JPH0669577A - Semiconductor laser device and optical information read write equipment, optical communication equipment and magneto-optical read write equipment using the same - Google Patents

Abstract

PURPOSE:To obtain lights of two wavelengths, as an optical output of low crosstalk and high SNR, by using wavelength switching operation characteristics based on the dynamics of a semiconductor laser carrier, modulating the pulse width of an injection current according to the information signal to be written, and driving the semiconductor laser. CONSTITUTION:When a write command is delivered, the write position of a magneto-optical disk 1 is designated. A control unit 22 controls seek mechanism, and accesses a light spot on an information track. Write data of the control unit 22 are sent to a modulation unit 23, which modulates the write data according to a specified modulation system and outputs them to a semiconductor laser driver 25 after adding a header and ECC codes. At the same time, the control unit 22 generates a high frequency signal via a high frequency oscillator 24. Modulation data of the modulation unit 23 and the high frequency signal of the high frequency oscillator 24 are inputted in the semiconductor laser driver 25, which drives a semiconductor laser 6 according to the inputted signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device that oscillates a laser beam, an optical information recording / reproducing device using the same, an optical communication device, and a magneto-optical recording / reproducing device that records or reproduces information magneto-optically. It relates to the device.

[0002]

2. Description of the Related Art In recent years, technological advances in the fields of optical communication and optical information processing have been remarkably advanced, such as wavelength multiplexing transmission and frequency modulation transmission methods for expanding the transmission band in the communications field, and wavelength multiplexing in the optical recording field. Due to higher recording densities and the like, higher wavelength tunability has become more important as a function required of semiconductor lasers. In such a technical field, the density of information is spatially and temporally increased by utilizing the multiplicity and parallelism of light wavelengths. Therefore, the present applicant previously proposed the following semiconductor laser and its driving method for the purpose of highly tunable wavelength. That is, as disclosed in Japanese Patent Laid-Open No. 63-211787, the active layer is composed of a plurality of quantum well layers having different quantum levels, and the magnitude of the injection current in the quantum well layers is changed. , Changing the oscillation wavelength.

By the way, progress has been remarkable in an optical information recording / reproducing apparatus for recording / reproducing information using such a semiconductor laser, and in particular, a recording / reproducing apparatus using a magneto-optical recording medium or a phase change recording medium erases information. Due to the fact that rewriting is possible and the recording capacity is large, there are great expectations. In such a recording / reproducing apparatus, research on overwriting of information to increase the data transfer rate, research on immediate verification of recorded information (direct verification), and further simultaneous recording / reproduction by a plurality of light spots ( Research and development on parallel recording / reproduction is active.

As an overwrite method for a magneto-optical recording medium, a magnetic field modulation method and an optical modulation method are roughly classified. The magnetic field modulation method is a method of applying a bias magnetic field modulated according to recording information while irradiating a recording medium with a laser beam having a constant intensity. On the other hand, the optical modulation method is a method of recording information by applying a constant magnetic field to a recording medium and irradiating a laser beam whose intensity is modulated according to the recording information. In addition, recently, a method of overwriting by applying a pulsed laser beam while applying an alternating magnetic field having a constant frequency to a recording medium has been proposed. 20A and 20B are time charts for explaining the recording operation of the recording method. FIG. 20A shows a reference clock, FIG. 20B shows an AC magnetic field, and FIG. 20C shows a pulsed laser beam. In this recording method, an AC magnetic field synchronized with the reference clock is applied to the recording medium, and a laser beam is irradiated in synchronization with the positive and negative peak positions of this AC magnetic field. In this case, the laser beam is emitted at the positive peak point or the negative peak point of the alternating magnetic field based on the signal obtained by modulating the recording signal shown in FIG. As described above, the magnetization direction of the temperature rising portion of the recording medium faces the direction corresponding to the recording signal, and the magnetic domain as shown in FIG. The shape of the magnetic domains formed at this time is an arrow blade shape as shown in FIG. As an overwrite method for a phase-change recording medium, there is a method of performing overwriting by irradiating a high-power and low-power light beam modulated according to recording information.

On the other hand, as a method of direct verify, for example, two light spots are sequentially irradiated on the same information track, and information is recorded by the preceding light spots.
There is a method in which the recorded information is reproduced by a subsequent light spot to perform verification. To create two light spots, there are a method of creating two light spots with one optical head and a method of creating two light spots with two optical heads. Further, as a parallel recording / reproducing system, a system for controlling four light spots by using an image rotating element (image rotator) so that each light spot is scanned on a target information track (ISOM'91 Lecture No. 3G- 1) and Japanese Patent Application No. 3-80654, there is a method of recording information on a plurality of information tracks by an alternating magnetic field and optical pulses.

[0006]

By the way, in the prior art, when a semiconductor laser is driven, the oscillation wavelength is mainly changed by changing the magnitude of the injection current, that is, a method of driving by utilizing the static characteristics of the semiconductor laser. Was taken. For example, in the case of using the apparatus for optically recording information, by changing the injection current, as shown in FIG. 4 to I _L and I _H, reproducing the intensity of the light beam power P _R and the recording power P _W However, there is a problem in that the range of application is limited in the drive utilizing the static characteristics of the semiconductor laser.

Further, as described above, in the case of recording in parallel, or in the case of recording by using the magnetic field modulation light pulse, in any case, it is necessary to reproduce the information and verify after the recording. Therefore, there is a problem that it takes time to record. Furthermore, when recording and reproducing in parallel using multiple light spots, a stable tracking control method has not been established, and in addition, each information track is directly irradiated by irradiating a light spot for recording and verifying. Even when verifying,
A tracking control method for stably scanning two light spots on one information track has not been established.

Further, as described above, when two optical spots are created by one optical head to perform the direct verify, the curvature of the track is different between the inner circumference and the outer circumference of the information recording disk. There is a problem that the tracking accuracy is changed and the accuracy of verification is lowered depending on the disc position. Furthermore, when creating two light spots with two optical heads, since both of the optical heads irradiate linearly polarized light, they are easily affected by the birefringence of the disk substrate, and the light spots are also distributed in the disk radial direction. When seeking, I had to move it exactly in the radial direction. Therefore, the structure is restricted, which is a factor that hinders the miniaturization of the optical system.

The present invention has been made in order to solve the above problems, and its purpose is to drive a semiconductor laser by utilizing the switching dynamic characteristics of the oscillation wavelength, thereby achieving low crosstalk and It is an object of the present invention to provide a semiconductor laser device capable of obtaining an optical output with a good SNR, an optical information recording / reproducing device using the same, and an optical communication device.

Further, the present invention enables parallel recording and direct verification by irradiating a plurality of information tracks with a main light spot for recording and a sub light spot for verifying, respectively, and additionally tracking of a plurality of light spots. It is an object of the present invention to provide a magneto-optical recording / reproducing device that can be stably controlled.

Further, according to the present invention, by providing an optical head dedicated to recording information for irradiating a circularly polarized light beam, the influence of the birefringence of the disk substrate is less likely to occur, and hence there is no restriction on the structure of the optical system. An object of the present invention is to provide a magneto-optical recording / reproducing device which is designed to downsize an optical system.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to generate a high-frequency signal having a predetermined frequency, and a semiconductor laser having a different energy level and including an active layer composed of a plurality of light-emitting layers. High-frequency signal generation means for
This is achieved by a semiconductor laser device characterized in that it has a driving means for modulating the signal width of the high frequency signal according to the transmitted information signal and driving the semiconductor laser by the obtained width modulation signal. It

Another object of the present invention is to provide an optical information recording / reproducing apparatus for irradiating an optical information recording medium with a light beam to record or reproduce information. A semiconductor laser including an active layer composed of layers, a high-frequency signal generating means for generating a high-frequency signal of a predetermined frequency, and a signal width of the high-frequency signal is modulated according to a transmitted information signal to obtain Drive means for driving the semiconductor laser by the width modulated signal, and a wavelength dispersion element for dispersing a plurality of light beams having different wavelengths emitted from the semiconductor laser by this drive for each wavelength. A recording light beam and a reproducing light beam, which are modulated according to the information signal of the laser, are formed on the same information track or different information tracks of the recording medium. By irradiating it has been, are achieved by an optical information recording and reproducing apparatus characterized by performing recording and reproduction of information at the same time.

Further, an object of the present invention is to provide an optical communication device for transmitting an information signal through an optical fiber, in which semiconductor lasers having energy levels different from each other and including active layers composed of a plurality of light emitting layers are laminated. A high-frequency signal generating means for generating a high-frequency signal of a predetermined frequency, and modulating the signal width of the high-frequency signal according to the sent information signal, and driving the semiconductor laser with the obtained width modulation signal. Drive means for detecting the optical information signal having a signal width modulated in accordance with the information signals of different wavelengths emitted from the semiconductor laser by the drive and transmitted through the optical fiber, and the optical signal of a constant period. And a clock generation for generating the optical signal of the constant cycle as a reference clock signal based on the detection signal of the sensor And a demodulating means for demodulating the optical information signal based on the detection signal of the sensor and demodulating the information transmitted in synchronization with the reference clock signal. Achieved by a communication device.

Another object of the present invention is to provide a plurality of light sources, a diffraction grating for dividing each light beam emitted from each light source into a 0th-order diffracted light and a 1st-order diffracted light, and the diffraction gratings. A plurality of light sources for forming 0-th order diffracted light and 1st-order diffracted light on a plurality of information tracks of a magneto-optical recording medium as a main light spot and a sub-light spot, respectively; A magnetic field applying means for applying an alternating magnetic field of a predetermined frequency to the irradiation spot of the light spot, and a light source driving means for pulse-driving the plurality of light sources according to signals modulated according to information signals to be recorded respectively. And recording information on a plurality of information tracks by applying a magnetic field by the magnetic field applying means and irradiating the main light spot with pulses by driving a light source driving means. , Magneto-optical recording / reproducing characterized in that a verify signal is generated based on the reflected light of each sub-light spot scanned after each main light spot to verify the information recorded on each information track. Achieved by the device.

Still another object of the present invention is to irradiate a circularly polarized recording light beam in a magneto-optical recording / reproducing apparatus which irradiates a magneto-optical recording medium with a light beam and records information by applying a magnetic field. Of the first and second optical heads for moving a track of the recording medium, and a first optical head for irradiating a reproducing light beam of linearly polarized light. A movable optical system for forming each light beam as a minute light spot on a designated information track, and information is recorded by the recording light beam of the first optical head, and a second optical head is provided. This is achieved by a magneto-optical recording / reproducing apparatus characterized in that the recorded information is reproduced on the basis of the reflected light of the reproducing light beam, and the recorded information is immediately verified.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings. First, one embodiment of the semiconductor laser device and the optical information recording / reproducing device of the present invention will be described with reference to FIG. In FIG. 1, 1 is a magneto-optical disk which is an information recording medium, 2 is an achromatic pickup lens, 3 is a polarization beam splitter, 4 is a prism, and 5 is an achromatic collimator lens. Further, 6 is a two-wavelength semiconductor laser for simultaneously generating two-wavelength laser beams of λ ₁ and λ ₂ as described later in detail. The laser light flux emitted from the semiconductor laser 1 is collimated by an achromatic collimator lens 5 and then shaped into a beam by a prism 4, and at the same time has a wavelength separation function based on its wavelength dispersion characteristic, two wavelengths λ ₁ and λ ₂ Is separated into light beams. The two-wavelength light beam of the two-wavelength semiconductor laser 1 is P-polarized light having an oscillating plane of an electric vector in the plane of the paper. After being separated by the prism 4, it is transmitted through the polarization beam splitter 3 and by the achromatic pickup lens 2. An image is formed on the recording layer of the magneto-optical disk 1 as two minute light spots. The transmittance of the polarization beam splitter 3 is about 70%. The interval between the two light spots imaged on the recording layer is determined by ftan θ, where θ is the angle at which the two light beams emitted from the prism 4 and f is the focal length of the pickup lens 2. It should be noted that the light spots of the wavelengths λ ₁ and λ ₂ of the two-wavelength semiconductor laser 6 are successively irradiated on the same information track,
The light spot of wavelength λ ₁ is for recording information in advance,
The light spot of wavelength λ ₂ is subsequently used for verification.

