JP2005353134A - Optical pickup and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain miniaturization and cost-saving, and also to prevent optical aberration from being caused by temperature gradient of an objective lens without sacrificing responsiveness. <P>SOLUTION: An inner circumferential part 2006 of a lens holder 2 is constituted by alternately arranging two or more abutment faces 2008 which abut on an outer circumferential surface 7002 of the objective lens 7 and two or more non-abutment faces 2010 facing the outer circumferential face 7002 of the objective lens 7 via a space 2009 in the circumferential direction of the inner circumferential part 2006. The objective lens 7 is attached to a recessed part 2002, in the state in which the outer circumferential face abuts on a plurality of abutment faces 2008, and the space 2009 is secured among a plurality of non-abutment faces 2010. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus for recording and reproducing signals on an optical disc and an optical pickup used in the optical disc apparatus.

There is an optical pickup that irradiates a light beam onto an optical disk such as a CD (Compact Disk) or a DVD (Digital Versatile Disk) to record or reproduce a signal or perform recording and reproduction.
Such an optical pickup includes a lens holder that holds an objective lens, and the lens holder is provided with a focus coil and a tracking coil that move the lens holder in a focus direction and a tracking direction.
On the other hand, in recent years, with the increase in recording density of optical discs, the wavelength of light beams has been shortened and the NA of numerical objectives has been increased. In addition, a plastic lens is increasingly used as an objective lens for reasons of ease of molding and cost reduction compared to a glass lens.
By the way, a plastic lens is easily deformed by a temperature change, and when the temperature distribution of the plastic lens is biased, in other words, when a temperature gradient is generated, the plastic lens is easily distorted and various optical aberrations are likely to occur.
Therefore, when a plastic lens is used as the objective lens, these coils generate heat due to the current flowing through the focus coil and tracking coil, and the heat is transmitted to the objective lens through the lens holder, causing optical aberration due to the temperature gradient. There is a problem in that the servo characteristics in the optical pickup and the quality of the reproduced signal are deteriorated.
In order to avoid such a problem, an annular member made of a material having high thermal conductivity is interposed between the objective lens and the lens holder, and the heat of the lens holder is made uniform by the annular member and transmitted to the objective lens. Thus, there has been proposed an optical pickup that suppresses the occurrence of a temperature gradient in the objective lens (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-176209

However, in the optical pickup, since the lens holder is provided with the annular member, the number of parts is increased, which is disadvantageous in reducing the size and cost of the optical pickup, and the weight of the lens holder is increased. It is also disadvantageous to improve the responsiveness.
The present invention has been made in view of such circumstances, and its purpose is to reduce the size and cost, and to prevent the occurrence of optical aberration due to the temperature gradient of the objective lens without sacrificing responsiveness. It is an object of the present invention to provide an optical pickup and an optical disk apparatus that are advantageous.

To achieve the above object, the present invention provides a lens holder for holding an objective lens, and the lens holder is moved in a focus direction, which is an optical axis direction of the objective lens, by supplying a current to the lens holder. An optical pickup comprising: a focus coil to be moved; and a tracking coil that is provided in the lens holder and moves the lens holder in a tracking direction orthogonal to the focus direction when current is supplied to the lens holder, A concave portion for accommodating the objective lens, the concave portion including an inner peripheral portion having a diameter corresponding to the outer peripheral surface of the objective lens, the inner peripheral portion being capable of contacting the outer peripheral surface of the objective lens; A plurality of contact surfaces and a plurality of non-contact surfaces facing the outer peripheral surface of the objective lens through a space intersect along the circumferential direction of the inner peripheral portion. The objective lens has an outer peripheral surface that is in contact with the plurality of contact surfaces, and the space is secured between the plurality of non-contact surfaces. It is attached.
The present invention also provides a driving means for holding and rotating the optical disk, and a recording and / or reproducing light beam applied to the optical disk rotated and driven by the driving means, and the light of the irradiated light beam. An optical disc apparatus having an optical pickup for detecting a reflected light beam by reflected light from a recording medium, wherein the optical pickup is provided with a lens holder for holding an objective lens, and provided with an electric current. The focus coil that moves the lens holder in the focus direction, which is the optical axis direction of the objective lens, and the lens holder is moved in the tracking direction orthogonal to the focus direction by being supplied with current. And a tracking coil for accommodating the objective lens The concave portion includes an inner peripheral portion having a diameter corresponding to the outer peripheral surface of the objective lens, and the inner peripheral portion includes a plurality of contact portions that can contact the outer peripheral surface of the objective lens. A contact surface and a plurality of non-contact surfaces facing the outer peripheral surface of the objective lens through a space are alternately arranged along the circumferential direction of the inner peripheral portion, and the objective lens Is in contact with the plurality of contact surfaces, and is attached to the recess with the space secured between the plurality of non-contact surfaces.

