JPH05189833A - Optical information recording method and recording/ reproducing apparatus - Google Patents

Abstract

PURPOSE:To realize high density recording by reading the data before rewriting and then setting a light irradiation power and a recording pulse width depending on the relationship between the condition before rewriting and data to be rewritten. CONSTITUTION:On the basis of the relationship between data B before rewriting and data C to be rewritten for each pit cell, a drive current is selcted from two kinds of currents and a high output semiconductor laser 15 near the wavelength of 800nm is modulated by a drive circuit 18 depending on this current setting value. In this case, the reflected light from a magneto-optical disk 2 of the condensed beam of a low output semiconductor laser 16 near the wavelength of 680nm is reflected by a beam splitter 10 through a quarter (1/4) wavelength plate 11 and is then received by a photo-detector 14. A spot diameter of condensed light beam near the wavelength of 680nm becomes small as much as the wavelength. Thereby, it becomes possible to reproduce a small pit and high recording density can also be realized.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an overwritable magneto-optical recording medium using an exchange coupling alternating multilayer film,
The present invention relates to a recording method and a recording / reproducing apparatus that enable high density recording.

[0002]

2. Description of the Related Art In a magneto-optical disk device, a magneto-optical recording film made of a perpendicularly magnetized film such as a TbFeCo thin film is formed on a transparent disk-shaped substrate made of glass, polycarbonate or the like, and is condensed through an optical head. The magneto-optical recording film is irradiated onto the magneto-optical recording film through the transparent substrate at the same time as the light spot focused by the lens is applied, and at the same time, the bias magnetic field generating coil applies a bias magnetic field to the magneto-optical recording film in the vertical direction. It is a new filing device that records the magnetization direction of data as data, and has major features such as large capacity, rewritability, and disk replaceability.

However, in the case of the generally used optical power modulation recording method, when rewriting information, a focused laser beam is irradiated while applying an erasing bias magnetic field -He once to irradiate the irradiated area with a Curie temperature. After the temperature is increased to the above, in the process of cooling the magneto-optical recording film, an erase operation is performed in which the direction of the magnetization is uniformly aligned with the direction of the erase bias magnetic field, and then the recording bias in the direction opposite to the erase bias magnetic field is applied. Information is recorded as the direction of magnetization by applying a magnetic field Hw to turn the laser beam on and off.

Therefore, since overwriting cannot be performed in this method, the transfer rate is effectively reduced during recording. On the other hand, if overwriting is possible, both recording and playback can be performed at the same transfer rate.
The data transfer speed is improved and it can be applied to a wider range of fields.

Therefore, in order to enable overwriting, some methods have been proposed so far. As one of the methods, Masatoshi Sato et al., "Single Beam Overwrite Method Using Multilayer Magneto-optical Recording Medium", 34th
Proceedings of the Second Joint Lecture on Applied Physics No. 28p-ZL
-3, page 721 (1987), an optical power modulation method using an exchange coupling multilayer film is known. This method will be described with reference to FIGS. 3 and 4.

FIG. 3 is a principle diagram showing a recording process of the exchange coupling multilayer film.

In FIG. 3, the moving direction of the magneto-optical recording medium 32 advances from right to left as indicated by an arrow 31. The magneto-optical recording medium 32 includes a memory layer 33 and an auxiliary layer 34.
It consists of Arrows written in the memory layer 33 and the auxiliary layer 34 in FIG. 3 respectively indicate the directions of magnetization. The upward magnetization is defined as a "1" level recording state, and the downward magnetization is defined as a "0" level recording state. Reference numeral 35 is an initializing magnetic circuit, 36 is a bias magnetic field applying magnetic circuit, and arrows 39 and 40 indicate the directions of the respective magnetic fields. A condenser lens 37 condenses a light spot 38 from a laser (not shown) on the magneto-optical recording medium 32.

Next, the operation of recording information will be described.

In FIG. 3A, first, the initialization magnetic circuit 35 for generating a cooperative magnetic field strength initializes the magnetization of the auxiliary layer 34 in a certain direction. Next, the recording light spot 38 is modulated corresponding to the levels of "0" and "1",
Information is written by the magnetization of the auxiliary layer 34 or the action of the magnetic field by the bias magnetic field applying magnetic circuit 36.