The light beam thus radiated on the magneto-optical disk is reflected by the recording layer and again passes through the pickup lens 2 and enters the polarization beam splitter 3. here,
Almost 100% of the S-polarized component contained in the reflected light is reflected by the polarization beam splitter 3, and about 30% of the P-polarized component is reflected and guided to the detection optical system side. On the detection optical system side, _first , the light beam of wavelength λ ₁ is reflected by the wavelength selection action of the dichroic prism 7, the light beam of wavelength λ ₂ is transmitted and is guided to the beam splitter 8, and here, the transmitted light and the reflected light are separated. It is split into two light beams. One of the separated light beams passes through a lens 9 and a beam splitter 10
And is further separated into two light beams of transmitted light and reflected light. The light beam that has passed through the beam splitter 10 is detected by the four-division photodiode 12 through the cylindrical lens 11, and autofocus control by the astigmatism method is performed based on the obtained detection signal.

That is, a focus error signal is detected based on the detection signal of the four-division photodiode 12, and an actuator for driving the pickup lens 2 in the focus direction based on the focus error signal by a focus control circuit (not shown) (see FIG. The focus control of the light beam is performed by controlling (not shown). On the other hand, the light beam reflected by the beam splitter 10 is detected by the two-divided photodiode 13, and push-pull type auto-tracking control is performed based on the obtained detection signal. That is, a tracking error signal is detected based on the detection signal of the two-divided photodiode 13, and an actuator (not shown) for driving the pickup lens 2 in the tracking direction based on the tracking error signal by a tracking control circuit (not shown). The tracking control of the light beam is performed by controlling the.

On the other hand, the light beam of wavelength λ ₂ reflected by the beam splitter 8 enters the polarization beam splitter 16 via the half-wave plate 14 and the lens 15, and is converted into S-polarized light depending on the polarization component. It is separated into P-polarized light. S polarization and P
The polarized light is detected by the RF photodiodes 17 and 18, respectively, and two signals whose signal components have opposite phases and noise generated by the semiconductor laser 6 and the magneto-optical disk 1 have the same phase are obtained. Then, by differentially detecting these two signals with the differential amplifier 19, it is possible to obtain an RF signal with a good SNR in which noise is canceled.

Reference numeral 22 is a CP for controlling each part as a whole.
A control unit including U, 23 is a modulation unit for modulating the recording data sent from the control unit 22, 24
Is a high frequency oscillator for generating a high frequency signal. Two
Reference numeral 5 denotes a semiconductor laser driver for driving the semiconductor laser 6, which modulates the pulse width of the high frequency pulse of the high frequency oscillator 24 with the modulation data and generates and injects the injection current of the semiconductor laser 6 by the obtained pulse width modulation signal. To do. The driving of the semiconductor laser 6 will be described later in detail.
Reference numeral 26 is a waveform processing unit for performing processing such as integration and binarization on the RF signal obtained by the differential amplifier 19, and 27 is the original data obtained by performing ECC decoding and checking on the signal after the waveform processing. A demodulation unit for demodulation.
Reference numeral 28 is a comparator for comparing the recorded data with the demodulated reproduced data at the time of information recording to verify whether or not the information can be correctly recorded.

FIG. 2 shows a specific example of the two-wavelength semiconductor laser 6, and is a diagram schematically showing the energy band near the active layer. The semiconductor laser 6 used here
Is a semiconductor laser having an active layer composed of two quantum well layers having different compositions or widths. In the example of FIG. 2, 80ÅGsAs well 301 and 60ÅAl _0.12 G
a _0.88 As well 302 is 300 Å Al _0.36 Ga _0.64 As
Separated by barriers. And the top and bottom are 500
Å GRIN Al _0.3 Ga _0.7 As-Al _0.5 Ga _0.5
As optical / carrier confinement layer (SCH layer) 304, 3
It is sandwiched between 05.

FIG. 3 is a sectional view schematically showing the film structure of the two-wavelength semiconductor laser 6. In FIG. 3, n ⁺ -GaAs
On the substrate 301, 0.5 μm n ⁺ -GaAs buffer layer 308, 1.5 μm n-AlGaAs lower cladding layer 306, SCH layer 304, well layer 301, barrier layer 30.
3, well layer 302, SCH layer 305, 1.5 μm P-
Al _0.5 Ga _0.5 As upper clad layer 307, 0.5μ
m P ⁺ -GaAs cap layer 309 is sequentially laminated by the molecular beam epitaxial method. Also, A on the P side
u / Cr electrode 311 and Au-Ge / Au electrode 3 on the n side
12 are vapor-deposited and alloyed by taking ohmic contact. The SCH layer 3 near the active layer
04, well layer 301, barrier layer 303, well layer 302, S
The CH layer 305 is not entirely doped.

Next, the light emitting principle of the two-wavelength semiconductor laser 6 will be described with reference to FIGS. First, the electrodes 312 and 3
When a current is applied between 11, electrons e are generated in the first light emitting layer (well layer 3
02) and the second light emitting layer (well layer 301), the electrons e and holes h are recombined in the first light emitting layer 302, and the light of wavelength λ ₁ is stimulated to be emitted. The wavelength λ ₁ is 8 here
It is 30 nm. Then, when the injection current is increased, recombination of the electron e and the hole h occurs also in the second light emitting layer 301,
Light of wavelength λ ₂ is stimulatedly emitted. Wavelength λ ₂ is 780 nm
Is. Further, when the injection current is increased, the oscillation of the wavelength λ ₁ is stopped and only the light of the wavelength λ ₂ is oscillated.

FIG. 4 is a diagram showing the current-light output characteristics of the semiconductor laser 6, wherein the horizontal axis is the current and the vertical axis is the light output.
In the figure, P ₁ indicated by the broken line is the optical output of the wavelength λ ₁ , and P ₂ indicated by the alternate long and short dash line is the optical output of the wavelength λ ₂ . When the current I is increased, first, the light of wavelength λ ₁ starts to oscillate at the first threshold current I _th , and the light of wavelength λ ₂ starts to oscillate at the second threshold current I _1. . Further, as the current is increased, the current I ₂
The light of wavelength λ ₁ stops oscillating, and only the light of wavelength λ ₂ oscillates.

FIG. 5 is a diagram for explaining the switching dynamic characteristics of the two-wavelength semiconductor laser 6, and FIG. 5 (a) is a diagram showing the relationship between time and light intensity. When a pulsed current is injected into the semiconductor laser 6, electrons e and holes h are formed in the active layer.
Are injected from the opposite direction, electrons e are injected from the n side, and holes h are injected from the P side. At this time, the injected electron e has a high mobility as shown in the energy band near the active layer in FIG.
02 rapidly fills in thermal equilibrium. On the other hand, hall h
Has a low mobility, the well layer 302 is filled therewith, but the injection into the well layer 301 is delayed by the time over the barrier layer 303. As a result, when the time t is t ₁ ≦ t ≦ t ₂ , recombination light emission occurs only in the well layer 302, as shown in FIG.
As shown in (a), only light of wavelength λ ₂ oscillates. In addition,
The oscillation that appears at the beginning of the light of wavelength λ ₂ is the relaxation oscillation similar to that of a normal semiconductor laser.

If the time t is t ₂ ≤t≤t ₃ ,
As shown in FIG. 5C, the well layer 301 is also filled with the holes h, and as shown in FIG. 5A, both the well layers 301 and 30 are formed.
Light having wavelengths λ ₁ and λ ₂ oscillates from ₂ . Furthermore, t ₃ ≤t
When ≦ t ₄ , the well layers 301 and 30 are formed as shown in FIG.
The density of the holes h of 2 and the radiative recombination speed and the moving speed of the holes h between the two wells are balanced, and as a result, the oscillation of the wavelength λ ₂ is stopped and only the light of the wavelength λ ₁ is oscillated as shown in FIG. 5A. To do.

By injecting the pulse current into the semiconductor laser in this way, light of wavelength λ ₂ oscillates in the first half of the optical pulse and light of wavelength λ ₁ oscillates in the latter half. In this case, if the injection current level is appropriately selected, the emission time of the wavelength λ ₂ is almost constant regardless of the current pulse width, and only the emission time of the wavelength λ ₁ can be controlled by the current pulse width. Therefore, by keeping the crest value of the injected current pulse constant and changing the pulse width, the optical energy of the optical pulse of wavelength λ ₂ , that is, the time integration of the optical intensity remains constant, while the optical pulse of wavelength λ ₁ Only the light energy can be controlled.
In a heat mode optical memory such as a magneto-optical disk, a mark is formed by converting the energy of given light into heat, so by making the above-mentioned change in the width of an optical pulse correspond to information, Can be recorded. In the embodiment of FIG. 1, information is recorded by modulating the light energy of the wavelength λ ₁ according to the information by utilizing the wavelength switching dynamic characteristics of the semiconductor laser 6, and at the same time, the light of the wavelength λ ₂ is emitted. The recorded information is reproduced and verification is performed.

The specific operation of the optical information recording / reproducing apparatus shown in FIG. 1 will be described. When recording information, the recording data to be recorded is transferred to the control unit shown in FIG. When a recording command is issued, the recording position of the magneto-optical disk 1 is instructed, and the control unit 2
In accordance with the instruction, 2 controls a seek mechanism (not shown) to allow the light spot to access the instructed information track. Further, the control unit 22 confirms the physical address, the logical address, the recording enable / disable, etc. on the magneto-optical disk 1. The control unit 22 modulates the recording data with the modulation unit 2
3, the recording data is modulated by the modulation unit 23 by a predetermined modulation method, and a header and an ECC code are added and output to the semiconductor laser driver 25. At the same time, the control unit 22 sends an operation command to the high frequency oscillator 24 to generate a high frequency signal. As a result, the modulation data of the modulation unit 23 and the high frequency signal of the high frequency oscillator 24 are input to the semiconductor laser driver 25, and the laser driver 25 drives the semiconductor laser 6 based on these input signals.

