JP2005222646A - Optical head device and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems in an optical disk having a guide groove, wherein it is difficult to deal with the optical disk having different track pitches, when focusing control is performed without being affected by a diffracted light from a guide groove, and wherein it is difficult to control precise tracking when the tracking control is performed without effect of offset, because the calculation for removing the offset component from two tracking error signals having opposite phases is performed. <P>SOLUTION: Three light convergence spots are formed, with respect to the direction in which the optical disk is scanned, by irradiating the optical disk 10 with three laser beams 7a, 7b, and 7c, wherein two light convergent spots 11b and 11c are constituted so as to be composed of the central main spot 21a and two sub spots 21b and 21c on both sides, with respect to the direction in which the optical disk is scanned. The sub spots are provided with a phase difference of 180 degrees, with respect to the main spot. The amount of light of the main spot is equal to that of the sub spots. The focusing control and the tracking control are made by using the reflected lights therefrom. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical head device for optically recording or reproducing information and an optical disk device using the same.

  An optical disc device that records or reproduces digital data by applying a laser beam to the recording surface of an optical recording medium (hereinafter referred to as an optical disc) can record large volumes as the semiconductor laser technology advances and microfabrication technology improves. Accordingly, it is becoming widespread not only in computer data recording but also in the fields of audio, video, and the like. Particularly in recent years, the amount of data handled, such as moving image information, has increased dramatically, and information signals (hereinafter referred to as pits) on the optical disk and rows (hereinafter referred to as tracks) in which pits are linearly connected in the rotation direction of the optical disk. ), The capacity of the optical disk device is further increased.

  In such a background, in order to accurately record on the optical disk or accurately reproduce the recorded information signal, a focusing control function for appropriately focusing the laser beam on a finer pit or traveling at high speed There is a need for an optical head device having a tracking control function for correctly following and scanning a track.

  There is an astigmatism method as one of the focusing control methods. This is because astigmatism is given by the cylindrical lens to the reflected light of the laser beam irradiated on the optical disk provided with guide grooves in advance, and a focusing error signal (hereinafter referred to as FES) is detected by a predetermined calculation from the shape. Control is performed. In this system, a disturbance signal is mixed into the FES due to the influence of diffracted light generated when the focused spot of the laser beam crosses the guide groove of the optical disk. For this reason, in conventional focusing control, a diffraction grating is used to form three condensing spots on the optical disc at intervals of an integral multiple of 1/2 the track pitch, and FES is detected from the reflected light from each condensing spot. At the same time, by utilizing the fact that the phase of the disturbance signal mixed in these three FESs is inverted, only the disturbance component is canceled to obtain an FES without the disturbance signal (for example, Patent Document 1). reference).

  There is a push-pull method as one of tracking control methods. This is a method of performing tracking control by the difference in intensity between the left and right light with respect to the scanning direction of the laser beam reflected from the optical disk. That is, when the laser beam irradiates off the track, the right and left light intensities are different. Therefore, the reflected light is detected by a light detector, and a tracking error signal (hereinafter referred to as TES) is calculated by calculating the difference between the left and right light amounts. Tracking control is performed. In this method, when an objective lens for condensing a laser beam on an optical disk moves in the radial direction of the optical disk (hereinafter referred to as a lens shift) or when the optical disk is tilted, an offset component is mixed into the TES, and tracking control is performed correctly. In the past, a differential push-pull method has been proposed.

  The principle of this differential push-pull method is as follows. Two optical spots are irradiated onto the optical disc so that the interval in the direction perpendicular to the scanning direction is half the track pitch. Then, it is known that the TES obtained by the push-pull method from the two focused spots each have an offset component in the same phase and an AC component in the opposite phase. Therefore, the TES obtained from the two spots is subtracted to cancel the offset component mixed in the TES, thereby obtaining the TES free from the influence of the offset component.

