JP2002334464A - Light pickup with tilt detection function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the tilt of a signal face which is being recorded or reproduced. SOLUTION: A main laser beam ML generated for recording or reproducing is guided with a main optical system 27 and the signal face 12 of a light disk 1 is irradiated with the laser beam through an objective lens 25. A sub laser beam SL generated for detecting the tilt of the light disk is guided with a sub optical system 55 and condensed at defocus on the signal face 12 through the objective lens 25 while being superimposed with the main laser beam ML. A returning laser beam SL' reflected on the signal face 12 is guided with the sub optical system 55 and condensed on a tetrameric photodetector 60 for detecting the tilt of the light disk with a condensor lens 54. In the case that the optical disk 1 is tilted based on the optical axis of the objective lens 25 looking toward the radial direction, a deviation in the returning laser beam SL' occurs, a difference appears between the total receiving amount of the photodetectors A and D of the tetrameric photodetector 60 and the total receiving amount of the photodetectors B and C, thus a tilt detection signal looking toward the radial direction is made from the output of the light detection of the tetrameric photodetector 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup having a tilt detecting function, and more particularly, to condensing a laser beam for detecting the tilt of an optical disc through a recording or reproducing objective lens onto a signal surface of the optical disc while detecting the tilt of the optical disc. With a tilt detection function that guides the return laser beam reflected from the signal surface of the optical disc by the condensing lens and focuses the return laser beam on the split light detection means, and can generate an optical disc tilt detection signal from the detection output of the split light detection means Related to optical pickup.

[0002]

2. Description of the Related Art An optical disk apparatus that performs recording or reproduction on an optical disk maintains a recording or reproduction laser beam emitted from an optical pickup to the optical disk perpendicular to a signal surface of the optical disk in order to perform recording or reproduction correctly. However, it is necessary to prevent coma from occurring in the return laser beam. For this reason, the optical disc apparatus is provided with a tilt control system for detecting the tilt (tilt) of the optical disc with respect to the recording or reproducing laser beam and canceling the detected tilt of the optical disc.

A conventional general tilt control system is disclosed in
As shown in JP-A-127630, a tilt detecting section comprising one light emitting element and two light receiving elements sandwiching the light emitting element is provided on the outer surface of the optical pickup, and two light receiving elements are provided after the light beam emitted from the light emitting element is reflected by the optical disk. The elements are designed to receive light simultaneously. Then, a difference between the light receiving outputs of the two light receiving elements is calculated to generate an optical disk tilt detection signal, and a tilt actuator provided in the optical pickup is driven based on the optical disk tilt detection signal, so that the optical disk tilt detection signal reduces the tilt to zero. The entire optical pickup is tilted until indicated.

Another conventional tilt control system is disclosed in Japanese Patent Application No.
No. 000-149297, a laser beam for recording or reproduction of an optical disk is irradiated on the optical disk through an objective lens, and a reflected laser beam on the surface of the optical disk is focused on a detection surface of a four-division photodetector for tilt detection by a condenser lens. To generate an optical disc tilt detection signal in the radial direction and the tangential direction from the detection output of the quadrant photodetector for tilt detection, and drive a tilt actuator provided on the objective lens based on the optical disc tilt detection signal, The objective lens is tilted until both the optical disc tilt detection signals in the radial direction and the tangential direction indicate zero tilt.

[0005]

By the way, in recent years, D
The recording density of an optical disc such as a VD (digital versatile disc) has become extremely high, and high-precision tilt control is required to perform a recording or reproducing operation correctly. However, the former actual application 60-127
In the invention of No. 630, the position on the optical disc where recording or reproduction is performed with the laser beam emitted from the optical pickup and the position where tilt detection is performed by the tilt detection unit are greatly deviated. The optical disk has a local warp, and the inclination of the optical disk at the position where recording or reproduction is performed cannot be correctly detected. In addition, the latter Japanese Patent Application No. 2000-14929.
In the invention of No. 7, the laser beam for recording or reproduction is focused on the signal surface of the optical disk, whereas the inclination of the optical disk is detected by using the reflected beam of the laser beam reflected on the optical disk surface. Also, the optical disk signal surface and the optical disk surface are not always parallel due to manufacturing variations of the optical disk, and the tilt of the optical disk on the signal surface on which recording or reproduction is performed with a laser beam cannot be correctly detected. An object of the present invention is to provide an optical pickup with a tilt detection function that can correctly detect an inclination on a signal surface on which recording or reproduction is performed in view of the above-described problems of the related art. Further, it is an object of the present invention to provide a tilt detecting device of an optical pickup with a tilt detecting function capable of relaxing a requirement of mounting accuracy of a divided light detecting means for detecting an inclination of an optical disc.
With that purpose.

[0006]

According to the first aspect of the present invention, there is provided an optical pickup having a tilt detecting function, wherein a main laser beam generating means for generating a main laser beam for recording or reproducing data on an optical disk, and an objective lens for guiding the main laser beam. In an optical pickup including a main optical system that focuses on a signal surface of an optical disk, a sub-laser beam generating means for generating a sub-laser beam for detecting the tilt of the optical disk, and the sub-laser beam is located in front of an objective lens of the main optical system. While guiding, superimpose on the axis of the main laser beam, and guide the return sub-laser beam where the sub-laser beam is reflected on the signal surface of the optical disk. For focusing light at the center of the detection surface of the divided light detection means for It has an optical system, a sub-laser beam is characterized by, adapted to give condensed by the defocus on the optical disc signal plane. In claim 1, the wavelengths of the main laser beam and the sub laser beam may be changed.

In the optical pickup with a tilt detecting function according to a third aspect, the divided light detecting means is divided into two by one divided axis or divided into four by two orthogonal divided axes. Shields the central portion of the cross section of the return sub-laser beam reflected on the signal surface of the optical disk by the light-shielding means in a line object with respect to the beam diameter corresponding to a certain split axis on the detection surface of the split-light detection means. That is, it is characterized. In claim 3,
The light blocking means may be provided in front of the condenser lens in the sub optical system. Further, the light shielding unit is a central portion of a cross section of the return sub laser beam where the sub laser beam is reflected on the signal surface of the optical disk, and corresponds to the one of the divided axes on the detection surface of the divided light detection unit. The light may be shielded in a substantially rectangular shape along the beam diameter. Further, in the detection surface of the divided light detection means, the above-mentioned certain one is included in all or a part of the range of the main lobe caused by the return sub-laser beam.
A non-light detection area may be provided on a line object with respect to one division axis.

In the optical pickup with tilt detecting function according to claim 7, the divided light detecting means is divided into four by two orthogonal divided axes, and the sub laser beam is reflected on the signal surface of the optical disk in the middle of the sub optical system. The central portion of the cross section of the return sub-laser beam is linearly shielded against the beam diameter corresponding to one of the split axes on the detection surface of the split light detection means, and the other part on the detection surface of the split light detection means. It is characterized in that light-shielding means is provided for shielding a line object even for a beam diameter corresponding to the division axis. In claim 7, the light-shielding means may be provided in front of the condenser lens in the sub optical system. Further, the light shielding means is a central portion of the cross section of the return sub laser beam where the sub laser beam is reflected on the signal surface of the optical disk, and the cross section of the return sub laser beam where the sub laser beam is reflected on the signal surface of the optical disk. A central portion that shields the light in a substantially rectangular shape along a beam diameter corresponding to the one split axis on the detection surface of the split light detection means, and that the other split axis on the detection surface of the split light detection means. The light may be shielded in a substantially rectangular shape along the beam diameter corresponding to. Further, a non-light detection area may be provided on all or a part of the range of the main lobe generated by the return sub-laser beam in the detection surface of the divisional light detection means so as to be a line object on any of the two divisional axes. .

