JPH1064115A - Optical pickup device, and recording and/or reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of recording and reproducing by simultaneously executing the change of numerical aperture and the correction of aberrations of an objective lens with an aperture varying means and an aberration correcting means. SOLUTION: The light from a semiconductor laser 2 is made incident on the objective lens 10 via an aperture and aberration variable element 3 capable of changing the aperture and aberration as the aperture varying means and the aberration correcting means, by which the writing and reading out of the information signals at the points irradiated and converged with the laser beam on an optical disk 1a or 1b are executed. The return light from the recording surface heads toward a photodetector 11. The element 3 has piezoelectric elements 6a to 6d and an annular elastic supporting body 7 between a transparent plate 4 and a thin glass sheet 5. A housing part 7a is filled with an electrolyte prepd. by melting AgBr. A toric transparent electrode 8 precipitates Ag atop the electrode 8 by current supply. The region shields the light and electrochemically changes the numerical aperture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of an optical pickup device for writing and reading information signals on an optical recording medium such as an optical disk.

[0002]

2. Description of the Related Art Conventionally, optical recording media such as optical disks and optical cards have been proposed as recording media for information signals.
An optical pickup device for writing and reading information signals to and from such an optical recording medium has been devised.

As shown in FIG. 14, the optical pickup device includes a semiconductor laser 60 as a light source, a beam splitter 61 into which laser light emitted from the semiconductor laser 60 is incident, and a light passing through the beam splitter 61. It has an objective lens 62 to be incident and a photodetector 63. The beam splitter 61 is disposed so that its reflection surface is inclined at 45 ° with respect to the optical axis of the laser light emitted from the semiconductor laser 60. The laser light is reflected on the reflecting surface and enters the objective lens 62.

The objective lens 62 converges the laser beam reflected by the beam splitter 61 on a desired recording track on a signal recording surface of the optical disc 64. Further, the objective lens 62 is supported by a biaxial actuator (not shown) so as to be movable in a focusing direction which is an optical axis direction and a tracking direction which is orthogonal to the optical axis and orthogonal to a recording track of the optical disk.

The return light reflected on the signal recording surface reaches a beam splitter 61 via an objective lens 62. In the beam splitter 61, a part of the return light is directed to the photodetector 63, and the other return light is
Go to zero.

The photodetector 63 is a light receiving element such as a photodiode, and receives the light that has passed through the beam splitter 61 and converts the light into an electric signal. The information signal recorded on the optical disk 64 is reproduced based on the detection output from the photodetector 63.

[0007]

Incidentally, in the above-mentioned optical disk, the recording density of information signals has been increased as an auxiliary storage medium for computers.

[0008] The above-mentioned optical disk includes an optical disk having a signal recording layer on which information signals are recorded on a transparent substrate formed in a disc-like shape having a thickness of 1.2 mm from a synthetic resin having a light transmitting property, for example, a polycarbonate resin, or a polycarbonate resin. There has been proposed an optical disk or the like having a signal recording layer on a transparent substrate formed into a disk-like shape having a thickness of 0.6 mm and bonding the signal recording layers together.

In order to record and reproduce information signals on and from the optical disk having a high recording density, the objective lens has a larger numerical aperture (NA).
It is necessary to reduce the beam spot diameter on this optical disk.

However, when the numerical aperture of the objective lens is increased, the tolerance for the inclination, thickness unevenness, and defocus of the beam spot on the signal recording surface of the optical disk is reduced. Becomes unstable.

For example, when the tilt angle (skew angle) of the optical disk with respect to the optical axis of the objective lens increases,
Wavefront aberration occurs in the light converged on the signal recording surface, and the detection output characteristics from the photodetector deteriorate.

This wavefront aberration is dominated by tertiary coma which occurs in proportion to the cube of the numerical aperture of the objective lens and the skew angle. Therefore, the allowable value for the tilt angle is inversely proportional to the cube of the numerical aperture of the objective lens, and thus becomes smaller as the numerical aperture increases.

Further, since an optical disk having a substrate thickness of 1.2 mm is mass-produced, the skew angle is, for example, ± 0.5 ° to 1 ° when reproducing or recording the optical disk.
May occur.