  However, in this method, it is necessary to set the interval in the direction perpendicular to the scanning direction of the two focused spots to half the track pitch, and therefore there is a problem that it is not possible to cope with different track pitches. In order to solve this problem, in the conventional tracking control, the first focused spot composed of two sub-spots having a phase difference of 180 degrees and the interval between the first focused spot and the direction orthogonal to the track are zero. The reflected light from the second focused spot (that is, the first focused spot and the second focused spot are arranged on the same track) is not affected by the offset component by the differential push-pull method. TES is calculated (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 1688631 (FIG. 1)

Japanese Patent Laid-Open No. 9-81942 (FIGS. 1, 6, and 11)

As described above, in the conventional focusing control method, there is a problem that it is difficult to cope with optical disks having different track pitches because the focused spots formed at intervals of half the track pitch are used.
Moreover, in the conventional tracking control method, the subtraction process is performed after adjusting the gain of the AC component of the TES including the offset component of the same phase obtained from the two focused spots and having the opposite phase. Since the offset component is canceled, the phase difference and gain difference between the two TESs due to the difference in the characteristics of the parts used and the difference in temperature characteristics are mixed as errors into the TES as they are. There is a problem that it is difficult to perform high-accuracy tracking control corresponding to an optical disc apparatus which is expected to have a transfer rate.
Further, in the conventional tracking control method, a region in which the period of the groove of the diffraction grating is inverted by 180 degrees is formed in the groove direction of the diffraction grating in order to give phase modulation to the laser beam (see FIG. 6 of Patent Document 2). Therefore, there is a problem that it is difficult to manufacture the diffraction grating, particularly the boundary portion of the region where the phase is changed, with high accuracy.

The present invention has been made to solve the above-described problems. As a first object,
It is an object of the present invention to provide an optical head device capable of focusing control without restriction on the track pitch and capable of highly accurate tracking control. A second object is to provide an optical disk device having such an optical head device.

  The optical head device according to the present invention is aligned with the first laser beam focused on the optical recording medium to form the first focused spot and the first focused spot in the scanning direction of the optical recording medium. Means for obtaining a second laser beam for forming a second focused spot, means for dividing the second focused spot into a main spot and a sub spot in the scanning direction of the optical recording medium, a sub spot with respect to the main spot Phase adding means for giving a phase difference of 180 degrees to the light quantity, light quantity setting means for making the light quantity of the main spot equal to the light quantity of the sub-spot, means for recording or reproducing data by the first focused spot, the second focused spot Focusing control means for detecting the intensity of the reflected light from the light with a split-type photodetector having a plurality of light receiving surfaces and performing focusing control by a predetermined calculation is provided.

  The optical head device according to the present invention includes a first laser beam that is focused and irradiated on an optical recording medium to form a first focused spot and a first focused spot in a direction in which the optical recording medium is scanned. Means for obtaining a second laser beam that forms a second focused spot side by side, means for dividing the second focused spot into a main spot and a sub spot in the direction of scanning the optical recording medium, Phase adding means for giving a phase difference of 180 degrees to the sub-spot, light quantity setting means for making the light quantity of the main spot equal to the light quantity of the sub-spot, means for recording or reproducing data by the first condensing spot, first collection Tracking control means for detecting the intensity of the reflected light from the light spot and the second focused spot with a split photodetector having a plurality of light receiving surfaces and performing tracking control by a predetermined calculation is provided. Than it is.

  The optical disc apparatus according to the present invention includes a first laser beam that is focused and irradiated on an optical recording medium to form a first focused spot, and a first focused spot in a direction in which the optical recording medium is scanned. Means for obtaining a second laser beam for forming a second focused spot side by side; means for dividing the second focused spot into a main spot and a sub spot in a scanning direction of the optical recording medium; Phase adding means for giving a phase difference of 180 degrees to the spot, light quantity setting means for making the light quantity of the main spot equal to the light quantity of the sub-spot, means for recording or reproducing data by the first light collection spot, second light collection An optical head device having focusing control means for detecting the intensity of reflected light from a spot with a split photodetector having a plurality of light receiving surfaces and performing focusing control by a predetermined calculation is provided. It is.

