JP2010192032A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To narrow the interval between two objective lenses arranged in the radius direction of an optical disk, with respect to an optical pickup in which light is made incident on two objective lenses in one direction for reducing the thickness of the device. <P>SOLUTION: The optical pickup is provided with: two light sources 1, 9 compatible with different kinds of optical disks; two collimator lenses 3, 11 attached to a lens holder 17 compatible with each of the light sources 1, 9 and being movable in the optical axis direction; two objective lenses 5, 13 compatible with each of the light sources 1, 9; and an actuator with the objective lenses 5, 13 thereon. The lens holder 17 is regulated at at least two different positions in the direction orthogonal to the optical axis in accordance with a position of an optical axis direction. An optical axis center of one collimator lens corresponding to one light source is aligned with an optical axis coupling one light source and an objective lens corresponding to the light source in each of the positions, while an optical axis center of the other collimator lens corresponding to the other light source is separated from an optical axis coupling the other light source and an objective lens corresponding to the light source. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical pickup having two objective lenses and a collimator lens in order to cope with a plurality of types of optical disks.

  2. Description of the Related Art Conventionally, optical pickups for supporting optical discs with different standards such as BD (Blu-ray Disc), DVD (Degital Vastile Disc), and CD (Compact Disc) have been proposed. Such an optical pickup has a configuration corresponding to each optical disk by mounting two objective lenses on one actuator.

  Further, by forming a diffractive structure on the surface of one objective lens and utilizing the difference in wavelength of the light source, it is possible to cope with two standards of “DVD” and “CD” optical disks. Furthermore, in order to support three types of optical disks including “BD”, a configuration using an optical element different from the objective lens has been proposed.

  However, when an optical element different from the objective lens is used, there is a problem that the thickness of the optical pickup increases because the objective lens and the optical element need to be adjusted and assembled together.

  Therefore, an optical pickup has been proposed in which an objective lens for “BD” and an objective lens for “DVD” and “CD” are arranged in parallel, and each is configured as an independent optical system.

  As a direction in which the objective lenses are arranged in parallel, a configuration in which two objective lenses are arranged in the radial direction of the optical disc and a configuration in which the objective lenses are arranged in a substantially tangential direction of the recording track as described in Patent Document 1 are proposed. ing.

  In the case where two objective lenses are arranged in the radial direction of the optical disk, the tracking track tangent direction as seen from each objective lens does not change even when the optical pickup moves in the radial direction of the optical disk. As a signal detection method, a so-called “3-beam method” or “differential push-pull method” can be used.

  FIG. 4 is a plan view showing an optical system in a conventional optical pickup, in which two objective lenses are arranged in the radial direction of the optical disk.

  In the conventional optical pickup, as shown in FIG. 4, the light emitted from the semiconductor laser 101 that is the light source for “BD” is transmitted through the prism 102 that separates the forward path and the backward path, and is substantially parallel by the collimator lens 103. Is converted into a luminous flux. Here, the collimator lens 103 is movable in the optical axis direction in order to correct spherical aberration caused by the thickness error of the optical disk 106. The light that has passed through the collimator lens 103 is converted in its optical path by the mirror 104 and condensed on the signal recording surface of the BD 106A by the objective lens 105. The light reflected by the BD 106A passes through the optical path opposite to the forward path, is reflected by the prism 102, enters the photodetector 108 through the lens 107 for detecting the tracking error signal and the focus error signal. By detecting the light incident on the photodetector 108, it is possible to execute focus servo and tracking servo for recording on the signal recording surface of the BD 106A or reproducing the signal recording surface of the BD 106A and causing the objective lens 105 to follow the BD 106A.

  The light emitted from the semiconductor laser 109, which is a light source for “DVD” and “CD”, passes through the prism 110 that divides the forward path and the return path, and is collimated by the collimator lens 111 for “DVD” and “CD”. It is converted into a substantially parallel light beam. The light that has become substantially parallel by the collimator lens 111 is converted in its optical path by the mirror 112 and is condensed by the objective lens 113 on the signal recording surface of the DVD 106B or CD 106C.