The operation of the semiconductor laser device of this embodiment will be described with reference to FIG. 6A shows the modulation data modulated by the modulation unit 23, and FIG. 6B shows the high frequency signal generated by the high frequency oscillator 24. The semiconductor laser driver 25 modulates the pulse width of the high-frequency pulse signal according to the modulation data, and as shown in FIG. 6C, the pulse width of the injection current of the semiconductor laser 6 is short when the modulation data is low level. When the signal is at high level, it is driven longer by pulse width modulation. In addition, in FIG. 6C, the time axis is enlarged and shown with respect to FIG. As a result, the semiconductor laser 6 is driven, and as shown in FIG.
As shown in (e), a light pulse (pulsed light emission) is emitted in response to the drive pulse. FIG. 6D shows the optical output of the wavelength λ ₂ , which has almost the same optical pulse waveform regardless of the pulse width of the injection current as described in FIG. On the other hand, FIG. 6 (e)
Indicates the optical output of wavelength λ ₁ , and the width of the optical pulse is the pulse width modulation of the injection current.As shown by the broken line in the figure, the average value of the optical output in the recording data modulation cycle is , It reflects the modulation of information. According to the sampling theorem, the frequency of the high-frequency oscillator 24 may be twice the maximum frequency in the information modulation band, but a frequency of 10 times or more is preferable to ensure accuracy.

As described above, the semiconductor laser 6 simultaneously generates lights of different wavelengths λ ₁ and λ ₂ by driving the laser driver 25, and the light of the wavelength λ ₁ is a light output modulated according to information, and the wavelength λ ₂ Light is emitted as a constant light output. The laser light fluxes of two wavelengths emitted from the semiconductor laser 6 are separated into laser light fluxes of wavelengths λ ₁ and λ ₂ by the wavelength separation action of the prism 4 as described above, and the laser light fluxes on the information track of the magneto-optical disc 1 are spaced at regular intervals. After that, each is irradiated as a minute light spot. That is, a light spot having a wavelength λ ₁ pulse-width-modulated according to the recorded information is irradiated to the preceding position of the information track, and a light spot having a constant intensity of the wavelength λ ₂ is irradiated to a position immediately after that at a constant distance. To be done. As described above, the reflected light from the magneto-optical disk 1 is detected by the four-division photodiode 12 and the two-division photodiode 13, respectively, and the autofocus control and the autotracking control are performed based on the detection signals of the two. The light spot scans following the information track of the rotating magneto-optical disk 1. A magnetic head (not shown) applies a magnetic field in a fixed direction to the magneto-optical disk 1, and a series of data is sequentially recorded on the information track by irradiating a light spot whose intensity is modulated by pulse width modulation and applying the magnetic field. To go. At this time, FIG.
As shown in (c), an optical pulse having a narrow pulse width is emitted corresponding to the low level of data, but since the average optical power is small, information is not recorded by it.

On the other hand, the reflected light of the magneto-optical disk 1 is guided to the dichroic prism 7 as described above, where the light of the wavelength λ ₁ is reflected and the light of the wavelength λ ₂ is transmitted, so that the reproducing optical system is provided. Only light of wavelength λ ₂ is guided. Therefore, only the reflected light of the light spot of wavelength λ ₂ scanned after the light spot of wavelength λ ₁ for information recording is detected by the photodiodes 17 and 18 via the beam splitter 8 and the polarization beam splitter 16. . Photodiode 17,
The detection signal of 18 is differentially detected by the differential amplifier 19, and RF
It is reproduced as a signal. Since the obtained reproduction signal is due to the reflected light of the light spot of wavelength λ ₂ , it becomes the reproduction signal of the information recorded by the light spot of wavelength λ ₁ . The reproduced signal is subjected to integration, binarization, etc. processing in the waveform processing unit 26, and then demodulated in the demodulation unit 27 to generate reproduced data. The obtained reproduced data is sent to the comparator 28, where it is verified by comparing it with the recorded data from the control unit 22. Then, the comparator 28
Then, a verify determination signal indicating whether normal writing or rewriting is required is output to the control unit 22 depending on the type and level of error. If a recording error occurs, the control unit 22 re-records the same data at the same position on the magneto-optical disk 1 or at another position and ends the process.

During normal reproduction of information, the control unit 22 outputs a control signal to the modulation unit 23, and the output signal of the modulation unit 23 is maintained at a low level.
Further, the control unit 22 instructs the high-frequency oscillator 24 to increase the frequency, so that the semiconductor laser driver 25 drives by narrowing the pulse width of the injection current of the semiconductor laser 6 and oscillates only the light of wavelength λ ₂ . As described above, at the time of reproducing information, only the light spot having the wavelength λ ₂ is irradiated onto the information track of the magneto-optical disk 1, and the reflected light thereof is detected by the photodiodes 17 and 18 and the differential detection by the differential amplifier 19 as in the recording. To be played. In this case, the control unit 22 instructs the demodulation unit 27 to send the reproduced data directly to the control unit 22 without transferring it to the comparator 28. Thereby, the demodulation unit 2
The reproduction data generated in 7 is sent to the control unit 22 and transferred from here to the outside.

As described above, in the present embodiment, the semiconductor laser is utilized for the wavelength switching dynamic characteristic, and the pulse width of the injection current is modulated in accordance with the information signal to be recorded, so that the light of two wavelengths is generated. It is possible to obtain an optical output having a high SNR with low crosstalk. Therefore, by irradiating the information track with the obtained light of two wavelengths as a light spot modulated according to the information for recording and a light spot with a constant intensity for reproduction at a constant interval, recording of information is performed. At the same time, the one-pass direct verify of reading the record information and confirming the record becomes possible. Therefore, the total throughput of the writing speed can be remarkably improved, and a high-speed transfer rate and a high-speed access can be realized, as compared with the conventional method of switching the recording and the verification for every one rotation of the disk using one spot.
Further, when performing direct verification using two light spots, it is required that the crosstalk between the two light spots is sufficiently small. In order to meet this requirement, in the past, for example, a two-array semiconductor laser was used to directly Although a method of performing verification has been proposed, in the method of this two-array semiconductor laser, there is a trade-off between reducing the distance between two light spots and improving crosstalk. There is a problem that it is very difficult to adjust the position of the laser. In this embodiment, the distance between the two light spots is determined by ftan θ as described above,
No optical adjustment is required and it is easy to manufacture.

In the above embodiments, the dichroic prism is used to separate the lights of different wavelengths. However, since the re-imaging spots are separated according to the wavelength, the size of the spatial filter and the photodiode is theoretically increased. The same function can be given depending on the shape and position, but the dichroic prism is more advantageous in terms of positioning accuracy. Further, a wavelength filter such as an etalon, a prism, a diffraction grating or the like may be used instead of the dichroic prism. Further, although beam shaping and wavelength separation were performed using the prism 4, a similar function can be provided by a diffraction grating. In that case, the direction of dispersion is opposite to that of the prism.

Further, in the embodiment, an example of recording and verifying information by using lights of two different wavelengths is shown.
In addition to this, for example, by irradiating the light spot before the recording light spot, the pilot for confirming the state before writing, such as detecting defects on the disc and confirming that the previous data has been erased. It can also be used as a spot or as a preheating spot for providing preheating before writing. Further, it is possible to irradiate two light spots not on the same information track but on different information tracks to perform recording and reproduction in parallel.

FIG. 7 is a block diagram showing a second embodiment of the optical information recording / reproducing apparatus of the present invention. In the embodiment of FIG. 1, light of two wavelengths is separated by using a dichroic prism, but in this embodiment, the dynamic characteristics of a two-wavelength semiconductor laser at high frequency are used to electrically separate the light on the time axis. . In FIG. 7, the same parts as those in FIG. 1 are designated by the same reference numerals. In FIG. 7, when recording information, the two-wavelength semiconductor laser 6 is driven by the semiconductor laser driver 25 in exactly the same manner as in the embodiment of FIG. As a result, the information track of the magneto-optical disk 1 is irradiated with the light spot of the wavelength λ _{1 and} the light spot of the wavelength λ ₂ , and the information is recorded on the information track. On the other hand, the reflected light from the magneto-optical disk 1 is detected by the photodiodes 17 and 18 via the beam splitter 8, the polarization beam splitter 16, etc. However, since there is no dichroic prism here, the reflected light is above the photodiodes 17 and 18. Causes large spatial crosstalk.

Therefore, in the present embodiment, the high frequency signal of the high frequency oscillator 24 is output to the waveform processing unit 29, and in the waveform processing unit 29, the differential amplifier 1 is synchronized with the high frequency signal.
By sampling and holding the RF signal of 9, the wavelength λ ₂
The data within the emission time of the light is extracted. Therefore, even if the wavelength separation is not performed by using the dichroic prism, only the reproduction signal by the light beam having the wavelength λ ₂ can be extracted by synchronously detecting by using the high frequency signal in the signal processing stage of the reproduction signal. The reproduced signal thus obtained is demodulated by the demodulation unit 27 and then compared with the recorded data by the comparator 28 to perform verification. As a synchronization detection method using a high frequency pulse, for example, a synchronization pulse is extracted from the output signal of the high frequency oscillator 24, the delay is adjusted,
There is a method of sampling and holding the analog value of the RF signal. Further, it is also possible to generate synchronous data in which the frequency and phase of the high frequency pulse are recovered from the binarized data of the RF signal by using a PLL circuit, and use this to synchronously detect only the signal by the light of wavelength λ _2. . As described above, in this embodiment, it is possible to extract only the reproduction signal by the light spot of the reproduction light spot having the wavelength λ ₂ by processing the electric reproduction signal without using the wavelength separation element such as the dichroic prism. it can. Therefore, similar to the embodiment of FIG. 1, it is possible to perform the verification at the same time as the recording of the information, that is, the one-pass direct verification.

FIG. 8 is a block diagram showing an embodiment of the optical communication apparatus of the present invention. In FIG. 8, those having the same functions as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted here. In FIG. 8, 32 is a coupling lens,
33 is an optical fiber for transmitting the optical information of the semiconductor laser 6, and 34 is a lens. Further, 35 is a prism for spatially dispersing light of wavelengths λ ₁ and λ ₂ sent through the optical fiber 33 for each wavelength, and 38 and 39 are wavelengths of λ ₁ and λ ₂ dispersed by the prism 35. It is a sensor for detecting each light. 30 is a controller, 3
1 is a modulation unit, 40 and 41 are sensor amplifiers for amplifying the signals detected by the sensors 38 and 39, and 42 is a clock signal by binarizing the light signal of wavelength λ ₂ amplified by the sensor amplifier 40. And a demodulation unit 43 for demodulating the signal of wavelength λ ₁ amplified by the sensor amplifier 41 into the original information.

When the information to be transmitted is input, the controller 30 transfers it to the modulation unit 31, and the transmission information is converted into a communication protocol. The obtained conversion data is sent to the semiconductor laser driver 25, and the laser driver 25 drives the semiconductor laser 6 exactly as in the embodiment of FIG. That is, a current obtained by modulating the pulse width of the high frequency pulse of the high frequency oscillator 24 according to the data is injected into the semiconductor laser 6, and as a result, the semiconductor laser 6 has a wavelength λ ₂ as shown in FIGS. 6 (d) and 6 (e). Output the optical pulse whose pulse width is modulated according to the optical pulse and the data of the wavelength λ ₁ . Each of the light pulses enters the optical fiber 33 through the coupling lens 32, travels through the optical fiber 33, and is guided to the receiving side. On the receiving side, the light transmitted through the optical fiber 35 is condensed on the prism 35 by the lens 34, and at this time, the wavelengths λ ₁ and λ ₂ are caused by the wavelength separation action of the prism 35.
Light is spatially separated. As a result, the light of wavelength λ ₁ is incident on the sensor 38 and the light of wavelength λ ₂ is incident on the sensor 39, which are respectively detected by the sensor. The detection signal of the light of wavelength λ ₁ detected by the sensor 38 is amplified by the sensor amplifier 41 and then demodulated by the demodulation unit 43 into the original information. On the other hand, the detection signal of the light of wavelength λ ₂ detected by the sensor 39 is amplified by the sensor amplifier 40 and then converted into a clock signal of a constant frequency by the binarization unit 42.

