JPH0935304A - Optical recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record/reproduce disks with different thicknesses without mechanically switching objective lenses by dividing and making incident a light beam from a light source to/on plural pieces of objective lenses arranged on the same lens holder. SOLUTION: When the thick disk 12 is arranged selectively, the light beam outgoing from a semiconductor laser 21 is made incident on a prism 23 with a beam splitter through a grating lens 28 and a collimate lens 22, and passes through the joint surface of the prism 23 to be focused on the disk 12 by the objective lens 1a. On the other hand, when the thin disk 13 is arranged selectively, the light beam outgoing from the semiconductor laser 21 is made incident on the prism 23 through the lenses 28, 22, and is reflected by the surface opposite to the joint surface of the prism 23 and the joint surface of a parallelogram prism to be focused on the disk 13 by the objective lens 1b. Thus, the necessity that the objective lenses 1a, 1b are switched dynamically according to the disks 12, 13 with different thicknesses is eliminated, and a switch means is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for optically writing or reading information on a disc-shaped recording medium.

[0002]

2. Description of the Related Art An optical recording / reproducing apparatus uses an objective lens as a recording medium in order to correct a focus shift due to vertical movement of a warp of an optical disc such as a CD (compact disc) or a magneto-optical disc and a tracking shift due to eccentricity. Recording or reproduction is performed optically by driving in two axes of a focus direction perpendicular to the surface and a tracking direction parallel to the recording medium surface.

In recent years, optical disks (or simply referred to as disks) have become larger in capacity and higher in density like DVDs (digital video disks). There are several means for achieving high density of the disk, but a typical one is to increase the NA of the objective lens. As a result, the diameter of the light spot focused by the objective lens can be reduced,
Higher density is achieved. However, the objective lens N
When A is increased, the influence of the aberration due to the tilt of the disc becomes more likely. In order to reduce this effect, it is necessary to reduce the thickness of the disk. In fact, the disc thickness is 1.2 mm for CD, but the disc thickness is 0.1 mm for DVD.
It is 6 mm. Therefore, it is difficult to reproduce the CD with the objective lens for DVD. CD and DVD
Since it is necessary to change the NA of the objective lens, for example, in order to reproduce a CD and a DVD with the same device, it is necessary to switch two objective lenses depending on whether the CD is reproduced or the DVD is reproduced. At this time, the optical recording / reproducing apparatus is naturally required to have a performance capable of reproducing or recording both CD and DVD in the same apparatus.

An example of the above-mentioned conventional optical recording / reproducing apparatus will be described below with reference to the drawings. FIG. 5 is a plan view of a conventional optical recording / reproducing apparatus, and FIG. 6 is a front view showing an optical configuration of the conventional optical recording / reproducing apparatus. Reference numeral 12 is a disc, and discs of two types of thickness are selectively arranged, such as a CD or a DVD. 1a and 1b are 2
First and second focusing respectively on discs of different thickness
Objective lens. Reference numeral 2 is a lens holder that holds the objective lenses 1a and 1b. 5a and 5b are lens holders 2
Is a focusing coil for driving the lens in the focusing direction F and is fixed to the lens holder 2. Reference numerals 6a and 6b are first and second tracking coils for driving the first objective lens 1a and 7a and 7b, respectively, for driving the second objective lens in the tracking direction T, which are fixed to the lens holder 2. . Reference numeral 8 denotes an axis, which is coupled with the lens holder 2, and the lens holder 2 slides and rotates along the axis 8 to move in the focus direction F and the tracking direction T.
Reference numeral 21 is a semiconductor laser that emits a light beam, 22 is a collimator lens that converts the light beam emitted from the semiconductor laser 21 into parallel light, and 23 is a structure in which two prisms having a substantially triangular cross section are joined together to form a substantially square cross section. Then, the first beam splitter which transmits a part of the light beam emitted from the collimator lens 22 at the cemented surface and makes it enter the objective lens 1a or 1b, and reflects a part of the light beam reflected from the disk 12 at the cemented surface. Reference numeral 24 denotes a convex lens for collecting the light beam reflected by the first beam splitter 23. Reference numeral 25 denotes two prisms having a substantially triangular cross section, which are joined to each other in a substantially square section, and the convex lens is formed at the joint surface. A second beam splitter that transmits a part of the light beam condensed by 24 and reflects a part of the light beam, and 26 represents a part of the light beam separated by the second beam splitter 25. An information detecting detector for detecting information in a part, 27 is a focus / tracking error detecting detector for performing servo detection for focusing and tracking with a part of the light beam separated by the second beam splitter 25, 20 is various optical elements (21 to 2
An optical stand for attaching and fixing 7). Further, 10 is the center of the disk 12, and 11 is a part of the information track on the center of the light beam incident on the disk 12 from the semiconductor laser 21.