  The light reflected by the DVD 106B or the CD 106C passes through the optical path opposite to the forward path, is reflected by the prism 110, passes through the lens 114 for detecting the tracking error signal and the focus error signal, and enters the photodetector 115. As in the case of “BD”, the focus servo and the tracking servo for recording the DVD 106B or CD 106C on the signal recording surface or reproducing the signal recording surface of the DVD 106B or CD 106C and causing the objective lens 105 to follow the DVD 106B or CD 106C are executed. Is done.

  When the objective lens is arranged in the substantially tangential direction of the recording track, when the optical pickup moves in the radial direction of the optical disk, one objective lens can be arranged at a position where the tangential direction of the recording track does not change. At the position of the other objective lens, the angle in the tangential direction of the recording track changes due to the movement of the optical pickup. Therefore, the “3-beam method” or the “differential push-pull method” cannot be used as a tracking error signal detection method. Therefore, as described in Patent Document 2, a new detection method has been proposed in which one beam of detection light is divided by a hologram to cancel an error signal offset due to lens shift.

JP-A-2005-293686 JP 2006-120306 A

  Incidentally, in the optical pickup in which two objective lenses are arranged in the radial direction of the optical disk as shown in FIG. 4, the optical path from the “BD” prism 102 to the mirror 104 and the “DVD” and “CD” prism 110 are arranged. The optical path from the mirror 112 to the mirror 112 is arranged in parallel. In this optical pickup, the outer diameter of the “BD” collimator lens 103 is a size obtained by adding an allowance when the objective lens 105 is shifted in the tracking direction to the effective luminous flux diameter of the objective lens 105 for “BD”. Need. Further, the outer diameter of the collimator lens 111 for “DVD” and “CD” is a margin when the objective lens 112 is shifted in the tracking direction to the effective beam diameter of the objective lens 111 for “DVD” and “CD”. Necessary size is required. That is, the outer diameter of the collimator lenses 103 and 111 needs to be larger than the outer diameter of the objective lenses 105 and 113.

  In general, the shift amount of the objective lenses 105 and 113 is about 0.3 mm to 0.4 mm on one side. This is because in addition to following the eccentricity of the optical disk 106, when the optical pickup moves in the radial direction of the optical disk 106, the servo does not become unstable even if the movable part of the actuator moves due to inertia. Required value.

  Further, the “BD” collimator lens 103 needs to be movable in the optical axis direction in order to correct aberration due to a thickness error of the optical disk 106. Therefore, a structure for holding the collimator lens 103 so as to be movable is required.

  Due to these restrictions, when the optical systems corresponding to the two objective lenses 105 and 113 are arranged in parallel, the distance between the two optical paths for “BD” and “DVD” and “CD” is the distance between the collimator lenses 103 and 111. It is determined by the outer diameter and the holding mechanism, and it is difficult to reduce the distance between the two objective lenses 105 and 113.

  In this optical pickup, each objective lens 105 and 113 needs to move from the innermost circumference to the outermost circumference of the corresponding optical disk 106. The objective lens 105 located outside the objective lens 112 as viewed from the center of the optical disk 106 needs to be able to move to the innermost circumference of the optical disk 106. At this time, the inner objective lens 113 is further positioned closer to the center of the optical disk 106. End up. There is a spindle motor that rotates the optical disk 106 at the center of the optical disk 106, and interference between the spindle motor and the optical pickup must be avoided.

  However, the position of the inner objective lens 113 is determined by the outer diameters of the two objective lenses 105 and 113 to be used and the position of the innermost circumference of the optical disk 106 corresponding to the outer objective lens 105. The outer shape and height are almost determined by the size of the magnetic circuit that generates the torque necessary to rotate the optical disk 106. For this reason, it is difficult to avoid interference between the spindle motor and the optical pickup.

