JP2001325743A - Optical recording / reproducing device and optical head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably perform recording and / or reproduction on a high-density optical recording medium while maintaining compatibility of optical recording media having different track pitches. SOLUTION: A rotary drive unit for rotatingly driving an information recording medium, an optical head for irradiating the information recording medium with light to record and / or reproduce an information signal, and processing a signal detected by the optical head Signal processing circuit,
The optical head includes a light source, an objective lens, and signal detection means. The numerical aperture NA of the objective lens is 0.5
<NA ≦ 0.6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus having an optical head for recording and / or reproducing information on an optical recording medium by irradiating the optical recording medium with a laser beam. Optical recording / reproducing apparatus for handling a plurality of optical recording media having recording tracks formed at different track pitches or an optical recording medium having a plurality of recording areas having recording tracks formed at different track pitches, and tracking control in the same Method etc.

[0002]

2. Description of the Related Art Information recording media such as read-only optical disks, phase-change optical disks, magneto-optical disks, and optical cards are widely used to store data such as video information, audio information, and computer programs. I have. In recent years, demands for higher recording density and higher capacity of these information recording media have been increasing.

In recent years, as an information recording means of a computer or the like, a write-once compact disc (CD-R: CD-Recordable) having reproduction compatibility with a compact disc (CD).
And rewritable compact disc (CD-RW: CD
-Rewritable) has appeared, and CD-R / RW devices for recording and / or reproducing information signals on and from these optical recording media are becoming widespread.

Further, there is an increasing demand for storing large-capacity data such as image data.
It is desired to increase the recording capacity of an optical recording medium such as R / RW.

By the way, for example, CD-R and CD-RW
In an optical disk recording / reproducing apparatus that handles an optical disk such as an optical disk, a tracking error signal is transmitted to a DPP (Differenti
al Push Pull) method or a three-spot method.

FIG. 11 shows a relationship between a spot on a disk and a spot on a photodetector when a tracking error signal is obtained by the DPP method.

[0007] On the optical disc 211 includes a main spot SP _m by the main beam, a side spot _SP s1, _{SP s2} by the side beams are formed. Interval of groove GR as recording track (track pitch)
Is defined as Tp, the side spots SP _s1 and SP _s2
, Relative to the main spot SP _m, in one direction and the other direction of the radial direction, respectively Tp / 2 (180
゜) formed at a position apart from each other.

Further, the photodiode units 212M, 212S ₁ , 212S ₂ constituting the photo detector 212
_Includes spots SP _m ′, SP _s1 ′, and S s by light beams reflected by the spots SP _m , SP _s1 , and SP _s2 formed on the optical disk 211 described above, respectively.
P _s2 ′ is formed. Here, the photodiode unit 2
The detection signals of the four photodiodes D _a and D _d constituting 12M are denoted by S _a and S _d , and the photodiode unit 212
Two photodiodes _D e constituting the S _1, a detection signal of the _{D f} and _S e, _{S f,} further photodiode unit 2
_Two photodiodes D _g and D _h constituting 12S ₂
The detection signal and _S g, _{S h.}

FIG. 12 shows circuit connections when a tracking error signal _STE is obtained by the DPP method.
In the subtracter 221M, than the addition signal of the detection signal _{S a} and the detection signal _{S d,} the detection signals _{S b} and is subtracted sum signal of the detection signal _{S c} is, push-pull signal _{S ppm} by the reflected light from the main spot SP _m Is obtained. Subtractor 2
In 21S _1, is subtracted the detection signal _{S e} from the detection signal _{S f,} the push-pull signal _{S PPS1} by the reflected light from the side spot _{SP s1} is obtained. Further, the subtractor 22
In 1S _2, it is subtracted detection signal Sh from the detection signal _{S g} is, push-pull signal _{S pps2} by the reflected light from the side spot _{SP s2} is obtained.

Further, the adder 222, the gain push-pull signal received through the amplitude adjuster 223 for G2 _{S pps2} and push-pull signal _{S PPS1} and are added to produce signal _{S s} is obtained. Then, the subtractor 224 subtracts the addition signal Ss from the push-pull signal S _ppm via the amplitude adjuster 225 having the gain G1, and the tracking error signal S
_TE is obtained. Here, the amplitude of the push-pull signal S _ppm is A1, and the amplitude of the push-pull signal S _pps1 is A
2, when the amplitude of the push-pull signal _{S pps2} and A3, are set to G1 = A1 / 2A2, G2 = A2 / A3, the offset is removed from the tracking error signal _{S TE.}

FIG. 13 shows the relationship between spots on a disc and spots on a photodetector when a tracking error signal is obtained by the three-spot method.

[0012] On the optical disc 211 includes a main spot SP _m by the main beam, a side spot _SP s1, _{SP s2} by the side beams are formed. Interval of groove GR as recording track (track pitch)
Is defined as Tp, the side spots SP _s1 and SP _s2
, Relative to the main spot SP _m, in one direction and the other direction of the radial direction, respectively Tp / 4 (90 °)
It is formed only at a position distant.

Further, a photodetector 213 is formed.
Photodiode section 213M, 213S₁, 213S₂
Are respectively formed on the optical disk 211 described above.
Spot SP_m, SP_s1, SP_s2Light reflected by
Spot SP by beam_m', SP_s1', S
P_s2'Is formed. Here, the photodiode unit 2
Four photodiodes D constituting 13M_a, D_dof
Set the detection signal to S_a, S_dAnd the photodiode unit 213
S₁Of the photodiode D_fThe detection signal of _f
And the photodiode section 213S₂Make up
Photodiode D_eThe detection signal of_eAnd

FIG. 14 shows a circuit connection when the tracking error signal _STE is obtained by the three-spot method. That is, the subtractor 226, the detection signal _{S e} from the detection signal _{S f} is subtracted, the tracking error signal _{S TE}
Is obtained.

[0015]

To increase the recording capacity of the optical recording medium as described above, a method of increasing the linear density or a method of increasing the track density is effective. However, if an attempt is made to increase the linear density of an optical recording medium without changing the specifications of an optical system for recording and reproducing information signals on such an optical recording medium, the jitter of the reproduced signal increases due to intersymbol interference. Would. Further, if the track density of the optical recording medium is increased without changing the specifications of the optical system, crosstalk occurs and it becomes difficult to perform stable reproduction.

Therefore, these problems can be solved by changing the specifications of the optical system to reduce the diameter of the reading spot.

In order to reduce the spot diameter, a method of reducing the laser wavelength of the optical system or the numerical aperture N of the objective lens is used.
A method for increasing A is given. However, if the laser wavelength is changed, recording and reproduction of the current CD-R cannot be performed. This is because the reflectance of the dye film constituting the recording layer provided on the CD-R disk largely depends on the wavelength of the laser. Also, if the NA of the objective lens is too large, the effect of jitter deterioration due to coma aberration caused by the warpage of the disk with respect to the optical axis of the laser and spherical aberration caused by unevenness in the thickness of the disk becomes extremely large, and the practical use becomes difficult. This is because it becomes difficult.

Further, when the tracking error signal detection is performed on a plurality of types of disks having different track densities (track pitches), the following problems are considered. In other words, as described above, when the tracking error signal _STE is obtained by the DPP method, the side spots SP _s1 and SP _s2 are _shifted with respect to the main spot SP _m by Tp in one radial direction and the other direction. / 2 away from each other. Therefore,
When the track pitch Tp is 1.6 μm like a CD (Compact Disc), an optical disk drive that handles the track pitch Tp, as shown in FIG.
_s1 and SP _s2 are arranged in the radial direction in one direction and the other direction with respect to the main spot SP _m , respectively.
It is formed at a position separated by 6/2 μm (180 °).

In such an optical disk drive, Tp =
When the 1.6 μm optical disk 211S is mounted, the push-pull signals S _ppm , S _pps1 , and S _pps S with respect to the radial position of the main spot SP _m.
pps2 changes as shown in FIGS. 15B, C, and D, respectively. In this case, since the push-pull signal S _pps1 and the push-pull signal S _pps2 have an in-phase relationship, the tracking error signal S _TE becomes as shown in FIG.
It has a sufficient amplitude.

However, in such an optical disk drive, for example, the track pitch Tp is 1.0 of １．０ of CD.
Optical disk 21 having a recording capacity of 7 μm and larger than a CD
When 1D is mounted, it is difficult to obtain a tracking error signal _STE having a sufficient amplitude. In this case, as shown in FIG.
P _s1 and SP _s2 are relative to the main spot SP _m .
It is formed at a position separated by 1.6 / 2 μm (270 °) in one direction and the other direction in the radial direction. Therefore, with respect to the radial direction position of the main spot SP _m, the push-pull signal _{S ppm, S PPS1,
Spps2} changes as shown in FIGS. 16B, C, and D, respectively. In this case, since the opposite phase relation to the push-pull signal _{S PPS1} and the push-pull signal _{S p ps2,} the tracking error signal _{S TE} is as shown in FIG. 16E, the amplitude smaller ones.

[0021] Thus, the main spot SP _m, side spots SP at positions apart respectively 1.6 / 2 [mu] m in one direction and the other direction of the radial direction
_{In the} optical disk drive in which _s1 and SP _s2 are formed,
Since the amplitude of the tracking error signal _{S TE} by the DPP method becomes extremely small when the optical disc 211D track pitch Tp is 1.07μm 2/3 of CD is mounted, the track pitch Tp is 1.07μ
It is difficult to handle the optical disk 211D of m.

Further, as described above, when the tracking error signal _STE is obtained by the three-spot method, the side spots SP _s1 and SP _s2 are positioned in one radial direction and the other direction with respect to the main spot SP _m . Are formed at positions apart from each other by Tp / 4. Therefore,
When the track pitch Tp is 1.6 μm as in the case of a CD, an optical disk drive that handles the track pitch Tp uses FIG.
As shown in, side spots SP _s1 and SP _s2 are
The main spot SP _m, in one direction and the other direction of the radial direction, respectively 1.6 / 4 [mu] m (90
゜) formed at a position apart from each other.

In such an optical disk drive, Tp =
When the 1.6 μm optical disk 211S is mounted, the main signal S _m (the addition signal of the detection signals S _a and S _d ) and the detection signals S _e and S _f are determined with respect to the radial position of the main spot SP _m. , Respectively, FIG. 17B, C,
It changes as shown in D. In this case, since the detection signal S _e and S _f in the opposite phase relationship, the tracking error signal S _TE is, as shown in FIG. 17E, it comes to have a sufficient amplitude.

However, such an optical disk drive device
For example, the track pitch Tp is 1.0 of ＣＤ of the CD.
Optical disk 21 having a recording capacity of 7 μm and larger than a CD
If 1D is mounted, a track with sufficient amplitude
King error signal S_TEIt is difficult to get. this
In this case, as shown in FIG.
P_s1, SP_s2Is the main spot SP_mFor
In one radial direction and the other,
Formed at a distance of 1.6 / 4 μm (135 °)
You. Therefore, the main spot SP_mRadial position of
The main signal S _m, Detection signal S_e, S_fIs
Each changes as shown in FIGS. 18B, 18C and 18D. this
In this case, since the detection signals Se and Sf do not have an antiphase relationship,
Tracking error signal S_TEIs as shown in FIG. 18E
Then, the amplitude becomes small.

As described above, the side spot SP is located at a position apart from the main spot SP _m by 1.6 / 4 μm in one radial direction and the other in the radial direction.
_{In the} optical disk drive in which _s1 and SP _s2 are formed,
Since the amplitude of the tracking error signal _{S TE} by the three-spot method is extremely small when the optical disc 211D track pitch Tp is 1.07μm 2/3 of CD is mounted, the track pitch Tp is 1. 0
It becomes difficult to handle the optical disk 211D of 7 μm.

The present invention has been proposed in view of the conventional circumstances as described above, and has been designed to record and / or reproduce data on / from a high-density optical recording medium while maintaining compatibility with existing optical recording media. It is a first object of the present invention to provide an optical recording / reproducing apparatus capable of performing a stable operation. It is a second object of the present invention to provide an optical recording / reproducing apparatus or the like which can obtain a good tracking error signal regardless of the track pitch.

[0027]

According to the present invention, there is provided an optical recording / reproducing apparatus for rotating an information recording medium, and irradiating the information recording medium rotationally driven by the rotation driving means with light. An optical head that records and / or reproduces an information signal; and a signal processing circuit that processes a signal detected by the optical head. The optical head includes a light source that emits light, and a light source that emits light. An objective lens for condensing the light on the information recording medium, and signal detecting means for receiving a return light reflected by the information recording medium and detecting a signal. In the optical recording / reproducing apparatus according to the present invention, the numerical aperture NA of the objective lens is in a range of 0.5 <NA ≦ 0.6.

In the optical recording / reproducing apparatus according to the present invention as described above, the numerical aperture NA of the objective lens is 0.5 <NA.
Since it is specified in the range of ≦ 0.6, it is possible to stably record and / or reproduce information by reducing the laser spot on a double-density information recording medium. It also has playback compatibility.

An optical disk drive according to the present invention provides an optical disk having at least a plurality of optical disks having recording tracks formed at different track pitches or an optical disk having a plurality of recording areas having recording tracks formed at different track pitches. An optical disk drive for handling a main spot, a first spot and a second side spot at positions spaced apart from each other in one and other radial directions with respect to the main spot. And an error generating a tracking error signal corresponding to a shift of a main spot from a predetermined recording track in a radial direction by using a light beam irradiating means for forming a laser beam and reflection light from at least the first and second side spots. Signal generation means and a tracking error signal. There main spot is one that includes a tracking control means for controlling so as to be positioned on a predetermined recording track. Then, the light beam irradiating means is provided with a position in the radial direction of the first and second side spots at which the amplitude of the tracking error signal generated by the error signal generating means becomes maximum when the track pitch is the largest among the different track pitches. Is the first position,
First and second amplitudes of the tracking error signal generated by the error signal generating means are maximum when the track pitch is the smallest of the different track pitches.
When the radial position of the side spot is defined as a second position, the first and second side spots are formed between the first position and the second position.

As described above, the first and second side spots have the first position where the amplitude of the tracking error signal is maximum at the maximum track pitch and the amplitude of the tracking error signal is maximum at the minimum track pitch. The tracking error signal is formed between the second position and the tracking error signal having a sufficient amplitude level even if the track pitch changes. Thereby, it is possible to handle a plurality of optical disks having recording tracks formed with different track pitches or an optical disk having a plurality of recording areas having recording tracks formed with different track pitches without changing the optical system. Becomes

When the track pitch of the optical disk to be handled changes, the amplitude of the generated tracking error signal changes. Therefore, a gain control means for controlling the gain of the error signal generating means so that the amplitude of the tracking error signal becomes constant at different track pitches may be further provided.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a recording / reproducing apparatus to which the present invention is applied. The recording / reproducing apparatus 1 includes a spindle motor 2
To perform recording and reproduction on the optical disc 3 rotating at a predetermined speed.

As shown in FIG. 2 to be described later, an optical disk 3 on which recording and reproduction is performed by the recording and reproduction apparatus 1 has information d by a phase change on a substrate 3a having a thickness d of, for example, about 1.2 mm. A recording layer for recording signals is formed, and the thickness t is, for example, about 0.1 mm on this recording layer.
The protective layer 3b is formed. The recording layer may be provided with a dye film like a CD-R.

The optical disk 3 is adapted to perform recording and reproduction by irradiating light from the substrate 3a side.

Although not shown, the disc 3 has a spirally formed groove GR on a data recording surface, and data is recorded and reproduced using the groove GR as a track. In this drive 1, the track pitch T
Both the disk 3S whose p is 1.6 μm and the disk 3D having a recording capacity of about twice the density of the disk 3S are handled.

The disk 3D having the double-density recording capacity has a track pitch Tp in the range of 1.0 μm to 1.2 μm. Specifically, the track pitch Tp
Is 1.10 ± 0.03 μm, and in the present embodiment, the track pitch Tp is 1.07 μm. This optical disc 3D has a shortest pit length (3T) of 0.555 μm.
m to 0.694 μm. In particular,
The shortest pit length (3T) of the disk 3S whose track pitch Tp is 1.6 μm is 0.833 μm, while the shortest pit length (3T) of the disk 3D is 0.625 μm.
m. The optical disk 3D on which recording and reproduction are performed by the optical head 4 is rotationally driven by the spindle motor 2 at a linear speed in a range of 0.8 m / sec to 1.0 m / sec.

The groove GR is slightly wobble, and is used as an address at recording (position information of a blank disk). This is ATIP (Ab
This is called “solute time in pregroove” and is devised as address information for a relatively long basic data unit such as a CD. The recorded time information is the same as that recorded in the Q channel of the subcode of the normal CD.

The ATIP has a job of generating address information at the time of recording, generating a synchronization signal for rotation servo at the time of recording, and generating various control signals. AT
The control signals recorded in the IP include the lead-in start time indicating the maximum recordable time, the lead-out start time when the program length is maximized, the write power recommended for the medium, the disc type, and the like. is there.

The optical recording / reproducing apparatus 1 of the present invention is particularly suitable for recording and / or reproducing information signals on a double-density optical disc 3D having the above-mentioned specifications. The optical recording / reproducing apparatus 1 of the present invention
The track pitch Tp is 6 ± 0.1 μm as shown in FIG.
Current single-density optical disks 3S (CD-ROM, C-ROM) whose shortest pit length (3T) is about 0.833 μm.
It also has playback compatibility with D-R, CD-RW and CD-DA.

As shown in FIG. 1, the recording / reproducing apparatus 1 comprises a spindle motor 2, an optical head 4,
F signal processing unit 5, EFM decoder 6, ATIP decoder 7, spindle driver 8, servo control unit 9
, A two-axis driver 10, an EFM encoder 11, a write strategy circuit 12, and an APC circuit 13.

The optical head 4 irradiates a laser beam to the optical disk 3 rotated and driven by the spindle motor 2 and receives the reflected light from the optical disk 3 to reproduce a signal.

Here, the specific configuration of the optical head 4 will be described later, but the numerical aperture NA of the objective lens 25 for condensing the light emitted from the light source 20 on the optical disc 3 will be described.
Is in the range of 0.5 <NA ≦ 0.6. By setting the numerical aperture NA of the objective lens 25 in a range of 0.5 <NA ≦ 0.6, the substrate thickness of the optical disk 3 (here, 1.
(2 mm) without changing the size of the pits while maintaining compatibility with the current CD-R / RW, thereby achieving a higher recording density than the current CD-R / RW.

The RF signal processing unit 5 performs a reproduction signal (RF signal), a focus error signal, a tracking error signal, and a groove GR on the optical disc 3 based on the voltage signal supplied from the photodetector 27 of the optical head 4. The wobble signal obtained from the wobble is generated. The reproduction signal generated by the RF signal processing unit 5 is subjected to a predetermined process such as an equalizing process or a binarization process, and then subjected to an EFM.
The data is supplied to the decoder 6. The wobble signal generated by the RF signal processing unit 5 is an ATIP (Absolute Time In P
The focus error signal and the tracking error signal are supplied to the re-groove decoder 7 and the servo controller 9 respectively.

The EFM decoder 6 performs EFM demodulation on the reproduction signal supplied as digital data from the RF signal processing unit 5 and performs error correction processing. EFM decoder 6
The data subjected to the EFM demodulation and the error correction processing is supplied to the host computer or the like via the interface 14 as reproduction data. This allows
An external computer or the like can receive a signal recorded on the optical disc 3 as a reproduction signal.

The ATIP decoder 7 includes an RF signal processor 5
It generates an ATIP signal from the wobble signal supplied from, and detects a linear velocity of the optical disc 3 to generate a constant linear velocity (CLV) signal for keeping the linear velocity constant. This CLV signal is supplied to the spindle motor 2 via the spindle driver 8. As a result, the spindle motor 2 rotates the optical disc 3 so that its linear velocity becomes constant. Specifically, the spindle motor 2 rotates the optical disc 3 at a linear velocity in a range from 0.8 m / sec to 1.0 m / sec. Further, the ATIP signal includes address information on the disk, so that the position on the disk can be known.

The servo controller 9 receives the focus error signal supplied from the RF signal processor 5 and drives the two-axis driver 10 on which the optical head 4 is mounted in accordance with the focus error signal. Accordingly, the focus control of the optical head 4 is performed in a direction perpendicular to the optical disk 3. Further, the servo control unit 9 receives the tracking error signal supplied from the RF signal processing unit 5, and responds to the tracking error signal to the two-axis driver 1.
0 to drive the optical head 4
Tracking control in the direction perpendicular to the track.

When recording data is supplied from a host computer or the like via the interface 14, the EFM encoder 11 performs EFM modulation processing and the like on the recording data to generate a write signal.
Then, the write signal is transferred to the write strategy circuit 1
2 to the optical head 4. Then, the optical head 4 responds to the supplied write signal by
The intensity of the laser light emitted from the optical disk 3 is generated and irradiated on the optical disc 3 and recorded as pits on the recording layer.

An APC (Auto-Power-Control) circuit 13 measures the light receiving power of the light beam emitted from the light source 20 of the optical head 4, and drives the light source so that the light receiving power becomes a predetermined value. Control the current.

Next, the optical head 4 mounted on the recording / reproducing apparatus 1 as described above will be described. The optical head 4 includes a light source 20 and a diffraction grating 2 as shown in FIG.
1, a beam splitter 22, and a collimator lens 23
, A quarter-wave plate 24, an objective lens 25, a multi-lens 26, and a photodetector 27.

The light source 20 emits light toward the optical disk 3 at the time of recording / reproducing. Specifically, the light source 20 is a semiconductor laser that emits linearly polarized laser light having a wavelength λ of 780 (± 10) nm. . The light source 20 emits a laser beam of a constant output when reproducing an information signal from the optical disk 3, and when recording an information signal on the optical disk 3, the intensity of the emitted laser light depends on the signal to be recorded. Is modulated.

The laser light emitted from the light source 20 first enters the diffraction grating 21 and is diffracted by the diffraction grating 21. This diffraction grating 21 has a so-called DP
In order to enable tracking servo by the P method (Deferential Push Pull) or the three spot method, the laser beam is divided into at least three parts. The tracking servo will be described in detail in the second embodiment.

Then, the zero-order light and ± first-order light (hereinafter collectively referred to as “incident laser light”) diffracted by the diffraction grating 21 pass through the beam splitter 22 and are collimated by a collimator lens 23. Incident on. here,
The collimator lens 23 includes, for example, two spherical lenses 2
3a and 23b are stuck together.

The laser light incident on the collimator lens 23 is collimated by the collimator lens 23.

The collimator lens 23 is a combination lens formed by combining the two lenses 23a and 23b as described above, and also has a function as a chromatic aberration correction lens. In such a chromatic aberration correction lens in which two lenses are combined, two light beams having different wavelengths have the same focal length. Thereby, most of the chromatic aberration can be removed.

Then, the incident laser light emitted from the collimator lens 23 enters the objective lens 25 via the quarter-wave plate 24. Here, the incident laser light is 1 /
When the light passes through the four-wavelength plate 24, the light is in a circularly polarized state.

Here, the objective lens 25 focuses the incident laser light on the recording layer of the optical disc 3. That is, the incident laser light that has been made into a circularly polarized state by the quarter-wave plate 24 is condensed by the objective lens 25 and enters the recording layer of the optical disc 3 via the light transmission layer 3 b of the optical disc 3.

In the optical head 4 according to the present invention,
When the numerical aperture NA of the objective lens 25 is 0.5 <NA ≦ 0.6.
The range has been made.

In the current recording / reproducing of a CD-R / RW, a reproduction-only optical disk apparatus has a numerical aperture of 0.2.
An optical system having an objective lens of about 45 is used,
An optical system provided with an objective lens having a numerical aperture of about 0.50 has been used for a recordable optical disk device.

The inventors of the present invention have made intensive studies to achieve compatibility with the current CD-R / RW and stable recording and reproduction on the double-density optical disc 3D.
By keeping the numerical aperture NA of 5 in the range of 0.5 <NA ≦ 0.6, compatibility with the current CD-R / RW can be maintained without changing the substrate thickness of the optical disk (here, 1.2 mm). While reducing the size of the pit,
-It has been conceived that a higher recording density can be realized than R / RW.

When NA ≦ 0.5, the current CD-R /
Although it is compatible with RW and has a large tilt margin, it cannot increase the recording density. In addition, the current CD-R
Although reproduction is not a problem in terms of compatibility with / RW, especially in the recording of a CD-RW having a phase change film, the beam width becomes small, so that the current CD-ROM recorded at NA = 0.50 is used.
When the RW disk is overwritten by a pickup having a large numerical aperture, there is a problem that a peripheral portion remains without being overwritten.

In the case of 0.6 <NA, the recording density is easily increased, but the tilt margin is very small, which is not practical. In addition, the influence of the deterioration of jitter on the warpage of the disk increases. In addition, CD
In -RW, a phase change film is used as a recording film.
When the numerical aperture NA of the objective lens 25 is increased, that is, when the laser spot diameter is reduced, the phase change film is heated to a higher temperature. Since the characteristics of the phase change film greatly change depending on the temperature, if a temperature higher than the set range is applied to the phase change film, the characteristics of the phase change film may be deteriorated, which is not preferable.

Therefore, the numerical aperture NA of the objective lens 25 is
By setting the range of 0.5 <NA ≦ 0.6, the current CD-
While having compatibility with R / RW, it is possible to increase the tilt margin and increase the recording density. In the above range, the numerical aperture NA of the objective lens 25 is 0.5
It is desirable to set it to 5.

As described above, the incident laser light condensed by the objective lens 25 and incident on the recording layer of the optical disc 3 is
The light is reflected by the recording layer and becomes return light. The return light follows the original optical path, passes through the objective lens 25, and then enters the quarter-wave plate 24. The return light is transmitted through the quarter-wave plate 24 to become linearly polarized light rotated by 90 degrees with respect to the forward polarization direction. Thereafter, the return light is converged by the collimator lens 23. After
The light enters the beam splitter 22 and is reflected by the beam splitter 22.

The return light reflected by the beam splitter 22 passes through a multi-lens 26 and is detected by a photodetector 27. Here, the multi-lens 26 is a lens whose entrance surface is a cylindrical surface and whose exit surface is a concave surface. The multi-lens 26 is for giving astigmatism to return light to enable focus servo by a so-called astigmatism method.

The photodetector 27 for detecting the return light to which the astigmatism is given by the multi-lens 26 includes, for example, six photodiodes. The photodetector 27 outputs an electric signal corresponding to the light intensity of the return light incident on each photodiode, performs predetermined arithmetic processing on the electric signal, and performs an RF signal processing unit. 5 is output.

A phase-change recording film was provided under the same conditions except that the numerical aperture NA of the objective lens of the optical head was changed as shown in the following table, using the optical recording / reproducing apparatus having the above-described configuration. The recording and reproduction of the test signal were performed on the CD-RW. Then, the recording density, the reproduction compatibility with the current CD, and the tilt margin were evaluated.

In the evaluation, a case where the required characteristics were sufficiently satisfied was evaluated as ◎, and it cannot be said that the characteristics were satisfied. In this case, it was marked as ○. When stable recording and reproduction could not be performed, it was evaluated as x. Table 1 shows the results.

[0069]

[Table 1]

As is clear from Table 1, when NA ≦ 0.5, compatibility with the current CD is provided and the tilt margin is large, but the recording density cannot be increased. In the case of 0.6 <NA, the recording density is easily increased, but the tilt margin is very small, and the influence of the deterioration of jitter on the warpage of the disk is increased.

Therefore, the numerical aperture NA of the objective lens is set to 0.1.
It can be seen that by setting the range of 5 <NA ≦ 0.6, it is possible to increase the tilt margin and increase the recording density while maintaining compatibility with the current CD. It is optimal that the numerical aperture NA is 0.55 in the above range.

<Second Embodiment> Next, the second embodiment of the present application will be described.
An embodiment will be described. FIG. 3 shows the configuration of an optical disk drive 100 as an optical disk drive.

The optical disk 101 (101S, 101D) handled by the drive 100 has a spirally formed groove GR on the data recording surface, similarly to the optical disk 3 in the first embodiment described above. Recording and reproduction of data are performed using the groove GR as a track. The optical disk 3 described above also has other configurations.
Since it is the same as (3S, 3D), detailed description is omitted.

In this drive 100 as well, a disk 101S having a track pitch Tp of 1.6 μm,
Disk 10 having a track pitch Tp of 1.07 μm
Both 1D are handled.

The drive 100 has a disk 101
Spindle motor 1 for rotating the motor at a constant linear velocity
02, an optical pickup 103 composed of a semiconductor laser, an objective lens, a photodetector, etc., a laser driver 104 for controlling light emission of the semiconductor laser of the optical pickup 103, and processing of an output signal of a photodetector constituting the optical pickup 103. And an RF amplifier unit 105 for obtaining a reproduction RF signal S _RF , a tracking error signal S _TE , a focus error signal S _FE, and a wobble signal S _WB corresponding to the wobble of the groove GR.

A laser beam (not shown) from a semiconductor laser constituting the optical pickup 103 is
Of the optical pickup 10
Irradiate the photodetector constituting 3. In the RF amplifier unit 105, the tracking error signal _STE is formed by the DPP method, and the focus error signal _SFE is formed by the astigmatism method (astigmatism method).

The drive 100 includes the RF amplifier 1
05 reproduced RF signal S _RFWaveform
Signal to obtain CD data by performing processing such as conversion and signal detection
Processing circuit 106 and CD encoding / decoding described later
Recording compensation for the recording data RD output from the
Compensation circuit 107 for supplying the laser driver 104 with
And Semiconductor laser for optical pickup 103
The laser beam output from the
Is modulated by the data RD.
Recording data RD is recorded.

The drive 100 has a CD encoding / decoding unit 111 and a CD-ROM encoding / decoding unit 112. During reproduction, the CD encode / decode unit 111 applies EFM (Eight to Fourt) to the CD data output from the RF signal processing circuit 106.
een Modulation) and CIRC (Cr
The CD-ROM data is obtained by performing an error correction process using an oss Interleave Reed-Solomon Code). Also,
This CD encoding / decoding unit 111
Parity by CIRC is added to the CD-ROM data output from the CD-ROM encoding / decoding unit 112, and EFM modulation processing is performed to obtain CD data. Further, the CD data is subjected to NRZI (Non Re
turn to Zero Inverted) Converted data R
D is obtained.

CD-ROM encode / decode section 11
Numeral 2 is for obtaining read data by performing descrambling processing, error correction processing, and the like on CD-ROM data output from the CD encoding / decoding unit 111 during reproduction. The CD-ROM encoding / decoding unit 112 performs a process of adding parity for error correction, a scrambling process, and the like to write data received from a SCSI / buffer controller described later at the time of recording, thereby performing CD-ROM data encoding. Is what you get. The CD-ROM encoding / decoding unit 112 has a RAM as a working memory for performing the above-described processing.
(Random Access Memory) 113 is connected.

The drive 100 receives a command from the host computer and supplies it to the system controller. Further, at the time of reproduction, the drive 100 outputs read data output from the CD-ROM encode / decode unit 112 via a RAM 114 as a buffer memory. And write data transferred from the host computer during recording to the RAM 114.
(Small Computer System Interface) for supplying to the CD-ROM encode / decode unit 112 via the
rface) / buffer controller 115.

The drive 100 includes the RF amplifier 1
05 based on the focus error signal S _FE and the tracking error signal S _TE is output from the focus / tracking servo control circuit 1 for performing focus servo and tracking servo of the optical pickup 103
21, a feed servo control circuit 122 for moving the optical pickup 103 at the time of access, and a spindle servo control circuit 123 for controlling the rotation speed of the spindle motor 102 to a predetermined value.

The operation of the servo control circuits 121 to 123 is as follows.
It is controlled by a mechanical controller 124 having a CPU (central processing unit).

The drive 100 has a system controller 125 for controlling the operation of the entire system. This system controller 125 has a CPU
It has.

The drive 100 includes the RF amplifier 1
Wobble signal S output from the signal 05 _WBMore ATIP
It has a wobble processing unit 131 for decoding a signal.
You. The ATIP signal obtained by the wobble processing unit 131
The signal is transmitted through the CD encode / decode
Nical controller 124 and system controller
125 and used for various controls.

Next, the optical pickup 103 will be described in detail. FIG. 4 shows the configuration of the optical system of the optical pickup 103.

The optical pickup 103 includes a semiconductor laser 152 for obtaining a laser beam 151 and a collimator lens 15 for shaping the laser beam 151 output from the semiconductor laser 152 from parallel light to divergent light.
And 3. Specifically, the semiconductor laser 152 emits laser light having a wavelength λ of 780 (± 10) nm. Between the semiconductor laser 152 and the collimator lens 153, a three-beam grating is arranged a (diffraction grating) 154 for forming, in the grating 154, a main beam _{B m} according to zero-order light,
First and second side beams B _s1 , B by ± first order light
_s2 is formed.

The optical pickup 103 includes a beam splitter 155, a １ ／ wavelength plate 161, an objective lens 156 for irradiating a recording surface of the disk 101 with a laser beam, and a front APC (Auto Power Control). And a photodetector 157. The objective lens 156 has a numerical aperture NA as described in the first embodiment.
Is used in the range of 0.5 <NA ≦ 0.6. Here, an objective lens having a numerical aperture NA of 0.55 is used. A part of the laser beam incident on the beam splitter 155 from the collimator lens 153 passes through the semi-permeable membrane 155a and is incident on the objective lens 156,
Another part is reflected by the semi-permeable film 155a and enters the photodetector 157. In addition, a part of the laser beam incident on the beam splitter 155 from the objective lens 156 is reflected by the semi-permeable film 155a, and further reflected on the reflection surface 155b.
And is emitted to the outside.

The optical pickup 103 is provided with a condensing lens 15 for condensing a laser beam reflected by the reflection surface 155b of the beam splitter 155 and emitted to the outside.
8, a photodetector 160 on which the laser beam emitted from the condenser lens 158 is incident, and a multi-lens 159 disposed between the condenser lens 158 and the photodetector 160. Multi lens 159
Is composed of a combination of a concave lens and a cylindrical lens. The reason why the cylindrical lens is used is to obtain the focus error signal _SFE by a well-known astigma method.

[0089] Also not described above, on the disk 101, a main spot SP _m of the main beam _{B m,} the side beams _{B s1, B s2} side spot _SP s1 by, S
P _{s 2} is formed. In this case, the side spot SP
_The points _s1 and SP _s2 are formed at positions spaced apart from the main spot SP _m by a predetermined distance in one radial direction and the other direction. Then, the laser beam emitted from the grating 154 is shaped into parallel light by the collimator lens 153, and thereafter is incident on the beam splitter 155. The laser beam transmitted through the semi-permeable film 155a of the beam splitter 155 is applied to the recording surface of the disk 101 via the quarter-wave plate 161 and the objective lens 156. In this case, on the disk 101, as shown in FIG. 3, and the spot SP _m of the main beam _{B m,} the side beams _B s1, B
_s2 by the spot _SP s1, and the _{SP s2} is formed.

The laser beam reflected from the recording surface of the disk 101 is incident on the beam splitter 155 via the quarter-wave plate 161 via the objective lens 156.
The light is sequentially reflected by the semi-permeable film 155a and the reflection surface 155b. The laser beam emitted from the beam splitter 155 enters the photodetector 160 via the condenser lens 158 and the multi lens 159.

The photodiode units 160M, 160S ₁ and 160S ₂ constituting the photo detector 160 include:
As shown in FIG. 5, each above-mentioned spot _SP m formed on the disk 101 _on, SP s1, _{SP s2} spot _SP m by the reflected laser beam ', SP
_s1 'and SP _s2 ' are formed.

Here, the photodiode section 160M is structured.
Four photodiodes D to be formed_a~ D_dDetection signal
S_a~ S_dAnd the photodiode section 160S₁Configure
Two photodiodes D_e, D_fThe detection signal of
_e, S_fAnd the photodiode section 160S₂Make up
Two photodiodes D_g, D_hDetection signal
S _g, S_h, The RF amplifier unit 105 (see FIG. 3)
), The reproduced RF signal is calculated by
S_RFAnd focus error signal S_FEIs obtained.
That is, S_RF= (S_a+ S_b+ S_c+ S_d), S
_FE= (S_a+ S_c)-(S_b+ S_d).

[0093] Further, the RF amplifier unit 105, the detection signal _S a, _S detection signal _S b than the addition signal of the _d, push-pull signal _{S ppm} by the reflected light from the main spot SP _m addition signal is subtracted the _{S c} Is generated, and a wobble signal _SWB is extracted from the push-pull signal _Sppm by a high-pass filter.

[0094] Further, the RF amplifier unit 105, the circuit of Figure 12 described above, the tracking error signal _{S TE} by the DPP method is calculated. That is, the subtractor 221
In M, from the addition signal of the detection signal _{S a} and the detection signal _{S d,} is subtracted sum signal of detection signals _{S b} and the detection signal _{S c} is obtained push-pull signal _{S ppm} by the reflected light from the main spot SP _m Can be Subtractor 221S
_1, is subtracted the detection signal _{S e} from the detection signal _{S f,} the push-pull signal _{S PPS1} by the reflected light from the side spot _{SP s1} is obtained. Further, the subtractor 221S ₂
In is subtracted detection signal _{S g} from the detection signal _{S h} is, push-pull signal _{S pps2} by the reflected light from the side spot _{SP s2} is obtained.

[0095] Further, in the adder 222, the gain push-pull signal received through the amplitude adjuster 223 for G2 _{S pps2} and push-pull signal _{S PPS1} and are added to produce signal _{S s} is obtained. Then, the subtractor 224, the push-pull signal _{S ppm} than the gain G1 addition signal _{S s} which is through the amplitude adjuster 225 is subtracted, the tracking error signal S
_TE is obtained.

Here, the track pitch Tp is 1.6 μm
The case where the disk 101S is mounted
I do. In this case, as shown in FIG.
SP _s1, SP_s2Is the main spot SP_mAgainst
In one direction and the other in the radial direction.
Formed at a distance of 1.3 / 2 μm (146 °).
It is. Therefore, the main spot SP_mRadial direction of
Push-pull signal S for position_ppm,
S_pps1, S_pps2Are shown in FIGS. 6B, C and D, respectively.
Changes as shown. In this case, the push-pull signal S
_pps1And push-pull signal S _pps2And the inverse relationship
The tracking error signal S_TEThe figure
As shown in FIG. 6E, it has a sufficient amplitude.

Next, the track pitch Tp is 1.07 μm
The case where the disk 101D is mounted
I do. In this case, as shown in FIG.
SP _s1, SP_s2Is the main spot SP_mAgainst
In one direction and the other in the radial direction.
Formed at a distance of 1.3 / 2 μm (218 °).
It is. Therefore, the main spot SP_mRadial direction of
Push-pull signal S for position_ppm,
S_pps1, S_pps2Are shown in FIGS. 7B, C and D, respectively.
Changes as shown. In this case, the push-pull signal S
_pps1And push-pull signal S _pps2And the inverse relationship
The tracking error signal S_TEThe figure
As shown in FIG. 7E, it has a sufficient amplitude.

Note that, although not described above, when the disk 101S having the track pitch Tp of 1.6 μm is mounted,
Disk 10 having a track pitch Tp of 1.07 μm
Tracking error signal S
The amplitude of _TE changes. Therefore, which disk 1
For example, the gain of the subtractor 224 and the like in the circuit shown in FIG. 12 may be controlled in accordance with the track pitch so that the amplitude of the tracking error signal is constant even when the 01 is mounted.

Next, the optical disk drive 10 shown in FIG.
The operation of 0 will be described.

When a data write command is supplied from the host computer to the system controller 125, data writing (recording) is performed. In this case, the write data transferred from the host computer is transmitted from the SCSI / buffer controller 115 to the CD-ROM.
The data is supplied to the ROM encode / decode unit 112. The CD-ROM encoding / decoding unit 112
In addition, a process of adding parity for error correction, a scrambling process, and the like are performed on the write data and the CD-ROM
Data is generated.

CD-ROM encode / decode section 11
The CD-ROM data generated in step 2 is supplied to the CD encoding / decoding unit 111. The CD encoding / decoding unit 111 adds a parity by CIRC to the CD-ROM data and
CD data is generated by performing FM modulation processing, and NRZI conversion processing is performed on the CD data to generate recording data RD.

The recording data RD is recorded-compensated by the recording compensation circuit 107 and supplied to the laser driver 104. Therefore, the laser beam output from the semiconductor laser of the optical pickup 103 is modulated by the recording data RD whose recording has been compensated, and the recording data RD is recorded on the disk 101.

Next, when a data read command is supplied from the host computer to the system controller 125, data reading (reproduction) is performed. The reproduction RF signal reproduced by the optical pickup 103 is subjected to processing such as waveform equalization by the RF signal processing circuit 106 to obtain CD data. Then, the CD data is supplied to the CD encode / decode unit 111. In the CD encoding / decoding unit 111, the reproduction data is subjected to EFM demodulation processing and error correction processing by CIRC.
D-ROM data is obtained.

The CD-ROM data obtained by the CD encoding / decoding section 111 is
The data is supplied to the decoding unit 112 and subjected to descrambling processing, error correction processing, and the like, thereby obtaining read data. Then, the read data is transferred to the host computer at a predetermined timing through the RAM 114 as a buffer memory under the control of the SCSI / buffer controller 115.

As described above, in the present embodiment,
And side spot SP_s1, SP _s2Is the main sport
SP_m1.6 / 2 μm in the radial direction
Shorter and separated by a distance longer than 1.07 / 2 μm
It is formed in the position where it was. Therefore, the track pitch Tp is
When a disk 101S of 1.6 μm is mounted,
Having a track pitch Tp of 1.07 μm
In both cases where 101D is mounted, the DPP method
Tracking error signal S_TEWith sufficient amplitude
be able to. Therefore, in the present embodiment,
A disk 101S having a track pitch Tp of 1.6 μm
In both cases, a disc 1 having a track pitch Tp of 1.07 μm
01D can be handled.

