JPH0363949A - Information recording and reproducing device - Google Patents

Abstract

PURPOSE:To reproduce data at the same timing even in the inner circumference and outer circumference tracks, for which linear velocity is made different, of a disk and to obtain data reproducing signals at the same level with high reliability by changing modulation timing corresponding to the linear velocity at the time of recording. CONSTITUTION:A means 16 is provided to control the modulation timing of a recorded signal to a desired value corresponding to the linear velocity of a recording medium 1. The effective linear velocity of the recoding medium 1 is known from the radial position and track number, etc., of the recording medium 1 and the modulation timing of the recorded signal is controlled to be matched with the linear velocity. For example, a delay circuit 17, etc., is provided and recording is executed by the delayed recording signal. Then, pit shifts S1 and S2 are corrected. By this correction, the shift amount of the recorded pit can be fixed even in any track of the disk 1. Thus, the data can be reproduced at the same timing even in the inner circumference and outer circumference tracks, for which the linear velocity is made different, of the disk and the data reproducing signal can be obtained at the same level with high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an information recording and reproducing apparatus that irradiates a recording medium such as a magneto-optical disk with a laser to form pits and record data.

[Prior Art] Magneto-optical disks have been known as large-capacity recording media on which data can be rewritten. There are two methods for recording on this magneto-optical disk: an optical modulation method in which the irradiation laser power is switched according to the recording signal, and a magnetic field modulation method in which the irradiation laser power is constant and the direction of the externally applied magnetic field is reversed in accordance with the recording signal. be. In both of these methods, recording pits are usually formed by heating the magnetic layer of the medium to a temperature higher than the Curie temperature by laser irradiation.

The timing of modulating the laser power or the applied magnetic field with the recording signal is controlled by, for example, detecting a clock pit provided in advance on the magneto-optical disk and creating a clock signal using this pit position as a reference. Furthermore, the timing of data reproduction is also controlled by a similar clock signal.

[Problems to be Solved by the Invention] Incidentally, in the information recording apparatus that forms pits by laser irradiation as described above, the shape of the formed pits also differs depending on the difference in recording conditions. For example, the pit shape depends on the linear velocity of the disk during laser irradiation.

Next, referring to FIG. 5, the pit formation process when recording is performed by magnetic field modulation at different linear velocities will be described. In Figure 5, L+ and L2 have the centers of the laser beams C, C*, respectively.
This figure shows the region where the magnetic layer of the medium rises above the Curie temperature and a domain wall is formed. The beam is moving in the direction of arrow d, Ll is slow and almost circular, and L2
At high speed, the beam becomes egg-shaped, extending toward the road side from the direction of beam travel. However, the laser power is increased in L2 so that the pit widths are the same. The pit has a positive magnetic field (+
) side, when the beam moves in the direction of arrow d on tracks T+ and Tx and the applied magnetic field H is reversed to the + side, pits P1. Pg is formed. At this time, the applied magnetic field reversal timing and the shift amount SS2 of the edges of the pits PI and P2 differ due to the difference in the domain wall forming regions, Lt (Sr<S-).

In an information recording device using the CAV (constant disc rotational speed) method, the linear velocity at the inner circumference of the disk is different from that at the outer circumference. Since the amount of deviation of the recorded pits on the periphery and the outer periphery is different, if the reproduction timing is the same on the inner and outer peripheries, the quality of the reproduced signal will differ depending on the radial position of the disk. For example, if the reproduction timing is adjusted to the inner circumference, there is a risk that reproduction errors will increase in the outer circumference. This matter is MC
The influence is thought to be even greater in AV (constant rotation speed, constant linear density) systems. Also, like mark length recording, data can be set to “1” or “0” depending on the edge position of the pit.
”, the difference in the amount of edge deviation becomes a big problem.

An object of the present invention is to provide an information recording and reproducing device that can reproduce data at the same timing even on tracks on the inner and outer circumferences of a disk having different linear velocities, and can obtain data reproduction signals with the same level of reliability. It is in.

[Means for Solving the Problems] In order to achieve the above object, the information recording/reproducing apparatus of the present invention records data by forming pits on a recording medium by laser irradiation, and the recording medium is synchronously In an information recording/reproducing device in which pits are recorded periodically in advance and the modulation timing of the recording signal and the data reproduction timing are created based on the synchronous pit position, the modulation timing of the recording signal is adjusted according to the linear velocity of the recording medium. The present invention is characterized by providing means for controlling the value to a desired value.

[Operation] In the present invention, the actual linear velocity of the recording medium is known from the radial position of the recording medium, the track number, etc., and the modulation timing of the recording signal is controlled in accordance with the linear velocity. For example, a delay circuit or the like is newly provided, recording is performed using a delayed recording signal, and pit shift is corrected. By this correction, the amount of shift of the recorded pits can be made constant for any track on the disk.

[Example] Hereinafter, the information recording/reproducing apparatus of the present invention will be described in detail based on a specific example.

As an embodiment of the present invention, a magnetic field modulation type magneto-optical disk device will be described. First, Figure 3 shows the format of the disc. For example, the magneto-optical disk 1 has a diameter of 13c.
It has a capacity of 200 Mbytes or more on one side. The radius of the innermost track is 35mm, and the radius of the outermost track is 60mm.If the rotation speed is 300 Orpm, the linear velocity is 10.99m/s at the innermost track and 18m/s at the outermost track.
．． It becomes 84m/s. In the figure, a track 100 consists of a servo area 101 and a data area 102.

FIG. 4 shows an enlarged view of the servo area 101 and the data area 102. Pit Pwl, P of servo area 101
C and Pw2 are formed in advance on the disk, and a clock pit Pc is located at the center of the track, and a clock signal C during recording/reproduction is generated by detecting this pit.

Further, the wobble pits P wl and P w2 are shifted in the vertical direction of the track, and a tracking error signal is generated based on the amount of shift to perform AT (auto tracking) control.

In the data area 102, the magnetic field is modulated according to the recording data signal to form pits Pdl, Pd2, . . . . Pit P wl, P w2. The diameter of P c is 0.5~
The length of the servo area 101 is approximately 1.0 μm.
5-301. About Lm, recording data pit P di.

Pd2. The width of . . . is about 1.0 μm, and 8 bytes of information can be recorded. Each track has 1376 servo areas 101 and 1376 data areas.

Next, FIG. 1 shows a magneto-optical disk recording and reproducing apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 indicates a magneto-optical disk as a recording medium, and reference numeral 2 indicates a magnetic film on which information is recorded. This magneto-optical disk 1 is rotationally driven by a motor 3.

Information is recorded or reproduced on this magneto-optical disk 1 by an optical pickup 4. The optical pickup 4 has a built-in semiconductor laser 5 as a light source. The light emitted from this semiconductor laser 5 passes through a collimating lens 6 and a beam splitter 7, and then passes through an objective lens 8 onto a magneto-optical disk.
The light is focused on the top. On the other hand, the light reflected by the magneto-optical disk 1 passes through the objective lens 8 again, is separated from the incident light by the beam splitter 7, and passes through the sensor lens 9 to the photodetector 10.
The light is received by Then, based on the output of this photodetector 10, a focus error signal and a tracking error signal are detected by an AT and AF circuit 11. These error signals are input to the actuator 12 and drive the objective lens 8, thereby performing auto-tracking and auto-focusing.

In this optical pickup unit 4, laser light of a constant intensity continuously emitted by a semiconductor laser 5 is locally irradiated onto the magnetic film 2 of the magneto-optical disk 1, and the temperature of the magnetic film 2 in the irradiated portion is changed to Curie. It is configured to raise the temperature above the point.

Further, reference numeral 13 indicates an electromagnet for applying a magnetic field to the magnetic film 2 of the magneto-optical disk 1, and in this example, this electromagnet 1
3 is constructed so that it can be moved in the radial direction of the magneto-optical disk 1 in conjunction with the optical pickup 4 with the magneto-optical disk 1 interposed therebetween.

Further, 14 indicates a magnetic field modulation circuit. The direction of the current flowing through the coil 13B wound around the electromagnet 13 is reversed in accordance with the recording signal input to this magnetic field modulation circuit.

For example, when the signal level of the recording signal is high level °゛1'', the current flowing in the direction shown by the arrow 13B is applied to the coil 13B.
When the signal level is low level °゛0°°, a current flowing in the direction shown by the arrow ■ is supplied to the coil 13B, and in the electromagnet 13, the signal level of the recording signal is high level °゛l''. At this time, a magnetic field as shown by the arrow HA is generated, and the signal level of the recording signal is low level "O".
The structure is such that a magnetic field as shown by the arrow is generated when ゛′.

Reference numeral 15 denotes a clock signal generation circuit that generates a clock signal C for data recording/re-maintaining based on a reproduced signal of the clock pit Pc from the photodetector 10. Further, 17 is a delay circuit that delays the recording signal, and 16 is a control circuit to which a signal related to linear velocity is input and determines the amount of delay of the delay circuit 17 in accordance with the signal. In a normal recording device, when recording data, the magnetic field modulation circuit 14 only determines the timing of magnetic field modulation based on the clock signal C from the clock signal generation circuit 15, but in this embodiment, this timing is controlled. The recording signal is delayed by a delay circuit 17 in accordance with a signal related to linear velocity inputted to the circuit 16 (for example, the distance of the recording track from the center of the disk), and is changed by changing it into a magnetic field modulation signal.

The amount of timing deviation is shown in FIG. The recording pit when the linear velocity is small is Pl, and the recording pit when it is high is P2.
It is. Letting the amount of deviation between the pit edge and the applied magnetic field reversal be S, , S, respectively, the timing of the magnetic field modulation is set to be shifted by Sl+S2 from the rising edge of the clock signal C by the delay circuit 17.

The amount of deviation S, , S varies depending on the signal related to the linear velocity such as the radial distance of the track, but its value can be uniquely determined.

[Other Embodiments] In the above embodiments, a magneto-optical disk device using a magnetic field modulation method was described, but a magneto-optical disk device using an optical modulation recording method can similarly delay an optical modulation signal. Accordingly, the present invention can be realized.

Furthermore, the present invention is applicable not only to magneto-optical disks but also to general optical disk devices in which data is recorded by forming pits by irradiating laser beams, in which the pit shape depends on the linear velocity and the amount of pit shift varies depending on the linear velocity. It is clear that the invention can be implemented in any device in general.

[Effects of the Invention] As explained above, according to the information recording and reproducing apparatus of the present invention, by changing the modulation timing during recording according to the linear velocity, the difference in pit shift amount due to the difference in linear velocity can be eliminated, Data can be reproduced at the same timing even on tracks on the inner and outer peripheries of the disk having different linear velocities, and highly reliable data reproduction signals of the same level can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing a magneto-optical disk device embodying the present invention. FIG. 2 is a diagram showing magnetic field modulation timing showing an embodiment of the present invention. FIGS. 3 and 4 are diagrams showing formats of magneto-optical disks that can be used with the apparatus shown in FIG. 1. FIG. 5 is an enlarged view of a disk pit showing a conventional example. 1: Magneto-optical disk, 2: Magnetic film, 3: Motor, 4: Optical pickup, 5: Semiconductor laser, 6: Collimator lens, 7: Beam splitter, 8: Objective lens, 9: Sensor lens, 10: Photodetector , 11: AT, AP circuit, 12: actuator, 13: electromagnet, 13B: coil, 14: magnetic field modulation circuit, 15: clock generation circuit, 16: control circuit, 17: delay circuit. Figure 2

Claims (2)

[Claims] (1) Data is recorded by forming pits on a recording medium by laser irradiation, and synchronous pits are periodically recorded in advance on the recording medium, and the modulation timing of the recording signal is based on the synchronous pit position. and an information recording and reproducing apparatus for creating data reproduction timing, characterized in that the information recording and reproducing apparatus is provided with means for controlling the modulation timing of the recording signal to a desired value according to the linear velocity of the recording medium. (2) The information recording and reproducing apparatus according to claim 1, characterized in that a magnetic field modulation method is adopted in which recording is performed by reversing the magnetic field applied to the recording medium according to the recording signal.