JPH02218037A - Recording/reproducing system for magneto-optical disk device - Google Patents

Abstract

PURPOSE:To expand capacity by forming the bit string of a prescribed interval lying along the center of a track, and using the interval as a data zone, and obtaining a track error signal and a clock signal by using the change of the diffraction pattern of a light beam generated at every bit edge and by using the change of the reflection factor or transmission factor of light respectively. CONSTITUTION:A magneto-optical disk whose reproducing principle is Kerr effect is constituted as follows. Namely, the bit 10 string of the prescribed interval lying along the center of the track is formed on the surface of the disk 2, and the generated interval is used as the data zone. Besides, by using the change of the diffraction pattern of the light beam to be generated at the edge of each bit 10, the track error signal is generated by a track error detection circuit 50. Next, track counting is performed by using this error signal, and by using the change of the reflection factor or the transmission factor of the light beam to be generated at every bit, a reference clock signal is generated by using a PLL circuit 60. Thus, the detection of an error and the counting of the track become possible by only providing the bit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical disk device, and in particular to a recording and reproducing method for a magneto-optical disk device.

3. Detailed description of the invention [Summary] Concerning the recording and reproducing method of a magneto-optical disk device, the sample servo method is adopted, and the MCAV method [prior art] An optical system whose reproducing principle is the Kerr effect, which is the interaction of light and magnetism. Since magnetic disk drives perform non-contact reading or writing, a focus servo mechanism is required to accurately focus the optical spot of the laser beam onto the signal surface.
A radial servo mechanism is required to accurately track the light spot on the track.

Radial servo methods include continuous servo method and sample servo method. The continuous servo system conventionally used in optical discs directs the reflected light from the guide groove in the tangential direction (the direction in which the spot moves relative to the disc).
This method utilizes the fact that when light is received by a two-part photodetector that is divided into two parts parallel to each other, the amount of light received by the left and right sensors forming the detector differs depending on the positional relationship between the spot of the incident light and the guide groove. This method has the advantage of being able to use the MCAV method, which changes the clock frequency between the inner and outer circumferences of the disk and increases the storage capacity on the outer circumference. Due to the shaking, the reflected light does not hit the center of the two-split photodetector, which is a so-called beam shift.
There is a drawback that track offset occurs.

On the other hand, sample servo, which is the object of the present invention, is performed using a servo byte 1 consisting of a pair of wobbled pits 1, a unique distance section 12, and a clock pit 13 as shown in FIG. That is, the pair of wobbled pins 11 are each shifted from the center of the track by 1/2 track to the left and right, and a trunk error can be detected by determining the difference in the amount of reflected light between the two. Furthermore, the unique distance section 12 provided between the wobbled pit 11 and the clock pit 13 has an unrecorded length that does not appear in the data zone 14, and this unrecorded length is detected. By doing so, it is possible to recognize that the next pit is the clock pit 13. Therefore, a reference clock signal for generating a clock signal can be generated based on the signal from this clock pulse.

Further, the servo bits 1 are arranged radially on the disk surface, and the number of leading pits of the wobbled pit 11 is 16.
The position of the 3rd channel and the 4th channel of the first bite are alternately shifted every other track. Therefore, when moving the optical head for the purpose of track search, spot A
By determining whether the track intersects with the 3rd channel position or the 4th channel position, a track count signal for every 16 trunks can be obtained, making it possible to conduct a rough search. Furthermore, with this method, even during track search (even when the optical head is moving)
Since the clock signal is obtained (the light beam and the radially arranged clock pits 12 intersect at predetermined intervals), if the intersecting speed between the spot and the track slows down at the end of the coarse search as described above, the above-mentioned Track addresses can be read using the clock. Therefore, by combining the above coarse search and fine search,
Track counting becomes possible.

[Problem to be solved by the invention]

In the above conventional method, the servo byte 1 has the above three functions, and if these three functions are secured, the servo byte 1 is shortened as much as possible and the data zone 1
4 is more advantageous in terms of capacity. However, in the above system, the unique distance section 12 is required in order to confirm the clock pit 13, and the servo byte 1 is inevitably lengthened, resulting in a reduction in capacity. Also, if you try to use the above MCAV method, the clock ping)1
3 is no longer arranged radially as described above, it becomes impossible to keep a clock at all times, and it becomes impossible to detect track errors and count tracks. Therefore,
There is a drawback that the capacity increase due to MCAV cannot be measured. On the other hand, since the reflection from the wobbled pit 11 is used as described above, there is no track offset caused by beam shift as in the continuous servo system, and the system is excellent in reliability.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a recording and reproducing method in a magneto-optical disk device that employs a sample servo method and also enables large-capacity storage using the MCAV method. The purpose is to

(Means for Solving the Problems) The present invention is based on a magneto-optical disk device based on the Kerr effect as a reproduction principle, and employs the following means to achieve the above object. That is, as shown in FIG. 1, 10 rows of pits are formed at predetermined intervals along the center of the trunk on the disk surface 2, which is a storage medium.
The track error detection circuit 50 uses the change in the diffraction pattern of the light beam that occurs at the edge of each pit 10.
A track error signal is formed by the track error signal, and the track count is performed using the track error signal, and a reference clock signal is formed using the PLL circuit 60 by using the change in reflectance or transmittance of the light beam that occurs at each pit. I try to do that.

[For production]

In magneto-optical disks, unlike optical disks, there are no pits in the data zone 14, so the reflectance (transmittance) of light does not change.
, the reflectance (transmittance) changes only at the focal point 10, and this change is detected by the photodetector 41 and inputted to the PL, I circuit 60, thereby generating the reference clock signal. Can be formed. Also, pit 10
By utilizing the change in the diffraction pattern of the reflected (transmitted) beam at the 0 part, the sum signal of the photodetector 41 (four-division photodetector) that receives reflected light (transmitted light) (sum of outputs of each sensor making up the four-division photodetector: 3
Determining whether the phase of the difference signal between the RF multiplied signal and the diagonal sum shown in the figure (difference between the diagonal sums of each sensor: HT D signal in Fig. 3) is ahead or behind indicates the direction of deviation from the track. Signal, ie, track error (No. 3) can be detected.

Furthermore, if the interval between the pits 10 is made relatively small and the relative speed between the disk 2 and the optical head during access is appropriate, track counting using the error signal described above becomes possible.

〔Example〕

FIG. 2 shows one embodiment of an apparatus for carrying out the present invention. Pit 10 is provided at the center of each track T on the surface of the disk 2 at predetermined intervals, and laser light from a light source is converged onto the surface of the disk 20 via a beam splinter 31 and an objective lens 32 to form a spot. 20.

The reflected light from the disk 2 is sent to the beam splitter (PB
S) 31 separates the light from the incident light and enters a 1/2 wavelength plate 33, where the plane of polarization is tilted by 45 degrees and then enters a beam splitter (PBS) 34. Since the beam splinter 34 has different proportions of transmitted light and reflected light depending on the polarization angle of the incident light, a data signal can be obtained by taking the difference between the two. That is, both the transmitted light and the reflected light are incident on the 4-split photodetectors 41a and 41b, respectively, and the outputs of the 4-split photodetectors 41a and 41b are input to adders 42a and 42b. Here, each photodetector 41a, 41. Each sensor aI constituting b
+ bl + cl + dI and “X +
bl+C! , dt is obtained, and the subtracter 43 calculates the difference between the two, and the regenerator 4
4 and output as a data signal.

Next, when the spot 20 intersects the pit 10, each element a of the four-part photodetector 41a.

Total sum signal of signals from bl + CI * dI [
Hereinafter referred to as RF multiplied signal: RF=al +, t), +c1
+d, ) and the diagonal sum difference signal [hereinafter referred to as HTD signal:
HTc+= (at +c, ) −(bl +d
, , ) )) is shown in Figure 3. That is, if the spot 20 is shifted to the right in the tangential direction with respect to the pit 10 as shown in FIG. If the spot 20 is shifted to the left in the tangential direction with respect to the pit 10 as shown in Figure 3 (C1), the phase of the RF multiplied signal and the HTD signal will be delayed. Te spot 20
When the positions of the RF multiplied signals coincide with each other, the RF multiplied signal is always zero as shown in FIG. 3('b).

This phenomenon is caused by the diffraction of the reflected beam by the edges of the pits 10, and by utilizing this phenomenon, it is possible to eliminate tracking errors by determining whether the HTD signal is leading or lagging behind the RF multiplied signal. This means that it can be detected. Therefore, the output of the adder 42a, that is, R
The HTD signal output from the F-fold signal adder/subtractor 45 is input to a track error detection circuit 50, which is a phase detector, to obtain a track error signal. For example, a hetero gain method is used as the phase detection method.

The track error signal obtained from the track error detection circuit 50 can also be used for track counting. That is, when the head moves in the radial direction, each track T
If the pit IO provided in , , and the spot 20 almost certainly intersect, the track error signal becomes the track count signal as it is. Further, at this time, even if a count error occurs, the head 1 moves slowly at the final stage of the track search, so it becomes possible to read the addresses written in each track and make fine adjustments.

Next, the output of the adder 42a which takes all the phases of the 4-split photodetector 41a is also input to the differentiator 46, which detects the change in the amount of light when the pit 10 and the spot 20 intersect. The output of the circuit 46 is input to a PLL circuit 60, and the output of the PLL circuit 60 is used as a reference clock. Here, the input to the differentiator 46 may be a value obtained by further adding the outputs of the adders 42a and 42b.

〔Effect of the invention〕

As explained above, in the present invention, track errors can be detected, track counted, and clock signals can be generated simply by providing pits at predetermined intervals on the surface of the disk, and moreover, no track offset occurs when detecting a track error. Therefore, not only the data zone can be enlarged, but also the capacity can be increased by converting to MCAV.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle of this invention, Fig. 2 is a configuration diagram showing an embodiment of a device implementing the invention, and Fig. 3 is a diagram showing changes in the relative positions of spots and pits and the RF multiplied signal HTD signal. A diagram showing the relationship, FIG. 4, is a schematic diagram of a conventional sampling method. In the figure, 2...disc, 10...pit, 14...data zone.

Claims (1)

[Scope of Claims] [1] In a magneto-optical disk device, a row of pits (10) are formed at predetermined intervals along the track center on the surface of a disk (2) which is a storage medium, and the above-mentioned intervals are defined as a data zone (14). ), a change in the diffraction pattern of the light beam that occurs at the edge of each pit (10) is used to form a track error signal, and the track error signal is used to perform track counting.
10) A recording/reproducing method for a magneto-optical disk device, characterized in that a clock signal is formed using the change in reflectance or transmittance of a light beam.