[0009]

Next, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of an optical pickup with a tilt detection function according to the present invention. 1 is an optical disk, 2 is a turntable on which the optical disk is mounted, and 3 is a spindle motor for rotating the turntable. The optical disc 1 has a signal surface (reflection surface) 12 formed between an upper substrate 10 and a transparent lower substrate 11. Reference numeral 20 denotes an optical pickup with a tilt detection function (hereinafter, simply referred to as “optical pickup”), which irradiates the signal surface 12 of the optical disc 1 with a 405 nm wavelength blue-violet main laser beam to record or reproduce information. Also, a sub-laser beam for detecting the tilt of the red optical disk having a wavelength of 650 nm is superimposed on the main laser beam, and
And the return sub-laser beam is focused on a four-segment photodetector for detecting the tilt of the optical disk. From the light detection output of the four-divided photodetector for detecting the tilt of the optical disk, a radial tilt detection signal and a tangential tilt detection signal of the optical disk 1 can be created.

In the optical pickup 20, a main laser light emitting diode 21 generates and emits a blue-violet main laser beam ML having a wavelength of 405 nm for recording or reproducing information and emits the laser beam in the horizontal direction. The collimator lens 23 that transmits the main laser beam ML and returns the main laser beam M
A half mirror for reflecting L ′ downward by 90 °, a rising mirror 24 for bending the main laser beam ML upward by 90 °, and an objective lens 25 for turning the main laser beam ML perpendicular to the signal surface 12 of the optical disc 1. Light is focused so that it is in focus while irradiating. Main laser beam M
L is the return main laser beam ML reflected by the signal surface 12
Is reflected 90 ° downward by the half mirror 23 through the objective lens 25 and the rising mirror 24. Reference numeral 30 denotes a divided photodetector for recording or reproducing information. An RF amplifier (not shown) provided outside can generate an RF signal, a focus error signal, and the like from the light detection output of the divided photodetector. Reference numeral 26 denotes a condensing lens for condensing the return main laser beam ML 'at the center of the split photodetector 30. A main optical system 27 is configured by the collimator lens 22, the half mirror 23, the rising mirror 24, the objective lens 25, and the condenser lens 26.
Reference numeral 40 denotes a tilt actuator attached to the objective lens 25, which can perform tilt adjustment in the radial direction and the tangential direction.

Reference numeral 50 denotes a sub-laser light emitting diode for generating and emitting a red sub-laser beam SL having a wavelength of 650 nm for tilt detection in the horizontal direction; 51, a collimator lens for collimating the sub-laser beam SL; A half mirror that reflects 90 ° upward and transmits the return sub laser beam SL ′.
Reference numeral 3 denotes a dichroic mirror in front of the rising mirror 24 of the main optical system, which superimposes the axis of the sub laser beam SL on the axis of the main laser beam ML while bending the sub laser beam SL horizontally by 90 °. 53 transmits a wavelength of 405 nm and has a wavelength of 650 nm.
Reflects nm wavelengths. After the sub-laser beam SL is bent upward by 90 ° by the rising mirror 24, it is focused on the signal surface 12 by the objective lens 25. However, since the sub laser beam SL has a longer wavelength than the main laser beam ML, the focal point is located above the signal surface 12, so that the sub laser beam SL is focused on the signal surface 12 by defocusing (see FIG. 2). . The return sub-laser beam SL ′ reflected from the signal surface 12 by the sub-laser beam SL
After passing through, the mirror 2
4 and is reflected by the dichroic mirror 53 and passes through the half mirror 52. Numeral 60 denotes a four-segment photodetector for detecting the tilt of the optical disk. The optical detection output of the four-segment photodetector is used to detect an optical disk tilt detection signal as viewed in the radial direction (left-right direction in FIG. ) Can be generated. 54 is a return sub laser beam SL '
Is a condensing lens that condenses the light at the center of the detection surface 61 of the four-divided photodetector 60.

The four-divided photodetector 60 is at a focal point (paraxial focal point) perpendicular to the optical axis of the condenser lens 54 (that is, the axis of the return sub-laser beam SL ') and for the paraxial ray of the condenser lens 54 having a wavelength of 650 nm. Are located. The vertical and horizontal sizes a × b of the detection surface 61 are collected by the condenser lens 54 when the optical disc 1 is at an inclination of zero with respect to the optical axis of the objective lens 25 in both the radial direction and the tangential direction. It is assumed that the light return sub-laser beam SL 'is formed to have a size of about twice or more the diameter r on the detection surface 61 of the return sub-laser beam SL'.
The return sub-laser beam SL 'immediately before the condenser lens 54
Is about 4.43 (mm) and r is about 0.011 (m
m), a is about 0.020 (mm), b is about 0.020
(Mm). A sub optical system 55 is constituted by the collimator lens 51, the half mirror 52, the dichroic mirror 53, and the condenser lens.

When viewed from the upper side of the optical disk 1, the four-division photodetector 60 for detecting the inclination of the optical disk has two divided axes V and W coincident with the radial direction and the tangential direction of the optical disk 1, respectively, as indicated by the symbol E in FIG. It is arranged to be. As shown in FIGS. 3A and 3B, unless the signal surface 12 at the recording or reproducing position of the optical disk 1 is inclined in either the radial direction or the tangential direction (FIG. 3A). 1 shows a case where the optical disc 1 is viewed from the plane of FIG. 1, and FIG. 3 (2) shows a case where the optical disc 1 is viewed from the direction F in FIG. 1). FIG.
As shown in (3) and (4), the four-divided photodetector 6
The light receiving amounts of the photodetectors A, B, C, and D of 0 become equal ((3) in FIG.
The light intensity distribution on the axis is shown, and FIG. 3D shows the light intensity distribution on the W axis of the quadrant photodetector 60. The point of intersection of the V axis and the W axis is defined as the origin (V, W) = (0, 0).

As shown in FIGS. 4 (1) and 4 (2), the signal surface 12 at the recording or reproducing position of the optical disk 1 is viewed radially with respect to the optical axis of the objective lens 25.
When tilted by 1.5 ° clockwise (counterclockwise) in (1), the light intensity on the detection surface 61 of the four-segment photodetector 60 as shown by the solid line (two-dot chain line) in FIG. The peak of the distribution shifts in the positive (negative) direction of the V axis, and the light receiving amounts of the photodetectors B and C (A and D) increase, and A and D (B
And C) decrease the amount of light received. The light intensity distribution on the W axis hardly changes from the case of FIG. 3 (4) (see FIG. 4 (4)).
As shown in FIGS. 5 (1) and 5 (2), the signal surface 12 at the recording or reproducing position of the optical disc 1 is clockwise (counterclockwise) in FIG. When tilted by 0.5 °, the peak of the light intensity distribution on the detection surface 61 of the four-segment photodetector 60 is shifted in the positive (negative) direction of the W axis, as shown by the solid line (two-dot chain line) in FIG. , The amount of light received by the photodetectors A and B (C and D) increases, and the amount of light received by C and D (A and B) decreases. The light intensity distribution on the V axis hardly changes from the case of FIG. 3 (3) (see FIG. 5 (3)). Further, as shown in FIGS. 6 (1) and 6 (2), the signal surface 12 at the recording / reproducing location of the optical disc 1 is clockwise in FIG. 6 (1) by 1.5 ° when viewed in the radial direction. 6 (2) in the clockwise direction in FIG. 6 (2) when viewed in the tangential direction.
As shown in (3) and (4), the four-divided photodetector 6
The peak of the light intensity distribution on the zero detection surface 61 is V-axis and W-axis.
The shift in the positive direction of the axis causes the amount of light received by the photodetector B to increase, and the amount of light received by D to decrease.