Next, the operation of the conventional optical recording / reproducing apparatus having the above structure will be described. When the disk 12 is selectively arranged, when the objective lens 1a is used corresponding to the disk 12, the first tracking coil 6 in the magnetic circuit (not shown) fixed to the optical table 20 is provided.
The lens holder 2 is rotated by a and 6b along the axis 8 fixed to the optical table 20 via a base (not shown) so that the objective lens 1a is placed on the information track 11 (the semiconductor laser 21 enters the disk 12). Then, the servo detection and information detection in the focus direction F and the tracking direction T are performed. Similarly, when the objective lens 1b is used, the lens holder 2 is rotated along the axis 8 by the second tracking coils 7a and 7b in the magnetic circuit (not shown) fixed to the optical table 20. After 1b is placed on the information track 11, servo detection and information detection in the focus direction F and the tracking direction T are performed.

[0006]

In the optical recording / reproducing apparatus having the above-mentioned structure, the objective lens needs to be switched depending on the disc, so that two drive coils are required in the tracking direction, and the objective lens is used. Since they are arranged in the substantially tracking direction, the size of the entire apparatus becomes large. Also, for example, a CD-RO stored in a cartridge
When M and DVD are reproduced by the same device, interference between the objective lens and the cartridge at the innermost peripheral position of the disc becomes a problem.

The present invention solves the above problems,
An object of the present invention is to provide an optical recording / reproducing apparatus for recording / reproducing information on / from a selectively arranged disk having a different thickness without mechanically switching a plurality of objective lenses.

[0008]

In order to achieve the above object, in the optical recording / reproducing apparatus of the present invention, a plurality of objective lenses are arranged in the same lens holder in a direction substantially orthogonal to the focus direction and the tracking direction. The light beam from the light source is separated, the optical path of the separated light beam is changed, and the light beam is incident on each objective lens.

[0009]

According to the present invention, since it is not necessary to dynamically switch the objective lens by the disk due to the above-mentioned structure,
Since no mechanical switching means is required and the objective lens is arranged in a direction substantially orthogonal to the focusing direction and the tracking direction, the overall size of the device is prevented from increasing, and the objective lens is used even when recording / reproducing the disc stored in the cartridge. Does not interfere with the cartridge.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of an optical recording / reproducing apparatus according to the first embodiment of the present invention, and FIG. 2 is a front view showing an optical configuration of the optical recording / reproducing apparatus of the same embodiment. In FIGS. 1 and 2, reference numerals 12 and 13 denote first and second disks as two kinds of disk-shaped recording media having different thicknesses such as CD or DVD, and either one of them is selectively arranged. It 1a is a first objective lens that focuses on the disk 12, and 1b is a second objective lens that focuses on the disk 13.
Objective lens. Reference numeral 2 is a lens holder that holds the objective lenses 1a and 1b. 5a and 5b are lens holders 2
Is a focusing coil for driving the focusing direction F (the optical axis direction perpendicular to the disks 12 and 13),
It is fixed to the lens holder 2. Tracking coils 6a and 6b drive the lens holder 2 in the tracking direction T (radial direction parallel to the disks 12 and 13) and are fixed to the lens holder 2.

Reference numeral 4 denotes a fixing member, and four metal wires 3a
The lens holder 2 is supported via ~ 3d. The wires 3a to 3d (the wire 3c is not shown) are attached to the lens holder 2 at one end and the fixing member 4 at the other end and are arranged so as to be substantially parallel to each other. It is translated in two axes in the tracking direction T.

Reference numeral 21 is a semiconductor laser as a light source for emitting a light beam, 28 is a grating lens as a diffraction element for branching the light beam emitted from the semiconductor laser 21 into a main beam and two auxiliary beams, and 22 is a grating lens 28. It is a collimating lens that converts the emitted light beam into parallel light. Reference numeral 23 denotes two prisms each having a substantially triangular shape and a substantially parallelogram-shaped cross section, which are joined so that the cross section becomes a substantially trapezoidal shape, and a part of the light beam emitted from the collimator lens 22 is transmitted through the joint surface to the objective lens 1a. Disk 12
Part of the light beam reflected from the collimator lens 22 is reflected by the surface facing the cemented surface and the cemented surface of the parallelogram prism, and is made incident on the objective lens 1b. , A prism with a beam splitter that transmits a part of the light beam reflected from the disk 13 at the cemented surface. That is, the prism 23 with a beam splitter serves as both a light beam splitting element and an optical path changing element.