In such an optical disk, the beam spot becomes asymmetric due to the third-order coma aberration, and the intersymbol interference increases remarkably. Therefore, it is difficult to accurately reproduce the information signal recorded on the signal recording surface.

On the other hand, since the amount of the third-order coma is proportional to the substrate thickness of the optical disk, it is necessary to reduce the third-order coma in a 0.6 mm optical disk having a thin substrate. it can.

In consideration of the above, it is necessary to develop a technique for reproducing optical disks having different shapes as described above using the same system.

By the way, when a parallel flat plate having a thickness t, for example, a disk substrate, is inserted into the optical path of the light beam converged by the objective lens, t × (NA) is related to the thickness t and the numerical aperture NA. Spherical aberration proportional to ⁴ occurs.

The above-mentioned objective lens is designed to correct this spherical aberration. That is, since the amount of spherical aberration that occurs when the thickness of the substrate differs, the objective lens is designed so as to be adapted to a predetermined substrate thickness.

Then, for example, by using an objective lens designed and adapted to an optical disk having a substrate thickness of 0.6 mm,
When trying to reproduce an optical disk with a substrate thickness of 1.2 mm, the difference in substrate thickness of 0.6 mm greatly exceeds the allowable range of the error of the substrate thickness that the optical pickup device can cope with. However, there is a problem that the beam spot is not sufficiently condensed and good reproduction cannot be performed.

By the way, mechanical diaphragm means for changing the numerical aperture of the objective lens according to the thickness of the substrate of the optical recording medium such as the optical disk have been proposed. However, providing a mechanical diaphragm leads to a complicated and large-sized optical pickup device. Also,
Since the objective lens is moved by the two-axis actuator following the optical recording medium, the positional relationship between the objective lens and the stop fluctuates, and the correction of spherical aberration by the objective lens is performed in a favorable state. It becomes difficult to maintain.

Further, most of the aberration correcting means has a mechanical drive mechanism, and cannot perform desired desired correction aberration, which is not very practical.

Accordingly, the present invention has been proposed in view of the above-mentioned circumstances, and not only selects an appropriate numerical aperture but also prevents skew and semiconductor laser non-uniformity for optical recording media having different substrate thicknesses. It is an object of the present invention to provide an optical pickup device and a recording and / or reproducing device that can arbitrarily correct aberrations up to a point difference.

[0023]

In order to solve the above-mentioned problems, an optical pickup device according to the present invention comprises a light source and an object for converging a light beam emitted from the light source on a signal recording surface of an optical recording medium. A lens, light detection means for detecting the reflected light of the light beam from the signal recording surface, and an enclosing body disposed in an optical path between the light source and the objective lens, and an opaque formed inside the enclosing body. A transparent electrode for depositing a transparent precipitate and an electrolytic solution contained in the enclosure and for depositing an opaque deposit on the transparent electrode. An aperture varying means for depositing an opaque deposit from the inside on the transparent electrode and changing the diameter of a light beam incident on the objective lens from the light source;

In the present invention, the variable aperture means includes an aberration correction element for correcting aberration.

On the other hand, an optical pickup device according to the present invention comprises a light source, an objective lens for condensing a light beam emitted from the light source on a signal recording surface of an optical recording medium, and an optical lens for the light beam from the signal recording surface. Light detection means for detecting reflected light,
A pair of parallel flat plates disposed in an optical path between the light source and the objective lens and disposed in parallel with each other, and a piezoelectric element for displacing at least one of the pair of flat plates; Aberration correction means for correcting the aberration of the light beam incident on the lens.

In the present invention, the aberration correction means includes an aperture variable element for changing the diameter of the incident light beam.

On the other hand, a recording and / or reproducing apparatus according to the present invention comprises: a light source; an objective lens for condensing a light beam emitted from the light source on a signal recording surface of an optical recording medium; Light detection means for detecting the reflected light of the light flux, thickness detection means for detecting the thickness of the optical recording medium based on the reflected light from the signal recording surface, and a light source and the objective lens An enclosing body disposed in an optical path between the enclosing body and a transparent electrode formed inside the enclosing body for depositing an opaque precipitate; And an aperture that changes the diameter of a light beam incident on the objective lens from the light source by depositing an opaque precipitate from the electrolyte on the transparent electrode by applying a current to the electrolyte through the transparent electrode. Variable means.

