JPH1186332A - Optical head device - Google Patents

Abstract

(57) Abstract: Provided is an optical head device capable of reliably removing an offset component included in a track error signal. An optical head device according to the present invention is a photodetector for detecting a track shift signal. By providing a light receiving area for detecting an offset component for removing an output of an offset component included in the track shift signal in a part of the light receiving area, 0th-order diffracted light, 1 The offset component included in the track shift signal, that is, the influence of the lens shift on the track error signal is removed by using the light in the portion where all of the first-order diffracted light and the minus first-order diffracted light overlap. Therefore, stable tracking control is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an optical head device for recording information on an optical disk as a recording medium and reproducing information from the optical disk.

[0002]

2. Description of the Related Art An optical disk device includes an optical head device having an objective lens for irradiating a recording surface of an optical disk as a recording medium with a light beam having a cross-sectional beam diameter set to a predetermined size. By irradiating the beam, reflected light corresponding to the information recorded on the optical disk is taken out to reproduce the information.

The above-described optical head device has a semiconductor laser device (hereinafter simply referred to as a laser device) as a light source for generating a light beam and a light beam radiated from the laser device on a recording surface of an optical disk as a recording medium. An objective lens for converging and extracting a reflected light beam reflected by the recording surface, a photodetector for photoelectrically converting the reflected light beam extracted by the objective lens and outputting a reproduction signal corresponding to information recorded on the optical disc; Each element is formed by a plurality of optical members or the like constituting an optical path of a light beam. The optical head device has an objective lens mounted on an actuator (movable part) in order to enable high-speed access, and a laser element, a photodetector, and an optical member forming an optical path are fixed units separated from the actuator. (Fixed part) is widely used.

On the recording surface of the optical disk, a guide groove called a groove is provided so that the condensed spot of the light beam condensed by the objective lens can always follow a predetermined radial position. I have.

In order to always match the center of the condensed spot converged by the objective lens with the center of the groove,
The objective lens is moved in the radial direction of the optical disk by the well-known tracking control.

In this case, the amount by which the objective lens should be moved, that is, the tracking control amount, is determined based on a track error signal obtained using, for example, a known push-pull method.
Is set. In the push-pull method, a light beam reflected / diffracted by a groove is received by a photodetector having a light sensing unit divided into two parts, and photoelectrically converted. A difference between the photoelectrically converted signals is determined by a track error. This method is used as a signal. For example, "optical disk technology" (Noboru Murayama et al., 198
9-year Radio Technology Co., Ltd., pages 86 to 87 and FIG.
99 described elsewhere.

[0007]

However, when a track error signal is obtained by using the above-described push-pull method, as described in "Optical Disc Technology", an offset component of the track error signal results. However, there is a problem that a tracking error signal is output as if the tracking error occurred even though no tracking error occurred.

[0008] This offset is used, for example, when it is necessary to read information at another radial position on the optical disk or to newly record information at another radial position.
Moving the objective lens, ie, the actuator, from the radial position currently hit by the converging spot to the target radial position at a high speed causes the center of the objective lens to shift. The shift of the center of the objective lens is called a lens shift.

Since the above-described lens shift is caused by moving the actuator at a high speed in the radial direction of the optical disk, the lens shift is substantially eliminated from the viewpoint of increasing the speed of reading or writing information. It is difficult to do. For this reason, there is a problem that the offset component contained in the track shift signal must be reliably removed.

An object of the present invention is to provide an optical head device capable of reliably removing an offset component contained in a track shift signal and obtaining a stable tracking characteristic.

[0011]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned problems, and comprises a semiconductor laser for supplying a light beam to a recording medium, and a light beam emitted from the semiconductor laser. An objective lens for condensing on a medium, and a photoelectric conversion unit for converting a reflected light beam reflected / diffracted from the recording medium into an electric signal,
In the optical head having at least the photoelectric conversion unit, when the condensed spot obtained by being converged by the objective lens moves in the radial direction of the recording medium, the reflected light beam reflected by the recording medium on the condensed spot Has a photoelectric conversion region divided into at least two light receiving regions by a dividing line defined in a direction substantially perpendicular to a direction in which the light receiving region is moved by being projected onto the photoelectric conversion means. A photoelectric conversion signal obtained by photoelectrically converting the reflected light beam by the predetermined light receiving region, and the reflected light beam is photoelectrically converted by the light receiving region forming a pair with the predetermined light receiving region among the light receiving regions divided by the division line. A first difference signal that is a difference from the converted photoelectric conversion signal is obtained. From the first difference signal, the condensed spot is diffracted by the recording medium. The 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light of the light beam overlap each other, and the reflected light beam is photoelectrically converted by a predetermined light receiving region among the light receiving regions divided by the division line. A second difference signal that is a difference between a photoelectric conversion signal and a photoelectric conversion signal obtained by photoelectrically converting the reflected light beam by a light receiving region forming a pair with the predetermined light receiving region among the light receiving regions divided by the division line. An optical head device characterized in that an output signal obtained by removing the above is used as a tracking error signal.

Also, the present invention provides a semiconductor laser for supplying a light beam to a recording medium, an objective lens for condensing a light beam emitted from the semiconductor laser on the recording medium, and An optical head having at least photoelectric conversion means for converting the reflected / diffracted reflected light beam into an electric signal, wherein the photoelectric conversion means is configured such that a condensed spot obtained by being converged by the objective lens is provided on the recording medium. When moved in the radial direction of
A photoelectric conversion area divided into at least two light-receiving areas by a dividing line defined in a direction substantially perpendicular to a direction in which the reflected light beam reflected by the recording medium from the condensed spot is projected onto the photoelectric conversion means and moves. And a photoelectric conversion signal obtained by photoelectrically converting the reflected light beam by a predetermined light receiving area among the light receiving areas divided by the division line, and the predetermined light reception among the light receiving areas divided by the division line A first difference signal, which is a difference between the reflected light beam and a photoelectrically converted signal obtained by photoelectrically converting the reflected light beam by a light receiving region forming a pair with an area, is obtained. The 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light of the diffracted light beam overlap each other, and a predetermined light reception in the light receiving area divided by the division line. A photoelectric conversion signal obtained by photoelectrically converting the reflected light beam according to a region, and a photoelectric conversion in which the reflected light beam is photoelectrically converted by a light receiving region forming a pair with the predetermined light receiving region among the light receiving regions divided by the division line. It is an object of the present invention to provide an optical head device wherein an output signal obtained by removing a second difference signal obtained by amplifying or reducing a difference from a signal by a predetermined value is used as a tracking error signal.