For example, when recording at "1" level, as shown in FIG. 3B, the power emitted from the laser is set to a high level and the light spot 38 condensed by the condenser lens 37 is used. Memory layer 33 and auxiliary layer 3
Both of the two layers 4 and 4 are heated to the Curie temperature or higher, and the magnetic fields of the bias magnetic field applying magnetic circuit 36 in the cooling process cause the two layers of the auxiliary layer 34 and the memory layer 33 to be magnetized upward.

On the other hand, when recording "0" level,
As shown in FIG. 3C, the power emitted from the laser is set to a low level, and the light spot 38 condensed by the condenser lens 37 raises only the memory layer 33 to the Curie temperature or higher. Recording is performed by inducing downward magnetization by spin interaction with the magnetization of the auxiliary layer 34.

Through the above process, overwriting with a single beam becomes possible.

FIG. 4 shows a method of overwriting information by a single beam. With respect to the data C to be rewritten, the recording power Pw having a high power level and the erasing power Pe (Pw> P) having a low power level as shown in the modulation waveform F
Information is overwritten by modulating the binary optical power of e) and irradiating it on the magneto-optical recording film.

FIG. 5 shows a block diagram of an example of a conventional optical information recording / reproducing apparatus. An optical information recording / reproducing apparatus includes a magneto-optical disk 1, a spindle motor 2 for rotating the optical disk 1, an optical head 3 for recording and erasing information and reading a signal by focusing laser light on the optical disk 1, and an optical head. Three
Positioner 4 and semiconductor laser 2 for controlling the
It is composed of a semiconductor laser drive unit 6 for modulating the emission power of the laser beam 5, and a reproduction signal control unit 7.

The semiconductor laser drive unit 6 is composed of an encoder 17 and a drive circuit 18, and the recorded data is encoded by the encoder 1.
7 is converted into a code signal C, and the semiconductor laser 25 is modulated by the drive circuit 18.

The optical head 3 comprises a semiconductor laser 25, a collimator lens 9, a beam splitter 10, and a quarter wave plate 1.
1, objective lens 12, actuator 13, photodetector 1
It is composed of 4.

The laser light from the semiconductor laser 25 is converted into parallel light by the collimator lens 9, and the beam splitter 1
The light passes through the 0, 1/4 wave plate 11 and is focused on the magneto-optical disk 1 by the objective lens 12. The focused light from the optical head 3 is focused on a predetermined position on the magneto-optical disk 1 based on the focus and tracking error signals (not shown) detected by the optical head 3 and the actuator 13 And is positioned by the positioner 4. The reflected light from the magneto-optical disk 1 passes through the objective lens 12 and the quarter-wave plate 11 and then the beam splitter 10
And is received by the photodetector 14.

The reproduction signal control section 7 comprises a preamplifier 22 and a demodulator 24. The reproduction signal photoelectrically converted by the photodetector 14 is amplified by the preamplifier 22 and the demodulator 24 reproduces the data. Be seen.

Here, as a required specification of the next-generation optical disc, overwrite is also an important item, but higher density and larger capacity are more important issues. In order to increase the density, it is necessary to miniaturize the light spot for reading information. Even if a large spot is used, it is possible to record a small pit to some extent. However, in a large spot, it is difficult to read a small pit due to interference of reproduced waveform. On the other hand, the light spot diameter φ is proportional to the wavelength λ of the light source and inversely proportional to the NA of the objective lens, as shown in the equation (1). φ = k · λ / NA (k: const) (1) Therefore, in order to increase the density, it is conceivable to shorten the wavelength of the light for reading information or increase the NA of the objective lens. Here, the method of increasing the NA is not practical because conditions for surface wobbling and the like become strict. Therefore, it is conceivable to shorten the wavelength of the reproduction light. When a semiconductor laser is targeted for downsizing and cost reduction of a device, an emission power sufficient for recording can be obtained for a semiconductor laser around 800 nm which is generally used for optical disks at present, but a short wavelength semiconductor laser around 670 nm. At present, the emission power is not more than 10 mW, which is not sufficient for recording.

Therefore, for recording and erasing data, a light spot of a semiconductor laser having a wavelength of about 800 nm, which gives a sufficient emission power, is used. On the other hand, for reproducing data, a visible semiconductor laser of about 670 nm capable of reducing the light spot diameter. There is a method of using a light spot according to. As a result, high-density recording / reproduction can be performed by the shortened wavelength.

