JP2685440B2 - Magneto-optical disk - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk, and more particularly, to an optical magnetic disk in which a rotation speed reference, a tracking reference, and a clock reference of a digital signal to be recorded are obtained. It is about magnetic disks. [Prior Art] The information track of a magneto-optical disk for recording / reproducing information using a laser beam has a narrow interval of about 1 μm to 3 μm,
In order to accurately trace information tracks with laser light, it is common to provide concentric or spiral grooves called pregroups on the disk substrate. Since the number of information tracks of the magneto-optical disk reaches tens of thousands, some kind of address information is recorded in each information track or each sector into which the information track is further divided in order to detect (search) the desired information track. It is desirable to do. 5 (a) and 5 (b) show, for example, the IEEE spectrum 19
FIG. 2 is a partially enlarged cross-sectional view and a partially enlarged plan view showing a conventional recordable optical disk (magneto-optical disk) shown in pages 26 to 33 of the August 1979 issue, where 1 is glass, A disk substrate made of a transparent material such as plastic and formed in a disk shape, 2 is a recording film composed of a magnetic film having perpendicular magnetic anisotropy and a dielectric protective film, 3 is an information recording portion, and has a depth λ. A guide groove 31 of / 8 (λ is the wavelength of the recording / reproducing laser beam) is formed in advance. Reference numeral 4 denotes an address portion, and an address information pit 41 having a depth λ / 4 is formed in advance similarly to the guide groove 31 of the information recording portion 3. Next, the recording / reproducing operation using the optical disk will be described. The light beam traces the guide groove 31 of the information recording section 3 and the address information pit 41 of the address section 4 on the extension of the guide groove 31. The method used for this tracking is the same as the method used for the tracking of a laser video disk or a compact disk, and is well known, so description thereof will be omitted. The address information unit 41 is formed so that it can be self-clocked, and clock reproduction and address information reading are performed when the optical spot is running on the address unit 4 of the optical disk. The rotation speed of the optical disk is controlled by phase comparison between the rotation reference frequency and the reproduced clock (reproduction clock), and the writing of information (data) to be recorded in the information recording unit 3 of the magneto-optical disk is also synchronized with the reproduction clock. It will be done. [Problems to be Solved by the Invention] Since the conventional magneto-optical disk is constructed as described above, the number of blocks per side when used as an optical disk is N, and the number of blocks of the information recording unit 3 per block is N. When the number of information bits is K ₁ and the number of address bits of the address section 4 is K ₂ , the total information capacity M can be expressed as M = N × (K ₁ + K ₂ ). As described above, the rotation of the optical disk is changed to the address information
When synchronized with the playback clock of 41, the response characteristic of the rotary servo is greatly influenced by the appearance frequency of the address section 4, and the frequency of appearance of the address section 4 is increased in order to make the response of the rotary servo quick and stable. It is necessary. That is, the number of blocks must be increased by N, but since the total information capacity M is almost constant as long as the disk size does not change, the sum (K ₁ + K ₂ ) of both bit numbers K ₁ and K ₂ is the block number N. It decreases in inverse proportion to. However, as the number of blocks N increases, the number of address bits K ₂ representing each block increases in proportion to log N, and thus the number of information bits K ₁ decreases and the utilization efficiency of the optical disk (N × K ₁ / M ) Decreases. That is, since improving the rotation accuracy of the optical disk and improving the usage efficiency of the optical disk are contradictory factors, there is a problem that both the rotation accuracy and the usage efficiency cannot be improved at the same time. . On the contrary, when the number of blocks N is reduced, an error occurs between the writing clock to the information recording unit 3 and the actual rotation because the reproduction clock of the address unit 4 is used.
Since it becomes necessary to provide the information bit number K ₁ with a margin for absorbing this error, the number of bits actually recordable with respect to the physical length of the information recording section 3 becomes small, and the magneto-optical disk There was a problem in that the utilization efficiency would still decrease. When it is used as a magneto-optical disk, as described above, the reproduction clock is obtained by reading the address information pit 41 provided only in the address section 4, so that sufficient rotation accuracy can be obtained. However, there is a problem in that a separate clock generator must be provided. The present invention has been made to solve the above problems, and an object of the present invention is to obtain a magneto-optical disk capable of improving the rotation accuracy by a reproduction clock obtained by reading its own guide pit. [Means for Solving Problems] The magneto-optical disk according to the present invention is
The guide pits are arranged at a cycle that is an integral multiple or a fraction of the cycle of the clock frequency of the digital signal to be recorded and that is short enough to be recognized as a continuous groove with respect to the cycle of the tracking response frequency. It is provided. [Operation] In the magneto-optical disk according to the present invention, by reading the guide pit, it is possible to obtain the reproduction clock used as the rotation speed reference, the tracking reference, and the clock reference of the digital signal to be recorded. An embodiment of the present invention will be described below with reference to the drawings. 1 (a) and 1 (b) are a partially enlarged sectional view and a partially enlarged plan view of an information recording portion showing a magneto-optical disk according to an embodiment of the present invention, and the same portions as those in FIG. It is attached. In FIG. 1, reference numeral 32 denotes an uneven row for tracking. This uneven row 32 is provided by a guide pit 321 provided at a cycle of an integral multiple or an integer fraction of the clock frequency of the digital signal to be recorded. Is configured. Next, the operation will be described. The magneto-optical disk according to the present invention is a concavo-convex array of the information recording section 3.
By tracing the guide pit 321 that constitutes 32, clock reproduction and data reading are performed. Normally, the upper limit of the response frequency of the tracking servo is several KH
z, and the magneto-optical disk of the present invention has a guide pit 3
Since the period τ of 21 is sufficiently short with respect to the period of the response frequency of the tracking servo, the uneven array for tracking 32
Can be treated in the same way as the continuous guide groove 31 in the conventional example, and since the signal of the concave-convex row 32 always appears also in the rotation cycle, the response can be controlled by controlling the cycle τ to be constant. , Servo characteristics with excellent stability can be obtained. Even if a fluctuation of the clock that cannot be responded to by the rotation control system occurs due to eccentricity or the like, the position of the position where the data should be written is used by using the signal of the concave-convex row 32 as the clock reference for reading and writing the data. Misalignment does not occur. FIG. 2 is a schematic diagram showing the arrangement of the concavo-convex array 32 of the magneto-optical disk used at a constant angular velocity, and the concavo-convex array at the radius r ₁ .
The mechanical spacing l ₁ of the 32 guide pits 321 is the mechanical spacing l of the guide pits 321 of the uneven row 32 at the radius r ₂ (r ₂ > r ₁ ).
_It is shorter than ₂ and has a relation of l = r × θ (θ: constant). FIG. 3 is a schematic view showing the arrangement of the concavo-convex row 32 of the magneto-optical disk used at a constant linear velocity, and l ₁ = l ₂ regardless of the size of the radii r ₁ , r ₂ . 4 is a partially enlarged sectional view and a partially enlarged plan view showing the vicinity of the boundary between the information recording portion 3 and the address portion 4 of the magneto-optical disk according to another embodiment of the present invention. The same reference numerals are attached. In FIG. 4, reference numeral 21 is a magnetic film having perpendicular anisotropy that constitutes the recording film 2, 22 is a dielectric protective film that constitutes the recording film 2, and 42 is an address information bit provided in the address section 4. The address information pits 42 are formed by modulation so as not to impair the periodicity of the period τ of the concave-convex array 32 of the information recording unit 3. In the case of this embodiment, the address portion 4 is also provided with the address information pit 42 for clock reproduction, and the same effect as that of the embodiment of FIG. 1 can be obtained. Then, the reproduction of the data is detected by the rotation of the polarization plane of the reflected light (or the transmitted light), and the clock reproduction from the concavo-convex row 32 is reproduced as the intensity change of the reflected light (or the transmitted light). Separation can be easily performed, and the degree of freedom for both pits 321 and 42 is increased. Therefore, the depths of both pits 321 and 42 can be made the same, and master recording for making the disk substrate 1 becomes easy. Although an example of the structure of the recording film 2 is shown in FIG. 4 in the above-mentioned embodiment, the structure of the recording film 2 is not limited to the structure shown in FIG. 4 and may have another structure. . [Effects of the Invention] As described above, according to the present invention,
The guide pits are arranged at a cycle that is an integral multiple or a fraction of the cycle of the clock frequency of the digital signal to be recorded and that is short enough to be recognized as a continuous groove with respect to the cycle of the tracking response frequency. Since the reproducing clock is provided, the reproduction clock can be obtained by reading the guide pit, so that the rotation accuracy can be improved by using the reproduction clock. Then, it can be applied to a magneto-optical disk having a constant angular velocity and a constant linear velocity. Further, since the depths of the pits provided in the information recording portion and the address portion can be made the same, there is an effect that master recording for forming the disk substrate becomes easy. Further, when used as an optical disc, there is an effect that the utilization efficiency can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are a partially enlarged sectional view and a partially enlarged plan view of an information recording portion showing a magneto-optical disk according to an embodiment of the present invention, FIGS. FIGS. 4A and 4B are schematic views showing the arrangement of concavo-convex rows of magneto-optical disks for constant velocity and constant linear velocity, respectively, and FIGS. 4A and 4B show information recording on a magneto-optical disk according to another embodiment of the present invention. Enlarged cross-sectional view and partial enlarged plan view showing the vicinity of the boundary between the address section and the address section. FIGS. 5A and 5B are partial enlarged views showing the vicinity of the boundary between the information recording section and the address section of the conventional optical disk. It is a sectional view and a partially enlarged plan view. In the figure, 1 is a disk substrate, 2 is a recording film, 3 is an information recording part, 32 is a concave and convex array, 321 is a guide pit, 4 is an address part, and 42 is an address information pit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] In a magneto-optical disk having a recording film formed on a disk substrate, the disk substrate has a cycle of an integral multiple or a fraction of a clock frequency of a digital signal to be recorded and a cycle of a tracking response frequency. The magneto-optical disk is characterized in that guide pits are arranged at a short period so that the grooves are recognized as continuous grooves. 2. The magneto-optical disk according to claim 1, wherein the guide pits are arranged at an equal angle with respect to the center of rotation. 3. The magneto-optical disk according to claim 1, characterized in that the guide pits are arranged at equal lengths in the cylindrical direction. 4. Address information pits that are formed by dividing a continuous guide pit into a plurality of blocks by dividing it into a plurality of blocks, and that address information of an address portion provided at the head of the plurality of blocks is modulated so as not to impair the periodicity of the guide pits. The magneto-optical disk according to any one of claims 1 to 3, wherein the magneto-optical disk is formed by. 5. The magneto-optical disk according to claim 4, wherein the depth of the address information pit is the same as the depth of the guide pit.