According to the present invention, a plurality of spaces are interposed between the outer peripheral surface of the objective lens and the inner peripheral portion of the lens holder via the non-contact surface. Therefore, conduction of heat generated by the current flowing through the tracking coil and the focus coil to the objective lens is performed through a plurality of contact surfaces, but it is extremely small because there are a plurality of non-contact surfaces. Become.
From this, by arranging a plurality of contact surfaces and a plurality of non-contact surfaces as appropriate, heat conducted from the focus coil and tracking coil to the outer periphery of the objective lens through the lens holder is spread over the entire outer periphery. It becomes possible to make it substantially uniform.
Therefore, each of the temperatures of the objective lens portions located on the circumference of the same radius centered on the optical axis of the objective lens changes with a similar temperature gradient outward in the radial direction over the entire circumference of the objective lens. Thus, the temperature gradient at the objective lens portion located on the circumference of the same radius can be made substantially zero.
In this way, if the temperature gradient at the objective lens portion located on the circumference of the same radius of the objective lens is almost zero, coma and astigmatism as optical aberrations generated in the objective lens will be very small and ignored. Only spherical aberrations need to be considered. Such spherical aberration can be easily corrected by the optical system of the optical pickup.
For this reason, it is possible to suppress the occurrence of a temperature gradient in the objective lens without interposing an annular member made of a material having a high thermal conductivity as in the past, between the objective lens and the lens holder. The number of points can be reduced, which is advantageous in reducing the size and cost of the optical pickup, and the lens holder can be reduced in weight, which is advantageous in improving the response of the optical pickup.

  An object of the present invention is to reduce the size and cost and to prevent the occurrence of optical aberration due to the temperature gradient of the objective lens without sacrificing responsiveness. This was realized by interposing a plurality of spaces with non-contact surfaces between the inner peripheral portion and the inner peripheral portion.

Embodiments of an optical pickup and a recording / reproducing apparatus according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of an optical disc apparatus incorporating an optical pickup according to Embodiment 1 of the present invention.

  In FIG. 1, an optical disk device 101 includes a spindle motor 103 as a driving means for rotating and driving an optical disk 102 as an optical recording medium such as a CD-R, a DVD ± R, a DVD-RAM, and a Blu-ray disk, and an optical pickup 104. And a feed motor 105 as drive means for moving the optical pickup 104 in the radial direction. Here, the spindle motor 103 is configured to be driven and controlled at a predetermined rotational speed by the system controller 107 and the servo control unit 109.

The signal modulation / demodulation unit and ECC block 108 modulates and demodulates a signal output from the signal processing unit 120 and adds an ECC (error correction code). The optical pickup 104 irradiates the signal recording surface of the optical disk 102 that rotates according to instructions from the system controller 107 and the servo control unit 109 with a light beam. Recording and reproduction of an optical signal with respect to the optical disc 102 is performed by such light irradiation.
Further, the optical pickup 104 can detect various light beams as will be described later based on the reflected light beam from the signal recording surface of the optical disc 102 and supply a signal corresponding to each light beam to the signal processing unit 120. It is configured.

The signal processing unit 120 is a servo control signal based on a detection signal corresponding to each light beam, that is, a focus error signal, a tracking error signal, an RF signal, and an ATIP necessary for controlling the rotation of the optical disc during recording. A signal or the like can be generated. Further, predetermined processing such as demodulation and error correction processing based on these signals is performed by the servo control unit 109, the signal modulation and ECC block 108, and the like according to the type of recording medium to be reproduced.
Here, if the recording signal demodulated by the signal modulation and ECC block 108 is, for example, for data storage of a computer, it is sent to the external computer 130 or the like via the interface 111. Accordingly, the external computer 130 and the like are configured to receive a signal recorded on the optical disc 102 as a reproduction signal.

Also, if the recording signal demodulated by the signal modulation and ECC block 108 is for audio / visual use, the digital / analog conversion is performed by the D / A conversion unit of the D / A and A / D converter 112 for audio / visual processing. Supplied to the unit 113. Audio / video signal processing is performed by the audio / visual processing unit 113 and transmitted to an external imaging / projection device via the audio / visual signal input / output unit 114.
A feed motor 105 is connected to the optical pickup 104, and the optical pickup 104 is moved to a predetermined recording track on the optical disk 102 by the rotation of the feed motor 105. Control of the spindle motor 103, control of the feed motor 105, and control of the focusing direction and tracking direction of the actuator holding the objective lens of the optical pickup 104 are performed by a servo control unit 109, respectively.
That is, the servo control unit 109 controls the spindle motor 103 based on the ATIP signal, and controls the actuator based on the focus error signal and the tracking error signal.
The servo control unit 109 also includes one focus coil 20 (see FIG. 2) and four tracking coils 30 (described later) based on the focus error signal, tracking error signal, RF signal, and the like input from the signal processing unit 120. A driving signal (driving current) to be supplied to each other is generated.
The laser control unit 121 controls the laser light source in the optical pickup 104.

  Here, the focus direction Z refers to the optical axis direction of the objective lens 7 (see FIG. 2) of the optical pickup 104, and the tracking direction X refers to the direction orthogonal to the focus direction Z (the radial direction of the optical disk 101). The local direction Y is a direction (tangential direction of the circumference of the optical disc 101) perpendicular to both the focus direction Z and the tracking direction X.

Next, the optical pickup 104 will be described in detail.
2 is a perspective view of the optical pickup according to the first embodiment of the present invention, FIG. 3 is a plan view of the optical pickup according to the first embodiment, FIG. 4 is a cross-sectional view taken along line AA in FIG. 3, and FIG. 6 is a cross-sectional view taken along line CC of FIG. 2, FIG. 7 is an exploded perspective view showing a state where the yoke base is removed from the optical pickup, and FIG. 8 is an assembly view showing a state where the yoke base is removed from the optical pickup.

The optical pickup 104 guides the light from the semiconductor laser as a light source that emits light, a photodiode as a light detection element that detects a reflected light beam from the signal recording surface of the optical disk 102, and the light from the semiconductor laser to the optical disk 101. And an optical system for guiding the reflected light beam to the light detection element.
As shown in FIG. 2, the optical pickup 104 is provided on a mount member 60 provided so as to be movable in the radial direction of the optical disc 101 within the housing of the optical disc apparatus 100.
The optical pickup 104 includes a lens holder 2 that holds an objective lens 7 that condenses the light beam emitted from the light source and irradiates the optical disc, and a mount member that is disposed at an interval in the tangential direction Y from the lens holder 2. A support block 3 attached to 60 and a suspension wire 80 connecting the lens holder 2 and the support block 3 are provided. The objective lens 7 constitutes a part of the optical system of the optical pickup 104.
On both sides of the lens holder 2 in the tracking direction X, two wire support portions 8 are provided at intervals in the focus direction Z, respectively.

As shown in FIGS. 2 and 3, the support block 3 has a length along the tracking direction X and a height along the focus direction Z.
On both sides of the support block 3 along the tracking direction X, two wire support portions 14 are provided at intervals in the focus direction Z, respectively.
A total of four suspension wires 80 are provided, and two wire support portions 8 on both sides in the tracking direction X of the lens holder 2 and two wire support portions 14 on both sides in the tracking direction X of the support block 3 are each two. The suspension wires 80 are connected.
The two suspension wires 80 are provided in parallel to each other with a gap in the focus direction Z, and support the lens holder 2 with respect to the support block 3 so as to be movable in the focus direction Z and the tracking direction X.
Each of these suspension wires 80 is made of a material having conductivity and elasticity.
The end of each suspension wire 80 on the support block 3 side is connected to the servo control unit 109 via a wiring member (not shown), and a focus drive signal and a tracking drive signal are received from the servo control unit 109. It is configured to be supplied.

As shown in FIGS. 2 and 3, a yoke base 18 is provided at a position between the lens holder 2 and the support block 3 and the mount member 60 in the focus direction Z. The yoke base 18 is attached to the mount member 60, the support block 3 is attached to the yoke base 18, and the yoke base 18 is provided with an opening 1802 at a portion through which the optical axis of the objective lens 7 passes.
A pair of yoke pieces 18a are erected on both sides of the yoke base 18 in the tangential direction Y, and the surfaces of the yoke pieces 18a facing each other face both ends of the lens holder 2 in the tangential direction Y. In addition, a single rectangular plate-shaped magnet 19 is attached with its thickness direction facing the tangential direction Y.
Further, on both sides of the pair of yoke pieces 18a in the tracking direction X, yoke end portions 18b bent in a direction close to the opposing yoke pieces 18a are provided, and one yoke piece 18a of the two yoke pieces 18a. The end surface of each yoke end portion 18b and the end surface of each yoke end portion 18b of the other yoke piece 18a are opposed to each other.
The end face of each yoke end 18b of one yoke piece 18a and the surface of the magnet 19 attached to this one yoke 18a that faces the lens holder 2 are configured to be substantially flush with each other. Similarly, the end face of each yoke end 18b of the other yoke piece 18a and the surface of the magnet 19 attached to the other yoke piece 18a that faces the lens holder 2 are arranged on substantially the same plane. Has been.

As shown in FIG. 7, in this embodiment, the objective lens 7 is configured by joining two plastic lenses superposed in the optical axis direction, and has a flat cylindrical shape as a whole. In this embodiment, the NA of the objective lens 7 is 0.85 corresponding to, for example, a Blu-ray disc and corresponds to a light beam having a wavelength of 405 nm.
The lens holder 2 has a rectangular plate shape and has a recess 2002 that accommodates the objective lens 7, and an opening 2004 is provided at the bottom of the recess 2002 at a portion through which the optical axis of the objective lens 7 passes.
As shown in FIGS. 2 and 6, one focus coil 20 is wound around the outer periphery of the lens holder 2.
The focus coil 20 has a coil surface orthogonal to the winding axis of the coil constituting the focus coil 20, and is provided so that this coil surface faces the focus direction Z.
As shown in FIGS. 3 and 6, two tracking coils 30 are attached to both ends of the lens holder 2 in the tangential direction Y and at both ends in the tracking direction X with an interval in the tracking direction X, respectively. In total, four tracking coils 30 are provided.
Each tracking coil 30 has a coil surface 3002 orthogonal to the winding axis of the coil constituting the tracking coil 30.
When viewed from the optical axis direction of the objective lens 7, the coil surfaces 3002 of the two tracking coils 30 attached to one end surface of the lens holder 2 in the tangential direction Y among the four tracking coils 30 are the tanger. Coils of two tracking coils 30 that face both the yoke ends 18b of one yoke piece 18a in the tangential direction Y and the surface of the magnet 19 and are attached to the other end face of the lens holder 2 in the tangential direction Y. The surface 3002 faces both the yoke end portions 18b of the other yoke piece 18a and the surface of the magnet 19 in the tangential direction Y.
In this embodiment, as shown in FIG. 6, when viewed from the optical axis direction of the objective lens 7, each tracking coil 30 is located on the inner side of the contour of the lens holder 2 in the tracking direction X. It has a coil portion 3004 and an outer coil portion 3006 located at a location outside the contour of the lens holder 2 in the tracking direction X.
The focus coil 20 and each tracking coil 30 are electrically connected to the ends of the four suspension wires 80 on the lens holder 2 side, and the focus drive signal is connected to the two focus coils 20 via the suspension wires 80. Are individually supplied, and the tracking drive signal is commonly supplied to each tracking coil 30 via a suspension wire 80.

The lens holder 2 will be described in detail. As shown in FIGS. 3 to 8, the recess 2002 is formed at the center of the lens holder 2, and the recess 2002 has an inner peripheral portion having a diameter corresponding to the outer peripheral surface 7002 of the objective lens 7. 2006 is comprised.
The inner peripheral portion 2006 includes a plurality of contact surfaces 2008 that can contact the outer peripheral surface 7002 of the objective lens 7 and a plurality of non-contact surfaces 2010 that face the outer peripheral surface 7002 of the objective lens 7 through a space 2009. In the present embodiment, four contact surfaces 2008 and four non-contact surfaces 2010 are provided, and the four contact surfaces 2008 are formed by alternately arranging the peripheral portions 2006 along the circumferential direction. The lens holder 2 is provided at each of the inner peripheral portions 2006 corresponding to the four corners.
The objective lens 7 is attached to the recess 2002 with its outer peripheral surface 7002 in contact with a plurality of contact surfaces 2008 and with a space 2009 secured between the plurality of non-contact surfaces 2010.
The recess 2002 has a bottom surface 2012 with which the end of the objective lens 7 in the optical axis direction comes into contact, and the inner peripheral portion 2006 stands from the outer periphery of the bottom surface 2012. The plurality of contact surfaces 2008 are provided so as to be able to contact a portion near the bottom surface 2012 in the optical axis direction of the objective lens 7. The plurality of non-contact surfaces 2010 are provided such that a space 2009 is secured from the bottom surface 2012 over the entire length of the objective lens 7 in the optical axis direction.
In addition, adhesive filling recesses 2014 are formed at locations corresponding to the four corners of the upper surface 2013 opposite to the bottom surface 2012 of the lens holder 2, and the adhesive filling recesses 2014 are filled with the adhesive, thereby the objective lens 7. Is bonded to the lens holder 2.
Further, lens protection convex portions 2016 projecting in the focus direction Z are provided at two positions sandwiched in the tracking direction X on the upper surface 2013, and the tip of the lens protective convex portion 2016 is attached to the lens holder 2. It protrudes from the lens surface facing the optical disc 102 of the optical disc 102. As a result, when the lens surface of the objective lens 7 is moved in a direction in contact with the optical disk 102, the lens surface of the objective lens 7 is damaged by the contact of each lens protection convex portion 2016 with the optical disk 102. It is preventing.

Next, the operation of the optical pickup 104 will be described.
A case where the lens holder 2 is moved in the focus direction Z and the tracking direction X will be described.
When a focus drive signal is supplied from the servo control unit 109 to the focus coil 20, the force in the focus direction Z generated by the magnetic interaction between the magnetic field generated in the focus coil 20 and the magnetic field of each magnet 19 is applied to the lens holder 2. By acting, the lens holder 2 is moved in the focus direction Z.
When a tracking drive signal is commonly supplied from the servo control unit 109 to each tracking coil 30, the force in the tracking direction X is generated by the magnetic interaction between the magnetic field generated in each tracking coil 30 and the magnetic field of each magnet 19. Acts on the lens holder 2 to move the lens holder 2 in the tracking direction X.
In a state where the focus drive signal is not supplied to the focus coil 20, the lens holder 2 is held at the neutral position in the focus direction Z by the elasticity of the suspension wire 80, and the tracking drive signal is tracked. When not supplied to the coil 30, the lens holder 2 is held at the neutral position in the tracking direction X by the elasticity of the suspension wire 80.

Next, simulation results of temperature distributions of the lens holder 2 and the objective lens 7 in a state where drive signals are respectively supplied to the focus coil 20 and the tracking coils 30 and the coils generate heat will be described.
9 is a schematic diagram showing a temperature distribution in a state where the objective lens and the lens holder are broken along a plane parallel to the tracking direction X including the optical axis of the objective lens, and FIG. 10 shows the optical axis of the objective lens and the lens holder. FIG. 11 is a schematic diagram showing the temperature distribution in the DD line cross section of FIGS. 9 and 10. FIG.
9 to 11, symbols T1 to T5 are temperatures, and the relationship between the temperatures is T1 <T2 <T3 <T4 <T5, and the temperatures T1, T2, T3, T4, and T5 are temperature differences between adjacent temperatures. Is a constant value. In the simulation, the environmental temperature of the optical pickup 104 is set, and the temperature distribution of the yoke base 18 of the optical pickup 104 is also analyzed.
As shown in FIGS. 9 to 11, the inner peripheral portion 2006 of the lens holder 2 includes a plurality of contact surfaces 2008 that can contact the outer peripheral surface 7002 of the objective lens 7 and a space 2009 in the outer peripheral surface 7002 of the objective lens 7. A plurality of non-contact surfaces 2010 that face each other are arranged alternately along the circumferential direction of the inner peripheral portion 2006.
That is, the objective lens 7 is positioned on the lens holder 2 through the contact surface 2008 and the contact surface 2008 and the inner peripheral portion 2006 of the lens holder 2 are in contact with each other, but the outer peripheral surface 7002 of the objective lens 7 and the lens holder 2 are in contact. A plurality of spaces 2009 are interposed between the inner peripheral portion 2006 with a non-contact surface 2010 interposed therebetween.
Therefore, conduction of heat generated by the current flowing through the tracking coil 20 and the focus coil 30 to the objective lens 7 is performed through the plurality of contact surfaces 2008, but there are a plurality of non-contact surfaces 2010. Very little.
Therefore, by appropriately arranging a plurality of contact surfaces 2008 and a plurality of non-contact surfaces 2010, the focus coil 20 and the four tracking coils 30 are conducted to the outer periphery of the objective lens 7 via the lens holder 2. It becomes possible to make the heat substantially uniform over the entire outer periphery.
Accordingly, as shown in FIGS. 9 to 11, each of the temperatures T <b> 1 to T <b> 5 of the objective lens 7 located on the circumference of the same radius centered on the optical axis of the objective lens 7 extends over the entire circumference of the objective lens 7. The temperature gradient changes outward in the radial direction with a similar temperature gradient, and the temperature gradient at the seven objective lens positions on the circumference of the same radius can be made substantially zero.
Thus, if the temperature gradient at the seven objective lens positions on the circumference of the same radius of the objective lens 7 is substantially zero, coma and astigmatism are very small as optical aberrations generated in the objective lens 7. Therefore, it can be ignored and only spherical aberration needs to be considered. Such spherical aberration can be easily corrected by the optical system of the optical pickup 104.
According to the present embodiment, the occurrence of a temperature gradient in the objective lens can be suppressed without interposing an annular member made of a material having a high thermal conductivity as in the past between the objective lens and the lens holder. Therefore, the number of components can be reduced, which is advantageous in reducing the size and cost of the optical pickup, and the lens holder can be reduced in weight, which is advantageous in improving the response of the optical pickup.
Further, providing the lens holder 2 with a plurality of non-contact surfaces 2010 eliminates the need for the material of the lens holder 2 having a volume corresponding to the space 2009, which is advantageous in reducing the weight of the lens holder 2.

In this embodiment, when viewed from the optical axis direction of the objective lens 7, each tracking coil 30 includes an inner coil portion 3004 positioned at a position inside the contour of the lens holder 2 in the tracking direction X, and a tracking direction. X has an outer coil portion 3006 located at a position outside the contour of the lens holder 2. In other words, the lens holder 2 has a rectangular plate shape, two of the four sides of the rectangle are provided in parallel with the tracking direction X, and the other two sides are provided in parallel with the tangential direction Y, and the tracking coil Reference numeral 30 denotes both ends of the two sides extending in parallel with the tracking direction X of the lens holder 2, part of which protrudes from the end of the lens holder 2 in the tracking direction X.
Therefore, the heat generated in the outer coil portion 3006 located outside the contour of the lens holder 2 is easily radiated into the air and is not easily transmitted to the objective lens 7. As a result, heat generated by the four tracking coils 30 is easily dispersed, which is advantageous in uniformly transferring the heat over the entire outer periphery of the objective lens 7.
If the lens holder 2 is provided in a square plate shape and the four tracking coils 30 are provided at the four corners of the lens holder 4, the lens holder 2 is equidistant in the circumferential direction on the circumference centered on the optical axis of the objective lens 7. Each tracking coil 30 can be arranged in this manner, which is advantageous in uniformly transferring the heat generated in each tracking coil 30 over the entire outer periphery of the objective lens 7.

In the present embodiment, the case where the objective lens 7 is made of a plastic lens has been described. However, the present invention is naturally applicable to a case where the objective lens 7 is made of a glass lens.
In this embodiment, the case where the NA of the objective lens 7 is 0.85 has been described. However, in the present invention, the NA required to prevent astigmatism and coma as much as possible is 0.8. It is particularly suitable for an optical pickup using the above objective lens.
However, the present invention is naturally applicable to an optical pickup having an objective lens with an NA of less than 0.8.
In this embodiment, only the focus coil 20 and the tracking coil 30 are mounted on the lens holder 2 that holds the objective lens 7, but a coil intended to drive in other directions, for example, a tilting coil. Of course, the present invention can be applied even if it is mounted.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an optical disc apparatus incorporating an optical pickup in Embodiment 1 of the present invention. It is a perspective view of the optical pick-up by Example 1 of this invention. 2 is a plan view of the optical pickup according to Embodiment 1. FIG. It is AA sectional view taken on the line of FIG. FIG. 4 is a sectional view taken along line BB in FIG. 3. It is CC sectional view taken on the line of FIG. It is a disassembled perspective view which shows the state which removed the yoke base from the optical pick-up. FIG. 6 is an assembly diagram illustrating a state where the yoke base is removed from the optical pickup. It is a schematic diagram which shows the temperature distribution in the state which fractured | ruptured the objective lens and the lens holder in the plane parallel to the tracking direction X including the optical axis of an objective lens. It is a schematic diagram which shows the temperature distribution in the state which fractured | ruptured the objective lens and the lens holder in the plane parallel to the tangential direction Y including the optical axis of an objective lens. It is a schematic diagram which shows the temperature distribution in the DD line cross section of FIG. 9, FIG.

Explanation of symbols

  2... Lens holder 202... Recessed portion, 2006. Inner circumferential portion, 2008... Abutting surface, 2009... Space, 2010. ... Focus coil, 30... Tracking coil, 101... Optical disk device, 102.

Claims (16)

A lens holder for holding the objective lens;
A focus coil that is provided in the lens holder and moves the lens holder in a focus direction that is an optical axis direction of the objective lens by supplying an electric current;
An optical pickup provided with a tracking coil that is provided in the lens holder and moves the lens holder in a tracking direction orthogonal to the focus direction by supplying an electric current;
The lens holder has a recess for accommodating the objective lens,
The concave portion includes an inner peripheral portion having a diameter corresponding to the outer peripheral surface of the objective lens,
The inner peripheral portion includes a plurality of contact surfaces that can contact the outer peripheral surface of the objective lens and a plurality of non-contact surfaces that face the outer peripheral surface of the objective lens through a space. It is composed of being arranged alternately along the direction,
The objective lens is attached to the recess in a state in which an outer peripheral surface thereof is in contact with the plurality of contact surfaces and the space is secured between the plurality of non-contact surfaces.
An optical pickup characterized by that.   The concave portion has a bottom surface with which an end portion of the objective lens in the optical axis direction is in contact, the inner peripheral portion is erected from the outer periphery of the bottom surface, and the plurality of contact surfaces are in the optical axis direction of the objective lens The plurality of non-contact surfaces are provided so as to ensure the space from the bottom surface over the entire length in the optical axis direction of the objective lens. The optical pickup according to claim 1.   The objective lens has a flat cylindrical shape, the lens holder has a rectangular plate shape, the concave portion is formed in the center of the lens holder, and the inner peripheral portions corresponding to the four corners of the lens holder are respectively The optical pickup according to claim 1, further comprising a contact surface.   The lens holder has a rectangular plate shape, two of the four sides of the rectangle are provided in parallel to the tracking direction, and the remaining two sides are tangential directions orthogonal to both the focus direction and the tracking direction. The tracking coil is provided at both ends in the extending direction of two sides extending in parallel with the tracking direction of the lens holder, and a part of them extends from the end of the lens holder in the tracking direction. The optical pickup according to claim 1, wherein the optical pickup is provided so as to protrude.   The optical pickup according to claim 1, wherein the lens holder has a rectangular plate shape, and the tracking coil is provided at each corner of the lens holder.   A support block is provided at a distance from the lens holder in a tangential direction, which is a direction orthogonal to both the focus direction and the tracking direction, and the lens holder is guided by the support block via a plurality of suspension wires. 2. The optical pickup according to claim 1, wherein the optical pickup is supported so as to be movable in a tracking direction.   2. The optical pickup according to claim 1, wherein the objective lens is a plastic lens.   2. The optical pickup according to claim 1, wherein the numerical aperture of the objective lens is 0.8 or more. Driving means for holding and rotating the optical disc;
An optical pickup that irradiates a recording and / or reproducing light beam to the optical disk that is rotationally driven by the driving means, and detects a reflected light beam of the irradiated light beam reflected by the optical recording medium; An optical disk device,
The optical pickup is
A lens holder for holding the objective lens;
A focus coil that is provided in the lens holder and moves the lens holder in a focus direction that is an optical axis direction of the objective lens by supplying an electric current;
A tracking coil that is provided in the lens holder and moves the lens holder in a tracking direction orthogonal to the focus direction by supplying an electric current;
The lens holder has a recess for accommodating the objective lens,
The concave portion includes an inner peripheral portion having a diameter corresponding to the outer peripheral surface of the objective lens,
The inner peripheral portion includes a plurality of contact surfaces that can contact the outer peripheral surface of the objective lens and a plurality of non-contact surfaces that face the outer peripheral surface of the objective lens through a space. It is composed of being arranged alternately along the direction,
The objective lens is attached to the recess in a state in which an outer peripheral surface thereof is in contact with the plurality of contact surfaces and the space is secured between the plurality of non-contact surfaces.
An optical disc device characterized by the above.   The concave portion has a bottom surface with which an end portion of the objective lens in the optical axis direction is in contact, the inner peripheral portion is erected from the outer periphery of the bottom surface, and the plurality of contact surfaces are in the optical axis direction of the objective lens The plurality of non-contact surfaces are provided so as to ensure the space from the bottom surface over the entire length in the optical axis direction of the objective lens. The optical disc apparatus according to claim 9.   The objective lens has a flat cylindrical shape, the lens holder has a rectangular plate shape, the concave portion is formed in the center of the lens holder, and the inner peripheral portions corresponding to the four corners of the lens holder are respectively The optical disk apparatus according to claim 9, wherein a contact surface is provided.   The lens holder has a rectangular plate shape, two of the four sides of the rectangle are provided in parallel to the tracking direction, and the remaining two sides are tangential directions orthogonal to both the focus direction and the tracking direction. The tracking coil is provided at both ends in the extending direction of two sides extending in parallel with the tracking direction of the lens holder, and a part of them extends from the end of the lens holder in the tracking direction. The optical disk apparatus according to claim 9, wherein the optical disk apparatus is protruded.   10. The optical disk device according to claim 9, wherein the lens holder has a rectangular plate shape, and the tracking coil is provided at each corner of the lens holder.   A support block is provided at a distance from the lens holder in a tangential direction, which is a direction orthogonal to both the focus direction and the tracking direction, and the lens holder is guided by the support block via a plurality of suspension wires. The optical disk apparatus according to claim 9, wherein the optical disk apparatus is supported so as to be movable in a tracking direction.   The optical disk apparatus according to claim 9, wherein the objective lens is formed of a plastic lens.   The optical disk apparatus according to claim 9, wherein the numerical aperture of the objective lens is 0.8 or more.

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