JPH0877581A - Two beam information recording/reproducing device - Google Patents

Abstract

PURPOSE: To provide a two beam information recording/reproducing device capable of simultaneously excellently performing erasure/record/verification or record/verification even when an optical head is constituted using a simple and inexpensive optical element so as to have a color aberration. CONSTITUTION: By inclining a lining direction of light emission points 2, 3 of a monolithic semiconductor laser 1 for a surface perpendicular to an optical axis 0 of an optical head optical system by an angle θ, the deviation between focus positions of two light spots 10, 11 in the direction of the optical axis based on the color aberration when information is recorded is compensated, and focusing is controlled so that a preceding light spot 10 is focused when the information is recorded, and the focusing is controlled so that a succeeding light spot 11 is focused when the information is reproduced. When the information is recorded, recording is performed by the light spot 10, and a focus error detection signal is obtained, and the verification is performed by the light spot 11, and when the information is reproduced, the focus error detection signal is obtained by the light spot 10, and an information regenerative signal is obtained by the light spot 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-beam information recording / reproducing device. The two-beam information recording / reproducing apparatus of the present invention particularly forms two light spots on a recording medium by using an optical head using a monolithic semiconductor laser array having two light emitting points as a light source, and performs erase / record / verify. Alternatively, it is suitable for simultaneously performing recording / verifying.

[0002]

2. Description of the Related Art An optical disk device or a magneto-optical disk device is used as a data file device by taking advantage of its features of large capacity, non-contact and high speed access. In a magneto-optical disk device, when an optical head that irradiates a single light beam is used, normally, in order to record data, old information is erased, new information is recorded, and the new recorded information is confirmed. Playback for (verify),
Each time, the magneto-optical disk is rotated once, that is, three times in total, or the old information is erased and the new information is recorded in one.
This is performed simultaneously during the rotation, and the verify reproduction is performed at the next one rotation. Therefore, in such a conventional magneto-optical disk device, a waiting time for rotating the magneto-optical disk is required, which is an obstacle in improving the data transfer rate.

Therefore, an optical head capable of simultaneously performing erasing / recording / verifying or recording / verifying by using an optical head for irradiating a plurality of light beams is disclosed, for example, in Japanese Patent Laid-Open No. 58-220247. Kaisho 64-82348
It is proposed in Japanese Patent Laid-Open No. 5-114159 and the like. 6 and 7 are schematic views showing an example of a multi-beam optical head disclosed in Japanese Patent Laid-Open No. 5-114159, FIG. 6 is a plan view, and FIG. 7 is a front view (* in FIG. 6). It is the view seen from the seal side).

In FIGS. 6 and 7, the monolithic semiconductor laser 1 has light emitting points 2 and 3. Each emission point 2,
The two light beams emitted from 3 are made into substantially parallel light beams by the collimator lens 4, transmitted through the beam splitter 5 with a beam shaping unit, and reflected by the mirror 6. The alternate long and short dash line indicates the optical axis O of the outward optical system. The two beams reflected by the mirror 6 are focused by the objective lens 7 onto a predetermined track 9 of the magneto-optical disk 8 as a recording spot 10 and a reproducing spot 11. The spot 10 corresponds to the light emitting point 3, and the spot 11 corresponds to the light emitting point 2. These two
Recording and reproduction can be performed simultaneously by one spot.

The reflected beams of the two spots 10 and 11 are again made into a substantially parallel light beam by the objective lens 7, reflected by the mirror 6, and this time, the beam splitter 5 with a beam shaping section.
And is incident on the beam splitter 12. The beam transmitted through the beam splitter 12 has a convex lens 13,
It is guided to a servo error signal detection system including a cylindrical lens 14 and a servo sensor 15. On the other hand, the beam reflected by the beam splitter 12 is the birefringent crystal 1
6, the convex lens 17 and the RF sensor 18 lead to an information signal detection system.

In FIG. 7, reference numeral 19 is an external magnetic circuit for applying a magnetic field to a predetermined recording position on the magneto-optical disk 8.

Here, of the two spots 10 and 11, the spot 10 precedes the spot 11 relative to the rotating magneto-optical disk 8 (that is, first at a specific position on the track 9). Scanning with spot 10 is performed and then immediately scanning with spot 11). When recording data, light emission point 3 is spot 1
0 emits light so as to have recording power, and the light emitting point 2 emits light so that the spot 11 has reproducing power. At the same time, the magnetic field modulated with the data information is applied by the external magnetic circuit 19. At this time, a so-called servo signal (focus error indication output signal) is obtained from the reflected light of the spot 10, and an information reproducing signal for verifying the recording performed by the spot 10 is obtained from the reflected light of the spot 11. As a result, the erasing of the old information, the recording of the new information, and the reproduction for verifying the new recorded information are simultaneously achieved. Further, during normal reproduction, both the light emitting points 2 and 3 emit light so that the spots 10 and 11 have reproduction power, and a servo signal is obtained from the reflected light of the spot 10 and an information reproduction signal is obtained from the reflected light of the spot 11. .

[0008]

By the way, generally, in the optical system as shown in FIGS. 6 and 7, the light utilization efficiency of the forward optical system is about 30 to 40% and the recording power is 6 to 10 mW.
The reproduction power is set to about 1.5 mW. Therefore, the light utilization efficiency of the outward optical system is 35% and the recording power is 8
When the mW and the reproducing power are 1.5 mW, the emission powers of the light emitting point 3 and the light emitting point 2 are 22.9 mW and 4.
It becomes 3mW. The power dependence of the wavelength of the semiconductor laser is 0.1 to 0.3 nm / mW, which is 0.2
nm / mW, the wavelength difference Δ of the light from the light emitting points 2 and 3
λ is about 3.7 nm. In this case, due to the chromatic aberration of the collimator lens 4 and the objective lens 7, at the time of recording,
As shown in the conceptual diagram of FIG. 8, the image formation point is displaced by Δf. Therefore, since the information for focus control is obtained at the spot 10, the spot 11 is defocused,
If the recording / verification is attempted at the same time, the verification performance will be significantly impaired. Further, if the collimator lens 4 and the objective lens 7 are made of a combination of a plurality of glass lenses so that there is no chromatic aberration, or if these lenses and a diffraction grating are combined, it becomes difficult to secure the optical performance, and the optical system becomes difficult. Becomes complicated, or the weight of the movable part becomes excessive, making high-speed access difficult, and the optical system becomes expensive.

In view of the problems of the prior art as described above, the present invention is provided with a light source having two light emitting points where the wavelength of the emitted light changes depending on the output, and is simple and has chromatic aberration. It is an object of the present invention to provide a two-beam information recording / reproducing apparatus capable of satisfactorily simultaneously performing erasing / recording / verifying or recording / verifying even if an optical head is constructed by using an inexpensive optical element. .

Still another object of the present invention is to perform good erasing / recording / verifying or recording / verifying at the same time while enabling high speed access without excessively increasing the weight of the movable portion of the optical head. It is to provide a possible two-beam information recording / reproducing apparatus.

[0011]

According to the present invention, in order to achieve the above object, a light source having first and second light emitting points for emitting first and second light beams, respectively, and A two-beam optical head including means for forming the first and second light spots on the surface of the information recording medium by passing the first and second light beams through substantially the same optical path, respectively. The light spot precedes the second light spot in the scanning on the information recording medium, and the outputs of the first and second light emitting points can be controlled independently, so that the information recording / reproducing can be performed on the information recording medium. In a two-beam information recording / reproducing apparatus for performing the information, the alignment direction of the first light emitting point and the second light emitting point is tilted with respect to a plane perpendicular to the optical axis of the optical system of the two-beam optical head. 2 Bee at the time of recording While compensating for the shift of the focusing position of the first and second light spots in the optical axis direction based on the chromatic aberration of the optical system of the optical head, the light is adjusted so that the first spot is focused during information recording. A two-beam optical information recording / reproducing apparatus is provided which controls a spot forming means and controls the light spot forming means so that the second spot is focused during information reproduction. It

In one aspect of the present invention, the control of the spot forming means selects the first point of the focus error detection signal of the first light spot as a control point at the time of recording the information, and at the time of reproducing the information. It is performed by selecting a second point different from the first point of the focus error detection signal of the first spot as a control point.

In one aspect of the invention, the light source is a semiconductor laser, especially a monolithic semiconductor laser.

In one aspect of the present invention, at the time of information recording, recording is performed by the first light spot, a focus error detection signal is obtained, and verification is performed by the second light spot. A focus error detection signal is obtained from the first light spot, and an information reproduction signal is obtained from the second light spot.

In one aspect of the present invention, the address information of the information recording medium is reproduced by the first light spot at the time of information recording, and the address information of the information recording medium is reproduced by the second light spot at the time of information reproduction. Play the information.

In one aspect of the present invention, the pre-format information of the information recording medium is reproduced by the first optical spot at the time of recording information, and the pre-format information of the information recording medium is reproduced by the second optical spot at the time of reproducing information. Play the preformatted information.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the construction of an optical head in an embodiment of a two-beam information recording / reproducing apparatus according to the present invention.

In FIG. 1, a monolithic semiconductor laser 1 has light emitting points 2 and 3. These two light emitting points are arranged so as to be inclined at a predetermined angle θ with respect to a plane orthogonal to the optical path O of the outward optical system whose arrangement direction is indicated by a chain line. Other configurations are similar to those in FIGS. 6 and 7.

That is, the two light beams emitted from the respective light emitting points 2 and 3 are made into substantially parallel light beams by the collimator lens 4, transmitted through the beam splitter 5 with a beam shaping section, and reflected by the mirror 6. The two beams reflected by the mirror 6 are recorded on the predetermined track 9 of the magneto-optical disk 8 by the objective lens 7 so as to have a recording spot 10 and a reproducing spot 1.
Narrowed down to 1. The spot 10 corresponds to the light emitting point 3, and the spot 11 corresponds to the light emitting point 2. Recording and reproduction can be performed simultaneously by these two spots.

The reflected beams of the two spots 10 and 11 are again made into a substantially parallel luminous flux by the objective lens 7, reflected by the mirror 6, and this time, the beam splitter 5 with a beam shaping section.
And is incident on the beam splitter 12. The beam transmitted through the beam splitter 12 has a convex lens 13,
It is guided to a servo error signal detection system including a cylindrical lens 14 and a servo sensor 15. On the other hand, the beam reflected by the beam splitter 12 is the birefringent crystal 1
6, the convex lens 17 and the RF sensor 18 lead to an information signal detection system.

The output of the servo sensor 15 is the control means 2
Input to 0. The focusing actuator 21 is controlled by the control means. The focusing actuator controls the position of the objective lens 7 in the optical axis direction, thereby controlling the focal positions of the spots 10 and 11.

Although not shown in FIG. 1, an external magnetic circuit for applying a magnetic field to a predetermined recording position of the magneto-optical disk 8 is provided as in the apparatus of FIGS. 6 and 7. There is.

Here, of the two spots 10 and 11, the spot 10 is ahead of the spot 11 relative to the rotating magneto-optical disk 8 (that is, first at a specific position on the track 9). Scanning with spot 10 is performed and then immediately scanning with spot 11). When recording data, light emission point 3 is spot 1
0 emits light so as to have recording power, and the light emitting point 2 emits light so that the spot 11 has reproducing power. At the same time, a magnetic field modulated with data information is applied by an external magnetic circuit. At this time, a so-called servo signal (focus error indication output signal) is obtained from the reflected light of the spot 10 and the spot 1
An information reproduction signal for verifying the recording made at the spot 10 is obtained from the reflected light of 1. As a result, the erasing of the old information, the recording of the new information, and the reproduction for verifying the new recorded information are simultaneously achieved. Further, during normal reproduction, both the light emitting points 2 and 3 emit light so that the spots 10 and 11 have reproduction power, and a servo signal is obtained from the reflected light of the spot 10 and an information reproduction signal is obtained from the reflected light of the spot 11. .

Here, the value of θ will be described in detail.

As described above, in the example of FIGS. 6 and 7, when the spot 10 has the recording power and the spot 11 has the reproducing power, the defocus of Δf occurs on the spot 11 side. Here, the distance between the two light emitting points 2 and 3 is d, the focal length of the collimator lens 4 is f _c , and its chromatic aberration is α [mm / n
m], the beam shaping ratio of the beam shaping unit with beam splitter 5 m, the focal length of the objective lens 7 f _o, the chromatic aberration β [mm / nm], the wavelength consisted spot 10 side is lambda to (λ + Δλ) Then, consider the defocus of the spot 11 at this time. At this time, if the defocus of the collimator lens 4 is Δd _c , Δd _c = α · Δλ, and the defocus of the objective lens is Δd _o , Δd _o = β · Δλ Overall, Δf = [{(f _{o ^{/ f c) 2 + (f}} o / mf c) 2} /
2] Δd _c + Δd _o .

Therefore, in the embodiment of the present invention, the monolithic semiconductor laser 1 is tilted by an angle θ with respect to a plane perpendicular to the optical axis O of the optical system as shown in FIG. 1, whereby Δd _c = α · Δλ−d · sin θ, and Δf = [{(f _o / f _c ) ² + (f _o / mf _c ) ² } /
2] (α · Δλ−d · sin θ) + β · Δλ. Therefore, θ = arcsin {α · Δλ / d + (2 / Ad) β · Δ
λ} where A = {(f _o / f _c ) ² + (f _o / mf _c ).
By setting ² }, Δf = 0 is realized.

In this embodiment, the numerical values of the optical system are as follows. That is, d = 0.1 mm, f _c = 8 [mm], α =
0.0003 [mm / nm], m = 2, f o = 4 [m
m], β = 0.0001 [mm / nm], Δλ = 3 [n
m]. Therefore, θ = 1.6 [degrees], and the monolithic semiconductor laser 1 is inclined by this angle.

As a result, the recording spot 10 at the time of recording
At the same time, the quality of the verification spot 11 is secured.

By the way, when the quality of the recording spot 10 and the verifying spot 11 at the time of recording is simultaneously secured as described above, two light emitting points 2 are provided at the time of normal reproduction.
Since 3 has almost the same output, approximately Δλ = 0, and if no measures are taken, the spot 11 is focused and the spot 11 is reversed by the amount corrected by tilting the monolithic semiconductor laser 1 by the angle θ. This results in defocusing, which deteriorates the information reproduction performance of the spot 11. As defocus amount, Δf '= - d · sinθ [{(f o / f c) 2 + (f o
/ A mf _c) ^2} / ^2] extent.

Therefore, in the embodiment of the present invention, the spot 10 is used.
In the focus position control using, as shown in FIGS. 2 and 3, the first control point AFofs1 is set so that the spot 10 is focused during information recording (in this case, the spot 11 is also focused as described above). Yes), spot 1 when reproducing information
The second control point AFofs2 is set so that 1 is in focus. Note that FIG. 2 shows a case where the focus error instruction output is 0 in AFofs1 and the optical system is ideally adjusted, and FIG. 3 shows AFofs1.
Shows the case where the focus error instruction output is not 0 and the adjustment of the optical system is not ideal. In any case, the relative defocus amount between the control points AFofs1 and AFofs2 is Δf ′.
The operation of the embodiment of the present invention will be described with reference to FIGS.

FIG. 4 shows the normal reproduction. At this time, there is almost no wavelength difference between the beams emitted from the two light emitting points 2 and 3, and relative defocus between the spots 10 and 11 occurs due to the tilt of the semiconductor laser at the angle θ with respect to the optical axis O. . Therefore, the position of the objective lens 7 is controlled so that the focus error instruction output obtained from the output of the servo sensor 15 becomes AFofs2. Then, the spot 10 is defocused by Δf ′ and the spot 11 is in focus.

FIG. 5 shows recording. At this time, the wavelength difference between the beams emitted from the two light emitting points 2 and 3 is Δλ,
As described above, the relative defocus between the spots 10 and 11 disappears (Δf = 0). Therefore, the servo sensor 15
The position of the objective lens 7 is controlled so that the focus error indication output obtained from the output of 1 is AFofs1. Then, the spot 10 is focused and the spot 11 is also focused.

In the embodiment of the present invention, the address information on the surface of the information recording medium is reproduced by the spot 10 during recording, and the address information on the surface of the information recording medium is reproduced by the spot 11 during normal reproduction. This advantage is that address information, like user data information, requires high-quality spot reproduction.Therefore, during recording or normal reproduction, defocusing occurs due to the output dependence of the emission wavelength of the semiconductor laser, that is, Δλ. It is possible to avoid the address information reproduction at a spot that is lost and to reproduce the address information at a high-quality spot that is always in focus. The address information is pre-formatted as a pattern of light reflectance and does not change even when spot irradiation with the recording power is performed.

As described above, the spot 10 is recorded at the time of recording.
The recording spot quality and the information reproduction performance of the spot 11 and the information reproduction performance of the spot 11 are ensured, while the information reproduction performance of the spot 11 is ensured during normal reproduction.

The present invention is not limited to the above embodiment, but can be applied to, for example, a phase change type optical disk device or an optical card device.

[0037]

As described above, according to the two-beam information recording / reproducing apparatus of the present invention, the direction of arrangement of the first light emitting point and the second light emitting point is determined by the optical axis of the optical system of the two-beam optical head. By tilting with respect to a surface perpendicular to the optical axis of the optical system of the two-beam optical head at the time of information recording, and compensating for the deviation of the in-focus position of the first and second light spots in the optical axis direction. At the time of reproducing the information and at the time of reproducing the information, respectively.
Since the spot forming means is controlled so that the spot of No. 1 is focused, the recording spot quality and the information reproducing performance of the first spot are ensured and the information reproducing performance of the second spot is ensured at the time of recording. During the information reproduction, the information reproduction performance of the second spot can be ensured.

Further, according to the present invention, the optical head is provided with a light source having two light emitting points where the wavelength of the emitted light changes depending on the output and using a simple and inexpensive optical element having chromatic aberration. Even with the above configuration, erasing / recording / verifying or recording / verifying can be favorably performed simultaneously.

Furthermore, according to the present invention, erasure / recording / verification or recording / recording / recording / recording / recording / recording / recording / recording / recording / recording / recording / recording / recording / recording
It becomes possible to perform the verification at the same time favorably.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical head in an embodiment of a two-beam information recording / reproducing apparatus according to the present invention.

FIG. 2 is a diagram showing control points of focusing control in the two-beam information recording / reproducing apparatus of FIG.

FIG. 3 is a diagram showing control points of focusing control in the two-beam information recording / reproducing apparatus of FIG.

4 is a diagram showing a focused state during normal reproduction in the two-beam information recording / reproducing apparatus of FIG.

5 is a diagram showing a focused state at the time of recording in the two-beam information recording / reproducing apparatus of FIG.

FIG. 6 is a schematic plan view showing an example of a conventional multi-beam optical head.

FIG. 7 is a schematic front view of FIG.

8 is a diagram showing a focused state in the multi-beam optical head shown in FIGS. 6 and 7. FIG.

[Explanation of symbols]

 1 Monolithic Semiconductor Laser 2, 3 Light Emitting Point 4 Collimating Lens 5 Beam Splitter with Beam Shaping Section 7 Objective Lens 8 Magneto-Optical Disk 9 Tracks 10, 11 Light Spot 12 Beam Splitter 13 Convex Lens 14 Cylindrical Lens 15 Servo Sensor 16 Birefringent Crystal 17 Convex lens 18 RF sensor O Optical system optical axis AFofs1, AFofs2 Control points

Claims (7)

[Claims] 1. An information recording medium in which a light source having first and second light emitting points for respectively emitting a first and a second light beam and the first and the second light beam pass through substantially the same optical path. A two-beam optical head including means for forming first and second light spots on the surface, respectively, wherein the first light spot precedes the second light spot in scanning the information recording medium. In the two-beam information recording / reproducing apparatus for recording / reproducing information on / from the information recording medium, the outputs of the first and second light emitting points can be controlled independently. The alignment directions of the two light emitting points are tilted with respect to a plane perpendicular to the optical axis of the optical system of the two-beam optical head, and the first and the second based on the chromatic aberration of the optical system of the two-beam optical head at the time of information recording In front of 2 light spots Thereby compensating for the deviation of the optical axis focus position information of the first light spot by controlling the spot forming means so as to focus at the time of recording, at the time of information reproduction and the second
The two-beam information recording / reproducing apparatus is characterized in that the spot forming means is controlled so that the light spot of (3) is focused. 2. The control of the spot forming means selects a first point of a focus error detection signal of the first light spot as a control point at the time of recording the information, and selects a first point of the first spot at the time of reproducing the information. The two-beam information recording / reproducing apparatus according to claim 1, wherein the two-beam information recording / reproducing apparatus is performed by selecting a second point different from the first point of the focus error detection signal as a control point. 3. The two-beam information recording / reproducing apparatus according to claim 1, wherein the light source is a semiconductor laser. 4. The two-beam information recording / reproducing apparatus according to claim 3, wherein the light source is a monolithic semiconductor laser. 5. When recording information, recording is performed with the first light spot, a focus error detection signal is obtained, and verification is performed with the second light spot, and when reproducing information, the first light spot is used. 5. The two-beam information recording / reproducing apparatus according to claim 1, wherein a focus error detection signal is obtained and an information reproducing signal is obtained by the second light spot. 6. The address information of the information recording medium is reproduced by the first light spot at the time of information recording, and the address information of the information recording medium is reproduced by the second light spot at the time of information reproduction. 1 to 5, characterized in that
2. The two-beam information recording / reproducing device according to any one of 1. 7. When recording information, the pre-format information of the information recording medium is reproduced by the first light spot,
7. The two-beam information recording / reproducing apparatus according to claim 1, wherein pre-format information of the information recording medium is reproduced by the second light spot when reproducing information.