Further, the present invention provides a semiconductor laser for supplying a light beam to a recording medium, an objective lens for condensing a light beam emitted from the semiconductor laser on the recording medium, and An optical head having at least photoelectric conversion means for converting the reflected / diffracted reflected light beam into an electric signal, wherein the photoelectric conversion means is configured such that a condensed spot obtained by being converged by the objective lens is provided on the recording medium. When moved in the radial direction of
A photoelectric conversion area divided into at least two light-receiving areas by a dividing line defined in a direction substantially perpendicular to a direction in which the reflected light beam reflected by the recording medium from the condensed spot is projected onto the photoelectric conversion means and moves. And each of the at least two light receiving regions has at least two arc-shaped light receiving regions divided by an arc-shaped outer dividing line defined symmetrically with the dividing line as a symmetry axis, and A photoelectric conversion signal obtained by photoelectrically converting the reflected light beam by a predetermined light receiving region among the divided light receiving regions, and a light receiving region forming a pair with the predetermined light receiving region among the light receiving regions divided by the dividing line. A first difference signal, which is a difference between the reflected light beam and a photoelectrically converted signal obtained by photoelectrically converting the light beam, is obtained. From the first difference signal, the condensed spot is rotated by the recording medium. Has been zero-order diffracted light and 1 said each first-order diffracted light and -1-order diffracted light of the light beam
And one of the photoelectric conversion signals obtained by photoelectrically converting the reflected light beam by the second circular light receiving region is amplified or reduced by a predetermined value, and the reflected light beam is amplified by the first and second circular light receiving regions. Is the second difference signal that is the difference between the photoelectrically converted photoelectrically converted signal and the other one of the signals.
It is an object of the present invention to provide an optical head device characterized in that an output signal obtained by removal is used as a tracking error signal.

Still further, the present invention provides a semiconductor laser for supplying a light beam to a recording medium, an objective lens for condensing a light beam emitted from the semiconductor laser on the recording medium, and a recording medium. And a photoelectric conversion unit for converting a reflected light beam reflected and diffracted from the object into an electric signal, wherein the photoelectric conversion unit is configured to record a condensed spot obtained by being converged by the objective lens. When the recording medium moves in the radial direction, at least two division lines are defined by a dividing line defined in a direction substantially perpendicular to the direction in which the reflected light beam reflected by the recording spot on the recording medium is projected onto the photoelectric conversion unit and moved.
A photoelectric conversion region divided into two light receiving regions, and at least two arc-shaped light receiving regions divided by each of the at least two light receiving regions by an arc-shaped outer dividing line symmetrically defined with the dividing line as a symmetric axis. And a photoelectric conversion signal obtained by subjecting the reflected light beam to photoelectric conversion by a predetermined light receiving region among the light receiving regions divided by the division line, and the predetermined light receiving region divided by the division line. A first difference signal which is a difference between the reflected light beam and the photoelectrically converted signal obtained by photoelectrically converting the reflected light beam is obtained by a light receiving region forming a pair with the light receiving region. The 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light of the light beam diffracted by the medium are each subjected to photoelectric conversion of the reflected light beam by the first and second arc-shaped light receiving regions. One of the photoelectric conversion signals is amplified or reduced by a predetermined value, and the difference between the one of the photoelectric conversion signals obtained by photoelectrically converting the reflected light beam by the first and second arc-shaped light receiving regions is compared with the other of the other signals. It is an object of the present invention to provide an optical head device characterized in that an output signal obtained by removing the second difference signal obtained by further amplifying or reducing the obtained value by a predetermined value is used as a tracking error signal.

Still further, the present invention provides a light source for emitting a light beam, a polarizing beam splitter for guiding the light beam emitted from the light source toward a recording medium, and a light passing through the polarizing beam splitter. An objective lens for giving a predetermined imaging characteristic to the beam to converge on the recording surface of the recording medium, and a track control coil for generating a propulsive force for moving the objective lens in a direction orthogonal to a guide groove specific to the recording medium The light beam converged on the recording surface of the recording medium by the objective lens, reflected by the recording surface, and passed through the objective lens again is reflected by the polarizing beam splitter to travel toward the objective lens. A non-polarizing beam splitter functioning as a half mirror for splitting the separated light beam into two light beams having substantially equal light intensities, and a recording medium The first and second two light receiving areas divided by a dividing line extending along the direction in which the shadow of the guide groove unique to the light receiving area is projected, and the first light receiving area and the second light receiving area are divided into the first light receiving area and the second light receiving area. First and second 2 divided by an arc-shaped outer dividing line defined symmetrically with the line as a symmetry axis
Two light receiving areas, and the first and second light receiving areas receive the light beam split by the non-polarizing beam splitter, and photoelectrically convert the light beam into the light beam. A track shift signal indicating a degree of shift from the center of the light beam converged by the objective lens is generated, and the light beam reflected on the recording surface of the recording medium by the first and second arc-shaped light receiving areas. A light beam applied to an area where each of the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light overlaps is received, photoelectrically converted, and converged by the center of the guide groove unique to the recording medium and the objective lens. A photodetector for generating a signal corresponding to an offset component in a track shift signal indicating a degree of shift from the center of the light beam, and the first and second light receiving areas of the photodetector; From the difference signal between two signals obtained by adding the outputs output from the first and second arc-shaped light receiving regions to the output output from each of the first and second arc-shaped light receiving regions based on a predetermined combination. And the difference signal between the output signals output from each of the second arc-shaped light receiving regions is subtracted, and the actual difference between the center of the guide groove unique to the recording medium and the center of the light beam converged by the objective lens is reduced. Based on a track error and offset detection circuit for determining the degree of the error, and a track error signal obtained by the track error and offset detection circuit.
A tracking control circuit for supplying a current in a predetermined direction to the track control coil.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram schematically illustrating an optical disc device in which an optical head device according to an embodiment of the present invention is incorporated.

As shown in FIG. 1, the optical disk device 1
Is an optical head device 3 for recording information on a recording surface of an optical disk D as a recording medium or reading information already recorded on the recording surface, and a signal corresponding to information to be recorded on the optical head device 3. And a control unit 9 that controls a motor 7 that rotates the optical head device 3 and the optical disc D at a predetermined speed. Have. An external device 99 such as a host computer is connected to the signal processing unit 5 via an interface (not shown).

In FIG. 1, the optical head device 3 transmits and receives electric signals to and from the signal processing unit 5 while controlling the irradiation position of the light beam irradiating the optical disk D by the control signal from the control unit 9. A light beam is exchanged with the optical disc D.

The signal processing unit 5 converts information read from the optical disk D by the optical head device 3 into an electric signal based on an instruction from the external device 99, and reproduces the information as recorded information. A recording signal is generated to make the information to be recorded correspond to the change in the light intensity of the light beam emitted from the optical head device 3.

The control unit 9 controls the light intensity of the light beam emitted from the optical head device 3 to the optical disk D, the position of the light beam on the optical disk, the rotation speed of the optical disk D rotated by the motor 7, and the like.

Hereinafter, the operation of the optical disk apparatus 1 shown in FIG. 1 will be briefly described. First, the signal processing unit 5 is connected to the external device 9.
9 for reproducing or recording information on the optical disk D.

Based on this command signal, the signal processing unit 5
Exchanges electrical signals with the optical head device 3 and transmits control signals to the control unit 9. Based on the transmitted control signal, the control unit 9 controls the irradiation position of the light beam on the optical disc D irradiated by the optical head device 3 and the rotation speed of the motor 7.

As described above, while being controlled by the control section 9, the optical head device 3 transmits and receives a light beam to and from the optical disk D based on the electric signal exchanged with the signal processing section 5. To reproduce or record information.

When the information is reproduced or recorded, the optical head device 3 obtains an electric signal corresponding to the information recorded on the optical disc D and the information on the light beam irradiation position, and converts the electric signal into a signal processing unit. 5 is transmitted.

The signal processing unit 5 sends a control signal for changing the position of the optical head device 3 to the control unit 9 based on the electric signal corresponding to the information on the irradiation position of the light beam from the electric signal. After performing processing such as decoding on the electric signal corresponding to the recorded information, the processed electric signal (reproduced signal) is transmitted to the external device 99.

The external device 99 that has received the reproduction signal from the signal processing unit 5 refers to this reproduction signal and
Then, the instruction signal as the next instruction is transmitted to the signal processing unit 5 again.

The optical disk apparatus 1 reproduces information recorded on the optical disk D or records information on the optical disk D by repeating a series of operations as described above. Next, the structure of the optical head device 3 will be described with reference to FIGS.

As shown in FIG. 2, the optical head device 3
Are a laser light emitting / receiving unit (hereinafter, referred to as a fixed optical system) 3a fixed on the base 31 and a fixed optical system 3a
And an actuator 3b for irradiating the recording surface of the optical disk D with the laser beam from the optical disk D and guiding the reflected laser beam reflected on the recording surface of the optical disk D again to the fixed optical system 3a. The actuator 3b includes, as shown in FIG. 3, a carriage 33 movably formed on a pair of guide rails 32, 32 extending in the radial direction of the optical disc D, and is integrally formed with the carriage 33. The guide rails 32, 34 are formed by a pair of radial drive coils 34, 34 and a magnetic field supplied from a magnetic field supply mechanism (not shown).
32 is formed so as to be movable in the radial direction of the optical disc D.

The fixed optical system 3a has a housing 10 made of, for example, aluminum, as shown in FIG. A laser element (semiconductor laser) 11 for generating a laser beam of a predetermined wavelength is provided at one end of the housing 10.
Has been fixed.

In the direction in which the laser beam Rf emitted from the semiconductor laser 11 travels, the divergent laser beam R
A collimator lens 12 for collimating f is arranged.

In the direction in which the laser beam Rf collimated by the collimator lens 12 is guided, the cross-sectional beam shape of the laser beam Rf emitted as an ellipse is changed from an ellipse to a circle in relation to the aspect ratio specific to the laser beam Rf. An elliptical correction prism 13 to be corrected and a laser beam Rf formed integrally with the elliptical correction prism 13 and having a substantially circular cross-sectional shape are passed toward the actuator 3b, that is, the optical disk D, and are reflected by a recording surface (not shown) of the optical disk D. A beam splitter 14 for separating the reflected laser beam Rr from the laser beam Rf heading for the optical disk D and a laser beam Rf passed through the beam splitter 14 and directed to the actuator 3b to change the direction of the polarization plane from linearly polarized light to circularly polarized light. And reflected on the optical disc D Direction of polarization direction of the polarization plane of the reflected laser beam Rr which the circular polarization to the direction of the plane of polarization of the laser beam Rf directed to actuator 3b is 90
A λ / 4 plate (phase delay plate) 15 for converting into linearly polarized light rotated by ° is arranged in order. Note that the beam splitter 14 is a polarization beam splitter.

The optical disk D by the beam splitter 14
The reflected laser beam Rr separated from the laser beam Rf toward
Is divided into two laser beams Rra and Rrb, and a half mirror type beam splitter 16 is arranged.

In the direction in which the laser beam Rra split into two by the beam splitter 16 is guided, a converging lens 17 for giving a predetermined imaging characteristic and convergence to the reflected laser beam Rra reflected by the optical disk D is arranged. ing.

In the direction in which the reflected laser beam Rra given convergence by the converging lens 17 travels, the reflected laser beam Rra passes through the concave lens 18, which improves the aberration due to the convergence given to the reflected laser beam Rra by the converging lens 17. A cylindrical lens 19 that gives predetermined imaging characteristics for detecting a focus shift described later to the reflected laser beam Rra, and a reflected laser beam Rr that is given predetermined imaging characteristics by the cylindrical lens 19.
The photodetectors 20 that receive the signal a and output an output signal corresponding to the light intensity of the received reflected laser beam Rra are arranged in order.

In the direction in which the laser beam Rrb split into two by the beam splitter 16 is guided, a mirror 21 for guiding the reflected laser beam Rrb reflected on the optical disk D in a predetermined direction is arranged.

In the direction in which the reflected laser beam Rrb bent by the mirror 21 travels, a converging lens 22 for giving a predetermined convergence to the reflected laser beam Rrb is arranged.

In the direction in which the reflected laser beam Rrb given a predetermined convergence by the converging lens 22 is guided, a photodetector 23 used for detecting a track shift and an offset amount described later is arranged. I have.

The carriage 33 of the actuator 3b has
As shown in FIG. 5, the laser beam Rf emitted from the fixed optical system 3a after passing through the beam splitter 14 and the λ / 4 plate 15 of the fixed optical system 3a is bent so as to be incident on an objective lens described below. A rising mirror 35 is provided.

The predetermined direction of the recording surface of the optical disk D is set between the direction in which the laser beam Rf guided by the rising mirror 35 and bent by approximately 90 ° by the rising mirror 35 is directed, that is, between the rising mirror 35 and the optical disk D. An objective lens 36, which is bent by the rising mirror 35 to converge the laser beam Rf and takes out the reflected laser beam Rr reflected by the recording layer of the optical disc D, is disposed on the recording layer (not shown). The objective lens 36
Is a direction parallel to the recording surface of the optical disk D by the lens holder described below with reference to FIG.
The optical disc D is movably held in a tracking direction substantially perpendicular to a guide groove or groove g formed in advance and a focus direction perpendicular to the recording surface of the optical disc D.

As shown in FIG. 5, the lens holder 37
Has a bearing portion 37a substantially at the center, and a lens holding surface 37b holding the objective lens 36 on a circumference of a concentric circle having a predetermined radius centered on the bearing portion 37a, and a direction perpendicular to the lens holding surface 37b. A bearing portion 37a is provided on a shaft 39 having a cylindrical surface 37c formed in a partially cut-out cylindrical shape, and extending substantially from the center of a lens holder base 38 fixed at a predetermined position of the carriage 33. By being engaged, it is formed to be rotatable around the shaft 39.

