JPS61236034A - Optical disk player - Google Patents

Abstract

PURPOSE:To use obtained reading output for various control by providing a low pass filter that obtains tracking error signals from push pull signal output from a signal forming section and a high pass filter that obtains reading output of signals recorded in a guide groove. CONSTITUTION:Tracking error signals TE in output signals RX are obtained from a low pass filter 49, and after specified processing such as phase compensation etc. is made by a tracking error signal processing circuit 51, supplied to an amplifier circuit 52. A driving signal TD for tracking adjusting is obtained from the amplifier circuit 52 and supplied to a driving coil 27 for tracking adjusting and tracking servo control is performed. On the other hand, reading output CL of clock signal in output signals RX is obtained from a low pass filter 50 separately from the tracking error signals TE. Obtained reading output can be used for various control such as time axis control of information signals written in a discoid recording medium or read out information signals.

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 Optical system and attached disk (second (Figures to Figures 8) G-2 Circuit system (Figure 1) G-3 Modification H Effect of the invention A Industrial field of application The present invention provides a disk-shaped circuit with a spiral guide groove surrounding the central part. The present invention relates to an optical disc player that records or reproduces information signals by making a light beam enter a recording medium.

B. Summary of the Invention The present invention provides an optical disc player that is equipped with a disc-shaped recording medium provided with a spiral guide groove surrounding the center, and records or reproduces information signals by making a light beam incident on the disc-shaped recording medium. A light beam designed to scan the spiral guide groove is incident on the disk-shaped recording medium, and the light beam coming from the disk-shaped recording medium is detected by a pair of adjacently arranged photodetecting means. detect,
By forming a push-pull signal based on the difference between the respective outputs of these pair of photodetecting means and supplying it to the bypass filter, recording is recorded in the spiral guide groove of the disk-shaped recording medium on the output side of the bypass filter. The read output of a signal having a frequency belonging to a frequency band higher than the predetermined frequency band that has been detected can be obtained separately from the tracking error signal obtained as having a frequency belonging to the predetermined frequency band. It is.

C. Conventional technology Among discs used as information recording media, there are so-called writable discs, in which information signals can be recorded using a light beam even after the disc has been formed. There is. In such a writable disk, a spiral guide groove surrounding the center hole is usually provided in advance around the center hole on the surface of the base body. When the writable disk is rotated around the central hole and a light beam is made incident on the guide groove to write an information signal or read an information signal that has already been written, the light beam is inserted into the guide groove. shall be used to obtain a tracking error signal required in a tracking servo control system formed to appropriately follow a recording track on which an information signal is to be written or on which an information signal has been written. , and further includes address information indicating the position on the disk in relation to the recording track. Note that the recording track corresponds to the bottom of the guide groove or two adjacent spiral guide grooves.
It is formed correspondingly between the two.

In such a writable disk that has a spiral guide groove formed in advance on the surface of the base, a predetermined clock signal is recorded in the guide groove, and as the disk is rotated, a light beam is made incident on it to read information. writing a signal,
Alternatively, when an information signal that has already been written is to be read, that is, the disc is mounted on an optical disc player, and a light beam from the optical head is made incident on the disc to write or read the information signal. Alternatively, if the clock signal can be easily read from the guide groove by the light beam from the optical head during playback, the clock signal obtained from the guide groove may be used to drive the disc player during recording or playback. The information signal written on the recording track, or the optical head moving mechanism that moves the incident position of the optical beam in the radial direction of the disk so that the optical beam incident on the disk follows the recording trunk. Therefore, the time axis of the information signal read from the recording track can be properly controlled, and the configuration of the disk rotation mechanism, the optical head feeding mechanism, etc. can be simplified and the mechanical accuracy can be improved.

In this way, the information signal written to the recording track by the clock signal read from the disk, or
Control to make the time axis of the information signal read from the recording trunk appropriate, that is, so-called self-clocking, is important when miniaturizing the disk or improving the time axis of the information signal on the disk. This is especially desirable when a fixed-line distance method is adopted in which the relative speed between the recording track and the light beam scanning it is constant regardless of the position on the disk, in order to increase the writing density. Become. When discs are made smaller, the mechanical accuracy of the disc rotation mechanism, optical head feeding mechanism, etc. provided in the disc player tends to decrease, and when a constant linear speed method is adopted, the disc rotation This is because a quick response is required in controlling the mechanism, optical head feeding mechanism, etc.

Furthermore, in a writable disc, a specific information signal is recorded in a guide groove provided in advance, and this does not adversely affect the information signal written to or read from the recording track. If the information can be easily read during recording or reproduction, not only can the amount of information recorded and reproduced using the disk be increased, but also the specific information read can be easily read. By using the information signal, it is possible to enrich the recording and reproduction modes of the information signal using the disk.

D. Problems to be Solved by the Invention However, in the past, a writable disk on which a clock signal or a specific information signal was recorded in a spiral guide groove provided in advance was prepared, and this was optically recorded. When installed in a disc player and used for writing or reading information signals, the signals recorded in the spiral guide groove do not adversely affect the information signals written to the recording trunk or the information signals read from the recording tracks. No disc player system has been found that can be easily read by an optical disc player. Therefore, conventional optical disc players do not enjoy the benefits that would be available if they were made capable of self-clocking.

In view of the above, the present invention provides a disk-shaped recording medium in which a signal having a frequency belonging to a frequency band higher than a predetermined frequency band is recorded in a spirally formed guide groove, and a light beam is incident on the disk-shaped recording medium. At least when writing or reading information signals, it is possible to read and output signals recorded in a spiral guide groove using a relatively simple configuration.
It does not adversely affect the information signal being written or being read, and it also provides the tracking and servo control system that is required for tracking and servo control systems.
An optical disc player that can obtain a read output separately from an error signal and use the obtained read output for various controls such as controlling the time axis of an information signal to be written or an information signal to be read. The purpose is to provide

E. Means for Solving the Problems In order to achieve the above-mentioned object, the optical disc player according to the present invention has a spiral guide groove surrounding the center portion having a frequency belonging to a frequency band higher than a predetermined frequency band. an optical means for causing a light beam to scan the guide groove to be incident on the disk-shaped recording medium on which a signal has been recorded; and a pair of adjacently arranged optical means for scanning the guide groove and detecting the light beam arriving from the disk-shaped recording medium. A photodetecting means, a signal forming section that generates a push-pull signal output based on the difference between the respective outputs of the pair of photodetecting means, and a signal forming section with a frequency band below the above-mentioned predetermined frequency band as a passband. a low-pass filter to which the push-pull signal output from the signal forming section is supplied and from which a tracking error signal is obtained; and a bypass filter for obtaining a readout output of the signal recorded in the groove.

F-effect In the optical disc player according to the present invention as described above, a signal having a frequency belonging to a frequency band higher than a predetermined frequency band recorded in a spiral guide groove provided in a disc-shaped recording medium is read. The output is a light beam that is made incident on a disc-shaped recording medium by an optical means and scans a guide groove. After passing through the guide groove, the light beam is detected by a pair of light detection means, and a push-pull signal is generated in a signal forming section in response to the light beam. During the output, a tracking error signal is obtained which will have frequencies belonging to a predetermined frequency band. The read output and tracking error signal of the signals recorded in the spiral guide grooves provided on these disk-shaped recording media are respectively derived from a bypass filter and a low-pass filter to which push-pull signals are supplied.

In this way, the reading output and tracking of the signals recorded in the spiral guide groove provided on the disk-shaped recording medium are performed.
The push-pull signal, which includes an error signal, is generated in a signal forming section separately from the information signal written to or read from the disk-shaped recording medium. The reading output of the signal recorded in the spiral guide groove provided on the recording medium (without any adverse effect on the information signal written to the disk-shaped recording medium or the information signal read from the disk-shaped recording medium, and tracking)・It can be obtained with a relatively simple configuration in which a bypass filter and a low-pass filter are provided on the output side of a signal forming section that generates a push-pull signal and is distinguished from an error signal. Become.

G Example G-1 Optical System and Mounted Disc (FIGS. 2 to 8) FIG. 2 shows the main parts, mainly the optical system, in an example of the optical disc player according to the present invention.

In this example, a writable disc D is mounted on a disc mounting section 21 that rotates at a predetermined rotational speed. As shown in FIG. 3, this disc D is provided with a central hole 1 and a recording section 3 extending around it.
Furthermore, a label section 5 is arranged between the center hole 1 and the recording section 3. In the recording section 3, an annular inner edge area 7 is provided on the inner circumference side, that is, on the boundary side with the label section 5, and an annular outer edge area 9 is provided on the outer circumference side. And these inner edges 8! A light beam is made incident between the area 7 and the outer edge area 9 to form an area where an information signal is written and where the written information signal is read, that is, an information signal recording track is formed. This is the recording track area 11 where the recording track area 11 is recorded.

In the recording track area 11, spiral guide grooves 13 surrounding the central hole 1 are provided at a predetermined pitch. This spiral guide groove 13 is formed with a certain depth and a certain groove width on the surface of the base body, and is used during recording when an information signal is written to the recording track area 11 or from the recording track area 11. During reproduction when information signals are read, the optical beam is scanned, and a spiral recording track is formed along a portion corresponding to the bottom of the optical beam.

The spiral guide groove 13 in the disk D is formed, for example, on the surface of the base 14, as shown in FIG. 4, so that each circumference of the spiral meanders with a minute amplitude. In this example of the guide groove 13, the depth t and the groove width W
is assumed to be constant, and the opposing edge is assumed to meander by reciprocating in the groove width direction with a minute amplitude. As shown in Fig. 5, the groove width W, pitch P, and meandering of the opposing edge are The dimensional relationship of the maximum amplitude Q is, for example, that the pitch P is the groove width W
It is selected such that the maximum amplitude Q of the meandering of the opposing edges is between 5 and 25 percent of the pitch P. This prevents the information signal written to the recording track or the information signal read from the recording track from being adversely affected by the meandering of the opposing edges of the guide groove 13.

The meandering of the opposing edges of the guide groove 13 with the maximum amplitude Q is in response to a predetermined signal, for example, a clock signal having a predetermined frequency, and the meandering period corresponds to the period of the clock signal. has been done. The frequency of this clock signal is selected to belong to a frequency band higher than the servo control frequency band in the tracking servo control system that is formed when the guide groove 13 is scanned by a light beam during recording or reproduction. There is. Therefore, in this example of the guide groove 13, a clock signal having a frequency belonging to a frequency band higher than a servo control frequency band in a tracking servo control system formed when being scanned by a light beam is applied to the maximum of the opposite edge. This means that it is written in a meandering form with an amplitude Q. Furthermore, the depth t of the guide groove I3 is selected to be, for example, 178 wavelengths of the reading light beam.

Further, the spiral guide groove 13 on the disk D not only has a meandering shape, but also has a constant depth t and groove width W on the surface of the base body 14, as shown in FIG. It is also assumed that the opposing edges are reciprocally displaced parallel to each other in the groove width direction with minute amplitudes to form repeated concavities and convexities. In the example of such a guide groove 13, as shown in FIG. It is selected so that the maximum amplitude Q' of the repetition of the unevenness on the opposing edge is 5 to 25 percent of the pitch P. The repetition period of the unevenness with the maximum amplitude Q'' on the opposing edge of the guide groove 13 corresponds to the period of a predetermined clock signal, and the frequency of this clock signal is set at the time of recording or reproduction. The guide groove 1 is selected to belong to a higher frequency band than the servo control frequency band in the tracking servo control system that is formed when the guide i1 $13 is scanned by a light beam.Therefore, the guide groove 1 shown in FIG.
In example 3, a clock signal having a frequency belonging to a frequency band higher than a servo control frequency band in a tracking servo control system formed when being scanned by a light beam has a maximum amplitude Q'' at the opposite edge. In this case, the depth t of the guide groove 13 is selected to be, for example, 1/8 of the wavelength of the reading light beam.

The disk D having the base body 14 provided with the guide grooves 13 as shown in FIG. 4 or FIG. A thin recording material layer 15 directly involved in writing information signals is provided on the surface, and a protective layer 17 is further provided on the recording material layer 15. The recording material layer 15 is provided along the guide grooves 13 formed in the base 14 and the portion between the guide grooves 13, and therefore the recording material layer 1
5 also forms a groove corresponding to the guide groove 13, and an information signal is written at the bottom of the groove. Further, the protective layer 17 is provided to fill the grooves of the recording material layer 15 and has a flat outer surface. In this case, the recording material layer 15 is, for example, a perpendicular magnetization film, and when a light beam such as a laser beam is irradiated under the action of a predetermined magnetic field, the portion irradiated with the light beam is Magnetization reversal occurs as the temperature rises, and so-called magneto-optical recording is performed.

In the disk D having such a configuration, the base 1
The guide groove 13 is scanned by a light beam incident from the 4 side, and the light beam that has scanned the guide groove 13 is reflected at the interface between the base 14 and the recording material layer 15 corresponding to the bottom of the guide groove 13. be done.

An optical system is arranged to allow a light beam that scans the guide groove 13 to be incident on the disk D, and to detect a light beam that is reflected back from the disk D. In this optical system, a laser beam from a laser light source 22 passes through a collimator lens 23 to a half mirror 24.
Enter and pass through this. The laser beam that has passed through the half mirror 24 enters the objective lens 25, is focused by the objective lens 25, and is made incident on the disk D to scan the spiral guide groove 13 provided therein. The objective lens 25 has a drive coil 26 for focus adjustment.
and the tracking adjustment drive coil 27, for example, move the laser beam in a direction approaching or away from the disk D, and in a direction in which the laser beam incident on the disk D crosses the guide groove 13 provided in the disk D. As a result, the laser beam incident on the disk D is positioned in the guide groove 13 provided on the disk D in an appropriate tracking relationship under an appropriate focus state. to form a spot.

The laser beam incident on the disk D changes in intensity at the bottom position of the guide groove 13 depending on the state of following the guide groove 13 and the repeated meandering or unevenness at the opposite edge of the guide groove 13, and , the state of polarization changes according to the state of magnetization reversal of the recording material layer 15 at the bottom of the guide groove 13, that is, the recording state of the information signal on the recording material layer 15, and is reflected, enters the objective lens 25 again, and enters the objective lens 25. The light is then reflected by the half mirror 24 to the right in the figure.

A portion of the laser beam reflected to the right by the half mirror 24 passes through the half mirror 28 and further reaches the photosensitive section 30 via the cylindrical lens 29.
The deviation of the laser beam incident on the disk D from the proper focus state in the position of the guide groove 13 provided on the disk D, that is, the focus error and the guide groove 13
Detection of deviation from, that is, tracking error,
It is also used for reproducing a clock signal recorded in the guide groove 13 in the form of a meandering or repeated unevenness on the opposite edge thereof. The photodetector constituting the photosensitive section 30 is
Upon receiving the laser beam that has passed through the cylindrical lens 29, an electric signal is generated in accordance with the changes in the laser beam.

Further, a portion of the laser beam reflected to the right by the half mirror 24 is reflected downward in the figure by the half mirror 28, and further divided into two by the half mirror 31. Each of these two divided laser beams is divided into two depending on the state of magnetization reversal of the recording material layer 15 at the bottom of the guide groove 13 provided on the disk D, that is,
The recording material layer 15 contains components reflected with different polarization planes depending on the recorded portion and the non-recorded portion of the information signal, and after one of them passes through the analyzer 32,
The light reaches the photosensitive section 34 via the lens 33 , the other side is reflected by the mirror 35 to the right in the figure, passes through the analyzer 36 , and then reaches the photosensitive section 38 via the lens 37 . Analyzer 3
2 and 36, the direction in which the transmittance is maximum is relative to the polarization plane of the component from the non-recorded portion of the information signal in the recording material layer 15 in each of the laser beams divided into two by the half mirror 31. The analyzers 32 and 36 are set to be in the positive direction and the negative direction.
At the point when the laser beam passing through each of the recording material layers 15 includes a component from the recording portion of the information signal, the amount of light incident on one of the photosensitive sections 34 and 38 becomes larger than the amount of light incident on the other. , when the information signal in the recording material layer 15 includes components from the non-recorded portion, on the contrary,
The amount of light incident on the other of the photosensitive sections 34 and 38 becomes larger than the amount of light incident on one of the photosensitive sections 34 and 38, and the photodetectors forming the photosensitive sections 34 and 38 generate electrical signals in response to this change in the amount of light.

The optical system configured in this way is entirely driven by a feed drive means (not shown), and is moved in the radial direction of the disk D as the disk D rotates, thereby moving the objective The laser beam incident on the disk D through the lens 25 follows and scans the spiral guide groove 13 of the rotating disk D.

Output signals from each of the photosensitive sections 30, 34 and 38 described above are used for focus servo control for focus adjustment with respect to the laser beam incident on the disk D and trunking control for tracking adjustment.
Respective servo control circuits for servo control, circuits for reading and outputting information signals recorded on the recording material layer 15 of the disk D, and reading and outputting clock signals recorded in the guide grooves 13 provided on the disk D. The drive signal is supplied to a signal processing circuit section 39 including a circuit for obtaining the same, and within the signal processing circuit section 39, a drive signal for controlling the position of the objective lens 25 for focus servo control and tracking servo control is formed. In addition to being supplied to the drive coil for focus adjustment 26 and the drive coil for tracking adjustment 27, from the signal processing circuit section 39, the read output of the information signal recorded on the recording material layer 15 of the disc D and the guide provided on the disc D are output. A read output of the clock signal recorded in the groove 13 is obtained.

G-2 circuit system (Fig. 1) Fig. 1 shows each photodetector constituting the photosensitive sections 30, 34 and 38 in an example of the optical disc player according to the present invention whose main parts are shown in Fig. 2. , and signal processing circuit section 3
9 shows a circuit system including each circuit block forming part 9.

Here, the photosensitive section 30 described above has four photodetectors 30 a
, 30b, 30c and 30d,
Further, the photosensitive sections 34 and 38 are photodetectors 34a and 38, respectively.
It consists of 8a. These photodetectors 30a to 30d forming the photosensitive section 30, the photodetector 34a forming the photosensitive section 34, and the photodetector 38a forming the photosensitive section 38 are as follows:
Cylindrical lens 29. The four photodetectors 30a to 30 forming the photosensitive section 30 are arranged at positions to detect the laser beam from the guide groove 13 provided in the disk D through the lens 33 and the lens 37.
d is the amount of light incident on the pair of photodetectors 30a and 30b and the amount of light incident on the pair of photodetectors 30c and 30d when the incident position of the laser beam on the disk D is shifted from the center of the guide groove 13 in the groove width direction. are set so that one increases and the other decreases.

Output signals Ra and Rc of the photodetectors 30a and 30c, which are two of the four photodetectors 30a to 30d forming the photosensitive section 30, are supplied to an adder circuit 41 to obtain a sum output signal Ra+Rc. Furthermore, the output signals Rb and Rd of the remaining two photodetectors 30b and 30d are supplied to the adder circuit 42 to obtain the sum output signal Rh+Rd. Then, the subtraction circuit 43 calculates the difference between the sum output signal Ra+Rc and the sum output signal Rb+Rd.
A guide groove 13 for the laser beam that enters the disk D from the
A focus error signal FE is obtained which varies depending on the focus state at the bottom position of the image sensor. The focus error signal FE obtained in this manner is supplied to an amplifier circuit 45 after being subjected to predetermined processing such as phase compensation in a focus error signal processing circuit 44 that constitutes a servo control circuit for focus servo control. ,
A focus adjustment drive signal FD is obtained from the amplifier circuit 45 and supplied to the focus adjustment drive coil 26 to perform focus servo control.

On the other hand, four photodetectors 30a to 3 forming the photosensitive section 30
The output signals Ra and Rb of the set of photodetectors 30a and 30b of 0d are supplied to an adder circuit 46 to obtain a sum output signal Ra+Rb, and the output signals Ra and Rb of the photodetectors 30c and 30b are
d sets of output signals RC and Rd are supplied to an adder circuit 47 to obtain a sum output signal Rc+Rd. Then, in the subtraction circuit 48, the sum output signal Ra+Rb and the sum output signal R
c+Rd, and a tracking error signal TE indicating the tracking state of the laser beam incident on the disk D with respect to the guide groove 13 is output from the subtraction circuit 48.
An output signal RX containing a signal corresponding to meandering or repetition of irregularities on the opposing edges of the guide groove 13, that is, a read output CL of the clock signal recorded in the guide groove 13, is obtained as a bush pull signal. In this case, as described above, the frequency of the clock signal recorded in the guide groove 13 of the disk D is higher than the servo control frequency band in the tracking servo control system formed when the guide groove 13 is scanned by the light beam. Since it is selected as belonging to the frequency band, the subtraction circuit 4 is selected as described above.
The read output CL of the clock signal included in the output signal RX, which is a push-pull signal obtained from 8, has a frequency that belongs to a higher frequency band than the frequency band of the tracking error signal TE, which is included in the output signal RX, which is also a push-pull signal. It will have the following.

The output signal RX as a bush-pull signal obtained from the subtraction circuit 48 is filtered by a low-pass filter 49 whose passband is a frequency band corresponding to the frequency band of the tracking error signal TE and a frequency band higher than the frequency band of the tracking error signal TE. The signal is supplied to a bypass filter 50 which serves as a pass band. Then, a tracking error signal TE in the output signal RX is obtained from the low-pass filter 49, and this signal is used for predetermined processing such as phase compensation in a tracking/miller signal processing circuit 51 that constitutes a servo control circuit for tracking/servo control. After processing, the signal is supplied to the amplifier circuit 52, from which a tracking adjustment drive signal TD is obtained and supplied to the tracking adjustment drive coil 27, where tracking servo control is performed.

On the other hand, a read output CL of the clock signal in the output signal RX is obtained from the low-pass filter 50 separately from the tracking error signal TE. The reading output CL of the clock signal recorded in the guide groove 13 of the disk D obtained in this way is used to control the rotation of the disk mounting section 21 that rotates the disk D, and to rotate the laser beam incident on the disk D. The entire optical system shown in FIG. 1, including the objective lens 25, is attached to the disk D in order to perform follow-up scanning for the spiral guide groove 13 of the disk D.
It can be used for drive control of the feed drive means for moving the disk D in the radial direction as the disk rotates, and self-clocking can be performed.

Furthermore, the output signal Rp of the photodetector 34a constituting the photosensitive section 34 and the output signal Rs of the photodetector 38a constituting the photosensitive section 38 are supplied to the differential circuit 55 via amplifier circuits 53 and 54, respectively, A reading output RF of the information signal recorded on the recording material layer 15 at the bottom position of the guide groove 13 of the disk D is obtained from the differential circuit 55. The reading output RF of such information signal is passed through the above-mentioned bypass filter 50.
The readout output CL of the clock signal recorded in the guide groove 13 of the disk D obtained from the disk loading section 2
1, and the entire optical system is controlled by the disk D.
The time axis can be properly controlled by controlling the drive means for moving the disk D in the radial direction as the disk D rotates. Then, the read output RF of the information signal obtained from the differential circuit 55 is supplied to the read information signal processing circuit 56 to undergo necessary processing, and the read information signal processing circuit 56 outputs the reproduced information signal Sl.
is derived.

G-3 Modification The above-described example of the optical disc player according to the present invention obtains a reading output of the clock signal recorded in the spiral guide groove 13 provided on the mounted disc D, and Although it is assumed that the information signal recorded on the recording material layer 15 at the bottom position of the shaped guide groove 13 is reproduced, the optical disc player according to the present invention is not limited to this. is attached, and in the same manner as in the above example, the clock signal recorded in the spiral guide groove 13 of the disk D is read out, and the recording material layer 15 at the bottom position of the guide groove 13 is read out.
By applying a predetermined magnetic field to the recording material layer 15 at the bottom of the guide groove 13, a laser beam modulated by an information signal is made to enter the recording material layer 15 at the bottom of the guide groove 13.
The information signal may be written to the .

Further, the disc D mounted on the above-described example of the optical disc player according to the present invention has a spiral guide groove 13.
It is assumed that a clock signal is written in the optical disc player according to the present invention, and a reading output of the clock signal is obtained from the bypass filter 50 in an example of the optical disc player according to the present invention. In a disc that can be mounted in a disc player, the signals written in the spiral guide groove are not limited to clock signals, and various information signals other than clock signals may be written therein.

Effects of the Invention H As is clear from the above explanation, according to the optical disc player of the present invention, a signal having a frequency belonging to a frequency band higher than a predetermined frequency band is recorded in the spirally formed guide groove. A disc-shaped recording medium is installed,
When writing or reading an information signal by inputting a light beam to the light beam, a spiral guide groove is scanned by the light beam, and a push-pull signal forming section and a bypass filter are used. Under the
A tracking servo control system that allows a light beam to scan a spiral guide groove without adversely affecting the information signal being written or the information signal being read. The tracking error signal can be obtained separately from the tracking error signal required in the following. The obtained read output can be used for various controls such as controlling the time axis of information signals written to or read from the disk-shaped recording medium.

[Brief explanation of the drawing]

FIG. 1 is a block connection diagram showing the configuration of main parts of an example of an optical disc player according to the present invention, and FIG. 2 shows main parts mainly including an optical system in an example of an optical disc player according to the invention. A schematic configuration diagram, FIG. 3 is a plan view showing a disk mounted on an example of an optical disk player according to the present invention, and FIGS. 4 and 5 are examples of guide grooves provided in the disk shown in FIG. 3. FIG. 6 and FIG. 7 are diagrams for explaining other examples of guide grooves provided in the disk shown in FIG. 3, and FIG. 8 is an optical type according to the present invention. FIG. 2 is a partial cross-sectional view of a disc mounted on an example of a disc player. In the figure, D is a disk, 13 is a guide groove, 14 is a base, 22
is a laser light source, 25 is an objective lens, 30.34 and 38
39 is a photosensitive section, 39 is a signal processing circuit section, 30a to 30d are photodetectors, 46 and 47 are addition circuits, 48 is a subtraction circuit, 4
9 is a low-pass filter, and 50 is a bypass filter. Figure 6 Figure 7 Cross-sectional view of the disk Figure 8

Claims (1)

[Scope of Claims] A disc-shaped recording medium is provided with a spiral guide groove surrounding a central portion, and a signal having a frequency belonging to a frequency band higher than a predetermined frequency band is recorded in the guide groove. an optical means for making a scanning light beam incident thereon; and a pair of adjacently arranged light detection means for detecting a light beam that enters the disk-shaped recording medium and comes from the disk-shaped recording medium to scan the guide groove. , a signal forming unit that generates an output signal based on the difference between the respective outputs of the pair of photodetecting means; a frequency band below the predetermined frequency band is defined as a pass band, and the output signal from the signal forming unit is supplied. a low-pass filter for obtaining a tracking error signal indicating a tracking state of the light beam incident on the disk-shaped recording medium with respect to the guide groove from the output signal; 1. An optical disc player comprising: a bypass filter to which an output signal from the forming section is supplied and obtains a reading output of the signal recorded in the guide groove from the output signal.