Here, each optical pulse emitted from the semiconductor laser 6 propagates in the optical fiber 33 and is transmitted to the receiving side. During the propagation, disturbance such as bending, vibration or temperature of the optical fiber 33 occurs. If there is, each optical pulse is affected such as the peak value fluctuating. In this case, the optical fibers 33 for the light of wavelengths λ ₁ and λ ₂
If the dispersion characteristic inside is so small that it can be ignored, it is possible to correct the fluctuation due to the disturbance of the signal of the light of wavelength λ ₁ based on the signal of the light of wavelength λ ₂ . For example, since the fluctuation of the crest value of the optical pulse can be detected as the fluctuation of the optical pulse train of the wavelength λ ₂ which is originally uniform, the gain control using the automatic gain control function of the sensor amplifier 41 based on the detection result, Or by correcting the DC component,
Data fluctuations can be corrected.

The clock obtained by the binarization unit 42 is sent to the demodulation unit 43, and the demodulation unit 43 outputs the demodulation data in synchronization with this clock signal.
Since the clock signal obtained by the binarization unit 42 is a clock signal with little jitter, the optical fiber 33
Even if jitter is added to the optical pulse of wavelength λ ₁ that was transmitted containing information during the transmission of, the transmitted data is accurately demodulated regardless of the jitter by extracting the data in synchronization with the clock signal. be able to. As described above, in the present embodiment, it is possible to simultaneously transmit an optical pulse containing information and an optical pulse serving as a reference clock even though it is one semiconductor laser. Therefore, when demodulating information, by synchronizing the data with the reference clock, the transmitted data can be accurately demodulated regardless of the jitter that occurs during transmission of the optical fiber. Although the two wavelengths of light are separated by using the prism 35 in the embodiment, the wavelength separation element is not used as in the embodiment of FIG. 1, and the two wavelengths of light are separated with low crosstalk by temporal resolution. It is also possible to do so.

In the above embodiments, the semiconductor laser device of the present invention is used for the optical information recording / reproducing device and the optical communication device. However, other than this, for example, for information transmission of the optical measuring device. Can be used. Furthermore, in the embodiment, an example of performing information recording and communication by using light of two wavelengths is shown, but it is also possible to realize a recording / reproducing device and a communication device having higher functions by using light of wavelengths longer than that. Is.

Next, an embodiment of the magneto-optical recording / reproducing apparatus of the present invention will be described. FIG. 9 is a block diagram showing the configuration of an embodiment of the magneto-optical recording / reproducing apparatus of the present invention. In this embodiment, a magneto-optical recording / reproducing apparatus that records and reproduces image information will be described as an example. In FIG. 9, reference numeral 51 is a laser light source in which three semiconductor lasers 51a, 51b, 51c are manufactured by hybrid or monolithic.
The three laser beams emitted from the laser light source 51 are
After being collimated by the collimator lenses 52, they are corrected by the beam shaping prism 53 to have a circular cross section.
The light beam emitted from the beam shaping prism 53 further passes through the diffraction grating 4, and at this time, it is divided into three sets of O-order light beam and ± 1st-order light beam. The intensity of the 0th order light with respect to the ± 1st order light is 1
It is about / 5 to 1/2. Further, the diffraction directions of the ± first-order lights are set substantially in the direction corresponding to the parallel direction of the information tracks on the magneto-optical recording medium 61, but here, the diffraction grating 5 is used.
4 is rotatable in a plane perpendicular to the optical axis. That is, the diffraction direction of the first-order diffracted light can be finely rotated by controlling the rotation of the diffraction grating 54 by the driving unit 55 such as an actuator. The light beam that has passed through the diffraction grating 54 is reflected by the polarization beam splitter 56, and the image rotation element 57
Pass through. The image rotator 57 is also rotatable in a plane perpendicular to the optical axis, and its rotation is controlled by driving a driving unit 58 such as an actuator.
The entire primary light is configured to be capable of fine rotation control.

The light flux that has passed through the image rotation element 57 is reflected by the mirror 5.
After being reflected by 9, the light enters the objective lens 60 and is condensed there to form a minute light spot on the magneto-optical recording medium 61. That is, 0 is formed on the magnetic layer of the magnetooptical recording medium 61.
A total of nine minute light spots of three main light spots of the next light and six sub light spots of the ± first-order lights are imaged. The objective lens 60 is configured to be movable in a focusing direction in the optical axis direction and a tracking direction orthogonal to the information track by driving a driving unit 62 such as an actuator, and focusing control and tracking control of all nine light spots are performed. The magneto-optical recording medium 61 has a single magnetic layer, or uses the exchange coupling force.
A recording medium for magnetic field modulation such as a layered structure is used. The magneto-optical recording medium 61 is rotated at a constant speed by driving a spindle motor (not shown). Reference numeral 63 is a magnetic head provided opposite to the objective lens 60 with the magneto-optical recording medium 61 interposed therebetween. The magnetic head 63 drives the magnetic head drive circuit 64 to generate an AC magnetic field having a constant frequency in synchronization with the reference clock generated by the reference clock generation circuit 65, and applies the AC magnetic field to the magneto-optical recording medium 61.

FIG. 10 is a diagram showing the nine light spots formed on the magneto-optical recording medium 61 and the magnetic field applied to the magnetic head 63. In the figure, MS1, MS2 and MS3 are main light spots by the three 0th order lights of the semiconductor lasers 51a, 51b and 51c of the laser light source 51. These main light spots are irradiated onto different information tracks by shifting the information tracks one by one. SF1 and SR1 are sub-light spots of the ± first-order light by the diffraction grating 54 of the semiconductor laser 51a, and are irradiated on both sides of the main light spot MS1 of the corresponding semiconductor laser 51a. SF2 and SR2 and S
F3 and SR3 are sub-light spots formed by the ± first-order lights of the semiconductor lasers 51b and 51c, respectively, and are applied to both sides of the corresponding main light spots MS2 and MS3. The sub-light spot SF1 precedes the main light spot MS1,
The position and the sub-light spot SR1 are located at the trailing positions. The positional relationship between other main light spots and sub light spots is also the same. The width of the information track and the diameter of each light spot are 1
Around X μm, the interval X between each main light spot is several tens of μm to 100 μm.
The distance Y between each main light spot and sub light spot is several μ
The distance is about m to several tens of μm and is set so that adjacent light spots do not cause thermal interference. A circle A shown by a broken line in the drawing is a range of effective magnetic field strength of the magnetic head 63. This range basically has only to include three main light spots, but considering the control performance of the magnetic head 63, it is desirable that the diameter of the range of the effective magnetic field strength be about several hundred μm.

Here, returning to FIG. Reference numeral 66 is a polarization beam splitter for dividing the reflected light from the magneto-optical recording medium 61 into a control optical system and a reproducing optical system. The laser beam emitted from the laser light source 51 is reflected by the magneto-optical recording medium 61, and then again guided to the polarization beam splitter 56 via the objective lens 60, the mirror 59, and the image rotation element 57. Then, it passes through the polarization beam splitter 56 and enters the polarization beam splitter 66, where the incident light flux is transmitted or reflected, the transmitted light flux is guided to the control optical system, and the reflected light flux is guided to the reproduction optical system. The transmitted light flux is condensed by the condenser lens 67 and enters the beam splitter 68. The beam splitter 68 further transmits or reflects the incident light beam, and the transmitted light beam gives the astigmatism to the cylindrical lens 6.
After passing through 9, the light is detected by the photodetector 70. This detection signal is sent to the focus error detection circuit 71, and the focusing error signal is detected. The reflected light flux reflected by the beam splitter 68 is detected by the photodetector 72,
The tracking error detection circuit 73 detects the tracking error signal based on this detection signal.

On the other hand, the light beam guided to the reproducing optical system by the polarization beam splitter 66 is rotated by 45 ° in the polarization direction by the ½ wavelength plate 74, and then is passed through the condensing lens 75 to the polarization beam splitter 76. Incident on. The polarization beam splitter 76 reflects or transmits the incident light, the reflected light is detected by the photodetector 77, and the transmitted light is detected by the photodetector 78. The obtained respective detection signals are the pre-pit detection circuit 79, the verification signal detection circuit 80 and the reproduction signal detection circuit 8
1, the signal indicating the track number, the timing pit detection signal, the verify signal,
A reproduction signal or the like is generated.

Reference numeral 97 is a recording signal modulation circuit for separating and modulating the recording signal into three signals. In this embodiment, the image information is recorded as the recording information as described above, and the image information here is divided into R (red), G (green) and B (blue) of the ternary color for each pixel. , Each of which has a gradation of 8 bits. That is, as the recording signal, R, G, and B signals are repeatedly transmitted in time series for each pixel. The recording signal modulation circuit 97 outputs this recording signal to the 3
Divide into two groups. For example, a group of 1 bit, a group of b, and a group of c may be divided in order, but here, R, G, and B are divided into 8 bits, R is a group of G, and G is a group of b. , B be a group of c. The recording signal modulation circuit 97 also modulates each group into a signal corresponding to the recording pattern on the magneto-optical recording medium 61. Then, the modulation signal of the group a is output to the laser drive circuit 98a, the modulation signal of the group b is output to the laser drive circuit 98b, and the modulation signal of the group c is output to the laser drive circuit 98c. In each laser drive circuit, the corresponding semiconductor laser is pulse-lit according to the transmitted modulation signal, and image information is recorded on the information track in combination with the application of the AC magnetic field by the magnetic head 63. This recording operation will be described later in detail.

Next, the detection operation of each servo error signal of the focus error detection circuit 71 and the track error detection circuit 73 will be described with reference to FIG. In FIG. 11, 7
Reference numeral 0'also shows an enlarged detection surface on the photodetector 70, and the photodetector 70 is composed of a four-division photodetector in which the detection surface is spatially divided into four. The four-division photodetector is divided into ten characters, and the four-division photodetector is arranged such that the division line forms an angle of 45 degrees with the information track of the magneto-optical recording medium 61. Then, this four-division photodetector detects only the central main light spot MS2 which is the 0th order light of the semiconductor laser 51b shown in FIG. In this case, each of the detection pieces 70a to 70d of the four-division photodetector is arranged at a position where the MS2 at the time of on-focus becomes the smallest random circle, and when the focus shifts to under or over, the light amount distribution of the MS2 becomes circular. Changes from landscape to portrait or vice versa.

Among the detection pieces of the four-division photodetector, the detection signals of the detection pieces 70a and 70c having diagonal positions are added by an adder 82.
Then, the detection signals of the detection pieces 70b and 70d are added by the adder 83, respectively. The sum signals obtained by the adders 82 and 83 are subtracted by a subtractor 84 to generate a focusing error signal by the so-called astigmatism method. The obtained focusing error signal is sent to the drive unit 62 shown in FIG. 1, and the objective lens 60 is driven in the focusing direction based on this error signal, whereby the focusing control of all nine light spots is performed.

