as to keep the peak level constant. Therefore, according to the present invention, even if dirt such as fingerprints is attached to the surface of the magneto-optical disk, the adverse effect on the recording of the signal can be eliminated. There is an effect that the loss of can be minimized. Further, according to the present invention, the recording light beam only needs to raise the temperature of the pit portion to the threshold value (Curie point),
Even if the diameter of the writing spot is slightly increased due to the influence of fingerprints, there is no problem in recording / reproducing a signal, so that the control of the recording light beam is relatively easy.
Furthermore, due to the above-mentioned effect, it is not necessary to store the magneto-optical disk in a case such as a caddy to prevent dirt from adhering, and the magneto-optical disk can be handled as it is like the compact disk, improving the handleability and the caddy. There is also an effect that the cost reduction due to the abolition of can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing an embodiment of a magneto-optical disk to which the invention is applied. FIG. 2 is a circuit diagram of a current control circuit shown in FIG. FIG. 3 is an explanatory diagram showing a power level of a recording light beam with respect to a fingerprint adhered portion and a state of amplitude of a signal corresponding to the power level. [Fig. 4] Deterioration due to fingerprints etc. adhering to the disk surface
Explanatory drawing showing the light amount signal and this reduced return light amount signal
FIG. 6 is an explanatory diagram showing a signal after correction of P by peak hold . FIG. 5 is an explanatory diagram used for explaining a magneto-optical disk recorder that can be used in the present invention.

Claims (1)

(57) is performed with a magnetic field modulation to Claims magneto-optical disk, and have contact to the magneto-optical disc recorder that records a signal by performing irradiation of the recording light beam, the recording light beam of the return signal means for detecting the level
When a magneto-optical disc recorder comprising a control means for controlling the output of said recording light beam to keep the upper sharp bell constant.