JPH0689442A - Information recording medium and cutting device - Google Patents

Abstract

PURPOSE:To eliminate the influence of the difference between linear velocities at the inner and outer peripheries of a recording medium in an optical information reproducing device with a CAV system and to generate a stable servo signal by adjusting the shapes of one and more pits among plural pits according to the radial position of a recording medium. CONSTITUTION:By synchronizing with a clock synchronized with the rotation of an optical disk 2, a laser driving circuit 12 irradiates the disk 2 with laser light from a semiconductor laser 3 through optical systems 3-6. At this time, a position detecttor 11 outputs a detection signal based on the radial position of the disk 2 to a power control circuit 13. Based on this detection signal, the circuit 13 reads power data x increasing from an inner to an outer peripheries out of a memory 14 and irradiates the circuit 12 with laser light having the corresponding power. Consequently, control pits 61, 62 for controlling a rise and a fall are formed according to the radius before and after a wobbling pit 81 and the servo signal of a CAV type reproducing device is stably generated without being affected by the difference of linear velocities between the inner and the outer peripheries.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample servo type information recording medium and a cutting device for forming servo pits recorded in a servo area of the information recording medium.

[0002]

2. Description of the Related Art Generally, in an optical recording / reproducing apparatus (hereinafter referred to as an optical disk apparatus), in order to record or reproduce information on a track on an optical recording medium (hereinafter referred to as an optical disk), It is necessary to detect and generate the tracking error signal and the bit clock signal.

One of the detection methods is called a sample servo method. As shown in FIG.
The format of the optical disk in the sample servo method is
A clock pit 80 provided at the center of the track of the servo area and two wobble pits 81 intermittently provided along the track at positions displaced from the center of the track by about 1/4 track pitch in the opposite direction in the radial direction. As shown in FIG. 5B, the reflected light intensity of the light beam 82 from the disc due to the wobble pits is A / D converted at predetermined timings a1, a0, a2, b1 ,. A sample value is calculated to generate a tracking error signal and a PLL error signal.

The detection of tracking error (Trk.error) in the sample servo type optical disk is
Performed by subtracting the sample value at the wobble pit displaced to one side from the sample value at the wobble pit displaced to the other side, Trk. error = c0-a0 (1)

On the other hand, a bit clock signal is generated by a phase locked loop (PLL) circuit, and a PLL error signal (PLL error) which is phase information is PLL error = {(a2-a1) + (c2-c1). } / 2 (2), and this PLL error signal and V in the PLL circuit are obtained.
A bit clock signal for data demodulation is generated by phase comparison of the CO outputs.

Normally, the clock pit and the two wobble pits provided in the servo area are each 1 bi.
It is formed by the information corresponding to t. The reproduced signal waveform obtained from this servo area is the MTF of the optical pickup.
The reproduction signal determined by (Modulation Transfer Function) with respect to the spatial frequency has the same reproduction waveform on the inner and outer peripheries as shown in FIG. 6 if the pits have the same size.

[0007]

[Problems to be Solved by the Invention] However, CAV
In the (Constant Anguler Velocity) type optical disk device, as shown in FIG. 7A, the linear velocity of track reproduction increases in proportion to the radius. For example, if the linear velocity of a track with a radius of 1 is VL, The linear velocity on a track with a radius of 2 is 2VL. In this way, since the linear velocities of the inner circumference and the outer circumference of the optical disk are different, considering the time axis, for example, the reproduction waveform of the wobble pits on the outer circumference is as shown in FIG.
As shown in (b), the peak waveform has a large inclination (close to vertical) with respect to the reproduced waveform in the inner circumference.

As shown in equation (2), the PLL error signal depends on the value of the reproduced signal at both ends of the wobble pit (a1 and a2 at the outer circumference and a1 ', a2' difference signal at the inner circumference). To do. Therefore, the difference in the slope (PLL sensitivity) of the PLL error signal with respect to time, that is, as shown in FIG. 7B, the PLL error signal due to a1 ′ and a2 ′ of the reproduced signal at the inner circumference, which has a relatively gentle slope. And the generation of the PLL error signal by the reproduced signals a1 and a2 at the outer periphery having a large inclination have different effects on the time axis,
There is a problem that such a difference in PLL sensitivity between the inner and outer circumferences cannot be absorbed by signal processing by a circuit or the like even during seek.

The present invention has been made in view of the above circumstances, and when a servo signal is generated in a CAV type optical information reproducing apparatus, a stable servo signal is generated without being affected by the difference in linear velocity between the inner and outer circumferences. It is an object of the present invention to provide an information recording medium capable of performing the above and a cutting device for forming servo pits recorded on the information recording medium.

[0010]

According to another aspect of the present invention, there is provided an information recording medium, wherein a plurality of tracks are formed in a concentric circle shape or a spiral shape, and the tracks are composed of a plurality of servo areas and a plurality of data areas. Therefore, a clock pit 80 and a wobble pit 81 are provided as a plurality of pits in a plurality of servo areas.
In the disk-shaped information recording medium in which the pits are formed, at least one of the clock pits 80 and the wobble pits 81 is configured so that its shape is adjusted according to the radial position of the information recording medium in which the pits are formed. It is characterized by

According to a fourth aspect of the present invention, a plurality of tracks are formed in a concentric circle shape or a spiral shape, and a plurality of tracks of an optical disk 2 as an information recording medium having a plurality of servo areas and a plurality of data areas. Of the semiconductor laser 3 as a light beam irradiating means for irradiating a light beam for forming a plurality of pits on the servo area of the optical disk 2 The power control as a control means for controlling the semiconductor laser 3 according to the detector 11 and the radial position of the optical beam of the optical beam detected by the position detector 11 and controlling at least one of the intensity of the optical beam and the irradiation time. And a circuit 13.

[0012]

According to the present invention, in at least one of the clock pits 80 and the wobble pits 81, at least one of the clock pits 80 and the wobble pits 81 is a radial position of the information recording medium. Since the shape is adjusted in accordance with the above, when the servo signal is generated in the CAV type optical information reproducing apparatus, it is possible to stably generate the servo signal without being affected by the difference in linear velocity between the inner and outer circumferences of the information recording medium. You can

According to another aspect of the cutting device of the present invention, the power control circuit 13 includes the position detector 11.
In the CAV type optical information reproducing apparatus, since the semiconductor laser 3 is controlled according to the radial position of the optical beam detected by the semiconductor laser 3 and at least one of the intensity and the irradiation time of the optical beam is controlled. It is possible to obtain the optical disc 2 that can generate a stable servo signal without being affected by the difference in linear velocity between the inner and outer circumferences of the information recording medium when the servo signal is generated.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 relate to a first embodiment of the present invention, FIG. 1 is a block diagram showing a configuration of a main part of a cutting device for forming servo pits of an information recording medium, and FIG. 2 is a PLL.
FIG. 3 is a block diagram showing a circuit configuration, FIG. 3 is an explanatory diagram for explaining servo pit formation by a cutting device, and FIG. 4 is an explanatory diagram for explaining a relationship between servo pit formation power and a radial position of a light beam.

As shown in FIG. 1, a cutting device 1 for forming servo pits of an information recording medium of this embodiment has a recording surface of an optical disc 2 as an information recording medium which is rotationally driven by a spindle motor (not shown). A semiconductor laser 3 for forming a servo area by irradiating a recording laser beam in synchronization with the rotational drive of the optical disk 2 is provided. The laser light from the semiconductor laser 3 is converted into substantially parallel light by the collimator lens 4, then the parallel light is incident on the beam splitter 5, and the light transmitted through the beam splitter 5 is condensed by the objective lens 6. The servo area of the optical disc 2 is irradiated as a light spot to form a pit.

Further, the cutting device 1 is provided with a position detector 11 for detecting the radial position of the optical disk 2 irradiated with the light condensed by the condenser lens 8. This position detector The detection signal from 11 is input to a power control circuit 13 that controls a laser drive circuit 12 that drives the semiconductor laser 3 to emit light.
On the basis of the detection signal from the position detector 11, it reads the data stored in advance in the memory 14 and controls the laser drive circuit 12 according to the radial position of the optical disc 2. The optical system including the semiconductor laser 3 can be moved in the radial direction of the optical disc 2 by a driving device (not shown).

When the clock pits 80 and the wobble pits 81 shown in FIG. 5 are formed on the optical disc 2, since these pits have not been formed yet, the optical disc 2 is rotated on the basis of a predetermined fixed clock. The position of the pit is determined on the basis of a clock generated in synchronization with the rotation of the optical disc 2.

On the other hand, in order to check the formed pits, the semiconductor laser 3 irradiates a reproducing laser beam having an intensity smaller than that of the recording laser beam. The light irradiated onto the optical disk 2 through the same optical path as the recording laser light and reflected by the optical disk 2 travels again to the beam splitter 5 via the objective lens 6. The light reflected by the beam splitter 5 is condensed by the condenser lens 8 to form an image on the photodetector 9, and is transmitted to the signal processing circuit 10 as a reproduction signal.

In the signal processing circuit 10, as shown in FIG. 2, the RF signal from the photodetector 9 is AGC.
After the gain is adjusted by the (auto gain controller) 30, it is input to the A / D converter 31 and converted into a digital signal. The conversion sampling rate of the A / D converter 31 is determined by a master clock generated by a digital PLL (phase lock rope) 32. From the digital RF signal which is the digital signal converted by the master clock,
The address detection circuit 33 detects the address of the light spot irradiation area of the reproduction laser light.

In the digital PLL 32, the output of the A / D converter 31 is input to the phase difference detection circuit 35, and the output of the phase difference detection circuit 35 is VCO (voltage control) via an LPF (low pass filter) 36. (Oscillator) 37. The output of the VCO 37 is fed back to the phase difference detection circuit 35 via the 1 / N frequency divider 38. As a result, the phase difference of the output of the VCO 37 with respect to the output of the A / D converter 31 is detected by the phase difference detection circuit 35, and a voltage corresponding to this phase difference is input to the VCO 37 and synchronization is performed so as to eliminate the phase difference. It is designed to generate a master clock.

The phase difference detection circuit 35 detects the phase difference as shown in FIG.
The intensity (FIG. 5 (b)) of the reflected light from the optical disk 2 according to 1 (FIG. 5 (a)) is A / D converted and detected by a PLL error signal generated by calculation.

Such a cutting device 1 is shown in FIG.
The laser drive circuit 12 irradiates the optical disk with a recording laser beam in synchronization with a clock synchronized with the rotation of the optical disk 2 shown in FIG. At this time, the power control circuit 13 stores in the memory 14 the power data x increasing from the inner circumference to the outer circumference as shown in FIG. 4 based on the radial position irradiated with the laser light by the detection signal of the position detector 11. As shown in FIG. 3B, the laser light having the cutting power corresponding to the power data x is irradiated before and after the wobble pit 81 shown in FIG. 5, for example. As a result, as shown in FIG. 3C, a rising control pit 61 and a falling control pit 62 are formed before and after the wobble pit 81.

The sizes of the rising control pit 61 and the falling control pit 62 differ depending on the power data x. For example, when the power data x is increased corresponding to the outer peripheral side as shown by the broken line, the rising control pit 6
1 and the falling control pit 62 also become larger (longer). When the formed pit is reproduced by the reproduction optical system, a reproduction signal corresponding to the radial position can be obtained as shown in FIG.

That is, when the rising control pits 61 and the falling control pits 62 are not formed, the slope of the reproduced waveform becomes larger toward the outer circumference (closer to vertical) as shown by the broken line in FIG. 4 (d). . On the other hand, when the control pits 61 and 62 are formed, the same inclination can be obtained in the outer circumference as in the inner circumference as shown by the solid line.

Since the tracking error signal is calculated by the above equation (1), if the length of the wobble pit 81 is sufficiently long (for example, a length of 2 clocks (2 bits) or more), The levels at the timings a0 and c0 in FIG. 5 are constant in the inner and outer circumferences. Therefore, the sensitivity is such that the rising control pit 61 and the falling control pit 6 are formed before and after the wobble pit 81.
It can be made constant by adding 2 and increasing the pit length.

Further, since the PLL error signal is calculated by the above equation (2), its sensitivity changes depending on the length of the wobble pit 81 and the inclination of the reproduced waveform.
That is, since the PLL sensitivity is related to the shapes of the rising control pit 61 and the falling control pit 62, the relationship between the radius and the power data x is set so that the PLL sensitivity is constant, as shown in FIG. As a result, the length of the wobble pit 81 is set to 2 clocks (2 bits) or more, and the pit shape is formed so that the inclination of the reproduced waveform is constant at the outer circumference and the inner circumference.

As described above, according to the optical disc of the present embodiment, the wobble pit 8 is formed so that the PLL sensitivity becomes constant.
Since the rising control pit 61 and the falling control pit 62 are provided before and after 1, the servo signals such as the tracking error signal and the PLL error signal are generated at the inner and outer circumferences when the servo signal is generated in the CAV type optical information reproducing apparatus. It can be stably generated without being affected by the difference in linear velocity.

Although the wobble pit 81 is used as the pit for providing the rising control pit 61 and the falling control pit 62, the rising control pit 61 and the falling control pit 61 and the falling pit are not limited to the wobble pit 81, but are also forward and backward. The control pit 62 may be provided and formed.

Further, in the above, the intensity of the laser beam is adjusted to adjust the pit shape including the pit length, but the irradiation time of the laser beam may be adjusted.

[0031]

As described above, according to the information recording medium of the first, second and third aspects, at least one pit of the plurality of pits is the radius of the information recording medium in which the pits are formed. Since the shape is adjusted according to the position, when the servo signal is generated in the CAV type optical information reproducing device,
There is an effect that stable servo signal generation can be performed without being affected by the difference in linear velocity between the inner and outer circumferences of the information recording medium.

According to a fourth aspect of the present invention, the control means controls the light beam irradiation means according to the radial position of the information recording medium of the light beam detected by the irradiation position detection means, and Since at least one of the beam intensity and the irradiation time is controlled, stable servo can be performed without being affected by the difference in linear velocity between the inner and outer circumferences of the information recording medium when the servo signal is generated in the CAV type optical information reproducing apparatus. The information recording medium capable of generating a signal can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a main part of a cutting device for forming a servo pit of an embodiment of an information recording medium of the present invention.

FIG. 2 is a block diagram showing a configuration of a signal processing circuit shown in FIG.

FIG. 3 is an explanatory diagram illustrating formation of servo pits by the cutting device of FIG.

FIG. 4 is an explanatory diagram illustrating a relationship between a servo pit forming power and a radial position of a light beam by the cutting device of FIG.

FIG. 5 is an explanatory diagram illustrating generation of a servo signal using wobble pits and clock pits according to a conventional example.

FIG. 6 is an explanatory diagram illustrating a relationship between a reproduction signal and a pit according to a conventional example.

FIG. 7 is an explanatory diagram illustrating a relationship between a reproduction signal and time in a CAV type optical information reproducing device according to a conventional example.

[Explanation of symbols]

 1 Cutting Device 2 Optical Disc 3 Semiconductor Laser 11 Position Detector 12 Laser Drive Circuit 13 Power Control Circuit 61 Rise Control Pit 62 Fall Control Pit 80 Clock Pit 81 Wobble Pit

Claims (4)

[Claims] 1. A disk on which a plurality of tracks are formed in a concentric circle shape or a spiral shape, and the tracks include a plurality of servo areas and a plurality of data areas, and a plurality of pits are formed in the plurality of servo areas. The information recording medium as described above, wherein the shape of at least one pit of the plurality of pits is adjusted according to the radial position of the information recording medium in which the pit is formed. 2. The information recording medium according to claim 1, wherein the pits whose size is adjusted according to the radial position of the information recording medium are wobble pits. 3. The information recording medium according to claim 1, wherein the pits whose size is adjusted according to the radial position of the information recording medium are clock pits. 4. A plurality of tracks are formed concentrically or spirally, and the tracks form a plurality of pits in the plurality of servo areas of an information recording medium including a plurality of servo areas and a plurality of data areas. A light beam irradiating means for irradiating a light beam, an irradiation position detecting means for detecting a radial position of the light beam irradiated by the light beam irradiating means on the information recording medium, and the light beam detected by the irradiation position detecting means 2. A cutting device, comprising: a control unit that controls the light beam irradiation unit according to the radial position of the information recording medium, and controls at least one of the intensity and the irradiation time of the light beam.