JPH1069648A - Optical pickup device and method of adjusting the optical pickup device - Google Patents

Abstract

(57) [Summary] [Problem] To improve the numerical aperture of an objective lens,
Provided are an optical pickup device and a method for adjusting the optical pickup device, which enable highly reliable recording and reproduction of information signals. An optical pickup device includes a first lens having a curved surface or a flat surface facing an optical recording medium and having a numerical aperture set to a predetermined value. A second lens 3 disposed so as to be interposed therebetween, a condensing optical system for condensing light reflected from the surface of the optical recording medium 5, and a first lens 6 and a second lens 3 The first moving means 2 for moving in the axial direction, the second moving means 11 for moving the first objective lens 6 relative to the second objective lens 3 in the optical axis direction, and the second moving means 9 Fixing means 12 for fixing the moved first lens 6. The method for adjusting the optical pickup device includes a moving step of adjusting the position of the first lens 6 in the optical axis direction;
Fixing the position of the lens 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup device for converging a laser beam on a signal recording surface of an optical recording medium and a method for adjusting the optical pickup device.

[0002]

2. Description of the Related Art In recent years, the density of disk-shaped recording media such as optical disks and magneto-optical disks as recording devices for computer systems and package media for music and image information has been increasing. One method for increasing the density of these recording media is to increase the numerical aperture of the objective lens provided in the optical pickup device, reduce the spot diameter of the laser beam irradiated on the recording medium, and reduce the recording pits. There is a method of increasing the density of the recording medium by increasing the density.

[0003] Generally, the diameter of a focused spot in an optical pickup device is given by λ / NA. Where λ
Is the wavelength of the laser light applied to the recording medium, and NA
Is the numerical aperture of the objective lens. Therefore, by increasing the numerical aperture of the objective lens, it is possible to irradiate the recording medium with laser light so as to reduce the diameter of the focused spot, thereby reducing the recording pits of the recording medium and improving the recording density. is there.

However, the numerical aperture of the objective lens is limited to about 0.6, mainly due to the manufacturing of the aspherical single lens used as the objective lens. Further, in order to keep the wavefront aberration of the laser beam caused by the inclination and warpage of the recording medium and the assembling accuracy of the optical pickup device within an allowable range, when the numerical aperture is large, it is necessary to make the disk substrate thinner. In a DVD (digital video disk), the thickness of the substrate is about 0.6.
mm.

On the other hand, as an objective lens unit having a numerical aperture of 0.6 or more, for example, an SIL (Solid Immersion Lens) is provided between the objective lens and a recording medium.
By disposing the lens, as a so-called two-group lens,
An optical system of an optical pickup device in which the numerical aperture is increased to 0.8 or more has been proposed.

[0006]

However, the above-mentioned objective lens unit has an S lens constituting one of the two group lenses.
It is necessary to keep the distance between the IL and the recording medium (hereinafter, referred to as an air gap) at an optimum value. If this air gap greatly changes, spherical aberration occurs on the surface of the recording medium, and an information signal from the recording medium, The output signal drops,
Further, there is a problem that it becomes impossible to record and / or reproduce the information signal on the recording medium.

On the other hand, in an optical disk recording and reproducing apparatus,
When the thickness of the substrate of the recording medium is constant, it is necessary to maintain the air gap at a constant value and the distance between the objective lens and the SIL at a constant value. The air gap and the distance between the objective lens and the SIL are kept constant by adjusting the positions of the objective lens and the SIL so that spherical aberration is minimized when assembling the above-described two-unit lens. I have.

Also, it is usually difficult to directly observe spherical aberration in an optical pickup device.

Accordingly, the present invention has been proposed in view of the above-mentioned circumstances, and has an optical pickup capable of improving the numerical aperture of an objective lens and capable of accurately recording and reproducing an information signal. It is an object of the present invention to provide a device and a method for adjusting the optical pickup device.

[0010]

An optical pickup device according to the present invention which solves the above-mentioned problems has a curved surface or a flat surface facing the surface of an optical recording medium, and the numerical aperture is set to a predetermined value. A first lens, a second lens disposed so as to sandwich the first lens between the optical recording medium, and a condensing optical system for condensing light reflected from the surface of the optical recording medium First moving means for moving the first lens and the second lens in the optical axis direction, and second moving means for moving the first lens in the optical axis direction with respect to the second lens. , The first moving means moved by the second moving means.
And fixing means for fixing the lens.

According to the optical pickup device configured as described above, the first lens is placed between the optical recording medium and the second lens.
And the first lens can be set at a constant distance from the signal recording surface of the optical recording medium, so that accurate information signal recording and reproduction on the optical recording medium can be performed. Becomes possible.

Further, according to the adjusting method of the optical pickup device of the present invention, the first lens having the curved surface or the flat surface facing the surface of the optical recording medium and having the refractive index set to a predetermined value is provided. A second lens disposed so as to sandwich the first lens between the first lens and an optical recording medium;
An adjustment method for adjusting the position of a first lens of an optical pickup device in a direction of an optical axis including a light collecting optical system for collecting light reflected from a surface of an optical recording medium, the method comprising: It has a moving step of moving the second lens in the optical axis direction and a fixing step of fixing the first lens moved in the moving step.

According to such an adjustment method of the optical pickup device, the first lens is placed between the optical recording medium and the second lens.
Since there is a moving step of disposing the first lens and moving the first lens in the optical axis direction with respect to the second lens, and fixing means for fixing the first lens at a predetermined position, One lens can be set at a fixed distance from the signal recording surface of the optical recording medium, and accurate recording and reproduction of information signals on the optical recording medium can be performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an optical pickup device according to the present invention and a method for adjusting the optical pickup device will be described in detail with reference to the drawings.

As shown in FIG. 1, the optical pickup device according to the present embodiment has an objective lens unit 1 for focusing a laser beam at a predetermined position on a disk. This objective lens unit 1 has a numerical aperture of about 0.45.
An objective lens 3 serving as a second lens, a pair of objective lens holders 4 for supporting the objective lens 3, and an objective lens 3 disposed on the same optical axis as the objective lens 3 and between the objective lens 3 and the disk 5. , A pair of front lens holders 7 supporting the front lens 6, the front lens holder 7 is moved in the optical axis direction, and the front lens 6 is moved. And an adjusting unit 9 for keeping an air gap 8 formed between the disk 5 and the disk 5 at a constant value. Also, this objective lens unit
It is mounted on a two-axis electromagnetic actuator that enables the objective lens 3 and the front lens 6 to move in the optical axis direction and the tracking direction.

When information is recorded on the magneto-optical disk, the optical pickup device applies a required external magnetic field to a predetermined area of the magneto-optical disk irradiated with the laser beam. Magnetic head 10 may be mounted.

The two-axis electromagnetic actuator drives the objective lens and the front lens in the optical axis direction and the tracking direction. That is, the two-axis electromagnetic actuator controls the focus by adjusting the distance between the front lens 6 and the disk 5 by applying signals obtained from the focus error signal and the tracking error signal, and irradiates the disk. It is possible to trace the laser beam to be emitted in a direction perpendicular to the track.

The objective lens 3 and the front lens 6 are arranged on a single optical axis to converge laser light on the disk 5. Further, the objective lens 6 and the front lens 3
Are arranged in this way to form a two-group objective lens, and the aperture ratio is improved to about 0.8. In the present embodiment, the front lens 6 is a hemispherical lens, so-called SIL (Solid Immersion).
n Lens), but an aspheric lens or the like may be used.

The front lens 3 is disposed so as to form an air gap 8 with the disk 5. The air gap 8 formed between the disk 5 and the front lens 6 is 2
Adjustment is possible with a shaft electromagnetic actuator.

The adjusting unit 9 includes a moving unit 11 for moving the front lens 6 and the front lens holder 7 in the optical axis direction, and a fixing unit 12 for fixing the moving unit 11 at a predetermined position.
Consists of

As shown in FIG. 2, the moving means 11 has a screw 4a provided on the outer periphery of the objective lens holder 4 and a screw 11 provided on the inner circumference of the ring which is the moving means 11.
a has a screwed structure. Here, an air film is provided between the objective lens holder 4 and the front lens holder 7 so that the position of the front lens 6 is smoothly adjusted. The end 7a of the front lens holder 7 is disposed in contact with the ring as the moving means 11, and the front lens 6 is moved in the optical axis direction as the moving means 11 moves in the optical axis direction. To be moved.

