JP3837767B2 - Optical disk playback device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disc reproducing apparatus that records and / or reproduces a recording signal by irradiating an optical disc with light and detecting return light.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for example, an optical pickup for reproducing an optical disk on which image data is digitized and compressed and recorded is configured as shown in FIG.
In FIG. 11, the optical pickup 1 includes a semiconductor laser element 2, a beam splitter 3, a rising mirror 4, an objective lens 5, and a photodetector 6.
[0003]
According to the optical pickup 1 having such a configuration, the light beam emitted from the semiconductor laser element 2 is reflected by the reflecting surface 3 a of the beam splitter 3, further reflected by the rising mirror 4, and passed through the objective lens 5. Thus, an image is formed at a certain point on the signal recording surface of the optical disc 7.
[0004]
The return light beam reflected by the signal recording surface of the optical disc 7 enters the beam splitter 3 again through the objective lens 5. Here, the return light beam passes through the beam splitter 3 and enters the light receiving portion of the photodetector 6.
As a result, the information recorded on the signal recording surface of the optical disc 7 is reproduced based on the detection signal output from the photodetector 6.
[0005]
[Problems to be solved by the invention]
Incidentally, in recent years, optical disks have been increased in density as auxiliary storage devices for computers and audio / image information package media. In order to achieve this higher density, the numerical aperture NA of the objective lens is conventionally increased. Although there is a method of making the numerical aperture NA of the objective lens in the optical pickup for compact discs larger, there is a problem that if the numerical aperture NA is increased, the allowable range for the tilt of the optical disc is reduced.
[0006]
Further, since the optical disk is provided with a signal recording surface through a transparent substrate having a predetermined disk substrate thickness (generally 1.2 mm in the case of a compact disk or the like), the optical axis of the objective lens of the optical pickup is provided. On the other hand, when the optical disk is tilted, wavefront aberration occurs, which affects the reproduction of the RF signal. At this time, regarding the wavefront aberration, the third-order coma aberration generated in proportion to the third power of the numerical aperture and the first power of the skew angle θ is dominant.
Accordingly, an optical disc including a transparent substrate made of polycarbonate or the like that is mass-produced at low cost has a skew angle θ of, for example, ± 0.5 to ± 1 degrees. Therefore, due to the wavefront aberration, the semiconductor laser element of the optical pickup 1 Since the imaging spot from 2 to the optical disk 6 becomes asymmetric, the intersymbol interference is remarkably increased, and the accurate RF signal cannot be reproduced.
[0007]
Therefore, paying attention to the fact that this third-order coma aberration is proportional to the disc substrate thickness of the optical disc, the third-order coma aberration is halved by reducing the disc substrate thickness to half of 0.6 mm. Is possible.
In this case, there are two types of optical discs having different characteristics, that is, one having a relatively thick disc substrate thickness (for example, 1.2 mm) and one having a relatively thin disc substrate thickness (for example, 0.6 mm). become.
[0008]
Here, for example, when a parallel plate having a thickness t is inserted into the optical path, a spherical aberration proportional to t × (NA) 4 occurs with respect to the thickness t and the numerical aperture NA. Designed to cancel spherical aberration. By the way, since the spherical aberration also changes when the disc substrate thickness is different, an objective lens corresponding to an optical disc having one standard, for example, a 0.6 mm disc substrate thickness is used, and the other standard, for example, a compact having a disc substrate thickness of 1.2 mm is used. When an optical disk such as a disk, a write-once optical disk, or a magneto-optical disk is to be reproduced, a fourth-order spherical aberration occurs due to the difference in disk substrate thickness. It will greatly exceed the range. Therefore, there has been a problem that signals cannot be correctly detected from the return light from the optical disk.
[0009]
Thus, there is a problem that a plurality of optical discs cannot be reproduced by the conventional optical pickup.
[0010]
An object of the present invention is to provide an optical disk reproducing apparatus that can correctly reproduce an optical disk, regardless of the type of optical disk.
[0011]
[Means for Solving the Problems]
According to the present invention, the above object is achieved by a light source that emits a light beam, an objective lens that irradiates the light beam emitted from the light source so as to be focused on a signal recording surface of a rotationally driven optical disc, and a light source. In the optical path between the light source and the optical disk, the light separating means disposed between the objective lenses, the photodetector for receiving the return light beam from the signal recording surface of the optical disk separated by the light separating means, Opening means comprising a plate-like member provided, the opening means being rotatable about the support shaft as a pivot center, and the plate-like member is provided in the circumferential direction of the support shaft. Two openings having different sizes are provided, and the inner edge or the outer edge of the plate-like member in the vicinity of the support shaft is opposed to the inner peripheral side or the outer peripheral side in the radial direction of the optical disk of the optical pickup. No configuration provided with a Tsuno突output unit, optical pickups Opening means is moved together with the flop, one of the two collision detection section is, and is provided outside the inside or outermost from the innermost periphery of the optical disk is movable in a tangential direction of the optical disk, the two protrusions This is achieved by a disk reproducing apparatus in which the opening means is switched by abutting against the stopper of the optical disk apparatus moved to a position corresponding to .
[0012]
According to the above configuration, between the light source and the optical disc, the opening means is provided, in accordance with the disc substrate thickness of the optical disk to be reproduced, by the opening means is rocked by relative optical pickup An aperture having an appropriate numerical aperture of the aperture means is selected, and as a result, the spherical aberration is corrected.
In this case, when the optical pickup is moved to the inner periphery or the outer periphery of the optical disc, the plate-like member is centered on the support shaft by the projecting portion coming into contact with the stopper provided in the optical disc apparatus. It swings and one opening is placed in the optical path of the objective lens.
As a result, the light beam from the light source is correctly imaged on the signal recording surface of the optical disc through the aperture means, and the return light from the signal recording surface of the optical disc is incident on the optical detector, so that it is always optimal. Signal reproduction is performed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 1 to 10.
The embodiments described below are preferable specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention particularly limits the present invention in the following description. As long as there is no description of the effect, it is not restricted to these aspects.
[0014]
FIG. 1 shows an embodiment of an optical pickup of an optical disk reproducing apparatus according to the present invention.
In FIG. 1, an optical pickup 10 includes a semiconductor laser element 11 as a light source, a beam splitter 12 as light separation means, a rising mirror 13 as optical path bending means, an objective lens 14 and a photodetector 15, and a rising mirror 13. And an aperture means 16 disposed between the objective lens 14 and the objective lens 14.
[0015]
The semiconductor laser element 11 is a light emitting element utilizing semiconductor recombination emission, and is used as a light source. The light beam emitted from the semiconductor laser element 11 is guided to the beam splitter 12.
[0016]
The beam splitter 12 is arranged with its reflection surface inclined at 45 degrees with respect to the optical axis, and separates the light beam emitted from the semiconductor laser element 11 and the return light from the signal recording surface of the optical disc 17. That is, the light beam from the semiconductor laser element 11 is reflected by the reflecting surface 12 a made of a dielectric multilayer film of the beam splitter 12, and the return light passes through the beam splitter 12.
[0017]
The rising mirror 13 is an optical path bending mirror that reflects the light beam from the beam splitter 12 upward and reflects the return light from the optical disc 17 in the horizontal direction.
[0018]
The objective lens 14 is a convex lens, and forms an image of the light beam reflected by the beam splitter 12 on a desired track on the signal recording surface of the optical disk 17 that is rotationally driven. Further, the objective lens 14 is supported by a biaxial actuator 18 so as to be movable in the biaxial direction, that is, the tracking direction and the focusing direction.
[0019]
The photodetector 15 is configured to have a light receiving unit for the return light beam that has passed through the beam splitter 12.