In the above embodiment, D
Tracking error signal S by PP method _TEWhat produces
However, in the present invention, tracking is performed by a three-spot method.
Error signal S_TEAlso applies to those that generate
be able to.

The tracking error signal S is obtained by the three-spot method.
_Even if it generates _TE , the optical pickup 103
Is configured as shown in FIG. 4, and on the disk 101,
As shown in FIG. 8, the spot S of the main beam B _m
P _m and the spot S by the side beams _{B s1, B s2}
P _s1 and SP _s2 are formed.

[0108] Here, 3 with those obtaining tracking error signal _{S TE} by spot method, which disc 101S and the track pitch Tp track pitch Tp is 1.6μm handles both disc 101D is 1.07μm , So the side spot SP
_s1 and SP _s2 are shorter than メ イ ン of the maximum track pitch (1.6 μm) in the radial direction with respect to the main spot SP _m and are the minimum track pitch (1.07).
.mu.m).

Here, the side spots SP _s1 , SP
_{When s2} is formed at a position spaced apart from the main spot SP _m by 1.6 / 4 μm in the radial direction, the disk 101S having the track pitch Tp of 1.6 μm.
, The amplitude of the tracking error signal _STE by the three-spot method becomes maximum. When the side spots SP _s1 and SP _s2 are formed at a position apart from the main spot SP _m by 1.07 / 4 μm in the radial direction, the track pitch Tp is 1.07 μm.
, The amplitude of the tracking error signal _STE by the three-spot method becomes maximum.

For example, the side spots SP _s1 , SP
_s2 is formed to correspond to the disk 101X having the track pitch Tp of 1.3 μm. That is, the side spots SP _s1 and SP _s2 are
The main spot SP _m, in one direction and the other direction of the radial direction, is formed in a position separated by 1.3 / 4 [mu] m. Such side spots SP _s1 and SP
The position adjustment of _s2 can be performed by adjusting the angle of the grating 154.

The photodetector 160 is shown in FIG.
As shown, one quadrant photodiode section 160M
And two photodiode units 160_S1, 160_S2
It is composed of The configuration of this photodetector 160
Photodiode section 160M, 160S₁, 160S
₂Are the spots formed on the disc 101, respectively.
SP_m, SP_s1, SP_s2Laser beam reflected by
Spot SP _m', SP_s1', SP_s2'But
It is formed.

Here, the photodiode section 160M is structured.
Four photodiodes D to be formed_a, D_dDetection signal
S_a, S_dAnd the photodiode section 160S₁Configure
Photodiode D_fThe detection signal of_fAnd
Photodiode section 160S₂Constituting the photodiode
D_eThe detection signal of_e, The RF amplifier unit 105
(Refer to FIG. 3)
RF signal S_RFAnd focus error signal S_FEGet
Can be That is, S_RF= (S_a+ S_b+ S _c+
S_d), S_FE= (S_a+ S_c)-(S_b+ S_d)
You.

[0113] Further, the RF amplifier unit 105, the detection signal _S a, _S detection signal _S b than the addition signal of the _d, push-pull signal _{S ppm} by the reflected light from the main spot SP _m addition signal is subtracted the _{S c} Is generated, and a wobble signal _SWB is extracted from the push-pull signal _Sppm by a high-pass filter.

In the RF amplifier section 105, the tracking error signal _STE is calculated by the three-spot method by the circuit shown in FIG. That is, i.e., the subtractor 226, the detection signal _{S e} from the detection signal _{S f} is subtracted, the tracking error signal _{S TE} is obtained.

Here, the track pitch Tp is 1.6 μm
The case where the disk 101S is mounted
I do. In this case, as shown in FIG.
SP _s1, SP_s2Is the main spot SP_mAgainst
In one direction and the other in the radial direction.
Formed at a position separated by 1.3 / 4 μm (73 °)
You. Therefore, the main spot SP_mRadial position of
The main signal S_m(Detection signal S_a~ S_dAddition
Signal), detection signal S_e, S_f9B, respectively.
It changes as shown in C and D. In this case, the detection signal S_e
And the detection signal S_fIs closer to a reversed phase relationship,
Racking error signal S_TEIs, as shown in FIG. 9E,
It has a sufficient amplitude.

Next, the track pitch Tp is 1.07 μm
The case where the disk 101D is mounted will be described. In this case, as shown in FIG. 10A, the side spots SP _s1 and SP _s2 are only 1.3 / 4 μm (109 °) _apart from the main spot SP _m in one radial direction and the other. It is formed at a remote position. Therefore, with respect to the radial direction position of the main spot SP _m, main signal _{S m,} the detection signal _S e, S
_f changes as shown in FIGS. 10B, 10C and 10D, respectively. In this case, as approaching the opposite phase relationship to the detection signal S _e and the detection signal S _f, the tracking error signal S
_{The TE} has a sufficient amplitude as shown in FIG. 10E.

Note that, even though not described above, when the disk 101S having the track pitch Tp of 1.6 μm is mounted,
Disk 10 having a track pitch Tp of 1.07 μm
Tracking error signal S
The amplitude of _TE changes. Therefore, which disk 1
For example, the gain of the subtractor 226 or the like in the circuit shown in FIG. 14 may be controlled in accordance with the track pitch so that the amplitude of the tracking error signal becomes constant even when 01 is mounted.

As described above, the side spots SP _s1 , S
P _s2 is shorter than 1.6 / 4 μm and 1.07 / 4 μm in the radial direction with respect to main spot SP _m .
By forming them at a position separated by a longer distance, when the disk 101S having the track pitch Tp of 1.6 μm is mounted and when the track pitch Tp is 1.07 μm
, The tracking error signal _STE by the three spot method
Can be obtained with a sufficient amplitude. Therefore, along with the disk 101S having the track pitch Tp of 1.6 μm,
Disk 101D having a track pitch Tp of 1.07 μm
Can handle both.

In the above-described embodiment, the disk 101S having the track pitch Tp of 1.6 μm is used.
And a disk 101D having a track pitch Tp of 1.07 μm is shown. However, the present invention can be similarly applied to a disk that handles more types of disks 101 having different track pitches. The minimum track of its case, the position of the side spot SP _s1, SP _{s 2} the amplitude of the tracking error signal becomes maximum at the maximum of the track pitch of the different track pitches to the first position, different track pitches from one another When the position of the side spots SP _{s 1} and SP _s2 at which the amplitude of the tracking error signal is the maximum at the pitch is the second position, the side spot S
The P _{s1, SP s 2} may be formed between the first and second positions. This makes it possible to obtain a tracking error signal having a sufficient amplitude even if the track pitch changes.

Further, in the above-described embodiment, the case of handling a plurality of optical disks 101S and 101D having recording tracks formed with different track pitches has been described, but recording tracks formed with different track pitches are used. A disk 101W having a plurality of recording areas can be handled. For example, a disk 101W having a recording area with a track pitch Tp of 1.6 μm on the inner circumference side and a recording area with a track pitch Tp of 1.07 μm on the outer circumference side can be handled.

In the above-described embodiment, the present invention is applied to the optical disk drive 100. However, the present invention is directed to a plurality of optical disks having at least recording tracks formed at different track pitches or different optical disks. The present invention can be applied to an optical disk drive that handles an optical disk having a plurality of recording areas having recording tracks formed at a track pitch.

[0122]

According to the present invention, in an optical recording / reproducing apparatus,
By defining the numerical aperture of the objective lens of the optical pickup, it is possible to realize a system having a higher capacity than the current CD by reducing the size of the pits while maintaining compatibility with the current CD.

Further, according to the present invention, a tracking error signal having a sufficient amplitude can be obtained even if the track pitch changes, and a plurality of optical discs having recording tracks formed at different track pitches or different optical discs having different track pitches can be obtained. An optical disk having a plurality of recording areas having recording tracks formed at a track pitch can be handled without changing the optical system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of an optical recording / reproducing apparatus according to the present invention.

FIG. 2 is a schematic diagram illustrating a configuration example of an optical head mounted on an optical recording / reproducing apparatus according to the present invention.

FIG. 3 is a block diagram illustrating a configuration of a CD-R drive.

FIG. 4 is a diagram showing a configuration of an optical system of the optical pickup.

FIG. 5 is a diagram showing a relationship (DPP method) between spots on a disc and spots on a photodetector.

FIG. 6 shows a spot position when a disc having a track pitch Tp = 1.6 μm is mounted (the side spot position is Tp = 1.
3μm and corresponds to (DPP method)), showing the various parts waveforms according to the generation of the tracking error signal _{S TE.}

FIG. 7 shows a spot position when a disc having a track pitch Tp = 1.07 μm is mounted (side spot position is Tp = 1.07 μm).
FIG. 3 is a diagram showing waveforms of each part relating to generation of a tracking error signal STE (corresponding to 1.3 μm (DPP method)).

FIG. 8 is a diagram showing the relationship between spots on a disk and spots on a photodetector (three-spot method).

FIG. 9 shows a spot position when a disc with a track pitch Tp = 1.6 μm is mounted (the side spot position is Tp = 1.
3A and 3B (corresponding to a three-spot method) and waveforms of respective parts relating to generation of a tracking error signal _STE .

FIG. 10 shows a spot position when a disc having a track pitch Tp = 1.07 μm is mounted (side spot position is Tp = 1.07 μm).
FIG. 3 is a diagram showing waveforms of 1.3 μm (corresponding to a three-spot method) and waveforms of various parts related to generation of a tracking error signal _STE .

FIG. 11 is a diagram showing a relationship between a spot on a conventional disk and a spot on a photodetector (DPP method).

FIG. 12 is a diagram showing a circuit for generating a tracking error signal by the DPP method.

FIG. 13 is a diagram showing the relationship between a spot on a conventional disk and a spot on a photodetector (three-spot method).

FIG. 14 is a diagram showing a circuit for generating a tracking error signal by a three-spot method.

FIG. 15 shows a spot position when a disc having a track pitch Tp = 1.6 μm is mounted (side spot position is Tp = 1.6 μm).
1.6μm and corresponds to (DPP method)), showing the various parts waveforms according to the generation of the tracking error signal _{S TE.}

FIG. 16 shows a spot position when a disc with a track pitch Tp = 1.07 μm is mounted (side spot position is Tp = 1.07 μm).
1.6μm and corresponds to (DPP method)), showing the various parts waveforms according to the generation of the tracking error signal _{S TE.}

FIG. 17 shows a spot position when a disc having a track pitch Tp = 1.6 μm is mounted (side spot position is Tp = 1.6 μm).
FIG. 10 is a diagram showing waveforms of respective parts related to the generation of the tracking error signal STE (corresponding to 1.6 μm (three spot method)).

FIG. 18 shows a spot position when a disc having a track pitch Tp = 1.07 μm is mounted (side spot position is Tp = 1.07 μm).
And 1.6μm corresponding to (3 spot method)), showing the various parts waveforms according to the generation of the tracking error signal _{S TE.}

[Explanation of symbols]

1 optical recording / reproducing device, 2 spindle motor, 3
Optical disc, 4 optical head, 5 RF signal processing unit, 6 EFM decoder, 7 ATIP decoder,
8 spindle driver, 9 servo controller, 1
0 2-axis driver, 11 EFM encoder, 12
Write strategy circuit, 13 APC circuit

Claims (10)

[Claims] 1. An optical recording / reproducing apparatus that handles a plurality of information recording media having at least recording tracks formed at different track pitches or an information recording medium having a plurality of recording areas having recording tracks formed at different track pitches. An apparatus, comprising: a rotation driving unit that rotationally drives an information recording medium; an optical head that records and / or reproduces an information signal by irradiating light to the information recording medium that is rotationally driven by the rotation driving unit. A signal processing circuit for processing a signal detected by the optical head, the optical head comprising: a light source for emitting light; and an objective lens for condensing light from the light source on the information recording medium. Signal detection means for receiving a return light reflected by the information recording medium and detecting a signal, wherein the objective lens has a numerical aperture NA, .5 <NA ≦ 0.
6. An optical recording / reproducing apparatus, wherein the range is 6. 2. The optical recording / reproducing apparatus according to claim 1, wherein the wavelength of the light emitted from the light source is about 780 nm. 3. The information recording medium according to claim 1, wherein the first information recording medium has a track pitch in a range of 1.0 μm to 1.2 μm, and the second information recording medium has a track pitch of 1.6 μm. The optical recording / reproducing apparatus according to claim 1, wherein: 4. The first information recording medium has a shortest pit length in a range of 0.555 μm to 0.694 μm, and the rotation drive means controls the information recording medium in a range of 0.8 m / sec to 1.0 m. 4. The optical recording / reproducing apparatus according to claim 3, wherein the optical recording / reproducing apparatus is driven to rotate at a linear velocity in the range of / sec. 5. The numerical aperture NA of the objective lens is 0.55.
The optical recording / reproducing apparatus according to claim 1, wherein: 6. Light is applied to at least a plurality of information recording media having recording tracks formed with different track pitches or an information recording medium having a plurality of recording areas having recording tracks formed with different track pitches. An optical head device for recording and / or reproducing an information signal by irradiating, wherein the optical head comprises: a light source for emitting light; and an objective lens for condensing light from the light source on the information recording medium. Signal detection means for receiving a return light reflected by the information recording medium and detecting a signal, wherein the objective lens has a numerical aperture NA of 0.5 <NA ≦ 0.
6. An optical head device having a range of 6. 7. The optical head device according to claim 6, wherein the wavelength of the light emitted from the light source is about 780 nm. 8. The information recording medium according to claim 1, wherein the first information recording medium has a track pitch in a range of 1.0 μm to 1.2 μm, and the second information recording medium has a track pitch of 1.6 μm. The optical head device according to claim 6, wherein 9. The first information recording medium has a shortest pit length in the range of 0.555 μm to 0.694 μm, and the second information recording medium has a shortest pit length of about 0.83 μm.
9. The optical head device according to claim 8, wherein the thickness is 3 [mu] m. 10. The numerical aperture NA of the objective lens is 0.5.
7. The optical head device according to claim 6, wherein