When the optical pickup device is assembled, the moving means 11 is rotated by a signal output from a moving means driving circuit provided in a front lens adjusting circuit to be described later, so that the front lens 6 and the front lens are rotated. By moving the lens holder 7 in the optical axis direction, the distance between the objective lens 3 and the front lens 6 and the distance between the front lens 6 and the disk 5 are changed.

Accordingly, since the moving means 11 can move the front lens 6 in the optical axis direction, the air gap 8 formed between the disk 5 and the front lens 6 can be optimally adjusted. It can be adjusted.

The fixing means 12 is constituted by, for example, a screw. When the optical pickup device is assembled, the fixing means 12 keeps the distance between the front lens 6 and the objective lens 3 constant by a signal output from a fixing means driving circuit provided in a front lens adjustment circuit described later. Keep in value.

The fixing means 12 is not limited to the above-mentioned screw, and the position of the front lens 6 may be fixed by bonding.

Therefore, since the fixing means 12 can fix the front lens 6 at a predetermined position, the distance between the objective lens 3 and the front lens 6 can always be kept constant. It becomes possible.

In the optical pickup device configured as described above, the air gap 8 is formed between the front lens 6 and the disk 5, so that the laser beam irradiated on the surface of the disk 5 has spherical aberration. Here, when a hemispherical lens is used as the front lens 6, the spherical aberration due to the air gap 8 formed by the SIL and the disk 5 is W
_40, the air gap amounts to is h, and the refractive index of the disc 5 is n, the numerical aperture of the two-group objective lens with _{sinθ 0, W 40 = - (} h / 8) n 2 (n 2 -1) sin ⁴ θ ₀ (1). If the spherical aberration represented by the equation (1) becomes large,
Reproduction characteristics when the optical pickup device reproduces an information signal from the disk 5 are significantly deteriorated.

For example, when the wavelength λ of the laser light emitted from the light source is 680 nm and the air gap amount h is 75 μm to form a two-group objective lens, a maximum wavefront aberration of about 3λ is generated from the equation (1). . Therefore, the optical pickup device according to the present embodiment eliminates the spherical aberration due to the asphericity by optimizing the asphericity of the objective lens 3 so that the air gap amount h becomes 75 μm and becomes astigmatic. The objective lens unit 1 is configured.

Here, when the thickness of the disk 5 is formed with a thickness error of Δt from a predetermined value t, the two-axis electromagnetic actuator operates the objective lens 3 and the tip of the objective lens 3 so that the error in the focusing direction is minimized. When the ball lens 6 is moved in the optical axis direction, the air gap amount h changes by Δt / n. At this time, the amount of spherical aberration ΔW _40D caused by the disk 5 and the amount of spherical aberration ΔW _40A caused by the air gap 8 are represented by ΔW _40D = (Δt ² / 8a) n (n−1) where a is the radius of the SIL. sin ⁴ θ ₀ (2) ΔW _40A = − (Δt / 8) n (n ² −1) sin ⁴ θ ₀ (3)

The radius a of the hemispherical lens is 1.25 m.
m, the refractive index n of the objective lens is 1.5, and the NA of the objective lens unit 1 is 0.8, sin θ ₀ =
It is necessary to set the thickness error Δt of the disk 5 to about 10 μm or less so that the total amount of wavefront aberration ΔW _40D + ΔW _40A expressed by the equations (2) and (3) as 0.533 becomes λ / 4 or less. is there.

On the other hand, when a disk reproducing apparatus is configured using an objective lens having a high numerical aperture, when the thickness of the substrate is increased, the tolerance for coma caused by the inclination of the disk is significantly reduced. Therefore, as described above, in order to configure a two-group objective lens having an aperture ratio of the objective lens of 0.6 or more and to reproduce the disk, it is necessary to reduce the thickness of the disk substrate.

The objective lens unit 1 described above is mounted on an optical system 20 of an optical pickup device applied to, for example, a magneto-optical disk shown in FIG. Here, since the objective lens unit 1 is mounted on and integrated with the two-axis electromagnetic actuator, a conventional method can be applied as it is as a method of focus control and tracking control. An optical system 20 of the optical pickup device includes a semiconductor laser 21 that emits laser light having a wavelength of 680 nm, a collimating lens 22 that parallelizes the laser light emitted from the semiconductor laser 21, and a laser that has passed through the collimating lens 22. A diffraction grating 23 for diffracting light, and a beam splitter 25 for dispersing the laser light passing through the diffraction grating 23 to the objective lens 3 and the lens 24
And the objective lens 3 and the front lens 6 that receive the laser beam passing through the beam splitter 25 and converge the laser beam on the magneto-optical disk 5.

In the optical system 20 of the optical pickup device, the laser light emitted from the semiconductor laser 21 enters the beam splitter 25 via the collimator lens 22 and the diffraction grating 23, and a part of the light is collected by the lens 24. The light is incident on the photodetector 26. This photodetector 2
Reference numeral 6 denotes an unillustrated A as an output signal of the incident laser light.
PC (Automatic Power Contro)
l) Supply to the circuit. This APC circuit includes a photodetector 26
Is controlled so that the amount of laser light emitted from the semiconductor laser 21 and applied to the magneto-optical disk 5 becomes constant.

On the other hand, the reflected laser light from the magneto-optical disk 5 passes through the front lens 6 and the objective lens 3 again, and
A part of the p-polarized component (for example, 30%) and an s-polarized component are reflected on the beam splitter 25, are reflected on the beam splitter 27, and a part of the laser light passing through the beam splitter 27 is partially converted into a lens 28. Into the polarization beam splitter 3 via the half-wave plate 29.
Leads to zero. The polarization beam splitter 30 splits the incident light into a p-polarized component and an s-polarized component,
1 and the lens 32.

The laser beam reflected by the beam splitter 27 and guided to the lens 28 is incident on a photodetector 34 via a lens 33 that gives astigmatism, and is converted into an electric signal corresponding to the light intensity. The signal is converted and supplied to a servo head amplifier described later as a servo error signal. The laser beam that has passed through the polarizing beam splitter 30 enters the photodetector 36 via the lenses 31 and 35, and enters the photodetector 38 via the lenses 32 and 37. The laser light incident on the photodetectors 36 and 38 is
It is converted into an electric signal according to the light intensity and output. Then, the output signal is differentially amplified and reproduced RF
The signal is output as an (high frequency) signal to an RF head amplifier described later.

FIG. 4 shows the electrical configuration of the optical pickup device 20 configured as described above.
In FIG. 4, the magneto-optical disk 5 is driven to rotate at a constant angular velocity by a spindle motor 39 when recording and / or reproducing information signals. Here, a predetermined area of the magneto-optical disk 5 is irradiated with a laser beam, and an information signal can be recorded as a recording pit. Further, in the configuration of FIG. 4, the recorded information is irradiated by irradiating a predetermined area of the magneto-optical disk 5 rotated at a constant speed with a laser beam and detecting the amount of reflected laser beam. The signal can be reproduced.

At this time, the above-described optical pickup device 2
The servo error signal output from the photodetector 34 provided for the servo amplifier 40 is amplified by the servo head amplifier 40 to detect a focus error.
And a tracking error signal detecting circuit 42 for detecting a tracking error.

The focus error signal output from the focus error signal detection circuit 41 and the tracking error signal output from the tracking error signal detection circuit 42 are phase-compensated by phase compensation circuits 43 and 44, respectively, and then amplified by an amplifier 45. , 46 at a predetermined gain. Then, the amplified tracking error signal and focusing error signal are input to the optical pickup device 20 and drive the two-axis electromagnetic actuator to drive the objective lens unit 1 in the tracking direction and the focusing direction.

It should be noted that the amplifiers 45 and 46 operate in the phase compensating circuit 4 in a normal operation state in which the focus servo is locked.
Although the output of No. 3 is selected as an input, when a control signal for focus servo pull-in from the control unit 47 is input, the control signal is changed to a search signal from the control unit 47 and a pull-in operation is performed.

The RF signal output from the optical pickup device 20 is input to an RF head amplifier 48,
After being amplified by a predetermined gain, signal processing is performed by a decoding circuit (not shown), and the information signal recorded on the magneto-optical disk 5 is reproduced as a reproduction RF signal.