Two sets of coils 4 are provided on the cylindrical surface 37c of the lens holder 37 at positions defined so as to divide the outer periphery of the cylindrical surface 37c into approximately four equal parts along an axis passing through the bearing 37a.
0, 40 and 41, 41 are provided.

The lens holder base 38 has an arbitrary radius whose radius is increased compared to the cylindrical surface 37c of the lens holder 37 with the axis 39 as the center axis. A yoke 42 having a notched portion is formed. At a predetermined position on the inner wall of the yoke 42, two sets of magnets 43, 43 and 44, which provide a magnetic field in a predetermined direction toward the cylindrical surface 37c of the lens holder 37,
44 are provided. The magnets 43, 43 are magnetized to have N and S poles in a form that is divided into two by a plane orthogonal to the optical axis of the objective lens 36. The N and S poles are magnetized in such a manner that the N and S poles are divided into two parts by a plane parallel to.

Next, the flow of the laser beam in the optical head device 3 described with reference to FIGS. 2 to 5 will be described. Laser beam R emitted from semiconductor laser 11
f is converted into a parallel light beam by the collimator lens 12, the cross-sectional shape is corrected to a substantially circular shape by the elliptical correction prism 13, and the light passes through the beam splitter 14.

The laser beam Rf transmitted through the beam splitter 14 passes through the quarter-wave plate 15 so that the polarization direction is changed from linearly polarized light to circularly polarized light, and is emitted toward the rising mirror 35 of the actuator 3b. Is done.

The laser beam Rf guided to the rising mirror 35 is bent by about 90 ° by the rising mirror 35 and guided to the objective lens 36 held in the lens holder 37.

The laser beam Rf is guided to the objective lens 36 and converged, and thereafter, is irradiated on the optical disk D as a spot. The reflected laser beam Rr reflected by the optical disc D is returned to the objective lens 36 and the rising mirror 35 in order, and the quarter-wave plate 15 changes the polarization state from circularly polarized light to linearly polarized light again. You will be guided. Since the polarization direction of the reflected laser beam Rr is rotated by exactly 90 ° with respect to the polarization direction of the original laser beam Rf emitted from the semiconductor laser 11, the reflected laser beam Rr is
Is then reflected by the polarization plane.

The reflected laser beam Rr separated from the laser beam Rf from the semiconductor laser 11 toward the objective lens 36 by the beam splitter 14 is converted into two laser beams Rra and Rrb having substantially equal light intensities by the beam splitter 16. Divided.

The reflected laser beam Rra transmitted through the beam splitter 16 is given predetermined imaging characteristics and convergence by a converging lens 17, then the aberration characteristics are improved by a concave lens 18, and the cylindrical lens 19 detects a focus shift. The photodetector 20 is irradiated with the astigmatism for

The laser beam ra applied to the photodetector 20 is converted by the photodetector 20 into an electric signal having a magnitude corresponding to the light intensity, and is used as a focus error signal and a reproduction signal. In this example, the detection of the focus error signal is a well-known astigmatism method, and a detailed description thereof will be omitted.

On the basis of the focus error signal generated by the photodetector 20, focus control, that is, focusing is performed to eliminate the deviation of the focal point of the spot converged by the objective lens 36 from the recording surface of the optical disk D in the optical axis direction. You. In focusing, the coils 40, 40 are controlled based on the focus error signal.
Is supplied with a current in a predetermined direction, so that the magnets 43, 4
As a result of the attraction or repulsion due to the electromagnetic interaction with the magnetic field provided by 3, the lens holder 37 (objective lens 36) is moved either in a direction toward or away from the recording surface of the optical disc D.

The remaining reflected laser beam Rrb reflected by the beam splitter 16 passes through the optical path 9
It is bent by 0 °, given a predetermined convergence by the converging lens 22, and guided to a photodetector 23 used for detecting a track shift and an offset amount.

The two light receiving areas 2 of the photo detector 23
Each of the signals photoelectrically converted by 3a and 23b is used for generating a track shift signal by applying a well-known push-pull method, as will be described later in detail with reference to FIG. 2
Each signal photoelectrically converted by the two arc-shaped light receiving regions 24a and 24b is similarly applied to a well-known push-pull method, and is used to generate a signal indicating a degree of an offset component included in the track shift signal.

A track error signal is generated by the signal processing unit shown in FIG. 8 based on the track shift signal and the offset signal generated by the photo detector 23.
Track control, that is, tracking, is performed to eliminate a deviation between the focus of the spot converged by the objective lens 36 and the center of the groove g on the recording surface of the optical disc D. In the tracking, current is supplied to the coils 41, 41 in a predetermined direction based on a track shift signal, which is a difference between outputs of the light receiving areas 23a and 23b of the photodetector 23, so that the magnets 44, 44 provide the tracking. As a result of attraction or repulsion due to electromagnetic field interaction with the applied magnetic field, the lens holder 37 (objective lens 36) is shifted toward the center of the optical disc D in the radial direction in the direction orthogonal to the groove g along the recording surface of the optical disc D or the outer periphery. Moved closer to one. Also, the arc-shaped light receiving area 24a
And 24b based on the offset signal which is the difference between the outputs
The magnitude of the current supplied to the coils 41 is corrected.

Meanwhile, an optical disk (DVD, groove g) for high-density digital recording, which has a higher recording density than that of a conventionally used music optical disk (CD), and on which video information is recorded, has been used. Is generally 1.
48 μm (hereinafter referred to as μm), and a DVD-RAM capable of writing and reproducing information at a recording density equivalent to that of a DVD is being put into practical use. Since the distance is compressed, the occurrence of the offset increases the crosstalk between the adjacent groove g and the offset component included in the track shift signal must be sufficiently removed. The two light receiving regions 24a and 24b near the center of the photodetector 23 are all or a part of the region where the 0th-order diffracted light component and the 1st-order diffracted light component overlap and the region where the 0th-order diffracted light component and the -1st-order diffracted light component overlap. Since all or a part of the laser beam is photoelectrically converted, it is useful for correcting an offset component included in the track shift signal obtained by the photodetector 23.

More specifically, the 0th-order diffracted light of the reflected laser beam Rrb applied to the photodetector 23 has its outer peripheral portion blurred by the objective lens 36, but as described below with reference to FIG. Since the laser beam substantially corresponds to the center of the laser beam, it has a sufficient light intensity.

That is, although the light receiving areas of the arc-shaped light receiving areas 24a and 24b of the photodetector 23 are smaller than the light receiving areas of the light receiving areas 23a and 23b, for example, the photoelectric conversion obtained from each of the arc light receiving areas 24a and 24b. Since the signal is generated by the reflected laser beam Rrb having a high light intensity passing through the center of the objective lens 36, even if the center between the reflected laser beam Rrb and the groove g is slightly shifted, the arc-shaped light receiving area is formed. 24
This is reflected as a sharp increase or decrease in one of the outputs a and 24b. The outer shape and area of the light receiving regions 24a and 24b are determined according to the specifications of the optical disk D, the wavelength of the laser beam Rf emitted from the semiconductor laser 11, the aperture ratio and imaging characteristics of the objective lens 36, and the optical design of the fixed optical system 3a. It is easily obtained from the specifications.

The offset signal obtained in this manner is applied to the light receiving areas 23a and 23a of the photodetector 23.
Correcting the position of the objective lens 36 by subtracting from the track shift signal output by b to generate a corrected track shift signal, that is, a track error signal, enables proper track control.

As a result, the laser beam Rrb passing through the center of the objective lens 36 and the center of the groove g of the optical disk D can be accurately matched. FIG. 6 shows that the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light of the reflected laser beam Rr reflected on the recording surface of the high-density optical disc D for DVD and DVD-RAM are the objective lenses 36.
FIG. 4 is a schematic view schematically illustrating a state where the information is guided by the user.

As shown in FIG. 6, the reflected laser beam Rr reflected by the groove g on the recording surface of the optical disc D
Are the 0th-order diffracted light that passes through substantially the entire area of the objective lens 36, the 1st-order diffracted light that partially overlaps the 0th-order diffracted light, and −
The light is incident on the objective lens 36 as an aggregate of the first-order diffracted light, the high-order diffracted light including the second-order not shown, and the high-order diffracted light including the second-order.

As is apparent from FIG. 6, each of the first-order diffracted light and the -1st-order diffracted light has a portion overlapping with the 0th-order diffracted light. That is, as described above, in a high-density optical disc for DVD or DVD-RAM,
Since the distance between adjacent grooves g is configured to be narrower than that of a well-known music CD or the like, each of the first-order diffracted light and the −1st-order diffracted light partially overlaps with the zero-order diffracted light, and furthermore, Parts of each other overlap.
In the region where the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light each overlap, the 0th-order diffracted light is a laser beam substantially corresponding to the center of the reflected laser beam Rr as described above. When the center of the reflected laser beam Rr passing through the center of the objective lens 36 and the center of the groove g are slightly displaced,
A steep change in light intensity can be provided in each of the region where the 0th-order diffracted light and the 1st-order diffracted light overlap and the region where the 0th-order diffracted light and the -1st-order diffracted light overlap.

More specifically, since each of the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light is partially blocked by the aperture of the objective lens 36, only a part of the reflected laser beam Rr is Through the fixed optical system 3a.

That is, the zero-order diffracted light is guided to the two light receiving areas 23a and 23b of the photodetector 23 shown in FIG. 7, for example, with the peripheral portion of the reflected laser beam before incidence on the objective lens 36 being cut off. On the other hand, the first-order diffracted light and the -1st-order diffracted light respectively enter the two light receiving regions 23a and 23b of the photodetector 23 while overlapping with the 0th-order diffracted light. That is, a difference between the photoelectric conversion signals from the two light receiving regions 23a and 23b is a track shift signal.

Therefore, if there is a condensed spot at a position where the center of the condensed spot of the laser beam converged on the optical disk D by the objective lens 36 and the center of the groove g, if there is a condensed spot in the groove g in the radial direction Since a symmetrical diffracted light is generated, the difference signal between the output signals from the two light receiving areas is at the 0 level. Will shift.

FIG. 7 is a plan view showing the light receiving surface of the photodetector 23. As shown in FIG. 7, the photodetector 23 is used for generating a well-known track error signal, and sets two light receiving regions 23a and 23b divided by a dividing line 23c and a dividing line 23c as axes of symmetry. And two arc-shaped light receiving regions 24a and 24b arranged symmetrically with respect to the dividing line 23c by the arcuate dividing lines 23d and 23e. The outer contours of the arc-shaped light receiving regions 24a and 24b, that is, the dividing lines 23d and 23e are coincident with the above-mentioned regions where all of the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light of the reflected laser beam Rr overlap. The dividing lines 23c are arranged so as to be substantially parallel to the direction in which the shadow of the groove g of the optical disc D is projected.

FIG. 8 is a schematic block diagram showing an example of a signal processing unit and a control unit which can be used for the signal processing unit 5 and the control unit 9 of the optical disk device 1 shown in FIG. As shown in FIG. 8, the signal processing unit 5 is connected to the main control circuit 50, and reproduces information recorded on the optical disc D based on outputs from four light receiving areas (not shown) of the photo detector 20. The circuit 51 is provided. In addition,
The information reproducing circuit 51 includes, for example, a threshold circuit (not shown), a binarizing circuit, a data expanding circuit, a buffer memory, and the like, and a current-voltage converting circuit described in detail later.
The information corresponding to the output from each light receiving area converted into a voltage signal by the differential amplifier and the adder is transmitted to the main control circuit 50.
And outputs it to the external device 99 via.

On the other hand, the control unit 9 includes a linear motor control circuit 61 for supplying a current in a predetermined direction to the radial drive coil 34 for moving the actuator 3b in the radial direction of the optical disk D, and an objective lens 36 for controlling the recording surface of the optical disk D. A focus error detection circuit 62 for setting a current value to be supplied to the two coils 40, 40 on the cylindrical surface of the lens holder 37 in order to move in a direction perpendicular to the direction of movement of the lens holder 37, and removing a focus error detected by the focus error detection circuit 62. A focus control circuit 63 for supplying a focus control current to the coils 40 and 40, and a cylindrical surface 2 of the lens holder 37 for moving the objective lens 36 in a direction intersecting the tangent to the groove g on the recording surface of the optical disc D. Track offset and offset for setting the current value to be supplied to the two coils 41, 41 The detection circuit 64, a coil in order to remove the outputted track deviation and offset from the track deviation and offset detection circuit 64 41,
It has a track control circuit 65 for supplying a track control current and a laser drive circuit 66 for setting the light intensity of the laser beam emitted from the semiconductor laser 11 to a predetermined intensity. Each circuit is connected to the main control circuit 50.

The information reproducing circuit 51 is connected to each of four light receiving regions (not shown) of the photodetector 20, and converts the output current output from each light receiving region into a voltage by a first to fourth current-voltage converters. The added output of the adder 72 for obtaining the sum of the voltage signals output from each of 71a to 71d is input.

The focus error detection circuit 62 has a first
And first and second differential amplifiers 73a and 73a for obtaining a differential output between two predetermined outputs among the output voltages output from the fourth to fourth current-voltage converters 71a to 71d.
An output obtained by adding each output of 73b by an adder 74 is input.

Track deviation and offset detection circuit 6
4 and the linear motor control circuit 61 respectively have light receiving areas 23a, 24a and 2a of the photodetector 23.
A signal obtained by subjecting the current output from each of 3b and 24b to current-to-voltage conversion by each of the fifth to eighth current-to-voltage converters 81a to 81d, and processing the resulting signal by a predetermined combination. A signal is input. As shown in the figure, an example of the combination is the output from the light receiving area 23a of the photodetector 23, that is, the fifth output.
Of the arc-shaped light receiving region 2
4a, that is, the sixth current-voltage converter 81b
And the light receiving area 23b.
, Ie, the output of the seventh current-voltage converter 81c, the output from the arc-shaped light receiving region 24a, ie, the output obtained by adding the output of the eighth current-voltage converter 81d by the adder 82b, to the adder 83. Are further added to generate a first difference signal, and the adder 84 generates the two difference light receiving regions 24a.
, 24b, that is, the difference between the outputs of the sixth and seventh current-voltage converters 81b, 81c, and the differential amplifier 85 calculates the difference between the first difference signal generated by the adder 83 and the output of the adder 84. A second difference signal whose difference from the output is obtained is input.

As described above, according to the optical head device 3 shown in FIGS. 2 to 7, the track shift of the objective lens 36 is different from the output from the light receiving area 23a of the photodetector 23 added by the adder 82b. A differential amplifier 84 is obtained from a first difference signal obtained by subtracting the output from the light receiving region 23b of the photodetector 23 added by the adder 82a from the output from the circular light receiving region 24a and the output from the circular light receiving region 24b. The difference between the outputs of the two arc-shaped light receiving regions 24a and 24b closer to the center of the photodetector 23 obtained by the above is displayed by a second difference signal obtained by subtraction by the differential amplifier 85.

As described above, the track shift amount obtained by the adder 83 and the offset amount detected by the differential amplifier 84 are calculated by the track shift and offset detection circuit 64, whereby the lens of the objective lens 36 is obtained. Due to the shift, it is possible to compensate for the offset amount that acts as a track error, that is, the influence of the offset component included in the track shift signal. Therefore, crosstalk in a high-density optical disk represented by an optical disk for DVD and DVD-RAM can be significantly reduced. The combination of the outputs of the adder and the differential amplifier described above is obtained, for example, by adding the outputs of the fifth and eighth current-voltage conversion circuits 81a and 81d by the differential amplifier 86 as shown in FIG. The output of the differential amplifier 84 may be removed again by the differential amplifier 85 from the signal obtained by adding the output signal obtained by the differential amplifier 84 and the output signal obtained by the differential amplifier 84 by the adder 87.

FIGS. 10 and 11 are graphs showing the output from the photodetector shown in FIG. 7 and the track error signal provided from the signal processing unit and the control unit shown in FIG. 8, respectively.

As is apparent from FIG. 11, the offset component included in the track shift signal output from the light receiving regions 23a and 23b of the photodetector 23 using the outputs of the arc-shaped light receiving regions 24a and 24b of the photodetector 23. , Track shift and offset detection circuit 64
As a result, the center value of the track shift signal input to the track control circuit 65 approaches 0 as compared with the conventional track error signal including the influence of the lens shift indicated by the dotted line in FIG. Is recognized.

FIG. 12 is a schematic block diagram showing another example of the signal processing unit and the control unit shown in FIG. As shown in FIG. 12, a gain controller 88 for matching the output signal level between the output of the adder 83 and the differential amplifier 84 is provided between the differential amplifier 84 and the differential amplifier 85,
The magnitude of the offset component included in the track shift signal is equal to the arc-shaped light receiving area 24a at the center of the photodetector 23.
, 24b and the outer light receiving areas 23a and 23b
It is possible to prevent an output as if an offset has occurred or does not exist due to the difference between the output signal levels 3b.

FIG. 13 is a schematic block diagram showing another example of the signal processing unit and the control unit shown in FIG. As shown in FIG. 13, with respect to the output of either the sixth or seventh current-voltage conversion circuit 81b or 81c for current-voltage conversion of the respective outputs of the light receiving regions 24a and 24b,
By connecting the gain controller 89, the light receiving area 2
It is possible to correct a difference in output level caused by a difference in area between 4a and 24b or an error in assembling inherent to the optical head device 3.

By using the signal processing section and the control section shown in FIG. 13, the offset component contained in the track error signal can be converted into the light receiving area 2 at the center of the photodetector 23.
It is as if an offset is generated or present due to a difference between the areas generated when the 4a and 24b are manufactured or a difference between the output signals of the respective light receiving regions due to an error in assembling inherent to the optical head device 3. It is possible to prevent the output that does not occur from being output.

FIG. 14 is a schematic block diagram showing another example of the signal processing section and the control section shown in FIG. As shown in FIG. 14, between the differential amplifier 84 and the differential amplifier 85,
A gain controller 88 for matching the output signal level between the output of the adder 83 and the differential amplifier 84 is provided, and the sixth or seventh current-to-voltage conversion of the output of each of the light receiving regions 24a and 24b is performed. Voltage conversion circuit 8
By connecting a gain controller 89 to either output 1b or 81c, the light receiving areas 24a and 24c
This makes it possible to correct a difference in output level due to an area difference between the optical head device b and an error during assembling inherent to the optical head device 3. That is, the magnitude of the offset component included in the track error signal is output as if an offset occurs or does not exist due to the output signal level of the photodetector 23, and the magnitude of the offset component is included in the track error signal. The offset component caused by the difference in the area caused by the manufacturing reasons of the two light receiving regions of the photodetector 23 or the difference between the output signals of the respective light receiving regions due to an error at the time of assembly inherent to the optical head device 3, It is possible to prevent an output as if an offset occurs or does not exist.

FIGS. 15 and 16 are graphs showing an output from the photodetector shown in FIG. 7 and a track error signal provided by the signal processing unit and the control unit shown in FIG. 14, respectively.

As is apparent from FIG. 16, the offset component included in the track shift signal output from the light receiving regions 23a and 23b of the photodetector 23 is determined by using the outputs of the arc-shaped light receiving regions 24a and 24b of the photodetector 23. , Track shift and offset detection circuit 64
And the difference between one area and the other area of the light receiving areas 23a and 23b of the photodetector 23, the deviation of the output level inherent to the optical head device 3, and the light receiving areas 23a and 23b and the circular light receiving area. 2
Eliminating the output associated with an element that apparently changes the magnitude of the output level, such as due to the difference in output level between 4a and 24b, includes the effect of the lens shift shown by the dotted line in FIG. Compared with the conventional track error signal, the center value of the track shift signal input to the track control circuit 65 can be approximated to almost zero.

[0080]

As described above, according to the optical head device of the present invention, the output of the offset component contained in the track error signal is removed from a part of the light receiving area of the photodetector for detecting the track error signal. By providing the light receiving area for detecting the offset component, the light of the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light of the reflected light reflected from the optical disk can be used to generate the track error signal. , The influence of the lens shift on the track error signal can be removed, and stable tracking control can be performed.

According to the optical head device of the present invention,
The respective outputs of the arc-shaped light receiving area for detecting the offset component and the light receiving area for detecting the track shift are set to appropriate sizes by the gain controller. Therefore, a photodetector capable of detecting the offset component can be provided at low cost, and the offset component is not detected or its size is prevented from being changed due to the output of the photodetector.

Further, according to the optical head device of the present invention, the optical head device may be caused by a difference between the areas of the two light receiving regions used for detecting the offset component, component accuracy of elements of the optical head device, or assembly of the optical head device. Is set to an appropriate magnitude by the gain controller. Therefore, there is no increase in assembly cost and component cost for detecting the offset component.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an optical disk device having an optical head device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an optical head device incorporated in the optical disk device shown in FIG.

FIG. 3 is a schematic diagram showing an example of an actuator of the optical head device shown in FIG. 2;

FIG. 4 is a schematic diagram showing an example of a fixed optical system of the optical head device shown in FIG.

FIG. 5 is a schematic diagram illustrating a lens holder of the actuator shown in FIG. 3 and its vicinity.

FIG. 6 is a schematic diagram illustrating a state of a reflected laser beam from the optical disc returned to the objective lens of the actuator shown in FIGS. 3 and 5;

7 is a schematic plan view showing a light receiving area of a photodetector used for detecting a track shift capable of detecting an offset component included in the reflected laser beam shown in FIG. 6 in the fixed optical system shown in FIG.

FIG. 8 is a schematic block diagram illustrating an example of a signal processing unit and a control unit that can be used in the signal processing unit and the control unit of the optical disc device illustrated in FIG. 1;

FIG. 9 is a schematic block diagram illustrating another example of the signal processing unit and the control unit illustrated in FIG. 8;

FIG. 10 is a graph showing an offset amount obtained by the photodetector shown in FIG. 7;

11 is a graph showing an output from the photodetector shown in FIG. 7 and a track shift signal provided by the signal processing unit and the control unit shown in FIG. 8;

FIG. 12 is a schematic block diagram illustrating another example of the signal processing unit and the control unit illustrated in FIG. 8;

FIG. 13 is a schematic block diagram showing still another example of the signal processing unit and the control unit shown in FIG. 8;

FIG. 14 is a schematic block diagram showing still another example of the signal processing unit and the control unit shown in FIG. 8;

FIG. 15 is a graph showing an offset amount obtained by the photodetector shown in FIG. 7 and the signal processing unit and the control unit shown in FIG. 14;

16 is a graph showing an output from the photodetector shown in FIG. 7 and a track shift signal provided by the signal processing unit and the control unit shown in FIG. 14;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk apparatus, 3 ... Optical head apparatus, 3 ... Optical head apparatus, 3a ... Fixed optical system, 3b ... Actuator, 5 ... Signal processing part, 7 ... Motor, 9 ... Control part, 10 ... Housing, 11 ... Semiconductor laser Reference numeral 12: Collimator lens, 13: Elliptical correction prism, 14: Beam splitter (polarization), 15: λ / 4 plate (phase delay element), 16: Beam splitter (half mirror), 17: Convergent lens, 18: Concave lens Reference numeral 19: cylindrical lens, 20: photodetector, 21: mirror, 22: converging lens, 23: photodetector, 23a: light receiving area (track error detection), 23b: light receiving area (track error detection), 24a: arc-shaped light receiving area ( Offset detection), 24b: arc-shaped light receiving area (offset detection), 31: base, 3 ... guide rail, 33 ... carriage, 34 ... radial drive coil, 35 ... raising mirror, 36 ... objective lens, 37 ... lens holder 38 ... lens holder base, 39 ... axis, 40 ... coil, 41 ... coil, 42 ... yoke 43: magnet, 44: magnet, 50: main control circuit, 51: information reproducing circuit, 61: linear motor control circuit, 62: focus error detection circuit, 63: focus control circuit, 64: track deviation and offset detection circuit, 65: track control circuit, 66: laser drive circuit, 71a: current-voltage conversion circuit, 71b: current-voltage conversion circuit, 71c: current-voltage conversion circuit, 71d: current-voltage conversion circuit, 72: adder, 73a ... Differential amplifier, 73b ... Differential amplifier, 74 ... Adder, 81a ... Current-voltage conversion circuit, 81 b: current-voltage conversion circuit, 81c: current-voltage conversion circuit, 81d: current-voltage conversion circuit, 82a: adder, 82b: adder, 83: differential amplifier, 84: differential amplifier, 85: differential Amplifier 86: Differential amplifier 87: Differential amplifier 88: Gain controller 89: Gain controller D: Optical disk g: Groove

Claims (9)

[Claims] A semiconductor laser for supplying a light beam to a recording medium; an objective lens for condensing a light beam emitted from the semiconductor laser on the recording medium; And a photoelectric conversion unit for converting the reflected light beam into an electric signal, wherein the photoelectric conversion unit is configured such that a condensed spot obtained by being converged by the objective lens is arranged in a radial direction of the recording medium. When the recording medium is moved, the recording medium is divided into at least two light receiving regions by a dividing line defined in a direction substantially perpendicular to a direction in which a reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion means and moves. The reflected light beam is photoelectrically converted by a predetermined light receiving region among light receiving regions divided by the division line. A first difference signal which is a difference between an electric conversion signal and a photoelectric conversion signal obtained by photoelectrically converting the reflected light beam by a light receiving region forming a pair with the predetermined light receiving region among the light receiving regions divided by the division line. From the first difference signal, the condensed spot is defined as 0 of the light beam diffracted by the recording medium.
The first-order diffracted light, the first-order diffracted light, and the -1st-order diffracted light overlap each other, and the reflected light beam is photoelectrically converted by a predetermined light receiving area among the light receiving areas divided by the division line, and the division is performed. An output obtained by removing a second difference signal that is a difference between the reflected light beam and a photoelectrically converted signal obtained by photoelectrically converting the reflected light beam by a light receiving region paired with the predetermined light receiving region among light receiving regions divided by a line. An optical head device, wherein the signal is a tracking error signal. 2. A semiconductor laser for supplying a light beam to a recording medium, an objective lens for converging a light beam emitted from the semiconductor laser on the recording medium, and an objective lens reflected and diffracted from the recording medium. And a photoelectric conversion unit for converting the reflected light beam into an electric signal, wherein the photoelectric conversion unit is configured such that a condensed spot obtained by being converged by the objective lens is arranged in a radial direction of the recording medium. When the recording medium is moved, the recording medium is divided into at least two light receiving regions by a dividing line defined in a direction substantially perpendicular to a direction in which a reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion means and moves. The reflected light beam is photoelectrically converted by a predetermined light receiving region among light receiving regions divided by the division line. A first difference signal which is a difference between an electric conversion signal and a photoelectric conversion signal obtained by photoelectrically converting the reflected light beam by a light receiving region forming a pair with the predetermined light receiving region among the light receiving regions divided by the division line. From the first difference signal, the condensed spot is defined as 0 of the light beam diffracted by the recording medium.
The first-order diffracted light, the first-order diffracted light, and the -1st-order diffracted light overlap each other, and the reflected light beam is photoelectrically converted by a predetermined light receiving area among the light receiving areas divided by the division line, and the division is performed. A second difference obtained by amplifying or reducing, by a predetermined value, a difference between a photoelectric conversion signal obtained by photoelectrically converting the reflected light beam by a light receiving region forming a pair with the predetermined light receiving region among light receiving regions divided by a line; An optical head device wherein an output signal obtained by removing a signal is used as a tracking error signal. 3. A semiconductor laser for supplying a light beam to a recording medium, an objective lens for condensing a light beam emitted from the semiconductor laser on the recording medium, and an objective lens reflected and diffracted from the recording medium. And a photoelectric conversion unit for converting the reflected light beam into an electric signal, wherein the photoelectric conversion unit is configured such that a condensed spot obtained by being converged by the objective lens is arranged in a radial direction of the recording medium. When the recording medium is moved, the recording medium is divided into at least two light receiving regions by a dividing line defined in a direction substantially perpendicular to a direction in which a reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion means and moves. An arc-shaped outer dividing line defined symmetrically with the dividing line as an axis of symmetry in each of the photoelectric conversion region and the at least two light receiving regions. And at least two arc-shaped light receiving regions divided by the dividing line. The photoelectric conversion signal obtained by photoelectrically converting the reflected light beam by a predetermined light receiving region among the light receiving regions divided by the dividing line and the dividing line A first difference signal which is a difference between a photoelectric conversion signal obtained by photoelectrically converting the reflected light beam and a photoelectric conversion signal obtained by the light receiving region forming a pair with the predetermined light receiving region among the divided light receiving regions is obtained. From the signal, the condensed spot is detected as 0% of the light beam diffracted by the recording medium.
Each of the first-order diffracted light, the first-order diffracted light, and the -1st-order diffracted light amplifies or reduces, by a predetermined value, one of the photoelectric conversion signals obtained by photoelectrically converting the reflected light beam by the first and second arc-shaped light receiving regions. An output signal obtained by removing a second difference signal which is a difference from the remaining one of the photoelectric conversion signals obtained by photoelectrically converting the reflected light beam by the first and second arc-shaped light receiving regions is obtained. An optical head device, wherein a tracking error signal is used. 4. A semiconductor laser for supplying a light beam to a recording medium, an objective lens for condensing a light beam emitted from the semiconductor laser on the recording medium, and a semiconductor laser reflected and diffracted from the recording medium. And a photoelectric conversion unit for converting the reflected light beam into an electric signal, wherein the photoelectric conversion unit is configured such that a condensed spot obtained by being converged by the objective lens is arranged in a radial direction of the recording medium. When the recording medium is moved, the recording medium is divided into at least two light receiving regions by a dividing line defined in a direction substantially perpendicular to a direction in which a reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion means and moves. An arc-shaped outer dividing line defined symmetrically with the dividing line as an axis of symmetry in each of the photoelectric conversion region and the at least two light receiving regions. And at least two arc-shaped light receiving regions divided by the dividing line. The photoelectric conversion signal obtained by photoelectrically converting the reflected light beam by a predetermined light receiving region among the light receiving regions divided by the dividing line and the dividing line A first difference signal which is a difference between a photoelectric conversion signal obtained by photoelectrically converting the reflected light beam and a photoelectric conversion signal obtained by the light receiving region forming a pair with the predetermined light receiving region among the divided light receiving regions is obtained. From the signal, the condensed spot is detected as 0% of the light beam diffracted by the recording medium.
Each of the first-order diffracted light, the first-order diffracted light, and the -1st-order diffracted light amplifies or reduces, by a predetermined value, one of the photoelectric conversion signals obtained by photoelectrically converting the reflected light beam by the first and second arc-shaped light receiving regions. The difference between the reflected light beam and the other one of the photoelectrically converted signals obtained by photoelectrically converting the reflected light beam by the first and second arc-shaped light receiving regions, and further amplifying or reducing the difference by a predetermined value. An optical head device wherein an output signal obtained by removing a signal is used as a tracking error signal. 5. A plurality of light receiving areas of said photoelectric conversion means are arranged symmetrically with first and second light receiving areas divided only by said dividing line, and said dividing line as an axis of symmetry,
3. The light-receiving device according to claim 1, further comprising third and fourth light-receiving regions further divided by two arc-shaped dividing lines that divide the respective predetermined regions of the first and second light-receiving regions. The optical head device according to any one of the above. 6. The arc-shaped parting line may be one of
6. The optical head device according to claim 5, wherein the first-order light component and the minus first-order light component coincide with an outline defined by a region overlapping each other. 7. The optical head device according to claim 5, wherein said first light receiving area and said third light receiving area are respectively located on the same side divided by said dividing line. 8. The arc-shaped contour parting line is coincident with a contour defined by a region where the primary light component and the −1st light component overlap each other. Or the optical head device according to any one of 4. 9. A light source that emits a light beam, a polarizing beam splitter that guides the light beam emitted from the light source toward a recording medium, and a light beam that has passed through the polarizing beam splitter has a predetermined shape. An objective lens for giving image characteristics to converge on a recording surface of a recording medium; a track control coil for generating a propulsive force for moving the objective lens in a direction orthogonal to a guide groove specific to the recording medium; The light beam converged on the recording surface of the recording medium, reflected by the recording surface, and passed through the objective lens again is reflected by the polarizing beam splitter and separated from the light beam traveling toward the objective lens. A non-polarizing beam splitter that functions as a half mirror that splits light into two light beams having substantially the same light intensity, and a shadow of a guide groove specific to the recording medium. The divided by dividing lines extending along the direction to be projected first and second 2
Two light receiving areas divided into two light receiving areas and first and second light receiving areas divided by an arc-shaped outer dividing line symmetrically defined with the dividing line as a symmetry axis in the first and second light receiving areas. A light beam split by the non-polarizing beam splitter is received by the first and second light receiving regions, photoelectrically converted, and converged by the center of a guide groove unique to a recording medium and the objective lens. A track error signal indicating the degree of deviation from the center of the light beam to be generated is generated. A light beam applied to an area where the first-order diffracted light and the -1st-order diffracted light overlap each other is received and photoelectrically converted, and the center of the guide groove unique to the recording medium and the center of the light beam converged by the objective lens are determined. of A photodetector for generating a signal corresponding to an offset component in the track error signal indicating the degree of the error, and the first and second circles being output from the first and second light receiving regions of the photodetector, respectively. An output signal output from each of the first and second arc-shaped light receiving regions is obtained from a difference signal between two signals obtained by adding outputs output from each of the arc-shaped light receiving regions based on a predetermined combination. A track shift and offset detection circuit for subtracting the mutual difference signal to determine the actual degree of shift between the center of the guide groove specific to the recording medium and the center of the light beam converged by the objective lens; A current in a predetermined direction is applied to the track control coil based on the track shift signal obtained by the shift and offset detection circuit. An optical head device, comprising: