JPH1064095A - Recording and reproducing device and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the skew amount of a data readout position. SOLUTION: After the laser beam emitted from a laser diode 21 is shaped into parallel beams in a collimating lens 22, the beams pass a beam splitter 23 to enter a hologram element 24. The hologram 24 transmits the major part of the beams as they are without diffracting them (a zeroth-order light) and also emits remaining laser beams by diffracting them (a first-order diffracted light). An objective lens 25 condenses the zeroth-order light on the recording surface of an optical disk and also irradiates the optical disk with the first-order diffracted light. The zeroth-order light reflected on the recording surface of the optical disk is received in a photodetector(PD) 27 to be converted into a signal in accordance with data on the optical disk. Besides, the first-order diffracted light generated in the hologram element 24 is received by the PD 27 as a stray light including information of the skew amount of the optical disk to be converted into a signal corresponding to the skew amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording and reproducing apparatus and method, and more particularly, to a recording and reproducing apparatus and method,
The recording medium is irradiated with a first light beam for information recording and reproduction and a second light beam for detecting the inclination of the recording medium, and the first and second light beams reflected by the recording medium are irradiated with the first and second light beams. And a method for adjusting the tilt of the recording medium in accordance with a signal corresponding to the tilt of the recording medium calculated from the output of the second light receiving section.

[0002]

2. Description of the Related Art In response to the increase in the capacity of information accompanying the progress of electronic technology, the density of optical disks used as recording media for computers and package media for image information has been increased.

In order to increase the density of an optical disk, it is conceivable to reduce the width or interval of a track, reduce the size of a pit, or reduce the interval between pits.

As described above, in an apparatus for reproducing or recording data on a high-density optical disk, the numerical aperture NA of the objective lens of the optical pickup is increased so that the laser light is focused on finer pits. I have.

At this time, a laser beam is focused on a recording surface via a transparent substrate of an optical disk (for example, in the case of a compact disk (CD), the thickness of the substrate is 1.2 mm), and the reflected light is detected. Then, the information recorded on the optical disk is reproduced.

When reproducing the optical disk, aberration occurs when the optical axis of the objective lens is inclined with respect to the recording surface of the optical disk (ie, deviates from 90 degrees). In this case, in particular, 3
The next coma is dominant and occurs in proportion to the third power of the numerical aperture and the first power of the skew amount θ. The wavefront at this time is represented by the following equation. W (x, y) = W31 · x · (x ² + y ² )

W31 represents the third-order Seidel's coma, and is represented by the following equation (provided that θ is sufficiently small). W31 = (n ² −1) / (2n ² ) · t · θ · NA ³ / λ

Here, t is the thickness of the substrate of the optical disk,
n represents the refractive index of the substrate.

Therefore, for example, D which is higher in density than CD
VD (Digital Versatile Disc) with a numerical aperture NA of 0.
In the case of reproducing using a 6 objective lens and reproducing a CD even with the same skew amount (NA = 0.45)
About 3.5 times the aberration occurs.

[0010] Furthermore, when inexpensive mass-produced polycarbonate is used for disks, the skew amount is ± 0,0.
Since it is about 5 to 1 degree, if the reproduction is performed as it is, the shape of the spot of the laser beam focused on the optical disk is distorted, the intersymbol interference increases, and the reproduction of information becomes difficult.

Therefore, in an apparatus for reproducing or recording data on such an optical disk, a skew sensor for detecting skew, and the position of an optical pickup or an objective lens (angle with respect to the optical disk) according to a detection signal from the skew sensor. There is a servo mechanism for adjusting the skew and correcting the skew.

FIG. 18 shows an example of the skew sensor 61. In this skew sensor 61, an LED
81 emits a predetermined light beam to the optical disc 41,
The two-segment photodetector 82 receives the light emitted from the LED 81 and reflected on the optical disk 41 by two light receiving units.

Then, as shown in FIG. 19, the two-segment photodetector 82 outputs an electric signal corresponding to the amount of light received by the two light receiving units to the arithmetic circuit 62, respectively. The arithmetic circuit 62 is a two-part photodetector 82
The difference between the signals from the two light receiving units is calculated and output to a predetermined control circuit (not shown) as a skew detection signal.

By doing so, the optical disk 4
Since the ratio of the reflected light incident on the two light receiving units of the two-segment photodetector 82 changes according to the inclination of 1 (that is, the skew), the skew is calculated from the difference in the amount of the reflected light received by the two light receiving units. You can know the quantity.