Reference numeral 24 denotes a convex lens for collecting the light beam emitted from the prism 23 with a beam splitter after the light beam is reflected by the disks 12 and 13, and 25 denotes the convex lens 2.
A beam splitter that transmits a part of the light beam condensed by 4 and reflects a part of the light beam, and 26 detects an information signal recorded on the disks 12 and 13 by a part of the light beam separated by the beam splitter 25. An information detecting detector 27 serves as means for performing servo detection for focusing and tracking with a part of the light beam separated by the beam splitter 25, and means for detecting a focus error signal and a tracking error signal. A focus and tracking error signal detecting detector (hereinafter, F and T error detecting detector) 20 is an optical base for mounting and fixing various optical elements (21 to 28).

The objective lenses 1a and 1b are arranged in a direction substantially orthogonal to the focus direction F and the tracking direction T. Further, 10 is the center of the disks 12 and 13, and 11 is a part of the information track on the center of the light beam incident on the disks 12 and 13 from the semiconductor laser 21. Further, the optical table 20 has a fixed magnetic yoke (not shown) and the like, and constitutes a magnetic circuit together with the focusing coils 5a and 5b and the tracking coils 6a and 6b, and the lens holder 2 is used in the focusing direction F and the tracking direction. An objective lens driving device that drives to T is formed.

The operation of the optical recording / reproducing apparatus of the first embodiment of the present invention constructed as above will be described. CD and L
When the thick disk 12 such as D (laser disk) is selectively arranged, the light beam emitted from the semiconductor laser 21 enters the prism 23 with the beam splitter through the grating lens 28 and the collimator lens 22. The incident light beam passes through the cemented surface of the prism 23 with a beam splitter, is focused on the disk 12 by the objective lens 1a, is reflected by the disk 12, and is reflected by the objective lens 1a to the prism 23 with a beam splitter. Incident. The reflected light beam is reflected by the cemented surface of the prism 23 with a beam splitter and is applied to the information detecting detector 26 and the F and T error signal detecting detector 27 via the convex lens 24 and the beam splitter 25.

Then, the lens holder 2 is fixed by the focusing coils 5a and 5b and the tracking coils 6a and 6b in a magnetic circuit (not shown) fixed to the optical table 20.
The fixing member 4 fixed to the optical table 20 via the wires 3a to 3d is translated in the focus direction F and the tracking direction T to perform servo and information detection in the focus direction F and the tracking direction T.

Here, since the optical axis of the objective lens 1a is arranged in the tracking direction T passing through the center 10 of the disk 12, servo detection in the tracking direction T when the objective lens 1a is used (tracking error signal detection)
A so-called three-beam tracking method can be used for detecting the difference in reflected light amount of the auxiliary beam diffracted by the grating lens 28.

When the thin disk 13 such as a DVD is selectively arranged, the light beam emitted from the semiconductor laser 21 is reflected by the grating lens 28 and the collimator lens 22.
And enters the prism 23 with a beam splitter. The incident light beam is reflected by the surface of the prism 23 with the beam splitter and the surface of the parallelogram prism facing the bonding surface, and is focused on the disk 13 by the objective lens 1b. The light enters the prism 23 with the beam splitter via the lens 1b. The reflected light beam is reflected by the surface of the prism 23 with a beam splitter, which is opposite to the joint surface of the parallelogram prism, passes through the joint surface, and passes through the convex lens 24 and the beam splitter 25 to detect the information detecting detectors 26 and F. , T error signal detecting detector 27 is irradiated.

The lens holder 2 is fixed by the focusing coils 5a and 5b and the tracking coils 6a and 6b in a magnetic circuit (not shown) fixed to the optical table 20.
The fixing member 4 fixed to the optical table 20 via the wires 3a to 3d is translated in the focus direction F and the tracking direction T to perform servo and information detection in the focus direction F and the tracking direction T.

Here, since the optical axis of the objective lens 1b is not arranged in the tracking direction T passing through the center 10 of the disc 13, the relative position of the information track 11 on the inner and outer circumferences of the disc 13 with respect to the objective lens 1b. Since the angle deviation is large, it is difficult to detect the tracking error with the auxiliary beam. Therefore, for example, for servo detection in the tracking direction T when the objective lens 1b is used, the tracking error detecting detector 27 is divided into lines that are substantially coincident with the tangential direction map of the information track 11 on the optical axis of the objective lens 1b. The so-called push-pull method for detecting the difference in the reflected light quantity of the main beam diffracted by the grating lens 28 or the so-called phase difference method for detecting the phase difference in the change in the light quantity of the main beam is used. At this time, if the effective light beam diameters of the objective lens 1a and the objective lens 1b are made substantially the same, the light spot diameters incident on the F and T error signal detecting detectors 27 can be made substantially the same, so that the servo is performed with the same division pattern. The signal can be detected.

As described above, according to this embodiment, since it is not necessary to dynamically switch the objective lens by the disks 12 and 13 having different thicknesses, no mechanical switching means is required, and two objective lenses are used. Is arranged in a direction substantially orthogonal to the focus direction F and the tracking direction T, the size of the entire apparatus is prevented from increasing, and the objective lens and the cartridge are used even when recording and reproducing a disc housed in a cartridge such as a CD-ROM. It is possible to realize an optical recording / reproducing device that does not interfere with each other.

Next, an optical recording / reproducing apparatus according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a plan view of the optical recording / reproducing apparatus of this embodiment, and FIG. 4 is a front view showing the optical configuration of the optical recording / reproducing apparatus of the same embodiment. The difference between this embodiment and the first embodiment is that the optical axes of the objective lenses 1a and 1b are at the center 1 of the disks 12 and 13.
The points are arranged substantially symmetrically with respect to the tracking direction T passing through 0, and the point without the grating lens 28. Other configurations and operations are similar to those of the first embodiment.

3 and 4, 12 and 13 are
For example, two types of discs having different thicknesses such as a CD or a DVD are selectively arranged. 1a is a first objective lens focused on the disk 12, and 1b is a disk 1
It is a second objective lens focusing on 3. Reference numeral 2 is a lens holder that holds the objective lenses 1a and 1b. 5a, 5
Reference numeral b denotes a focusing coil for driving the lens holder 2 in the focusing direction F, which is fixed to the lens holder 2. Tracking coils 6a and 6b for driving the lens holder 2 in the tracking direction T are fixed to the lens holder 2.

Reference numeral 4 denotes a fixing member, which is made of metal wires 3a to 3d.
The lens holder 2 is supported via. Wire 3a ~
3d has one end attached to the lens holder 2 and the other end attached to the fixing member 4, and is arranged so as to be substantially parallel to each other, and translates the lens holder 2 in two axes of the focus direction F and the tracking direction T. Reference numeral 21 is a semiconductor laser that emits a light beam, 22 is a collimator lens that converts the light beam emitted from the semiconductor laser 21 into parallel light, and 23 is two prisms having a substantially triangular shape and a substantially parallelogram cross section, and the cross section is substantially trapezoidal. And the objective lens 1a by transmitting a part of the light beam emitted from the collimator lens 22 at the cemented surface.
To reflect a part of the light beam reflected from the disk 12 and to reflect a part of the light beam emitted from the collimator lens 22 on the surface facing the cemented surface and the cemented surface of the parallelogram prism. A prism with a beam splitter that allows a part of the light beam that is incident on the objective lens 1b and that is reflected from the disc 13 to pass through at the joint surface, and 24 is the disc 1
Prism 2 with beam splitter after being reflected by 2 and 13
A convex lens for condensing the light beam emitted from 3; 25, a beam splitter which transmits a part of the light beam condensed by the convex lens 24 and reflects a part thereof; 26, a light beam which is separated by the beam splitter 25 A detector for detecting information for detecting information in a part of the beam splitter 27.
An F and T error signal detection detector for performing servo detection for focusing and tracking with a part of the light beam separated by 5, and an optical stand 20 for mounting and fixing various optical elements (21 to 27). . Also, 10 is a disk 1
In the centers of 2 and 13, 11 indicates a part of the information track on the center of the light beam entering the disks 12 and 13 from the semiconductor laser 21.

The operation of the optical recording / reproducing apparatus of the second embodiment of the present invention constructed as above will be described. CD and L
When a thick disk 12 such as a D (laser disk) is selectively placed, the objective lens 1a is used in correspondence with the disk 12 for focusing in a magnetic circuit (not shown) fixed to the optical table 20. The coil 5a, 5b and the tracking coils 6a, 6b connect the lens holder 2 to the wire 3
The fixing member 4 fixed to the optical table 20 via a to 3d is translated in the focus direction F and the tracking direction T to perform servo and information detection in the focus direction F and the tracking direction T.

When a thin disk 13 such as a DVD is selectively placed, an objective lens 1b is used corresponding to the disk 13 and a focusing coil 5a in a magnetic circuit (not shown) fixed to the optical table 20. , 5b and tracking coils 6a, 6b, the lens holder 2 is connected to the wires 3a-3.
The fixing member 4 fixed to the optical table 20 via d is translated in the focus direction F and the tracking direction T to perform servo and information detection in the focus direction F and the tracking direction T.