Further, when recording, as shown in FIG. 6, for recording data C, the DUTY in one pit cell
By adjusting the recording power, the pulse train recording compensation method is used for optimum recording. For example,
With 1/7 NRZI modulation, there are seven types of recording pulse widths from 1 Tp to 4 Tp, so two at 1 Tp, 1.5 Tp.
Is used for recording with three pulses, and with 8 pulses at 4 Tp. With this recording compensation method, the amount of jitter is reduced, the phase margin is improved, and a high recording density can be realized, as compared with the recording method which has been conventionally performed.

[0022]

The above-mentioned magneto-optical recording medium using the exchange-coupling alternating multilayer film is composed of a high level recording power Pw and an intermediate level erasing power Pe when rewriting information. Overwriting is possible by performing three-level optical modulation. However, as compared with the conventional non-overwritable magneto-optical recording medium that records at a binary level with the recording power Pw, the C / N ratio is low, the resolution is poor, and it is difficult to achieve high density. There was a point.

When pulse train recording compensation is performed,
There is a problem in that the life of the semiconductor laser is shortened because it requires more recording power than before.

The object of the present invention is to read the data before rewriting and rewrite it to the state before rewriting, just before rewriting the information, by using the reproducing short wavelength light beam used for realizing the high recording density. Based on the data
By setting the light irradiation power and recording pulse width, there is no unerased pre-data and good recording characteristics are obtained.
Another object of the present invention is to provide an optical information recording method and a recording / reproducing apparatus which can reduce the load on the semiconductor laser and extend the life of the semiconductor laser.

[0025]

DISCLOSURE OF THE INVENTION The present invention provides an overwritable magneto-optical recording medium comprising an exchange coupling alternating multilayer film,
This is a recording method for overwriting a signal by irradiation of a light beam, and is characterized in that the light irradiation power and the recording pulse width are set based on the relationship between the state before rewriting and the data to be rewritten.

Further, the present invention is a recording / reproducing apparatus for overwriting a signal on a magneto-optical recording medium which can be overwritten by an exchange-coupling alternating multilayer film, by irradiating a light beam with information on the exchange-coupling alternating multilayer film surface. A first beam from a first semiconductor laser having a sufficient emission power for recording and erasing, and a converging beam with a low emission power for reproducing information on the exchange-coupling alternating multilayer film surface. A second beam from a second semiconductor laser capable of narrowing the light and two light beams from the light source of the two wavelengths to record and erase information on the exchange-coupling alternating multilayer film surface,
An optical system for guiding the light onto the exchange-coupling alternating multilayer film surface for reproduction, and for capturing and processing reflected light from the exchange-coupling alternating multilayer film surface, and the two light beams for the exchange-coupling alternating multilayer film. A positioner that moves an optical system so that a predetermined position on the surface is irradiated, a clock generation unit that generates a clock from information read from the exchange coupling alternating multilayer film by the second light beam, and the first A reproduction signal control unit that demodulates the information read by the second light beam into reproduction data, a timing adjustment unit that matches the timing of the reproduction data read by the second light beam with the data to be rewritten, and the reproduction before rewriting. Based on the relationship between the state of No. 1 and the data to be rewritten, the power setting unit for setting the light irradiation power and the recording pulse width, and the current value set by the power setting unit are DOO in, characterized in that it is composed of a semiconductor laser driving unit for driving the first semiconductor laser.

[0027]

In the magneto-optical recording medium which can be overwritten by the exchange-coupling alternating multilayer film, the pre-data is erased once and the erasing power Pe of the intermediate level is applied like the conventional magneto-optical recording medium which cannot be overwritten. Instead, by performing the binary recording of the recording power Pw and the reproducing power Pr, the C / N ratio is high, the resolution is high, and the jitter is high, as compared with the case of the ternary recording including the erasing power Pe. It is confirmed that it will decrease.

For example, FIGS. 7 and 8 show a case where overwriting is performed in ternary recording on a magneto-optical recording medium using an exchange coupling alternating multilayer film, and a case where predata is erased and then binary recording is performed. 2 shows the evaluation results of the recording frequency dependence of the C / N ratio and the signal amplitude when recorded in FIG.