  The optical disc apparatus according to the present invention includes a first laser beam that is focused and irradiated on an optical recording medium to form a first focused spot, and a first focused spot in a direction in which the optical recording medium is scanned. Means for obtaining a second laser beam for forming a second focused spot side by side; means for dividing the second focused spot into a main spot and a sub spot in a scanning direction of the optical recording medium; Phase adding means for giving a phase difference of 180 degrees to the spot, light quantity setting means for making the light quantity of the main spot equal to the light quantity of the sub-spot, means for recording or reproducing data by the first focused spot, first focused light There is a tracking control means for detecting the intensity of the reflected light from the spot and the second focused spot with a split-type photodetector having a plurality of light receiving surfaces and performing tracking control by a predetermined calculation. Those having an optical head device.

  According to the optical head device and the optical disc device of the present invention, focusing control can be performed without being restricted by the track pitch and without being influenced by the diffracted light generated when traversing the guide groove of the optical disc. In addition, it is not subject to track pitch restrictions, is not affected by offset caused by diffracted light generated when traversing the guide groove of an optical disk or lens shift, etc., and is further affected by differences in the characteristics of components used and temperature characteristics. There is an effect that it is possible to perform highly accurate tracking control that is difficult to receive.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a main part, in particular, an optical system of an optical disk device and an optical head device 1 used therefor according to Embodiment 1 of the present invention.
The laser beam 3 emitted from the semiconductor laser 2 is converted into parallel light 5 by the collimator lens 4, and the first-order diffraction beam 7a that is the first laser beam and the + 1st-order diffraction that is the second laser beam by the diffraction grating 6. The laser beam is divided into three laser beams, a beam 7b and a −1st order diffraction beam 7c. The 0th-order diffracted beam 7a, the + 1st-order diffracted beam 7b, and the -1st-order diffracted beam 7c pass through the beam splitter 8 and are then focused and irradiated on the optical disk 10 by the objective lens 9 to be focused as a first focused spot. The spot 11a and the two focused spots 11b and 11c, which are the second focused spots, are formed in the scanning direction of the optical disc 10.

  Reflected light from the three condensing spots 11a, 11b, and 11c is reflected by the beam splitter 8 through the objective lens 9, and is divided into a four-divided light detector 14a that is a split type light detector by the condensing lens 12 and the cylindrical lens 13, respectively. , 14b, 14c. The current / voltage conversion circuit 15 converts the photocurrent signals from the quadrant detectors 14a, 14b, and 14c into voltage signals, and performs a predetermined operation in an FES generation circuit 16 for performing focusing control and a TES generation circuit 17 for performing tracking control. FES and TES are calculated by the above calculation, and the lens driving device 19 is operated based on them to change the objective lens 9 in the focal direction and the radial direction with respect to the optical disc 10. The RF signal generation circuit 18 detects the intensity of the reflected light of the first focused spot 11a by the four-divided light detector 14a, further generates an information signal of the optical disk 10 from the output of the current-voltage conversion circuit 15, and generates an audio or image signal. Etc. are reproduced. The focused spot 11a is also used for recording data on the optical disc 10, and in this case, in order to increase the output of the laser beam, the current / voltage conversion circuit 15 adjusts the gain to match the reproduction. Yes.

  FIG. 2 shows a situation in which the parallel light 5 is divided by the diffraction grating 6 into a 0th-order diffracted beam 7a that is the first laser beam, a + 1st-order diffracted beam 7b that is the second laser beam, and a −1st-order diffracted beam 7c. It is a perspective view shown. The diffraction grating 6 is formed by grooves formed linearly at equal intervals in a direction perpendicular to the direction in which the optical disk 10 is scanned. Further, it is divided into three areas of + N part, P part and -N part which are the first, second and third areas in the scanning direction of the optical disc 10, and the groove of the P part which is the second area in the center is formed. The period of the grooves of the + N part and the −N part which are the first and third regions on both sides with respect to the period is reversed by 180 degrees when one period is 360 degrees. The width of the P portion, + N portion, and −N portion in the scanning direction of the optical disk 10 is such that when the parallel light 5 passes through the diffraction grating 6, the amount of light transmitted through the P portion and the + N portion and −N portion are transmitted. Is set so that the sum of the amounts of light to be emitted is equal. The laser beam that has passed through the diffraction grating 6 is divided into three laser beams, a zero-order diffracted beam 7a, a + 1st-order diffracted beam 7b, and a −1st-order diffracted beam 7c, and is guided onto the optical disc 10.

  Next, the operation will be described. As described with reference to FIG. 2, the diffraction grating 6 is configured such that the period of the grating grooves is inverted by 180 degrees in the + N part and the −N part on both sides with respect to the central P part. For this reason, the + 1st order diffracted beam 7b and the −1st order diffracted beam 7c are diffracted and propagated at a diffraction angle depending on the interval between the grating grooves, and + N part with respect to the laser beam transmitted through the central P part inside the laser beam. The laser beam transmitted through the -N portion is subjected to 180 degree phase modulation. The zero-order diffracted beam 7a is not subjected to the diffraction action and phase modulation action of the diffraction grating 6 at all.

  These three diffracted beams 7a, 7b, and 7c are imaged as three focused spots on the optical disk 10 by the objective lens 9, and the reflected light is imaged on a four-divided photodetector as shown in FIG. Show. In FIG. 3, on the same information track 20 of the optical disc 10, the 0th-order focused spot 11a that is the first focused spot corresponding to the 0th-order diffracted beam 7a, the + 1st-order diffracted beam 7b, and the -1st-order diffracted beam 7c. The + 1st order focused spot 11b and the −1st order focused spot 11c, which are the second focused spots, are imaged. As described above, the + 1st-order condensing spot 11b is composed of a central main spot 21a and two sub-spots 21b and 21c whose phases are inverted by 180 degrees from the central main spot 21a by the diffraction action and phase modulation action of the diffraction grating 6. The The reflected lights of the 0th-order focused spot 11a, the + first-order focused spot 11b, and the −1st-order focused spot 11c are guided to the four-divided photodetectors 14a, 14b, and 14c, respectively.

  In FIG. 3, the main spot 21a and the sub-spots 21b and 21c of the condensing spot 11b have an elliptical shape. This is because the parallel light 5 is scanned by the P portion, + N portion, and −N portion of the diffraction grating 6. This is because the image is formed in a near-field region that is split into a laser beam that is long in the direction perpendicular to the direction and added with phase information and focused and irradiated on the optical disk 10. On the other hand, the image of the reflected light of the condensing spot 11b in the quadrant optical detector 14b is circular. The reflected light of the condensing spot 11b needs to be completely condensed on the quadrant optical detector 14b. Therefore, since the outer shape of the lens is a circle, the transmitted light also has a circular shape, which is a far field region where the shape is imaged. The same applies to the imaging of the −1st-order focused spot 11c and its reflected light onto the four-divided photodetector 14c.

  That is, the diffraction grating 6 according to the present invention obtains the converging spot 11a and the two converging spots 7b and 11c from the laser beam 3 emitted from the semiconductor laser 2 and the two diffracting beams 7b and 7c. Means, a means for dividing the condensed spots 11b and 11c into a main spot and two sub-spots, a phase adding means for giving a phase difference of 180 degrees to the two sub-spots relative to the main spot, a light quantity of the main spot and two sub-spots A light amount setting means for equalizing the sum of the light amounts of the spots is also provided.

  FIG. 4 is a perspective view showing the light intensity distribution of the + first-order focused spot 11b, where the X axis indicates the track direction, the Y axis indicates a direction perpendicular to the track direction, and the Z axis indicates the light intensity. Corresponding to the central P portion of the diffraction grating 6 and the + N portion and −N portion where the 180 ° phase is inverted on both sides, the condensing spot 11b has three peaks, a main spot 21a and sub-spots 21b and 21c on both sides. doing. Furthermore, since the sum of the light amount of the laser beam that passes through the P portion and the light amount of the laser beam that passes through the + N portion and the −N portion is set to be equal, the light amount of the main spot 21a and the sub-spots 21b and 21c The sum of the light amounts is formed to be equal. This is because the sub-spots 21b and 21c in FIG. 4 are lower than the main spot 21a. The same applies to the negative primary focused spot 11c. The zero-order focused spot 11a is not subjected to the diffraction action and phase modulation action of the diffraction grating 6 at all, and thus has a shape having only the main spot.

  A method of performing focusing control from the reflected light of each focused spot described above will be described. Focusing control in which a laser beam is focused on an optical disc is performed by detecting FES from reflected light from the optical disc of the laser beam. The FES detection method is performed by a well-known astigmatism method. This is because astigmatism is given by the reflected light of the laser beam passing through the cylindrical lens 13, and when the focused light is in focus, the irradiation shape of the reflected light to the photodetector becomes a circle, and when the focus is shifted, an elliptical shape is formed. The detailed description here is omitted.

  For generating the FES, the + 1st order focused spot 11b and the −1st order focused spot 11c formed on the optical disk 10 are used. Reflected light of each condensing spot is received by the light detector 14 at the + 1st-order focused spot 11b by the 4-split light detector 14b and the -1st-order focused spot 11c by the 4-split photodetector 14c. As shown in FIG. 3, the four-split light detectors 14b and 14c are divided into four in the track scanning direction and the direction perpendicular to the scanning direction, and electric signals corresponding to the intensity of each light are E1, F1, When G1, H1, and E2, F2, G2, and H2,

    FES = (E1 + E2 + G1 + G2) − (F1 + F2 + H1 + H2) (1)

FES is calculated by the following calculation. When in focus, the shape of the reflected light of the condensed spots 11b and 11c irradiated to the four-split light detectors 14b and 14c is a circle, so the FES in Equation (1) is zero, but the focus is If it is deviated, this shape becomes an elliptical shape in the diagonal direction of the 4-split photodetector, so that FES in Equation (1) is a non-zero value.

Therefore, it is better to control the lens driving device 19 so that the calculation result of the formula (1) becomes zero. However, the FES as shown in FIG. Since focusing control cannot be performed, in the conventional astigmatism method, the focused spots are formed at intervals of an integral multiple of 1/2 of the track pitch so as to eliminate the influence of the guide grooves. As described above, in this method, it is difficult to cope with optical disks having different track pitches.

  Therefore, in the present invention, as indicated by the + first-order condensing spot 11b in FIG. 3, the FES is calculated using the reflected light of the main spot 21a and the sub-spots 21b and 21c whose phases are inverted by 180 degrees. In this case, for example, the influence of the diffracted light received from the guide groove when the + first-order focused spot 11b crosses the guide groove of the optical disc 10 is completely opposite between the main spot 21a and the sub-spots 21b and 21c. Further, since the sum of the light amount of the main spot 21a and the light amounts of the sub-spots 21b and 21c is equal, the influence of the diffracted light of the guide grooves received by the main spot 21a and the sub-spots 21b and 21c is opposite in action and equal in magnitude. As a result, they are canceled out and become equivalent to being not affected by the diffracted light from the guide groove. This can be said to be equivalent to the fact that the + 1st-order focused spot 11b and the -1st-order focused spot 11c are imaged on a flat optical disc having no guide groove in spite of the presence of the guide groove. it can. As a result, from Formula (1), an FES free from disturbance can be obtained as shown in FIG.

  For focusing control, the signal of the focused spot 11a is not used. However, the focused spot 11a is used for recording or reproducing digital data as described above, and is therefore indispensable as an optical head device. is there.

  Next, the tracking control operation will be described. The tracking control is for correctly following and scanning the laser beam on the track of the optical disk, and is performed by detecting TES from the reflected light of the laser beam from the optical disk in the same manner as the focusing control described above. The TES detection method is performed by a well-known differential push-pull method. This is because when the laser beam scans off the track, tracking control is performed by the difference in light intensity in the direction perpendicular to the scanning direction of the reflected light, and the influence of the offset component due to the objective lens shift and the tilt of the optical disk. There is a feature that does not receive.

  A TES generation method by the differential push-pull method in the present invention is as follows. For the generation of TES, the 0th-order focused spot 11a, the + first-order focused spot 11b, and the −1st-order focused spot 11c formed on the optical disk 10 are used. The reflected light of the respective condensed spots is detected by the photodetector 14 in which the zero-order condensed spot 11a is a four-divided photodetector 14a, the first-order condensed spot 11b is a four-divided photodetector 14b, and the −1st-order condensed spot 11c. Is received by the four-split light detector 14c. As shown in FIG. 3, the four-split light detectors 14a, 14b, and 14c are divided into four parts, that is, the scanning direction of the track and the direction perpendicular to the scanning direction, and the electric signals corresponding to the intensity of each light (A, B , C, D), (E1, F1, G1, H1) and (E2, F2, G2, H2),

TES = {(A + D)-(B + C)}
-K {(E1 + E2 + H1 + H2)-(F1 + F2 + G1 + G2)} (2)

TES is calculated by the following calculation. When the focused spot 11a correctly scans the track, the reflected light is received at the center of the four-divided photodetector 14a, so that the left and right light intensities are equal to the scanning direction of the track. The value of the first term {(A + D)-(B + C)} (referred to as a push-pull signal) is zero. On the other hand, when the focused spot 11a scans off the track, it becomes a non-zero value due to the influence of the diffracted light in the guide groove. This is repeated each time the focused spot crosses the guide groove, and the change of {(A + D)-(B + C)} at this time is shown in FIG.

  The waveform in FIG. 7 is a waveform in which an offset component is superimposed. This waveform is generated depending on the lens shift of the objective lens or the tilt of the optical disc, and TES disturbance causes correct tracking control. It is a cause that disappears. The second term of Equation (2) is a push-pull signal calculated from the reflected light from the + 1st order focused spot 11b and the −1st order focused spot 11c, and as described above, the + 1st order focused spot 11b and − Since the influence of the diffracted light from the guide groove is canceled in the primary focused spot 11c, the push-pull signal calculated from the four-split optical detectors 14b and 14c is guided from the waveform of FIG. 7 as shown in FIG. Only the effect of removing the diffracted light of the groove, ie, the offset component is obtained. Further, by setting the coefficient k so as to cancel out the offset component in the formula (2), a TES without disturbance from which the offset component is removed can be obtained from the formula (2) as shown in FIG.

  In terms of tracking control, three focused spots 11a, 11b, and 11c are used, but the focused spot 11a is also used for recording or reproducing digital data as described above.

According to the first embodiment, it is possible to obtain an FES without a disturbance signal due to the influence of the diffracted light from the guide groove without being restricted by the track pitch, and from the guide groove without being restricted by the track pitch. There is no disturbance signal due to the effect of offset components due to diffracted light and lens shift or optical disc tilt, and the calculation process only subtracts the offset component, which is a DC component. Can be obtained.
Further, a region in which the groove period of the diffraction grating 6 is inverted by 180 degrees in order to give phase modulation to the laser beam is formed in the direction in which the optical disk 10 is scanned, that is, in the direction perpendicular to the groove direction of the diffraction grating 6 (FIG. 2). Therefore, there is an effect that it is easy to manufacture the diffraction grating 6, especially the boundary portion of the region where the phase is changed.

  In the FES calculation of the first embodiment, the reflected light from the two focused spots 11b and 11c corresponding to the two laser beams is received by the two four-divided photodetectors 14b and 14c. Although the FES is calculated by calculation, the FES may be calculated by a predetermined calculation after receiving light by one four-divided light detector 14b or 14c using one condensing spot 11b or 11c. In that case, although the S / N ratio is slightly reduced, it is possible to reduce the parts to be used, and as a result, it is possible to reduce costs and improve reliability.

  In the TES calculation of the first embodiment, the reflected light from the three focused spots 11a, 11b, and 11c corresponding to the three laser beams is received by the three quadrant photodetectors 14a, 14b, and 14c. The TES was calculated by a predetermined calculation, and received by the two four-split photodetectors 14a, 14b or 14a, 14c using the two focused spots 11a, 11b or 11a, 11c, and the predetermined calculation. TES may be calculated. In that case, the intended purpose can be achieved by adjusting the value of the coefficient k. Although the S / N ratio is slightly reduced, it is possible to reduce the parts to be used, and as a result, it is possible to reduce costs and improve reliability.

  Furthermore, the diffraction grating 6 may be installed on the semiconductor laser 2 side by reversing the installation positions of the collimator lens 4 and the diffraction grating 6 of the first embodiment. Then, since the intensity distribution of the laser beam emitted from the semiconductor laser 2 is a so-called Gaussian distribution, the light amount of the laser beam that passes through the P portion of the diffraction grating 6 and the laser beam that passes through the + N portion and the −N portion. Fine adjustment for setting the sum of the light amounts to be equal can be performed by moving the diffraction grating 6 in the laser beam irradiation direction.

1 is a configuration diagram of an example of an optical disc device according to Embodiment 1 of the present invention and an optical system of an optical head device. It is a perspective view which shows the diffraction grating 6 of Embodiment 1 of this invention. It is a figure which shows the condensing spot on the optical disk 10 of Embodiment 1 of this invention, a 4-part dividing light detector, and a calculation processing block. It is a perspective view which shows the light intensity distribution of the condensing spot 11b of Embodiment 1 of this invention. It is a wave form diagram which shows FES by the conventional astigmatism method. It is a wave form diagram which shows FES by Embodiment 1 of this invention. It is a wave form diagram of the push pull signal detected from the 0th-order condensing spot 11a of Embodiment 1 of this invention. It is a wave form diagram of the push pull signal detected from the + 1st order condensing spot 11b of Embodiment 1 of this invention, and the -1st order condensing spot 11c. It is a wave form diagram which shows TES of Embodiment 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical head apparatus, 2 Semiconductor laser, 3 Laser beam, 4 Collimator lens, 5 Parallel light, 6 Diffraction grating, 7a 0th order diffracted beam, 7b + 1st order diffracted beam, 7c-1st order diffracted beam, 8 Beam splitter, 9 Objective Lens, 10 Optical disc, 11a 0th-order focused spot, 11b + 1st-order focused spot, 11c-1st-order focused spot, 12 Condensing lens, 13 Cylindrical lens, 14 Photo detector, 14a 4 split photo detector, 14b 4 Split light detector, 14c Quadrant light detector, 15 Current-voltage conversion circuit, 16 FES generation circuit, 17 TES generation circuit, 18 RF signal generation circuit, 19 Lens drive device, 20 track, 21a Main spot, 21b Sub spot, 21c Vice spot.

Claims (14)

