JPS6338774B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a disc-shaped information recording medium and a method for reproducing the same, in which main information signal pits are formed with different shapes in the radial direction to obtain a reference signal for tracking control of the main information signal pits. It is an object of the present invention to provide a reproducing method which can be used as a pit for recording data, can densely form a main information signal track pitch, and can be reenergized with a simple circuit configuration.

The present applicant has previously developed an electrode in which the main information signal and the first to third tracking control reference signals (hereinafter referred to as tracking signals) are recorded as changes in the geometric shape without forming a needle guide groove. Reproduction in which the main information signal and tracking signal are read and reproduced as changes in capacitance by scanning a functional disk-shaped information recording medium (hereinafter referred to as a disk) and a reproducing needle having an electrode function by relative sliding movement of the medium and a reproducing needle having an electrode function. proposed a device.

As shown in FIGS. 1 and 2, on the surface of the disk, a main track 3 for recording main information signals such as video signals is formed in a spiral manner, and is made up of repeated flat surfaces 1 and pits 2. On both sides, there is a first tracking signal f _p1 (marked with a circle) in which pits 4 and flat surface 1 are repeated, and pits 5 and flat surface 1 are repeated at frequencies lower than the recording frequency band of the main information signal. The second tracking signal f _p2 (×
In addition, a third tracking signal f _p3 for switching the tracking polarity of the tracking servo circuit is recorded at the switching connection portion (broken line) of the tracking signals f _{p1 and f p2 .} ing. On the other hand, it is detected that the capacitance formed between the regeneration needle 6, the electrode 6a and the rotating disk 7 changes according to the intermittent row of pits,
Convert to RF signal.

As shown in FIG. 3, the pickup circuit 8 mainly consists of a coaxial resonant section and an AM detection section, and the capacitance change detected by the regeneration needle 6 is extracted as a change in the resonant frequency of the coaxial resonant section. It can be done. A signal with a constant frequency is supplied to the coaxial resonator from the outside, and an RF signal having a predetermined amplitude change whose frequency changes in accordance with changes in capacitance is extracted from the coaxial resonator. This change in amplitude corresponds to the depth of the pit and is constant. The RF signal is
After being detected by the AM detection section and amplified by the preamplifier 9, only the main information signal is extracted by the main information signal filter 10, and demodulated by the main information signal demodulation circuit 11.

On the other hand, the RF signal from the preamplifier 9 is separated into a first tracking signal f _p1 and a second tracking signal f _p2 by an f _p1 filter 12 and an f _p2 filter 13 and supplied to a switch circuit 14 . or,
The third tracking signal f _p3 extracted by the f _p3 filter 15 is envelope-detected by the detection circuit 16 and then supplied to the switch circuit 14 . Therefore, switching is performed every rotation of the disk 7. As a result, the tracking signals f _p1 and f _p2 supplied to the detection circuits 17 and 18 are alternately switched. That is, the left and right tracking signals of the main information signal track are 1.
The configuration is such that a predetermined tracking control signal is always taken out even if the left and right signals are swapped every rotation. The tracking signal whose envelope has been detected by the detection circuits 17 and 18 is supplied to a differential amplifier 19 to be converted into a tracking error signal, and is converted to a drive signal by a drive circuit 20 and supplied to the tracking coil 21 of the regeneration needle 6. , so that the reproduction needle 6 always traces the main information signal track 3.

In the present invention, the tracking signals on the left and right sides of the main information signal track are omitted so that the main information signal pit itself can be used as a tracking signal pit. An embodiment thereof will be described with reference to FIG. 4 and subsequent figures.

4 and 5 respectively show a schematic perspective view of an embodiment of a disc-shaped information recording medium according to the present invention and a block system diagram of an embodiment of a method for reproducing the same. In the figure, on the surface of a disk 29, a main information signal recording main track 32 consisting of a repeated flat surface 30 and pits 31 is formed in a spiral shape without intervening tracking signal sub-tracks. Pitt 3
1 has a substantially triangular shape, and is formed so that the apex corresponds to the inner circumferential direction and the bottom corresponds to the outer circumferential direction,
When the electrode 33a of the reproduction needle 33 traces the center line _l2 of the pit 31 and the flat surface 30, the amplitude of the RF signal from the coaxial resonance part is constant, and the level of the envelope detection output becomes equal to the predetermined threshold level. It is configured as follows.

For reproduction, a reproduction apparatus as shown in FIG. 5 is used. A signal taken out from the pickup circuit 8 and having a frequency corresponding to a change in capacitance caused by intermittent pit rows on the disk 29 is amplified by a preamplifier 9 and then supplied to a demodulation circuit 10 for demodulation.
At this time, since only the main information signal is recorded on the disk 29, there is no need to provide a main information signal filter like the conventional circuit shown in FIG.

On the other hand, the AM detection output from the pickup circuit 8 has a constant amplitude, and the envelope detector 34
After the envelope on one side is detected by the level comparator 2
8. The level comparator 28 has a terminal 27
A threshold level signal is supplied from the envelope detector 34, and the level difference between the envelope level from the envelope detector 34 and the threshold level is compared in the level comparator 28.
When the electrode 33a of the regeneration needle 33 correctly traces the center line _l2 (FIG. 6A), the level comparator 2
Although no tracking error signal is extracted from 8, if the reproduction needle 33 is displaced toward the outer circumference of the disk 29 (FIG. 6B), the opposing area of the electrode 33a and the pit 31 will be larger than that during normal tracing. The capacitance becomes large. As a result, the level of the AM detection output from the pickup circuit 8 becomes higher than that during normal tracing.
Therefore, the envelope level extracted from the envelope detector 34 is higher than that during normal tracing, and is compared with the threshold level in the level comparator 34, and a tracking error signal corresponding to the level difference is detected. Served. This signal is supplied to the tracking coil 21 via the drive circuit 20, and is controlled to displace the reproduction needle 33 in the inner circumferential direction of the disk 29. On the other hand, as shown in FIG. 6C, the electrode 3
When 3a shifts toward the inner circumference, the capacitance decreases,
The regeneration needle 33 is controlled to be displaced in the direction of the outer circumference of the disk.

Further, the recording medium according to the present invention can be applied not only to a capacitive type but also to an optical type. That is, if a pit-shaped recording medium such as the recording medium of the present invention is used in an optical video disc playback device, when a tracking error occurs, the detection level of the main signal will be extremely different from that during normal track tracing. , this allows tracking control to be performed. Therefore, by using the recording medium of the present invention, a tracking error signal can also be obtained using only the detection device for detecting the main information signal.

As described above, in the disk-shaped information recording medium and the method for reproducing the same according to the present invention, the shape of the pit of the main information signal is formed by gradually varying the length in the rotational direction in the radial direction. When the element is traced off the center of the main information signal pit, the reproduced main information signal at a level different from the level of the reproduced main information signal when the reproduction element traced the center of the pit is extracted and used as a tracking error signal. Therefore, the main information signal can also be used as a tracking reference signal as it is, and the main information signal track pitch is lower than that of conventional capacitive information recording media in which reference signal tracks for tracking control are provided on both sides of the main information signal track. and a filter for separating the main information signal and the reference signal for tracking control from the reproduction signal, such as a conventional reproduction apparatus for reproducing this capacitive information recording medium, and a filter for left and right tracking control. Since there is no need to provide a switch to switch the reference signal for each rotation of the recording medium, an error amplifier to obtain the tracking error signal, etc., the circuit can be constructed more easily and at lower cost than conventional playback devices. Furthermore, it has the advantage that it is easier to manufacture the disk than, for example, when the pits are shaped to have different depths in the radial direction.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the recording position of a reference signal for tracking control on a disk-shaped information recording medium previously proposed by the present applicant, and FIG. 2 shows the reproduction state of the recording medium shown in FIG. 1 and the reproduction needle. Partially enlarged perspective view shown, 3rd
Figure 1 is a block diagram of an example of a reproducing device previously proposed by the applicant for reproducing the recording medium shown in Figure 1, and Figure 4 is a partial enlargement of an embodiment of the disk-shaped information recording medium of the present invention. A perspective view, FIG. 5 is a block system diagram for explaining one embodiment of the disc-shaped information recording medium reproducing method according to the present invention, and FIGS.
FIG. 3 is a schematic plan view for explaining a state in which a reproducing needle electrode faces a pit of the illustrated recording medium. 8...Pickup circuit, 11...Main information signal demodulation circuit, 20...Drive circuit, 21...Tracking coil, 29...Disc-shaped information recording medium, 3
0... Flat surface, 31... Pit, 32... Main information signal track, 33... Regeneration needle, 33a... Electrode, 28... Level comparator, 34... Envelope detector.

Claims (1)

[Claims] 1. In a disk-shaped information recording medium in which a main information signal is recorded as a change in geometric shape, the shape of the pit of the main information signal is defined by the length in the rotation direction in the radial direction. A disc-shaped information recording medium characterized by being formed with gradually different shapes. 2. In a method for reproducing a disc-shaped information recording medium in which the main information signal is read and reproduced as a change in capacitance from a disc-shaped information recording medium in which the main information signal is recorded as a change in geometric shape, the main information signal is When reproducing a disk-shaped information recording medium formed by forming pits whose lengths in the rotational direction gradually vary in the radial direction, the reproducing element is traced off the center of the pit of the main information signal. When the reproducing element traces the center of the pit of the main information signal, a reproduced main information signal having a level different from the level of the reproduced main information signal when the reproducing element traces the center of the pit of the main information signal is extracted and used as a tracking error signal of the reproducing element. A method for reproducing a disc-shaped information recording medium.