JPS62170001A - Information signal processing circuit - Google Patents

Abstract

PURPOSE:To obtain reproducing information with excellent S/N even at the inner circumference of a recording disk medium by using a control signal in response to the position of a read head so as to correct a noise cancellation signal formed based on a reproducing information signal. CONSTITUTION:A noise cancellation signal is formed and fed to a voltage control amplifier circuit 36 by a noise cancellation signal forming section 35 provided with an HPF 31, a limiter 32 and a level adjusting circuit 33 or the like based on a signal reproduced and demodulated after being read from the recording disk medium via a reproducing amplifier circuit 25 and a demodulation section 30. On the other hand, an envelope detector 14 in response to the output of the circuit 25 detects the envelope of the reproducing signal changing in response to the read position to output a control signal corresponding to the position of the read head and supply the signal to the circuit 36. Thus, the noise cancellation signal corrected depending on the location of the read head 20 is outputted from the circuit 36, the noise component of a demodulation signal is eliminated via a subtraction circuit 38 and the reproducing information with excellent S/N is obtained even from the inner circumference of the recording medium.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B. Overview of the invention C. Prior art D. Problem to be solved by the invention E. Means for solving the problem F. Effect G. Example G-1 Structure of the example (Fig. 1) G -2 Operation of the embodiment (Fig. 1, Fig. 2, Fig. 4) c-i Modified example (Fig. 3) H Effect of the invention A Industrial application field The present invention can be formed in a concentric or spiral shape. The present invention relates to an information signal processing circuit that obtains a reproduced information signal based on a read signal from a disk-shaped recording medium in which an information signal is recorded on a track that has been recorded, and performs processing to reduce noise components on the obtained reproduced information signal.

B. Fourth Summary of the Invention The present invention provides a read head unit that is moved in the radial direction of a disk-shaped recording medium on which information signals are recorded with concentric or spiral tracks and is rotated at a constant rotational speed. In an information signal processing circuit that obtains a reproduced information signal from a read signal from a reading means that includes the read signal, and performs processing to reduce noise components in the obtained reproduced information signal, the noise component is reduced based on the reproduced information signal obtained from the read signal. In addition to forming a cancellation signal, a control signal corresponding to the position of the reading head with respect to the disk-shaped recording medium is formed based on the read signal, and the level of the noise cancellation signal is changed according to the control signal to generate a corrected noise cancellation signal. By supplying the obtained corrected noise cancellation signal and reproduction information signal to the subtracting section, the signal-to-noise signal is transmitted from the subtracting section to the reading signal even when the throat section is located on the inner circumferential side of the disk-shaped recording medium. This makes it possible to obtain a reproduced information signal with an improved ratio.

C. Conventional technology A disk on which an information signal such as a video signal is recorded is rotated at a constant rotational speed, and a reading means including a gutter section arranged to move in the radial direction of the disk reads the information from the disk. An information signal reproducing system has been proposed in which a read signal is obtained, the obtained read signal is supplied to a demodulator, and a reproduced information signal such as a reproduced video signal is obtained from the demodulator. A disk used in such an information signal reproduction system is, for example, a disk on which information signals are magnetically recorded to form a large number (for example, about 50) annular tracks arranged concentrically or spirally. In each annular track, a predetermined section of the information signal, for example, one frame period or one field period in the case of a video signal, is converted into a frequency modulated signal and is It is assumed that the level is recorded and the track address data indicating the absolute address of the track is encoded and recorded.

In such an information signal reproduction system, when an information signal such as a video signal is reproduced from a disk in which information signals such as video signals are recorded with a large number of annular trunks as described above, the reading means reads each annular trunk of the disk. A read signal obtained by reading from the track is supplied to a demodulator,
In the demodulation section, the read signal is supplied to the demodulation circuit via the limiter and demodulated, and the output of the demodulation circuit is derived via the de-emphasis circuit,
Although an information signal is obtained from the demodulation section, the reproduced information signal usually contains undesired noise components. Therefore, in order to remove this noise component, for example, the reproduction information signal obtained from the demodulation section is supplied to the noise cancellation signal formation section, and the noise cancellation signal formation section performs noise cancellation corresponding to the noise component included in the reproduction information signal. A noise canceling process is performed in which a signal is formed and a noise canceling signal is subtracted from the reproduced video signal.

In performing such noise canceling processing, in the noise canceling signal forming section, the reproduced information signal is supplied to a bypass filter to extract high frequency components from the reproduced information signal, and the level of the high frequency components is After being made constant by a limiter, it is further adjusted and processed to become a noise canceling signal. Therefore, the noise cancellation signal has a constant level that has been adjusted in a predetermined manner, and when subtracted from the reproduction information signal, it cancels out the noise component contained in the reproduction information signal.