Assuming that the light detection outputs of the photodetectors A, B, C, and D are a, b, c, and d, an optical disk tilt detection signal generation unit 70 provided outside the optical pickup 20
Can be obtained as follows: (b + c)-(a + d) = optical disc tilt detection signal in radial direction (a + b)-(c + d) = optical disc tilt detection signal in tangential direction The tilt controller 80 drives the tilt actuator 40 based on the optical disk tilt detection signal and the tangential optical disk tilt detection signal so that both the radial optical disk tilt detection signal and the tangential direction optical disk tilt detection signal become zero. , The objective lens 25 is tilted. The radial optical disc tilt detection signal and the tangential optical disc tilt detection signal are the radial tilt of the signal surface 12 at the position where the main laser beam ML for recording or reproduction is irradiated, and the tilt in the tangential direction. , The main laser beam ML for recording or reproduction
Can be correctly maintained perpendicular to the signal plane 12.

By the way, even if the sub laser beam SL is focused on the signal surface 12 in a focused state, as shown in FIGS. 7A and 7B, recording or reproduction on the optical disk 1 is performed. When the signal surface 12 at the place is inclined by 1.5 ° clockwise (counterclockwise) in FIG. 7A when viewed in the radial direction with respect to the optical axis of the objective lens 25, FIG.
As shown by a solid line (two-dot chain line), the peak of the light intensity distribution on the detection surface 61 of the quadrant photodetector 60 shifts in the positive (negative) direction of the V axis. The peak of the light intensity distribution on the W axis is the origin (see FIG. 7 (4)). Similarly, FIG.
As shown in (1) and (2), the signal surface 12 at the recording or reproducing position of the optical disc 1 is clockwise (counterclockwise) in FIG.
When tilted by °, the peak of the light intensity distribution on the detection surface 61 of the four-divided photodetector 60 shifts in the positive (negative) direction of the W axis as shown by the solid line (two-dot chain line) in FIG. . The peak of the light intensity distribution on the V axis is the origin (FIG. 8).
(3)).

However, FIGS. 4 (3), (4) and FIG.
(3), (4) (or FIGS. 5 (3), (4) and FIG. 8)
Comparing (3) and (4)), when the signal surface 12 is inclined by the same angle with respect to the optical axis of the objective lens 25, the sub laser beam SL is focused on the signal surface 12 by defocusing. The amount of movement of the peak of the light intensity distribution from the center of the detection surface 61 is larger than when the light is focused in a focused state, and the tilt of the optical disc 1 can be detected with high accuracy.

According to the embodiment shown in FIG. 1, the optical disc 1 is irradiated with the sub-laser beam SL for detecting the tilt of the optical disc and the main laser beam ML for recording or reproducing information. Since the return sub-laser beam SL ′ when the beam SL is condensed on the signal surface 12 by defocusing is condensed by the condensing lens 54 at the center of the detection surface of the four-division photodetector 60 for detecting the tilt of the optical disk, it is divided into four parts. The radial optical disk tilt detection signal and the tangential direction optical disk tilt detection signal created from the photodetection output of the photodetector 60 are:
The tilt in the radial direction and the tilt in the tangential direction of the signal surface 12 at the position where the main laser beam ML for recording or reproduction is irradiated are shown. Therefore, the tilt control unit 8 detects the tilt of the optical disk in the radial direction and the tilt of the optical disk in the tangential direction.
0 drives the tilt actuator 40, and tilts the objective lens 25 so that both the radial optical disc tilt detection signal and the tangential optical disc tilt detection signal become zero, so that the main laser beam ML for recording or reproduction is used. Can be accurately maintained perpendicular to the signal surface 12 when viewed in both the radial direction and the tangential direction, and information can be recorded or reproduced with high accuracy.

When the signal surface 12 is inclined by the same angle with respect to the objective lens 25, it is better to focus the sub laser beam SL on the signal surface 12 by defocusing than by focusing on the signal surface 12. Light intensity distribution peak detection surface 61
Is large, and the inclination of the signal surface 12 can be accurately detected. At this time, the sub laser beam SL is focused on the signal surface 12 by defocusing without special measures only by setting the wavelength of the sub laser beam SL to a value different from the wavelength of the main laser beam ML. be able to.

Incidentally, the four-divided photodetector 6 in FIG.
The V axis and the W axis of 0 are arranged so as to coincide with the radial direction and the tangential direction of the optical disk 1, respectively, but as shown in FIG. It may be arranged.
In this case, the optical disc tilt detection signal creating unit 70 provided outside the optical pickup 20 detects the tilt of the optical disc 1 as follows: You only need to find the signal.

When only the tilt control in the radial direction is performed, instead of the four-segment photodetector 60, FIG.
The two-segment photodetector 60 ₁ shown in (1) is
Are arranged so as to coincide with the tangential direction of the optical disc 1, and the optical disc tilt detection signal creating section 70 calculates the radial tilt detection signal of the optical disc 1 as ba = radial optical disc tilt detection signal. Is also good. On the contrary, when only the tilt control in the tangential direction is performed, the four-segment photodetector 6 is used.
Instead of 0, a 2-split photodetector 60 ₁ shown in FIG. 10 (2) dividing axis X is arranged to coincide with the radial direction of the optical disc 1, the optical disk inclination detecting signal generating unit 70, a-b = tangential A tangential tilt detection signal of the optical disc 1 may be obtained as the directional optical disc tilt detection signal.

FIG. 11 is a block diagram of an optical pickup with a tilt detecting function according to a second embodiment of the present invention.
The same components as those described above are denoted by the same reference numerals. FIG.
Optical pickup (hereinafter, referred to as “optical pickup”) 200 with a tilt detection function is provided with a return sub-laser beam SL.
The return sub-laser beam SL 'is guided in the middle of the sub-optical system 550, in this case immediately before the condenser lens 54, and condensed on the quadrant photodetector 60 for detecting the tilt of the optical disk.
A light shielding mask 90 that shields the entire beam diameter in a substantially rectangular shape along the beam diameter corresponding to one division axis W on the detection surface 61 of the four-segment photodetector 60 at the center of the cross section of Are located. Light shielding mask 90
When looking down from directly above the optical disc 1, as indicated by reference numeral G, the light shielding area BA is formed symmetrically with respect to the beam diameter L corresponding to the division axis W.
The area other than the light shielding area BA is the transmission area TA. Optical disk 1
If the diameter of the return sub-laser beam SL 'at the position of the light-shielding mask 90 when the signal surface 12 at the position where the main laser beam ML is irradiated has no inclination in the radial direction and the tangential direction is R, light is blocked. The light shielding width h of the light shielding area BA of the mask 90 is desirably about R / 5 to R / 2. The four-divided photodetector 60 in FIG. 11 uses the optical axis of the condenser
The axis is located at a position (beam waist position) where the diameter of the return sub-laser beam SL ′ having a wavelength of 650 nm is perpendicular to (vertical axis), that is, a spherical aberration optimum focus position. Other components of the optical pickup with tilt detection function 200 are configured in the same manner as in FIG.