Further, in the present invention, the aperture changing means includes:
An aberration correction element for correcting aberration is provided.

Further, the recording and / or reproducing apparatus according to the present invention comprises a light source, an objective lens for condensing a light beam emitted from the light source on a signal recording surface of an optical recording medium, Light detection means for detecting the reflected light of the light flux, thickness detection means for detecting the thickness of the optical recording medium based on the reflected light from the signal recording surface, and a light source and the objective lens A pair of parallel flat plates and a pair of parallel flat plates arranged in parallel with each other and having a variable aperture element arranged in an optical path between the light sources to change the diameter of a light beam incident on the objective lens from the light source; and at least one of the pair of flat plates An aberration correcting means for correcting the aberration of the incident light beam, comprising a piezoelectric element for displacing the flat plate.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

The optical pickup device according to the present invention in this embodiment has a thickness of 0.6 m as shown in FIG.
The first optical disk 1a, which is an optical recording medium using a transparent substrate of m, and the second optical disk 1b, which is an optical recording medium using a transparent substrate of 1.2 mm in thickness, are used to transmit information signals. An optical pickup device capable of recording and reproducing.

The first optical disk 1a records a signal on one principal surface of a disk-shaped substrate having a thickness of 0.6 mm (D ₂ ) and a diameter of 120 mm made of a synthetic resin having a light transmitting property, for example, polycarbonate. Layers. The first optical disk 1a is a double-sided disk having a thickness of 1.2 mm, in which two optical disks are bonded together on the signal recording layer side.

The recording and reproduction of information signals on and from the first optical disk 1a are performed by using a laser beam having a wavelength of 635 or 650 nm via an objective lens that is designed to have a numerical aperture (NA) of 0.6. This is made possible by irradiating the signal recording surface of the first optical disk 1a.

Further, the second optical disk 1b has a first
It is formed by molding a polycarbonate resin similarly to the optical disk 1a. Specifically, thickness 1.2mm
(D ₁ ) A signal recording layer is provided on one main surface of a disk-shaped substrate having a diameter of 80 mm or 120 mm.

The recording and reproduction of information signals on the second optical disk 1b are performed by using a laser beam having a wavelength of 780 nm through an objective lens adapted so that the numerical aperture becomes 0.45. It becomes possible by irradiating the signal recording surface.

As shown in FIG. 1, the optical pickup device has a semiconductor laser 2 as a light source. The semiconductor laser 2 emits linearly polarized laser light having a wavelength of 635 nm.

The laser light is first passed through an aperture / aberration variable element 3 which can change the aperture and aberration, which is an aperture variable means and an aberration correction means, so as to be suitable for recording and reproduction of a mounted optical disk. It is adjusted and enters the beam splitter 9.

As will be described later, the aperture / aberration variable element 3 has a structure in which the diameter of the incident laser beam can be changed and the aberration can be changed simultaneously or separately.

The beam splitter 9 on which the laser beam that has passed through the aperture / aberration variable element 3 is incident is disposed with its main surface inclined at 45 ° to the optical axis of the laser beam. The beam splitter 9 reflects the laser beam by the main surface and deflects the laser beam by 90 degrees. The laser light having passed through the beam splitter 9 is incident on an objective lens 10.

The objective lens 10 has a numerical aperture of 0.6, and when a plane-parallel plate having a thickness t of 0.6 mm is inserted into the optical path of the convergent light beam condensed by the objective lens 10. , T × (NA) ⁴ are designed to be corrected. That is, the objective lens 10 is designed to be suitable for the first optical disk 1a having a substrate thickness of 0.6 mm.

The objective lens 10 includes the objective lens 10
The first optical disc 1a or the second optical disc 1
It is supported by a two-axis actuator composed of a focus servo that is controlled to irradiate the recording track b with laser light and a tracking servo that is controlled to follow the recording track. Thereby, the objective lens 1
Numeral 0 is moved by the biaxial actuator in the optical axis direction (focus direction) and in the direction perpendicular to the optical axis and perpendicular to the recording track (tracking direction).