D. Problems to be Solved by the Invention However, it is possible to obtain reproduced information signals by rotating a disk on which information signals are recorded at a constant level on a large number of annular tracks at a constant rotational speed. In the 4-report signal reproduction system, when noise canceling processing is performed on the reproduced information signal using the noise canceling signal as described above, there are problems as described below.

That is, when the reading means obtains a read signal from each annular trunk of the disk, the reading head included in the reading means scans each annular track of the disk, and the position of the reading head relative to the disk is The relative speed between each annular track and the reading head section decreases as it moves from the outer circumferential side to the inner circumferential side.

Therefore, the level of the reproduced information signal obtained based on the read signal obtained from the reading means when the reading head section scans each annular track of the disk is based on the information signal recorded at a constant level on each annular track. So, the fourth
As shown by the solid line p in the figure, the position of the reading head relative to the disk decreases as it moves from the outer circumferential side of the disk to the inner circumferential side of the disk. In other words, the level of the reproduced information signal changes depending on the position of the read throat section relative to the disk, and accordingly, the level of the noise component included in the reproduced information signal also changes depending on the position of the read head section relative to the disk. It will change accordingly.

On the other hand, as mentioned above, the noise canceling signal obtained from the conventionally proposed noise canceling signal forming section has a constant level that has been adjusted in a predetermined manner, regardless of the position of the reading head section with respect to the disk. It is said that Therefore, even if the noise cancellation signal is subtracted from the reproduction information signal, the difference between the level of the noise component included in the reproduction information signal and the level of the noise cancellation signal may occur depending on the position of the read head with respect to the disk. becomes large, and the noise component included in the reproduced information signal is not canceled out sufficiently, resulting in a situation where the signal-to-noise ratio (S/N ratio) of the reproduced information signal decreases. For example, if the level of the noise cancellation signal is set so that the noise component included in the reproduced information signal is sufficiently canceled when the read head is located at the outermost circumference of the disk, the S/ As shown by the broken line q' in FIG. 4, the N ratio decreases significantly as the position of the read head relative to the disk moves from the outer circumferential side of the disk to the inner circumferential side of the disk.

Furthermore, when obtaining a reproduced information signal from a disc on which an information signal has been recorded, a problem arises due to the difference in relative speed between the disc and the read head section between the inner and outer periphery of the disc. As a measure against this, for example, as described in Japanese Patent Application Laid-Open No. 55-1/12422, in an optical information reproducing device, the frequency characteristics of the read signal supplied to the information signal processing circuit are It has been proposed to change the track address separated from the disc in accordance with the incoming address signal. However, such a method does not allow a disc in which information signals are recorded at a constant level on a large number of annular tracks. To solve the above-mentioned problem that occurs when noise canceling processing is performed on a reproduced information signal using the above-mentioned noise canceling signal in an information signal reproduction system that obtains a reproduced information signal by rotating at a constant rotation speed. It is not possible.

In view of the above, the present invention provides a disc-shaped recording medium in which information signals are recorded with concentric or spiral tracks and is rotated at a constant rotational speed, and a reading device arranged to scan the tracks with respect to the disc-shaped recording medium. Obtaining a reproduction information signal from a read signal obtained through a reading means including a head unit, forming a noise canceling signal based on the obtained reproduction information signal, and performing noise canceling processing on the reproduction information signal using the signal. In doing so, regardless of the position of the reading head with respect to the disk-shaped recording medium, for example, even when the reading head is located on the inner circumferential side of the disk-shaped recording medium, noise components contained in the reproduced information signal can be canceled. It is an object of the present invention to provide an information signal processing circuit that can perform proper processing and obtain a reproduced information signal with an excellent signal-to-noise ratio.

E. Means for Solving the Problems In order to achieve the above object, the information signal processing circuit according to the present invention uses a disk on which information signals are recorded with concentric or spiral trunks and is rotated at a constant rotational speed. a demodulator that obtains a reproduction information signal based on a read signal from a reading means including a reading head disposed movably in the radial direction of the shaped recording medium; and a demodulator that generates a noise canceling signal based on the reproduction information signal from the demodulator. a control signal forming section that obtains a control signal corresponding to the position of the reading head relative to the disk-shaped recording medium based on the read signal; and a control signal forming section that generates a corrected noise cancel signal from the noise cancel signal and the control signal. and a subtraction section to which the reproduced information signal and the corrected noise cancellation signal are supplied. Then, the signal correction section is
A corrected noise cancellation signal is formed by changing the level of the noise cancellation signal in accordance with a control signal that corresponds to the position of the reading head with respect to the disk-shaped recording medium.