When the central portion of the cross section of the return sub-laser beam SL 'is shielded linearly with respect to the beam diameter L corresponding to the division axis W by the light shielding mask 90, the V-axis of the detection surface 61 of the four-divided photodetector 60 As seen above, large side lobes appear as the main lobe sharpens.
Actually, as shown in FIGS.
If the signal surface 12 at the place where recording or reproduction is performed is not inclined in either the radial direction or the tangential direction (FIG. 12 (1) shows a case where the optical disc 1 is viewed from the plane of FIG. 11). 12 (2) shows a case where the optical disc 1 is viewed from the direction F in FIG.
12B, the return sub-laser beam SL 'is not biased, and the intensity distribution on the positive side and the negative side on the V axis is of interest, as shown in FIG. The peaks of the side lobes have the same height. As shown in FIG. 12 (4), even on the W axis, the intensity distribution on the positive side and the negative side is of interest, but almost no side lobe appears (FIG. 12 (3) shows the distribution of the quadrant photodetector 60 on the V axis). FIG. 12 (4) shows the light intensity distribution on the W axis of the four-segment photodetector 60). Therefore, the total amount of light received by the photodetectors A and D is the same as the total amount of light received by B and C.

As shown in FIGS. 13 (1) and 13 (2), the signal surface 12 at the recording or reproducing position of the optical disk is viewed radially with respect to the optical axis of the objective lens 25 in FIG.
When tilted clockwise (counterclockwise) by 1.5 ° as shown by the solid line (two-dot chain line) in (1), as shown by the solid line (two-dot chain line) in FIG. Although the peak positions of the negative side lobe and the negative side lobe hardly change, the peak of the positive side lobe becomes extremely high (low) and the peak of the negative side lobe becomes extremely low (high). As shown in FIG. 13D, the light intensity distribution on the W axis hardly changes from the case of FIG. Therefore, the total amount of light received by the photodetectors A and D decreases (increases), and the total amount of light received by B and C increases (decreases).

Assuming that the photodetection outputs of the photodetectors A, B, C and D are a, b, c and d, the optical pickup 200
Optical disk tilt detection signal generator 70 provided outside
0, the tilt detection signal of the optical disc 1 can be obtained as (b + c)-(a + d) = optical disc tilt detection signal in the radial direction, and the tilt control unit 800 controls the tilt actuator 40 based on the radial optical disc tilt detection signal. Then, the objective lens 25 is tilted so that the optical disk tilt detection signal in the radial direction becomes zero.

According to the embodiment shown in FIG. 11, the optical disc 1 is irradiated with the sub-laser beam SL for detecting the tilt of the optical disc and the main laser beam ML for recording or reproducing information. The return sub-laser beam SL ′ when the SL is focused on the signal surface 12 by defocusing is focused by the focusing lens 54 at the center of the detection surface of the four-divided photodetector 60 for detecting the tilt of the optical disk. 90, one division axis W on the detection surface 61 of the four-division photodetector 60 at the center of the cross section of the return sub-laser beam SL '.
Along the beam diameter (see L in FIG. 11), the entire beam diameter is shielded in a substantially rectangular shape so as to be linear with respect to the beam diameter. , V of 4-split photodetector 60
On the positive side and the negative side of the axis, peaks of side lobes generated at positions away from the center of the detection surface change differentially. Therefore, the radial optical disc tilt detection signal created from the light detection output of the four-segment photodetector 60 indicates the radial tilt of the signal surface 12 at the position where the recording or reproducing main laser beam ML is irradiated. The tilt control unit 800 drives the tilt actuator 40 based on the radial direction optical disc tilt detection signal, and tilts the objective lens 25 so that the radial direction optical disc tilt detection signal becomes zero, so that the main laser for recording or reproduction is used. The beam ML can be correctly maintained perpendicular to the signal surface 12 when viewed in the radial direction, and information can be recorded or reproduced with high accuracy.

The main lobe formed on the detection surface 61 of the four-divided photodetector 60 has a small diameter, and the peak position hardly moves even by the radial inclination angle of the optical disc 1 with respect to the optical axis of the objective lens 25 ( FIG. 13 (3)). On the other hand, depending on the radial tilt angle of the optical disc 1, side lobes whose peaks change differentially on the positive and negative sides of the V axis of the four-divided photodetector 60 are generated at positions distant from the center of the detection surface. Because (the first
In the second embodiment, the peak position of the light intensity distribution on the detection surface 61 when the optical disc 1 is tilted clockwise by 1.5 ° when viewed in the radial direction is the optical disc 1 in the second embodiment. Is far closer to the center of the detection surface 61 than the peak position of the side lobe on the detection surface 61 when is tilted clockwise by 1.5 ° when viewed in the radial direction. FIG. 4 (3) and FIG.
(Comparison with (3)) Even if the center of the detection surface 61 of the four-division photodetector 60 and the optical axis of the condenser lens 54 are slightly displaced, it is possible to accurately detect the tilt of the optical disk in the radial direction. Therefore, the requirement for the mounting accuracy of the four-segment photodetector 60 can be relaxed.

Although the V-axis and W-axis of the four-segment photodetector 60 in FIG. 11 are arranged so as to correspond to the radial direction and the tangential direction of the optical disk 1, respectively.
As shown in FIG. 9, the photodetector 60 may be arranged so as to be rotated by 45 degrees in the detection plane of the photodetector 60. In this case, the light-shielding mask 90 is located at the center of the cross section of the return sub-laser beam SL ′, and has one divided axis W and 4 on the detection surface 61 of the four-divided photodetector 60.
Along the beam diameter (see L in FIG. 11) corresponding to the axis W ′ forming 5 °, the entire beam diameter is arranged to be shielded from light in a rectangular shape. The optical disc tilt detection signal generation unit 700 provided outside the optical pickup 200 may obtain the radial tilt detection signal of the optical disc 1 as b−d = radial optical disc tilt detection signal.

Further, instead of the 4-split photodetector 60, arranged as split axis X of the two-division photodetector 60 ₁ as shown in FIG. 10 (1) matches the tangential direction of the optical disc 1, create an optical disk tilt detecting signal The unit 700 may determine a radial tilt detection signal of the optical disc 1 as ba = radial optical disc tilt detection signal.

Further, the quadrant photodetector 6 shown in FIG.
When 0 is used in the same arrangement, FIG.
As shown in (2), the central part on the detection surface 61 is the main part.
All or part of the lobe range (see Fig. 12 (3))
In addition, the non-light receiving area that is line-symmetric to the W axis
Area IA or IB may be provided,
Rotate the split photo detector 60 by 45 ° as shown in FIG.
In the case of arrangement, as shown in FIG. 14 (3) or (4),
The entire area of the main lobe at the center on the detection surface 61
Or, in part, a line pair with respect to the W ′ axis such as a circle or square
To provide an imaginary non-light receiving area IC or ID,
As shown in FIG. 10A, a two-part photodetector 60 is used.₁
Is divided in the tangential direction of the optical disc 1
15 (1) or (2)
As shown in FIG.₁Main row in the middle part above
12 (3) and 13 (3).
Or partly symmetric about the X axis, such as a circle or square
The non-light receiving area IE or IF may be provided.
14 and 15, the optical disc in the radial direction
The tilt detection signal is hardly affected by the main lobe.
Therefore, a four-divided photo
Tector 60 or two-segment photodetector 60 ₁Mounting
The requirements for the accuracy of the application can be further reduced.

The light-shielding area BA of the light-shielding mask 90 shields the entire beam diameter from light in a rectangular shape.
6 (1) as shown by reference numeral 90 _1, or so as to shield the beam diameter entire length partially elliptical shape, FIG. 16 (2) -
(4) as shown by reference numeral 90 _2, 90 _3, 90 _4, it may be to shield the part of the central side of the beam diameter to a rectangular shape or an elliptical shape or a circular shape.

FIG. 17 is a block diagram of an optical pickup with a tilt detecting function according to a third embodiment of the present invention.
The same components as those in 1 are denoted by the same reference numerals. FIG.
The optical pickup 201 having a tilt detection function (hereinafter, referred to as an “optical pickup”) 201 has a return sub-laser beam S
The return sub-laser beam SL is guided in the middle of the sub-optical system 551 for guiding L ′ to the four-divided photodetector 60 for detecting the tilt of the optical disk, here immediately before the condenser lens 54.
A light-shielding mask 91 that shields the entire beam diameter in a substantially rectangular shape along the beam diameter corresponding to one division axis V on the detection surface 61 of the four-segment photodetector 60 at the central portion of the cross section of '. Is arranged. Light shielding mask 9
1, when viewed from directly above the optical disc 1, as indicated by reference numeral H, a rectangular light-blocking area BA is formed symmetrically with respect to the beam diameter M corresponding to the division axis V. When the diameter of the return sub-laser beam SL ′ at the position of the light-shielding mask 91 when the signal surface 12 at the position where the main laser beam ML of the optical disc 1 is irradiated has no inclination in the radial direction and the tangential direction is R, , Light shielding mask 91
The light shielding width k of the light shielding area BA is desirably about R / 5 to R / 2. Other components of the optical pickup 201 with the tilt detection function are configured in the same manner as in FIG.

When the central portion of the cross section of the return sub-laser beam SL 'is light-shielded by the light-shielding mask 91 in a line-symmetric manner with respect to the beam diameter M corresponding to the division axis V, the W-axis of the detection surface 61 of the four-divided photodetector 60 As seen above, large side lobes appear as the main lobe sharpens.
Actually, as shown in FIGS.
If the signal surface 12 at the place where recording or reproduction is performed is not inclined in both the radial direction and the tangential direction (FIG. 18A shows the case where the optical disc 1 is viewed from the paper surface of FIG. 17). FIG. 18 (2) shows F in FIG.
This shows the case where the optical disc 1 is viewed from the direction), the return sub-laser beam SL ′ is not biased in front of the light shielding mask 91, and the positive and negative intensities on the W axis as shown in FIG. The distribution is of interest and the sidelobe peaks are at the same height. As shown in FIG. 18 (3), the intensity distribution on the positive side and the negative side is also targeted on the V-axis, but almost no side lobe appears (FIG. 18 (3) shows the case where the four-divided photodetector 60 is on the V-axis). FIG. 18D shows the light intensity distribution.
5 shows the light intensity distribution of the split photodetector 60 on the W axis. Therefore, the total amount of light received by the photodetectors A and B is the same as the total amount of light received by C and D.

As shown in FIGS. 19A and 19B, the signal surface 12 at the recording or reproducing position of the optical disk is viewed in the tangential direction with respect to the optical axis of the objective lens 25. As shown by the solid line (two-dot chain line) in FIG. 19 (4), as shown by the solid line (two-dot chain line) in FIG. Although the peak position of the side lobe is almost the same, the peak of the positive side lobe becomes extremely high (low) and the peak of the negative side lobe becomes extremely low (high).
The light intensity distribution on the V axis as shown in FIG.
It hardly changes from the case of. Therefore, photodetector A
And B, the total received light amount increases (decreases), and the total received light amount of C and D decreases (increases).

Assuming that the light detection outputs of the photodetectors A, B, C and D are a, b, c and d, the optical pickup 201
Optical disk tilt detection signal generator 70 provided outside
1, the tilt detection signal of the optical disc 1 can be obtained as (a + b)-(c + d) = optical disc tilt detection signal in the tangential direction, and the tilt control unit 801 controls the tilt actuator based on the optical disc tilt detection signal in the tangential direction. By driving the objective lens 25, the objective lens 25 is tilted so that the optical disc tilt detection signal in the tangential direction becomes zero.

According to the embodiment shown in FIG. 17, the optical disc 1 is irradiated with the sub laser beam SL for detecting the tilt of the optical disc and the main laser beam ML for recording or reproducing information. The return sub-laser beam SL ′ when the SL is focused on the signal surface 12 by defocusing is focused by the focusing lens 54 at the center of the detection surface of the four-divided photodetector 60 for detecting the tilt of the optical disk. Due to 91, one division axis V on the detection surface 61 of the four-division photodetector 60 is the central part of the cross section of the return sub-laser beam SL '.
Along the beam diameter (see M in FIG. 17), the entire beam diameter is shielded in a substantially rectangular shape with respect to the beam diameter, so that the signal surface 12 of the optical disc 1 with respect to the optical axis of the objective lens 25 is In accordance with the inclination angle in the tangential direction, peaks of side lobes generated at positions away from the center of the detection surface are differentially changed on the positive side and the negative side of the W axis of the four-divided photodetector 60. Therefore, the optical disc tilt detection signal in the tangential direction created from the light detection output of the four-split photodetector 60 is the signal of the optical disc in the tangential direction on the signal surface 12 at the position where the main laser beam ML for recording or reproduction is irradiated. Shows the slope. Therefore, the tilt control unit 801 drives the tilt actuator 40 based on the tangential direction optical disk tilt detection signal, and tilts the objective lens 25 so that the radial direction optical disk tilt detection signal becomes zero, thereby enabling recording or reproduction. Main laser beam M
When viewed in the tangential direction, L can be correctly maintained perpendicular to the signal surface 12, and information can be recorded or reproduced with high accuracy. Also, a four-segment photodetector 6
The main lobe generated on the 0 detection surface 61 has a small diameter, and the peak position hardly moves even by the inclination angle of the optical disc 1 in the tangential direction with respect to the optical axis of the objective lens 25 (see FIG. 19 (4)). . On the other hand, depending on the inclination angle of the optical disc 1 in the tangential direction, side lobes whose peaks change differentially on the positive and negative sides of the W axis of the four-divided photodetector 60 are generated at positions distant from the center of the detection surface. Therefore, even if the center of the detection surface of the four-division photodetector 60 and the optical axis of the condenser lens 54 are slightly displaced, the inclination of the optical disk in the tangential direction can be accurately detected. Therefore, the requirement for the mounting accuracy of the four-segment photodetector 60 can be relaxed.

The V-axis and W-axis of the four-segment photodetector 60 in FIG. 17 are arranged so as to correspond to the radial direction and the tangential direction of the optical disk 1, respectively.
As shown in FIG. 9, the photodetector 60 may be arranged so as to be rotated by 45 degrees in the detection plane of the photodetector 60. In this case, the light-shielding mask 91 is located at the center of the cross section of the return sub-laser beam SL ′ and has one divided axis V and 4 on the detection surface 61 of the four-divided photodetector 60.
Along the beam diameter (see M in FIG. 17) corresponding to the axis V ′ forming 5 °, the entire beam diameter is arranged to be shielded in a substantially rectangular shape. Optical disc tilt detection signal generator 701 provided outside optical pickup 201
In this case, the inclination detection signal of the optical disk 1 in the tangential direction may be obtained as ac = the optical disk inclination detection signal in the tangential direction.

In place of the four-segment photodetector 60, a two-segment photodetector 60 shown in FIG.
₁ is arranged so that the division axis X coincides with the radial direction of the optical disc 1,
Alternatively, the tangential direction tilt detection signal of the optical disk 1 may be obtained as ab = tangential direction optical disk tilt detection signal.

Further, the four-divided photodetector 6 shown in FIG.
In the case where 0 is used as it is, as shown in FIG. 14 (1) or (2), the central part on the detection surface 61 is entirely or partially in the range of the main lobe (see FIG. 18 (4)). When a non-light receiving area IA or IB which is linearly symmetric with respect to a V axis such as a circle or a square is provided, or when the four-divided photodetector 60 in FIG. 17 is rotated by 45 degrees as shown in FIG. Or as shown in (4),
A non-light receiving area IC or ID that is linear or symmetrical with respect to the W ′ axis, such as a circle or a square, is provided on the whole or a part of the range of the main lobe in the central portion on the detection surface 61,
As shown in FIG. 10 (2), the two-divided photodetector 60 ₁
If the division axis X is arranged to coincide with the radial direction of the optical disc 1, as shown in FIG. 20 (1) or (2), all of the range of the main lobe in the central part on the detection surface 61 ₁ or a The portion may be provided with a non-light receiving area IG or IH that is symmetrical to the X axis, such as a circle or a square. If Figure 14, as shown in FIG. 20, the optical disk tilt detecting signal in the tangential direction since hardly affected by the main lobe, the 4-split photodetector 60, or 2-division photodetector 60 ₁ of the mounting accuracy for inclination detection of the optical disk 1 Requirements can be further relaxed.

The light-shielding area BA of the light-shielding mask 91 shields the entire beam diameter in a rectangular shape.
1 (1) as shown by reference numeral 91 _1, or so as to shield the beam diameter entire length partially elliptical shape, FIG. 21 (2) -
(4) as shown by reference numeral 91 _2, 91 _3, 91 _4, it may be to shield the part of the central side of the beam diameter to a rectangular shape or an elliptical shape, or a circular or the like.

FIG. 22 is a block diagram of an optical pickup with a tilt detection function according to a fourth embodiment of the present invention.
The same components as those described above are denoted by the same reference numerals. FIG.
The optical pickup 202 with a tilt detection function (hereinafter, referred to as “optical pickup”) has a return sub-laser beam SL.
The return sub-laser beam SL ′ is guided in the middle of the sub-optical system 552, in this case immediately before the condensing lens 54, where it is guided to the four-divided photodetector 60 for detecting the tilt of the optical disk.
Is a central portion of a cross section of the photodetector 60, and the entire beam diameter is shielded in a rectangular shape along the beam diameter corresponding to one division axis W on the detection surface 61 of the four division photodetector 60;
In addition, a light-shielding mask 92 that shields the entire beam diameter in a substantially rectangular shape along the beam diameter corresponding to another one of the divided axes V on the detection surface 61 of the four-divided photodetector 60 is arranged. When the light-shielding mask 92 is viewed from directly above the optical disc 1, a rectangular light-shielding area BA is formed symmetrically with respect to the beam diameter L corresponding to the division axis W, as indicated by reference numeral I. The beam diameter M corresponding to V is also formed linearly. Optical disk 1
If the diameter of the return sub-laser beam SL ′ at the position of the light-shielding mask 92 when the signal surface 12 at the position where the main laser beam ML is irradiated has no inclination in the radial direction and the tangential direction is R, light is blocked. The light shielding width j of the mask 92 is desirably about R / 5 to R / 2. Other components of the optical pickup 202 with the tilt detection function are configured in the same manner as in FIG.

When the central portion of the cross section of the return sub-laser beam SL 'is shielded linearly with respect to the beam diameter L corresponding to the division axis W by the light shielding mask 92, the V axis of the detection surface 61 of the four-division photodetector 60 As seen above, large side lobes appear as the main lobe sharpens.
When the central portion of the cross section of the return sub-laser beam SL ′ is shielded by the light-shielding mask 92 in a line symmetrical manner with respect to the beam diameter M corresponding to the division axis V, the four-divided photodetector 6
When viewed on the W axis of the zero detection surface 61, the main lobe sharpens and a large side lobe appears at the same time.

Actually, as shown in FIGS. 23A and 23B,
If the signal surface 12 at the place where recording or reproduction is performed on the optical disk 1 is not inclined in both the radial direction and the tangential direction (FIG. 23 (1) shows the optical disk 1 viewed from the paper surface of FIG. 22). FIG. 23 (2)
22 shows the case where the optical disc 1 is viewed from the F direction in FIG. 22), the return sub-laser beam SL ′ is not biased on the front side of the light shielding mask 92, and the positive side on the V axis as shown in FIG. And the intensity distribution on the negative side are the targets, and the peaks of the side lobes have the same height. As shown in FIG. 23 (4), the intensity distribution on the positive side and the negative side is also an object on the W axis, and the peak of the side lobe has the same height (FIG. 23).
(3) shows the light intensity distribution on the V axis of the four-segmented photodetector 60, and FIG. 23 (4) shows the light intensity distribution on the W-axis of the four-segmented photodetector 60). Therefore, the photodetectors A, B, C, and D all receive the same amount of light.

As shown in FIGS. 24 (1) and (2), the signal surface 12 at the recording or reproducing position of the optical disk is viewed in the radial direction with respect to the optical axis of the objective lens 25.
When inclined by 1.5 ° clockwise (counterclockwise) as shown by the solid line (two-dot chain line) in (1), as shown by the solid line (two-dot chain line) in FIG. Although the peak position of the negative side lobe is almost the same as that of FIG. 23,
The peak of the side lobe on the positive side is extremely high (low)
The peak of the negative side lobe becomes extremely low (high). As shown in FIG. 24D, the light intensity distribution on the W axis hardly changes from the case of FIG. Therefore, the total amount of light received by the photodetectors A and D decreases (increases), and B
And C increase (decrease) the total amount of received light.

As shown in FIGS. 25 (1) and 25 (2), the signal surface 12 at the recording or reproducing position of the optical disk is viewed in the tangential direction with respect to the optical axis of the objective lens 25. 23, the light intensity distribution on the V axis hardly changes from that in FIG. 23 as shown in FIG. 25 (3) when it is inclined clockwise (counterclockwise) by 1.5 ° as shown by the solid line (two-dot chain line). . On the other hand, as shown by the solid line (two-dot chain line) in FIG. 25D, the peak positions of the positive side lobe and the negative side lobe on the W axis are almost the same as those in FIG. The peak of the negative side lobe becomes extremely low (high). Therefore, the total amount of received light of the photodetectors A and B increases (decreases), and the total amount of received light of C and D decreases (increases).

Assuming that the light detection outputs of the photodetectors A, B, C, and D are a, b, c, and d, the optical pickup 202
Optical disk tilt detection signal generator 70 provided outside
2 is: (b + c)-(a + d) = optical disc tilt detection signal in the radial direction (a + b)-(c + d) = optical disc tilt detection signal in the tangential direction The tilt detection signal of the optical disc 1 can be obtained. The tilt control unit 802 drives the tilt actuator 40 based on the optical disk tilt detection signal and the tangential direction optical disk tilt detection signal so that both the radial direction optical disk tilt detection signal and the tangential direction optical disk tilt detection signal become zero. Then, the objective lens 25 is tilted. The radial optical disc tilt detection signal and the tangential optical disc tilt detection signal are the radial tilt of the signal surface 12 at the position where the main laser beam ML for recording or reproduction is irradiated, and the tilt in the tangential direction. , The main laser beam ML for recording or reproduction
Can be correctly maintained perpendicular to the signal surface 12 in both the radial direction and the tangential direction.

According to the embodiment shown in FIG. 22, the optical disk 1 is irradiated with the sub-laser beam SL for detecting the tilt of the optical disk and the main laser beam ML for recording or reproducing information. The return sub-laser beam SL ′ when the SL is focused on the signal surface 12 by defocusing is focused by the focusing lens 54 at the center of the detection surface of the four-divided photodetector 60 for detecting the tilt of the optical disk. 92, one division axis W on the detection surface 61 of the four-division photodetector 60 at the center of the cross section of the return sub-laser beam SL '
Along the beam diameter corresponding to the beam diameter, the entire beam diameter is shielded in a substantially rectangular shape in a line object with respect to the beam diameter, and also along the beam diameter corresponding to the other split axis V, In contrast to this, since the entire beam diameter is shielded in a substantially rectangular shape with respect to the line object, the center of the detection surface 61 is located on the positive side and the negative side of the V axis of the four-divided photodetector 60 in accordance with the radial tilt angle of the optical disc 1. The peak of the side lobe generated at a distant position changes differentially, and the optical disk 1
The peak of the side lobe generated at a position away from the center of the detection surface 61 changes differentially on the positive side and the negative side of the W axis of the four-divided photodetector 60 in accordance with the inclination angle in the tangential direction. . Accordingly, the radial direction optical disk tilt detection signal and the tangential direction optical disk tilt detection signal created from the light detection output of the four-divided photodetector 60 indicate the signal surface at the position where the main laser beam ML for recording or reproduction is irradiated. 12 shows the tilt of the optical disc 1 in the radial direction and the tilt of the optical disc 1 in the tangential direction. Therefore, the tilt control unit 802 drives the tilt actuator 40 based on the radial direction optical disk tilt detection signal and the tangential direction optical disk tilt detection signal, and the radial direction optical disk tilt detection signal and the tangential direction optical disk tilt detection signal are output. By inclining the objective lens 25 so that both become zero, the main laser beam ML for recording or reproduction can be correctly maintained perpendicular to the signal surface 12 when viewed in the radial direction and the tangential direction, and the recording or reproduction of information can be performed. Can be performed with high accuracy.

The main lobe formed on the detection surface 61 of the four-divided photodetector 60 has a small diameter, and its peak position is also determined by the inclination angles of the optical disk 1 with respect to the optical axis of the objective lens 25 in the radial and tangential directions. It hardly moves (see FIGS. 23 (3) and (4)). On the other hand, according to the tilt angle of the optical disc 1 in the radial direction, 4
Side lobes whose peaks change differentially on the positive side and the negative side of the V axis of the split photodetector 60 are generated at positions distant from the center of the detection surface 61, and at the inclination angle of the optical disc 1 in the tangential direction. Accordingly, a side lobe whose peak changes differentially on the positive side and the negative side of the W axis of the four-divided photodetector 60 is generated at a position away from the center of the detection surface 61. Even if there is a slight deviation between the center of 61 and the optical axis of the condenser lens 54, it is possible to accurately detect the tilt of the optical disk in the radial direction and the tilt of the optical disk in the tangential direction.
Therefore, the requirement for the mounting accuracy of the four-segment photodetector 60 can be relaxed.

The V-axis and W-axis of the four-segment photodetector 60 in FIG. 22 are arranged so that they respectively coincide with the radial direction and the tangential direction of the optical disk 1.
As shown in FIG. 9, the photodetector 60 may be arranged so as to be rotated by 45 degrees in the detection plane of the photodetector 60. In this case, the light-shielding mask 92 is located at the center of the cross section of the return sub-laser beam SL ′, and has one divided axis W and 4 on the detection surface 61 of the four-divided photodetector 60.
Along the beam diameter (see L in FIG. 22) corresponding to the axis W ′ forming 5 °, the entire beam diameter is shielded in a substantially rectangular shape, and the axis V ′ forming 45 ° with the other divided axis V. Along the beam diameter (see M in FIG. 22) corresponding to the above, the entire beam diameter is arranged to be shielded in a substantially rectangular shape. The optical disc tilt detection signal creation unit 702 provided outside the optical pickup 202 detects the radial tilt of the optical disc 1 as follows: bd = optical disc tilt detection signal in the radial direction, ac = optical disc tilt detection signal in the tangential direction. The signal and the inclination detection signal in the tangential direction may be obtained.

The quadrant photodetector 6 shown in FIG.
In the case where 0 is used as it is, as shown in FIG. 14 (1) or (2), the entire area of the main lobe (see FIGS. 23 (3) and (4)) at the center on the detection surface 61 or Partially, a non-light receiving area IA or IB which is linear in both the V axis and the W axis such as a circle or a square is provided, or the quadrant photodetector 60 in FIG. 22 is rotated by 45 ° as shown in FIG. In the case of disposing, as shown in FIG. 14 (3) or (4), the whole or a part of the range of the main lobe at the central portion on the detection surface 61 has the W ′ axis and the V ′ axis such as a circle or a rectangle. Non-light receiving area I which is a line object in any case
C or ID may be provided. In the case shown in FIG. 14, since neither the radial optical disk tilt detection signal nor the tangential optical disk tilt detection signal is substantially affected by the main lobe, the mounting accuracy of the four-division photodetector 60 for detecting the tilt of the optical disk 1 is improved. Requirements can be further relaxed.

The light-shielding area BA of the light-shielding mask 92 shields the entire beam diameter from light in a rectangular shape.
6 (1) as shown by reference numeral 92 _1, or so as to shield the beam diameter entire length partially elliptical shape, FIG. 26 (2) -
(4) as shown by reference numeral 92 _2, 92 _3, 92 _4, it may be to shield a portion of the inboard of the beam diameter to a rectangular shape or an elliptical shape, or a circular or the like.

In the second to fourth embodiments and their modifications, the light shielding mask is arranged immediately before the condenser lens in the sub optical system. It may be arranged at an arbitrary position between the optical lenses, or may be arranged between the condenser lens and the divided photodetector for detecting the tilt of the optical disk, such as immediately after the condenser lens.

[0053]

According to the present invention, the sub-laser beam for detecting the tilt of the optical disk is focused on the signal surface by defocusing, so that the divided light detecting means for detecting the tilt of the optical disk can be used on the detection surface. The movement amount of the peak of the light intensity distribution increases, and the tilt of the optical disk can be detected with high accuracy.

According to another aspect of the present invention, the center portion of the cross section of the return sub-laser beam is provided in the middle of the sub-optical system for guiding the return sub-laser beam to the divided light detecting means for detecting the tilt of the optical disk. Since the light beam is shielded linearly with respect to the beam diameter corresponding to the division axis of the divided light detection means or the axis shifted by 45 ° from the division axis, on the detection surface of the divided light detection means,
Side lobes whose peaks change differentially according to the tilt of the optical disk are generated at positions away from the center of the detection surface of the divided light detection means. Therefore, even if the center of the detection surface of the divided light detecting means and the optical axis of the sub optical system are slightly displaced, it is possible to accurately detect the inclination of the optical disk, and to mount the divided light detecting means for detecting the inclination of the optical disk. Accuracy requirements can be relaxed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical pickup with a tilt detection function according to a first embodiment of the present invention.

FIG. 2 is an enlarged view near an objective lens in FIG.

FIG. 3 is an explanatory diagram of a light intensity distribution on a four-segment photodetector by a return sub-laser beam when the optical disc in FIG. 1 has no inclination.

4 is an explanatory diagram of a light intensity distribution on a four-segment photodetector by a return sub-laser beam when the optical disk in FIG. 1 is tilted in a radial direction.

5 is an explanatory diagram of a light intensity distribution on a four-segment photodetector by a return sub-laser beam when the optical disk in FIG. 1 is tilted in a tangential direction.

FIG. 6 is an explanatory diagram of a light intensity distribution on a four-segment photodetector by a return sub-laser beam when the optical disc in FIG. 1 has a tilt in a radial direction and a tilt in a tangential direction.

FIG. 7 is an explanatory diagram of a light intensity distribution on a four-divided photodetector by a return sub-laser beam when the optical disk is tilted in a radial direction when the sub-laser beam is focused on a signal surface.

FIG. 8 is an explanatory diagram of a light intensity distribution on a four-divided photodetector by a return sub-laser beam when the optical disk is tilted in a tangential direction when the sub-laser beam is focused on a signal surface.

FIG. 9 is an explanatory diagram showing an example in which the arrangement of the four-segment photodetector for detecting the tilt of the optical disk in FIG. 1 is changed.

10 is an explanatory diagram of a two-segment photodetector used in place of the four-segment photodetector for detecting the tilt of the optical disc in FIG.

FIG. 11 is a configuration diagram of an optical pickup with a tilt detection function according to a second embodiment of the present invention.

12 is an explanatory diagram of a light intensity distribution on a four-divided photodetector by a return sub-laser beam when the optical disk in FIG. 11 has no inclination.

FIG. 13 is a diagram showing a fourth example of the return sub-laser beam when the optical disc in FIG. 11 is inclined in the radial direction.
FIG. 4 is an explanatory diagram of a light intensity distribution on a split photodetector.

FIG. 14 is an explanatory diagram showing a modification of the four-segment photodetector for detecting the tilt of the optical disk in FIG. 11;

FIG. 15 is an explanatory diagram showing a modification of the two-segment photodetector for detecting the tilt of the optical disk.

FIG. 16 is an explanatory diagram showing a modified example of the light shielding mask in FIG. 11;

FIG. 17 is a configuration diagram of an optical pickup with a tilt detection function according to a third embodiment of the present invention.

18 is an explanatory diagram of a light intensity distribution on a four-divided photodetector by a return sub-laser beam when the optical disc in FIG. 17 has no inclination.

19 is an explanatory diagram of a light intensity distribution on a four-divided photodetector by a return sub-laser beam when the optical disk in FIG. 17 is inclined in the tangential direction.

FIG. 20 is an explanatory view showing a modified example of the two-segment photodetector for detecting the tilt of the optical disk.

FIG. 21 is an explanatory diagram showing a modification of the light shielding mask in FIG. 17;

FIG. 22 is a configuration diagram of an optical pickup with a tilt detection function according to a fourth embodiment of the present invention.

23 is an explanatory diagram of a light intensity distribution on a four-segment photodetector by a return sub-laser beam when the optical disc in FIG. 22 has no inclination.

FIG. 24 is a diagram illustrating a fourth example of the return sub-laser beam when the optical disc in FIG. 22 is inclined in the radial direction;
FIG. 4 is an explanatory diagram of a light intensity distribution on a split photodetector.

25 is an explanatory diagram of a light intensity distribution on a four-segment photodetector by a return sub-laser beam when the optical disk in FIG. 22 is inclined in the tangential direction.

FIG. 26 is an explanatory view showing a modification of the light shielding mask in FIG. 22;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical disk 12 Signal surface 20, 200, 201, 202 Optical pickup with tilt detection function 21 Main laser light emitting diode 25 Objective lens 27 Main optical system 40 Tilt actuator 50 Sub laser light emitting diode 54 Condensing lens 55 Sub optical system 60 Quadrant photodetector 60 ₁ 2-division photodetector 61, 61 _first detecting surface 70,700,701,702 optical disk tilt detecting signal generator 80,800,801,802 tilt controller 90, 90 ₁ to 90 _4, 91, 91 ₁ to 91 _4, 92 ,
92 _{1 to} 92 ₄ Light-shielding mask ML Main laser beam SL Sub-laser beam SL ′ Return sub-laser beam BA Light-shielding area IA to IH Non-light-receiving area

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunari Abe 1-14-6 Dogenzaka, Shibuya-ku, Tokyo Co., Ltd. Inside Kenwood Corporation (72) Takaki Hiraga 1-16-16 Dogenzaka, Shibuya-ku, Tokyo Co., Ltd. Inside Kenwood (72) Inventor Hiroshi Miyazawa 1-14-6 Dogenzaka, Shibuya-ku, Tokyo Inside Kenwood Co., Ltd. (72) Haruki Tokumaru 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Japan Broadcasting Corporation Research Institute (72) Inventor Naoki Shimizu 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Japan Broadcasting Corporation Research Institute (72) Inventor Hitoshi Yanagisawa 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Inside the laboratory (72) Inventor Daiichi Koide 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Research Institute F-term (reference) 5D1 18 AA16 BA01 CA05 CD04 CF03 CF06 CG03 CG07 CG15 CG26 DA40 5D119 BA01 EC40 EC47 FA08 KA17 KA24 KA26

Claims (10)

[Claims] 1. An optical pickup including a main laser beam generating means for generating a main laser beam for recording or reproduction of an optical disc and a main optical system for focusing a signal surface of the optical disc with an objective lens while guiding the main laser beam. A sub-laser beam generating means for generating a sub-laser beam for detecting the tilt of the optical disc; and superimposing the sub-laser beam on the axis of the main laser beam while guiding the sub-laser beam to the front side of the objective lens of the main optical system. A sub-optical system that guides the return sub-laser beam reflected on the signal surface of the optical disk and condenses it at the center of the detection surface of the divided light detection means for detecting the tilt of the optical disk arranged perpendicularly to the axis of the return sub-laser beam by the condenser lens And the sub-laser beam is defaulted on the optical disc signal surface. It has to be condensed in Kas, tilt detection function with optical pickup according to claim. 2. The optical pickup with a tilt detection function according to claim 1, wherein the wavelengths of the main laser beam and the sub laser beam are changed. 3. A split light detecting means is provided by two split axes.
The center of the cross section of the return sub-laser beam where the sub-laser beam is reflected on the signal surface of the optical disk is located in the middle of the sub-optical system. The optical pickup with a tilt detection function according to claim 1, wherein a light beam is shielded by a light-shielding means with respect to a beam diameter corresponding to one of the upper divided axes. 4. The optical pickup with a tilt detection function according to claim 3, wherein the light blocking means is provided in front of the condenser lens in the sub optical system. 5. The light-blocking means is a central portion of a transverse section of the return sub-laser beam where the sub-laser beam is reflected on the signal surface of the optical disk, and the one of the divided axes on the detection surface of the divided light detection means. The optical pickup with a tilt detection function according to claim 3 or 4, wherein light is shielded in a substantially rectangular shape along a beam diameter corresponding to (c). 6. A non-light detection area is provided on a whole or a part of a range of a main lobe generated by a return sub-laser beam in a detection surface of the divisional light detection means so as to be linear with respect to the one divisional axis. The optical pickup with a tilt detection function according to claim 3, 4, or 5. 7. A split light detecting means is divided into four by two orthogonal split axes, and a middle portion of a cross section of a return sub laser beam in which a sub laser beam is reflected on a signal surface of an optical disk is provided in the middle of a sub optical system. , And shields the beam diameter corresponding to one of the split axes on the detection surface of the split light detection means from linear objects, and also applies the beam diameter to the other split axis on the detection surface of the split light detection means. 3. An optical pickup with a tilt detection function according to claim 1, wherein a light shielding means for shielding the line object is provided. 8. The optical pickup with a tilt detection function according to claim 7, wherein the light shielding means is provided in front of the condenser lens in the sub optical system. 9. The light-shielding means is located at the center of the cross section of the return sub-laser beam where the sub-laser beam is reflected on the signal surface of the optical disk, and corresponds to the one of the split axes on the detection surface of the split light detection means. The light is shielded in a substantially rectangular shape along the beam diameter to be formed, and the light is shielded in a substantially rectangular shape along the beam diameter corresponding to the other split axis on the detection surface of the split light detection means. An optical pickup with a tilt detection function according to claim 7 or 8. 10. A non-light detection area is provided on all or a part of a range of a main lobe generated by a return sub-laser beam in a detection surface of a split light detection means, and a line object is located on any of the two split axes. The optical pickup with a tilt detection function according to claim 7, wherein: