JPH09147378A - Information reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform information reproducing to both tracks of a land/a groove by providing focus control means of tracks of the land/the groove, the reflectivity detecting means of a light beam and the discrimination means of tracks irradiated with a laser beam. SOLUTION: There are a land track 2 and a groove track on a magneto- optical disk 1 and information are recorded on both tracks. At the time of reproducing information, a focus leading in control is performed by processing a focusing error signal FE in a servo controller 10 and by driving a focus actuator 13. A system controller 20 performs a tracking leading in control corresponding to the land/the groove by discriminating the track of the land/the groove from the tracking error TE on which the light beams is focused and the reflectivity of the light beam. The phase pit signal PPS and the reproduced signal of a magneto-optical signal MOS are transmitted from a reproducing head 4 to a host computer 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reproducing apparatus for reproducing information recorded on an information recording medium such as an optical disc.

[0002]

2. Description of the Related Art As an example of a conventional information reproducing apparatus, there is a reproducing apparatus for a compact disk (CD). Figure 9 is a CD
FIG. 3 is a diagram showing the configuration of FIG. As shown in FIG. 9, the CD is a relief-shaped phase pit array 8 on a transparent substrate 81 having a thickness of 1.2 mm.
2 is formed in a spiral shape. This is the information track. The audio information is recorded by associating the audio information with the length of the phase pit.

When reproducing information recorded on a CD, the CD is first rotated. Then, a light spot having a radius slightly larger than the phase pit is formed on the information track by the light beam emitted from the reproducing head.
Then, information is reproduced by detecting the diffraction state of the reflected light of the light spot irradiated on the information track.

When there is no phase pit at the position of the light spot, all the reflected light from the information track returns to the reproducing head. Therefore, the information detector built into the playback head
Detect large values. If there is a phase pit at the position of the light spot, the reflected light from the information track is diffracted by the phase pit. Therefore, a part of the reflected light is reflected to the outside of the reproducing head and does not return to the reproducing head. The remaining part of the reflected light returns to the reproducing head. That is, when there is a phase pit at the position of the light spot, the information detector built in the reproducing head detects a small value.

Generally, the radius of a light beam from a reproducing head can be reduced to the diffraction limit. Therefore, if an information reproducing head having a built-in laser light source with a wavelength of 830 nm is used, the radius of the light spot irradiated on the information track can be narrowed down to 1 μm or less. Therefore, the pitch of the information tracks can be 1.6 μm, and a large amount of information can be recorded.

Examples of other information reproducing devices include a magneto-optical disk device and a phase change disk device. The playback principle of these devices is the same as that of the CD playback device except that the Kerr rotation effect and the reflectance change effect of the reflected light from the medium are used, and therefore detailed description is omitted.

[0007]

However, the potential demand for recording more information on the information recording medium is extremely high. The inventor has made many studies to meet this demand. In general, it has been proposed to reduce the reproducing beam diameter by shortening the wavelength of the light source of the reproducing head and to reduce the track pitch.

However, the wavelength of the light source of the reproducing head is limited, and it is impossible to reduce the wavelength indefinitely.
On the other hand, if the size of the reproduction beam is fixed and the track is narrowed, a light spot by the reproduction beam is also irradiated on the information pit of the adjacent track. As a result, there arises a problem that information of an adjacent track is read in addition to information other than the target reproduction track.

Therefore, there is a need for an information reproducing apparatus capable of suppressing information reading from an adjacent track and reproducing only information from a target track. As a result of many studies, a land / groove reproduction method has been found as a measure for suppressing such information reading from an adjacent track. Generally, tracks on a recording medium such as a magneto-optical disk are
It is formed by concentric or spiral grooves.
Therefore, a convex portion and a concave portion exist on the recording surface. In a conventional recording medium, either one of a convex portion and a concave portion is information. On the other hand, in the land / groove reproduction method,
A disc in which information is recorded on both the convex portions (lands) and the concave portions (grooves) is used.

This system is an extremely excellent system in which the track pitch can be reduced to about half. The effect of suppressing information reading from adjacent tracks by the land / groove reproduction method has been described in the following literature, and therefore detailed description is omitted here. The technology related to phase change disks
It is described in "High Density Phase Change Disk by Land & Groove Recording (5th Phase Change Recording Research Group Symposium Proceedings)". The technology related to magneto-optical disks is described in "CROSSTALK ANALYSIS OF LAND / GROOVE MAGNE
T-OPTICAL RECODING (SYMPOSIUM ON OPTICAL MEMORY 199
4) ”.

Although not yet published at the time of filing of the present application, Japanese Patent Application Nos. 6190695, 6-215137 and 6-215138 (all filed by the applicant) The effect of suppressing the information read from the adjacent track in the groove reproduction system is described. However, in the land / groove reproduction method, since there are two types of information tracks, a land track and a groove track, information of an arbitrary track cannot be freely reproduced by the conventional technique.

For example, when reproducing information from a recording medium, the information recorded on the information track is sequentially reproduced by moving the light spot relatively on the information track. Specifically, in the reproduction of a CD, the irradiation position of the light spot is controlled while the disc is rotated, so that the light spot is always on the information track. Such control is called tracking control.

[0013] The tracking control mechanism in the conventional device can cope only with tracking of either the land track or the groove track. This is because the land track and the groove track have different tracking characteristics, and therefore, if the tracking control is performed according to the characteristics of one track, the tracking control of the other track is not suitable.

The present invention has been made in consideration of the above problems, and it is an object of the present invention to provide an information recording medium reproducing apparatus capable of arbitrarily reproducing information from both land and groove tracks. And

[0015]

Means for Solving the Problems To solve the above problems,
According to the present invention, the first group of information tracks on which information is recorded and the second group of information tracks exist concentrically or spirally, and the first group of tracks and the second group of tracks are arranged in a radial direction. An information reproducing apparatus for reproducing recorded information by irradiating each of the tracks with a laser beam for an information recording medium having a disk shape which is alternately stepped, Focus control means for converging the laser light on the track surface, detection means for detecting the reflectance of the surface irradiated with the laser light, and a track irradiated with the laser light from the detection result of the detection means , And a determination means for determining whether the track is the first group track or the second group track.

Further, according to the present invention, the information tracks of the first group and the information tracks of the second group in which information is recorded exist concentrically or spirally, and the tracks of the first group and the second group. A track is an information reproducing apparatus which reproduces recorded information by irradiating each track with a laser beam on a disc-shaped information recording medium which has steps alternately arranged in a radial direction. Focus control means for converging the laser light on the track surface of the recording medium, detecting means for detecting the reflectance of the surface irradiated with the laser light, and irradiation position of the laser light for the first group of tracks. Alternatively, the tracking control means for causing the tracks of the second group to follow and the control conditions in the tracking control means are set to the first group. Setting means for setting the tracking control condition for the track of the group or the tracking control condition for the track of the second group, and the track irradiated with the laser beam is the first group based on the detection result of the detection means. And a second group of tracks, and a determination means for setting the control condition according to the determination result.

The setting of the tracking control condition by the setting means may be a setting for switching the polarity of a track error signal used in the tracking control. The detection means may include light receiving means for receiving the reflected light of the laser light from the recording medium surface and outputting a signal according to the amount of received light.

The determination means has a signal generation means for generating a track error signal indicating the amount of deviation between the irradiation position of the laser beam and the track of the first group or the track of the second group. The determination may be made on the basis of the detection result of 1) and the track error signal.

[0019]

FIG. 2 is a diagram showing a track structure of an information recording medium used in an information reproducing apparatus according to one embodiment of the present invention. FIG. 2 shows a configuration of a recording track of a disk-shaped recording medium. The disc-shaped recording medium 1 has a land track 2 and a groove track 3, and the level difference between them is approximately 1 / 7λ. Note that λ is
It is the wavelength of the light beam that illuminates these tracks for playback.

Each track has a phase pit 41
Area where information is recorded by the optical pit 4
2, there is an area where information is recorded. Address information is recorded in an area where information is recorded by the phase pits 41, and information to be recorded (information used by a user) is recorded in an area where information is recorded by the magneto-optical pits 42. ing.

FIG. 3 is a diagram showing a track shape of an information recording medium used in an information reproducing apparatus according to one embodiment of the present invention. On the recording surface of the disc-shaped recording medium 1, land tracks 2 and groove tracks 3 are alternately arranged in the radial direction. Each track is formed in a spiral shape. That is, an uneven double spiral track is formed. The land tracks and the groove tracks may be formed concentrically and formed alternately in the radial direction.

In the case of a spiral track, a land track 2
And the groove track 3 are each formed as one continuous track from the outermost circumference to the outermost circumference, but one round of the track is regarded as one track. FIG.
As shown in (1), each track is composed of address sections 43 and 45 and information recording sections 44 and 46. A continuous pair of an address section and an information recording section is called a sector (for example, a pair of an address section 43 and an information recording section 44). In the track, a plurality of sectors are continuously arranged in the track direction. In the address sections 43 and 45, address information is recorded by phase pits. The information recording unit 4
4 and 46, information used by the user is recorded by magneto-optical pits.

A track address and a sector address are recorded in an address portion of each sector. The track addresses are assigned, for example, in ascending order from the innermost track.
The same track address is recorded in each sector of one track (one track). In this embodiment, the land track has an odd track address,
An even track address is recorded in the groove track.

For example, the track address of the innermost track (land track) is "1", and the track address of the next outer track (groove track) is "1".
2 ”, and thereafter,“ 3 ”,“
Track addresses are assigned such as 4 "," 5 ", etc. By assigning addresses to each track in this way, odd addresses become land tracks and even addresses become groove tracks.

The step between the land track and the groove track is set to a value having an effect of suppressing reading of the adjacent track. This value is slightly different depending on a CD, a magneto-optical disk, a phase change disk, and the like, but is generally about 1/7 wavelength (about 1/7 of the wavelength of the irradiated light beam). That is, when a transparent substrate having a wavelength of the light beam to be irradiated of 830 nm and an index (refractive index) of 1.5 is used, a step difference of 80 nm is preferable.

The property of the information pit is set to a value that has the effect of suppressing reading of the adjacent track. This value is
D, a magneto-optical disk, a phase change disk, and the like, depending on the type of disk. For example, for a CD, it is preferable to set the phase difference to 1/4 wavelength. For a magneto-optical disk, it is preferable to set the complex Kerr rotation angle {k = 0}. That is,
In the case of a magneto-optical disk, a magnetic pit having a Kerr rotation angle θk = 1 ° and a complex Kerr rotation angle {k = 0} may be set as the information pit.

As shown in FIG. 2, in this embodiment, the land track and the groove track have the same width in the disk radial direction. The track pitch is set so that when a reproduction beam is irradiated to the center of a land track, the reproduction beam does not hit an adjacent land track. In this way, even when the reproduction beam is irradiated to the center of the groove track, the reproduction beam is not irradiated to the adjacent groove track.

At this time, the reproduction beam applied to the land track is applied to the adjacent groove track, and the reproduction beam applied to the groove track is applied to the adjacent land track, but it does not matter. That is, when the wavelength of the irradiated light beam is 830 nm and the numerical aperture NA of the objective lens of the optical head is 0.55, the track pitch from the land track to the adjacent groove track may be 800 nm.

FIG. 1 is a diagram showing a configuration of an information reproducing apparatus according to one embodiment of the present invention. Disc-shaped recording medium 1
Is, for example, 1 by a spindle motor (not shown).
It is rotating at 800 rpm. The disc-shaped recording medium 1 has a land track 2 and a groove track 3, and the level difference between them is approximately 1 / 7λ (λ is the wavelength of the light beam to be irradiated). On the surface 203 of the substrate 201, a reflective layer made of a metal (such as aluminum) is formed.

Here, a track having a convex portion as viewed from the light beam irradiation direction is called a land track, and a track having a concave portion is called a groove track. The disk-shaped recording medium 1 is a magneto-optical disk. Information is recorded on the land track 2 and the groove track 3 by magnetic pits and phase pits. The protective film 202 covering the recording surface on which information is recorded is made of a polymer material.

The optical head 4 for reproducing information recorded on the recording medium 1 has the following configuration. The light beam emitted from the semiconductor laser 5 in the optical head 4 passes through the beam splitter 7 and is converged by the objective lens 6 to form a light spot on the track surface of the recording medium 1. The light reflected on the track surface passes through the objective lens 6 again, is reflected on the beam splitter 7, and is incident on a detector (photoelectric converter, for example, a photodiode) 8.

The reflected light is converted into an electric signal by the detector 8 and enters the electric circuit 9. The electric circuit 9 processes the electric signal from the detector 8 and outputs a track error signal (TE), a focus error signal (FE), a phase pit signal (PPS), and a magneto-optical signal (MoS). The track error signal TE is a signal indicating a shift amount between a light spot formed on a track of the disk-shaped recording medium 1 and a center line in a radial direction of the track. The focus error signal FE is a signal indicating a shift amount between the position of the convergence point of the light beam and the track surface. The phase pit signal PPS is a reproduction signal of information recorded by the phase pit on the track. The magneto-optical signal MoS is a reproduction signal of information recorded by magnetic pits on a track.

The track error signal TE and the focus error signal FE are input to the servo controller 10 and subjected to signal processing to be converted into a tracking signal, a positioning signal and a focus signal and output. The tracking signal is a signal for driving the tracking actuator 11. The tracking signal is a signal having a level corresponding to the level of the track error signal TE (the amount of deviation between the light spot and the center line in the radial direction of the track).
The tracking actuator 11 moves the objective lens 6 in the radial direction of the recording medium 1 by an amount corresponding to the level of the tracking signal. This positions the light spot at the center of the track.

The positioning signal is a signal for driving the positioner 12. The positioner 12 moves the optical head 6 in the radial direction of the recording medium 1 according to the level of the positioning signal. The focus signal is a signal for driving the focus actuator 13. The focus signal is a signal of a level corresponding to the level of the focus error signal FE (the amount of deviation between the position of the light beam convergence point and the track surface). Focus actuator 1
3 moves the objective lens 6 in the direction perpendicular to the recording surface of the recording medium 1 by an amount corresponding to the level of the focus signal. This focuses the light spot on the track surface.

On the other hand, the phase pit signal PPS and the magneto-optical signal MOS are input to the system controller 20. These signals are output to the host computer 30 as information read from the recording medium 1. The system controller 20 communicates with the host computer 30 and, in response to a command from the host computer 30,
The read information is sent to the host computer 30.

Further, the system controller 20 creates a control signal based on the phase pit signal PPS and the magneto-optical signal MOS and sends it to the servo controller 10. FIG.
2 is a configuration diagram of the servo controller 10 and the system controller 20 of FIG. The servo controller 10
The land track control circuit 14, the groove track control circuit 15, the focus control circuit 16, the switch circuits 17 and 18, the positioner control circuit 19, and the land / groove identifying circuit 23 shown in FIG. The system controller 20 is composed of the address detecting circuit 21, the information reproducing circuit 22, the land / groove identifying circuit 23, and the control circuit 24 shown in FIG.

The track error signal TE is input to the land track control circuit 14 and the groove track control circuit 15. Each control circuit has the same control constant and the opposite polarity of the output signal. The switch circuit 17 includes a land track control circuit 14 and a groove track control circuit 15.
Input the output signal from. Then, one of the two input signals is selectively output according to the signal from the system controller 20. The output signal from the switch circuit 17 is output to the tracking actuator 11 as a tracking signal.

A part of the tracking signal from the switch circuit 17 is output to the positioner 12 as a positioning signal via the positioner control circuit 19. The focus error signal controls the focus actuator via the focus control circuit 16 and the switch circuit 18. The switch circuit 18 is controlled between an open state and a closed state by a signal from the system controller 20. That is, the presence or absence of the output from the switch circuit 18 is controlled.
The signal output from the switch circuit 18 is output to the focus actuator 13 as a focusing signal.

The phase pit signal (PPS) is input to the address detection circuit 21. In the address detection circuit 21,
A signal (address signal) indicating address information is detected from the phase pit signal. The magneto-optical signal (MoS) is input to the information reproducing circuit 22. Then, the magneto-optical signal MoS
Is reproduced by the information reproducing circuit 22. The address signal output from the address detection circuit 21 and the reproduction data output from the information reproduction circuit 22 are input to the control circuit 24. The control circuit 24 sends the reproduction data from the area of the desired address to the host computer 30.

FIG. 5 is a diagram showing changes in the track error signal. FIG. 5A shows a temporal change of the track error signal detected when the optical head 6 is moved from the inner circumference side to the outer circumference side in the radial direction. In FIG. 5A, the portion indicated by reference numeral (d) is when the light spot is passing through the land track. The portion indicated by the symbol (e) is when the light spot passes through the boundary between the land track and the groove track. The portion indicated by the symbol (f) is when the light spot is passing through the groove track.

FIG. 5B shows a change in the reflectance. The reflectance is the ratio of the amount of light received by the detector 8 to the amount of light emitted. The reflectance is lower when the light spot passes through the boundary between the land track and the groove track than when the light spot passes through the land track and when it passes through the groove track.

FIG. 5C shows a waveform of a track error signal when the push-pull method is used for detecting a tracking error. When the light spot passes through the land track, the slope of the change over time of the track error signal level is positive. That is, the level monotonically increases. Further, when the track error signal level is passed over the groove track, the gradient of the change with the passage of time becomes negative.

As can be seen from FIG. 5, the polarity of the tracking error signal is reversed between when the light spot passes through the land track and when it passes through the groove track. The tracking signal output from the land track control circuit 14 and the groove track detection circuit 15 is a signal for controlling the tracking actuator so that the level of the tracking error signal becomes zero. Since the polarity of the tracking error signal is reversed between when the light spot is on the land track and when the light spot is on the groove track, if the polarity of the tracking signal is also reversed, the tracking control in each track will be improved. Will be done. Therefore, in this embodiment, the polarity of the output of the land track control circuit 14 and the output of the groove track detection circuit 15 are reversed.

Next, the operation of the information reproducing apparatus of this embodiment will be described. First, a recording medium is inserted into the information reproducing device. The control circuit 24 controls the spindle motor 40
By sending a control signal to (as shown in FIG. 4), the spindle motor 40 starts rotating, and the recording medium installed on the turntable also rotates. The playback device detects whether the inserted recording medium is a land / groove recording medium.

This detection can be performed as follows. The information recording medium is stored in the case. A sensor hole is provided in a part of the case. The playback device detects the sensor hole in the case when the recording medium is inserted. If the sensor hole is detected in the playback device,
It can be recognized that the inserted recording medium is a land / groove recording medium.

Alternatively, the recording surface of the information recording medium may be provided with a mark indicating that it is a land / groove recording medium. For example, the recording surface of a magneto-optical disk generally has an area called a PEP (phase modulating portion). Various information about the medium is recorded here,
Information indicating the land / groove recording medium may be recorded in this area. Further, information indicating a land / groove recording medium may be recorded in a predetermined area of another predetermined track.

When the recording medium is inserted, the reproducing apparatus rotates the information recording medium at a predetermined rotation speed by the spindle motor. Next, the reproducing apparatus drives the focus actuator 13 of the optical head 6 to perform focus pull-in control on an arbitrary track on the recording medium. This focus pull-in control is performed by the system controller 2
This is performed when the control circuit 24 in 0 outputs a control signal and the switch circuit 18 is closed. When the switch circuit 18 is closed, a focusing signal is output from the switch circuit 18 to the focus actuator 13. Then, the light spot is focused on the track surface by the operation of the focus actuator 13.

When performing such focus pull-in control, the switch 17 is opened. That is, the land track control circuit 14, the groove track control circuit 1
The tracking signal from any one of 5 is not output to the tracking actuator 11. This state is a state in which the tracking servo loop is open (servo off).

In this case, since the tracking signal is not output, the absolute position of the light spot does not change. However, since the track of the disk 1 is eccentric, the relative position of the light spot and the track of the disk 1 is displaced in the radial direction due to the rotation of the disk 1. Therefore, the light spot does not continue to be illuminated on the same track.
The relative position of the light spot to the track is disc 1
Depending on the rotation of the, it moves outward or inward.

FIG. 6 is a diagram showing a change in reflectance and a change in offset of the track error signal when the irradiation position of the light spot relatively moves in the radial direction of the disk 1. Further, FIG. 7 is a diagram showing a configuration of the land / groove identifying circuit 23 for identifying whether the current position of the light spot is a land track or a groove track. FIG.
(A) shows the movement locus of the light spot on the track. The part indicated by the symbol k is the groove track, the part indicated by the symbol l is the boundary between the groove track and the land track,
The portion indicated by reference sign m is a land track.

FIG. 6B shows the change in reflectance. Since the intensity of the light beam applied to the recording medium during reproduction is constant, the reflectance is represented by the level of the output signal from the detector 8. When the widths of the land track and the groove track in the radial direction are made equal to each other as in the present embodiment, the change in reflectance when the light beam is irradiated to each position is as follows. When the light spot is on the groove track (symbol k), the reflectance becomes maximum,
The reflectance is minimum when the light spot is at the boundary between the groove track and the land track (reference numeral 1). When the light spot is on the land track (reference numeral m), the reflectance has an intermediate value between them.

Here, the land / groove discrimination circuit of FIG. 7 will be described. In FIG. 7, the phase pit signal PP
S is input to the comparator 201. The comparator 201 compares the level of the input phase pit signal with a predetermined threshold level, and outputs a pulse when the level of the input phase pit signal is high. The threshold level is
The level is indicated by n in FIG. The level n is set to a value lower than the level of the phase pit signal when the light spot is on the groove track and higher than the level of the phase pit signal when the light spot is on the land track. FIG. 6C shows the output pulse from the comparator 201. The output from the comparator 201 is input to the inverter 202, inverted and output. FIG. 6D shows the output pulse from the inverter 202. The pulse shown in FIG. 6D becomes low level when the pulse shown in FIG.
It goes high when the pulse in (a) is low.

The track error signal is sent to the comparator 20.
3 is input. FIG. 6 (e) shows the waveform of the track error signal. The track error signal is input to the comparator 201. 0V for the comparator 201
The track error signal is binarized by comparing the level with the level of the track error signal. The level of the binarized track error signal output from the comparator 201 changes from negative to positive when the light spot is at the center of the land track in the radial direction.

Schmitt trigger circuits 205 and 206
Detects a point where the binarized track error signal level changes from negative to positive and a point from positive to negative. That is, a binarized track error signal is input to the Schmitt trigger circuit 205, and a pulse signal is output when the level of the track error signal changes from negative to positive.
In addition, the Schmitt trigger circuit 206 includes an inverter 2
The signal from 04 is input. The inverter 204 has
A binarized track error signal from the binarization circuit 102 is input. That is, an inverted signal of the binarized track error signal is output from the inverter 204 and input to the Schmitt trigger circuit 206. The Schmitt trigger circuit 206 outputs a pulse signal when the level of the input inversion track error signal changes from negative to positive. That is, the pulse signal is output when the level of the track error signal (not inverted) changes from positive to negative.

FIG. 6F shows the Schmitt trigger circuit 20.
5 shows the waveform of the output signal from No. 5. As can be seen from the figure, the Schmitt trigger circuit 205 outputs a pulse when the level of the track error signal changes from negative to positive. Further, FIG. 6G shows the Schmitt trigger circuit 20.
6 shows the waveform of the output signal from No. 6. As can be seen from the figure, the Schmitt trigger circuit 206 outputs a pulse when the level of the track error signal changes from positive to negative.

The outputs from the Schmitt trigger circuits 205 and 206 are input to the OR circuit 207. OR circuit 2
07 outputs a logical sum signal of the two input signals. FIG. 6H shows the waveform of the output signal from the OR circuit 207. As can be seen from the figure, when the level of the track error signal changes from negative to positive or from positive to negative, the OR circuit 207 outputs a pulse.

With the above configuration, the OR circuit 207 outputs a pulse when the light spot reaches the center of the track (land track or groove track). O
The output from the R circuit 207 is the AND circuits 208 and 20.
9 is input to one of the input terminals. The output from the comparator 201 is input to the other input terminal of the AND circuit 208. The output from the inverter 202 is input to the other input terminal of the AND circuit 202.

The AND circuits 208 and 209 output a logical product signal of the two input signals. FIG. 6 (i) shows
The waveform of the output signal from the AND circuit 208 is shown,
FIG. 6 (j) shows the waveform of the output signal from the AND circuit 209. The AND circuit 208 outputs a pulse when the reflectance is higher than a predetermined value and the light spot is at the center of the track (that is, when the light spot is on the groove track). Also, the AND circuit 2
From 09, a pulse is output when the reflectance is smaller than a predetermined value and the light spot is at the center of the track (that is, when the light spot is on the land track).

With the above configuration, the AND circuit 20
It is possible to identify whether the current position of the light spot is a land track or a groove track, depending on which of 8 and 209 the pulse is output. When the light beam is first focused on a track, it is not known whether the focused track is a land track or a groove track. Therefore, the output from the land / groove identifying circuit 23 determines whether the track where the light spot is present is a land track or a groove track.

The control circuit 24 determines from the output signal from the identification circuit 23 whether the light spot is currently on the land track or the groove track. This determination is made by determining which A of the identification circuit 23, as described above.
This can be performed depending on whether a pulse is output from the ND circuit. If the control circuit 24 determines that the light spot is on the land track, it closes the switch circuit 17 to the side of the land track control circuit 14, and if it determines that it is on the groove track, it controls the switch circuit 17 on the groove track. Control to close the circuit 15 side is performed.

As a result, a tracking signal corresponding to the track on which the light spot is located is output to the tracking actuator 11, and tracking control is started. The light spot can continue to follow the focused track (land track or groove track). For example, if it is determined that the light spot is on the land track, the tracking condition is set to the condition corresponding to the land track. Then, tracking pull-in control is performed on the land track. This control is performed by the system controller 2
This is performed by selecting an output from the switch circuit 17 by outputting a control signal from the control circuit 24 in 0. The control circuit 24 outputs a control signal for causing the switch circuit 17 to output the output from the land track control circuit 14 as a tracking signal. As a result, the switch circuit 17 outputs a tracking signal having a polarity suitable for land track tracking control. This tracking signal is sent to the tracking actuator 11, and the tracking actuator 11 performs tracking pull-in control on the land track, and thereafter, the light spot keeps following the land track.

According to the above operation, the light spot is subjected to tracking control and focus control for a certain land track. Then, the light spot keeps following the land track, and keeps applying focus control to the land track surface. In this way, the light spot follows the land track and waits for an instruction from the host computer 30 installed outside the reproducing apparatus. Then, the host computer 30 receives an instruction to read information of a predetermined sector. This instruction is input to the control circuit 24 in the system controller 20. The control circuit 24 determines whether the sector that has received the read instruction exists on a land track or a groove track.

Then, the control circuit 24 obtains a difference between the current head position (current track) and the relative position of the sector (target track) that has received the read instruction. The control circuit 24 opens the tracking servo loop (servo off). This control may be performed by opening the switch circuit 17 so that the tracking signal from the switch circuit 17 is not output.

Next, the control circuit 24 performs control to move the optical head 4 in the direction of the target track by sending a control signal to the positioner control circuit 19. While the optical head 4 is moving, a track error signal as shown in FIG. The counter circuit 25 counts the number of pulses of the track error signal. This count value is input to the control circuit 24. From this count value, the number of tracks traversed by the light spot can be determined. Then, when the optical head 4 has been traversed by the number of tracks to the target track (when the position of the light spot is just above the target track), the movement of the optical head 4 is stopped, and the tracking servo is set to a closed loop (servo ON). The movement of the optical head 4 is stopped by the control circuit 24 sending a control signal to the positioner control circuit 19. The control circuit 24 controls the switch circuit 17 to make the tracking servo a closed loop. At this time, if the target track is a land track, the switching circuit 17 outputs a tracking signal having a polarity suitable for the tracking control of the land track. That is, the switch circuit 17 is connected to the output side from the land track control circuit 14. If the target track is a groove track, a tracking signal having a polarity suitable for the tracking control of the groove track is output. That is, the switch circuit 17 is connected to the output side of the groove track control circuit 15. Now, it is assumed that the target track is a groove track.

The reproducing apparatus reproduces information from the track followed by the light spot by tracking control and detects the track address. The control circuit 24 confirms that the detected track address is that of the groove track and that the track in which the sector for which the read instruction has been received exists is present.

If they are different, the difference in relative position between the current track address and the track (target track) in which the sector receiving the read instruction is present is obtained again. Then, the above operation is performed again. Then, when the current track address matches the address of the track on which the sector for which the read instruction is present is present, the reproducing apparatus reproduces the information of the sector for which the read instruction is received, and transfers the read information to an external host computer. This operation is performed when the control circuit 24 transfers the reproduction data from the information reproduction circuit 22 to the host computer 30.

Thereafter, the reproducing apparatus waits for an instruction from the host computer again.

[0068]

As described above, according to the present invention, the track pitch of the recording medium can be substantially halved as compared with the conventional one. Therefore, twice the information can be recorded on the recording medium. Furthermore, according to the present invention, the tracks of the first group and the tracks of the second group can be arbitrarily reproduced. Therefore, it can be used as a random access type storage device.

Also, the head does not require any special structure,
It does not increase the cost. Further, the present invention can be applied not only to a read-only medium such as a CD but also to a rewritable medium.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an information reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a track structure of an information recording medium used in an information reproducing apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an information reproducing apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a servo controller and a system controller of the information reproducing apparatus according to the embodiment of the present invention.

FIG. 5 is a diagram showing a change in polarity of a track error signal of the information reproducing apparatus according to the embodiment of the present invention.

FIG. 6 is a diagram for explaining the operation of the land / groove identifying circuit of the information reproducing apparatus according to the embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a land / groove identifying circuit of the information reproducing apparatus according to the embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a conventional CD (compact disc).

[Explanation of symbols]

 1: Disc-shaped recording medium (magneto-optical disk), 2: Land track, 3: Groove track, 4: Optical head, 5: Light source (semiconductor laser), 6: Objective lens, 8: Detector, 10: Servo controller, 14 : Land track control circuit, 15: Groove track control circuit, 16: Focus control circuit, 17, 18: Switch circuit, 20: System controller, 21: Address detection circuit, 22: Information reproducing circuit, 23: Land / groove discrimination circuit , 24: control circuit, 30: host computer, 40: spindle motor, 41: phase pit, 42: magneto-optical pit, 43, 45: address part, 44, 46: information recording part.

Claims (5)

[Claims] An information track of a first group and an information track of a second group on which information is recorded exist concentrically or spirally, and the track of the first group and the information track of the second group are present.
An information reproducing apparatus for reproducing recorded information by irradiating each of the tracks with a laser beam on a disc-shaped information recording medium in which the tracks of the group are alternately stepped in the radial direction. There, focus control means for converging the laser light on the track surface of the recording medium, detection means for detecting the reflectance of the surface irradiated with the laser light, and the laser light from the detection result of the detection means An information reproducing apparatus, comprising: a determining unit that determines whether the track illuminated by the light is a first group track or a second group track. 2. A first group of information tracks on which information is recorded and a second group of information tracks exist concentrically or spirally, and the first group of tracks and the second group of information tracks.
An information reproducing apparatus for reproducing recorded information by irradiating each of the tracks with a laser beam on a disc-shaped information recording medium in which the tracks of the group are alternately stepped in the radial direction. And a focus control unit that converges the laser light on the track surface of the recording medium, a detection unit that detects the reflectance of the surface irradiated with the laser light, and an irradiation position of the laser light in the first group. Tracking control means for making the track follow the other track or the tracks of the second group, and the control condition in the tracking control means is set to the tracking control condition for the first group track or the tracking control condition for the second group track. The setting means to be set and the detection result of the detection means are An information reproducing apparatus comprising: a determination unit that determines whether the track irradiated with the laser beam is a first group track or a second group track and sets the control condition according to the determination result. . 3. The information reproducing apparatus according to claim 2, wherein the setting of the tracking control condition in the setting means is a setting for switching the polarity of the track error signal used in the tracking control. 4. The light receiving means for receiving the reflected light of the laser light from the surface of the recording medium and outputting a signal according to the amount of received light, the detecting means having a light receiving means. The information reproducing apparatus according to claim 2 or claim 3. 5. A signal generating means for generating a track error signal indicating a deviation amount between the irradiation position of the laser beam and the track of the first group or the track of the second group, the judging means comprising: 3. The information reproducing apparatus according to claim 2, wherein the determination is made based on the detection result of the detecting means and the track error signal.