  Here, it is possible to arrange the two optical systems in different directions. However, in order to reduce the thickness of the entire optical disk device including the optical pickup, the actuator and the optical system need to be configured so as not to overlap in the thickness direction, and the direction of the optical path incident on the objective lenses 105 and 113 is determined. You will be limited to one direction.

  Therefore, the present invention is proposed in view of the above situation, and is an optical pickup in which the direction of the optical path incident on two objective lenses is one direction in order to correspond to a thin optical disk device, An object of the present invention is to provide an optical pickup capable of narrowing the interval between two objective lenses arranged in the radial direction (radial direction) of an optical disc.

  In order to solve the above problems and achieve the above object, an optical pickup according to the present invention has the following configuration.

[Configuration 1]
A first light source, a second light source having a wavelength different from that of the first light source, a first collimator lens that converts light emitted from the first light source into substantially parallel light, and emission from the second light source A second collimator lens that converts the emitted light into substantially parallel light, a lens holder in which the first collimator lens and the second collimator lens are integrally attached to be movable in the optical axis direction, and a first collimator lens. The lens holder includes a first objective lens that collects the transmitted light and a second objective lens that collects the light transmitted through the second collimator lens. The position in the direction orthogonal to the axis is restricted to at least the first position and the second position, and at the first position, on the optical axis connecting the first light source and the first objective lens, While matching the optical axis center of the collimator lens The optical axis center of the second collimator lens is separated from the optical axis connecting the second light source and the second objective lens, and the light connecting the second light source and the second objective lens at the second position. The optical axis center of the second collimator lens coincides with the axis, and the optical axis center of the first collimator lens is separated from the optical axis connecting the first light source and the first objective lens. It is what.

[Configuration 2]
In the optical pickup having the configuration 1, when the second objective lens is positioned on the inner peripheral side of the first objective lens with respect to the optical disc recorded or reproduced by the first or second objective lens, the first position is set. 2, the optical axis center of the second collimator lens is separated from the optical axis connecting the second light source and the second objective lens toward the inner circumference side with respect to the optical disc, and the first collimator is located at the second position. The center of the optical axis of the lens is separated from the optical axis connecting the first light source and the first objective lens toward the outer peripheral side with respect to the optical disc.

  In the optical pickup according to the present invention, by having the configuration 1, the position of the lens holder in the direction orthogonal to the optical axis is restricted to at least the first position and the second position according to the position in the optical axis direction. The optical axis center of the first collimator lens coincides with the optical axis connecting the first light source and the first objective lens at the first position, and the optical axis center of the second collimator lens is set to the second axis. The optical axis center of the second collimator lens is made to coincide with the optical axis connecting the second light source and the second objective lens at the second position away from the optical axis connecting the light source and the second objective lens. In addition, since the center of the optical axis of the first collimator lens is separated from the optical axis connecting the first light source and the first objective lens, the distance between the two optical paths corresponding to the two collimator lenses and the two objectives. Between the center of the lens The interval may be narrower than the distance between the center of each of the collimator lenses. In this optical pickup, since two objective lenses are mounted on one actuator, the two objective lenses can be disposed close to each other, and the actuator and the optical pickup as a whole are reduced in thickness and size. It is possible.

In addition, in the optical pickup according to the present invention, the second objective lens has the configuration 2 so that the second objective lens has an inner circumference with respect to the optical disc recorded or reproduced by the first or second objective lens. The optical axis center of the second collimator lens is separated from the optical axis connecting the second light source and the second objective lens toward the inner peripheral side with respect to the optical disc at the first position. At the position 2, the center of the optical axis of the first collimator lens is separated from the optical axis connecting the first light source and the first objective lens toward the outer periphery side with respect to the optical disc.
Therefore, even when this optical pickup is moved to the innermost circumference of the optical disk, a sufficient distance from the spindle motor can be secured. Therefore, it is possible to use a spindle motor having a large outer diameter because it has been thinned while sufficiently securing driving torque.

  That is, the present invention is an optical pickup in which the direction of an optical path incident on two objective lenses is one direction in order to correspond to a thin apparatus, and the two objective lenses are arranged in the radial direction (radial direction) of the optical disc. It is possible to provide an optical pickup capable of narrowing the interval.

It is a top view which shows the structure of the optical pick-up based on this invention. It is a block diagram which shows the Example of this invention. It is a block diagram which shows the Example of this invention. It is an optical system in a conventional optical pickup, and is a plan view showing a configuration in which two objective lenses are arranged in the radial direction of an optical disc.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1A is a plan view showing a configuration of an optical pickup when “BD” according to the present invention is recorded or reproduced (initial state). FIG. 1B is a plan view showing a configuration of an optical pickup when “DVD” or “CD” according to the present invention is recorded or reproduced. 1A and 1B differ in the position of the lens holder 17 in the optical axis direction.

  In the optical pickup according to the present invention, light having a wavelength of 405 nm emitted from the semiconductor laser 1 which is a light source for “BD” is transmitted through the prism 2 that separates the forward path and the return path, and is converted into a substantially parallel light beam by the collimator lens 3. Converted. The collimator lens 3 is at a position P3 as shown in FIG. The light that has been made substantially parallel by the collimator lens 3 is converted in its optical path by the mirror 4 and condensed on the signal recording surface of the BD 6A by the objective lens 5.

  The light reflected by the BD 6A passes through the optical path opposite to the forward path, is reflected by the prism 2, passes through the lens 7 for detecting the focus error signal and the tracking error signal, and enters the photodetector 8. By detecting the light incident on the photodetector 8, recording on the signal recording surface of the BD 6A or reproduction of the signal recording surface of the BD 6A, and focus servo and tracking servo for causing the objective lens 5 to follow the BD 6A are executed.

  Further, light having a wavelength of 650 nm or 780 nm emitted from the semiconductor laser 9 which is a light source for “DVD” and “CD” is transmitted through the prism 10 that divides the forward path and the return path, and is used for “DVD” and “CD”. The collimator lens 11 converts the light into a substantially parallel light beam. The collimator lens 11 is at a position P4 as shown in FIG. In this embodiment, the semiconductor laser 9 uses a so-called two-wavelength LD in which two light sources for “DVD” and “CD” are combined into one package, but separate light sources may be used.

  The light that has been made substantially parallel by the collimator lens 11 has its optical path converted by the mirror 12 and condensed by the objective lens 13 on the signal recording surface of the DVD 6B or CD 6C. The light reflected by the DVD 6B or CD 6C passes through the optical path opposite to the forward path, is reflected by the prism 10, and enters the photodetector 15 through the lens 14 for detecting the focus error signal and tracking error signal. As a result, similarly to “BD”, focus servo and tracking servo are executed for recording on the signal recording surface of DVD6B or CD6C or reproducing DVD6B or CD6C and causing the objective lens 13 to follow DVD6B or CD6C.

  In this optical pickup, the optical path from the “BD” prism 2 to the mirror 4 and the optical path from the “DVD” and “CD” prism 10 to the mirror 12 are arranged in parallel.

  The outer diameter of the “BD” collimator lens 3 needs to have a size that takes into account the effective light beam diameter of the objective lens 5 for “BD” and a margin when the objective lens 5 is shifted in the tracking direction. Further, the outer diameter of the collimator lens 11 for “DVD” and “CD” is a margin when the objective lens 13 is shifted in the tracking direction to the effective beam diameter of the objective lens 13 for “DVD” and “CD”. Necessary size is required. The amount of shift in the tracking direction of the objective lenses 5 and 13 is generally about 0.3 mm to 0.4 mm on one side. This is necessary not only to follow the eccentricity of the optical disc 6 but also to prevent the servo from becoming unstable even if the movable part of the actuator moves due to inertia when the optical pickup moves in the radial direction of the optical disc 6. Value.

  In this optical pickup, the collimator lens 3 for “BD” and the collimator lens 11 for “DVD” and “CD” are integrally attached to a lens holder 17 movable in the optical axis direction. The lens holder 17 to which the collimator lenses 3 and 11 are integrally attached can be moved in the optical axis direction. A stepping motor 20 or the like is used as a mechanism for moving the lens holder 17. By moving the lens holder 17 to move the collimator lens 3 in the optical axis direction, it is possible to correct spherical aberration caused by a thickness error or temperature error of the optical disc 6 including the BD 6A.

  Further, the lens holder 17 does not always move linearly when moved by the stepping motor 20. Depending on the position of the lens holder 17, a range where the optical axis center of the “BD” collimator lens 3 coincides with the optical axis connecting the semiconductor laser 1 for “BD” and the objective lens 5, “DVD” and “ There is a range in which the optical axis center of the collimator lens 11 for “CD” coincides with the optical axis connecting the semiconductor laser 9 for “DVD” and “CD” and the objective lens 13.

  For example, the position of the lens holder 17 in the initial state is at an intermediate position P3 between the position P1 and the position P2. When the lens holder 17 is at the position P 3, the light emitted from the “BD” semiconductor laser 1 is made into substantially parallel light by the collimator lens 3. Further, when recording or reproduction is performed on the BD 6A, the collimator lens 3 attached to the lens holder 17 is moved within the range of the positions P1 and P2 shown in FIG. 2, and the thickness error of the optical disc 6 is within this range. It is possible to correct spherical aberration generated by the above. At this time, the center of the optical axis of the collimator lens 3 for “BD” coincides with the optical axis connecting the semiconductor laser 1 for “BD” and the objective lens 5, while for “DVD” and “CD”. The center of the optical axis of the collimator lens 11 is shifted to the inner peripheral side of the optical disk 6 from the optical axis connecting the semiconductor laser 9 for “DVD” and “CD” and the objective lens 13.

  Further, when recording or reproduction is performed on the DVD 6B or CD 6C, the collimator lens 11 is moved from the position P3 in the initial state for “BD” to the position P4. At this time, the center of the optical axis of the collimator lens 11 for “DVD” and “CD” coincides with the optical axis connecting the semiconductor laser 9 for “DVD” and “CD” and the objective lens 13, The optical axis center of the “BD” collimator lens 3 is shifted to the outer peripheral side of the optical disc 6 with respect to the optical axis connecting the “BD” semiconductor laser 1 and the objective lens 5.

  Thus, in this optical pickup, the collimator lens 3 for “BD” and the collimator lens 11 for “DVD” and “CD” are integrally mounted on the lens holder 17. , The distance between the two objective lenses 5 and 13 can be made narrower than the distance between the two collimator lenses 3 and 11. In particular, when recording or reproduction is performed on the BD 6A, the light that connects the optical axis center of the collimator lens 11 for “DVD” and “CD” with the semiconductor laser 9 for “DVD” and “CD” and the objective lens 13 is used. When the optical disc 6 is separated from the axis toward the inner peripheral side of the optical disc 6 and recording or reproduction is performed on the DVD 6B or CD 6C, the center of the optical axis of the collimator lens 11 for "BD" The distance between the two objective lenses 5 and 13 can be made narrower by separating them from the optical axis connecting the lens 13 to the outer peripheral side of the optical disc 6. By narrowing the distance between the two objective lenses 5 and 13, the required distance for the optical pickup to move from the innermost periphery to the outermost periphery of the optical disk 6 can be reduced. When the optical pickup is moved to the innermost circumference of the optical disc 6, a sufficient gap between a spindle motor (not shown) and the inner objective lens 13 can be secured. Therefore, even in a thin optical disc apparatus, each objective lens 5, 13 can be arranged side by side in the radial direction (radial direction) of the optical disk 6.

  FIG. 2 is a perspective view showing a configuration of a collimator lens moving mechanism in the optical pickup according to the present invention.

  In the optical pickup according to the present invention, the mechanism for moving the collimator lenses 3 and 11 includes a collimator lens 3 for "BD" and a collimator lens 11 for "DVD" and "CD" as shown in FIG. The lens holder 17 to which is attached is disposed such that its position in the height direction is regulated by two shafts 19a and 19b provided in the housing. The lens holder 17 can be moved in the optical axis direction by a stepping motor 20. The lens holder 17 and the drive shaft of the stepping motor 20 are coupled by the coupling unit 22, and the driving force of the stepping motor 20 is transmitted to the lens holder 17. The coupling portion 22 is made of an elastic member such as a spring, and the boss is always in contact with one side of the guide groove of the driving force of the stepping motor 20, and rattling is caused when moving in the optical axis direction. Does not occur.

  3A and 3B are a plan view and a front view showing the configuration of the collimator lens moving mechanism in the optical pickup according to the present invention.

  As shown in FIG. 3, the lens holder 17 is provided with a boss 21a for regulating the position in a direction orthogonal to the optical axis. The boss 21 a is inserted into a guide groove 21 b provided in the housing, and regulates the position of the lens holder 17 in the direction orthogonal to the optical axis.

  When recording or reproduction is performed on the BD 6A, the lens holder 17 moves in the optical axis direction within the range of the positions P1 and P2. At this position, the optical axis center of the “BD” collimator lens 3 coincides with the optical axis connecting the “BD” semiconductor laser 1 and the objective lens 5. At this time, it is possible to correct spherical aberration caused by the thickness error or temperature error of the optical disk.

  When performing recording or reproduction on the DVD 6B or CD 6C, the lens holder 17 is moved to the position P4. At this time, the center of the optical axis of the collimator lens 11 for “DVD” and “CD” coincides with the optical axis connecting the semiconductor laser 9 for “DVD” and “CD” and the objective lens 13.

  In this embodiment, the stepping motor 20 is used as the moving mechanism of the lens holder 17, but the moving mechanism is not limited to this, and various moving means such as a DC motor and a piezo element are used. Can be used. Moreover, although the example using the boss | hub and the guide groove is shown as a positioning mechanism of the lens holder 17, it is good also as a mechanism which carries out position regulation with the other mechanism, for example, the side surface of the lens holder 17. FIG.

  The present invention is applied to an optical pickup having two objective lenses and a collimator lens in order to cope with a plurality of types of optical disks.

DESCRIPTION OF SYMBOLS 1 "BD" semiconductor laser 3 "BD" collimator lens 5 "BD" objective lens 6 Optical disk 9 "DVD" and "CD" semiconductor laser 11 "DVD" and "CD" collimator lens 13 "DVD" and Objective lens for “CD” 17 Lens holder

Claims (2)

A first light source;
A second light source having a wavelength different from that of the first light source;
A first collimator lens that converts light emitted from the first light source into substantially parallel light;
A second collimator lens that converts light emitted from the second light source into substantially parallel light;
A lens holder in which the first collimator lens and the second collimator lens are integrally attached to be movable in the optical axis direction;
A first objective lens for condensing the light transmitted through the first collimator lens;
A second objective lens that condenses the light transmitted through the second collimator lens,
The position of the lens holder in a direction orthogonal to the optical axis is restricted to at least a first position and a second position according to a position in the optical axis direction, and the first light source is at the first position. And the optical axis center of the first collimator lens on the optical axis connecting the first objective lens and the first objective lens, and the optical axis center of the second collimator lens is aligned with the second light source and the first objective lens. The optical axis center of the second collimator lens is separated from the optical axis connecting the second objective lens and on the optical axis connecting the second light source and the second objective lens at the second position. And an optical axis center of the first collimator lens is separated from an optical axis connecting the first light source and the first objective lens. When the second objective lens is positioned on the inner peripheral side of the first objective lens with respect to the optical disk to be recorded or reproduced by the first or second objective lens, The center of the optical axis of the second collimator lens is separated from the optical axis connecting the second light source and the second objective lens toward the inner peripheral side with respect to the optical disc, and at the second position, 2. The optical pickup according to claim 1, wherein an optical axis center of one collimator lens is separated from an optical axis connecting the first light source and the first objective lens toward an outer peripheral side with respect to the optical disk. .

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