JP3085418B2 - Optical information recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording apparatus for optically recording information on an information recording medium, and more particularly to an optical information recording apparatus which performs direct verification simultaneously with recording using one semiconductor laser as a light source. It relates to a recording device.

[0002]

2. Description of the Related Art Conventionally, in an optical information recording apparatus,
The information recording operation requires three processes of erasing, recording, and verifying. When the recording medium has a disk shape, each process requires one rotation of the disk. Therefore, it takes a long time to record information, and various studies have been made to solve this problem. For example, an overwrite recording method in which new data is overwritten on old data is known. According to this method, information can be directly recorded without the need for an erasing process. be able to. Recently, direct verification has been attempted in which verification is performed simultaneously with recording. If this direct verification and the above-mentioned overwriting method are used together, erasing, recording, and verifying can all be performed simultaneously by one rotation of the disk, and the recording time can be reduced to 1/3 of the conventional one. As a method of direct verification, for example, a recording light spot and a reproduction light spot are irradiated before and after on an information track, information is recorded by a preceding recording light spot, and recording information is recorded by a subsequent reproduction light spot. There is known a method of immediately playing back.

[0003]

However, in the above-mentioned conventional direct verify method, when two light spots for recording and reproduction are formed, two separate semiconductor lasers are used as light sources, or an array-like light source is used. Since the recording and reproduction light spots are created using the semiconductor laser described above, there is a problem that it is extremely difficult to adjust the position of the two light spots, that is, to adjust the optical system. In addition, when an array of semiconductor lasers is used, the distance between the elements cannot be reduced due to a problem of thermal interference of the semiconductor laser elements, and two light spots cannot be brought close to each other.
There is a problem that the performance of the optical system cannot be sufficiently obtained.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an optical information recording apparatus capable of performing direct verification using one semiconductor laser. .

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical information recording apparatus for irradiating an optical information recording medium with a light beam to optically record information, at least having different energy levels. A semiconductor laser having an active layer composed of two light emitting layers, and a recording signal
The reproduction light output of the first oscillation wavelength and the second oscillation wave
Laser driving means for oscillating with a long recording light output;
The light output for recording and the light output for reproduction are refracted or
The information track of the recording medium is changed by changing the diffraction angle.
Above a predetermined distance as a recording light spot and a reproduction light spot
A wavelength dispersive element for positioning at a distance;
Information is recorded at the light spot for reproduction, and
Means for verifying by reproducing the recorded information.
The laser driving means controls the semiconductor laser to a first
When oscillating with the reproduction optical output of the oscillation wavelength, the first oscillation wave
A first drive current that is greater than the long first threshold current.
When supplying and oscillating with the recording light output of the second oscillation wavelength
Is a second oscillation wavelength larger than the first drive current.
2, and a first oscillation wavelength
Supply a second drive current such that the optical output of the
As a result, the light spot for reproduction continuously emits light at the light output for reproduction.
The recording light spot is modulated according to the recording signal
This is achieved by an optical information recording device.

[0006]

[0007]

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the optical information recording apparatus of the present invention. In FIG. 1, 1
Numeral denotes a magneto-optical disk as an information recording medium, and numeral 2 denotes an objective lens for narrowing a light beam irradiated on the disk 1 to a minute light spot. 3 is a magneto-optical disk
A polarization beam splitter 4 for separating the incident light beam from the reflected light beam, a beam shaping prism 4, a collimator lens 5, and a semiconductor laser 6 provided as a recording / reproducing light source. The specific structure and characteristics of the semiconductor laser 6 will be described later in detail. Reference numeral 22 denotes a semiconductor laser drive circuit for driving the semiconductor laser 6, which drives the semiconductor laser 6 to oscillate with a recording light output and a reproduction light output having different wavelengths according to a recording signal. The reproduction light output is used as a verification light beam, and has a wavelength λ ₁
(830 nm) is a constant light output that does not record information. The recording light output has a wavelength of λ ₂ (780 nm).
Is a high-intensity modulated light output modulated by the information signal. The specific configuration and operation of the semiconductor laser drive circuit 22 will be described later in detail.