FIG. 20 shows an example of the correspondence between the skew amount of the optical disk 41 and the skew detection signal. FIG.
As shown by 0, when the skew amount is small (when the skew amount is about −2 degrees to about 2 degrees), the skew detection signal is almost proportional to the skew amount. Adjust the pickup angle to correct the skew.

FIG. 21 shows an example of a skew correction mechanism. In the correction mechanism of FIG.
Drives the worm gear 91 in accordance with a control signal supplied from a predetermined control circuit in response to the skew detection signal detected by the above-described skew sensor 61, and drives the worm gear 91 via the gear 92 and the gear 93 to the base 95. The cam 94 in contact is rotated.

The objective lens 25 and the skew sensor 61
Is disposed rotatably about a shaft 97 and rotates according to the eccentricity of the cam 94. Further, a spring 96 is provided between the base 95 and a housing (not shown) so that the cam 94 and the base 95 are kept in contact with each other.

By doing so, the cam 94 rotates in response to the signal supplied to the motor 71, and the base 95 rotates accordingly, and the objective lens 25 and the skew sensor 61 with respect to the optical disk 41 The angle is adjusted.

FIG. 21 shows only a correction mechanism for one axis, but actually, a correction mechanism is provided for the other axis. As described above, the correction mechanism is provided for the two axes to correct both the radial skew (radial skew) and the tangential skew (tangential skew) of the optical disk 41.

FIG. 22 shows another example of the skew correction mechanism. In the correction mechanism shown in FIG.
Drives the worm gear 101 according to a control signal supplied from a predetermined control circuit in response to the skew detection signal detected by the above-described skew sensor 61, and
2, the objective lens 25 and the skew sensor 61
Arm 10 in contact with base 95 provided with
4 is rotated.

The optical pickup 105 and the above-described drive system (such as the motor 71) are rotatably arranged around a shaft 107, and rotate according to the position of the arm 104 of the gear 103. Also, the base 95 and the optical pickup 1 are arranged so that the arm 104 and the base 95 are kept in contact with each other.
A spring 106 is provided between 05.

In this manner, the angles of the objective lens 25 and the skew sensor 61 with respect to the optical disk 41 are adjusted in accordance with the signal supplied to the motor 71.

FIG. 22 shows only a correction mechanism for one axis, but actually, a correction mechanism is similarly provided for the other axis. As described above, the correction mechanism is provided for the two axes to correct both the radial skew (radial skew) and the tangential skew (tangential skew) of the optical disk 41.

FIG. 23 shows still another example of the skew correction mechanism. In the correction mechanism shown in FIG. 23, the motor 71 drives the worm gear 111 according to a control signal supplied from a predetermined control circuit in response to the skew detection signal detected by the skew sensor 61 described above. Via a cam 1 that is in contact with a drive shaft 114 used for moving the optical pickup 105
13 is rotated.

The objective lens 25 and the skew sensor 61
As shown in FIG. 23, the drive shaft 114 provided with the optical pickup 105 having the
3 rotates according to the eccentricity.

In this way, the angle of the optical pickup 105 with respect to the optical disk 41 is adjusted in accordance with the signal supplied to the motor 71.

FIG. 24 shows still another example of the skew correction mechanism. 24, the motor 71 drives the worm gear 121 according to a control signal supplied from a predetermined control circuit in response to the skew detection signal detected by the skew sensor 61 described above. , The optical pickup 105 rotates the cam 123 which is in contact with the subunit 124 slidably provided.

The sub-unit 124 includes a shaft 125
, And rotates in accordance with the eccentricity of the cam 123.

In this way, the angle of the optical pickup 105 provided with the objective lens 25 and the skew sensor 61 with respect to the optical disk 41 is adjusted in accordance with the signal supplied to the motor 71.

FIG. 25 shows still another example of the skew correction mechanism. In the correction mechanism shown in FIG. 25, the motor 71 drives the worm gear 131 in accordance with a control signal supplied from a predetermined control circuit in response to the skew detection signal detected by the skew sensor 61 described above. The cam 134 that is in contact with a base 136 provided with a spindle motor 135 for rotating the optical disc 41 is rotated via the gear 133 and the gear 133.

The base 136 is a mechanical deck 138
Is rotatably disposed about a shaft 137 as a contact portion with the cam 134, and rotates in accordance with the eccentricity of the cam 134. Also, cam 1
Base 13 so that base 34 and base 136 are kept in contact with each other.
A spring 139 is provided between 6 and the housing.

In this way, the inclination angles of the spindle motor 135 and the base 136 for rotating the optical disk 41 are adjusted according to the signal supplied to the motor 71.

As described above, the skew is corrected by operating the above-described skew correction mechanism in accordance with the signal detected by the skew sensor 61.

[0034]

However, since the skew sensor 61 is about 10 mm in diameter,
The measurement position of the skew sensor on the optical disk is different from the data reading position, and it is difficult to accurately measure the skew at the data reading position, and it is difficult to sufficiently correct the skew. .

In particular, when the numerical aperture NA of the objective lens is 0.6 or more, if the skew is not sufficiently corrected, the aberration increases, and the data recorded on the optical disk can be accurately reproduced. Is difficult.

Further, as described above, in the skew sensor using the LED and the photodetector, it is difficult to detect the skew amount with high reliability because the light emission pattern of the LED changes according to the temperature. Have a problem.

The present invention has been made in view of such a situation, and focuses a plurality of diffracted lights on a plurality of recording media, and generates a signal corresponding to the inclination of the recording medium from return light reflected by the recording medium. By calculating and adjusting the inclination of the recording medium in accordance with the signal, the skew amount at the data reading position can be detected, and the skew can be corrected accurately. . Further, since an LED such as the above-described skew sensor is not required, the skew amount can be detected with high reliability.

[0038]

According to a first aspect of the present invention, there is provided a recording / reproducing apparatus comprising: a generating means for generating a light beam; a first light beam for information recording / reproducing; Generating means for generating a second light beam for detecting the inclination of the medium, irradiating means for irradiating the recording medium with the first light beam and the second light beam, and generating the first light beam reflected by the recording medium. A first light receiving section for receiving light, a light receiving means having a second light receiving section for receiving a second light beam reflected by the recording medium, and information recorded on the recording medium from an output of the first light receiving section. Reproducing means for reproducing, and calculating means for calculating a signal corresponding to the inclination of the recording medium from the output of the second light receiving section;
Adjusting means for adjusting the inclination of the recording medium in accordance with the signal calculated by the calculating means.

The recording / reproducing method according to claim 8, wherein the step of generating a light beam, the first light beam for information recording / reproducing and the second light beam for detecting the inclination of the recording medium are performed based on the light beam. Generating a first light beam and a second light beam.
Irradiating the first light beam reflected by the recording medium with the first light receiving unit, and irradiating the second light beam reflected by the recording medium with the second light receiving unit. Receiving the light, reproducing the information recorded on the recording medium from the output of the first light receiving unit, calculating the signal corresponding to the inclination of the recording medium from the output of the second light receiving unit, Adjusting the tilt of the recording medium in response to the set signal.

In the recording / reproducing apparatus according to the first aspect, the generating means generates a light beam, and the generating means generates a first light beam for information recording / reproducing and a recording / reproducing operation from the light beam from the generating means. A second light beam for detecting the tilt of the medium is generated, the irradiating means irradiates the recording medium with the first light beam and the second light beam, and the light receiving means reflects the first light beam reflected by the recording medium.
Is received by the first light receiving unit, the second light beam reflected by the recording medium is received by the second light receiving unit, and the reproducing means records the output from the first light receiving unit on the recording medium. The arithmetic means calculates a signal corresponding to the tilt of the recording medium from the output of the second light receiving unit, and the adjusting means adjusts the tilt of the recording medium in accordance with the signal calculated by the calculating means. Adjust

In the recording / reproducing method according to the eighth aspect, a light beam is generated, and a first light beam for information recording / reproduction and a second light beam for tilt detection of the recording medium are generated from the light beam. The first light beam and the second light beam are generated and applied to the recording medium, and the first light beam reflected by the recording medium is received by the first light receiving unit, and the second light beam reflected by the recording medium is received by the first light receiving unit. The light beam is received by the second light receiving unit, information recorded on the recording medium is reproduced from the output of the first light receiving unit, and a signal corresponding to the inclination of the recording medium is calculated from the output of the second light receiving unit. Then, the inclination of the recording medium is adjusted according to the calculated signal.

[0042]

FIG. 1 shows a configuration of an embodiment of a recording / reproducing apparatus according to the present invention. In this embodiment, the optical pickup unit 1 has a built-in laser diode (L
D) A laser beam of a predetermined wavelength is generated by 21 (FIG. 2) (generating means), condensed on an optical disk 41 (for example, DVD) via a predetermined optical system (FIG. 2), and the reflected light (return light) light)
To a photodetector (PD) 27 having a plurality of light receiving sections.
(FIG. 2) The signal is detected by the (light receiving means), and the output signal of each light receiving section is output to the arithmetic circuit 2 (arithmetic means) as a PD output signal.

The arithmetic circuit 2 converts the PD output signal (signal from each light receiving section) into a data detection signal (RF signal) for reproducing the optical disk.
Signal), a focus error signal indicating a shift in focus of the laser beam in the optical axis direction, a tracking error signal indicating a shift in tracking in the radial direction of the optical disc, and a skew detection signal indicating an inclination (skew) of the optical disc, and data detection. The signal is output to the reproduction circuit 3 (reproduction means), and the focus error signal, the tracking error signal, and the skew detection signal are output to the control circuit 4 (adjustment means).

The reproduction circuit 3 equalizes the data detection signal supplied from the arithmetic circuit 2 and then binarizes the data detection signal. Further, the signal demodulated while performing error correction is used as a reproduction signal by a predetermined device (not shown). Output.

The control circuit 4 controls the focus servo actuator 6 in accordance with the focus error signal supplied from the arithmetic circuit 2, and moves the objective lens 25 (FIG. 2) of the optical pickup unit 1 in the optical axis direction. The focus is adjusted, the tracking servo actuator 7 is controlled in accordance with the tracking error signal supplied from the arithmetic circuit 2, and the optical pickup unit 1 is moved in the radial direction of the optical disk 41 to adjust the tracking. ing.

The control circuit 4 controls the skew correction actuator 8 (for example, the motor 71 in FIGS. 20 to 25) in accordance with the skew detection signal supplied from the arithmetic circuit 2 to correct the skew of the optical disk 41. It has been made like that.

The control circuit 4 controls the motor 9 and
The optical disk 41 is rotated at a predetermined speed.

When the control circuit 4 receives a signal corresponding to a user operation from the input device 5, the control circuit 4 controls each circuit according to the signal.

FIG. 2 shows an example of the configuration of the optical pickup unit 1 of FIG. The LD 21 emits laser light having a predetermined wavelength toward the collimator lens 22. The collimator lens 22 arranges the laser light from the LD 21 into a parallel light beam, and causes the laser light to enter a beam splitter (BS) 23.

The BS 23 allows the laser light from the collimator lens 22 to pass therethrough, and the hologram element 24 (generation means)
And reflects the laser light (reflected light from the optical disc 41) incident from the hologram element 24,
The light is incident on the PD 27 via the multi-lens 26.

The hologram element 24 and the objective lens 25 (irradiation means) constitute a bifocal lens for the zero-order light and the primary light, and the hologram element 24 has a diffraction efficiency for the zero-order light (transmitted light). A hologram is formed to increase the diffraction efficiency with respect to the primary light (first-order diffracted light).

That is, the hologram element 24 transmits the laser beam incident from the BS 23 as it is, without diffracting it, as the zero-order light as it is (first laser beam).
The remaining laser light is diffracted, emitted as primary light (second laser light), and made incident on the objective lens 25. The objective lens 25 focuses the incident first laser beam on the recording surface of the optical disc 41 via the substrate. The objective lens 25 irradiates the optical disc 41 with the incident second laser light.

Since the objective lens 25 is set so as to converge the first laser light on the recording surface of the optical disk 41, it is diffracted by the hologram element 24 and is formed at an angle different from that of the first laser light. The incident second laser light is not focused on the recording surface and forms a large spot.

The hologram element 24 transmits most of the reflected light incident from the objective lens 25 as it is, and diffracts the remaining reflected light to enter the BS 23.

FIG. 3 shows an example of the hologram element 24. The hologram element 24 in FIG. 3 is a defractive phase element having a continuous thickness. In addition, for example, a hologram element (binary element) having a quaternary level as shown in FIG. 4A or a binary level as shown in FIG. 4B can be used. As shown in FIG. 5, instead of arranging the hologram element 24,
A hologram (diffraction means) may be formed on the surface of the objective lens 25. Further, these holograms may be blazed holograms.

The hologram element 2 shown in FIGS.
In 4, the hologram is formed only on one side, but holograms may be formed on both sides.

As the hologram element 24, for example, one described in Japanese Patent Application Laid-Open No. 7-98431 can be used.

FIG. 6 shows an example of the arrangement of the light receiving section of the PD 27. The light receiving units A, B, C, and D (first light receiving units) in FIG. 6 are light receiving elements for data detection and various servos, and detect return light corresponding to the zero-order light in the hologram element 24.

On the other hand, the light receiving sections E, F, G, and H (second light receiving sections) are light receiving elements for skew detection, and detect stray light caused by primary light generated in the hologram element 24.

FIG. 7 shows an example of the light receiving section of the PD 27 and an example of the operation of the arithmetic circuit 2. The PD 27 has light receiving units A to H. The light receiving units A to D receive laser light (return light) used for reading data, detecting a focus error, and detecting a tracking error. The light receiving units A to D convert the incident light into electric signals, and output the electric signals A to D to the arithmetic circuit 2, respectively.

In this embodiment, the focus servo is performed in accordance with the astigmatism method (astigmatism method), and the arithmetic circuit 2 calculates the focus error signal (from the four signals A to D supplied from the light receiving units A to D). (A + D)-(B +
C)) is calculated and output to the control circuit 4.

The tracking servo is performed according to the push-pull method. The arithmetic circuit 2 calculates a tracking error signal (A + C− (B + D)) from the signals A to D supplied from the light receiving units A to D, 4 is output.

Note that these servo methods are not limited to the above-described methods, and other methods may be employed.

The arithmetic circuit 2 calculates a data detection signal (A + B + C + D) from the four signals A to D supplied from the light receiving units A to D, and outputs the data detection signal to the reproduction circuit 3. ing.

Further, the arithmetic circuit 2 calculates the four signals E to H supplied from the light receiving units E to H from the optical disk 41
And a skew detection signal (EF) corresponding to the skew amount of the optical disk 41 in the tangential direction of the optical disk 41, and these skew detection signals are converted to a control circuit. 4 is output.

Next, the operation of this embodiment will be described.

In this embodiment, as shown in FIG. 8A, the hologram element 24 is transmitted as the 0th-order light, condensed on the optical disk 41, reflected on the optical disk 41, and then transmitted to the 0th-order light. Return light transmitted as light (hereinafter, referred to as reproduction light) is received by the light receiving units A to D of the PD 27. Then, the data detection signal (A + B + C + D) is calculated by the arithmetic circuit 2, and the reproduction circuit 3 calculates
The data recorded on the optical disk 41 is reproduced by processing the data detection signal.

On the other hand, as shown in FIG. 8 (b), in this embodiment, the hologram element 24 is transmitted as the zero-order light and condensed on the optical disk 41, and after being reflected on the optical disk 41, Return light diffracted at 24 and emitted as primary light (hereinafter, referred to as first stray light), as shown in FIG. 8C, is diffracted at the hologram element 24 and applied to the optical disc 41 as primary light. After being reflected on the optical disk 41, the return light (hereinafter, referred to as second stray light) transmitted through the hologram element 24 as the zero-order light, and diffracted by the hologram element 24 as shown in FIG. After irradiating the optical disc 41 as primary light and reflecting off the optical disc 41,
Return light (hereinafter, referred to as third stray light) diffracted by the hologram element 24 and emitted as primary light is received by the light receiving units E to H of the PD 27, and the skew amount of the optical disk 41 is detected.

The first stray light and the second stray light incident on the PD 27 are geometrically superimposed and interfere with each other. Therefore, when no skew occurs on the optical disk 41, a spot having a pattern as shown in FIG. Generate These stray lights are received by the light receiving units E to H as shown in FIG. As described above, these stray lights are not light condensed at the image forming point of the optical disc, and therefore, the light receiving portions A to D
To form a spot wider than the spot of the reproduction light received by the camera.

On the other hand, when the optical disk 41 has a skew, the aberration increases, and the optical paths of the first stray light and the second stray light are as shown in FIGS. 11A and 11B. , The image point is shifted from the principal ray by the lateral shift amount δ. Shuring interference occurs due to the lateral shift amount δ, and a crescent-shaped interference fringe is generated in the PD 27 as shown in FIG. The lateral shift amount δ is generated corresponding to the direction of the skew, so that the interference fringe pattern corresponding to the radial skew is obtained by rotating the interference fringe pattern corresponding to the tangential skew by 90 degrees.

Therefore, when radial skew occurs, for example, as shown in FIG. 13, a difference occurs between the amount of return light incident on the light receiving portion G of the PD 27 and the amount of return light incident on the light receiving portion H. The arithmetic circuit 2 outputs the difference (GH) between the output G of the light receiving unit G of the PD 27 and the output H of the light receiving unit H to the control circuit 4 as a skew detection signal corresponding to the radial skew. When tangential skew occurs, there is a difference between the amount of return light incident on the light receiving unit E of the PD 27 and the amount of return light incident on the light receiving unit F. The difference (E−F) between the output E and the output F of the light receiving unit F is output to the control circuit 4 as a skew detection signal corresponding to tangential skew.

FIG. 14 shows an example of the correspondence between the skew amount and the skew detection signal. As shown in FIG.
When the skew amount is small (when the skew amount is about −2 degrees to about 2 degrees), the skew detection signal is almost proportional to the skew amount. (For example,
The skew is corrected by controlling the motor 71 of FIGS. 20 to 25 and adjusting the angle of the optical pickup unit 1 with respect to the optical disk 41 using a correction mechanism as shown in FIGS. In a range where the skew amount is large, the skew detection signal is not proportional to the skew amount. However, such a large skew does not usually occur, so that there is no particular problem.

As described above, the optical pickup unit 1
The skew is corrected by detecting the skew amount of the optical disk 41 using the first to third stray light generated by the hologram element 24, and operating the skew correction mechanism according to the skew amount.

The shape of the light receiving portions E to H of the PD 27 is not limited to a square, but may be an annular shape as shown in FIG.

When detecting only one direction of skew, as shown in FIG. 16, two light receiving units E and F are provided in the PD 27, and the difference (E−F) between the outputs E and F of these light receiving units is obtained.
F) is handled as a skew detection signal. In this case as well, the shapes of the light receiving portions E and F are not limited to the quadrangular shape, and may be annular as shown in FIG.

[0076]

As described above, according to the recording and reproducing apparatus according to the first aspect and the recording and reproducing method according to the eighth aspect,
A light beam is generated, and a first light beam for information recording / reproducing and a second light beam for tilt detection of the recording medium, which are generated from the light beam, are radiated to the recording medium, and the first light beam reflected from the recording medium is reflected. The first light beam is received by the first light receiving unit, the information recorded on the recording medium is reproduced, and the second light beam reflected by the recording medium is received by the second light receiving unit. Since the inclination of the recording medium is adjusted according to the signal corresponding to the inclination of the recording medium calculated from the output of the light receiving unit, the skew amount at the data reading position can be detected, and the skew correction can be accurately performed. Can be done. Further, a skew sensor having low reliability is not required due to the temperature characteristic, and therefore, the skew amount can be detected with high reliability.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an embodiment of a recording / reproducing apparatus according to the present invention.

FIG. 2 is a perspective view showing an example of an optical system of the optical pickup unit 1 of FIG.

FIG. 3 is a sectional view showing an example of the hologram element 24 of FIG.

FIG. 4 is a sectional view showing another example of the hologram element 24 of FIG.

FIG. 5 is a cross-sectional view showing an example of an objective lens 25 provided with a hologram on the surface.

6 is a diagram illustrating an example of an arrangement of a light receiving unit of the photodetector 27 in FIG.

FIG. 7 is a block diagram showing an example of the operation of each signal by the arithmetic unit 2 of FIG. 1;

8 is a diagram for explaining return light used for reproducing data in the optical system of FIG. 2 and return light corresponding to stray light generated in the hologram element 24. FIG.

FIG. 9 is a diagram illustrating an example of a spot generated by return light corresponding to stray light generated by the hologram element 24;

FIG. 10 is a diagram which is generated by being incident on a photodetector 27;
It is a figure showing an example of a spot by return light corresponding to stray light.

FIG. 11 is a cross-sectional view illustrating an example of an optical path when skew occurs.

FIG. 12 is a diagram illustrating an example of a spot generated by return light corresponding to stray light when skew occurs.

FIG. 13 is a diagram illustrating an example of a spot due to return light corresponding to stray light incident on the photodetector 27 when skew occurs.

FIG. 14 shows a skew amount of the optical disk 41 and an arithmetic circuit 2
FIG. 5 is a diagram showing an example of a correspondence relationship of a skew detection signal calculated by the following equation.

15 is a diagram illustrating another example of the arrangement of the light receiving units of the photodetector 27 in FIG.

16 is a diagram showing still another example of the arrangement of the light receiving unit of the photodetector 27 in FIG.

17 is a diagram showing still another example of the arrangement of the light receiving units of the photodetector 27 in FIG.

FIG. 18 is a cross-sectional view illustrating an example of a skew sensor.

FIG. 19 is a diagram illustrating detection of skew by a skew sensor.

FIG. 20 is a diagram illustrating an example of a correspondence relationship between a skew amount of the optical disc 41 and a skew detection signal calculated using a skew sensor.

FIG. 21 is a diagram illustrating an example of a skew correction mechanism.

FIG. 22 is a diagram illustrating another example of the skew correction mechanism.

FIG. 23 is a diagram showing still another example of the skew correction mechanism.

FIG. 24 is a diagram showing still another example of the skew correction mechanism.

FIG. 25 is a diagram showing still another example of the skew correction mechanism.

[Explanation of symbols]

Reference Signs List 1 optical pickup unit, 2 arithmetic circuit, 3 reproduction circuit, 4 control circuit, 5 input device, 6 focus servo actuator, 7 tracking servo actuator, 8 skew correction actuator, 9 motor, 21 laser diode, 2
2 collimator lens, 23 beam splitter,
24 hologram element, 25 objective lens, 26
Multi-lens, 27 photo detector

Claims (8)

[Claims] 1. A light beam is focused on a recording surface of a recording medium,
A recording / reproducing apparatus for recording or reproducing information on or from the recording medium, a generating unit for generating a light beam; a first light beam for information recording / reproducing from the light beam from the generating unit; Second for detecting the inclination of the recording medium
Generating means for generating a first light beam, a first light beam and a second light beam, irradiating the recording medium with the first light beam and the second light beam, and a first means for receiving the first light beam reflected by the recording medium. A light receiving unit having a second light receiving unit for receiving the second light beam reflected by the recording medium; and information recorded on the recording medium from an output of the first light receiving unit. Reproducing means for reproducing; calculating means for calculating a signal corresponding to the tilt of the recording medium from the output of the second light receiving portion; and calculating the tilt of the recording medium in accordance with the signal calculated by the calculating means. A recording / reproducing apparatus, comprising: an adjusting means for adjusting. 2. The second light receiving unit has at least two light receiving units, and the arithmetic unit outputs a difference between outputs of the two light receiving units as a signal corresponding to a tilt of the recording medium. The recording / reproducing apparatus according to claim 1, wherein 3. The recording medium according to claim 2, wherein the second light receiving unit has at least four light receiving units, and the calculating unit calculates a difference between outputs of two light receiving units among the four light receiving units. And outputs the difference between the outputs of the other two light receiving sections as a signal corresponding to the tangential inclination of the track on which information on the recording medium is recorded or reproduced. The recording / reproducing apparatus according to claim 1, wherein: 4. The recording / reproducing apparatus according to claim 1, wherein the second light receiving section has a quadrangular shape. 5. The recording / reproducing apparatus according to claim 1, wherein the second light receiving section has an annular shape. 6. The recording / reproducing apparatus according to claim 1, wherein said generating means is a hologram element. 7. The recording / reproducing apparatus according to claim 1, wherein the irradiation unit is an objective lens, and the generation unit is a hologram formed on a surface of the objective lens. 8. A light beam is focused on a recording surface of a recording medium,
In a recording / reproducing method for recording or reproducing information on or from the recording medium, a step of generating a light beam; a first light beam for information recording / reproducing from the light beam; Generating a second light beam, irradiating the first light beam and the second light beam to the recording medium, and applying the first light beam reflected by the recording medium to a first light beam. Receiving the second light beam reflected by the recording medium at the second light receiving section while receiving the light at the light receiving section; and reproducing the information recorded on the recording medium from the output of the first light receiving section Performing a signal corresponding to the tilt of the recording medium from the output of the second light receiving unit; and adjusting the tilt of the recording medium in accordance with the calculated signal. A recording / reproducing method characterized in that: