JPH04102230A - Optical recording medium and recording and reproducing method using this medium - Google Patents

Abstract

PURPOSE:To improve a resolving power and to increase a recording density as well as to decrease the reading errors of recording by providing ruggedness on the surface of recording tracks at a prescribed period in the extension direction of recording tracks. CONSTITUTION:The spiral recording tracks 5 consisting of 1.0mum wide land are formed at 1.6mum pitch on both sides of 0.6 mum width grooves on the surface of a disk substrate made of polycarbonate having 86mm diameter and recording surfaces 10 and grooves 11 are alternately formed along the extension direction thereof. The recording surfaces 10 are formed by providing the grooves having 1.0mum depth and 0.2mum width at 1.0mum intervals in the scanning direction B of the recording tracks 5. The optical disk formed in such a manner is first heated and melted by using an Ar laser beam and is then slowly cooled, by which the entire surface of the recording layer is crystallized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the structure of an optical recording medium and a recording/reproducing method using the optical recording medium, and particularly relates to a technique for improving the recording density of an optical recording medium. It is something.

[Conventional technology]

Optical recording media such as optical disks have a recording density approximately 10 to 100 times that of conventional magnetic recording media and have a long lifespan, so they are considered promising as new recording media.

As shown in FIG. 13, the structure of the optical disc is that tracking grooves 1 are formed on the surface of a disc substrate 1 made of polycarbonate, etc.
A is formed in a spiral shape, and on top of this, a magnetic thin film is formed in the case of a magneto-optical method, and a thin film made of a material that can be reversibly changed between crystal and amorphous in the case of a phase change method is formed on the recording layer 2. form as. Although not shown in the figure, various types of protective films are usually formed above and below the recording layer. Tracking groove 1
The portion of the recording layer 2 formed directly above a is divided into a groove 3 and a land 4, and this group 3 area forms a recording track 5 shown in FIG.

This recording track 5 is normally irradiated with a laser beam from the back side of the substrate 1, and information is recorded at predetermined intervals along the recording track 5.

The irradiation position of the laser beam is adjusted by a tracking servo mechanism of the optical recording device, and its focus is adjusted by a focus servo mechanism.

By these adjusting means, the laser beam is narrowed down to the diffraction limit, and a recording mark 6 with a diameter of about 1 μm is formed on the recording track. Since the recording mark 6 has a magnetization direction or reflectance different from its surroundings, the presence or absence of the recording mark 6 can be read out as binary data by detecting the intensity of transmitted light or reflected light of a low-power laser beam.

In order to record and reproduce data accurately, it is necessary to match the point at which the value of the detection signal is taken out and the position of the recording mark on the recording track. For this reason, bit synchronization is usually performed on the recording track. In order to do this, a preamble section with a clock signal recorded thereon was provided, and a synchronization signal was taken in before recording and reproducing data.

[Problem to be solved by the invention]

However, the conventional optical recording medium described above has the following problems.

That is, the reason why the recording density of an optical recording medium is higher than that of a magnetic recording medium is that the recording mark 6 can be made to have an extremely small diameter of about 1 μm, as described above.
On the other hand, since this 1 μm is the limit for narrowing down the laser beam, it is technically difficult to obtain a recording density higher than this.

That is, when the interval between the recording marks 60 on the recording track 5 is shortened, as shown in FIG. 15, the peaks of the signal intensities obtained from each recording mark 6 overlap, increasing the probability of occurrence of a reading error.

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and its object is to improve the resolution of the detection signal by making the recording track 5 have a periodic structure, and to add periodic components to the detection signal itself that become synchronization signals. It is an object of the present invention to provide an optical recording medium in which the recording density is increased by shortening the interval between recording marks 6, and there are fewer recording reading errors, and an optical recording method using the same.

[Means to solve the problem]

In order to solve the above-mentioned problems, in an optical recording medium having a recording track on which information can be recorded or read by optical means, the means taken by the present invention is to This provides unevenness on the surface of the track.

The unevenness is composed of grooves, protrusions, and other steps on the recording surface. Here, the above-mentioned unevenness may be formed by forming a plurality of recording surfaces parallel to each other in the extending direction of the recording track and having different surface orientations or surface heights within a predetermined period. Furthermore, at least one of the plurality of recording surfaces may be a slope inclined in the direction of extension of the recording track.

The recording/reproducing method using these optical recording media involves scanning the recording track by irradiating laser light, etc., and detecting this in synchronization with periodic fluctuations in the intensity of the detected light obtained based on the unevenness on the recording track. The recorded content is extracted from the light intensity.

Furthermore, in synchronization with periodic fluctuations in the detected light intensity obtained based on the unevenness during scanning of the recording track, the characteristics of the light irradiated to the recording track, such as light intensity, spot diameter, etc., are adjusted,
Data is recorded or erased on the recording track.

In these recording and reproducing methods, the intensity of the focus error signal may be used as the detected light intensity.

[Effect]

According to this means, since unevenness is formed at a predetermined period in the extending direction of the recording track, when the recording track is scanned with the laser beam irradiated on the unevenness, the transmitted light or the transmitted light based on the irradiated light is Since the direction of the reflected light or its focal length changes, the detected light intensity also changes. As a result, the detection signal from the recording track becomes a data signal, which is the original recorded content, on which a periodic signal synchronized with the recorded bits is superimposed. Therefore, by recording data in accordance with the formation period of the unevenness on the recording trunk, the detection signal itself has a built-in synchronization signal for reading the contents of the data signal, thereby preventing the occurrence of reading errors. can do. Unlike the conventional bit synchronization using a preamble section, this synchronization method allows synchronization in real time, so it is possible to suppress the occurrence of synchronization errors and eliminates the need for the preamble section itself.

In addition, if the unevenness is composed of multiple recording planes with different surface orientations or surface heights, the irradiation light beam that matches one recording plane will be affected by the focal length and optical path direction with respect to the other recording planes. Since the two recording surfaces do not match, it is possible to eliminate contributions from other recording surfaces to the detection signal. Therefore, even if the interval between recording bits is made smaller than the spot diameter of the laser beam, the information from the area where the spot diameter spreads to areas other than the recording bits will hardly affect the detection signal. Even if the interval between recording bits is made smaller than the spot diameter of the irradiation light beam, the occurrence of reading errors can be suppressed, and as a result, the data recording density can be increased.

Furthermore, if at least one of the plurality of recording surfaces is a slope inclined in the direction of extension of the recording track, in order to perform recording and reproduction on this slope, it is necessary to match the irradiation light beam to the slope angle. However, since the effective recording area can be increased, the recording density can be further increased.

As a method for recording and reproducing data using the optical recording medium described above, the data signal can be reproduced in synchronization with the variation period of the detection signal based on the unevenness on the recording track, and the detection By changing the light intensity, spot diameter, etc. of the irradiated light flux in synchronization with the fluctuation cycle of the signal,
Data can be recorded or erased on the recording track.

In this method, by making the period of the unevenness on the recording track constant on the entire recording medium, it is possible to ensure high recording density and to always perform recording and reproduction in the same state. For example, conventionally, when trying to form recording bits with the same spacing on all recording tracks of an optical disc, it was necessary to change the disc rotation speed or recording/reproducing frequency in the radial direction of the optical disc, but with this method, Since the recording and reproducing frequency can be automatically adjusted in synchronization with the unevenness on the recording track, it is possible to eliminate or simplify the adjustment mechanism for the disk rotation speed and recording and reproducing frequency, and it is possible to improve the recording and reproducing frequency. It is possible to expect an improvement in accuracy.

〔Example〕

The present invention will now be described in detail with reference to the accompanying drawings.

<First Example> The first example of the optical recording medium is a spiral recording track consisting of 1.0 μm wide lands sandwiching 0.6 μm wide groups on the surface of a polycarbonate disk substrate with a diameter of 86 mm. 5 are formed at a pitch of 1.6 μm, and the recording surface 10 and grooves 1 are formed along the extending direction as shown in FIG.
1 are alternately formed. The recording surface 10 has a depth of 1 at intervals of 1.0 μm in the scanning direction B of the recording track 5.
It is formed by providing a groove with a width of 0.2 μm.

On this disk substrate are a protective layer made of ZnS with a thickness of 110 nm, a recording layer made of Get Sb and Te with a thickness of 30 nm, a protective layer made of ZnS with a thickness of 170 nm, and a cooling reflection layer of Af with a thickness of 1100 nm. Each of the layers was sequentially formed by sputtering.

The optical disc thus formed was first heated and melted using Ar laser light, and then slowly cooled to crystallize the entire surface of the recording layer. Here, the refractive index of the recording layer differs depending on whether it is in a crystalline state or an amorphous state, and depending on whether or not the crystallized recording layer is irradiated with a laser beam to make it amorphous, the reflection of that part of the optical disc is rate changes. Therefore, it becomes possible to record these crystalline states and amorphous states in correspondence with binary data.

The optical disc of this example has a disc rotation speed of 360 Or
The recording track 5 was scanned at pm to record binary serial data, and then a recording/reproduction test was conducted.

In this optical disc, as shown in FIGS. 2(a) to 2(d), the laser beam scans over the recording trunk 5 as the disc rotates, but the laser beam 12 scans the recording surface.
At the time when only the surface of 0a is irradiated, the recording surface 10
A reflected light beam 13a is obtained from a, and the reflected light intensity is obtained based on the reflectance corresponding to the recording state of the recording surface 10a.
Figure (a)). As the disk rotates, a portion of the laser beam 12 comes to be irradiated onto the groove 11a, and since the laser beam 12 is focused on the surface of the recording surface 10a, the bottom surface of the groove 11a The reflection direction and phase of the reflected light from above are shifted, and the reflected light flux that is effectively detected becomes 13b shown in FIG. 2(b). The cross section of this reflected light beam 13b decreases as the disk rotates, and as a result, the detected light intensity decreases. next,
As shown in FIG. 2(c), when the laser beam 12 strikes the adjacent recording surface 10b, a reflected beam 13c reflecting the recording state of this recording surface 10b is obtained, and the cross section of the beam is determined by the rotation of the disk. As shown in FIG. 2(d), the signal intensity of the detection light increases until the recording surface 10b is completely irradiated with the entire laser beam 12 and a reflected beam 13d is obtained.

FIG. 3 shows the signal intensity of the detection light obtained by scanning the recording track 5 with the laser beam 12 in this manner. At time t1 when the laser beam 12 is irradiated onto the groove 11 of the recording track 5, the signal intensity decreases, and if the spot of the laser beam 12 is at the center of the recording surface 10, the recording state of the recording surface 1o changes. Accordingly, 1 at time tt and 1 at time t
At 3, a detection strength corresponding to the recorded content of 0 is obtained.

In this first embodiment, the conventional detection signal shown in FIG.
In other words, a detection signal in which a periodic signal identical to the formation period of the groove 11 is superimposed on a data signal reflecting recorded data is obtained, so by using this periodic signal as it is as a synchronization signal, bit synchronization can be performed in real time. can be taken. Therefore, since it is possible to reliably prevent the occurrence of read errors, it is possible to shorten the interval between the recording surfaces 10 constituting each recording bit. There is no need to secure a recording area such as a file section. As a result of these, the recording density of the optical disc can be increased more than before. In this example, the recording bit interval is 1.0 μm.
This is shorter than the conventional method, and the recording capacity of the optical disk can be increased to approximately 1.5 times that of the conventional method.

Note that the same effect can be obtained by providing periodic protrusions on the recording track 5 instead of the grooves 11.

Second Embodiment Next, a second embodiment of the present invention will be described. Note that the configuration of the optical disc as the optical recording medium of this embodiment is as follows:
The second embodiment is the same as the first embodiment except for the surface shape, and the explanation thereof will be omitted. In this second embodiment, as shown in FIG. 4, on the surface of the recording track 5, the recording surface 2 is
0 and the recording surface 21 are formed alternately. Recording surface 20.
The lengths of the recording surfaces 20 and 21 in the scanning direction B are both 0.7 μm, and the step difference between the recording surfaces 20 and 21 is 1.0 μm.

FIG. 5 shows a state in which the recording track 5 is scanned with the laser beam 14. When the spot of the laser beam 14 is on the recording surface 20, as shown in FIG. 5(a), even if the spot diameter of the laser beam 14 is longer than the length of the recording surface 20, the laser beam 14 Since the focus is on the surface of the recording surface 20, only the reflected light beam 15a from the recording surface 20 contributes to the signal intensity of the detection light. Next, as the laser beam 14 moves onto the recording surface 21 of the disk, as shown in FIG. When the spot of the laser beam 14 moves from the recording surface 20 to the recording surface 21 and the intensity of the reflected light from the recording surface 21 increases, the focus servo mechanism moves the laser beam after a certain tracking time. 14 is focused on the recording surface 21. Therefore, when using this optical disk, it is necessary to increase the tracking frequency of the focus servo mechanism from the conventional several KHz to 100 MHz. ), the detected reflected light becomes a reflected light flux 15c from the recording surface 21, and the recording state of the recording surface 21 is read out. When the laser beam 14 hits the step, as shown in FIG. 5(d), the cross-sectional area of the reflected beam 15d decreases, and the signal intensity rapidly decreases.

In this embodiment as well, as in the first embodiment, as shown in FIG. Since they are superimposed, this periodic signal can be used as a synchronization signal. Further, as a synchronization signal source, a focus servo error signal shown in FIG. 7 can also be used to drive the focus servo mechanism.

In this embodiment, the laser beam 1 is as shown in FIG.
Even if the spot diameter of No. 4 is larger than the length of the recording surface 20 or 21, only the reflected light beam from either one of the recording surfaces 20 and 21 contributes to the signal intensity, and the data signals overlap. Detection errors caused by this can be prevented. Therefore, without being limited by the diffraction limit of the laser beam 14, it is possible to make the distance between the recording surfaces 20, 21 smaller than the minimum spot diameter of the laser beam 14, and it is possible to improve the recording density.

In this embodiment, the interval between recording bits can be narrowed to 0.7 μm, and the recording capacity of the optical disc is about twice that of the conventional one.

Third embodiment> Next, a third embodiment of the optical disc according to the present invention will be described.

In this embodiment as well, explanations of parts common to the first embodiment will be omitted.

The recording track 5 of the third embodiment is as shown in FIG.
Two recording slopes 30 and 31 with a mutual angle of 90 degrees are arranged alternately in parallel along the scanning direction, and both recording slopes 30.3
1 are both formed at an angle of 45 degrees with respect to the horizontal plane.

On this recording track 5, the optical head is placed 4 times relative to the horizontal plane.
Recording and playback were performed with the device tilted 5 degrees. As a result, as shown in FIG. 9, laser beams 32.degree. 33 can be irradiated perpendicularly to the respective recording slopes 30, 31.

In this case, the method of recording and reproducing on the optical disk is to continuously record or reproduce on the recording slope 30 on one side, and after the recording or reproduction on the recording slope 30 is completed, recording or reproducing on the recording slope 31 on the opposite side. This is what we do. In this way, when the optical head is accessing the recording slope 30, the recording slope 31 will perform the same function as the step between the recording surfaces 20 and 21 in the second embodiment,
As in the second embodiment, the length of the recording slope 30.31 can be made smaller than the spot diameter of the laser beam. Moreover, in this embodiment, since the total area of the recording slopes 30 and 31 is larger than the area occupied by the recording track 5, the effective recording area is expanded, and the recording capacity of the optical disc can be further increased. .

In this third embodiment, the bit interval can be shortened to 0.5 μm, and the recording capacity of the optical disc is approximately 3 times that of the conventional one.
I was able to double it.

For this optical disc, as shown in FIG. 10, it is also possible to irradiate a laser beam 34 perpendicularly to the disc surface and detect high-order diffracted light returning in the perpendicular direction. In this case, although the signal strength decreases, the area on the recording slope 30.31 where the focal lengths match is
That is, it is limited to short elliptical regions 30a and 31a in the scanning direction of the recording track 5, and the interval between the recording slopes 30 and 31 can be further shortened.

As a result, the bit interval could be shortened to 0.35 μm, and the recording capacity of the optical disc could be increased approximately four times.

<Fourth Example> Finally, an example of an optical recording and reproducing method using the optical disc described in each of the above examples will be described. In this fourth embodiment, as shown in FIG. 12, a laser beam emitted by a laser light source 40 is irradiated onto a recording track 5 of an optical disk via an objective lens 41 that is finely adjusted by an actuator, and the reflected The light flux R passes through the objective lens 41 again and reaches the photodetector 42, where its light intensity is detected. This detection signal T is sent to the gate circuit 44 as well as the periodic signal reading device 43.

In this periodic signal reading device 43, a periodic signal caused by the uneven shape of the recording track 5 is separated from the detection signal T, and this periodic signal is sent to the laser light source 40 as a synchronization signal A for driving the light source, and a synchronization signal B for driving the gate. The signal is sent to the gate circuit 44 as a signal.

The laser light source 40 controls the intensity and spot area of the emitted laser, and accurately strikes the center of the recording surface on the recording track 5 based on the synchronization signal A for driving the light source sent from the periodic signal reader 43. Data is recorded or data on the recording surface is erased.

On the other hand, the gate circuit 44 performs bit synchronization of the detection signal T based on the sent gate drive synchronization signal B.
Data signal C is sent to data processing device 45 as a binary digital signal.

According to this method, unlike conventional recording and reproducing methods, bit synchronization is performed in real time, so there is no room for read errors due to phase shifts between the synchronization signal and the detection signal. Therefore, data can be reproduced accurately, and data can be recorded and erased reliably by adjusting the laser beam.

〔Effect of the invention〕

As explained above, the present invention is characterized in that the recording track of an optical recording medium is provided with concavities and convexities at a predetermined period in the direction in which it extends, and provides the following effects.

■ By using the periodic component in the detection signal based on the unevenness of the recording track as a synchronization signal, bit synchronization can be achieved in real time when recording or reproducing data, so recording and reproduction can be performed with higher precision than before. I can do it. Therefore, it is possible to increase the recording density by shortening the bit interval on the recording track, and it is also possible to prevent the occurrence of reading errors.

■ If multiple recording surfaces with different surface orientations or surface heights are formed within one period of unevenness, only the data signal from one recording surface can be extracted, and the detection signal between adjacent bits can be extracted. Since overlapping can be prevented, the bit interval can be further shortened, and the recording density can be increased.

(2) When at least one of the plurality of recording surfaces is a slope inclined in the direction of extension of the recording trunk, the effective recording area can be increased and the recording capacity can be increased.

■ In the recording and reproducing method using the optical recording medium described above, bit synchronization can be performed using periodic signals generated by the unevenness of the recording trunk. Even when a recording focus with a minimum area is arranged over the entire surface of an optical recording medium to increase the recording capacity, the drive mechanism for recording and reproduction can be simplified, and the accuracy of recording and reproduction can be improved. You can expect to improve.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a recording track shape of a first embodiment of an optical recording medium according to the present invention. FIGS. 2(a) to 2(d) are cross-sectional views showing a state in which a laser beam is irradiated onto a recording track of the same embodiment. FIG. 3 is a graph showing temporal changes in signal intensity based on detected light from the recording track of the same embodiment. FIG. 4 is a perspective view showing the recording track shape of a second embodiment of the optical recording medium according to the present invention. FIGS. 5(a) to 5(d) are cross-sectional views showing a state in which a laser beam is irradiated onto a recording track of the same embodiment. FIG. 6 is a graph showing the temporal change in the intensity of reflected light from the recording track of the same example. FIG. 7 is a graph showing the time change of the focus servo error signal obtained by the reflected light from the recording track of the same embodiment. FIG. 8 is a perspective view showing the shape of a recording trunk of a third embodiment of the optical recording medium according to the present invention. FIG. 9 is a sectional view showing the direction of the laser beam irradiated onto the recording track of the same embodiment. FIG. 10 is a sectional view showing another direction of the laser beam irradiated onto the recording track of the same embodiment. FIG. 11 is a plan view showing a portion of the recording slope that emits a reflected light flux that effectively contributes to the detection signal in the recording track X of the same embodiment. FIG. 12 is a process diagram showing an embodiment of the recording and reproducing method using the optical recording medium according to the present invention. FIG. 13 is a perspective view showing the shape of a part of the optical disc. FIG. 14 is a plan view showing the arrangement of recording marks on the recording track. FIG. 15 is a graph showing temporal changes in signal intensity based on detected light from a conventional optical disc. [Explanation of symbols] 5... Recording track 10 20. 21... Recording surface 11... Groove 12, 14, 32, 33, 3 13a 13b, 13c, 115a,
15b, 15c, 130.31... Recording slope 40... Gate circuit 41... Objective lens 42... Photodetector 43... Periodic signal reader 44... Gate circuit 45... Data processing device T...Detection signal A...Light source drive synchronization signal B...Gate drive synchronization signal C...Data signal. 4...Laser beam 3d. 5d...Reflected light flux Figure 1 Figure 3

Claims (5)

[Claims] (1) In an optical recording medium having a recording track on which information can be recorded or reproduced by optical means, unevenness is provided on the surface of the recording track at a predetermined period in the extending direction of the recording track. An optical recording medium characterized by: (2) In the optical recording medium according to claim 1, the unevenness is such that a plurality of recording surfaces parallel to the extension direction and having different surface orientations or surface heights are formed within the predetermined period. An optical recording medium characterized by: (3) The optical recording medium according to claim 2, wherein at least one of the plurality of recording surfaces is a slope inclined in the direction in which the recording track extends. . (4) A recording/reproducing method using the optical recording medium according to claim 1, wherein the optical recording medium is detected in synchronization with periodic fluctuations in detected light intensity obtained based on the unevenness during scanning of the recording track. A recording and reproducing method using an optical recording medium, characterized in that the recorded content of the recording track is read from the detected light intensity. (5) A recording/reproducing method using the optical recording medium according to claim 1, wherein the recording is performed in synchronization with periodic fluctuations in detected light intensity obtained based on the unevenness when scanning the recording track. A recording/reproducing method using an optical recording medium, characterized in that data is recorded or erased on the recording track by adjusting characteristics of light irradiated onto the track. (6) A recording and reproducing method using the optical recording medium according to claim 4 or 5, wherein the detected light intensity is the intensity of a focus error signal. Recording and playback method to use.