Here, since the optical axes of the objective lenses 1a and 1b are arranged substantially symmetrically with respect to the tracking direction T passing through the center of the disk 13, for example, the tracking direction T
For servo detection of F, T error signal detector 2
7 is divided into two by a dividing line which substantially coincides with the tangential direction mapping of the information track 11 on the tracking direction T, and the disc 1
2 or the so-called push-pull method for detecting the light amount difference of the reflected light from the disk 13 or the so-called phase difference method for detecting the phase difference of the light amount change is used. At this time, if the effective light beam diameters of the objective lens 1a and the objective lens 1b are made substantially the same, the light spot diameters incident on the F and T error signal detecting detectors 27 can be made substantially the same, so that the servo is performed with the same division pattern. The signal can be detected.

As described above, according to this embodiment, the objective lenses 1a and 1b are formed by the disks 12 and 13 having different thicknesses.
Since there is no need to dynamically switch the lens, there is no need for mechanical switching means, and since the objective lens is arranged in a direction substantially orthogonal to the focus direction and the tracking direction, it is possible to prevent the apparatus from becoming large in size, It is possible to realize an optical recording / reproducing apparatus in which the objective lens and the cartridge do not interfere with each other even when recording / reproducing a disk housed in a cartridge such as a ROM.

[0029]

As is apparent from the above description, according to the optical recording / reproducing apparatus of the present invention, a plurality of objective lenses are arranged in the same lens holder in a direction substantially orthogonal to the focusing direction and the tracking direction. , Since the light beam from the light source is separated, the optical path of the separated light beam is converted and is made incident on each objective lens,
Since it is not necessary to dynamically switch a plurality of objective lenses by discs having different thicknesses, there is no need for a mechanical switching means, and further, a plurality of objective lenses are arranged in a direction substantially orthogonal to the focus direction and the tracking direction. Therefore, it is possible to realize an optical recording / reproducing apparatus in which the objective lens and the cartridge do not interfere with each other even when recording / reproducing a disk housed in a cartridge such as a CD-ROM.

[Brief description of drawings]

FIG. 1 is a plan view of an optical recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a front view showing an optical configuration of an optical recording / reproducing apparatus in the embodiment.

FIG. 3 is a plan view of an optical recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 4 is a front view showing the optical configuration of the optical recording / reproducing apparatus in the embodiment.

FIG. 5 is a plan view of a conventional optical recording / reproducing apparatus.

FIG. 6 is a front view showing an optical configuration of a conventional optical recording / reproducing apparatus.

[Description of Reference Signs] 1a, 1b Objective lens 2 Lens holder 3a to 3d Wire 4 Fixing member 12 First disk 13 Second disk 20 Optical stage 21 Semiconductor laser 22 Collimating lens 23 Beam splitter prism 24 Convex lens 25 Beam splitter 26 Information detection detector 27 Focus and tracking error detection detector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yutaka Murakami 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A plurality of objective lenses corresponding to the thickness of the disk-shaped recording medium for optically writing or reading information on the disk-shaped recording media having different thicknesses which are selectively arranged at substantially coaxial positions. Lens holder that holds the
An objective lens driving device having a mechanism for driving in a radial direction parallel to a recording medium surface of the disk-shaped recording medium and an optical axis direction perpendicular to the recording medium surface, a light source, and the light source. Beam separating element having a function of separating the light beam from the light beam, an optical path changing element for causing the light beams separated by the light beam separating element to enter the plurality of objective lenses, and a focus on the disc-shaped recording medium. Optical recording comprising: means for detecting an error signal, means for detecting a tracking error signal on the disk-shaped recording medium, and means for detecting an information signal on the disk-shaped recording medium. Playback device. 2. The optical recording / reproducing apparatus according to claim 1, wherein a plurality of objective lenses are arranged in a direction substantially orthogonal to the optical axis direction and the radial direction. 3. A collimator lens for converting a light beam emitted from the light source into parallel light is disposed in an optical path between the light source and the plurality of objective lenses, and the effective light beam diameters of the plurality of objective lenses are substantially the same. The method according to claim 1, wherein
An optical recording / reproducing apparatus as described in the above. 4. A disk-shaped recording medium among a plurality of objective lenses, comprising a diffraction element having a function of generating a main beam and at least two auxiliary beams in an optical path between a light source and a plurality of objective lenses. When using an objective lens arranged in the radial direction including the central axis of, the tracking error signal is obtained by the two auxiliary beams, and when other objective lenses are used, the tracking error signal is obtained by the main beam. The optical recording / reproducing apparatus according to claim 1, which is obtained.