[0020]
Here, the fixing portions of the semiconductor laser element 11, the beam splitter 12, the rising mirror 13, the photodetector 15 and the biaxial actuator 18 are attached to an optical case 19 as a base member for fixing and holding each optical element of the optical pickup. It is fixed against. The case 19 is disposed so as to be movable in the radial direction of the optical disc 17 along the guide rail 20 in an optical disc apparatus (not shown).
Therefore, the optical pickup 10, the case 19, and the biaxial actuator 18 constitute an optical disk recording and / or reproducing device.
[0021]
As shown in FIGS. 2 and 3, the opening means 16 is supported so as to be slidable in the radial direction of the optical disk 17 with respect to the case 19 of the optical pickup 10. The opening means 16 is formed of a plate-like member in the illustrated case and has two openings 16a and 16b arranged in the radial direction of the optical disk.
Of these openings 16a and 16b, the opening 16a is a relatively large opening, and the size is selected so as to have a numerical aperture corresponding to an optical disk having a relatively thin disk substrate thickness of 0.6 mm, for example. . The size of the opening 16b is selected so as to have a numerical aperture corresponding to an optical disk having a relatively thick disk substrate thickness of 1.2 mm, for example.
Further, the width of the plate-like member of the opening means 16 is set so that the side edge opposite to the opening protrudes from the side edge of the case 19 of the optical pickup 10 in a state where one of the openings 16a or 16b is selected. Have been selected.
[0022]
The optical pickup 10 according to the present embodiment is configured as described above, and a case where an optical disc (for example, a compact disc) having a relatively thin disc substrate thickness of 0.6 mm is reproduced will be described first.
In this case, the case of the optical pickup 10 is first moved along the guide rail 20 to the inner side of the innermost circumference 17a (of the track on which the signal is recorded) of the optical disc 17 as shown in FIG. Thereby, the opening means 16 abuts against the inner stopper 21 provided in the optical disc apparatus, and slides with respect to the case 19, so that the opening 16a is disposed in the optical path of the objective lens 14 of the optical pickup 10. .
[0023]
In this state, the light beam from the semiconductor laser element 11 is reflected by the reflecting surface of the beam splitter 12, reflected by the rising mirror 13, passes through the aperture 16 a of the aperture means 16, and further passes through the objective lens 14. Then, an image is formed on the signal recording surface of the optical disc 17.
At this time, the numerical aperture is appropriately set by the aperture means 16 , for example, NA = 0.6 . However, the objective lens 13 can suppress the spherical aberration most for an optical disc having a disc substrate thickness of 0.6 mm. Thus, the light beam is correctly imaged on the signal recording surface of the optical disc 17.
The return light from the optical disc 17 passes through the beam splitter 12 again through the objective lens 14, the aperture means 16, and the rising mirror 13 and forms an image on the photodetector 15. Thereby, the recording signal of the optical disc 17 is reproduced based on the detection signal of the photodetector 15.
[0024]
Next, when reproducing an optical disk having a relatively thick disk substrate thickness of 1.2 mm,
As shown in FIG. 5, the case of the optical pickup 10 is moved along the guide rail 20 to the outside of the outermost periphery 17 b (of the track on which the signal is recorded) of the optical disc 17. As a result, the opening means 16 comes into contact with the outer stopper 22 provided in the optical disc apparatus, and slides with respect to the case 19 so that the opening 16b is disposed in the optical path of the objective lens 14 of the optical pickup 10. .
[0025]
In this state, the light beam from the semiconductor laser element 11 is reflected by the reflecting surface of the beam splitter 12, reflected by the rising mirror 13, and then transmitted through the opening 16b of the opening means 16, and further the objective lens. 14, an image is formed on the signal recording surface of the optical disc 17.
At this time, since the numerical aperture is appropriately set by the aperture means 16, for example, NA = 0.4 , since the spherical aberration can be suppressed low, the light beam is correctly imaged on the signal recording surface of the optical disc 16. Will do.
The return light from the optical disc 17 passes through the beam splitter 12 again through the objective lens 14, the aperture means 16, and the rising mirror 13 and forms an image on the photodetector 15. Thereby, the recording signal of the optical disc 17 is reproduced based on the detection signal of the photodetector 15.
[0026]
6 and 7 show a second embodiment of the disk recording and / or reproducing apparatus according to the present invention.
6 and 7, only the opening means 31 is shown in the optical pickup 30, but in the case 32, a semiconductor laser element, a beam splitter, and the like having the same configuration as the optical pickup 10 in FIGS. A rising mirror, an objective lens and a photodetector are provided.
[0027]
Here, as shown in FIGS. 6 and 7, the opening means 31 is a plate-like member, and is located at a point A set slightly proximal to the center of the plate-like member with respect to the case 32 of the optical pickup 30. A support shaft is provided and supported so as to be swingable about A. Further, the opening means 31 which is a plate-like member has two openings 31a and 31b provided side by side in the tangential direction of the optical disc and arranged side by side on the front end side from the swing center A.
Of these openings 31a and 31b, the opening 31a is a relatively large opening, and the size is selected so as to have a numerical aperture corresponding to an optical disk having a relatively thin disk substrate thickness of 0.6 mm, for example. . The size of the opening 31b is selected so as to have a numerical aperture corresponding to an optical disk having a relatively thick disk substrate thickness of 1.2 mm, for example.
Further, the opening means 16 includes projecting portions 31c and 31d projecting in the width direction on the base end side opposite to the tip end side where the opening 31a or 31b is provided.
[0028]
According to the optical pickup 30 having such a configuration, when reproducing an optical disk having a relatively thick disk substrate thickness of 1.2 mm, the case of the optical pickup 30 is first provided with a guide rail 20 as shown in FIG. The protrusion 31c of the opening means 31 is brought into contact with the inner stopper 21 provided in the optical disk device, so that it swings with respect to the case 32 and opens. 31 b is arranged in the optical path of the objective lens of the optical pickup 30.
[0029]
In this state, the optical pickup 30 reproduces the optical disc, and the aperture means 31 sets the numerical aperture appropriately. Therefore, the light beam is correctly imaged on the signal recording surface of the optical disc, and the signal reproduction of the optical disc is correctly performed.
[0030]
Next, when reproducing an optical disk having a relatively thin disk substrate thickness of 0.6 mm, the case 32 of the optical pickup 30 extends along the guide rail 20 from the outermost periphery of the optical disk to the outside as shown in FIG. The protrusion 31d of the opening means 31 is moved to abut against the outer stopper 22 provided in the optical disc apparatus, so that it swings with respect to the case 32, and the opening 31b is in the optical path of the objective lens of the optical pickup 30. Be placed.
In this state, the optical pickup 30 reproduces the signal of the optical disc, and the aperture means 31 sets the numerical aperture appropriately. Therefore, the light beam is correctly imaged on the signal recording surface of the optical disc, and the signal reproduction of the optical disc is correctly performed.
In this case, the movement distance (from the innermost circumference to the inner side and the outermost circumference to the outer side) of the optical pickup 30 necessary for switching the aperture of the aperture means 31 is compared with that of the optical pickup 10 in FIG. It's short.
[0031]
8 and 9, the optical pickup 40, by an optical pickup 30 shown in FIGS. 6 and 7, instead of the protrusion 31c of the opening means 31, only one side edge, the protruding portion 31 d and the rocking A protrusion 31e is provided on the opposite side with respect to the moving center A. Correspondingly, an outer stopper 22 provided in the optical disc apparatus is disposed so as to be movable in the tangential direction of the optical disc. Except for these, the semiconductor laser element, beam splitter, rising mirror, objective lens, and photodetector in other configurations are the same as those of the optical pickup 10 in FIG.
[0032]
According to the optical pickup 40 having such a configuration, when reproducing an optical disk having a relatively thick disk substrate thickness of 1.2 mm, the outer stopper 22 is first provided with the protruding portion of the opening means 31 as shown in FIG. It is moved so as to be indicated by an arrow at a position corresponding to 31e. Then, the case of the optical pickup 30 is moved along the guide rail 20 from the outermost periphery of the optical disk to the outside, and the protruding portion 31 e of the opening means 31 comes into contact with the outer stopper 22. Thereby, the opening means 31 swings with respect to the case 32, and the opening 31 b is disposed in the optical path of the objective lens of the optical pickup 30.
[0033]
In this state, the optical pickup 30 reproduces the optical disc, and the aperture means 31 sets the numerical aperture appropriately. Therefore, the light beam is correctly imaged on the signal recording surface of the optical disc, and the signal reproduction of the optical disc is correctly performed.
[0034]
Next, in the case of reproducing an optical disk having a relatively thin disk substrate thickness of 0.6 mm, the case 32 of the optical pickup 30 first has the outer stopper 22 on the protrusion 31d of the opening means 31 as shown in FIG. While being moved to the corresponding position, the case of the optical pickup 30 is moved along the guide rail 20 to the outside from the outermost periphery of the optical disc, and the protruding portion 31 d of the opening means 31 contacts the outer stopper 22. Thereby, the opening means 31 swings with respect to the case 32, and the opening 31 a is disposed in the optical path of the objective lens of the optical pickup 30.
In this state, the optical pickup 30 reproduces the signal of the optical disc, and the aperture means 31 sets the numerical aperture appropriately. Therefore, the light beam is correctly imaged on the signal recording surface of the optical disc, and the signal reproduction of the optical disc is correctly performed.
[0035]
In this case, the movement distance of the optical pickup 30 (from the outermost periphery of the optical disk to the outside) required for switching the opening of the opening means 31 can be shorter than that of the optical pickup 10 of FIG. There is no need to move to the inside of the inner circumference. In the illustrated case, the projecting portions 31 d and 31 e of the opening means 31 are provided in the outer direction of the optical disc, but the present invention is not limited thereto, and may be provided in the inner direction of the optical disc. The inner stopper is movably disposed.
[0036]
Thus, according to the above-described embodiment, since the variable aperture means is provided between the light source and the optical disk, the numerical aperture of the variable aperture means depends on the disk substrate thickness of the optical disk to be reproduced. The spherical aberration is corrected by the adjustment. As a result, the light beam from the light source is correctly imaged on the signal recording surface of the optical disc through the variable aperture means, and the return light from the signal recording surface of the optical disc is incident on the photodetector so that it is always optimal. Signal reproduction is performed.
Accordingly, a plurality of types of optical discs having different disc substrate thicknesses are always reproduced correctly by one optical pickup and one optical disc reproducing apparatus equipped with this pickup.
[0037]
In the above embodiment, the opening means 16 and 31 are disposed between the rising mirror 13 and the objective lens 14 as shown in FIG. As long as it is disposed in the optical path between the semiconductor laser element 11 as the light source and the optical disc 17, for example, as shown in FIG. 10, it is disposed in the optical path between the beam splitter 12 and the rising mirror 13. It may be.
[0038]
Further, when the aperture means is disposed in the optical path between the optical disk and the beam splitter, both the light beam from the light source to the optical disk and the return light beam from the optical disk are narrowed by the aperture means. Become.
On the other hand, when the aperture means is disposed in the optical path between the beam splitter and the light source, only the light beam from the light source to the optical disk is narrowed down by the aperture means and from the optical disk. Since the return light beam does not pass through the aperture means, it is not narrowed down.
[0039]
Furthermore, in the above embodiment, for the optical disk having a disk substrate thickness of 1.2 mm and 0.6 mm, the light beam is changed by switching the openings 16a, 16b, 31a, 31b of the opening means 16, 31 respectively. An image is formed on the signal recording surface of an optical disk having a relatively thin disk substrate thickness and an optical disk having a relatively thick disk substrate thickness. However, the present invention is not limited to this. For example, a bonded optical disk in which two substrates are bonded together In addition, the present invention can be applied when reproducing a normal optical disc.
Further, each of the openings 16a, 16b, 31a, 31b of the opening means 16, 31 may be provided with a lens having an appropriate numerical aperture, and by switching or swinging the opening means 16, 31 at the time of opening switching. Obviously, the opening means may be retracted from the optical path.
[0040]
【The invention's effect】
As described above, according to the present invention, the optical disc is correctly played back regardless of the optical disc of any system. Further, since the opening means is swung around the support shaft and the opening means is switched, the moving distance of the optical pickup can be shortened.
[Brief description of the drawings]
FIG. 1 is a schematic side view showing a first embodiment of an optical pickup of a disc reproducing apparatus according to the present invention.
FIG. 2 is a schematic plan view of the optical pickup of FIG.
FIG. 3 is a schematic plan view showing aperture switching of the optical pickup in FIG. 1;
4 is a schematic plan view showing an aperture switching state inside the innermost circumference of the optical disc by the optical pickup of FIG. 1; FIG.
5 is a schematic plan view showing an aperture switching state outside the outermost circumference of the optical disk by the optical pickup of FIG. 1. FIG.
FIG. 6 is a schematic plan view showing a second embodiment of the optical pickup according to the present invention.
7 is a schematic plan view showing aperture switching in the optical pickup of FIG. 6. FIG.
FIG. 8 is a schematic perspective view showing a third embodiment of the optical pickup according to the present invention.
9 is a schematic plan view showing aperture switching in the optical pickup of FIG. 8. FIG.
FIG. 10 is a schematic side view showing a fourth embodiment of the optical pickup according to the present invention.
FIG. 11 is a schematic perspective view showing an example of a conventional optical pickup.
[Explanation of symbols]
10 Optical Pickup 11 Semiconductor Laser Element (Light Source)
12 beam splitter 13 rising mirror 14 objective lens 15 photodetector 16 opening means 16a, 16b opening 17 optical disk 18 biaxial actuator 19 case 20 guide rail 21 inner stopper 22 outer stopper 30 optical pickup 31 opening means 31a, 31b opening 31c, 31d, 31e Projection 32 Case

Claims (3)

A light source that emits a light beam;
An objective lens for irradiating a light beam emitted from the light source so as to be focused on a signal recording surface of a rotationally driven optical disc;
A light separating means disposed between the light source and the objective lens,
A photodetector for receiving a return light beam from the signal recording surface of the optical disk separated by the light separation means;
Opening means comprising a plate-like member provided in the optical path between the light source and the optical disc,
The opening means is
The plate-like member is rotatable about a support shaft as a swing center, and the plate-like member has two openings of different sizes separated from each other in the circumferential direction of the support shaft , and in the vicinity of the support shaft . of an inner edge or outer edge of the plate member, without the configuration with two collision detection section which is opposed to the inner circumferential side or outer circumferential side in the radial direction of the optical disc of the optical pickup,
The optical pickup said opening means is moved together with either one of the above two collision detection section is a movable in the tangential direction of and the optical disk is provided outside the inner or outermost from the innermost circumference of the optical disc Then, the aperture switching of the aperture means is performed by abutting against a stopper of the optical disc apparatus moved to a position corresponding to the two protrusions .   2. The disk reproduction according to claim 1, wherein the opening means includes an opening having a numerical aperture corresponding to a disk substrate thickness of an optical disk to be reproduced with respect to optical disks having different disk substrate thicknesses. apparatus.   2. The disk reproducing apparatus according to claim 1, wherein the opening means is switched when one opening is located in the optical path or the entire opening means is retracted from the optical path.

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