Reference numeral 72 'is an enlarged view of the detection surface of the photodetector 72, and is composed of five two-divided photodetectors 85 to 89, each of which is divided into two in the track direction. Two split photodetectors 85-87 arranged in the center
Is the light spot sequence SF2, MS2, SR2 in the center of FIG.
The detection pieces 85a and 85b, the detection pieces 86a and 86b, and the detection pieces 87a and 87b, respectively.
It consists of These two-division photodetectors 85-8
7 is the main light spot MS when the light spot is on track
2. The light amount distributions of the sub light spots SF2 and SR2 are arranged so as to be located in the center thereof. Main light spot MS2
Detection pieces 86a and 86 of the two-division photodetector 86 corresponding to
The detection signal of b is subtracted by the subtractor 90 to generate a tracking error signal by the so-called push-pull method.
The obtained tracking error signal is sent to the drive unit 62, and the drive unit 62 drives the objective lens 60 in the tracking direction based on the error signal, thereby performing tracking control of all nine light spots. Also, 2
Detection pieces 85a and 87b of one of the split photodetectors 85 and 87
Of the detection signal of the other side by the adder 91.
The detection signals of 7a are added by the adder 92, and the obtained sum signal is further subtracted by the subtractor 93 to generate a tracking error signal for tracking control of the diffraction grating 54. The obtained error signal is sent to the driving unit 55, and the driving unit 55 drives the diffraction grating 54 based on this error signal, so that the diffraction grating 54 makes a minute rotation about the optical axis, and the six sub-light spots. Supplementary tracking control is performed.

Reference numeral 88 is a two-split photodetector provided corresponding to the main light spot MS1 in the first row shown in FIG. 10, and 89 is a two-split light detector provided corresponding to the main light spot MS3 in the third row. It is a photodetector. Each of these two-divided photodetectors is arranged so that the light spot is located at the center when each main light spot is on-track. The two-divided photodetectors 88 and 89 have two detection pieces 88a and 88b, respectively.
And detection pieces 89a and 89b. The detection signals of the detection piece 88a of the two-division photodetector 88 and the detection piece 89b of the two-division photodetector 89 are added by the adder 94, and the detection signals of the detection piece 88b and the detection piece 89a on the other side are added by the adder 95. Is added. Then, the sum signal obtained by the adders 94 and 95 is subtracted by the subtractor 96, and the tracking error signal of the image rotation element 57 is generated. The obtained error signal is sent to the drive unit 58, and the drive unit 58 drives the image rotation element 57 based on this error signal. As a result, the image rotator 57 finely rotates about the optical axis, and the main light spot MS
The auxiliary tracking control of 1 and MS3 is performed. Although only the main light spot MS2 is detected when performing the focusing control in the embodiment, for example, the three main light spots may be detected, and the focusing value may be used to perform the focusing control.

Next, the pre-pit detection circuit 7 shown in FIG.
9, verify signal detection circuit 80, reproduction signal detection circuit 8
The detection operation of No. 1 will be described with reference to FIG. In FIG. 12, reference numeral 77 'indicates the detection surface of the photodetector 77 of the reproduction optical system and the light spot projected on it, and 78' indicates the detection surface of the photodetector 78 and the light spot projected on it. The photodetector 77 includes detection pieces 77a and 77b corresponding to the main light spot MS1 and the sub-light spot SR1 of the light spots in the first row and the main light spot MS2 in the center row shown in FIG.
And detection pieces 77c, 77 corresponding to the sub-light spot SR2.
d, the main light spot MS3 and the sub light spot SR in the third row
It is composed of detection pieces 77e and 77f corresponding to No. 3. Similarly, in the photodetector 78, the detection pieces 78a to 7 corresponding to the main light spots MS1 to MS2 and the sub light spots SR1 to SR3 in the first to third rows are similarly processed.
It is composed of 8f.

Detection piece 77a of photodetector 77 and photodetector 7
The detection signals of the detection pieces 78a of No. 8 are subtracted by the subtractor 102 to generate a magneto-optical signal by the main light spot MS1. Similarly, the detection signals of the detection pieces 77c and 78c are the subtractor 101, and the detection signals of the detection pieces 77e and 78e are the subtractor 1.
00, the main light spots MS2 and MS3 are subtracted.
To generate a magneto-optical signal. The magneto-optical signal obtained by each subtractor is sent to the reproduction signal detecting circuit 81, where each magneto-optical signal is demodulated and the demodulated data is combined to generate a reproduction signal. The above reproduction process is of course performed during normal information reproduction, and at this time, the laser power of the semiconductor lasers 51a to 51c is set to the reproduction power.

On the other hand, when recording information, as will be described in detail later, information is recorded in parallel on three information tracks by using the main light spots MS1 to MS2. During this information recording, the detection signals of the detection pieces 77b and 78b are the subtractor 105, the detection signals of the detection pieces 77d and 78d are the subtractor 104, and the detection signals of the detection pieces 77f and 78f are the subtractor 1.
Sub-light spots SR1, SR2, SR3
To generate a magneto-optical signal. That is, the information recorded by the preceding main light spots MS1, MS2, MS3 is scanned subsequently by the sub light spots SR1 to SR.
3 is played in real time. Each subtractor 103-
The magneto-optical signal obtained at 105 is demodulated and synthesized by the verify signal detection circuit 80 to reproduce the verify signal. The obtained verify signal is sent to a verify determination circuit (not shown), where the recording signal and the verify signal are compared to perform direct verification at the same time as the recording of information.

The detection signals of the detection pieces 77a and 78a are added by the adder 109, the detection signals of the detection pieces 77c and 78c are added by the adder 110, and the detection signals of the detection pieces 77e and 78e are added by the adder 111, respectively. Main light spot MS1, M
Light intensity change signals of S2 and MS3 are generated. The obtained light amount change signal is sent to the pre-pit detection circuit 79, and the pre-pit information recorded on each information track is detected.
As a result, the prepit detection circuit 79 outputs the signal A indicating the track number and the timing pit signal A.
These pieces of pre-pit information are used during the above recording and during normal information reproduction. Further, the detection signals of the detection pieces 77b and 78b are added by the adder 106, the detection signals of the detection pieces 77d and 78d are added by the adder 107, and the detection signals of the detection pieces 77f and 78f are added by the adder 108, respectively. SR
1, SR2 and SR3 light amount change signals are generated. The pre-pit detection circuit 79 detects pre-pit information on each information track based on each light amount change signal, and outputs a signal B indicating a track number and a timing pit detection signal B. These pieces of pre-pit information are used when generating a verify signal.

Next, the specific operation of this embodiment will be described in detail with reference to the time chart shown in FIG. First,
This is a recording operation. FIG. 3A shows the reference clock generation circuit 6
5, the reference clock generated in FIG. 5 is the AC magnetic field generated in the magnetic head 63. The reference clock is output to the magnetic head drive circuit 64, and the drive circuit 64 generates an AC magnetic field having a constant frequency in synchronization with the reference clock.
It is applied to the magneto-optical recording medium 61. The reference clock is the pre-pit detection circuit 79 and the verification signal detection circuit 8.
0, the reproduction signal detection circuit 81, the recording signal modulation circuit 97, etc.

On the other hand, the optical head composed of optical elements such as the objective lens 60 shown in FIG. 9 is accessed by a moving mechanism (not shown) so that nine light spots are positioned on the indicated information track. In this case, the pre-pit detection circuit 79 detects the track number while the target 3
Although it moves to the information track of the book, the same track number is assigned to every three information tracks in this embodiment in order to record and reproduce with nine light spots at the same time.
As a result, the number of tracks to be detected can be reduced, and the circuit configuration can be simplified accordingly. Also,
The track numbers are not always detected for nine light spots. For example, in the case of rough movement, the track numbers are detected only by the central main light spot, and the central main light spot is one of the three target information tracks. After reaching any one of the information tracks, the track numbers may be respectively detected by the main light spot and the sub light spot, and the light spots may be switched to the precise control so as to be drawn onto the respective information tracks. By performing such control, the light spot can be moved onto the target information track at a higher speed. When each of the nine light spots is located on the target information track, the timing pit detection signal A in the prepit detected by the prepit detection circuit 79 is detected.
Thus, it is recognized that the main light spots MS1, MS2, MS3 have reached the recording area on the information track. FIG.
(C) shows the timing pit detection signal. The timing pits may be recorded on all the information tracks and the timing pits of the respective information tracks may be detected by the three main light spots. In this case, information recording may be started for each information track. Alternatively, the timing pit may be recorded only on the central information track, and the arrival of the three light spots in the recording area may be detected by the detection signal of the pit. At this time, the recording of information is started simultaneously for all three information tracks.

FIG. 14 is a diagram showing a state in which the timing pits are recorded in each information track.
P1, TP2, and TP3 are recorded at the same distance as the interval X between the main light spots. The sub-main spot is not shown here. If the timing pits are recorded in a state where they are aligned in the radial direction of the magneto-optical recording medium 61, the recording and reproducing timings will shift for each main light spot. Therefore, in order to correct this shift, the capacity of the buffer memory in the recording signal modulation circuit 97 and the reproduction signal detection circuit 81 increases. Therefore, as shown in FIG. 14, if the arrangement of the timing pits is arranged in parallel with the arrangement of the main light spots MS1, MS2, MS3, the start timings of recording and reproduction of the three main light spots are deviated. There is no.

Returning to FIG. FIG. 7C shows the timing pit detection signal as described above, and in the present embodiment, the central main light spot represents the timing pit as a representative. It should be noted that, at the time of detecting the pre-pit, the laser light source 51 emits a laser beam having the same constant power as that at the time of reproduction. When a timing pit is detected, each light spot is erased for the first few pulses in order to eliminate the unerased portion, then the start pit (domain) is recorded, and then the information is recorded according to the modulated signal. . FIG. 13D-1 shows a laser pulse of the semiconductor laser 51a driven by the laser drive circuit 98a. The semiconductor laser 51a has the above-mentioned light spot M.
The image of S1 is formed on the information track and is driven according to the modulation of the recording signal modulation circuit 97. Further, in the figure (d-
2) is a semiconductor laser 51b corresponding to the light spot MS2
(D-3) of the laser pulse of FIG.
Is a laser pulse of the semiconductor laser 51c corresponding to.
These laser pulses are similarly driven according to the modulation of the recording signal modulation circuit 97. Here, the high level of the main light spot by the laser pulse is high power capable of recording and erasing, and the low level is the same power as during reproduction.

In each laser pulse, the first two pulses are erasing pulses, and the AC magnetic field is applied at the peak position of negative polarity. As a result, the magnetization direction of the laser pulse irradiation portion of the main light spot of each information track becomes downward, and if there is an unerased portion of the previously recorded information, they are completely erased and the magnetization direction is returned to the initial state. . In this embodiment, the downward magnetization direction is the initial state. Figure 1
3 (e-1) is a recording pattern on the information track corresponding to the laser pulse of the main light spot MS1 by the semiconductor laser 51a. Further, (e-2) of the figure shows a recording pattern corresponding to the main light spot MS2 by the semiconductor laser 51b, and (e-3) shows a recording pattern corresponding to the main light spot MS3 of the semiconductor laser 51c. Here, the secondary light spot does not affect the formation of the recording pattern. In this recording pattern, the white areas are downward magnetic domains in the magnetization direction, and the shaded areas are upward magnetic domains in the magnetization direction. It can be seen that in the region irradiated with the two laser pulses for erasing, the magnetization direction is downward and is initialized as described above.

In each laser pulse, the third pulse is for recording a start pit indicating the start position of information recording. Since the start pit is recorded with the modulation signal "1" as shown in each laser pulse, the start pit laser pulse is emitted in time with the peak position of the positive polarity of the AC magnetic field. As a result, upward magnetic domains are formed on the three information tracks, and the upward magnetic domains are recorded only after the timing pits are detected. After this, following the laser pulse for the start pit, the information is recorded on each information track as shown in FIGS.
2), a laser pulse is emitted as shown in (d-3). As described above, these laser pulses are obtained by modulating the image information separated for each pixel of R, G, and B, and are radiated in parallel on the three information tracks. For example, in the laser pulse of FIG. 13 (d-1), after the third start pit laser pulse is first irradiated, the timing is reached at the positive peak point of the alternating magnetic field until before the next modulation signal "1". And two laser pulses are emitted. Then, the modulation signal becomes "1", and four laser pulses are emitted in time before the next modulation signal "1" at the negative peak point of the AC magnetic field. That is, the laser pulse is irradiated in such a manner that the timing is matched with the positive or negative polarity of the alternating magnetic field according to the magnetic domain to be recorded, and the magnetization direction is inverted when the modulation signal is "1". As a result, as shown in FIG. 13 (e-1), initially, the upward magnetic domains indicated by diagonal lines are recorded, and then the downward magnetic domains and the upward magnetic domains are sequentially recorded according to the modulation signal. 13 (d-2), (d
Also in the laser pulse shown in -3), magnetic domains are recorded by the same operation as described above, and the magnetic domain is recorded on each information track.
3 (e-2) and (e-3), magnetic domains are sequentially recorded.

On the other hand, when each sub-light spot passes through the timing pit, as shown in FIGS. 13 (d-1), 13 (d-2),
Since the modulation of each semiconductor laser shown in (d-3) has already started, each sub-light spot is also irradiated onto the information track as corresponding high-level and low-level laser pulses. Here, the power of the sub light spot at the high level is set to be equal to or less than the power of the main light spot at the time of reproduction. When a light intensity change signal or a magneto-optical signal is obtained by using the thus modulated light pulse, the power change of the light pulse affects the signal. For example, a high level and a low level can be obtained by using the modulated signal. By changing the amplification factor of the photodetector to obtain the detection signal, the influence of the power change on the signal can be eliminated.

When the timing pit is detected by the pre-pit detection circuit 79, the verification signal detection circuit 80 reads the start pit, and thereafter, as described with reference to FIG. 12, it is recorded by the main light spot preceding each information track. The magnetic domains are read sequentially. And 3
A reproduction signal for verification is generated by demodulating and combining the magneto-optical signals obtained in one information track. This verify signal is compared with the recording signal. As a result, if the error between the verify signal and the recording signal is more than a certain reference value, it is judged as a recording error, and the same recording position on the magneto-optical recording medium 61 or another position. Re-recording is done at the position. Although the verify signal and the recording signal are compared here, the magneto-optical signal from each information track,
You may compare with each modulation signal obtained by the recording signal modulation circuit.

Next, a normal reproducing operation will be described.
First, at the time of reproducing information, the power of the main light spot by each semiconductor laser of the laser light source 51 is set to a reproducing power of a constant intensity, and like the case of recording, three main light spots are on the designated information track. Be moved. In addition,
At this time, the secondary light spot is not used. In this way, when each light spot is moved to the target information track,
First, the timing pit detection signal is detected, and then the reproduction signal detection circuit 81 detects the start pit. As a result, the head of the magnetic domain array on the information track is detected, and thereafter, the recorded information is reproduced as described with reference to FIG. That is, in the reproduction signal detection circuit 81,
The magneto-optical signal for each information track generated at 102 is taken in and sequentially demodulated and combined, and the information recorded separately on each of the R, G, and B pixels on the three information tracks is re-recorded. It is restored to the original image information and output as a reproduction signal.

As described above, in this embodiment, the light beams of the three semiconductor lasers are divided into the 0th-order light and the ± 1st-order lights by the diffraction gratings, and the divided lights are distributed on the three information tracks. By irradiating as the main light spot and the sub light spot, information can be recorded on each information track by each main light spot, and a verify signal is generated based on the reflected light of each sub light spot to generate each information. It is possible to perform a direct verify that the recorded information on the track is immediately verified. Therefore, it is possible to verify the information on each information track while simultaneously recording on a plurality of tracks, and it is possible to greatly reduce the recording time. In addition, tracking control of each sub-light spot irradiated on the three information tracks is performed by finely rotating the diffraction grating around the optical axis based on the tracking error signal obtained based on the reflected light of the sub-light spot. Can be corrected. Furthermore, the tracking control of the main light spot can be similarly corrected by finely rotating the image rotation element about the optical axis based on the tracking error signal obtained based on the reflected light of the main light spot. . Therefore, even when the main light spot and the sub light spot are respectively radiated on the plurality of information tracks, the main light spot and the sub light spot can be accurately scanned to follow the information tracks. Recording and reproduction can be performed stably.

In the above embodiments, image information is taken as an example of the recording information, and the separated data for each pixel of R, G, B is recorded on three information tracks by using three semiconductor lasers. However, the present invention is not limited to this. For example, recording information other than image information can be recorded, and in that case, the number of information tracks to be simultaneously recorded is not limited to three, and may be arbitrarily set to be less than or more than three. Further, in this embodiment,
Although the magneto-optical recording apparatus of the magnetic field modulation optical pulse system for overwriting the magneto-optical recording medium has been described as an example, the present invention is not limited to this, and overwrites can be performed by utilizing the power change of the optical pulse. Any device that performs the above can be applied to a device using an optical modulation method or a device using a phase change medium.

FIG. 15 is a block diagram showing another embodiment of the magneto-optical recording / reproducing apparatus of the present invention. In FIG. 15, 12
Reference numeral 0 is a fixed optical system fixed in the apparatus, and reference numeral 121 is a movable optical system configured to be movable in the radial direction of a magneto-optical disk (not shown). The fixed optical system 120 is composed of a first optical head 122 and a second optical head 123. The first optical head 122 is for recording information, and the second optical head 123 is for reproducing and recording information. Used for instant playback. The structure of the first optical head 122 is as follows. First, 124 is a semiconductor laser which is a light source for recording, 125 is a collimator lens, 126 is a beam shaping prism, 127 is a polarization beam splitter, and 128.
Is a quarter-wave plate. The light beam of the semiconductor laser 124 is a linearly polarized light having a polarization direction parallel to the paper surface (hereinafter referred to as P
The polarization beam splitter 127 transmits almost 100% of the P-polarized component and linearly polarized light having a polarization direction perpendicular to the polarization direction of the P-polarized light (hereinafter referred to as “polarized light”).
S-polarized light) is used that reflects almost 100%.

The light beam emitted from the semiconductor laser 124 is collimated by the collimator lens 125 and then corrected by the beam shaping prism 126 into a circular cross section. This parallel light beam passes through the polarization beam splitter 127, and
The quarter-wave plate 128 turns the light into circularly polarized light and emits the light toward the movable optical system 121. The movable optical system 121 is provided with a mirror 129, and the incident light beam is reflected by this mirror 1.
The light is reflected by 29 in the direction perpendicular to the plane of the paper, and is further focused on a small light spot by an objective lens (not shown) to be irradiated onto a magneto-optical disk (not shown). Thus, information is recorded by irradiating a light spot on the information track of the magneto-optical disk and applying a magnetic field by a magnetic head described later. On the other hand, this light beam is reflected by the magneto-optical disk and enters the polarization beam splitter 127 via the objective lens, the mirror 129, and the quarter-wave plate 128. In this case, when passing through the quarter-wave plate 128, S
Returned to polarized light. As a result, the polarization beam splitter 1
Since the reference numeral 27 reflects almost 100% of S-polarized light due to its polarization characteristic, the reflected light from the magneto-optical disk is reflected by the condenser lens 1.
It is guided to the half prism 131 via 30.

The half prism 131 splits the incident light beam into two, and one light beam is detected by the photodetector 132. Then, a tracking error signal is generated based on the detection signal of the photodetector 132, and automatic tracking control by the so-called push-pull method is performed. Also,
By separating the frequency of the tracking control signal from the detection signal of the photodetector 132, the information such as the track address and the sector address recorded in the information track by the concave and convex pits is reproduced. The specified information track is searched based on this address information, and the light beam is accessed to the target information track. On the other hand, half prism 1
The light flux that has passed through 31 is detected by the photodetector 134 via the knife edge 133, and autofocus control by the so-called knife edge method is performed based on this detection signal.

Since the first optical head 122 is dedicated to recording, it is sufficient to irradiate circularly polarized light. Therefore, the combination of the polarization beam splitter 127 and the quarter-wave plate 128 makes it possible to return light to the semiconductor laser 124. Can be prevented. Therefore, as compared with the conventional optical head for a magneto-optical disk that radiates linearly polarized light, the transmission efficiency of light from the semiconductor laser to the magneto-optical disk can be increased, thereby reducing the maximum output of the semiconductor laser 124. You can Also, since the circularly polarized light is not emitted and the magneto-optical signal is not reproduced, the influence of the birefringence of the substrate of the magneto-optical disk is less likely to occur, so that the objective lens can be accurately positioned in the radial direction of the magneto-optical disk. The information recorded in the concave and convex pits can be accurately reproduced without moving.

The second optical head 123 will be described.
Reference numeral 135 is a semiconductor laser which is a reproducing light source, 136 is a collimator lens, 137 is a beam shaping prism, and 138 is a polarization beam splitter. The light beam of the semiconductor laser 135 is P-polarized similarly to the first optical head 122,
As the polarization beam splitter 138, a P-polarized light transmittance of 60%, a reflectance of 40%, an S-polarized light transmittance of almost 0%, and a reflectance of almost 100% are used.
The light beam of the semiconductor laser 135 is a collimator lens 13
The beam is emitted to the movable optical system 121 through the beam shaping prism 137 and the polarization beam splitter 138. This light flux is reflected by the mirror 129 of the movable optical system 121 in the direction perpendicular to the paper surface, and is further imaged as a minute light spot on the magneto-optical disk by an objective lens (not shown). The light beam reflected from the magneto-optical disk is returned again to the polarization beam splitter 138 of the second optical head 123 via the objective lens and the mirror 129, where a part of the returned light beam is reflected to the polarization beam splitter 139.

The polarization beam splitter 139 has the polarization characteristics that the transmittance of P-polarized light is 20%, the reflectance is 80%, the transmittance of S-polarized light is almost 0%, and the reflectance is almost 100%.
Therefore, here, only a part of the P-polarized light is transmitted and a part of the P-polarized light and almost all of the S-polarized light are reflected. The light flux transmitted through the polarization beam splitter 139 is guided to a control optical system composed of a condenser lens 140, a half prism 141, photodetectors 142 and 143, and a knife edge 143, and the first
Similar to the optical head 122, a servo error signal for focus control and tracking control is generated based on the detection signals of the photodetectors 142 and 144. Then, based on the obtained servo error signal, auto-tracking control by the push-pull method and auto-focusing control by the knife-edge method are performed. On the other hand, the P-polarized light beam and the S-polarized light beam reflected by the polarization beam splitter 139 are 1 /
After the polarization direction is rotated 45 degrees by the two-wave plate 145,
Polarization beam splitter 147 via condenser lens 146
Is incident on. The polarization beam splitter 147 has a transmittance of P-polarized light of about 100%, a reflectance of about 0%, a transmittance of S-polarized light of about 0%, and a reflectance of about 100%. Therefore, the light beam incident on the polarization beam splitter 147 is split into P-polarized light and S-polarized light, and the P-polarized light is S-polarized by the photodetector 148.
The polarized light is detected by the photodetector 149. The detection signals of the photodetectors 148 and 149 are sent to a signal processing circuit (not shown), where the two detection signals are differentially detected to be reproduced as a magneto-optical signal, and further binarized and demodulated. Playback data is generated by. Further, in the signal processing circuit, the detection signals of the photodetectors 148 and 149 are added to reproduce the information such as the track address and the sector address recorded by the concave and convex pits on the magneto-optical disk. Of course, reproduction can also be performed by a signal from the photodetector of the control optical system as in the case of the first optical head 122. Information tracks and sectors are searched based on the obtained address information.

Since the second optical head 123 is exclusively for reproduction, it is necessary to irradiate the magneto-optical disk with a linearly polarized light beam. Therefore, the transmission efficiency of light from the semiconductor laser 135 to the magneto-optical disk is poorer than that of the first optical head 122 due to the characteristics of the polarization beam splitter 138, but high output for recording is not required, and thus the maximum output is small. A semiconductor laser can be used. Also, since the linearly polarized light is emitted and the magneto-optical signal is reproduced, it is easily affected by the birefringence of the substrate of the magneto-optical disk. It is desirable to move it accurately. That is, as shown in FIG. 15, it is desirable that the center of the magneto-optical disk is located on the extension line of the objective lens of the second optical head 123 in the X direction.

FIG. 16 is a plan view showing the positional relationship between the magneto-optical disk and the movable optical system, and FIG. 17 is a side view thereof. In the figure, reference numeral 150 is a magneto-optical disk, not shown in FIG. The opening / closing shutter 152 is the magneto-optical disk 1.
It will be in the open state when 50 is mounted on the device. The magneto-optical disk 150 is rotated at a constant speed by driving a spindle motor (not shown). Reference numeral 121 denotes the movable optical system shown in FIG. 15, and on its upper surface, objective lenses 153a and 153b not shown in FIG. 15 are provided. The objective lens 153a corresponds to the first optical head 122, and the objective lens 153b corresponds to the second optical head 123. Then, each objective lens is provided with an actuator (not shown) for autofocusing and autotracking, and is configured to be able to independently perform autofocusing control and autotracking control. Objective lens 153 of the second optical head 123
b is the magneto-optical disk 1 on the extension line as described above.
The center of 50 is arranged so that the light beam can accurately move in the radial direction of the magneto-optical disk 150.

As shown in FIG. 17, the movable optical system 121 is constructed to be movable in the radial direction (X direction) of the magneto-optical disk 150 by driving a linear motor or the like. As a result, the light beams emitted from the first and second optical heads 122 and 123 in the fixed optical system 120 are accessed on the target information tracks. in this case,
The recording light spot of the first optical head 122 is irradiated to the position preceding the information track of the magneto-optical disk 150,
The reproduction light spot of the second optical head 123 is irradiated immediately after that with a certain distance. On the upper surface of the magneto-optical disk 150, the objective lenses 153a, 1a of the movable optical system 121 are arranged.
A magnetic head 154 is arranged opposite to 53b. In this embodiment, information can be recorded by either the magnetic field modulation method or the light modulation method, but here, the information is recorded by the magnetic field modulation method. Therefore, the magnetic head 154 generates a magnetic field modulated according to the information signal to be recorded and applies it to the magneto-optical disk 150. Of course, the recording light beam of the first optical head 122 is set to have a constant recording power. On the other hand, when recording is performed by the optical modulation method, the magnetic field of the magnetic head 154 may be a magnetic field in a fixed direction, and the intensity of the recording light beam may be modulated according to the information signal. The objective space of the two optical heads and the servo control actuator are attached to one movable optical system 121, so that the drive space of the movable optical system 121 does not increase, and the window (opening / closing of the conventional magneto-optical disk) The objective lens 153 of the two optical heads in the shutter)
a and 153b can be arranged.

Next, the specific operation of this embodiment will be described. First, the recording operation. When recording information, the movable optical system 121 moves in the radial direction of the magneto-optical disk 150, and seeks in the vicinity of the information track instructed by the control of the control unit (not shown). Then, the first and second optical heads 122 and 123 move while reading the track address and the sector address by the above-described operation, and the recording / reproducing light spots of the two optical heads are respectively positioned on the target information tracks. To be done. Next, a constant intensity light beam emitted from the first optical head 122 is scanned following the information track, and at the same time a modulation magnetic field is applied from the magnetic head 154 to record a series of information on the information track. To be done. On the other hand, the second optical head 12
The reproducing light beam emitted from 3 is scanned after the recording light spot. In the second optical head 123,
As described above, the reflected light is sequentially detected, and the signal processing circuit reproduces the recorded information based on the detected signal. That is, the information recorded by the recording light beam of the first optical head 122 is immediately reproduced by the reproduction light beam of the second optical head 123. The obtained reproduction data is sent to a verification determination circuit (not shown), and verification is performed by comparing it with the recording data. As a result of this verification, if the recording error exceeds the reference value, re-recording is performed on the same information track or another alternative track.

On the other hand, when reproducing information, the movable optical system 121 is sought once near the instructed information track, and then moved while the second optical head 123 reads the address information of the information track. Then, the light beam of the second optical head 123 is positioned on the target information track. Next, the reproduction light beam of the second optical head 123 is scanned following the target information track, the second optical head 123 detects the reflected light, and the signal processing circuit uses the detected signal as a basis. The recorded information is reproduced by performing binarization and demodulation processing. The obtained reproduction data is sequentially transferred to the outside. In the case of reproducing information, the first optical head 122 may turn off the semiconductor laser 124 to save power consumption, or in order to speed up the response to the next recording, the same information track or a track in the vicinity thereof. May be scanned with low output optical power.

As described above, in this embodiment, by irradiating the first optical head for recording only with circularly polarized light, it is possible to reduce the influence of the birefringence of the substrate of the magneto-optical disk. . Therefore, it is not necessary to move the objective lens of the first optical head accurately in the radial direction of the magneto-optical disk, and by this, the two objective lenses are attached to the same movable optical system and the objective lens of the first optical head is moved. It is possible to move the disc while deviating it from the radial direction. This brings about an effect that the entire optical system can be downsized. Further, in the first optical head, since it is possible to prevent the returning light to the semiconductor laser, it is possible to improve the light transmission efficiency as compared with the conventional one, so that the output of the semiconductor laser can be lowered and the cost can be reduced. It can be reduced. Furthermore, since only the concave and convex pits are reproduced by the first optical head, the birefringence allowance value for the optical element in the first optical head becomes large, and the cost can be reduced. In addition, since the second optical head uses a low output semiconductor laser instead of a high output semiconductor laser for recording, the cost can be reduced. Further, by mounting the objective lenses and actuators of the two optical heads in one movable optical system, the objective lenses of the two optical heads can be arranged in the conventional windows without increasing the size of the magneto-optical disk window. You can

FIG. 18 is a plan view showing another embodiment of the present invention, and FIG. 19 is a side view thereof. 1 in the embodiment of FIG.
The example in which the objective lenses of the two optical heads and the actuators for driving the same are attached to one movable optical system has been shown, but the size of the magneto-optical disk is, for example, from 5.25 inches to 3.5.
At inches or even smaller, the curvature of the track on the inner circumference of the disk becomes large, so that it is necessary to increase the driving range of each objective lens in the tracking direction, which imposes a burden on the design. Further, since the window of the protective case is also small, it is necessary to downsize the actuator of each objective lens. Therefore, in the present embodiment, in order to cope with the adverse effects caused by the miniaturization of the magneto-optical disk, the movable optical system is divided corresponding to the first and second optical heads. The details will be described below. In the figure, 155 is a 3.5-inch small-sized magneto-optical disk, 156 is its protective case, and 157 is an opening / closing shutter. The opening / closing shutter 157 is configured so that when the magneto-optical disk 155 is mounted on the apparatus main body, the entire central portion opens as shown in FIG. A base 158 is configured to be rotatable about a rotation shaft 159 by a predetermined angle θ. The first optical head 122 for recording shown in FIG. 15 is mounted on the base 158. There is.

Further, the magneto-optical disk 155 of the base 158
A mirror 160 for reflecting the recording light beam of the first optical head 122 toward the magneto-optical disk 155 is provided at the tip of the projecting portion projected on the lower surface of the disk, and the recording light beam is narrowed to a minute light spot. A movable optical system 162 including an objective lens 161 for driving the objective lens 161 and an actuator (not shown) for driving the objective lens 161 is mounted. With this structure, the base 158 is rotated about the rotation shaft 159 by driving a motor or the like, and the movable optical system 162 is moved in the radial direction of the magneto-optical disk 155. As a result, the movable optical system 162 is positioned on the target information track,
The recording light beam emitted from the first optical head 122 is emitted onto a target information track. A magnetic head 154 is arranged facing the movable optical system 162 corresponding to the first optical head 122 for recording. Also, 1
Reference numeral 63 denotes a movable optical system corresponding to the second optical head 123, on which a mirror 129 corresponding to the second optical head 123 shown in FIGS. 16 and 17, an objective lens 153b, and an actuator for driving the same are mounted. This movable optical system 163
Is moved in the radial direction (X direction) of the magneto-optical disk 155 by driving a linear motor or the like similarly to the movable optical system 121 described above, and the reproduction light beam of the second optical head 123 is applied to the target information track. It

In this embodiment, when recording information, 2
The two optical heads are accessed independently. First
In the optical head 122, the movable optical system 162 moves in the disk radial direction by rotating the base 158 as described above, and the recording light beam is irradiated onto the target information track. At the same time, the movable optical system 163 moves in the disc radial direction, and the reproducing light beam of the second optical head 123 is positioned on the same information track. Of course, the recording light beam precedes, and the reproducing light beam scans after that. As a result, information is recorded on the target information track by irradiation of the recording light beam and application of the magnetic field of the magnetic head 154, and the recorded information is reproduced by the reproduction light beam. The obtained reproduced data is compared with the recorded data and verification is performed. On the other hand, when reproducing information, only the second optical head 123 is accessed and the movable optical system 163 is positioned on the target information track.
Therefore, only the reproducing light beam is scanned on the information track and the recorded information is read. At this time, the first optical head 122 and the movable optical system 162 remain stationary at predetermined positions. Since the movable optical system is divided into two in this way, the drive range of each objective lens is not restricted, so that good tracking control can be performed even if the magneto-optical disk is downsized. Further, the movable optical system 162 moves on the circumference of a circle centering on the rotating shaft 159, but as described above, circularly polarized light is emitted as the recording light beam, and the objective lens is a disc. Since it does not have to move accurately in the radial direction of, there is no problem even with such a circular movement.