  A first laser beam that is focused and irradiated on the optical recording medium to form a first focused spot, and a second focused spot that is aligned with the first focused spot in the scanning direction of the optical recording medium Means for obtaining a second laser beam for forming a second spot; means for dividing the second focused spot into a main spot and a sub spot in a direction of scanning the optical recording medium; Phase adding means for providing a phase difference of the above, light quantity setting means for making the light quantity of the main spot equal to the light quantity of the sub-spot, means for recording or reproducing data by the first light collection spot, the second light collection Focusing control means for detecting the intensity of reflected light from the spot with a split-type photodetector having a plurality of light receiving surfaces and performing focusing control by a predetermined calculation is provided. De devices.   2. The optical head device according to claim 1, wherein the focusing control means is performed by an astigmatism method.   A first laser beam that is focused and irradiated on the optical recording medium to form a first focused spot, and a second focused spot that is aligned with the first focused spot in the scanning direction of the optical recording medium Means for obtaining a second laser beam for forming a second spot; means for dividing the second focused spot into a main spot and a sub spot in a direction of scanning the optical recording medium; Phase adding means for providing a phase difference of the above, light quantity setting means for making the light quantity of the main spot equal to the light quantity of the sub-spot, means for recording or reproducing data by the first light collection spot, the first light collection Tracking control means for detecting the intensity of reflected light from the spot and the second focused spot with a split type photodetector having a plurality of light receiving surfaces and performing tracking control by a predetermined calculation is provided. An optical head and wherein the a.   4. The optical head device according to claim 3, wherein the tracking control means is performed by a differential push-pull method.   The second focused spot is two focused spots, the second laser beam is two laser beams, and the secondary spot is two secondary spots. The optical head device described.   The means for obtaining the first laser beam and the second laser beam, the means for splitting the second focused spot, the phase adding means, and the light quantity setting means have grooves in a direction perpendicular to the scanning direction of the optical recording medium. The first and second regions are formed in order in the scanning direction of the optical recording medium, and the period of the lattice grooves in the second region and the lattice grooves in the first and third regions are formed. And a diffraction grating configured such that the light amount of the laser beam transmitted through the second region is equal to the sum of the light amounts of the laser beams transmitted through the first and third regions. 6. The optical head device according to claim 1, wherein the optical head device is provided.   7. The optical head device according to claim 1, wherein the first focused spot and the second focused spot are formed on the same information track of the optical recording medium.   A first laser beam that is focused and irradiated on the optical recording medium to form a first focused spot, and a second focused spot that is aligned with the first focused spot in the scanning direction of the optical recording medium Means for obtaining a second laser beam for forming a second spot; means for dividing the second focused spot into a main spot and a sub spot in a direction of scanning the optical recording medium; Phase adding means for providing a phase difference of the above, light quantity setting means for making the light quantity of the main spot equal to the light quantity of the sub-spot, means for recording or reproducing data by the first light collection spot, the second light collection Information is detected by an optical head device equipped with a focusing control means for detecting the intensity of reflected light from the spot with a split photodetector having a plurality of light receiving surfaces and performing focusing control by a predetermined calculation. Optical disc apparatus characterized by performing the recording or reproduction.   9. The optical disc apparatus according to claim 8, wherein the focusing control means is performed by an astigmatism method.   A first laser beam that is focused and irradiated on the optical recording medium to form a first focused spot, and a second focused spot that is aligned with the first focused spot in the scanning direction of the optical recording medium Means for obtaining a second laser beam for forming a second spot; means for dividing the second focused spot into a main spot and a sub spot in a direction of scanning the optical recording medium; Phase adding means for providing a phase difference of the above, light quantity setting means for making the light quantity of the main spot equal to the light quantity of the sub-spot, means for recording or reproducing data by the first light collection spot, the first light collection Tracking control means for detecting the intensity of reflected light from the spot and the second focused spot with a split type photodetector having a plurality of light receiving surfaces and performing tracking control by a predetermined calculation is provided. Optical disc and wherein the recording or reproduction of information by the optical head apparatus.   11. The optical disk apparatus according to claim 10, wherein the tracking control means is performed by a differential push-pull method.   The second focused spot is two focused spots, the second laser beam is two laser beams, and the secondary spot is two secondary spots. The optical disk device described.   The means for obtaining the first laser beam and the second laser beam, the means for splitting the second focused spot, the phase adding means, and the light quantity setting means have grooves in a direction perpendicular to the scanning direction of the optical recording medium. The first and second regions are formed in order in the scanning direction of the optical recording medium, and the period of the lattice grooves in the second region and the lattice grooves in the first and third regions are formed. And a diffraction grating configured such that the light amount of the laser beam transmitted through the second region is equal to the sum of the light amounts of the laser beams transmitted through the first and third regions. The optical disk apparatus according to claim 8, wherein the optical disk apparatus is provided. 14. The optical disc apparatus according to claim 8, wherein the first focused spot and the second focused spot are formed on the same information track of the optical recording medium.

Images