JPS6012834B2 - information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information recording medium, and particularly to an information recording medium on which information can be easily tracked.

In recent years, there has been an increasing need to record large amounts of image information, and research for this purpose has been active.

Among these, methods of recording information with high density on a rotating body such as a disk are attracting attention. Each frame of information, such as a video signal for television display, is recorded on one track, and a large number of these tracks are arranged concentrically. At this time, in order to record a large amount of information, extremely high-density recording is performed. For example, 1 micron pitch within a track, 1-2 micron pitch between tracks.
It is like a micron pitch. When such a high-density disk is rotated at a high speed, for example, about 60 revolutions per second, the problem is how to faithfully follow the track (tracking). The present invention is based on this tracking method. This will be explained below using the drawings. In FIG. 1, a disk is specifically taken up, and tracks are schematically shown here.

That is, tracks 10, 102, . FIG. 2 is an explanatory diagram of recording signals on a track. 10 in figure A
0 to 1003 indicates the use of media with different surface reflectances or transmittances. For this purpose, a suitable substance may be coated, and after the deposition, the transmittance or reflectance may be recorded as appropriate depending on the signal.
The simplest example is a photographic emulsion. FIG. 2B shows an example in which signals are recorded by surface irregularities.

FIG. 3 is a basic explanatory diagram of reading signals from such a disk. The light from the laser 2 passes through a mirror 3, a half mirror 4, and a focusing lens 5, and is focused onto the disk, and the reflected light from there is sent to a half mirror 4, a photodetector 6,
and a demodulator 8 to obtain a signal, for example a video signal for TV display.

The signal for this tracking is passed through an appropriate tracking error signal discrimination circuit 9 to a mirror deflection drive circuit 11, and changes the angle of the mirror 3 so that the light is correctly irradiated onto the track. Make it. FIG. 4 is an enlarged view of the signal recording portion on the track.

100,,10 on tracks 10,,102,103
02, 1003, it is recorded in the form of surface irregularities, for example. The track spacing 1 is about 1-2 microns, and during recording of the signal within the track d is about 1-2 microns. Now, the problem with such a system is how to generate a tracking error signal.

FIG. 5 is a diagram showing an example of recording such a tracking signal. The track 10 includes video signal portions 20, . ,2
In addition to 0, 2, etc., tracking signals 30,
．． , 30, 2... are recorded. This tracking signal consists of two parts, 300, 3002, which are offset from the center of the track by half a track. Now, suppose that this tracking signal is recorded in an appropriate form, and when the light beam is located at the center position of this track, the outputs from these two tracking signal parts 3001 and 3002 will be the same, but if the light beam is , one can be made to be larger than the other.

This is shown schematically in FIG.

a and b are tracking signal parts 3001 and 30, respectively
This is the output from 02.

At A, since the light beam is located at the center of the track, both outputs are equal, and the difference signal is zero as shown at c.

0 Now, when the light beam deviates upward in FIG. 5, the signal at a becomes larger than the signal at b, as shown in diagram B, and therefore, this difference becomes positive.

On the other hand, when the light beam shifts downward, as shown in FIG. 6c, the signal a becomes smaller than the signal b, and this difference becomes negative. Therefore, the direction of deviation can be determined from this difference signal.

This pattern is shown in FIG. That is, a tracking error signal can be obtained depending on the amount and direction of deviation of the light beam. Therefore, using this error signal, the direction of the light beam may be controlled so that this error signal becomes zero. The problem here is that the tracking signal 300
1,3002 is recorded in what form. Generally, FM modulation is used to obtain a high signal-to-noise ratio. Therefore, the previous tracking signal may be recorded at two different frequencies f, , f2. 8th
The figure schematically shows this, and it can be seen that the tracking signal is expressed in forms with different pitches. The signal will be explained in more detail. In Figure 9,
This is an example of a frequency spectrum when a video signal for TV display is subjected to FM modulation.

For example, between 3.8MHZ and 4.8MHZ (part B)
The fundamental frequency is distributed in , and its harmonics are below it (part A
).

An example is to set the two tracking frequencies f, , f2 to 4.9 MHz or higher as shown in the figure. Signal detection at this time is performed as shown in FIG. This description is only for the photodetector 6 and below in FIG. 3. That is, the output of the photodetector 6 is appropriately amplified and then passed through three hand-pass filters. Phil evening 1
2. Only video signal components of 4.9 MHz or less are allowed to pass through, and are further supplied to a demodulator 8 to obtain a video signal for TV display.

On the other hand, the filters 122 and 123 allow only the f and f2 components to pass through, respectively.

These filter outputs are preferably sent to the mirror deflection drive circuit 11 as an error signal via the demodulators 82 and 83, the differential amplifier 13, and an appropriate error signal generation circuit 9. Figure 11 shows the case where the values of f, , etc. are selected in the video frequency domain.

A synchronizing signal is required to separate the signal from the video signal.
FIG. 12 shows an embodiment of the present invention. Video signal part 20
、． ,2012... The synchronization signal portion 40,
．． , 408 are provided. After this, the tracking signal 30,
．． , 308, etc. are provided. The f, , f2 components after this synchronization signal are regarded as tracking signals. Specifically, this is carried out according to the circuit shown in FIG.

As before, one of the outputs from the photodetector 6 is directly sent to the video signal demodulator 8. However, the synchronization signal detected from this output is
Sent to 2. This gate circuit is for operating the filters 122 and 123 only for a certain period of time immediately after the synchronization signal is detected. The filters 122 and 123 respectively allow only f, f2 components to pass through. The subsequent output processing is exactly the same as that shown in FIG. In the case of a general TV display, the synchronization signal mentioned here is included in the horizontal line period, and moreover, the tracking signal 300, 3
002 etc. can also be incorporated into this horizontal line period.
Therefore, in the case of general TV display, not only is there no need to newly provide a synchronization signal, but also there is no need to introduce a tracking signal, which will cause loss of information or an increase in the required bandwidth. Has practical advantages.

In addition, the synchronization signal included in the reproduced video signal can be used as a timing signal for detecting the tracking signal, and a recording medium exclusively for the timing signal can be provided.
Another advantage is that there is no need to provide a special timing signal generating means such as detecting the rotation of the recording medium.

Furthermore, when the tracking signal is placed in a portion of the center line of the track that belongs to the horizontal line period of the video signal, the following advantages are obtained. That is, when a tracking signal is continuously recorded over the entire recording track, even if the frequency f or f2 of the tracking signal is placed outside the band occupied by the recorded video signal, for example on the lower frequency side, the reproduction will not be possible. Due to the nonlinearity of the recording medium, detector, circuit, etc. at the time, when the frequency of the recorded video signal is f, a frequency component of f + nf, or f±nf2 (n: natural number) mixes into the band of the video signal, This cannot be removed. This component appears as a moiré component on the playback screen and significantly impairs image quality. The only way to prevent this is to lower the recording level of the tracking signal, but then a track deviation signal with a sufficient S/N ratio cannot be obtained. However, if the tracking signals are placed in portions of the track center line that belong to the horizontal line period, even if this moiré component occurs, it will not affect the playback screen. Therefore, it becomes possible to record a tracking signal at a sufficient recording level, and a track deviation signal with a sufficient S/N ratio can be obtained. In the examples of Figures 5 and 12, f,,f
The two tracking signals are arranged adjacent to each other on the same track. This can actually be simplified further. FIG. 14 shows another embodiment of the present invention, in which f, , and rims are arranged temporally shifted. Therefore, it becomes easy to record such signals. When the track spacing is close, it becomes difficult to always use the f2 signal independently for each track. Figure 15 shows a solution to this problem. For example, 30012 is track 101
and 102. 0 At this time, in the track 10, the component increases even if the light beam shifts upward, whereas in the track 102, the component also increases.

Therefore, in order to correct this difference, it is necessary to invert the sign of the error signal for each track. Ta 1st
In the example shown in Figures 4 and 15, the tracking signal is first 300,
, 3002, and other information can be recorded in the margin (such as below 300).

0 FIG. 16 further simplifies the signal recording, with 300 phantoms used for both tracks 10, 102.

In this case as well, the sign of the error signal must be switched for each track, as in the example shown in FIG. To record the tracking signal shown in FIG. 16, synchronization signals 40, .
Then 300, . Next, write 20, 2, etc. In the next track, write 408, then 3002, then 202. In the above example, for the same track,
The positional relationship between f and f2 is interposed. For example, the first
In the example shown in Figure 6, tracks 10 and 102 each have f
,,f2 are on the upper side. Therefore, as shown in FIG. 6, the difference signals obtained from the same track continue to have almost the same sign.

This is not necessarily optimal for subsequent signal processing. Furthermore, in the examples shown in FIGS. 15 and 16, it was necessary to invert the sign of the relationship between the error signal and the deviation for each track. As a method for solving this problem, there is a method shown in FIG.

In other words, one track has L, f2, L,...f2・
The tracking signals f, , ra, f are mixed together with the tracking signals f, , ra, f.

When the output of the photodetector 6 shown in FIG. 3 is given, the result as shown in FIG. 18A will be obtained if tracking is performed completely.

That is, a and b are the outputs for f, , f2, respectively, and c is the difference output. If the light beam shifts upward in FIG. 17, the result will be as shown in FIG. 18B. As a result, a difference output c is obtained. On the other hand, if it is shifted downward, the result will be as shown in FIG. 18c.

From the comparison of FIGS. 18B and 18C, there is a certain relationship between the direction of deviation of the light beam and the difference signal c.

That is, considering the fundamental frequency component of the pulse train c, the phases are opposite in FIGS. 18B and 18C.

In Figure 18A, the difference signal is zero. Therefore, now the 18th
If the case of figure B is the in-phase component, the case of figure 18C is the opposite phase.

Therefore, if we find these components out of the difference signal and find X = in-phase component - anti-phase component, the relationship between this X can be used as an error signal.

In fact, this type of detection can be performed using the system shown in FIG.

This is an explanation for the case shown in FIG. The same applies to the case shown in FIG. Of the outputs from the photodetector 6, tracking signals of frequencies f, , f2 are obtained via filters 122, I23, and are sent to an appropriate demodulator 82.
, 83 and further to the differential multiplier 13, whose output is supplied to the differential multiplier 132 via synchronous, anti-phase demodulation circuits 80, 802. This output is given to the error signal generation circuit 9. For example, when the optical beam is shifted above the track, the demodulators 82 and 83 produce the output pulses shown in FIG. A dynamic signal can be obtained.

Of the fundamental frequency (which corresponds to two horizontal scanning periods in the present example) component of this differential signal, the in-phase component (as shown in FIG. A demodulating circuit 80
, is obtained. Similarly, among the fundamental frequency components of the above-mentioned differential signal, anti-phase components (as shown in FIG. 18C, after regions 40, ., 40, 2 in FIG. 17, respectively)
(having negative and positive values) is determined by the demodulation circuit 802. In the case of FIG. 188, only the in-phase component has a positive value, and the anti-phase component has a value of 0. Therefore, a positive signal is output from the Ashikin intensifier 132. In exactly the same way, the first
In the case of FIG. 8C, a negative value signal is output from the differential amplifier 132. Thus, depending on the sign and magnitude of the output of the differential intensifier 132, the error signal generation circuit 9 sends an error signal to the mirror deflection drive circuit 11 for positioning the light beam to the center of the track. The following is the same as before.

Finally, recording of tracking signals will be specifically explained.

In this case, video signals are sequentially recorded on predetermined tracks on the rotating disk, and when it is time to write a tracking signal, the recording light beam is slightly deflected so that the light beam is placed at a position offset from the center of the track. to come.

For example, in FIG. 16, synchronization signal sections 40, . After writing the tracking part 300, . , and then return the light beam to its original position and continue to 20,2. this house,
300,. In order to write tracking signals over a wide area inside the track, it is also effective to wave the light beam in a direction perpendicular to the track. The above demonstrates that the present invention provides simple and accurate tracking.

Although the description has been made regarding disks, the same applies to drums, tapes, etc.

Furthermore, although a video signal for TV display has been described as a signal, it is generally effective for recording information in general. Further, although the recording method has been described using FM modulation, it is clear that the recording method is not limited to this.

[Brief explanation of the drawing]

Figure 1 is a conceptual explanatory diagram of disks and tracks;
The figure is an explanatory diagram of the recording format of signals on the disc, Figure 3 is an explanatory diagram of the reproduction of signals from the disc, Figure 4 is an explanatory diagram of an enlarged view of the track, and Figure 5 is an explanatory diagram of the recording of tracking signals. An explanatory diagram, FIG. 6 is an explanatory diagram of reproduction of the tracking signal,
Fig. 7 is an explanatory diagram of the error signal and the amount of deviation, Fig. 8 is the tracking signal, Fig. 9 is the video signal and the tracking signal,
FIG. 10 is an explanatory diagram of each of the signal processing systems, and FIGS. 11, 12, and 13 are explanatory diagrams of embodiments of the present invention. FIGS. 14 to 17 are diagrams showing other embodiments of the present invention, and FIGS. 18 to 20 are illustrations of tracking signal processing according to the present invention. Here, 1...jisuku, 10, ~
103...Track, 100-1003...Signal recording element, 200...Disc rotation direction, 2...Laser, 3...Mihu, 4...Half mirror, 5...Lens, 6
......Photodetector, 8...Demodulator, 9...
Error signal generation circuit, 10, to 103... Track, 11... Mirror deflection drive circuit, 12..., 1
22,123...Filter, 13,13,,132,...
...differential multiplier, 20,. ,20,2... Information recording part, 30,. , 30, 2... Tracking signal recording section, 40, . , 40, 2... Synchronization signal recording section, 80
,,802... Synchronous detector, 100...100
3...Signal recording element, 300,,3002...
...Tracking signal. Shizu'zu younger brother zA figure 28 figure 3 figure Tsutomu 4 figure 5 figure 7 figure 5 figure 8 figure 8 '5 Many illustrations '5 Illustration Leopard / 7 Figure 8 Group of Figures of '8A Figure Ticket '8c Younger Brother Smoke Group Figure

Claims (1)

[Scope of Claims] 1. In an information recording medium in which a predetermined signal is formed in a track shape, a recording area in which a tracking signal for tracking the predetermined signal along the track is recorded and a timing for detecting the tracking signal. An information recording medium characterized in that recording areas in which signals are recorded exist intermittently along the track. 2. The information recording medium according to claim 1, wherein the predetermined signal is a video signal, and the timing signal is a synchronization signal of the video signal. 3. The information recording medium according to claim 1, wherein the recording area for the tracking signal is provided outside the track, and the recording area for the timing signal is inside the track. 4. The information recording medium according to claim 1, wherein in the recording area of the tracking signal, signals of different frequencies are recorded as the tracking signal on both sides of the center line of the track. 5. Information recording according to claim 1, wherein in the recording area of the tracking signal, signals of different frequencies are recorded as the tracking signals so as to alternately go out in opposite directions. Medium. 6. The information recording medium according to claim 1, wherein the recording area for the tracking signal is provided so as to be shared between adjacent tracks.