In the information signal processing circuit configured in this manner with F action,
In the calculation section, subtraction is performed between the reproduction information signal obtained from the demodulation section and the corrected noise cancellation signal obtained from the signal correction section, and the noise component included in the reproduction information signal is canceled by the correction noise cancellation signal. . At this time, the noise component included in the reproduced information signal has a level change depending on the position of the reading head with respect to the disk-shaped recording medium. Since the corrected noise cancellation signal obtained by changing the level according to the control signal from the control signal generating section also has a level change according to the position of the reading head section with respect to the disk-shaped recording medium, the subtracting section Correction of the noise component included in the reproduced information signal in
This is done properly regardless of the position of the read head relative to the medium, and as a result, the subtraction section provides a reproduced information signal with an excellent signal-to-noise ratio, regardless of the position of the read head relative to the disk-shaped recording medium.

G Embodiment G-1 Configuration of Embodiment (FIG. 1) FIG. 1 shows an example of an information signal processing circuit according to the present invention, together with the main parts of an information signal reproduction system to which the circuit is applied.

In FIG. 1, for example, 50 tracks T are formed concentrically on a disk 10 with a predetermined track pitch.

In each track T, a video signal for one field period as an information signal is magnetically recorded as a frequency modulated signal together with track address data. ``The disk 10 is rotated based on the rotation of the spindle motor 11. A magnetic yoke 12 is attached to a predetermined position in the center of the recording surface side of the disk 10, and a disk rotation phase detection head 14 faces the recording surface of the disk 10 and detects leakage magnetic flux from the magnetic yoke 12. is arranged so that a disk rotational phase detection pulse PC,o can be obtained from the disk 14 for disk rotational phase detection. This disk rotation phase detection pulse PGo is supplied to the system control section 100, and a pulse PGc similar to the disk rotation phase detection pulse PGo is obtained from the system control section 100 and is supplied to the speed servo circuit 16. The output is supplied to the spindle motor 11, and the disk 10 is rotated for 1760 seconds corresponding to one field period of the video signal.
It is rotated at a constant rotational speed.

A read head 20 is disposed in contact with the disk 10 and scans a track T formed on the disk 10 as the disk 10 rotates and reads signals from the track T. The reading head 20 is moved in the radial direction of the disk 10 by a head feeding mechanism 22 based on the rotation of the stamping motor 21. The stamping motor 21 includes a motor drive circuit 23 to which a motor drive control signal MD is supplied from the system control section 100.
driven by.

The reading head 20 reads the signals recorded on each track T of the disk IO, and the read signal Sa obtained from the reading head 20 is supplied to the reproduction amplification circuit 25 and amplified. Read signal Sa
is derived. A portion including the reading head 20 and the reproduction amplification circuit 25 forms a reading means.

The read signal Sa derived from the reading means is transmitted to the limiter 26
After the amplitude fluctuation component is removed, the signal is supplied to the demodulation circuit 27. In the demodulation circuit 27, the video signal in the read signal Sa, which is a frequency modulated signal, is demodulated, and a reproduced video signal sb is obtained from the demodulation circuit 27.

This reproduced video signal sb is supplied to the de-emphasis circuit 28 and is made to have the same frequency-level characteristics as the original video signal. Here, limiter 2G, demodulation circuit 2
7 and the de-emphasis circuit 28 together constitute a demodulator 30 for video signals.

A reproduced video signal sb obtained from the output end of the de-emphasis circuit 28, that is, the output end of the demodulation section 30, is supplied to one input end of a subtraction circuit 38, which will be described later. In addition to this, the reproduced video signal s obtained from the output end of the demodulator 30
b is supplied to the bypass filter 31 in the noise cancellation signal forming section 35, and from the bypass filter 3I, the frequency band component in which the noise components included in the reproduced video signal sb are concentrated is output as the filter output signal Sc. taken out. This filter output signal Sc is also supplied to the limiter 32 in the noise cancellation signal forming section 35, and its level is kept constant. Then, the filter output signal SC obtained from the limiter 32 and having a constant level is supplied to a level adjustment circuit 33 that forms a noise canceling signal forming section 35 together with the bypass filter 3I and the limiter 32, and is adjusted to a predetermined level. In response, the level adjustment circuit 33 sends out the noise cancellation signal Sd. In this noise canceling signal forming section 35, a noise canceling signal Sd to be formed based on the reproduced video signal sb is supplied to an input terminal of a voltage control amplification circuit 36.

On the other hand, the read signal Sa derived from the reading means is also supplied to the envelope detector 40. An output signal having a voltage level corresponding to the envelope of the read signal Sa is obtained from the envelope detector 40 as a control signal De, and this control signal De is supplied to the control end of the voltage-controlled amplifier circuit 36. As a result, the voltage control amplifier circuit 3
6, the level of the noise canceling signal Sd supplied from its input terminal changes according to the level of the control signal De, and the output terminal of the voltage control amplifier circuit 36 changes according to the level of the control signal De. The noise cancellation signal Sd whose level has been corrected is obtained as a corrected noise cancellation signal Sf, and is supplied to the other input terminal of the subtraction circuit 38.

In the subtraction circuit 38, the corrected noise cancel signal Sr is subtracted from the reproduced video No. 13 sb obtained from the output end of the demodulator 30, and the level component corresponding to the corrected noise cancel signal Sf in the reproduced video signal sb is subtracted. Cancellation is performed by the corrected noise cancellation signal Sf. The level component corresponding to the corrected noise cancel signal Sf in the reproduced video signal sb is the corrected noise cancel (g signal Sf), which is generated by the bypass filter 31 described above, where the noise components included in the reproduced video signal sb are concentrated. Since it is formed based on the filter output signal Sc that is obtained by extracting the frequency band component that is the main component, it is mainly a noise component, and therefore, it is a correction noise cancellation signal for the noise component included in the reproduced video signal sb. Then, the subtraction circuit 38 obtains a reproduced video signal sb whose noise component has been canceled by the corrected noise cancellation signal S[, and is output to the output terminal 38a. .

Note that the control signal De obtained from the envelope detector 40 is also supplied to the system control section 100.

Operation of the G-2 embodiment (FIGS. 1, 2, and 4) In the information signal reproducing system having the configuration described above, the disk 10 is rotated at a constant rotational speed. Therefore, each track T formed on the disk 10
The relative speed between the read head 20 scanning the track T and the track T decreases as the position of the read head 20 relative to the disk 10 moves from the outer circumferential side of the disk 10 to the inner circumferential side. For this reason, the reading head 20 is
The level of the read signal Sa obtained from the output end of the reproducing amplification circuit 25, that is, the output end of the reading means, is determined when the position of the read head 20 with respect to the disk 10 is
0 becomes smaller as it moves from the outer circumferential side to the inner circumferential side.

Furthermore, the level of the reproduced video signal sb from the demodulator 30 obtained by demodulating the video signal contained in the read signal Sa and made into a frequency modulated signal is the same as that of the read head 20.
The position with respect to the disk 10 decreases as it moves from the outer circumference side to the inner circumference side of the disk 10.

Therefore, for example, the level of the noise component included in this reproduced video signal sb, which is as shown in FIG. It decreases as it moves to the side, depending on the position of the read head 20 with respect to the disk 10.

As described above, the level of the read signal Sa is determined by the position of the read head 20 relative to the disk 10.
becomes smaller as it moves from the outer circumferential side to the inner circumferential side. Therefore, the control signal De obtained from the envelope detector 40 with a voltage level corresponding to the envelope of the read signal Sa is the same as that of the read head 20. The level decreases as the position relative to the disk 10 moves from the outer circumferential side to the inner circumferential side of the disk 10. That is, the control signal De has a level depending on the position of the read head 20 with respect to the disk 10.

Therefore, the level of the corrected noise cancellation signal Sf, which is obtained from the voltage control amplifier circuit 36 as shown in FIG. 2B and has a level that changes depending on the level of the control signal De, is , read navel)'2
0(7) The position relative to the disk 10 decreases as the position moves from the outer circumferential side to the inner circumferential side of the disk 10, and corresponds to the position of the reading head 20 relative to the disk 10.

In this way, the level of the noise component included in the reproduced video signal sb supplied to the subtraction circuit 38 and the level of the corrected noise cancellation signal Sf are determined when the position of the reading head 20 with respect to the disk 10 is on the outer peripheral side of the disk 10. It decreases as it moves toward the inner circumference, depending on the position of the reading head 20 with respect to the disk 10. Therefore,
Noise cancellation signal Sd in level adjustment circuit 33
The subtraction circuit 3
8, the cancellation of the noise component as shown in FIG. 2A included in the reproduced video signal sb by the corrected noise cancellation signal Sf as shown in FIG. However, the noise component contained in the reproduced information signal sb is appropriately removed or reduced as shown in FIG. 2C. As a result, the reproduced video signal sb obtained at the output terminal 38a has noise components included in it.
It is assumed that the S/N ratio is significantly reduced regardless of the position of the reading head 20 relative to the disk 10, and the S/N ratio is shown in a chain 'f!' in FIG. As shown by Aq, the decrease in the position of the reading head 20 relative to the disk 10 as it moves from the outer circumferential side to the inner circumferential side of the disk 10 is made small. That is, even when the reading head 20 is located on the inner peripheral side of the disk 10, for example, a reproduced video signal sb with an improved S/N ratio can be obtained at the output terminal 38a.

Note that the control signal De supplied to the system control unit 100 is used for various controls as a position information signal indicating the position of the reading head 20 with respect to the disk 10.

G-3 Modification (FIG. 3) In the above example, a control signal De is obtained from the envelope detector 40 and has a level depending on the position of the read head 20 with respect to the disk 10, and the voltage controlled amplifier circuit 36, but by using other means instead of the envelope detector 40, a control signal De having a level depending on the position of the read head 20 with respect to the disk 10 can be obtained. It can be done.

FIG. 3 shows a main part of an example in which other means are used instead of the envelope detector 40. In this example, the envelope detector 40 is replaced with an address data decoding circuit 41 and a control signal generation circuit. 42 are provided. The address data decoding circuit 41 is supplied with the read signal Sa from the reading means, and the address data decoding circuit 4 decodes the address decoding which indicates the track address in the read signal Sa. Then, an output signal sy corresponding to the track address corresponding to the position of the reading head 20 on the disk IO is obtained from the address data decoding circuit 41 and is supplied to the control signal generating circuit 42. The control signal generation circuit 42 generates a signal having a voltage level corresponding to the track address corresponding to the output signal Sy, that is, a voltage level corresponding to the position of the read head 20 on the disk 10. This is sent out as a control signal De and supplied to the control terminal of the voltage control amplifier circuit 36.

In this case as well, similarly to the example shown in FIG. 1, a corrected noise cancellation signal Sr having a level corresponding to the position of the read head 20 with respect to the disk 10 is obtained from the voltage control amplifier circuit 36, and as a result, The reproduced video signal Sd obtained at the output terminal 38a is not affected by the position of the reading head 20 relative to the disk 10, and the S/N ratio is improved.

H Effects of the Invention As is clear from the above explanation, the information signal processing circuit according to the present invention provides a disk-shaped recording medium in which information signals are recorded with concentric or spiral trunks and is rotated at a constant rotational speed. A reproduction information signal is obtained from a read signal from a reading means including a reading head section arranged to scan a track, and when noise canceling processing is performed on the obtained reproduction information signal, the reproduction information signal is Both the level of the noise component included in the reproduced information signal and the level of a correction noise cancellation signal for canceling the noise component included in the reproduced information signal are changed as the position of the read head section relative to the disk-shaped recording medium changes. As a result, the noise components contained in the reproduced information signal can be canceled by the correction noise cancellation signal depending on the position of the reading head relative to the disk-shaped recording medium. can be appropriately removed or reduced.

As a result, regardless of the position of the reading head with respect to the disk-shaped recording medium, for example, even when the reading head is located on the inner circumferential side of the disk-shaped recording medium, S,
/ It is possible to obtain a reproduced information signal with an excellent N ratio.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an information signal processing circuit according to the present invention together with the main parts of an information signal reproduction system to which the circuit is applied, and FIG. 2 is a block diagram for explaining the operation of the example shown in FIG. 1. FIG. 3 is a block configuration diagram showing a main part of a modified example of the example shown in FIG. 1, and FIG. FIG. In the figure, 10 is a disk, 20 is a reading head, 25 is a reproducing amplifier circuit, 30 is a demodulating section, 35 is a noise canceling signal forming section, 36 is a voltage control amplifier circuit, 38 is a subtracting circuit, 4
0 is an envelope detector, 41 is an address data decoding circuit, and 42 is a control signal generating circuit. C Figure 2 Position of reading head

Claims (1)

[Claims] From a reading means including a reading head movably disposed in the radial direction of a disk-shaped recording medium on which information signals are recorded with concentric or spiral tracks and rotated at a constant rotational speed. a demodulation unit that obtains a reproduction information signal based on the read signal; a noise cancellation signal forming unit that obtains a noise cancellation signal based on the reproduction information signal;
a control signal forming section that obtains a control signal according to the position of the reading head section with respect to the disk-shaped recording medium based on the reading signal; and a correction noise canceling section that changes the level of the noise canceling signal according to the control signal. An information signal processing circuit comprising: a signal correction section that obtains a signal; and a subtraction section to which the reproduced information signal and the corrected noise cancellation signal are supplied.