From these evaluation results, when the state before rewriting and the data to be rewritten are the same, the C / N ratio is higher and the resolving power is higher if the required optical power is applied only when they are different from each other without applying the optical power. You can see that it is getting higher. Furthermore, by doing so, the irradiation time of the semiconductor laser can be reduced.

Therefore, a clock is generated from the reproduced data, and the light irradiation power or the recording pulse width is set for each pit cell based on the relationship between the state before rewriting and the data to be rewritten. It is possible to obtain good characteristics without performing unerased pre-data, as compared with

According to the optical information recording method and the recording / reproducing apparatus of the present invention, when the data is overwritten on the exchange-coupling alternating multilayer film, good recording / reproducing characteristics can be obtained without any unerased pre-data. It is possible to realize the recording density. Further, since the laser irradiation time is reduced, it is possible to improve the laser life.

[0032]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a conceptual diagram showing an embodiment of a recording method for an overwritable magneto-optical recording medium using an exchange coupling alternating multilayer film according to the present invention.

In FIG. 1, A is a pit before rewriting, and the portion in which the magnetization state is upward is shown by hatching.
The clock G is generated from the reproduced data. By this clock, the data B before rewriting is obtained for each pit cell. C is code data to be recorded, which is generated by the encoder from the recording data signal. D is the light emission power actually applied to the magneto-optical recording medium, and the emission power and the recording pulse width are determined by comparing the data before rewriting and the data to be rewritten for each pit cell. By irradiating this optical power, the pit E after rewriting is obtained and overwriting is realized.

Here, the emission power D is determined as follows. From the relationship between the state before rewriting and the data to be rewritten in a certain pit cell, the relationship of the light irradiation power in that pit cell is as shown in Table 1.

[0036]

[Table 1]

That is, when the state before rewriting and the data to be rewritten are the same, the state before rewriting is maintained by setting the light irradiation power to zero. When the magnetization state before rewriting is downward and the data to be rewritten is upward, by adding the recording power Pw1 to the pit cell with a pulse width of a certain appropriate DUTY ratio,
The magnetization state is upward. Furthermore, if the magnetization state before rewriting is upward and the data to be rewritten is downward,
By adding the erasing power Pe1, the magnetization state becomes downward, following the direction of the auxiliary layer. As described above, overwriting can be realized without erasing the pre-data.

For a magneto-optical recording medium using an exchange-coupling alternating multilayer film as in this embodiment,
Data before rewriting is read, and from the relationship between the state before rewriting and the data to be rewritten, by setting the light irradiation power and the recording pulse width, the pre-erasure of the pre-data can be eliminated rather than overwriting at the conventional three-level level. Without it, good characteristics can be obtained and high density recording can be realized. Further, since the laser irradiation time is reduced, it becomes possible to extend the life of the laser.

FIG. 2 is a block diagram showing an embodiment of a recording / reproducing apparatus for an overwritable magneto-optical recording medium using an exchange coupling alternating multilayer film according to the present invention.

This recording / reproducing apparatus comprises a magneto-optical disk 1,
A spindle motor 2 for rotating the magneto-optical disk 1, an optical head 3 for condensing laser light on the magneto-optical disk 1 to record / erase information and read signals, and a positioner for controlling the optical head 3 to a predetermined position. 4, a semiconductor laser drive unit 6 for modulating the emission power of the semiconductor laser array 5, a reproduction signal control unit 7, and a bias magnetic field applying magnetic circuit 8.

The optical head 3 comprises a semiconductor laser array 5, a collimator lens 9, a beam splitter 10, a quarter-wave plate 11, an objective lens 12, an actuator 13, and a photodetector 14. The semiconductor laser array 5 is
It has a two-beam configuration including a high-output semiconductor laser 15 having a wavelength near 800 nm and a low-output semiconductor laser 16 having a wavelength near 680 nm.

The semiconductor laser drive unit 6 is composed of an encoder 17, drive circuits 18 and 19, a power setting unit 20, and a timing adjusting unit 21. The drive circuit 19 keeps the low-power semiconductor laser 16 having a wavelength around 680 nm constant at a power suitable for reproducing information.

The two laser beams from the semiconductor laser array 5 are collimated by the collimator lens 9, pass through the beam splitter 10 and the quarter-wave plate 11, and are focused on the magneto-optical disk 1 by the objective lens 12. .. The focused light from the optical head 3 is focused on a predetermined position on the magneto-optical disk 1 based on the focus and tracking error signals (not shown) detected by the optical head 3 and the actuator 13 and It is positioned by the positioner 4. Then, the focused beam of the low-power semiconductor laser 16 having a wavelength of about 680 nm has a wavelength of 800 nm.
For the focused beam of the high-power semiconductor laser 15 in the vicinity,
It is arranged on the same track so as to be on the front side in the rotation direction of the magneto-optical disk 1.

The reflected light from the magneto-optical disk 1 of the focused beam of the low-power semiconductor laser 16 having a wavelength near 680 nm is
After passing through the objective lens 12 and the quarter-wave plate 11, it is reflected by the beam splitter 10 and received by the photodetector 14. The focused spot diameter of the beam near the wavelength of 680 nm is
Since the size is reduced by the wavelength, it is possible to reproduce a small pit, and it is possible to increase the density.

The reproduction signal control unit 7 includes preamplifiers 22 and P.
The photodetector 1 includes an LO 23 and a demodulator 24.
The reproduced signal photoelectrically converted in 4 is amplified in the preamplifier 22, a clock is generated in the PLO 23, and data is reproduced by the demodulator 24 based on the clock.

Here, an example of the power setting unit 20 for rewriting information on the magneto-optical disk 1 will be described with reference to FIG.

The power setting section shown in FIG. 9 comprises a logic circuit 91 such as PAL, two current setting sections 92 and 93, and two switches 94 and 95.

Here, the semiconductor laser is in a laser emission region for a current above a certain value called a threshold value, and the output power increases in proportion to the current value. Therefore,
The emission power can be uniquely determined for the applied current. The current setting units 92 and 93 are used for the magneto-optical disk 1
As the upper emission power, Pw1 and Pw shown in FIG.
The currents Iw1 and Ie1 for driving the high-power semiconductor laser 15 having a wavelength of about 800 nm such that it becomes e1 are set.

A method of selecting such two kinds of current setting sections will be described below.

As described above, the data B before rewriting is obtained from the pit A recorded on the magneto-optical disk 1, and the state before rewriting can be known. The recording data to be newly rewritten is converted into the code signal C by the encoder 17.

Here, the spot distance between the two light beams on the magneto-optical disk 1 is about 20 μm. Therefore, for example, in the case of a 5.25-inch optical disc, the time difference between the two light beams is 2 m under the current specifications.
It is about s. In consideration of the delay in the circuit, the position of the read data before rewriting on the magneto-optical disk 1 and the position of the data to be rewritten on the magneto-optical disk 1 are matched by the timing adjusting unit 21 including a delay line or the like. Since the adjustment amount varies depending on the linear velocity, the linear velocity is obtained from the position of the optical head and the adjustment amount is adjusted by a variable delay line or the like.

Data B thus obtained before rewriting
From the combination with the data C to be rewritten, the corresponding current setting unit is selected from two types through the logic circuit 91 such as PAL.

For example, with respect to the data B before rewriting and the data C to be rewritten, the upward magnetization portion corresponds to H and the downward magnetization portion corresponds to L, respectively. For each pit cell, the state before rewriting and the data to be rewritten are compared, and if the state before rewriting and the data to be rewritten are the same, neither switch is selected by the logic circuit 91, and the light irradiation power becomes zero. When the state before rewriting is the downward magnetization L and the data to be rewritten corresponds to the upward magnetization H, the logic circuit 91.
Outputs a signal for activating only the switch 94 to set the current Iw1 of the current setting unit 92,
The irradiation power becomes Pw1. This current Iw1 is adapted to be applied to the pit cell at an appropriate DUTY ratio. Further, when the state before rewriting is the upward magnetization H and the data to be rewritten is the downward magnetization L,
A signal that activates only the switch 95 is output, the current Ie1 of the current setting unit 93 is set, and the irradiation power becomes Pe1.

As described above, based on the relationship between the data B before rewriting and the data C to be rewritten for each pit cell,
A drive current is selected from two types, and the drive circuit 18 modulates the high-power semiconductor laser 15 having a wavelength near 800 nm as shown in D of FIG. 1 based on the current setting value.

As another embodiment, a wavelength of 800 nm
There is a method in which an optical system is assembled using two semiconductor lasers, a high-power semiconductor laser in the vicinity and a low-power semiconductor laser in the vicinity of a wavelength of 680 nm, and the same operation is performed.

[0056]

As described above, according to the optical information recording method and the recording / reproducing apparatus of the present invention, the magneto-optical recording medium using the overwritable exchange-coupling alternating multilayer film before the rewriting is performed. From the relationship between the state before reading and rewriting data and the data to be rewritten, by setting the light irradiation power and the recording pulse width, there is no pre-erasure of pre-data, rather than overwriting at the conventional ternary level. There is an effect that good characteristics can be obtained and high density recording can be realized. Further, since the laser irradiation time is reduced, there is an effect that the life of the laser is extended.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of an optical information recording method according to the present invention.

FIG. 2 is a configuration diagram showing an embodiment of an optical information recording / reproducing apparatus according to the present invention.

FIG. 3 is a principle diagram illustrating an optical modulation overwrite using an exchange coupling alternating multilayer film.

FIG. 4 is a diagram showing a conventional recording method of light modulation overwrite using an exchange coupling alternating multilayer film.

FIG. 5 is a block diagram of a conventional optical information recording / reproducing apparatus.

FIG. 6 is a diagram showing the principle of a pulse train recording compensation method.

FIG. 7 is a graph showing an example of recording frequency characteristics of C / N ratio in the case of ternary recording and in the case of binary recording.

FIG. 8 is a graph showing an example of recording frequency characteristics of signal amplitude in the case of ternary recording and in the case of binary recording.

FIG. 9 is a conceptual diagram showing an embodiment of a power setting section of the optical information recording / reproducing apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 2 Spindle motor 3 Optical head 4 Positioner 5 Semiconductor laser array 6 Semiconductor laser drive unit 7 Playback signal control unit 8 Magnetic circuit for applying bias magnetic field 9 Collimator lens 10 Beam splitter 11 1/4 wavelength plate 12 Objective lens 13 Actuator 14 Photodetector 15 High-power semiconductor laser near wavelength 800 nm 16 Low-power semiconductor laser near wavelength 680 nm 17 Encoder 18, 19 Drive circuit 20 Power setting part 21 Timing adjusting part 22 Preamplifier 23 PLO 24 Demodulator 31 Medium traveling direction 32 Magneto-optical recording medium 33 Memory layer 34 Auxiliary layer 35 Initializing magnetic circuit 36 Bias magnetic field applying magnetic circuit 37 Condenser lens 38 Light spot 39, 40 Arrow 91 Logic circuit 92, 93 Current setting section 94, 95 Switch A rewriting pit F modulation waveform G clock before the pit B before rewriting data C recorded data D light modulated waveform E rewritten

Claims (2)

[Claims] 1. A recording method in which a signal is overwritten on a magneto-optical recording medium capable of overwriting by an exchange coupling alternating multilayer film by irradiation of a light beam, and a relationship between a state before rewriting and data to be rewritten,
An optical information recording method characterized by setting a light irradiation power and a recording pulse width. 2. A recording / reproducing apparatus for overwriting a signal on a magneto-optical recording medium which can be overwritten by an exchange-coupling alternating multilayer film by irradiating a light beam, wherein information is recorded and erased on the exchange-coupling alternating multilayer film surface. A first beam from a first semiconductor laser having an emission power sufficient for recording for performing, and an emission power for reproducing information on the exchange-coupling alternating multilayer film surface is low, but a focused beam is focused. The second that can be done
A second beam from the semiconductor laser and two light beams from the two-wavelength light source onto the exchange-coupling alternating multilayer film surface for recording, erasing, and reproducing information on the exchange-coupling alternating multilayer film surface. An optical system for taking in and processing reflected light from the exchange-coupling alternating multilayer film surface, and an optical system for irradiating the two light beams at predetermined positions on the exchange-coupling alternating multilayer film surface. , A clock generator that generates a clock from the information read from the exchange-coupling alternating multilayer film with the second light beam, and the information read with the second light beam is demodulated to reproduction data. A reproduction signal control unit, a timing adjustment unit that matches the timing of the reproduction data read by the second light beam with the data to be rewritten, and the reproduction state before rewriting A power setting unit that sets the light irradiation power and the recording pulse width based on the relationship with the data to be rewritten, and a semiconductor laser drive unit that drives the first semiconductor laser based on the current value set by the power setting unit. An optical information recording / reproducing apparatus comprising: