JP2014116041A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device capable of simply inclining a lens holder in setting control action for detecting and correcting an optical offset component.SOLUTION: In setting control performed whenever an optical disc D is loaded, a lens holder 15 energized by a tracking coil Ct is moved in a radial direction (Rad), and then the lens holder 15 energized by a focus coil Cf is moved downward. At this time, a lower contact part 15b of the lens holder 15 touches a regulation part 7 and the lens holder 15 is inclined. In this state, an offset component due to random light can be accurately detected without receiving return light by a photo detector even when detection light is focused on a surface Ds of the optical disc D.

Description

  The present invention relates to an optical pickup device that performs a focus correction operation and a tracking correction operation, and more particularly to an optical pickup device that detects an offset component by tilting a lens holder when a disk is loaded.

  An optical pickup device that reproduces information recorded on various optical discs such as a CD and a DVD has an objective lens that focuses detection light on a recording surface of the disc, and a lens holder that holds the objective lens.

  The optical pickup device is provided with a focus correction mechanism that moves the lens holder in the optical axis direction of the objective lens, and the focal point of the detection light condensed from the objective lens toward the recording surface of the disk is on the recording surface. A focus correction operation is performed so as to match. In addition, a tracking correction mechanism for moving the lens holder in a radial direction orthogonal to the optical axis is provided, and a tracking correction operation for causing the focal point of the detection light to follow the recording track on the recording surface of the disk is performed.

  In the optical pickup device, a light receiving element that detects reflected light reflected by the recording surface of the disc is provided, and information is reproduced based on the light reception detection output by the light reception element, and based on the light reception detection output. Thus, a focus error signal and a tracking error signal are detected. In the servo control unit, the focus servo circuit, and the tracking servo circuit, operation control of the focus correction mechanism and the tracking correction mechanism is performed based on the focus error signal and the tracking error signal.

  However, in an actual optical pickup device, there is a problem that an offset component unrelated to an error signal resulting from the relative position between the objective lens and the recording surface of the disc is superimposed on the focus error signal and the tracking error signal. If this offset component is excessive, the focus correction operation and the tracking correction operation are not accurately performed, and a correction operation error is likely to occur.

  The offset component includes an electrical offset component caused by an electric circuit and an optical offset component caused by detection light emitted from the light emitting element being reflected by, for example, a metal part other than the recording surface of the disk and entering the light receiving element. Can be divided roughly. The electric offset component can be corrected by an electric circuit. For example, it is possible to solve the problem by monitoring the light reception signal from the light receiving element in a state where the operation of the light emitting element that generates the detection light is stopped, and calculating the electrical offset component based on the monitored value.

  The light offset component is set so that the detection light is not focused on the recording surface while the light emitting element is operating, and the light is monitored by the light receiving element when the detection light does not return from the recording surface. However, it is possible to take measures by calculating the optical offset component from the monitored value.

  Conventionally, immediately after a new disk is loaded, the focus drive mechanism is operated to move the lens holder away from the disk so that the recording light does not focus on the recording surface. The above countermeasure is taken by forcibly setting a state in which the reflected light does not return to the light receiving element, and monitoring the light reception detection output from the light receiving element at this time.

  However, the return light from the disk may not be completely erased only by moving the lens holder away from the disk. For example, when the lens holder is moved in a direction away from the disk, if the focal point of the detection light coincides with the surface of the cover layer of the disk by chance, a lot of light is reflected from this surface and the light receiving element And the light receiving component is erroneously detected as a light offset component. As a result, the optical offset component is corrected with an incorrect correction value.

  In the disk device described in Patent Document 1 below, when the lens holder is moved to the bottom dead center, the lens holder is tilted so that the reflected light from the surface of the disk cover does not return to the light receiving element. ing.

  However, Patent Document 1 does not explain how to tilt the lens holder. If the lens holder is tilted using a focus correction mechanism, tracking correction mechanism, or other correction mechanism, a large amount of correction current is required for the operation, and the lens holder is supported. An excessive strain is generated in the elastic support member, and fatigue is accumulated in the elastic support member.

JP 2002-222530 A

  The present invention solves the above-mentioned conventional problems, and the lens holder can be tilted without giving excessive distortion to the elastic support member, and the return light from the disk cover surface is detected by the light receiving element. It is an object of the present invention to provide an optical pickup device that can prevent the occurrence of the error and perform an accurate offset correction.

The present invention relates to a pickup base, a lens holder on which an objective lens facing the disk is mounted, an elastic support member that operably supports the lens holder with respect to the pickup base, and the lens holder to light of the objective lens. A light having a focus correction mechanism that moves in the axial direction, a tracking correction mechanism that moves the lens holder in a radial direction that intersects the optical axis direction, and a servo control unit that controls the focus correction mechanism and the tracking correction mechanism In the pickup device,
When the tracking mechanism is controlled and the lens holder is moved in the radial direction by a distance exceeding the tracking correction range, a regulating portion that faces the lower part on one side of the lens holder in the radial direction from below. Is provided,
In the servo control unit, the tracking mechanism is controlled to move the lens holder in a radial direction by a distance exceeding the tracking correction range, and further move the lens holder downward so that the lower portion of the lens holder and the restriction are moved. Setting control for tilting the lens holder is performed with the contact portion with the portion as a fulcrum.

  The optical pickup device of the present invention can tilt the lens holder simply by moving the lens holder in the radial direction and moving the lens holder downward. Even when the surface is focused, it is easy to prevent the return light from the cover surface from being detected by the light receiving element.

  In the present invention, when the setting control is being performed, offset correction of a focus drive signal that operates the focus correction mechanism is performed. Furthermore, when the setting control is performed, offset correction of the tracking drive signal that operates the tracking correction mechanism is performed.

  In the present invention, it is preferable that a distance by which the lens holder is moved downward by the focus mechanism is within a focus correction range when the setting control is performed.

  Furthermore, when the setting control is performed, it is preferable that a distance by which the lens holder is moved beyond the tracking correction range by the tracking mechanism is equal to or less than an absolute value of a movable region in the focus correction range.

  With the above means, the distance for moving the lens holder in the optical axis direction and the radial direction during setting control can be shortened, and excessive stress can be avoided from acting on the elastic support member.

  In the present invention, the elastic member is an elastic body wire extending in a tangential direction perpendicular to both the optical axis direction and the radial direction, and a section modulus in the optical axis direction and a cross section in the radial direction of the elastic body wire. The coefficients are preferably the same.

  According to the present invention, setting control for tilting the lens holder can be performed only by driving the lens holder in the radial direction and the downward direction using the focus correction mechanism and the tracking correction mechanism.

  Further, since it is not necessary to increase the distance of movement of the lens holder in the two directions, an excessive driving current is not required, and the distortion of the elastic support member is not excessive.

The perspective view which shows the optical pick-up apparatus of embodiment of this invention, A circuit block diagram showing a part of an optical pickup device and a control circuit associated therewith, Operation explanatory diagram of the optical pickup device, Operation explanatory diagram of the optical pickup device, Illustration of focus error signal,

  The optical pickup device of the present invention is for reproducing information recorded on the recording surface of various optical disks such as CDs and DVDs, or writing information on the recording surface.

  The optical disc D shown in FIGS. 2 to 4 is a CD. In the CD optical disk D, information represented by a plurality of pits is recorded on a recording track set on the recording surface Dd. The surface of the recording surface Dd is covered with a transparent resin cover Dc. In CD, the thickness Td of the cover Dc is about 1.2 mm. The disk device loaded with the optical disk D is provided with a spindle motor and a turntable rotated by the spindle motor, and the center hole of the optical disk D is clamped to the turntable.

  The optical pickup device 1 according to the embodiment shown in FIGS. 1 to 4 is provided with a moving base 2. The disk device is provided with a guide mechanism, and the moving base 2 is guided along a recording surface Dd of the optical disk so as to be reciprocally movable in a radial direction (Rad), which is a radial direction, and by a feed mechanism having a screw shaft or the like. The moving base 2 is moved.

  A pickup unit 10 shown in FIG. 1 is mounted on the moving base 2. The pickup unit 10 has a pickup base 11. The pickup base 11 is made of sheet metal and is fixed to the moving base 2. An inclination adjusting mechanism is provided between the moving base 2 and the pickup base 11, and the pickup unit 10 can be fixed on the moving base 2 with variable inclination.

  As shown in FIG. 1, a support 12 is fixed to the pickup base 11, and a central portion 13 a of a support substrate 13 is fixed to the back of the support 12. The base of the elastic wire 14 is fixed to the support substrate 13. Two elastic wires 14 are fixed to both left and right ends of the support substrate 13, and a total of four elastic wires 14 constitute an elastic support member. The elastic wires 14 pass through the opening 12a formed in the support 12 and extend in parallel to each other in the tangential direction (Tan) which is the tangential direction of the optical disc D.

  The pickup unit 10 has a lens holder 15. The lens holder 15 is made of synthetic resin or light metal. Support protrusions 15a extending in the radial direction (Rad) are integrally formed on the left and right side portions of the lens holder 15, and the tip portions of the elastic wires 14 are fixed to the support protrusions 15a, respectively. The lens holder 15 is supported by the four elastic wires 14 and is movable in an optical axis direction (F) and a radial direction (Rad), and in a direction having an angle with respect to the optical axis direction and the radial direction.

  The elastic wire 14 is made of steel and has a true circular cross section. Therefore, the section modulus in the optical axis direction (F) of the elastic body wire 14 is the same as the section coefficient in the radial direction (Rad). Therefore, when the lens holder 15 moves in the optical axis direction (F) and when it moves in the radial direction (Rad), the elastic modulus is the same, and the stress for the same strain amount is also the same. The effect on fatigue is the same.

  A focus coil Cf is wound around the lens holder 15. Tracking coils Ct are provided on both side surfaces of the lens holder 15 facing the tangential direction (Tan). Two tracking coils Ct are fixed to each side surface.

  As shown in FIG. 1, a pair of yokes 11a and 11b are integrally bent to a pickup base 11, and a magnet M is fixed to each of the yokes 11a and 11b. Each magnet M faces both the focus coil Cf and the tracking coil Ct mounted on the lens holder 15.

  The focus coil Cf and the magnet M constitute a focus correction mechanism. In the focus correction mechanism, the lens holder 15 is driven in the optical axis direction (F) by the current flowing in the radial direction (Rad) in the focus coil Cf and the magnetic field from the magnet M.

  The tracking coil Ct and the magnet M constitute a tracking correction mechanism. In the tracking correction mechanism, the lens holder 15 is driven in the radial direction (Rad) by the magnetic field flowing in the optical axis direction (F) by the tracking coil Ct and the magnetic field from the magnet M.

  As shown in FIG. 2, tracking stoppers 6 and 6 are provided on both sides of the lens holder 15 in the radial direction (Rad). The tracking stoppers 6 and 6 are provided on either the moving base 2 or the pickup base 11. The tracking stoppers 6 and 6 regulate the lens holder 15 so as not to move excessively in the radial direction (Rad).

  As shown in FIG. 2, the lens holder 15 is integrally formed with a lower contact portion 15b below the end portion on either side in the radial direction (Rad). In FIG. 2, the lens holder 15 is in a neutral position in the radial direction (Rad). At this time, the restricting portion 7 faces the diagonally lower side of the lower contact portion 15b of the lens holder. The restricting portion 7 is formed integrally with either the moving base 2 or the pickup base 11. Alternatively, the restricting portion 7 is formed as a separate part and is fixed to the moving base 2 or the pickup base 11.

  As shown in FIG. 1, the objective lens 16 is held by the lens holder 15. In each drawing, an optical axis center line O passing perpendicularly through the center of the effective diameter of the objective lens 16 is shown. As shown in FIG. 2, the moving base 2 is provided with a reflecting member 3, and the optical axis center line O faces the reflecting surface of the reflecting member 3. The reflection direction of the reflection surface is a tangential direction (Tan), and the light emitting / receiving unit 4 is mounted at a position spaced from the reflection surface in the tangential direction.

  The detection light emitted from the light emitting element provided in the light emitting / receiving unit 4 is reflected by the reflecting surface of the reflecting member 3 and condensed on the recording surface Dd of the optical disc D by the objective lens 16. The reflected light reflected from the recording surface Dd is captured by the objective lens 16, reflected by the reflecting surface of the reflecting member 3, and detected by the light receiving element provided in the light emitting / receiving unit 4.

  As shown in FIG. 2, in the circuit unit 20 associated with the optical pickup device 1, the light reception detection output detected by the light receiving element of the light emitting / light receiving unit 4 is given to the RF amplifier 21. Of the received light detection output, a reproduction output signal optically influenced by the pit information recorded on the recording surface Dd of the optical disc D is sent from the RF amplifier 21 to a demodulator (not shown).

  The focus error signal in the received light detection output is given to the focus servo circuit 22, and the focus servo circuit 22 generates a focus drive signal. The focus drive signal is converted into a current by the drive amplifier 23 and applied to the focus coil Cf. The tracking error signal in the received light detection output is given to the tracking servo circuit 24, and the tracking servo circuit 24 generates a tracking drive signal. The tracking drive signal is converted into a current by the drive amplifier 25 and applied to the tracking coil Ct.

  A servo control unit 26 is provided in the circuit unit 20. The focus servo circuit 22 and the tracking servo circuit 24 are controlled by a servo control unit 26.

  In FIG. 2, the focal point Pf of the detection light condensed by the objective lens 16 coincides with the recording surface Dd of the optical disc D. When the optical disc D rotates and the recording surface Dd of the optical disc D swings up and down, the focal point Pf does not coincide with the recording surface Dd. When this is given to the focus servo circuit 22 as a focus error signal, the focus servo circuit 22 generates a focus drive signal for making the in-focus point Pf coincide with the recording surface Dd, and the focus drive signal is converted into a current so that the focus coil. Is given to Cf. As a result, the lens holder 15 is moved in the optical axis direction (F), and the focal point Pf is corrected so as to coincide with the recording surface Dd.

  In the light emitting / receiving unit 4, the focus error signal is detected by a beam size method or the like. FIG. 5 shows a focus error signal Ef when the optical disk D moves up and down with the lens holder 15 not moving. When the focal point Pf coincides with the recording surface Dd, the focus error signal Ef reaches the in-focus level E0.

  The focus level E0 of the focus error signal Ef is preferably set to a reference potential V0 such as zero potential. However, in the actual optical pickup device 1, the offset signal Δ is superimposed on the focus error signal Ef, and the focus level E0 often deviates from the reference potential V0. The offset signal Δ is roughly classified into an electrical offset component caused by the circuit unit 20 and an optical offset component mainly composed of stray light reflected from the detection surface other than the recording surface Dd.

  The electrical offset component stops the emission of the detection light from the light emitting element of the light emitting / receiving unit 4 in a state where the optical disc D is mounted, and the light receiving detection received by the light receiving element of the light emitting / receiving unit 4 at this time The output can be detected by analyzing the servo control unit 26. The correction value for subtracting the electrical offset component from the servo control unit 26 is given to the focus servo signal 22, so that the electrical offset component can be brought close to elimination.

  The optical offset component is a light receiving component other than the reflected light including the reproduction signal component reflected from the recording surface Dd when the recording surface Dd and the focal point Pf coincide with each other. For example, the optical offset component is emitted upward from the objective lens 16. The detection light is generated when the light receiving element receives stray light that is reflected when it hits a metal part or the like in the disk device.

  Therefore, in order to detect this optical offset component, the detection light is emitted from the light emitting element of the light emitting / receiving unit 4 with the optical disc D loaded, and the focal point Pf of the detection light is the recording surface Dd of the optical disc D. It is necessary to set the posture of the lens holder 15 so as not to coincide with. By analyzing the light reception detection output detected by the light receiving element when the focal point Pf does not coincide with the recording surface Dd, the servo control unit 26 analyzes the light offset component. By providing the focus servo signal 22 with a correction value for subtracting the optical offset component from the servo control unit 26, the optical offset component can be brought close to elimination.

  The correction for eliminating the electrical offset component and the correction for eliminating the optical offset component are performed every time, for example, when a new optical disc D is loaded on the turntable and before the information reproduction operation. . Further, when the power of the disk device is turned off while the optical disk D is loaded, it is performed every time the power is turned on again.

  Further, when the optical disc D rotates, the focal point Pf of the detection light and the recording track recorded on the recording surface Dd of the optical disc D may be misaligned. In the light emitting / receiving unit 4, a tracking error signal corresponding to the amount of deviation between the focal point Pf and the recording track is detected by the three beam method or the like, and this tracking error signal is given to the tracking servo circuit 24. In the tracking servo circuit 24, a tracking drive signal corresponding to the amount of positional deviation between the focal point Pf and the recording track is generated and applied to the tracking coil Ct, and the lens holder 15 is driven in the radial direction (Rad). The focal point Pf is corrected so as to follow the recording track.

  Since the electrical offset component and the optical offset component are also superimposed on the tracking error signal, it is necessary to perform processing for removing the offset signal from the tracking error signal as in the case of the focus error signal. This correction process is basically the same as the correction of the offset signal included in the focus error signal.

  Hereinafter, a setting control operation for detecting the optical offset component when a new optical disk D is loaded or the power of the disk device is turned on again will be described.

  This setting control is mainly executed by the servo control unit 26. First, a first setting control signal is given from the servo control unit 26 to the tracking servo circuit 24. By the first setting control signal, a setting current is applied from the tracking servo circuit 24 to the tracking coil Ct, and as shown in FIG. 3, the lens holder 15 is moved in the radial direction (Rad) by the distance Zt. By this movement, the lower contact portion 15 b of the lens holder 15 faces the upper portion of the restricting portion 7.

  Thereafter, a second setting control signal is given from the servo control unit 26 to the focus servo circuit 22, and a setting current is given from the focus servo circuit 22 to the focus coil Cf. As shown in FIG. Moved to. In the middle of this movement, the lower contact portion 15b and the restricting portion 7 come into contact, and the lens holder 15 tilts with the contact portion between the lower contact portion 15b and the restricting portion 7 as a fulcrum, and the optical axis center of the objective lens 16 The line O is inclined by an angle θ with respect to the perpendicular of the recording surface Dd of the optical disc D.

  In this state, since the focal point Pf of the detection light and the recording surface Dd do not coincide with each other, the reflected light from the recording surface Dd is not received by the light receiving element of the light emitting / receiving unit 4. Furthermore, even if the focal point Pf may coincide with a reflective surface other than the recording surface Dd of the optical disc D, for example, even if the focal point Pf may coincide with the surface Ds of the cover Dc of the optical disc D, Since the center line of the reflected light does not return toward the optical axis center line O of the objective lens 16, it is possible to prevent unnecessary reflected light of the detection light from being received by the light receiving element.

  As shown in FIG. 4, when setting control in which the attitude of the lens holder 15 is tilted is performed, a light reception detection output from the light receiving element is given to the servo control unit 26, and correction for removing the optical offset component is performed. The value is calculated.

  As shown in FIG. 2, the tracking correction range (± St) in which the lens holder 15 is moved in the radial direction (Rad) in order to eliminate the tracking error when performing a normal reproduction operation on the optical disc D is maximum. Is about ± 0.4 mm. As long as the lens holder 15 moves within this range, the lower contact portion 15b of the lens holder 15 does not face the upper portion of the restricting portion 7. Therefore, even when the lens holder 15 is moved downward in the radial direction (Rad) in the maximum range of the tracking correction range (± St) and the lens holder 15 is moved downward for the focus correction operation, the lower holder The contact portion 15b does not hit the restricting portion 7, and the lens holder 15 is not tilted by the restricting portion 7 during a normal tracking correction operation or focus correction operation.

  However, as shown in FIG. 3, the moving distance Zt when the lens holder 15 is moved in the radial direction (Rad) by the first setting control signal is set to be longer than the tracking correction range St in one direction. Thus, when the lens holder 15 moves beyond the tracking correction range St, the lower contact portion 15b and the restricting portion 7 face each other vertically.

  As shown in FIG. 2, when a normal reproduction operation is performed on the optical disc D, the lens holder 15 moves up and down along the optical axis direction (F) in order to eliminate the focus error. The focus correction range (± Sf) is about ± 1.0 mm. This is longer than ± 0.4 mm which is the absolute value of the moving distance of the tracking correction range (± St).

  As shown in FIG. 3, the movement distance Zt when the lens holder 15 is moved in the radial direction (Rad) is set to a distance equivalent to the focus correction range (± Sf) by the first setting control signal. It is preferable.

  The elastic body wire 14 constituting the elastic support member has the same section modulus in the optical axis direction (F) and the radial direction (Rad). Therefore, in the setting control operation shown in FIGS. 3 and 4, the distance Zt when the lens holder 15 moves in the radial direction (Rad) is set to be the same as the absolute value of the movement distance of the focus correction range (± Sf). As a result, it is possible to avoid an excessive stress that is larger than the stress acting on the elastic wire 14 during the normal focus correction operation.

  That is, the movement distance Zt of the lens holder 15 in the radial direction (Rad) in the setting control shown in FIG. 3 is preferably a value that exceeds the tracking correction range St and is equal to or less than the focus correction range Sf.

  Next, as shown in FIG. 4, the lens holder 15 is lowered by the second setting control signal, and the lowering distance Zf of the lens holder 15 necessary for setting the lens holder to the tilted posture is also the focus correction. It is preferable that the distance be equal to or shorter than the moving distance in the range Sf. By setting the descending distance Zf during the setting control to be equal to or less than the focus correction range Sf in the normal reproduction operation, the stress during the normal focus correction operation is applied to the elastic body wire 14 when performing the setting control shown in FIG. Excessive stress that does not act is eliminated, and fatigue of the elastic body wire 14 can be reduced.

  Since the lens holder 15 is tilted when it hits the restricting portion 7, the optical axis center line O of the objective lens 16 can be sufficiently tilted even when the descending distance Zf is set to be equal to or smaller than the focus correction range Sf. In the optical pickup device 1 having a normal size, if the angle θ of inclination of the optical axis center line O shown in FIG. 4 is set to 1 degree or more, and preferably set to 3 degrees or more, the focal point Pf is assumed to be the cover Dc. Even if it matches the surface Ds, the reflected light is not detected by the light receiving element of the light emitting / receiving unit 4.

DESCRIPTION OF SYMBOLS 1 Optical pick-up apparatus 2 Moving base 3 Reflecting member 4 Light emission / light-receiving unit 7 Control part 10 Pickup unit 11 Pickup base 12 Support body 14 Elastic wire 15 Lens holder 15a Support protrusion 15b Lower contact part 16 Objective lens 20 Circuit part 22 Focus servo Circuit 24 Tracking servo circuit 26 Servo controller Cf Focusing coil Ct Tracking coil D Optical disk Dd Recording surface Ds Surface M Magnet O Optical axis center line Pf Focus point F Optical axis direction Rad Radial method Tan Tangental direction Sf Focus correction range St Tracking correction range Zt Travel distance Zf Descent distance

Claims (6)

A pickup base, a lens holder on which an objective lens facing the disk is mounted, an elastic support member that operably supports the lens holder with respect to the pickup base, and the lens holder is moved in the optical axis direction of the objective lens In an optical pickup device comprising: a focus correction mechanism to be moved; a tracking correction mechanism for moving the lens holder in a radial direction intersecting an optical axis direction; and a servo control unit for controlling the focus correction mechanism and the tracking correction mechanism.
When the tracking mechanism is controlled and the lens holder is moved in the radial direction by a distance exceeding the tracking correction range, a regulating portion that faces the lower part on one side of the lens holder in the radial direction from below. Is provided,
In the servo control unit, the tracking mechanism is controlled to move the lens holder in a radial direction by a distance exceeding the tracking correction range, and further move the lens holder downward so that the lower portion of the lens holder and the restriction are moved. An optical pickup device characterized in that setting control for tilting the lens holder is performed with a contact portion with the support portion as a fulcrum.   The optical pickup device according to claim 1, wherein offset correction of a focus drive signal that operates the focus correction mechanism is performed when the setting control is performed.   The optical pickup device according to claim 2, wherein offset correction of a tracking drive signal for operating the tracking correction mechanism is performed when the setting control is performed.   4. The optical pickup device according to claim 1, wherein when the setting control is performed, a distance by which the lens holder is moved downward by the focus mechanism is within a focus correction range. 5.   The distance by which the lens holder is moved beyond the tracking correction range by the tracking mechanism when the setting control is performed is equal to or less than the absolute value of the movable region in the focus correction range. The optical pickup device described.   The elastic member is an elastic wire extending in a tangential direction orthogonal to both the optical axis direction and the radial direction, and the cross section coefficient in the optical axis direction and the cross section coefficient in the radial direction of the elastic body wire are the same. The optical pickup device according to claim 5.

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