JPWO2010087010A1 - Optical pickup adjusting method and optical recording / reproducing apparatus - Google Patents

Abstract

When the collimating lens is moved to correct spherical aberration, a converged or diverged light beam is incident on the objective lens, and the tilt characteristic of the objective lens changes greatly. This coma aberration can be sufficiently corrected even when the lens is tilted. This optical pickup adjustment method converts a light beam from a light source into a parallel light beam, and can change the convergence and divergence state of the light beam that moves in the optical axis direction and the light from the collimator lens. The present invention relates to an adjustment method of an optical pickup including an objective lens that focuses a beam on an optical recording medium. That is, the step of moving the collimating lens to correct the spherical aberration, the step of tilting the objective lens with respect to the optical axis direction to correct the coma aberration, the moving distance of the collimating lens and the optical axis direction of the objective lens Biasing the objective lens based on the angle.

Description

  The present invention relates to a method for adjusting an optical pickup for recording or reproducing information on an optical recording medium such as an optical disc, and an optical recording / reproducing apparatus equipped with the optical pickup adjusted by this adjustment method.

  At present, optical discs conforming to the Blu-ray Disc (registered trademark) (hereinafter referred to as “BD”) standard and optical recording / reproducing apparatuses for recording / reproducing information on the optical disc are spreading on the market. In this BD standard, in order to improve the recording density, a blue-violet laser whose wavelength of the emitted light beam is around 400 nm is used as a light source, and an objective lens having a large numerical aperture (NA) (for example, NA = 0.85) is adopted. The optical disc used for the BD standard has a thickness of a cover layer for protecting the information recording surface of 0.1 mm, a single-layer type in which the information recording surface is one layer, and a first layer in the thickness direction. There is a two-layer type in which the second information recording surface is arranged at a predetermined interval.

  Among these, when recording / reproducing information on / from a two-layer type optical disk, switching from one information recording surface to the other information recording surface changes the position where the light beam should be focused, resulting in spherical aberration. . Also, when recording / reproducing information on / from a BD standard optical disc, whether it is a single-layer type or a double-layer type, due to wavelength variation of the light beam, a slight thickness error of the cover layer, etc. Apart from the switching of the information recording surface, large spherical aberration tends to occur. The spherical aberration based on the structure of the optical disc described above is referred to as “spherical aberration based on the structure of the optical disc”.

  Therefore, in order to correct the “spherical aberration based on the structure of the optical disk”, some conventional optical pickups have the following configuration. This optical pickup detects the power of the light beam emitted from the light source, the objective lens, a collimating lens that is disposed between the light source and the objective lens, and is movable in the optical axis direction. And a light detection means. The collimating lens is provided so that the convergence / divergence state of the light beam passing therethrough can be changed by moving in the optical axis direction. The light detection means is provided so as to receive a part of the light beam emitted from the light source and passing through the collimating lens. In this optical pickup, the reference position serving as the movement reference of the collimating lens is detected by utilizing the fact that the convergence / divergence state of the light beam is changed by the movement of the collimating lens and the detection state in the light detecting means is changed. (For example, refer to Patent Document 1). Hereinafter, this technique is referred to as a first conventional example.

  An optical disc is flat and free of warping when it is just purchased, but it may warp if it is used repeatedly or handled violently. When information is recorded / reproduced on / from such an optical disc, coma aberration occurs because the optical axis of the objective lens is not perpendicular to the information recording surface of the optical disc. Further, coma aberration also occurs due to variations in optical components constituting the optical pickup, misalignment, and the like.

  Therefore, in order to correct this coma and to correct newly generated spherical aberration by correcting this coma, some conventional optical recording / reproducing apparatuses have the following configurations. The optical recording / reproducing apparatus includes an objective lens, an objective lens moving unit, a focus error signal generating unit, a focus control unit, a lens tilt unit, a spherical aberration correction unit, and a lens tilt spherical aberration correction control unit. ing. The objective lens moving unit moves the objective lens with respect to the information recording surface. The focus error signal generation unit generates a focus error signal indicating a focused state of the light beam focused on the information recording surface. The focus control unit controls the objective lens moving unit to focus the light beam on the information recording surface based on the focus error signal. The lens tilt unit tilts the objective lens so as to correct coma aberration generated in the light beam focused on the information recording surface. The spherical aberration correction unit corrects the spherical aberration generated in the light beam spot focused on the information recording surface. The lens tilt spherical aberration correction control unit controls the spherical aberration correction unit so that the correction amount of the spherical aberration corrected by the spherical aberration correction unit is switched according to the inclination of the objective lens tilted by the lens tilt unit. (For example, refer to Patent Document 2). Hereinafter, this technique is referred to as a second conventional example.

JP 2008-293601A (Claims 1, [0010], [0011], [0020] to [0046], FIGS. 1 and 2) JP-A-2005-158228 (Claim 1, [0058], [0079] to [0160], FIG. 1A, FIG. 1B, FIG. 2 to FIG. 4)

  By the way, recently, as a material of an objective lens constituting an optical pickup, mainly for the purpose of stabilizing optical characteristics, reducing cost, and reducing weight, olefin resin (for example, cycloolefin), acrylic resin (for example, PMMA). ), Synthetic resins such as methacrylic resins are used. However, an objective lens made of a synthetic resin is more likely to change its optical characteristics (especially spherical aberration) depending on the temperature due to its physical characteristics than an objective lens made of glass. The spherical aberration described above is referred to as “spherical aberration based on objective lens material”. Therefore, in an optical recording / reproducing apparatus that records or reproduces information on an optical disc of the BD standard, a light beam is applied to an information recording surface of an optical disc having a cover layer thickness of 0.1 mm by an objective lens having a high NA of about 0.85. Therefore, a slight change in the optical characteristics of the objective lens greatly affects the recording / reproducing characteristics.

  For this reason, as in the first conventional example described above, the collimating lens is moved in order to correct the “spherical aberration based on the structure of the optical disk”, so that the converged or diverged light beam is incident on the objective lens. In this case, the tilt characteristic of the objective lens (characteristic relating to the amount of coma generated with respect to the tilt angle) changes greatly. In such a state, even if the objective lens is tilted to correct coma aberration based on warpage of the optical disk, as in the second conventional example, the coma aberration should be sufficiently corrected. You may not be able to. In particular, when the optical pickup is in a high temperature (for example, 75 ° C.) environment, the wavelength of the light beam emitted from the light source varies toward the long wavelength side, and the thickness of the cover layer of the optical disc is thicker than a predetermined value. Even if the objective lens is tilted, coma aberration does not occur. As a result, since the coma based on the warp of the optical disk cannot be sufficiently corrected, the optical beam emitted from the light source may not be correctly irradiated on the optical disk, and information may not be recorded or reproduced on the optical disk. There is.

  The problem described above is not only an optical recording / reproducing apparatus equipped with an optical pickup equipped with an objective lens made of synthetic resin, but also an optical recording / reproducing apparatus equipped with an optical pickup equipped with an objective lens made of glass, When information is recorded on or reproduced from a so-called multilayer disc having three or more information recording surfaces, there is a risk of occurrence. Normally, an objective lens made of glass is less likely to generate “spherical aberration based on the objective lens material” even if the temperature of the optical pickup changes. However, when recording or reproducing information on a multilayer disc, Since there is a large difference between the distance to the information recording surface closest to the light incident surface and the distance from the light incident surface to the information recording surface farthest from the light incident surface, the light matched to the selected information recording surface The correction amount of the “spherical aberration based on the structure of the optical disk” of the pickup is also increased. As a result, when recording or reproducing information on a multilayer disk, the amount of movement of the collimator lens is larger than when recording or reproducing information on an optical disk having two or less layers. Even if it is used, the above-described problems may occur.

  The present invention has been made in view of the above-described circumstances, and an example of an object is to solve the above-described problems. An optical pickup adjusting method and an optical pickup that can solve these problems, and An object is to provide an optical recording / reproducing apparatus.

  In order to solve the above problems, an optical pickup adjustment method according to the first aspect of the present invention converts a light beam from a light source into a parallel light beam, and moves the light beam passing in the optical axis direction. An adjustment method of an optical pickup comprising: a collimating lens capable of changing a convergence / divergence state; and an objective lens for condensing a light beam from the collimating lens onto an optical recording medium, wherein the collimating lens is used to correct spherical aberration The objective lens based on the moving distance of the collimator lens and the angle of the objective lens with respect to the optical axis direction. And a step of deflecting the lens.

  The optical recording / reproducing apparatus according to the invention described in claim 5 can convert the light beam from the light source into a parallel light beam, and can change the convergence / divergence state of the light beam moving and passing in the optical axis direction. A collimating lens; an objective lens for condensing the light beam from the collimating lens on an optical recording medium; and the collimating lens is moved to correct spherical aberration, and the objective lens is moved to correct the coma aberration. And a control means for tilting the objective lens based on a moving distance of the collimator lens and an angle of the objective lens with respect to the optical axis direction.

It is the schematic which shows the structure of the optical system of the optical pick-up to which the adjustment method of the optical pick-up concerning Embodiment 1 of this invention is applied. It is a schematic perspective view which shows the structure of the optical system of the optical pick-up shown in FIG. It is a schematic perspective view which shows the structure of the objective lens drive device which drives the objective lens of the optical pick-up shown in FIG. It is a disassembled perspective view which shows the structure of a part of objective-lens drive device shown in FIG. It is a conceptual diagram which shows an example of a structure of the optical recording / reproducing apparatus carrying the optical pick-up shown in FIG. It is a conceptual diagram which shows an example which inclines the objective lens of the optical pick-up shown in FIG. 1 centering on a principal point. It is a figure which shows an example of the calculation result of the characteristic of each aberration with respect to temperature in case the objective lens inclines 0.5 degree | times about the optical pickup shown in FIG. It is a figure which shows an example of the characteristic of each aberration with respect to the inclination in the YZ plane of an objective lens when the wavelength of a light beam is a long wavelength and the cover layer of an optical disk is thick in an optical pick-up environment. It is a figure which shows an example of the characteristic of each aberration with respect to the inclination in the YZ surface of an objective lens in case an optical pick-up is a low wavelength environment, the wavelength of a light beam is a short wavelength, and the cover layer of an optical disk is thin. It is a figure which shows an example of the lens deviation characteristic at the time of entering a parallel light beam into an objective lens. It is a figure which shows an example of the lens deviation characteristic when a convergent light beam is incident on the objective lens. It is a figure which shows an example of the lens deviation characteristic when a divergent light beam is incident on the objective lens. It is a conceptual diagram for demonstrating the 1st method of inclining an objective lens centering on a principal point, and biasing in the direction which a flange falls. It is a conceptual diagram for demonstrating the 2nd method of inclining an objective lens centering on a principal point, and biasing in the direction where a flange goes up. It is a figure which shows an example of the tilt characteristic of the objective lens in the condition where the light beam has a long wavelength, the cover layer is thick, and the divergent light beam is incident on the objective lens at a high temperature. (B) is an example of the tilt characteristic when the objective lens is tilted and deflected. It is a figure which shows an example of the tilt characteristic of the objective lens in the condition where the light beam has a short wavelength, the cover layer is thin, and the convergent light beam is incident on the objective lens at a low temperature. (B) is an example of the tilt characteristic when the objective lens is tilted and deflected. It is a flowchart for demonstrating the specific process of the adjustment method of the optical pick-up which concerns on Embodiment 1 of this invention. It is a flowchart for demonstrating the specific process of the adjustment method of the optical pick-up which concerns on Embodiment 1 of this invention. It is a flowchart for demonstrating the specific process of the adjustment method of the optical pick-up which concerns on Embodiment 1 of this invention. It is a conceptual diagram which shows an example of the relationship between the angle (theta) by which the radial tilt of the objective lens was adjusted, and the lens deviation | shift amount d. It is a figure which shows an example of the relationship between the step number of a collimating lens, and the coefficient K. It is a figure which shows an example of the relationship between the number of steps of a collimating lens, and the deflection amount d of an objective lens at the time of carrying out radial tilt adjustment of the objective lens only by 0.4 degree | times. It is a conceptual diagram for demonstrating the basic idea of the adjustment method of the optical pick-up concerning Embodiment 3 of this invention. It is a conceptual diagram for demonstrating the basic idea of the adjustment method of the optical pick-up concerning Embodiment 3 of this invention. It is a conceptual diagram for demonstrating the basic idea of the adjustment method of the optical pick-up concerning Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram showing a configuration of an optical system of an optical pickup 1 to which an optical pickup adjustment method according to Embodiment 1 of the present invention is applied. FIG. 2 is a schematic perspective view showing a configuration of the optical system of the optical pickup 1. FIG.
The optical pickup 1 has a semiconductor laser 3 as a light source that emits a light beam. For example, the semiconductor laser 3 emits a light beam having a wavelength of 406 nm for recording / reproducing the BD standard optical disc (optical recording medium) 2.

  At a predetermined position on the light emitting side of the semiconductor laser 3, a polarizing beam splitter 4, a collimating lens 5, a rising mirror 6, a quarter wavelength plate 7, and an objective lens 8 are arranged in this order. The polarization beam splitter 4 reflects almost 100% of the P-polarized linearly polarized light component of the light beam from the semiconductor laser 3 and enters the collimating lens 5. The polarizing beam splitter 4 transmits 90% or more of the S-polarized linearly polarized light component from the rising mirror 6 and enters the sensor lens 9 described later.

  The collimating lens 5 converts the divergent light beam from the polarization beam splitter 4 into a parallel light beam, and converts the parallel light beam from the rising mirror 6 into a focused light beam. Further, the collimating lens 5 is configured to be movable in the optical axis direction as indicated by an arrow in FIG. Although not shown, the moving unit of the collimating lens 5 is driven based on, for example, a holder for holding the collimating lens 5, a lead nut attached to the holder, a screw meshing with the lead nut, and a pulse signal supplied from the outside. And a stepping motor that rotationally drives the screw. For details of the moving unit of the collimating lens 5, see, for example, Patent Document 1 described above.

  The rising mirror 6 reflects the light beam that has passed through the collimating lens 5, bends the optical path, rises in the direction of the optical disk 2, and enters the quarter-wave plate 7. Further, the rising mirror 6 reflects the light beam from the quarter-wave plate 7, bends the optical path, and enters the collimating lens 5.

  The quarter-wave plate 7 converts the P-polarized linearly polarized light component (hereinafter referred to as “outgoing light beam”) of the light beam from the rising mirror 6 into a circularly polarized light component and circularly polarized light from the objective lens 8. The component is converted into a linearly polarized light component in a direction orthogonal to the polarization direction of the forward light beam, that is, the linearly polarized light component of the S-polarized light.

  The objective lens 8 condenses the parallel light beam from the quarter wavelength plate 7 on the information recording surface of the optical disc 2 and converts the reflected light beam from the optical disc 2 into a parallel light beam. The objective lens 8 is integrally formed by injection molding or extrusion molding using synthetic resin such as olefin resin (for example, cycloolefin), acrylic resin (for example, PMMA), and methacrylic resin as a raw material. The objective lens 8 has a substantially disk shape as a whole, and its lower surface is a spherical or aspherical convex curved surface forming a lens surface. On the outer periphery of the objective lens 8, an annular flange (outer ring portion, edge) 8 a is provided.

  On the other hand, a sensor lens 9 and a light receiving element 10 are arranged in this order on the light transmitting side of the polarization beam splitter 4 when viewed from the collimating lens 5. The sensor lens 9 expands the light beam reflected by the optical disc 2 with a predetermined optical system magnification. The sensor lens 9 is configured to be movable in the optical axis direction when the optical pickup 1 is assembled and adjusted. In other words, by moving the sensor lens 9 in the optical axis direction, the in-focus position on the light receiving surface provided on the light receiving element 10 of the light beam reflected by the optical disc 2 can be optically adjusted. Has been.

  The light receiving element 10 includes, for example, a PDIC (photo diode integrated circuit) or an optoelectronic integrated circuit (OEIC). The light receiving element 10 is provided with a plurality of light receiving regions, and each receives light beams emitted from the semiconductor laser 3 and reflected by the information recording surface of the optical disc 2. Each received light beam is independently photoelectrically converted in each light receiving cell further divided in each light receiving region and output as an electric signal.

  Next, the configuration of the objective lens driving device for driving the objective lens 8 will be described with reference to a schematic perspective view shown in FIG. 3 and an exploded perspective view shown in FIG. The objective lens driving device includes a movable part 11 and a fixed part 12. The movable portion 11 is schematically configured by an objective lens 8, a lens holder 21, track coils 22a to 22d, focus coils 23a and 23b, radial tilt coils 24a and 24b, and printed boards 25a and 25b. On the other hand, the fixing portion 12 is generally configured by a wire base 31, a printed board 32, a yoke base 33, and magnets 34a and 34b.

  The movable part 11 is configured such that the operation center coincides with the optical axis of the objective lens 8. The objective lens 8 is fixed to the upper part of the lens holder 21 with an adhesive (not shown). The lens holder 21 is integrally formed by injection molding or extrusion molding using a lightweight and highly rigid synthetic resin as a raw material. Examples of the synthetic resin include liquid crystal polymer (LCP) and polyphenylene sulfide (PPS). The lens holder 21 may be made of the above synthetic resin whose glass fiber or carbon is used to enhance the rigidity.

The lens holder 21 has a substantially cubic shape as a whole, has an open bottom surface, and is hollow. As shown in FIG. 4, the lens holder 21 includes track coils 22a to 22d, focus coils 23a and 23b, a radial tilt coil 24a, and both side surfaces 21a and 21b opposed to the tangential direction (X ₊ -X ₋ direction). 24b are respectively attached. The track coils 22a to 22d, the focus coils 23a and 23b, and the radial tilt coils 24a and 24b are all wound around the tangential direction (X ₊ -X ₋ direction) as a central axis, and have common specifications.

The track coils 22a to 22d are ring-shaped solenoid coils that are long in the radial direction (Y ₊ -Y ₋ direction). The track coils 22 a and 22 b are arranged in parallel above and below the side surface 21 a of the lens holder 21. On the other hand, the track coils 22 c and 22 d are arranged in parallel above and below the side surface 21 b of the lens holder 21.

The focus coils 23a and 23b and the radial tilt coils 24a and 24b are ring-shaped solenoid coils that are long in the focus direction (optical axis direction) (Z ₊ -Z ₋ direction). The focus coil 23a is disposed on the track coils 22a and 22b and at one end in the radial direction (Y ₊ -Y ₋ direction) of the track coils 22a and 22b. On the other hand, the radial tilt coil 24a is disposed on the track coils 22a and 22b and at the other end of the track coils 22a and 22b in the radial direction (Y ₊ -Y ₋ direction). The focus coil 23b is disposed on the track coils 22c and 22d and at the other end in the radial direction (Y ₊ -Y ₋ direction) of the track coils 22c and 22d. On the other hand, the radial tilt coil 24b is disposed on the track coils 22c and 22d and at one end of the track coils 22c and 22d in the radial direction (Y ₊ -Y ₋ direction). That is, the focus coil 23a and the focus coil 23b are disposed at diagonal positions, and the radial tilt coil 24a and the radial tilt coil 24b are disposed at diagonal positions.

As shown in FIG. 3, printed circuit boards 25 a and 25 b are attached to both side surfaces 21 c and 21 d facing the radial direction (Y ₊ -Y ₋ direction) of the lens holder 21. The printed circuit boards 25a and 25b are made of a conductive elastic body, and one end side of each of the flexible suspension wires 26 is soldered and fixed at a predetermined interval. On the other hand, each other end side of the suspension wire 26 is fixed by soldering to a printed circuit board 32 attached to the wire base 31. Accordingly, the movable portion 11 is cantilevered by the wire base 31 and the printed circuit board 32 via the suspension wire 26 and is elastically supported so as to be relatively displaceable with respect to the fixed portion 12.

  Further, one end of each of the six suspension wires 26 is soldered and electrically connected to one end of each of the track coils 12a to 12d, the focus coils 13a and 13b, and the radial tilt coils 14a and 14b. On the other hand, the other ends of the six suspension wires 26 are electrically connected to the lens driving circuit 47 (see FIG. 5) via the printed circuit board 32, respectively. That is, the suspension wire 26 functions as an elastic body (supporting body) for supporting the movable portion 11 and power supply to the track coils 12a to 12d, the focus coils 13a and 13b, and the radial tilt coils 14a and 14b. It also has a function as a lead wire. The suspension wire 26 may be another elastic body such as a leaf spring, a coil spring, or conductive rubber.

The yoke base 33 is made of a known magnetic material such as a metal such as pure iron, oxygen-free steel, or silicon steel, or an alloy. On the yoke base 33, standing walls 33a and 33b that face the tangential direction (X ₊ -X ₋ direction) and have a predetermined thickness extend in the focus direction (Z ₊ −Z ₋ direction). ing. Magnets 34a and 34b are fixed to the standing walls 33a and 33b so as to face each other. Thereby, the standing walls 33a and 33b and the magnets 34a and 34b constitute a magnetic circuit.

  As shown in FIG. 3, the wire base 31 is disposed on the opposite side of the standing wall 33b to the fixed surface of the magnet 34b, and the lens holder 21 is disposed between the standing wall 33a and the standing wall 33b. Thus, the track coils 12a to 12d, the focus coils 13a and 13b, and the radial tilt coils 14a and 14b face the magnets 34a and 34b. For this reason, an actuator for moving the movable portion 11 is configured by a combination of the track coils 12a to 12d, the focus coils 13a and 13b, the radial tilt coils 14a and 14b, and the magnets 34a and 34b.

The magnets 34a and 34b are made of, for example, a permanent magnet such as a rare earth (eg, neodymium), samarium / cobalt, alnico, or ferrite magnet. The magnets 34a and 34b have a substantially rectangular parallelepiped shape when viewed in parallel with the tangential direction (X ₊ -X ₋ direction). The magnets 34a and 34b are divided into four with the substantially cross-shaped magnetization boundary lines a and b as boundaries, and each of the further divided areas is magnetized. The magnetization direction of each region of the magnets 34a and 34b is perpendicular to and adjacent to a virtual plane (YZ plane) including a focus direction (Z ₊ -Z _- direction) and a radial direction (Y ₊ -Y _- direction). It is magnetized in the opposite direction to the matching area.

  In a state where the movable part 11 is attached to the wire base 31 via the suspension wire 26, the magnets 34a and 34b, the track coils 12a to 12d, the focus coils 13a and 13b, and the radial tilt coils 14a and 14b Are arranged symmetrically. In this state, the magnetization boundary line a of the magnets 34a and 34b is located at the center of each of the track coils 12a to 12d, and the magnetization boundary line b at the center of the focus coils 13a and 13b and the radial tilt coils 14a and 14b. Track coils 12a to 12d, focus coils 13a and 13b, and radial tilt coils 14a and 14b face the magnets 34a and 34b.

The track coils 12a to 12d, the focus coils 13a and 13b, and the radial tilt coils 14a and 14b are supplied with power independently via a suspension wire 26. When the power is supplied, the track coils 12a to 12d generate thrust in the horizontal direction (track direction), that is, in the radial direction (Y ₊ -Y ₋ direction). On the other hand, the focus coils 13a and 13b and the radial tilt coils 14a and 14b generate thrust in the vertical direction, that is, the focus direction (Z ₊ -Z ₋ direction) when supplied with power.

  Here, when power is supplied to the focus coils 13a and 13b, thrusts in the same direction are generated, so that the objective lens 8 moves along the focus direction. On the other hand, when power is supplied to the radial tilt coils 14a and 14b, thrusts in opposite directions are generated. Therefore, a radial tilt torque is generated, and the optical axis of the objective lens 8 can be tilted. The amount of inclination of the optical axis of the objective lens 8 is controlled by the value of current flowing through the focus coils 13a and 13b.

  Next, the configuration of an optical recording / reproducing apparatus equipped with the above-described optical pickup 1 will be described with reference to the schematic diagram shown in FIG. This optical recording / reproducing apparatus includes the optical pickup 1, the spindle motor 41, the spindle motor drive circuit 42, the controller 43, the feed motor 44, the feed motor drive circuit 45, the laser drive circuit 46, and the lens drive circuit. 47.

  The spindle motor drive circuit 42 rotates the optical disc 2 by driving the spindle motor 41 under the control of the controller 43. The controller 43 controls the spindle motor drive circuit 42, the feed motor drive circuit 45, the laser drive circuit 46, and the lens drive circuit 47 based on detection signals from the light receiving element 10 supplied from the optical pickup 1.

  The feed motor drive circuit 45 drives the feed motor 44 under the control of the controller 43 to move the optical pickup 1 in the radial direction of the optical disc 2. The laser drive circuit 46 generates a laser drive signal for driving the semiconductor laser 3 (see FIGS. 1 and 2) constituting the optical pickup 1 under the control of the controller 43 and supplies the laser drive signal to the optical pickup 1. The lens driving circuit 47 generates a lens driving signal for controlling the focusing, tracking, and radial tilt of the objective lens 8 constituting the optical pickup 1 and for adjusting the position of the collimating lens 5 under the control of the controller 43. And supplied to the optical pickup 1.

  The controller 43 includes a focus servo tracking circuit 51, a tracking servo tracking circuit 52, a tilt adjustment circuit 53, a collimator lens adjustment circuit 54, and a laser control circuit 55. The focus servo follow-up circuit 51 applies light to the information recording surface of the rotating optical disc 2 based on a focus error signal (FE signal) generated by calculation from a detection signal from the light receiving element 10 supplied from the optical pickup 1. A focus servo signal for focusing the light beam emitted from the pickup 1 is generated and supplied to the lens driving circuit 47.

  The tracking servo tracking circuit 52 applies an eccentric signal track of the optical disc 2 based on a tracking error signal (TE signal) generated by calculation from a detection signal from the light receiving element 10 supplied from the optical pickup 1. Then, a tracking servo signal for following the beam spot of the light beam emitted from the optical pickup 1 is generated and supplied to the lens driving circuit 47. The tilt adjustment circuit 53 is based on the TE signal or other signal generated by calculation from the detection signal from the light receiving element 10 supplied from the optical pickup 1, and the objective lens 8 constituting the optical pickup 1 (FIGS. 1 and 1). 2) is generated and is supplied to the lens driving circuit 47.

  The collimating lens adjustment circuit 54 adjusts the collimating lens 5 constituting the optical pickup 1 based on the FE signal or the TE signal generated by calculation from the detection signal at the light receiving element 10 supplied from the optical pickup 1. A collimating lens adjustment signal is generated and supplied to the lens driving circuit 47. The laser control circuit 55 generates an appropriate laser drive signal based on the recording condition setting information recorded on the optical disc 2 extracted from the detection signal from the light receiving element 10 supplied from the optical pickup 1.

  The controller 43 may be configured by hardware such as a digital signal processor (DSP) and a sequencer, and the CPU (central processing unit) is configured by the focus servo tracking circuit 51, the tracking servo tracking circuit 52, the tilt adjustment circuit 53, The processes performed by the collimating lens adjustment circuit 54 and the laser control circuit 55 may be executed based on a program.

  Next, an outline of an adjustment method of the optical pickup 1 in the optical recording / reproducing apparatus having the above configuration will be described. As described in the section “Problems to be Solved by the Invention”, the objective lens 8 made of synthetic resin generates a large amount of “spherical aberration based on the objective lens material” depending on the temperature due to its physical characteristics. When the collimating lens 5 is moved in order to correct the “spherical aberration based on the structure of the optical disk” and the like, when the converged or diverged light beam is incident on the objective lens 8, the tilt characteristic of the objective lens 8 (coma aberration with respect to the tilt angle) (Characteristics related to the generation amount) greatly change.

  Therefore, in order to correct the coma based on the warp of the optical disk 2, the coma can be sufficiently corrected even when the objective lens 8 is tilted about the principal point 8b as shown in FIG. It may not be possible. In particular, when the optical pickup 1 is in a high temperature (for example, 75 ° C.) environment, the wavelength of the light beam emitted from the semiconductor laser 3 varies toward the long wavelength side, and the thickness of the cover layer of the optical disc 2 exceeds a predetermined value. If it is thick, coma will not occur even if the objective lens 8 is tilted.

  FIG. 7 shows the characteristics of each aberration (low-order aberration of Zernike aberration (third-order aberration term)) (hereinafter simply referred to as “aberration”) with respect to temperature when the objective lens 8 is tilted by 0.5 degrees with respect to the optical pickup 1. It is a figure which shows an example of the calculation result of. In this example, the wavelength of the light beam is 410 nm, and the thickness of the cover layer of the optical disc 2 is 0.1 mm. FIG. 8 shows a case where the wavelength of the light beam from the semiconductor laser 3 is a long wavelength and the thickness of the cover layer of the optical disc 2 is larger than a predetermined value in an environment where the optical pickup 1 is at a high temperature (for example, 75 ° C.). It is a figure which shows an example of the characteristic of each aberration with respect to the inclination in the YZ surface (refer FIG. 3) of the objective lens 8. FIG. Furthermore, FIG. 9 shows the YZ plane of the objective lens 8 when the wavelength of the light beam from the semiconductor laser 3 is short and the thickness of the cover layer of the optical disc 2 is smaller than a predetermined value when the optical pickup 1 is in a low temperature environment. It is a figure which shows an example of the characteristic of each aberration with respect to the inclination in (refer FIG. 3).

  7 to 9, a curve a is a characteristic curve of wavefront aberration (Root Mean Square) of each term of the Zernike aberration equation, and a curve b is defocus (the third term of the Zernike aberration equation). The characteristic curve, curve c, is the characteristic curve of the third-order astigmatism (as aberration) in the 0-90 ° direction (the fourth term of the Zernike aberration equation). Curve d is the characteristic curve of the third-order as aberration in the ± 45 ° direction (the fifth term of the Zernike aberration equation), and curve e is the 0-180 ° direction of the third-order coma aberration (the first of the Zernike aberration equation). 6) characteristic curve, curve f is the characteristic curve of the third-order coma aberration in the ± 90 ° direction (the seventh term of the Zernike aberration equation), and curve g is the third spherical aberration (the Zernike aberration equation eighth). Is a characteristic curve of the item).

  As can be seen from FIG. 7, in a high-temperature environment, even when the objective lens 8 is tilted by 0.5 degrees about the principal point 8b, the third-order coma aberration in the 0-180 ° direction (see curve e) is almost generated. Absent. In particular, when the cover layer of the optical disk 2 is thick at high temperatures and long wavelengths, the third-order coma aberration in the 0-180 ° direction (see curve e) hardly occurs as can be seen from FIG. On the other hand, as can be seen from FIG. 9, when the cover layer of the optical disk 2 is thin at low temperature, short wavelength, and when the objective lens 8 is tilted by 0.5 degrees about the principal point 8b, the third order A coma aberration direction of 0-180 ° (see curve e) is greatly generated. Therefore, in particular, when the cover layer of the optical disk 2 is thick at high temperatures, long wavelengths, simply tilting the objective lens 8 about the principal point 8b, as shown in FIG. Since the coma based thereon cannot be corrected sufficiently, the optical beam 2 emitted from the semiconductor laser 3 may not be correctly irradiated onto the optical disc 2 and information may not be recorded or reproduced on the optical disc 2.

  Therefore, the inventor has found that the objective lens 8 can be used even when the optical pickup 1 is in a high temperature environment, the wavelength of the light beam from the semiconductor laser 3 is long, and the thickness of the cover layer of the optical disc 2 is larger than a predetermined value. As a result of intensive studies on the conditions that can sufficiently ensure the amount of coma generated with respect to the tilt on the YZ plane (see FIG. 3), the inventors have come up with the idea of the optical pickup adjustment method described below.

  FIG. 10 is a diagram showing an example of a characteristic of each aberration (hereinafter referred to as “lens deviation characteristic”) with respect to a decenter of the objective lens 8 on the Y axis when a parallel light beam is incident on the objective lens 8. . FIG. 11 is a diagram illustrating an example of lens deviation characteristics when a convergent light beam is incident on the objective lens 8. Furthermore, FIG. 12 is a diagram illustrating an example of lens deviation characteristics when a divergent light beam is incident on the objective lens 8. 10 to 12, the meanings of the curves a to g are the same as those in FIGS. 7 to 9.

As can be seen from FIGS. 10 to 12, when a parallel light beam is incident on the objective lens 8, each aberration does not occur even if the objective lens 8 is deflected, but a convergent light beam or a divergent light beam is applied to the objective lens 8. When the objective lens 8 is deflected, aberration, in particular, wavefront aberration (see curve a) and third-order coma aberration in the 0-180 ° direction (see curve e) are generated. Here, “bias” refers to moving the objective lens 8 in a direction orthogonal to the optical axis of the light beam.
Therefore, when the cover layer of the optical disk 2 is thick at high temperature, long wavelength, and moving the collimating lens 5 to correct “spherical aberration based on the structure of the optical disk”, a converged or diverged light beam is obtained. When incident on the objective lens 8, coma aberration can be generated by tilting the objective lens 8 about the principal point 8 b and deviating it. It can be assumed that it can be corrected.

  Next, the relationship between the tilt and deflection direction of the objective lens 8 and the sensitivity of coma will be considered. As shown in FIG. 13, the deflection direction of the objective lens 8 is shown in FIG. 14 in which the objective lens 8 is tilted about the principal point 8b and the flange 8a is lowered in the downward direction (first method). As described above, there is a method (second method) in which the objective lens 8 is tilted about the principal point 8b and biased in the direction in which the flange 8a is raised.

  As a result of extensive studies by the inventors, it has been found that the sensitivity of the coma aberration increases in the first method, whereas the sensitivity of the coma aberration decreases in the second method. Therefore, when the optical pickup 1 is in a high temperature environment and the wavelength of the light beam from the semiconductor laser 3 is long and the thickness of the cover layer of the optical disc 2 is thicker than a predetermined value, the first method is adopted, When the wavelength of the light beam from the semiconductor laser 3 is a short wavelength and the thickness of the cover layer of the optical disk 2 is thinner than a predetermined value under the low temperature environment 1, the second method is adopted to A conclusion has been reached that coma based on warpage can be sufficiently corrected.

  That is, when the optical pickup 1 is in a high temperature environment, the wavelength of the light beam from the semiconductor laser 3 is long, and the thickness of the cover layer of the optical disc 2 is larger than a predetermined value. If the diverging light beam is incident on the objective lens 8 by moving the collimating lens 5 to correct the “aberration”, the first method may be adopted. On the other hand, when the optical pickup 1 is in a low temperature environment, the wavelength of the light beam from the semiconductor laser 3 is short, and the thickness of the cover layer of the optical disc 2 is smaller than a predetermined value. If the convergent light beam is incident on the objective lens 8 by moving the collimating lens 5 in order to correct the “aberration”, the second method may be adopted.

  FIG. 15A shows a case where the optical pickup 1 is in a high temperature environment, the wavelength of the light beam from the semiconductor laser 3 is long, and the thickness of the cover layer of the optical disc 2 is larger than a predetermined value. When the collimating lens 5 is moved in order to correct the “spherical aberration based on the structure”, the diverging light beam is incident on the objective lens 8, and the objective lens 8 is not tilted by being tilted. It is an example of a tilt characteristic. On the other hand, FIG. 15B is an example of a tilt characteristic when the objective lens 8 is tilted and deflected in the same situation as FIG. 15A. As can be seen by comparing FIGS. 15A and 15B, the frame characteristics (see curve e) are slightly increased.

  On the other hand, FIG. 16A shows a case where the optical pickup 1 is in a low temperature environment, the wavelength of the light beam from the semiconductor laser 3 is short, and the thickness of the cover layer of the optical disc 2 is smaller than a predetermined value. By moving the collimating lens 5 in order to correct the “spherical aberration based on the structure of the optical disk”, the objective lens 8 is not deflected simply by tilting in the situation where the convergent light beam is incident on the objective lens 8. It is an example of the tilt characteristic in a case. On the other hand, FIG. 16B is an example of a tilt characteristic when the objective lens 8 is tilted and deflected in the same situation as FIG. As can be seen by comparing FIGS. 16A and 16B, the frame characteristics (see curve e) are slightly reduced. 15 and 16, the meanings of the curves a to g are the same as those in FIGS. 7 to 9.

Next, a method for adjusting the optical pickup 1 described above will be specifically described with reference to flowcharts shown in FIGS. In the following description, it is assumed that the controller 43 performs the corresponding processing based on the corresponding program.
The optical recording / reproducing apparatus of this example starts the adjustment process of the optical pickup 1 described below from the time when the power is turned on, and continuously performs this process while the power is turned on. That is, after the power is supplied to the optical recording / reproducing apparatus of this example, the controller 43 proceeds to the processing of step SP1 shown in FIG. 17 and determines whether or not it has been activated. If the determination result in step SP1 is “YES”, that is, if the optical recording / reproducing apparatus of this example is turned on, the controller 43 proceeds to step SP2.

  In step SP2, the controller 43 generates a collimating lens adjustment signal for moving the collimating lens 5 to the initial position, supplies it to the lens driving circuit 47, and then proceeds to step SP3. Accordingly, the lens driving circuit 47 generates a lens driving signal (pulse signal) for moving the collimating lens 5 to the initial position based on the collimating lens adjustment signal supplied from the controller 43 and supplies the lens driving signal to the optical pickup 1. To do. In step SP3, the controller 43 generates a collimating lens adjustment signal for moving the collimating lens 5 to a position where the sensitivity of the FE signal is maximized, supplies the collimating lens adjustment signal to the lens driving circuit 47, and then proceeds to step SP4. Accordingly, the lens driving circuit 47 generates a lens driving signal (pulse signal) for moving the collimating lens 5 for coarse adjustment based on the collimating lens adjustment signal supplied from the controller 43, and the optical pickup 1. To supply. For details of the processing in step SP3, refer to, for example, Japanese Patent Laid-Open No. 2008-41186.

  In step SP4, the controller 43 turns on the focus servo, and then proceeds to step SP5. In step SP5, the controller 43 determines whether or not information is recorded on the optical disc 2 at all. If the determination result in step SP5 is “NO”, that is, if any information is already recorded on the optical disc 2, the controller 43 proceeds to step SP6.

  In step SP6, the controller 43 generates a collimating lens adjustment signal for moving the collimating lens 5 to a position where the RF signal is maximized, supplies the collimating lens adjustment signal to the lens driving circuit 47, and then proceeds to step SP8. Accordingly, the lens driving circuit 47 generates a lens driving signal (pulse signal) for finely adjusting the collimating lens 5 based on the collimating lens adjustment signal supplied from the controller 43 and supplies the lens driving signal to the optical pickup 1.

  On the other hand, if the determination result in step SP5 is “YES”, that is, if no information is recorded on the optical disc 2, the controller 43 proceeds to step SP7. In step SP7, the controller 43 generates a collimating lens adjustment signal for moving the collimating lens 5 to a position where the TE signal is maximized, supplies the collimating lens adjustment signal to the lens driving circuit 47, and then proceeds to step SP8. Accordingly, the lens driving circuit 47 generates a lens driving signal (pulse signal) for finely adjusting the collimating lens 5 based on the collimating lens adjustment signal supplied from the controller 43 and supplies the lens driving signal to the optical pickup 1.

In step SP8, after calculating the lens deviation coefficient K, the controller 43 proceeds to step SP9. The lens deviation coefficient K is calculated based on, for example, the following formula (1).
K = A × (STA−STD) (1)
In Expression (1), A is optimized according to the design parameters of the objective lens 8, for example, the refractive index of the synthetic resin that is the material of the objective lens 8, the focal length of the objective lens 8, the thickness of the objective lens 8, and the like. Coefficient. Further, STA is the number of steps of the stepping motor when the collimating lens 5 is moved to the position adjusted by the above-described processing of steps SP3 and SP6 or SP7. On the other hand, in the optical system of the optical pickup 1 shown in FIGS. 1 and 2, the STD has a collimating lens at a design position where the collimating lens 5 can convert the diverging light beam emitted from the polarization beam splitter 4 into a parallel light beam. This is the number of steps of the stepping motor when 5 is moved.

  In step SP9, the controller 43 determines whether or not it is the first adjustment process of the optical pickup 1 after the optical recording / reproducing apparatus is powered on. If the determination result in step SP9 is “YES”, that is, if the adjustment process of the optical pickup 1 is performed for the first time after the optical recording / reproducing apparatus is turned on, the controller 43 proceeds to step S10. In step SP10, the controller 43 turns on the tracking servo, and then proceeds to step SP11 shown in FIG. On the other hand, when the determination result of step S2P9 is “NO”, that is, when the optical recording / reproducing apparatus is turned on for the second time and thereafter, the controller 43 performs FIG. The process proceeds to step SP11.

  In step SP11, the controller 43 determines whether or not information is recorded on the optical disc 2 at all. If the determination result in step SP11 is “NO”, that is, if some information is already recorded on the optical disc 2, the controller 43 proceeds to step SP12.

  In step SP12, the controller 43 generates a tilt adjustment signal for tilting the objective lens 8 to an angle in the radial direction that minimizes the amplitude of the jitter signal of the RF signal, and supplies the tilt adjustment signal to the lens driving circuit 47, and then step SP14. Proceed to Accordingly, the lens driving circuit 47 generates a lens driving signal for controlling the radial tilt of the objective lens 8 based on the tilt adjustment signal supplied from the controller 43 and supplies the lens driving signal to the optical pickup 1. For details of the processing in step SP12 and the operation of the lens driving circuit 47, refer to, for example, Japanese Patent Application Laid-Open No. 2007-95151.

  On the other hand, if the determination result in step SP11 is “YES”, that is, if no information is recorded on the optical disc 2, the controller 43 proceeds to step SP13. In step SP13, the controller 43 generates a tilt adjustment signal for inclining the objective lens 8 at an angle in the radial direction that maximizes the amplitude of the wobble signal, supplies the tilt adjustment signal to the lens driving circuit 47, and then proceeds to step SP14. Accordingly, the lens driving circuit 47 generates a lens driving signal for controlling the radial tilt of the objective lens 8 based on the tilt adjustment signal supplied from the controller 43 and supplies the lens driving signal to the optical pickup 1. For details of the processing in step SP13 and the operation of the lens driving circuit 47, refer to, for example, Japanese Patent Laid-Open No. 2006-18882.

In step SP14, the controller 43 calculates the lens deviation amount d (see FIG. 20), and then proceeds to step SP15. The lens deviation amount d is calculated based on, for example, the following equation (2).
d [mm] = K × θ [degrees] (2)
In the equation (2), K is a lens deviation coefficient K obtained by the above equation (1). Further, θ is the angle of the objective lens 8 that has been subjected to the radial tilt adjustment in the process of step SP12 or SP13 described above (see FIG. 20).

  In step SP15, the controller 43 generates a bias instruction signal for biasing the objective lens 8 based on the lens deviation amount d obtained in the process of step SP14, and supplies the bias instruction signal to the lens driving circuit 47. Return to step SP1. As a result, the lens driving circuit 47 generates a lens driving signal for biasing the objective lens 8 based on the bias instruction signal supplied from the controller 43 and supplies the lens driving signal to the optical pickup 1.

  At this time, when the optical pickup 1 is in a high temperature environment, the wavelength of the light beam from the semiconductor laser 3 is long, and the thickness of the cover layer of the optical disc 2 is larger than a predetermined value. In the situation where the diverging light beam is incident on the objective lens 8 by moving the collimating lens 5 to correct the “spherical aberration”, the lens driving signal is generated as shown in FIG. As shown, the signal corresponds to a method in which the objective lens 8 is tilted about the principal point 8b and biased in the direction in which the flange 8a is lowered.

  On the other hand, when the optical pickup 1 is in a low temperature environment, the wavelength of the light beam from the semiconductor laser 3 is short, and the thickness of the cover layer of the optical disc 2 is smaller than a predetermined value. In a situation where the convergent light beam is incident on the objective lens 8 by moving the collimating lens 5 to correct the “aberration”, the lens driving signal is shown in FIG. Thus, the signal corresponds to a method of tilting the objective lens 8 around the principal point 8b and biasing the objective lens 8 in the direction in which the flange 8a rises.

  As a result, in the optical pickup 1, the supplied lens driving signal (current) flows through the track coils 22 a to 22 d, whereby the Lorentz force is generated by Fleming's law and the objective lens 8 constituting the movable portion 11 is described above. Corresponding to the first or second method, it is biased in the tracking direction.

  Here, FIG. 21 is a diagram illustrating an example of the relationship between the number of steps of the collimating lens 5 and the coefficient K. In FIG. In the example of FIG. 21, the optical pickup 1 is designed such that when the number of steps of the collimating lens 5 is 200, the coefficient K is 0, that is, a parallel light beam is emitted from the collimating lens 5. When the optical pickup 1 is placed in a high temperature environment, the number of steps of the collimating lens 5 becomes greater than 200 steps, and the value of the coefficient K becomes a positive value, that is, the diverging light beam from the collimating lens 5. Is emitted. On the other hand, when the optical pickup 1 is placed in a low temperature environment, the number of steps of the collimating lens 5 becomes smaller than 200 steps, and the value of the coefficient K becomes a negative value. Is emitted.

  FIG. 22 is a diagram showing an example of the relationship between the number of steps of the collimating lens 5 and the amount of deviation d of the objective lens 8 when the objective lens 8 is subjected to radial tilt adjustment by 0.4 degrees. In the example of FIG. 22, when the number of steps of the collimating lens 5 is 200, a parallel light beam is emitted from the collimating lens 5 and the deviation d of the objective lens 8 is 0, that is, the optical pickup 1 is not deviated. Designed. When the optical pickup 1 is placed in a high temperature environment, the number of steps of the collimating lens 5 becomes greater than 200 steps, and the diverging light beam is emitted from the collimating lens 5, so that the deviation amount d of the objective lens 8 is d. Is a positive value. On the other hand, when the optical pickup 1 is placed in a low temperature environment, the number of steps of the collimating lens 5 becomes smaller than 200 steps, and a convergent light beam is emitted from the collimating lens 5, so that the amount of deviation d of the objective lens 8 is d. Is a negative value.

  If the determination result in step SP1 shown in FIG. 17 is “NO”, that is, if the optical recording / reproducing apparatus of this example has already been turned on, the controller 43 proceeds to step SP16 shown in FIG. move on. In step SP16, the controller 43 determines whether or not the position of the collimating lens 5 needs to be readjusted. This determination is made, for example, when the temperature of the optical pickup 1 detected by a temperature sensor (not shown) attached to the optical pickup 1 is detected when the optical recording / reproducing apparatus is turned on. This is based on whether or not the temperature has changed more than a predetermined temperature (increase or decrease).

  If the determination result in step SP16 is “YES”, that is, if the position of the collimating lens 5 needs to be readjusted, the controller 43 proceeds to step SP17. In step SP17, the controller 43 determines whether or not no information is recorded on the optical disc 2. If the determination result in step SP17 is “NO”, that is, if some information is already recorded on the optical disc 2, the controller 43 proceeds to step SP18.

  In step SP18, the controller 43 generates a collimating lens adjustment signal for moving the collimating lens 5 to a position where the amplitude of the jitter signal of the RF signal is minimized, and supplies the collimating lens adjustment signal to the lens driving circuit 47, which is shown in FIG. Proceed to step SP8. Accordingly, the lens driving circuit 47 generates a lens driving signal (pulse signal) for finely adjusting the collimating lens 5 based on the collimating lens adjustment signal supplied from the controller 43 and supplies the lens driving signal to the optical pickup 1.

  On the other hand, if the determination result in step SP17 is “YES”, that is, if no information is recorded on the optical disc 2, the controller 43 proceeds to step SP19. In step SP19, the controller 43 generates a collimating lens adjustment signal for moving the collimating lens 5 to a position where the amplitude of the wobble signal is maximized, supplies the collimating lens adjustment signal to the lens driving circuit 47, and then proceeds to step SP8 shown in FIG. move on. Accordingly, the lens driving circuit 47 generates a lens driving signal (pulse signal) for finely adjusting the collimating lens 5 based on the collimating lens adjustment signal supplied from the controller 43 and supplies the lens driving signal to the optical pickup 1. If the determination result in step SP16 is “NO”, that is, if there is no need to readjust the position of the collimating lens 5, the controller 43 does nothing and returns to step SP1 shown in FIG.

  As described above, according to the first embodiment of the present invention, the collimator lens 5 is moved to correct the spherical aberration, and the objective lens 8 is inclined with respect to the optical axis direction to correct the coma aberration. The objective lens 8 is deflected by a lens deviation amount d in a direction orthogonal to the optical axis direction based on the moving distance (number of steps) of 5 and the angle θ of the objective lens 8 with respect to the optical axis direction.

  Therefore, by moving the collimating lens 5 in order to correct the “spherical aberration based on the structure of the optical disk”, the converged or diverged light beam is incident on the objective lens 8 made of synthetic resin. 8 can be sufficiently corrected even when the tilt characteristic of 8 is greatly changed and the objective lens 8 is tilted in order to correct the coma based on the warp of the optical disk 2 or the like. In particular, when the optical pickup 1 is in a high temperature (for example, 75 ° C.) environment, the wavelength of the light beam emitted from the light source of the semiconductor laser 3 varies toward the long wavelength side, and the thickness of the cover layer of the optical disc 2 is a predetermined value. Even when the thickness is larger, the coma based on the warp of the optical disk 2 can be sufficiently corrected. As a result, the light beam emitted from the semiconductor laser 3 is irradiated perpendicularly to the information recording surface of the optical disc 2, so that information can be recorded on or reproduced from the optical disc 2.

Embodiment 2. FIG.
In the first embodiment described above, the example in which the lens deviation amount d is calculated according to the moving distance of the collimating lens 5 (the number of steps of the stepping motor) has been described, but the present invention is not limited to this. For example, a temperature sensor is attached to the optical pickup 1 in advance in order to adjust the output power of the semiconductor laser 3. The temperature of the optical pickup 1 and the amount of spherical aberration generated are in a proportional relationship. Therefore, the lens deviation amount d may be calculated based on the temperature of the optical pickup 1.

Embodiment 3 FIG.
In the first embodiment described above, an example in which the adjustment of the inclination of the objective lens 8 and the adjustment of the deviation amount d are performed separately is shown, but the present invention is not limited to this. For example, the relationship between the tilt of the objective lens 8 and the amount of deviation d is obtained in advance, for example, the controller 43 includes a storage unit storing a table corresponding to the above relationship, and after the tilt of the objective lens 8 is adjusted, The deflection amount d may be obtained by referring to the table, and the objective lens 8 may be biased according to the obtained deflection amount d. Further, when the objective lens 8 is tilted, a mechanism may be provided so that the objective lens 8 is biased by a preset bias amount d along with the tilt.

  For example, as shown in FIG. 23, the rotation center of the objective lens 8 is provided below the objective lens 8, as shown in FIG. 24, the rotation center of the objective lens 8 is provided above the objective lens 8, or As shown in FIG. 25, the center of rotation of the objective lens 8 may be provided on the left side of the objective lens 8. The example of FIG. 23 is advantageous when the optical pickup 1 is in a high temperature environment, the wavelength of the light beam from the semiconductor laser 3 is long, and the thickness of the cover layer of the optical disc 2 is greater than a predetermined value (first situation). It is a simple configuration. On the other hand, in the example of FIG. 24, when the optical pickup 1 is in a low temperature environment, the wavelength of the light beam from the semiconductor laser 3 is short, and the thickness of the cover layer of the optical disc 2 is smaller than a predetermined value (second situation). This is an advantageous configuration. In addition, the example of FIG. 25 can deal with both the first situation and the second situation.

Embodiment 4 FIG.
In the first embodiment described above, an example in which the present invention is applied to an optical recording / reproducing apparatus equipped with an optical pickup 1 including an objective lens 8 made of a synthetic resin has been described. However, the present invention is not limited to this. The present invention can also be applied to an optical recording / reproducing apparatus equipped with an optical pickup equipped with an objective lens made of glass under certain conditions. That is, when recording or reproducing information on a so-called multilayer disc having three or more information recording surfaces, the distance between the light incident surface and the information recording surface closest to the light incident surface, the light incident surface, Since there is a large difference in the distance to the information recording surface farthest from the light incident surface, the correction amount of the above-mentioned “spherical aberration based on the structure of the optical disc” of the optical pickup in accordance with the selected information recording surface also increases. . As a result, when recording or reproducing information on a multilayer disk, the amount of movement of the collimator lens is larger than when recording or reproducing information on an optical disk having two or less layers. Even if it is used, it is meaningful to apply the present invention.

As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and the design can be changed without departing from the scope of the present invention. Is included in the present invention.
For example, in the first embodiment described above, an example in which the lens deviation coefficient K is calculated after the fine adjustment of the position of the collimating lens 5 is shown, but the present invention is not limited to this. It may be calculated.
In addition, each of the above-described embodiments can divert each other's technology as long as there is no particular contradiction or problem in its purpose and configuration.

Claims (8)

A collimating lens capable of converting a light beam from a light source into a parallel light beam and changing the convergence and divergence state of the light beam moving and passing in the optical axis direction, and collecting the light beam from the collimating lens on an optical recording medium. An optical pickup adjustment method including an objective lens that emits light,
Moving the collimating lens to correct spherical aberration;
Tilting the objective lens with respect to the optical axis direction to correct coma,
The method of adjusting an optical pickup, comprising: biasing the objective lens based on a moving distance of the collimator lens and an angle of the objective lens with respect to the optical axis direction.   The method of adjusting an optical pickup according to claim 1, wherein the objective lens is made of a synthetic resin.   The method of adjusting an optical pickup according to claim 1, wherein the optical recording medium has a plurality of information recording surfaces.   4. The method of adjusting an optical pickup according to claim 1, wherein the optical recording medium includes a Blu-ray disc. A collimating lens that converts a light beam from a light source into a parallel light beam, and that can change the convergence and divergence state of the light beam that moves in the direction of the optical axis,
An objective lens for condensing the light beam from the collimating lens on an optical recording medium;
The collimating lens is moved to correct spherical aberration, the objective lens is tilted with respect to the optical axis direction to correct coma aberration, and the moving distance of the collimating lens and the optical axis direction of the objective lens are An optical recording / reproducing apparatus comprising: control means for biasing the objective lens based on an angle.   The optical recording / reproducing apparatus according to claim 5, wherein the objective lens is made of a synthetic resin.   The optical recording / reproducing apparatus according to claim 5, wherein the optical recording medium has a plurality of information recording surfaces.   The optical recording / reproducing apparatus according to claim 5, wherein the optical recording medium includes a Blu-ray disc.

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