The reproduced RF signal is input to a front lens adjusting circuit 49 so as to be used for adjusting the objective lens unit 1 when assembling the optical pickup device. The front lens adjustment circuit 49 includes the front lens 6
Is moved in the direction of the optical axis so that the input reproduced RF signal becomes the best. When the reproduced RF signal becomes the best, the front lens 6 is fixed.

The front lens adjusting circuit 49 receives the reproduction signal, moves the objective lens unit 1 in the optical axis direction, controls the adjusting unit 9 for fixing the objective lens unit 1 at a predetermined position, and controls the objective lens 3 and the front lens. While adjusting the distance from the lens 6,
An air gap 8 formed between the front lens 6 and the magneto-optical disk 5 is maintained at a constant value.

As shown in FIG. 5, the front lens adjustment circuit 49 receives the signal from the RF head amplifier 48 and detects the amplitude peak of the reflected laser light from the magneto-optical disk 5. And the signal from the amplitude peak detection circuit 49a
A driving means driving circuit 49b for adjusting the position of the front lens 6 by driving the
a driving circuit 4 for driving the fixing means 12 which receives the signal from the input means a and fixes the front lens 6 at a predetermined position.
9c.

The amplitude peak detection circuit 49a receives a reproduction RF signal from the light amount signal of the laser beam applied to the magneto-optical disk 5 via the RF head amplifier 48. And
The amplitude peak detection circuit 49a receives the input reproduced RF signal.
By detecting a change in signal amplitude, a change in the amount of reflected light from the magneto-optical disk 5 is detected.

The amplitude peak detecting circuit 49a sends a control signal to the moving means driving circuit 49b so that the moving means 11 is moved in the optical axis direction by the input reproduced RF signal so that the amplitude of the reproduced RF signal becomes the best. Is output. And
The amplitude peak detection circuit 49a outputs a control signal to the fixing means driving circuit 49c so as to fix the moving means 11 when the reproduced RF signal becomes the best.

The moving means driving circuit 49b receives the control signal from the amplitude peak detecting circuit 49a, and converts the laser beam irradiating the magneto-optical disk 5 to minimize the wavefront aberration caused by the air gap 8 and the surface of the magneto-optical disk 5. So that
This is a circuit for controlling the moving means 11.

Here, when the thickness of the magneto-optical disk 5 deviates from a predetermined thickness, spherical aberration occurs as described above. At this time, the moving means driving circuit 49b outputs a signal for moving the front lens 6 in the optical axis direction to minimize the spherical aberration and to move the front lens 6 to a position where the reproduced RF signal is optimal. Therefore, by inputting the signal from the moving means driving circuit 49b to the moving means 11, the light amount signal from the optical pickup device 20 changes, and the position of the front lens 6 is adjusted so that the reproduced RF signal becomes the best. It is possible to

The fixed manual drive circuit 49c receives the control signal from the amplitude peak detection circuit 49a when the reproduced RF signal is at its best, and
Is output so that is fixed at a predetermined position.

When the position of the front lens 6 is adjusted, the front lens adjustment circuit 49 having the above-described configuration reproduces the reproduction RF signal.
Since the signal is detected and the adjustment in the optical axis direction is performed, the laser beam can be focused on a predetermined area of the magneto-optical disk 5 without causing wavefront aberration. It is possible to record and reproduce information signals on the magneto-optical disk 5 and to improve the recording density of the magneto-optical disk 5.

The above-described front lens adjustment circuit 49 adjusts the position of the front lens 6 as follows. The position adjustment of the front lens 6 is performed when the optical pickup device 20 is assembled. The position adjustment method of the front lens 6 for adjusting the position of the front lens includes a step of moving the front lens 6 facing the disk 5 in the optical axis direction, and a step of fixing the front lens 6 at a predetermined position. Having.

The step of moving the front lens 6 in the optical axis direction is a step of detecting the reproduced RF signal from the RF head amplifier 48 by the amplitude peak detecting circuit 49a and controlling the moving means driving circuit 49b.

Here, the reproduction RF signal input to the amplitude peak detection circuit 49a includes the influence of spherical aberration as wavefront aberration caused by the thickness of the disk substrate. Therefore, the amplitude peak detection circuit 49a adjusts the position of the front lens 6 so that the influence of the reproduced RF signal due to such spherical aberration is reduced.

FIG. 6 shows the calculated value of the reproduced RF signal of the optical pickup device when a certain amount of spherical aberration exists as the wavefront aberration. FIG. 6 is a diagram in which the vertical axis represents the modulation signal of the reproduced RF signal, and the horizontal axis represents the spatial frequency of the optical pickup device. In FIG. 6, the difference of the modulation signal between the case where spherical aberration exists and the case where spherical aberration does not exist is that the spatial frequency is about 400 to about 800 (cycles / cycle).
mm). Therefore, when the frequency is about 400 to about 800 (cycles / mm), the influence of the spherical aberration is most remarkably received.

Therefore, in the method of adjusting the position of the front lens 6 according to the present embodiment, the step of driving the front lens 6 facing the magneto-optical disk 5 in the optical axis direction includes:
Approximately 400 to 800 (cycle) which is easily affected by spherical aberration
Since the front lens 6 is adjusted in the frequency band of (es / mm), it is possible to perform adjustment with high sensitivity to spherical aberration.

Next, in the step of fixing the front lens 6 at a predetermined position, after the position of the front lens 6 is adjusted, the front lens 6 is set at a position where the reproduced RF signal has a maximum value. Is fixed. The control signal from the amplitude peak detection circuit 49a is input to the fixing means driving circuit 49c.
Then, the fixing means 12 provided in the optical pickup device to which the control signal is input is fixed.

Therefore, according to such a method for adjusting the position of the front lens 6, the step of moving the front lens 6 facing the magneto-optical disk 5 in the optical axis direction, and the step of moving the front lens 6 to the predetermined position. The distance between the front lens 6 and the objective lens 3 and the air gap 8 formed by the front lens 6 and the magneto-optical disk 5 can be set with high precision. Possible and
It is possible to keep it at a constant value.

For example, a DVD (Digital Video Disk) is used in the optical pickup device according to the present embodiment.
When a signal subjected to modulation equivalent to the above is recorded and reproduced on the magneto-optical disk 5, the frequency band corresponds to
The mark length is in the vicinity of 4T to 6T (T: 1 channel clock). By adjusting the position of the front lens 6 so that the amplitude of these reproduced signal components is maximized, the thickness of the disk substrate is shifted. Thus, it is possible to minimize the spherical aberration caused by this and to reproduce an excellent information signal.

Similarly, the entire reproduced RF signal also has a wavefront aberration due to the deviation of the thickness of the disk substrate,
Since the modulation signal is affected, the front lens 6 may be adjusted so that the enprobe which is a waveform based on the maximum value and the minimum value of the amplitude of the reproduced RF signal is optimized.

Further, in this optical pickup device, it is effective to adjust the front lens 6 so that the reproduction RF signal is not affected by the wavefront aberration and the time axis fluctuation of the reproduction RF signal is minimized.

The above-mentioned spherical aberration is caused not only when reproducing the information signal recorded on the magneto-optical disk but also when recording the information signal due to the deviation of the thickness of the magneto-optical disk substrate. Therefore, in a device capable of recording and reproducing an information signal, such as an optical pickup device in a magneto-optical disk described in the present embodiment, when recording an information signal, the influence of spherical aberration is previously determined as in a ROM disk. It is desirable that the front lens 6 be adjusted by reproducing the magneto-optical disk 5 on which a signal in a frequency band in which the frequency becomes remarkable. Further, a signal for adjusting the front lens 6 may be preformatted on a part of the magneto-optical disk 5.

As described above, the optical pickup device and the method for adjusting the front lens can be applied to a magneto-optical disk as described above. The present invention is also applicable to an optical pickup device for reproducing a DVD or the like.

Further, the adjustment method of the front lens is not limited to the so-called automatic adjustment method of the front lens as in the above-described adjustment method of the optical pickup device, and the reproduction RF signal is detected by, for example, an oscilloscope to adjust the front lens. The adjustment of the optical pickup device may be performed manually.

[0063]

As described above in detail, in the optical pickup device according to the present invention, the first lens can be adjusted in the optical axis direction so as to optimize the distance between the first lens and the optical recording medium. And holding the distance between the first lens and the optical recording medium to be constant,
Since a fixing means for holding the distance between the first lens and the second lens so as to be constant is provided, it is possible to set an optimum lens position according to the optical recording medium and to obtain a high aperture. Since the number of lenses is realized, the recording density of the optical recording medium can be improved.

The method for adjusting the optical pickup device according to the present invention includes a first lens having a curved surface or a flat surface facing the surface of the optical recording medium and having a numerical aperture set to a predetermined value; An optical pickup device comprising: a second lens disposed so as to sandwich the first lens between the optical recording medium; and a condensing optical system that condenses light reflected from the surface of the optical recording medium. This is an adjustment method for adjusting the position of the first lens in the optical axis direction. The method for adjusting the optical pickup device includes a moving step of moving the first lens and the second lens in the optical axis direction, and a fixing step of fixing the first lens moved in the moving step. Therefore, it is possible to set the optimal position of the first lens according to the optical recording medium, and to realize an objective lens with a high numerical aperture, thereby improving the recording density of the optical recording medium. become.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an objective lens unit mounted on an optical pickup device according to the present invention.

FIG. 2 is an enlarged view of a main part showing an example of a vicinity of a moving unit of an adjustment unit provided in the objective lens unit.

FIG. 3 is a configuration diagram showing an example of an optical system of the optical pickup device.

FIG. 4 is a block diagram showing an example of an electrical configuration of the optical pickup device.

FIG. 5 is a block diagram showing an example of a front lens adjustment circuit provided in the optical pickup device.

FIG. 6 is a diagram showing the spatial frequency dependence of the optical pickup device when there is a spherical aberration of the modulation signal detected by the optical pickup device and when there is no spherical aberration.

[Explanation of symbols]

1 objective lens unit, 3 objective lenses, 5 discs, 6 front lenses, 8 air gap, 9 adjustment section, 1
Reference Signs List 1 moving means, 12 fixing means, 20 optical pickup device, 51 front lens adjustment circuit, 51a amplitude peak detection circuit, 51b moving means driving circuit, 51c fixing means driving circuit

Continued on the front page (72) Inventor Kiyoshi Osato 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Toshio Watanabe 6-35, 7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation Inside the company (72) Inventor Atsushi Fukumoto 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Akira Suzuki 6-35-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (6)

[Claims] 1. An optical pickup device for converging a laser beam emitted from a light source on a signal recording surface of an optical recording medium, wherein the optical pickup device has a curved surface or a flat surface facing the surface of the optical recording medium, and has a predetermined numerical aperture. A first lens set to a value, a second lens disposed so as to sandwich the first lens between the optical recording medium, and light reflected from the surface of the optical recording medium. A condensing optical system that emits light, a first moving unit that moves the first lens and the second lens in an optical axis direction, and an optical axis direction that moves the first lens with respect to the second lens. An optical pickup device, comprising: a second moving means for moving the first lens; and a fixing means for fixing the first lens moved by the second moving means. 2. The optical pickup device according to claim 1, wherein a ring designed to move in an optical axis direction is used as said second moving means. 3. The optical pickup device according to claim 1, wherein a screw or an adhesive is used for said fixing means. 4. A method for adjusting an optical pickup device for converging laser light emitted from a light source on a signal recording surface of an optical recording medium, wherein the optical pickup device has a curved surface or a flat surface facing the surface of the optical recording medium, and is refracted. A first lens whose ratio is set to a predetermined value, a second lens disposed so as to sandwich the first lens between the first lens and the optical recording medium, and a second lens disposed between the first lens and the surface of the optical recording medium. An adjustment method for adjusting the position of the first lens of an optical pickup device having a light collecting optical system for collecting reflected light in the optical axis direction, wherein the first lens and the second lens are A method for adjusting an optical pickup device, comprising: a moving step of moving in the optical axis direction; and a fixing step of fixing the first lens moved in the moving step. 5. The adjustment method for an optical pickup device according to claim 4, wherein said moving step is performed based on a signal obtained by detecting reflected light from said optical recording medium. 6. The method according to claim 4, wherein the moving step is performed so that the amplitude of a signal obtained by detecting light reflected from the optical recording medium is maximized. .