Thus, the first optical disk 1a or the second optical disk 1a
The recording and reproduction of the optical disk 1b can be performed, and the laser beam passing through the objective lens 10 is irradiated, and the writing and reading of the information signal at the converged portion are performed.

As described above, the laser beam irradiated on the signal recording surface of the first optical disk 1a or the second optical disk 1b modulates the light amount or the polarization direction according to the information signal on the signal recording surface. Then, the light is reflected by the objective lens 10.

That is, the return light from the signal recording surface reaches the beam splitter 9 via the objective lens 10. In this beam splitter 9, a part of the return light goes to the semiconductor laser 2, and the other return light passes through the beam splitter 9 and goes to the photodetector 11.

The photodetector 11 is a light receiving element such as a photodiode, and receives the return light passing through the beam splitter 10 and converts it into an electric signal. An information signal recorded on the optical disk is reproduced based on the electric signal.

The reproducing or recording operation by the laser beam irradiated from the semiconductor laser 2 and passed through the aperture / aberration variable element 3 arranged in the optical path has been described.

Next, the configuration and operation of the aperture / aberration variable element 3 will be described in detail.

As shown in FIGS. 2 and 3, the aperture / aberration variable element 3 has a transparent plate 4 and a thin glass plate 5 rich in elastic deformation. The four piezoelectric elements 6a, which are piezoelectric elements, are sandwiched between
6b, 6c, 6d and an annular elastic support 7 are provided. On the transparent plate 4, an annular transparent electrode 8 is provided.

The center axis of the elastic support 7 provided in the aperture / aberration correction element 3 and the center axis of the annular transparent electrode 8 coincide with the optical axis of the laser beam transmitted through the aperture / aberration variable element 3. I do. Also, four piezo elements 6a, 6b, 6c, 6
d are arranged on concentric circles centered on the optical axis, and are arranged so that they are equally spaced.

The accommodating portion 7a sandwiched between the transparent member 4 and the thin glass plate 5 and surrounded by the elastic support member 7 is made of AgB.
r (silver bromide) is filled with a molten electrolytic solution.

The elastic support 7 is grounded by a terminal connected to the elastic support 7, and the annular transparent electrode 8 is connected to a current source via a changeover switch.

When the current is supplied from the power source, Ag is deposited on the annular transparent electrode 8 on the upper surface of the annular transparent electrode 8. At this time, since the region to be deposited is in an opaque state, the region blocks light, and the numerical aperture can be electrochemically changed.

In this case, since the diameter of the laser beam emitted from the semiconductor laser 2 is limited as shown in FIG. 5, the numerical aperture of the objective lens 10 is 0.37. On the other hand, when no current is supplied to the ring-shaped transparent electrode 8, the deposition of Ag on the ring-shaped transparent electrode 8 disappears, so that the ring-shaped transparent electrode 8 does not become opaque. As shown in FIG. It becomes 6.

The aperture / aberration varying means 3 is provided in
And an annular transparent electrode 8 on the transparent plate 4 as shown in FIG.
May be provided by disposing a central transparent electrode 12 inscribed on the inner peripheral surface of the above.

In this case, the numerical aperture can be changed in the same manner as described above by making the annular transparent electrode 8 opaque. On the other hand, by making only the central transparent electrode 12 opaque, the first
The beam spot diameter on the signal recording surface of the optical disc 1a or the second optical disc 1b is reduced, and recording and reproduction at an ultra-high density can be performed.

The means for limiting the aperture may be, for example, a liquid crystal panel instead of the transparent electrode as described above. In this case, the optical axis is controlled by controlling the opaque position by the crystal. A variable aperture element that can follow eccentricity can be created.

On the other hand, in the aperture / aberration variable element 3, the expansion and contraction of the piezo elements 6a, 6b, 6c and 6d are controlled by driving units of the piezo elements which are independently connected to each other. The shape of No. 5 can be arbitrarily changed to form an aspherical shape.

The driving section includes the piezo elements 6a, 6
Each of the piezo elements can be expanded and contracted by selectively applying a positive voltage or a negative voltage to b, 6c, and 6d. With this driving unit, the length of the piezo element does not change when the applied voltage is zero, but expands with a positive voltage and contracts with a negative voltage.

For example, the piezo elements 6a, 6b, 6
It is possible to deform the thin glass plate 5 into 81 aspherical shapes simply by changing the lengths of c and 6d in three stages (+ voltage, no application, and −voltage) by the driving unit.

As a specific example, the piezo element 6a,
When the lengths of 6b, 6c and 6d are changed, A- in FIG.
FIGS. 8 to 10 show the shape of the thin glass plate 5 obtained in the A section.
Shown in

That is, the piezo elements 6a, 6b, 6c,
When all of 6d shrinks, as shown in FIG.
Is a deformation in which the central part is separated from the transparent plate 4, that is, the aspherical shape of the convex lens as a whole. Also, the piezo element 6
When all of a, 6b, 6c, and 6d extend, as shown in FIG. 9, the thin glass plate 5 is deformed such that the central portion approaches the transparent plate 4, that is, the thin glass plate 5 has an aspherical shape of a concave lens as a whole.
Aberration correction can be performed by the deformed shape of the thin glass plate 5.

Further, the piezo element 6a on one side extends,
When the piezo element 6c on the other side shrinks, as shown in FIG.

In this case, an inclination sensor for detecting a change in the attitude of the first optical disk 1a or the second optical disk 1b, for example, a light detecting element such as a light emitting element for emitting light to the optical disk and a photodiode for detecting reflected light thereof. When it is detected from the skew detection sensor provided with the optical disc that the optical disc is tilted, aberration correction corresponding to the tilt of the optical disc can be performed by the shape of the thin glass plate 5 as shown in FIG.

Although the aberration can be corrected by the deformation of the thin glass plate 5, focusing servo and tracking servo can be performed. That is, at the time of focusing servo, spherical aberration is generated by concentric displacement of the thin glass plate 5, and a minute change in focal length is generated. At the time of tracking servo, by making the shape of the thin glass plate 5 inclined with respect to the transparent plate 4,
Perform tracking. Therefore, by controlling each of the four piezo elements, each servo operation can be performed in an auxiliary manner to the operation of the two-axis actuator, particularly, for a high-frequency component.

The thickness, material, and the like of the thin glass plate 5 are designed so as to be suitable for recording and reproduction of the first optical disk 1a. That is, aberration correction is performed during recording and reproduction of the first optical disk 1a. It is unnecessary. This eliminates the need to control the shape of the thin glass plate 5 by the piezo elements 6a, 6b, 6c, 6d during reproduction of the first optical disk 1a, thereby reducing power consumption.

The arrangement of the piezoelectric elements such as the piezo elements does not have to be arranged at a fixed place as described above, and the number of arrangements is not limited to four. Thus, a desired shape of the thin glass plate 5 can be created by changing the length of the piezoelectric element to an arbitrary length.
Further, the expansion and contraction operation by the piezoelectric element may be performed by an element that expands and contracts mechanically by driving a motor or a plunger, for example.

As described above, when recording and reproducing information signals on the first optical disk 1a, as shown in FIG. 4, the portion of the annular transparent electrode 8 of the aperture / aberration variable element is not made opaque. To allow the laser light to pass. Thereby, the numerical aperture of the objective lens 10 becomes 0.6. At this time, since the objective lens 10 is designed so as to be adapted for the first optical disk 1a, there is no need for aberration correction, and there is no need to deform the thin glass plate 5 by controlling expansion and contraction of the piezo element.

Thus, the original conditions for recording and reproducing the information signal on the first optical disk 1a, that is, the numerical aperture of the objective lens 10 is 0.6 and the wavelength of the laser beam is 63
The condition of 5 nm is satisfied, and a sufficient spatial frequency characteristic (Modulation transfer function; MTF) is obtained for all signals recorded on the first optical disk 1a, and good recording and reproduction can be performed.

On the other hand, when recording and reproducing information signals on the second optical disk 1b, as shown in FIG.
The portion of the annular transparent electrode 8 of the variable aperture / aberration element 3 is made opaque, and the substantial numerical aperture of the objective lens 10 is set to 0.37. At this time, in the aperture / aberration variable element 3, the shape of the thin glass plate 5 is changed by controlling the expansion and contraction of each piezo element, and appropriate aberration correction is performed.

The numerical aperture of the objective lens 10 depends on the original conditions for recording and reproducing information signals on the second optical disc 1b, that is, the numerical aperture of the objective lens 10 is 0.45.
In the condition that the wavelength of the laser beam is 780 nm, a beam spot having a diameter substantially equal to the beam spot diameter of the laser beam on the signal recording surface is formed.
Due to the relationship of × (635/780), it was changed to about 0.37.

Thus, the thickness of the substrate is 1.2 mm.
The spherical aberration occurring in relation to (t) and the numerical aperture (NA) of the objective lens 10, that is, in proportion to t × (NA) ⁴ , is suppressed by the decrease in the numerical aperture, and the second Good recording and reproduction on the optical disk 1b are realized.

Accordingly, a sufficient MTF can be obtained for all signals recorded on the second optical disk 1b, and good recording and reproduction can be performed.

The optical pickup device according to the present invention may be constituted by using an integrated device 20 such as a laser coupler as shown in FIG. The integrated device 20
Is a semiconductor laser 2 serving as a light source on a silicon substrate 21.
Two and a plurality of photodetectors 25 and 26 are formed. The beam splitter prism 23 is disposed on the photodetectors 25 and 26.

In this integrated device 20, the laser light emitted from the semiconductor laser 22 is reflected by the inclined surface 24 having an inclination of 45 ° which is one end of the beam splitter prism 23, and is reflected in the direction perpendicular to the silicon substrate 21. Is emitted. This laser light passes through the aperture / aberration variable element 3 and enters the objective lens 27 as in the optical pickup device described above.

The optical disk 1 is moved by the objective lens 27.
a or the laser beam converged on the signal recording surface of the optical disk 1b is reflected by the signal recording surface, passes through the objective lens 27 and the aperture / aberration variable element 3, and passes through the slope portion 24.
Return to The light that has returned to the slope 24 enters the beam splitter prism 23 while being refracted on the slope 24. The light that has entered the beam splitter prism 23 is applied to each of the photodetectors 25 and 26. Each of the photodetectors 25 and 26 outputs an electric signal corresponding to the emitted light.

Further, in the optical pickup device according to the present invention, as shown in FIG.
May be a parallel light beam. That is, the laser light emitted by the semiconductor laser 2 serving as a light source is transmitted through the collimating lens 31 to be a parallel light beam.

The laser light, which has become a parallel light beam as described above, passes through the aperture / aberration variable element 3 and reaches the beam splitter 32, is deflected by 90 ° by the main surface of the beam splitter 32, and is directed to the objective lens 33. Incident.

The optical disk 1 is moved by the objective lens 33.
The laser light converged on the signal recording surface of the optical recording medium 1a or the optical disk 1b is reflected on the signal recording surface to become return light. This return light passes through the objective lens 33 and the beam splitter 32, and passes through the condenser lens 34 to the light detector 35.
Is irradiated. The light detection unit 35 outputs an electric signal corresponding to the emitted light.

Next, an embodiment of the recording and / or reproducing apparatus according to the present invention will be described. As shown in FIG. 13, the recording and / or reproducing apparatus is a so-called optical disk recording / reproducing apparatus including an optical pickup device 40 for recording and reproducing signals on an optical recording medium such as an optical disk.

As shown in FIG. 1, the optical pickup device 40 has an aperture / aberration variable element 3 whose numerical aperture changes according to the optical disk and can perform aberration correction. Recording and reproduction of information signals on the signal recording surface of the first optical disk 1a having a signal recording layer on a substrate or the second optical disk 1b having a signal recording layer on a substrate having a thickness of 1.2 mm. I do.

That is, by selecting the numerical aperture at the time of reproduction of the optical disk by switching the switch of the annular transparent electrode 8 in accordance with the type of the mounted optical disk, under the condition suitable for the mounted optical disk. Recording and reproduction of information signals can be performed.

When the first optical disk 1a or the second optical disk 1b is mounted, the numerical aperture is set to 0.6, the signal of the mounted optical disk is read in this state, and the signal of this signal is read. From the content, it is possible to determine whether the loaded optical disk is the first optical disk 1a or the second optical disk 1b. That is, even if the numerical aperture at which the signal of the first optical disk 1a can be read, that is, the numerical aperture is set to 0.6, a part of the signal recorded on the second optical disk 1b can be read. Based on the read signal, it is possible to determine that the loaded optical disk is the second optical disk 1a. Thus the numerical aperture,
After judging whether the aberration correction is in an appropriate state, the recording and reproduction of the information signal can be performed on the signal recording surface of the optical disc.

For example, in the optical disk recording / reproducing apparatus shown in FIG. 13, the information signal converted into an electric signal by the optical pickup device 40 is sent to an analog waveform shaping circuit. The analog waveform shaping circuit 41 shapes the electric signal and converts it into a digital signal. The above digital signal is a phase locked circuit (Phase Locked Loo
The synchronization processing is performed by a synchronization detection circuit 43 having (p, PLL) 42. The digital signal subjected to the synchronization processing is detected and corrected by the digital signal processing circuit 44 based on the reference signal of the crystal oscillator 46 connected to the rotary servo 50. Thereafter, the digital signal sent from the digital signal processing circuit 44 is supplied to the D / A converter 45 and also to the sub-coating detection circuit 47. Here, the digital signal supplied to the D / A converter 45 is converted into an analog signal and output to an output device (not shown). On the other hand, the digital signal supplied to the sub-coating detection circuit 47 is transmitted to the actuator 51 as a so-called control signal. The access control of the connected tracking servo 49 is performed.

On the other hand, the reference signal from the crystal
Locking is performed by the LL 42, and the rotation servo 50 is controlled. The focus servo 48 is detected by detecting a focus error signal based on a signal from the optical pickup device 40.
Control.

The electric signal reproduced by the optical pickup device 40 as described above is output as an information signal to the outside via a D / A converter. On the other hand, the focus servo 48, the tracking servo 49, Further, it controls a rotary servo 50 connected to the spindle motor 52.

The recording and / or reproducing apparatus according to the present invention may be constituted by using an optical pickup device having an integrated element 20 (a so-called laser coupler) as shown in FIG.

Further, as shown in FIG. 12, the recording and / or reproducing apparatus according to the present invention comprises a collimator lens 31 for converting a laser beam incident on an aperture / aberration variable element into a parallel light beam.
May be configured using an optical pickup device having

[0088]

In the optical pickup device according to the present invention, the change of the numerical aperture of the objective lens and the correction of the aberration can be simultaneously performed by the aperture changing means and the aberration correcting means. Further, since the correction of the aberration can be performed continuously, the accuracy of recording and reproduction is improved.

In addition, the aberration correcting means can perform focus servo and tracking servo, particularly for high-frequency components, in an auxiliary manner to the operation of the biaxial actuator.

Further, since the aperture varying means, the aberration correcting means, and the lens system can be incorporated as one component, the optical pickup device can be made compact.

The recording and / or reproducing apparatus according to the present invention can automatically switch the numerical aperture of the objective lens and correct the aberration according to the recording medium on which the information signal is written and read.

[Brief description of the drawings]

FIG. 1 is a front view of an optical pickup device according to an embodiment of the present invention.

FIG. 2 is a front view of an aperture / aberration variable element.

FIG. 3 is a sectional view of the aperture / aberration variable element.

FIG. 4 is a diagram showing an operation example of changing the aperture in the aperture / aberration variable element.

FIG. 5 is a view showing another operation example of the aperture / aberration variable element different from that of FIG. 4;

FIG. 6 is a front view of another aperture / aberration variable element.

FIG. 7 is a sectional view of another aperture / aberration variable element.

FIG. 8 is a diagram showing an operation example of performing aberration correction in the aperture / aberration variable element.

FIG. 9 is a view showing another operation example of the aperture / aberration variable element different from that of FIG. 8;

FIG. 10 is a diagram showing another example of operation of the aperture / aberration variable element, which is different from FIGS. 8 and 9;

FIG. 11 is a front view of another optical pickup device different from FIG. 1 according to the embodiment of the present invention.

FIG. 12 is a front view of another optical pickup device different from FIGS. 1 and 11 according to the embodiment of the present invention.

FIG. 13 is a configuration diagram of a recording and / or reproducing apparatus according to an embodiment of the present invention.

FIG. 14 is a front view of a conventional optical pickup device.

[Explanation of symbols]

1a optical disk, 1b optical disk, 2 semiconductor laser, 3 aperture / aberration variable element, 4 transparent plate, 5 thin glass plate, 6a, 6b, 6c, 6d piezo element, 7 elastic support, 8 annular transparent electrode, 9 beam splitter ,
10 objective lens, 11 photodetector

Claims (10)

[Claims] A light source; an objective lens for converging a light beam emitted from the light source on a signal recording surface of an optical recording medium; and a light detecting means for detecting reflected light of the light beam from the signal recording surface; Disposed in an optical path between the light source and the objective lens;
A variable aperture for changing the diameter of a light beam incident on the objective lens from the light source; the variable aperture means includes an enclosure and a transparent electrode formed inside the enclosure to deposit opaque deposits And an electrolytic solution accommodated in the enclosure and for depositing an opaque deposit on the transparent electrode. A light source; an objective lens for converging a light beam emitted from the light source on a signal recording surface of an optical recording medium; and a light detecting unit for detecting reflected light of the light beam from the signal recording surface. Disposed in an optical path between the light source and the objective lens;
An aberration corrector for correcting an aberration of a light beam incident on the objective lens from the light source, wherein the aberration corrector includes a pair of parallel flat plates arranged in parallel with each other, and at least one flat plate of the pair of flat plates An optical pickup device comprising: a piezoelectric element for displacing the piezoelectric element. 3. The optical pickup device according to claim 1, wherein the aperture changing means includes an aberration correction element for correcting aberration. 4. The aberration correction element according to claim 3, wherein the aberration correction element comprises a pair of parallel flat plates arranged in parallel with each other, and a piezoelectric element for displacing at least one of the pair of flat plates. Optical pickup device. 5. The optical pickup device according to claim 2, wherein the aberration correction means includes a variable aperture element for changing a diameter of the incident light beam. 6. The optical pickup device according to claim 2, wherein the aberration correcting means performs focusing servo or tracking servo. 7. A light source, an objective lens for condensing a light beam emitted from the light source on a signal recording surface of an optical recording medium, and a light detecting means for detecting reflected light of the light beam from the signal recording surface A thickness detecting means for detecting a thickness of the optical recording medium based on the reflected light from the signal recording surface; and a thickness detecting unit disposed in an optical path between the light source and the objective lens,
A variable aperture for changing the diameter of a light beam incident on the objective lens from the light source; the variable aperture means includes an enclosure and a transparent electrode formed inside the enclosure to deposit opaque deposits A recording and / or reproducing apparatus, comprising: an electrolyte solution for depositing an opaque deposit on the transparent electrode, the electrolyte solution being contained in the enclosure. 8. The recording and / or reproducing apparatus according to claim 7, wherein the aperture changing means includes an aberration correction element for correcting aberration. 9. The aberration correction element according to claim 8, wherein the aberration correction element includes a pair of parallel flat plates arranged in parallel with each other and a piezoelectric element for displacing at least one of the pair of flat plates. Recording and / or playback device. 10. A light source, an objective lens for converging a light beam emitted from the light source on a signal recording surface of an optical recording medium, and a light detecting means for detecting reflected light of the light beam from the signal recording surface. A thickness detecting means for detecting a thickness of the optical recording medium based on the reflected light from the signal recording surface; and
An aperture variable element for changing a diameter of a light beam incident on the objective lens from the light source; and an aberration correcting unit for correcting aberration of the incident light beam, wherein the aberration correcting units are disposed in parallel with each other. A recording and / or reproducing apparatus comprising: a pair of parallel flat plates; and a piezoelectric element for displacing at least one of the pair of flat plates.