[0084]

As described above, the present invention has the following effects. (1) By driving a semiconductor laser by utilizing wavelength switching dynamics based on carrier dynamics of the semiconductor laser, light of each wavelength can be detected with low crosstalk, and a high-quality signal with high SNR can be obtained. it can. Therefore, high density of information can be achieved in the fields of optical information recording, transmission, processing, measurement and the like. (2) For recording a plurality of light beams having different wavelengths obtained by utilizing the wavelength switching dynamic characteristics of the semiconductor laser,
By irradiating the same information track or different information tracks for reproduction, it is possible to effectively perform recording and reproduction such as verifying at the same information track and simultaneous recording / reproduction at a plurality of information tracks. it can. (3) By transmitting lights of different wavelengths through optical fibers for the optical information signal and the synchronous clock signal,
When demodulating information, the information signal transmitted in synchronization with the synchronization clock can be demodulated. Therefore, the transmitted information can be accurately demodulated regardless of the jitter generated during the transmission of the optical fiber. (4) The light beams of a plurality of light sources are divided into 0th-order light and 1st-order light, and the divided lights are irradiated onto a plurality of information tracks as a main light spot and a sub-light spot, respectively, and on each information track. By recording information in the main light spot and reproducing the recording in the sub light spot, direct verification can be performed while recording in a plurality of information tracks. Therefore, it is possible to perform the instant verification while recording a large amount of information, and it is possible to greatly reduce the information recording time as compared with the conventional case. (5) Further, by finely rotating the diffraction grating and the image rotator about the optical axis based on the tracking error signals, the tracking control of the plurality of light spots respectively irradiated on the plurality of information tracks is corrected. You can Therefore, even if a plurality of light spots are respectively irradiated on a plurality of information tracks, each light spot can be made to accurately follow the information track, and information can be recorded and reproduced stably. (6) As the optical head, a first optical head for recording information and a second optical head for reproducing information are provided, and the first optical head records information with a circularly polarized light beam, thereby It is possible to reduce the influence of the birefringence of the substrate. Therefore, since the light spot does not have to be accurately moved in the radial direction of the recording medium, there are no restrictions on the structure of the optical system, and the optical system can be downsized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a semiconductor laser device of the present invention and an optical information recording / reproducing device using the same.

FIG. 2 is a diagram schematically showing an energy band near an active layer of a two-wavelength semiconductor laser used in the embodiment of FIG.

FIG. 3 is a cross-sectional view schematically showing a film structure of the two-wavelength semiconductor laser.

FIG. 4 is a diagram showing current-light output characteristics of the two-wavelength semiconductor laser.

FIG. 5 is a diagram for explaining wavelength switching dynamic characteristics of the two-wavelength semiconductor laser.

FIG. 6 is a time chart showing the operation of the semiconductor laser device of the embodiment of FIG.

FIG. 7 is a block diagram showing another embodiment of the optical information recording / reproducing apparatus of the present invention.

FIG. 8 is a configuration diagram showing an embodiment of an optical communication device of the present invention.

FIG. 9 is a block diagram showing an embodiment of a magneto-optical recording / reproducing apparatus of the present invention.

FIG. 10 is a diagram showing a light spot irradiated on the recording medium of the embodiment of FIG.

FIG. 11 is a diagram showing in detail the photodetector of the control optical system and the light spot projected on it, the focusing control circuit, and the tracking control circuit in the embodiment of FIG. 9;

FIG. 12 is a diagram showing a photodetector of a reproduction optical system and a light spot / prepit detection circuit projected on the reproduction optical system, a verify signal detection circuit, and a reproduction signal detection circuit in the embodiment of FIG. 9;

FIG. 13 is a diagram showing an information recording operation of the embodiment of FIG.

FIG. 14 is a diagram showing timing pits on the recording medium of the embodiment of FIG.

FIG. 15 is a block diagram showing another embodiment of the magneto-optical recording / reproducing apparatus of the present invention.

16 is a plan view showing a magneto-optical disk and a movable optical system of the embodiment of FIG.

FIG. 17 is a side view of FIG.

FIG. 18 is a plan view showing an example in which the first optical head in the embodiment of FIG. 15 is of a rotational movement type.

FIG. 19 is a side view of FIG.

FIG. 20 is a diagram showing an overwrite type information recording operation by an AC magnetic field and an optical pulse in a conventional example.

[Explanation of symbols]

 1 Magneto-optical disk 2 Achromatic pickup lens 4 Prism 6 2 wavelength semiconductor laser 7 Dichroic prism 17, 18 RF photodiode 19 Differential amplifier 22 Control unit 23 Modulation unit 24 High frequency oscillator 25 Semiconductor laser driver 26 Waveform processing unit 27 Demodulation unit 28 comparator 30 controller 32 coupling lens 33 optical fiber 34 prism 38, 39 sensor 42 binarization unit 43 demodulation unit 51 laser light source 54 diffraction grating 57 image rotator 60 objective lens 61 magneto-optical recording medium 63 magnetic head 70, 72, 77, 78 Photodetector 71 Focus error detection circuit 73 Track error detection circuit 79 Pre-pit detection circuit 80 Verify signal detection circuit 81 Playback signal detection circuit 97 Recording Signal modulation circuit 98a, 98b, 98c Laser drive circuit 120 Fixed optical system 121 Movable optical system 122 First optical head 123 Second optical head 124,135 Semiconductor laser 128 Quarter wave plate 129 Mirror 150,155 Magneto-optical disk 153a, 153b Objective lens 162, 163 Movable optical system

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location G11B 7/14 7247-5D 11/10 Z 9075-5D H04B 10/04 10/06 (72) Invention Person Sotoike Ikeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (11)

[Claims] 1. A semiconductor laser having energy levels different from each other and stacked including an active layer composed of a plurality of light emitting layers, a high frequency signal generating means for generating a high frequency signal of a predetermined frequency, and the high frequency. A semiconductor laser device comprising: driving means for modulating the signal width of the signal in accordance with the transmitted information signal and driving the semiconductor laser by the obtained width modulation signal. 2. An optical information recording / reproducing apparatus for recording or reproducing information by irradiating an optical information recording medium with a light beam, the active layer having a plurality of light emitting layers and having different energy units. Including and stacking semiconductor laser, high-frequency signal generating means for generating a high-frequency signal of a predetermined frequency, and modulating the signal width of this high-frequency signal according to the information signal sent, the width modulation signal obtained by the A driving means for driving the semiconductor laser and a wavelength dispersion element for dispersing a plurality of light beams emitted from the semiconductor laser and having different wavelengths by this driving by the wavelength dispersion element are provided, and the wavelength dispersion element is provided according to the information signal of the semiconductor laser. By irradiating the recording light beam and the reproducing light beam, which are modulated by the above, on the same information track or different information tracks of the recording medium, An optical information recording / reproducing apparatus characterized by simultaneously recording and reproducing information. 3. An optical communication device for transmitting an information signal via an optical fiber, wherein the semiconductor lasers have different energy levels and are laminated by including an active layer composed of a plurality of light emitting layers, and a high frequency of a predetermined frequency. A high frequency signal generating means for generating a signal, and a driving means for modulating the signal width of the high frequency signal according to the sent information signal, and driving the semiconductor laser by the obtained width modulation signal, Sensors for detecting the optical information signal and the optical signal of a constant period, which are emitted from the semiconductor laser by this driving, and whose signal width is modulated according to the information signals of different wavelengths transmitted through the optical fiber,
Clock generating means for generating the optical signal of the constant cycle as a reference clock signal based on the detection signal of the sensor, and demodulating the optical information signal based on the detection signal of the sensor, and the reference clock. An optical communication device, comprising: demodulation means for demodulating information transmitted in synchronization with a signal. 4. The optical information recording / reproducing apparatus according to claim 2, wherein the frequency of the high frequency signal generating means is at least twice the upper limit of the frequency of the transmitted information signal. 5. A plurality of light sources, a diffraction grating for dividing each light beam emitted from each light source into a 0th-order diffracted light and a 1st-order diffracted light, and a plurality of light sources divided by this diffraction grating. Spot forming means for forming 0th-order diffracted light and 1st-order diffracted light on a plurality of information tracks of a magneto-optical recording medium as a main light spot and a sub-light spot, respectively, and an irradiation portion of the plurality of light spots on the recording medium. The magnetic field applying means includes a magnetic field applying means for applying an alternating magnetic field of a predetermined frequency, and a light source driving means for pulse-driving the plurality of light sources according to signals modulated according to information signals to be recorded. By the pulse irradiation of the main light spot by applying a magnetic field and driving the light source driving means by
Information is recorded on each of a plurality of information tracks, and a verify signal is generated based on the reflected light of each sub light spot scanned after each main light spot to generate a verify signal. A magneto-optical recording / reproducing apparatus characterized by performing verification. 6. A tracking error signal is detected based on the reflected light of the main light spot in the center among the main light spots irradiated on the plurality of information tracks, and the entire main light spot and the sub light spot are tracked. 6. The magneto-optical recording / reproducing apparatus according to claim 5, which is controlled. 7. A diffractive grating having driving means for rotating the diffractive grating about an optical axis, and based on a tracking error signal obtained based on the reflected light of the sub-light spot by the drivable element. 6. The magneto-optical recording / reproducing apparatus according to claim 5, wherein the tracking control of the sub-light spots respectively radiated on the plurality of information tracks is corrected by finely rotating. 8. An image rotating element and driving means for rotating the image rotating element about an optical axis are provided in an optical path from the light source to the magneto-optical recording medium, and the main means is driven by the driving means. The tracking control of the main light spots respectively irradiated on the plurality of information tracks is corrected by rotating the image rotating element based on the tracking error signal obtained based on the reflected light of the light spots. The magneto-optical recording / reproducing apparatus according to claim 5. 9. A first light for irradiating a circularly polarized recording light beam in a magneto-optical recording / reproducing apparatus for irradiating a magneto-optical recording medium with a light beam and applying a magnetic field to record information. A head, a second optical head for irradiating a linearly polarized reproducing light beam, and a track moving direction of the recording medium, and the respective light beams of the first and second optical heads are instructed. A movable optical system for forming an image as a minute light spot on the information track,
Information is recorded by the recording light beam of the first optical head, and the recorded information is reproduced based on the reflected light of the reproduction light beam of the second optical head, so that the recorded information is immediately verified. A magneto-optical recording / reproducing apparatus characterized by the above. 10. The movable optical system is configured by integrating an objective lens for collecting a light beam corresponding to each of the first and second optical heads and an actuator for driving each objective lens. The magneto-optical recording / reproducing apparatus according to claim 9, wherein 11. The movable optical system is separated into two movable optical systems corresponding to the first and second optical heads, and the movable optical system corresponding to the first optical head rotates about a rotation axis. 10. The magneto-optical recording / reproducing apparatus according to claim 9, wherein the magneto-optical recording / reproducing apparatus is configured to move on the moving base in the track crossing direction of the recording medium.