Reference numeral 7 denotes a dichroic prism on which a film having wavelength selectivity is formed. The dichroic prism 7 transmits light having a wavelength of λ ₁ as a verifying light beam to the polarizing beam splitter 8 side, and has a wavelength of λ ₂ as a recording light beam. The light is reflected to the half-wave plate 16 side. 10 is a half-wave plate, 11 is a polarization beam splitter, 12 and 14 are condenser lenses, 13 and 15 are light receiving elements, and a general differential detection optical system when the recording medium is a magneto-optical material. Is configured. In the differential detection optical system, the reflected light of lambda ₁ of the verifying light beam is wavelength detected differential, to reproduce a signal for verification. Of course, this optical system is also used for information reproduction during normal reproduction. When the recording medium is a phase change medium, only the condenser lens 12 and the light receiving element 13 are required. On the other hand, the light beam 9 reflected by the polarization beam splitter 8 is guided to a control optical system (not shown), and is used to obtain a servo error signal for auto-focusing and auto-tracking. Furthermore, 1/2-wavelength plate 16, polarization beam splitter 17, a condenser lens 18 and 20, the light receiving elements 19 and 21 is an optical system for differential detection of lambda ₂ wavelength light. Usually, when the wavelength of λ ₂ is shorter than the wavelength of λ ₁ ,
The light spot of wavelength λ ₂ on the magneto-optical disk 1 has a wavelength of λ ₁
, The light beam having the wavelength of λ ₂ has a higher reproducing ability. Therefore, the above-mentioned optical system is used in such a case to enhance the reproduction capability, and is not always necessary.

Next, a specific configuration of the semiconductor laser 6 will be described. As the semiconductor laser of this embodiment, for example, a semiconductor laser having an active layer composed of quantum well layers having two different compositions or widths can be used. FIG. 2 shows a semiconductor laser 6
FIG. 3 is a diagram showing an energy band near an active layer of a semiconductor laser. As shown in FIGS. 2 and 3, the structure of this semiconductor laser is 80 °.
GaAs well (second light emitting layer) 301 and 60 ° Al
_0.12 Ga _0.88 As well (first light emitting layer) 302 is 300Å
It is separated by an Al _0.36 Ga _0.64 As barrier 303, and the upper and lower sides are 500 ° GRIN Al _0.3 Ga _0.7
It is sandwiched between confinement layers (SCH layers) 304 and 305 of As-Al _0.5 Ga _0.5 As light / carrier. Also,
As shown in FIG. 2, the film structure of the laser is such that a 0.5 μm n ⁺ -GaAs buffer layer 3 is formed on an n ⁺ -GaAs substrate 310.
08, 1.5 μm n-Al _0.5 Ga _0.5 As lower cladding layer 306, SCH layer 304, well layer 302, barrier layer 303, well layer 302, SCH layer 305, 1.5 μm p-Al _0.5 Ga _0.5 As top The cladding layers 307, 0.
A 5 μm p ⁺ -GaAs cap layer 309 is stacked by molecular beam epitaxy. An Au / Cr electrode 311 is deposited on the p-side, and an Au-Ge / Au electrode 312 is deposited on the n-side. Note that 304, 301, 3 near the active layer
Nos. 03, 302 and 305 are not doped.

Here, when a current flows between the electrodes 312 and 311, electrons e are emitted from the first light emitting layer 302 and the second light emitting layer 30.
In the first light emitting layer 302, the electrons e and the holes h are firstly recombined, and light having a wavelength of λ ₁ (830 nm) is stimulatedly emitted. Next, when the injection current is increased, recombination of electrons e and holes h occurs in the second light emitting layer 301, and light having a wavelength of λ ₂ (780 nm) is induced and emitted. When the injection current is further increased, the oscillation of the wavelength λ ₁ stops, and the wavelength λ ₂
Only light of this type emits light. FIG. 4 schematically shows the current-light output characteristics as described above. In FIG. 4, I is a current, P ₁ , P ₂
Indicates the output of light of wavelengths λ ₁ and λ ₂ , respectively. When the current I is increased, light of the wavelength λ ₁ oscillates at the first threshold current I = I _th and then the second threshold current I = I th
_{At 1} , the light of wavelength λ ₂ oscillates. As the current further increases, the light of wavelength λ ₁ stops oscillating at I = I ₂ and the wavelength λ ₂
Only the light oscillates.

FIG. 5 shows a specific example of a semiconductor laser driving circuit .
FIG . This embodiment is an example applied to a drive circuit for driving a semiconductor laser at a high frequency in order to reduce noise of light reflected from a recording medium. In FIG.
205 is an operational amplifier, 206 is a choke coil, 207
Is a high frequency oscillator. A recording signal to be recorded on the magneto-optical disk 1 is input to the input terminal 201, and the input terminal 2
02 is input with a reproduction power setting signal from a control unit (not shown). The semiconductor laser 6 has an oscillator 207 at all times.
Supplies a high frequency predetermined sine wave signal (I ₃ -I ₁ or I ₁ -I _{0 in the} drawing) of, for example, several hundred MHz, or a square wave drive signal. Choke coil 206
Is provided so that this drive current does not leak to the operational amplifier 205 side. In the drawing, R1 is a resistor, RV1 and RV2 are semi-fixed resistors, and C is a capacitor. In the above driving circuit, when the recording signal is “0”, the reproducing state is established, so that only the wavelength light of λ ₁ is emitted with a constant light output,
_The output of the wavelength ₂ light needs to be zero. Therefore, in the playback state is inputted reproduction power reference voltage to the input terminal 202, the semiconductor laser 6 is adapted to oscillate at a reproducing power light output wavelength lambda _1. In this case, adjustment is made by the semi-fixed resistor RV2 so that high-frequency driving is performed between the driving currents I ₀ and I ₁ shown in FIG. In this adjustment, it is sufficient to find the maximum drive current that does not return the reflected light of the λ ₂ wavelength light to the light receiving element 19 or 21 shown in FIG. On the other hand, when the recording signal is "1", it adjusts the semi-fixed resistor RV1 is adapted to be a high frequency driven between the drive currents I ₁ and I ₃ in Fig. 4.

FIG. 6 shows signal waveforms at various parts of the semiconductor laser drive circuit. FIG. 6A shows a recording signal, and FIG. 6B shows a driving current of the semiconductor laser 6. When the recording signal is “0”, the reproduction power reference voltage is input to the input terminal 201, and the semiconductor laser 6 receives I ₀ as shown in FIG.
And a high frequency pulse current between I ₁ is provided. At this time, the optical output of the semiconductor laser 6 becomes a constant power output of the wavelength λ ₁ as shown in FIG. 6C, and the optical output of the wavelength λ ₂ becomes zero as shown in FIG. 6D. The optical output of the wavelength lambda ₁ is used as a verifying light beam immediately after recording. Further, when the recording signal is "1", the semiconductor laser 6 is high frequency driving current between I ₁ and I ₃ as shown in FIG. 6 (b) is supplied, as shown in FIG. 6 (d) Wavelength λ
The light output of high light intensity of ₂ . Of course, this high intensity light output is used for recording information. At this time, the light output of a current I ₁ lambda ₂ is zero, the light output of the large peak value in the current I _3. When the recording signal is “1”, the optical output of λ ₁ maintains the reproducing power as shown in FIG. 6C, and the optical output always has a constant reproducing power. In this embodiment, the optical output of the semiconductor laser 6 is a high-frequency optical pulse train,
Since the frequency is sufficiently higher than the response speed of the light receiving elements 13 and 15 in FIG. 1, the output may be effectively regarded as a constant output.

Next, the operation of the optical information recording apparatus shown in the embodiment of FIG. 1 will be described. First, when information is recorded, a recording signal is input to the semiconductor laser drive circuit 22,
The drive circuit 22 supplies a drive current as shown in FIG. 6B to the semiconductor laser 6 in response to the recording signal. As a result, the semiconductor laser 6 outputs light of wavelengths λ ₁ and λ ₂ as shown in FIGS. 6 (c) and 6 (d). After the optical output of the semiconductor laser 6 is collimated by the collimator lens 5 achromatized for the wavelengths of λ ₁ and λ ₂ , the cross-sectional shape of the light beam is corrected to a circular shape by the beam shaping prism 4. At this time, since the wavelength lights of λ ₁ and λ ₂ have different wavelengths, the refraction angle (or diffraction angle) of the beam shaping prism 4 differs due to the wavelength dispersion characteristics of the beam shaping prism 4, whereby the optical axes are not parallel to each other. , Λ ₁ and λ ₂ produce a certain angle θ. The light beam emitted from the beam shaping prism 4 is transmitted through the polarizing beam splitter 3 and is incident on the objective lens 2 achromatized for the wavelengths of λ ₁ and λ ₂ , where it is narrowed down to a minute light spot and Irradiated on the recording surface. Figure 7 shows a light spot on the recording surface, 103 light spot due to the wavelength lambda ₂ of the light beam, 104 is a light spot due to the wavelength lambda ₁ of the light beam. The distance between the light spots 103 and 104 is ftan θ, where θ is the angle by the beam shaping prism 4 and f is the focal length of the objective lens 2. Therefore, the light spots 103 and 104 are imaged at a fixed interval on the information track, the light spot 103 of the wavelength λ ₂ is imaged at the preceding position, and the light spot 104 of the wavelength λ ₁ follows. become. These light spots 103 and 104 are subjected to tracking control and focusing control, and scan on an information track while being focused on a recording surface. Reference numeral 101 denotes a guide groove for the tracking control.

Since the light spot 103 has a high light intensity light output of the wavelength λ ₂ , the recording bit 102 is recorded on the recording surface, and the light spot 104 of the wavelength λ ₁ scans the recording bit 102. At this time, information is recorded by a light modulation method by irradiation of the light spot 103 and application of a magnetic field in a fixed direction from a magnetic head (not shown).
04 is set to the reproduction power, so that no information is recorded. The reflected light from the recording surfaces of the light spots 103 and 104 passes through the objective lens 2 and the polarizing beam splitter 3
, And enters the dichroic prism 7, where only the wavelength light of λ ₁ is transmitted to the polarization beam splitter 8 due to the wavelength selection characteristics. The wavelength light of λ ₂ is 1 /
It is guided to the two-wavelength plate 16 side. In the polarization beam splitter 8, the incident light beam is split into two, and one of them is a half-wave plate 1.
The other side is guided to a control optical system (not shown) as a light beam 9 toward the 0 side. The light beam guided to the half-wave plate 10 is further split into two by a polarization beam splitter 11, and the split light beams are condensed through condensing lenses 12 and 14, respectively, to light receiving elements 13
And 15 are detected. Then, the light receiving elements 13 and 15
Are detected differentially by a differential amplifier (not shown) and reproduced as magneto-optical signals. Thus, the light spot 104 of the light having the wavelength of λ ₁ is reproduced, and the information of the recording bit recorded in the preceding light spot 103 is reproduced.
The obtained reproduction signal is sent to a verify determination circuit (not shown), where a comparison is made between the reproduction signal and the recording signal to perform verification for determining whether or not the information has been correctly recorded. That is, direct verification is performed to confirm the recording immediately after recording. As described above, the light spots 103 and 104 scan the information track at predetermined intervals, and a series of information is recorded while reproducing the recorded information of the preceding light spot 103 by the light spot 104 that follows. If a verify error is detected in this series of recording processes, processing such as re-recording at the same position or re-recording at another alternative position is performed. The light flux 9 reflected by the polarization beam splitter 8
Is guided to a control optical system, and a servo error signal for tracking and focus control is generated. Then, tracking control and focus control of the light spot are performed by a servo control circuit (not shown).

When normal information reproduction is performed, the semiconductor laser drive circuit 22 operates from I ₀ to I shown in FIG.
_The semiconductor laser 6 is driven by _one pulse drive current. As a result, the semiconductor laser 6 becomes λ as shown in FIG.
Light is emitted at a reproduction power of ₁ wavelength, and the recording surface of the optical disc 1 is irradiated with only the light spot 104 of the wavelength of ₁ shown in FIG. Therefore, during normal reproduction, the light spot 1
04 scans the information track and uses the reflected light to reproduce the information on the reproduction optical system, thereby reproducing a series of information recorded on the information track.

FIG. 8 shows another embodiment of the semiconductor laser driving circuit .
FIG . In the above embodiment, the semiconductor laser 6 is driven by the high-frequency pulse drive current. However, in this embodiment, the semiconductor laser 6 is driven in a DC manner, and the reproduction power light output of the wavelength λ ₁ and the wavelength it is an example of to obtain a recording power light output of lambda _2. In FIG.
The recording signal is input to the input terminal 201, and the operational amplifier 20
After being amplified by 5, it is applied to the semiconductor laser 6. Here, when the recording signal is “0”, the driving current to the semiconductor laser 6 is a current corresponding to the input voltage of the non-inverting input terminal of the operational amplifier 205. Driving current at this time so that I _L shown in FIG. 9, by adjusting in advance the voltage of the DC power source 208 in a semi-fixed resistor RV2, the initial setting is made. Current I _L shown in FIG. 9 is a driving current for driving in the reproducing power semiconductor laser 6, a semiconductor laser 6 at this time oscillates with the light output of a predetermined reproduction power P _R of the wavelength lambda _1, wavelength lambda Light ₂ does not oscillate. On the other hand, when the recording signal is “1”, the driving current of the semiconductor laser 6 is
The current corresponds to the sum of the non-inverting terminal input voltage and the inverting terminal input voltage of the operational amplifier 205. In this case, as the driving current becomes I _H shown in FIG. 9, is adjusted in a semi-fixed resistor RV1, therefore light in this case the wavelength lambda ₁ oscillates remains reproducing power P _R, the wavelength lambda ₂ Light oscillates at the recording power _PW .

FIGS. 10A and 10B show signal waveforms at various parts of the semiconductor laser driving circuit. FIG. 10A shows a recording signal, and FIG. 10B shows a driving current of the semiconductor laser 6. As described above, the driving current is I _L when the recording signal is “0”,
When "1" varies between I _H next, I _L and I _H. Thereby, in the semiconductor laser 6, the wavelength λ ₁
The light, as shown in FIG. 10 (c), and oscillates at all times reproduction power P _R regardless recording signal, the wavelength lambda ₂ light 10
As shown in (d), oscillation occurs at the recording power _PW only when the recording signal is "1". Therefore, even in the driving circuit of the present embodiment, as shown in FIG. 7, the light of wavelength λ ₂ can be imaged as the light spot 103, and subsequently the light of wavelength λ ₁ is imaged as the light spot 104. Thus, the direct verification using one semiconductor laser can be performed in the same manner as in the above embodiment.

In the above embodiment, an example in which the present invention is applied to an apparatus of a light modulation system based on irradiation of a light beam and application of a magnetic field has been described. However, the present invention is not limited to this. The present invention can be applied to any device that records information.

[0020]

As described above , according to the present invention , 1
Even if two semiconductor lasers are used, a simple circuit
With the raw light spot continuously emitting light, the recording light spot
Can be modulated according to the recording signal.
Can be easily and stably verified .

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of an optical information recording apparatus of the present invention.

FIG. 2 is a sectional view showing a structure of a semiconductor laser used in the embodiment of FIG.

FIG. 3 is a diagram showing an energy band near an active layer of the semiconductor laser.

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

FIG. 5 is a specific example of the semiconductor laser drive circuit of the embodiment of FIG . 1;
FIG .

FIG. 6 is a diagram showing a signal waveform of each part of the semiconductor laser drive circuit.

FIG. 7 is an explanatory diagram showing a state in which a recording light spot and a reproduction light spot having different wavelengths are irradiated on a recording surface of a recording medium.

FIG. 8 is a circuit diagram showing another example of the semiconductor laser drive circuit.
It is .

9 is a diagram showing a drive current I _L and I _H of the semiconductor laser in the semiconductor laser drive circuit of FIG.

FIG. 10 is a diagram showing signal waveforms at various parts of the semiconductor laser drive circuit of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 2 Objective lens 4 Beam shaping prism 6 Semiconductor laser 7 Dichroic prism 13, 14 Light receiving element 22 Semiconductor laser drive circuit 103, 104 Optical spot 205 Operational amplifier 207 High frequency oscillator 301 Second light emitting layer 302 First light emitting layer

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-1-154324 (JP, A) JP-A-62-109242 (JP, A) JP-A-5-114190 (JP, A) JP-A-2- 111091 (JP, A) JP-A-2-253676 (JP, A) JP-A-63-44224 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B ^7/ 12-7 / 22 G11B 11/105 H01S 3/18

Claims (2)

(57) [Claims] 1. An optical information recording apparatus for optically recording information by irradiating an optical information recording medium with a light beam, comprising an active layer comprising at least two light emitting layers having mutually different energy levels. A semiconductor laser, said
A semiconductor laser is coupled to a reproduction optical output having a first oscillation wavelength and a second
Laser drive means for oscillating with the recording light output of the oscillation wavelength
And the recording light output and the reproduction light output are refracted by wavelength.
Information on the recording medium by changing the angle or diffraction angle.
A recording light spot and a reproduction light spot on the track
A wavelength dispersion element for positioning at a predetermined interval,
While recording information with the recording light spot,
Performs verification by reproducing the recorded information with an optical spot
Means for driving the semiconductor laser.
A first threshold value of a first oscillation wavelength according to a recording signal;
A first drive current greater than the first drive current;
The second threshold current of the second oscillation wavelength larger than the current
And the optical output of the first oscillation wavelength becomes zero.
By supplying a second drive current that does not
The spot for recording is recorded while the spot continues to emit light.
An optical information recording device, which modulates according to a recording signal . 2. The method according to claim 1, wherein the first drive current is supplied to the semiconductor laser.
The optical output of the first oscillation wavelength when flowing through the
The optical output of the first oscillation wavelength when the drive current flows is equal
Selection of the first and second drive currents
3. The optical information recording apparatus according to claim 2, wherein: