JP2005302243A - Optical pickup device and light source unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device and a light source unit capable of properly recording and/or reproducing information even when a light source unit including two light emitting parts is adopted and even when secular change and environmental change, etc. occur. <P>SOLUTION: Since a light emitting part holder HD is driven to an arbitrary position by an actuator, an axis line L2 of a light flux of a second semiconductor laser LD2 or an axis line L3 of a light flux of a third semiconductor laser LD3 mounted on the holder is aligned on an optical axis of a condensing optical system of the optical pickup device shown in Fig. 1 and thus, an influence by light axis displacement of a light source is avoided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup device and a light source unit, and more particularly to an optical pickup device and a light source unit capable of appropriately recording and / or reproducing information with respect to an optical information recording medium.

  In an optical pickup device that records and / or reproduces information with respect to an optical disc, it is necessary to align optical elements with high accuracy in assembly adjustment. For example, if the optical axis of the objective lens is deviated with respect to the optical axis emitted from the light source, coma aberration that hinders appropriate information recording and / or reproduction may occur. Therefore, in order to reduce the coma aberration of the focused spot imaged on the optical disc, the angle is adjusted during assembly so that the optical axis of the light beam emitted from the light source and the optical axis of the objective lens are within the allowable range. It is carried out.

Incidentally, in recent years, in an optical pickup device capable of recording and / or reproducing information interchangeably with different types of optical disks, a light source unit in which a plurality of light sources having different wavelengths are incorporated in one package has come to be used. (See Patent Document 1). However, when such a light source unit is used, each light source is provided so as to be shifted in a direction perpendicular to the optical axis in the optical pickup device. There is a problem in that the state of the tops in the light fluxes is different, so that the optimum tops cannot be obtained for all the light fluxes. Therefore, in Patent Document 1, a collimator in which a diffraction pattern is formed is provided, and a condensing optical system in which the optical axis gives coma to a light beam from a light source and reaches the optical disk using the diffraction effect. The coma aberration is corrected as a whole.
JP 2001-236680 A

  Here, in the configuration of Patent Document 1, by accurately adjusting the relationship between the light source and the collimator, the light flux from any light source is appropriately condensed on the information recording surface of the optical disc in a state where the coma is suppressed. be able to. However, when the diffraction effect is used, it is difficult to achieve 100% of the diffraction efficiency due to the shape error of the diffraction pattern. Therefore, a light source with higher power is required to compensate for the reduced efficiency, resulting in a high cost. Is also contrary to energy saving.

  Also, if an optical pickup device is used for a long period of time, the positional relationship between the light source and the collimator may deviate slightly due to environmental changes such as vibration, impact, and temperature / humidity depending on the mounting condition, and coma aberration given by the diffraction effect May fluctuate and coma aberration may increase in the entire condensing optical system. Even when the relationship between the light source and the collimator does not change, the relationship with other optical elements constituting the condensing optical system such as a prism and a mirror shifts, and as a result, the light beam reflected from the information recording surface is detected by light. There is also a possibility that a detection error or the like may be caused because the light does not enter the position where it should be incident. As these measures, when these optical elements are fixed in an optical housing, an adhesive is used, which has excellent environmental characteristics, or a mechanical structure that easily absorbs thermal expansion and contraction and mechanical shock is adopted for an optical pickup device or the like. However, there is a difference between solids in the produced optical pickup device, and it is difficult to fundamentally eliminate the problem in all cases.

  The present invention has been made in view of such problems, and even when a light source unit including two light emitting units is employed, or even when aging or environmental changes occur, information recording and / or appropriate An object of the present invention is to provide an optical pickup device and a light source unit capable of reproducing.

The optical pickup device according to claim 1 includes a light source unit, and a condensing optical system including an objective lens that condenses a light beam from the light source unit on an information recording surface of an optical information recording medium, and An optical pickup device configured to record and / or reproduce information by condensing a light beam emitted from a light source onto an information recording surface of the optical information recording medium via the condensing optical system. And
The light source unit integrally incorporates a light emitting unit and an actuator that moves the light emitting unit in an optical axis direction and / or a direction intersecting the optical axis.

  According to the present invention, for example, when a light source unit having a plurality of light emitting units separated by a predetermined distance (for example, two lasers and one package) is used, an optical pickup device is switched along with switching of a light source used for recording or reproduction. The axis of the light beam of the light emitting unit (also referred to as the optical axis) is deviated from the optical axis of the light collecting optical system. The actuator is used to move the light emitting unit to a position where no deviation from the optical axis of the optical information is generated, whereby the light emitted from any of the light emitting units is coupled to the information recording surface of the optical information recording medium. Even when an image spot is generated, astigmatism and coma can be effectively suppressed. Further, for example, when a plurality of information recording surfaces (layers) are provided on one optical information recording medium, the protective layers having different thicknesses are transmitted as the information recording surface used for recording or reproduction is switched. In such a case, it is necessary to form an appropriate condensing spot on the information recording surface.In such a case, the light emitting unit is moved in the optical axis direction to the appropriate position using the actuator, thereby Spherical aberration and the like can be effectively suppressed when the light beam emitted from the light emitting section causes an imaging spot on any information recording surface of the optical information recording medium. Furthermore, even in an optical information recording medium provided with one information recording surface (layer), the thickness of the protective layer varies depending on the position, so-called thickness unevenness may occur. In the optical information recording medium, it is necessary to form an appropriate light condensing spot on the information recording surface through the protective layers having different thicknesses. On the other hand, according to the present invention, the light emitting unit is moved in the optical axis direction to the appropriate position using the actuator, so that the light beam emitted from the light emitting unit can be transmitted to any of the optical information recording media. When an imaging spot is generated on the information recording surface, spherical aberration and the like can be effectively suppressed.

  According to a second aspect of the present invention, in the optical pickup device according to the first aspect of the present invention, a plurality of the light emitting units are provided. The plurality is not limited to two and may be three or four or more.

The optical pickup device according to claim 3 includes a light source unit, and a condensing optical system including an objective lens that condenses a light beam from the light source unit on an information recording surface of an optical information recording medium, and An optical pickup device configured to record and / or reproduce information by condensing a light beam emitted from a light source onto an information recording surface of the optical information recording medium via the condensing optical system. And
The light source unit integrally includes a light emitting unit, a coupling lens that emits a light beam emitted from the light emitting unit and changes the divergence, and an actuator that moves the coupling lens in the optical axis direction. It is characterized by being incorporated.

  According to the present invention, for example, in the case where a plurality of information recording surfaces (layers) are provided on one optical information recording medium, the thickness of the information recording surface is changed according to the switching of the information recording surface used for recording or reproduction. It is necessary to form an appropriate light condensing spot on the information recording surface through the protective layer. In such a case, the coupling lens (for example, a collimator) is moved to an appropriate position using the actuator. When the luminous flux is moved in the optical axis direction, and the light beam emitted from the light emitting section causes an imaging spot on any information recording surface of the optical information recording medium, spherical aberration and the like are effectively suppressed. Can do. Furthermore, even in an optical information recording medium provided with one information recording surface (layer), the thickness of the protective layer varies depending on the position, so-called thickness unevenness may occur. In the optical information recording medium, it is necessary to form an appropriate light condensing spot on the information recording surface through the protective layers having different thicknesses. On the other hand, according to the present invention, the coupling lens is moved in the optical axis direction to the appropriate position using the actuator, so that the light beam emitted from the light emitting unit can be transmitted to any of the optical information recording media. When an imaging spot is generated on the information recording surface, spherical aberration and the like can be effectively suppressed.

According to a fourth aspect of the present invention, there is provided the optical pickup device according to any one of the first to third aspects, further comprising a photodetector that receives a reflected light beam from the information recording surface, and the actuator includes the information recording Since the light emitting unit is driven based on an information signal output from the photodetector in accordance with a reflected light beam from a surface, feedback control is performed without bothering an assembly operator or a user. By automatically controlling the actuator, the light emitting unit can be moved to an appropriate position. In addition, even when the positional interval between the light emitting unit and the coupling lens becomes inappropriate due to secular change or environmental change, or when the optical axis shift between the light emitting unit and the condensing optical system occurs, the information Based on the information signal output from the photodetector in accordance with the reflected light beam from the recording surface, the light emitting unit is moved using the actuator, thereby recording and / or reproducing appropriate information. it can. Note that “movement to an appropriate position” means, for example, the following movement.
(A) If the distance between the light emitting portion and the coupling lens becomes inappropriate, spherical aberration is generated. Since the spherical aberration deteriorates the quality of the information signal obtained from the photodetector, the position of the light emitting unit is moved in the optical axis direction via the actuator in a direction that improves the quality of the information signal. Methods for improving the quality of the information signal include (1) increasing the recorded “amplitude of the information signal” and (2) reducing the jitter of the signal. These can be detected by appropriately processing the information signal obtained via the photodetector. In addition to the above-described (1) and (2), spherical aberration correction methods are described in JP-A-10-214436, JP-A-2004-14039, and International Publication WO02 / 21520. The spherical aberration may be detected using the above-described technique, and the position of the light emitting unit may be moved in the optical axis direction based on the result.
(B) Alternatively, as will be described later in connection with the embodiment of FIG. 7, the positional relationship of the reflected light beam from the information recording surface of the optical information recording medium with respect to the photodetector is set via an actuator so as to be appropriate. The position of the light emitting unit is moved.

  The coupling lens in this specification is an optical element having a function of emitting a divergence angle of a light beam emitted from the light emitting unit as a light beam that is axisymmetrically suppressed about the optical axis. A collimator which is a lens for converting the emitted light beam into a parallel light beam. In addition to a glass or plastic lens, for example, a lens made of a diffraction grating may be used.

The optical pickup device according to claim 5 includes a light source unit and a condensing optical system including an objective lens that condenses a light beam from the light source unit on an information recording surface of an optical information recording medium, and An optical pickup device configured to record and / or reproduce information by condensing a light beam emitted from a light source onto an information recording surface of the optical information recording medium via the condensing optical system. And
The light source unit integrally incorporates a light emitting unit, an optical axis changing element that changes the direction of the axis of a light beam emitted from the light emitting unit, and an actuator that moves the optical axis changing element. And

  In the first aspect of the invention, the light emitting section itself is moved by the actuator. However, wiring for power supply is connected to the light emitting unit, and it is not always appropriate to move the light source in view of reliability and the like. Therefore, in the case of the present invention described in claim 4, an optical axis changing element that changes the direction of the light beam, such as a prism, a mirror, or a diffraction grating, is incorporated in the light source unit, and the light beam whose direction is changed is transmitted from the light source unit. The light is emitted. Therefore, according to the present invention, when the optical axis shift occurs in the light beam emitted from the light source unit, the optical axis changing element is moved by a predetermined amount in advance to the position where it does not occur. As a result, even when the light beam emitted from any of the light emitting portions generates an imaging spot on the information recording surface of the optical information recording medium, astigmatism and coma aberration can be effectively suppressed.

  A collimator or a coupling lens driven in the optical axis direction by an actuator can be incorporated in the light source unit and moved in the optical axis direction, which is caused by a difference in the thickness of the protective layer such as a DVD or CD. It is also possible to appropriately correct spherical aberration, wavelength fluctuation caused when switching light emission when a plurality of light emitting parts are used, and spherical aberration caused by wavelength fluctuation caused by temperature change or emission power change of the light emitting part.

  According to a sixth aspect of the present invention, there is provided the optical pickup device according to the fifth aspect, wherein the optical axis changing element is a mirror, and the actuator rotationally drives the mirror.

  According to a seventh aspect of the present invention, in the optical pickup device of the fifth aspect, the optical axis changing element is a diffraction grating, and the actuator drives the diffraction grating in a direction intersecting the optical axis. And As such a diffractive element, for example, those described in JP-A-2003-329969 can be used.

  An optical pickup device according to an eighth aspect of the present invention includes the optical detector according to any one of the fifth to seventh aspects, further including a photodetector that receives a reflected light beam from the information recording surface, and the actuator includes the information recording Since it is characterized by driving the optical axis changing element based on the information signal output from the photodetector according to the reflected light beam from the surface, without bothering the assembly operator and the user, The actuator can be automatically controlled by feedback control to move the light emitting unit to an appropriate position. Further, even when an optical axis shift occurs between the light emitting unit and the condensing optical system due to secular change or environmental change, the light emitting unit is moved using the actuator based on a signal from the photodetector. As a result, appropriate information can be recorded and / or reproduced.

  A light source unit according to a ninth aspect is used in the optical pickup device according to any one of the first to eighth aspects.

  The optical pickup device according to claim 10 is disposed between a light source, an objective lens that focuses a light beam from the light source on an information recording surface of an optical information recording medium, and the light source and the objective lens. A light collecting optical system including a beam shaping element; and an actuator for driving the beam shaping element, and the light beam emitted from the light source is transmitted to the information on the optical information recording medium via the light collecting optical system. Information is recorded and / or reproduced by focusing light onto a recording surface.

  Depending on the light emission characteristics of the light source, the divergent light beam emitted from the light source may have an elliptical light intensity distribution in the cross section in the direction orthogonal to the optical axis. Can interfere with regeneration. On the other hand, there is a case where a beam shaping element for making the light intensity distribution close to a circular shape is arranged between the light source and the objective lens. However, if the optical axis is shifted from the optical axis of the light source, Since there is a possibility that the intensity distribution is not corrected into a circular shape, positioning with high accuracy is required. Therefore, according to the present invention, the beam shaping element is moved using the actuator to a position where an optical axis deviation does not occur, whereby appropriate information can be recorded and / or reproduced.

  The optical pickup device according to claim 11 includes a light source, a condensing optical system including an objective lens that condenses a light beam from the light source on an information recording surface of an optical information recording medium, and reflection from the information recording surface. A light detector that receives the light beam; and an actuator that drives the light detector; and the light beam emitted from the light source is transmitted to the information recording surface of the optical information recording medium via the condensing optical system. An optical pickup device configured to record and / or reproduce information by condensing, on the basis of an information signal output from the photodetector in response to a reflected light beam from the information recording surface The actuator drives the photodetector in a direction intersecting with a light beam incident on the photodetector.

  According to the present invention, even when a positional relationship between the photodetector and an incident light beam is generated due to a secular change, an environmental change, or the like, the light is applied using the actuator in a direction to eliminate such a shift. The detector can be moved so that appropriate information can be recorded and / or reproduced.

  An optical pickup device according to a twelfth aspect of the present invention is the invention according to any one of the first to eleventh aspects, wherein the actuator includes an electromechanical conversion element, a driving member fixed to one end of the electromechanical conversion element, The movable member is movably held on the drive member and a drive circuit for applying a voltage to the electromechanical conversion element, and the electromechanical conversion element is expanded and contracted according to the voltage applied from the drive circuit. By doing so, the drive member and the movable member are moved relative to each other.

  The actuator used for the above-described applications is required to be extremely compact and have high responsiveness. However, conventionally used voice coil motors generally have a problem of high power consumption, and it is difficult to make the size to be incorporated in a light source unit or the like. On the other hand, stepping motors are generally larger than voice coil motors, and there is a problem that resolution is lowered when trying to provide high responsiveness. The actuator of the present invention satisfies the required characteristics by the above-described configuration.

  More specifically, in the actuator, by applying a driving voltage such as a sawtooth-shaped pulse from the driving circuit to the electromechanical conversion element for a very short time, the electromechanical conversion element is made minute. However, the speed of expansion or contraction can be changed depending on the shape of the pulse. Here, when the electromechanical conversion element is deformed at a high speed in the extending or contracting direction, the movable member does not follow the operation of the driving member due to the inertia of the mass and remains in the same position. On the other hand, when the electromechanical conversion element is deformed in the opposite direction at a slower speed, the movable member moves following the operation of the drive member by the friction force acting therebetween. Therefore, when the electromechanical conversion element repeats expansion and contraction, the movable member can continuously move in one direction. That is, by using the actuator of the present invention having high responsiveness, the movable element connected to the movable member can be moved with a large amount of movement, or can be moved with a small amount of movement. Due to such a configuration, the configuration of the actuator is simple and can be reduced in size, and is further inexpensive.

  In the present invention described above, a light source unit that moves any one of the light emitting unit, the coupling lens, and the optical axis changing element in the optical axis direction or the optical axis orthogonal direction by an actuator is used. A configuration in which two or all of them are moved using an actuator is also possible. That is, when the optical information recording medium is replaced with a different type, two points are necessary: (a) correspondence to different light source wavelengths and (b) correspondence to different protective layer thicknesses. In the case of a light source unit having a plurality of light emitting parts, it is necessary to align the optical axis by moving the light emitting part or the optical axis changing element. As for (b), if the objective lens is used in common, the light emission Correction of spherical aberration by moving the lens or coupling lens is required.

More specifically, in an optical pickup device, an optical information recording medium (for example, BD) having a light source wavelength of 405 nm and a protective layer thickness of 0.1 mm is used, and an optical information recording medium having a light source wavelength of 655 nm and a protective layer thickness of 0.6 mm is used. When recording and / or reproducing information by exchanging with a medium (for example, a DVD), the following measures can be taken.
(1) The light emitting unit is moved in the direction perpendicular to the optical axis so that the DVD light flux is aligned with the optical axis of the condensing optical system, and is moved in the optical axis direction for spherical aberration correction.
(2) The light emitting unit is moved in the direction perpendicular to the optical axis so that the DVD light beam is aligned with the optical axis of the condensing optical system, and the coupling lens is moved in the optical axis direction for spherical aberration correction.
(3) The optical axis changing element is moved so that the luminous flux for DVD coincides with the optical axis of the condensing optical system, and the light emitting part or the coupling lens is moved in the optical axis direction for spherical aberration correction.
The above configuration is included in the scope of the present invention.

  According to the present invention, there is provided an optical pickup device and a light source unit that can appropriately record and / or reproduce information even when a light source unit including two light emitting units is employed, or even when aging or environmental change occurs. Can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an optical pickup device according to the present embodiment that can appropriately record / reproduce information to / from an BD or HD DVD, DVD and CD, which are optical information recording media (also referred to as optical disks) having different protective layer thicknesses. It is a top view which shows a structure schematically. FIG. 2 is a side view of the present embodiment as viewed from the direction of arrow II. In the present embodiment, the condensing optical system includes the objective lens OBJ and the collimator optical system COL. In the present embodiment, a light source unit in which the second semiconductor laser LD2 and the third semiconductor laser LD3 are accommodated in the same package is used. Such a light source unit will be described later with reference to FIG.

  When recording and / or reproducing information on the first optical disc OD1 (for example, BD or HD DVD), the light beam emitted from the semiconductor laser LD1 having a light source wavelength of 380 to 450 nm in the optical pickup device of FIG. The beam shape is shaped by the beam shaping element BS, and further passed through the first diffractive element D1 to be separated into a main beam for recording / reproducing and a sub beam for detecting a tracking error signal, and then reflected by the dichroic beam splitter DBS. The light is reflected by the polarization beam splitter PBS, passes through the collimator optical system COL, and then enters the rising mirror M.

  In FIG. 2, a part of the light beam incident on the rising mirror M is transmitted through the monitor lens ML, then enters the laser power monitor LPM, and is used for monitoring the laser power. On the other hand, the remainder of the light beam incident on the rising mirror M is reflected there, passes through the quarter-wave plate QWP, and then the objective lens OBJ (in this embodiment, it consists of two elements, but one may be used). Then, the light is focused on the information recording surface R1 (the protective layer thickness is 0.1 mm or 0.6 mm) of the optical disk OD1.

  The reflected light beam modulated by the information pits on the information recording surface R1 passes through the objective lens OBJ and the quarter wavelength plate QWP again, is reflected by the rising mirror M, passes through the collimator optical system COL, and is further polarized. The light passes through the beam splitter PBS and is condensed on the light receiving surface of the photodetector PD by the sensor lens SL. A read signal of information recorded on the optical disk OD1 is obtained using the output signal of the photodetector PD.

  In addition, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the photodetector PD. Based on this detection, the objective lens OBJ is moved to the lens holder so that the focusing actuator and tracking actuator of the objective lens actuator mechanism ACT appropriately image the light beam from the first semiconductor laser LD1 on the information recording surface R1 of the optical disk OD1. It is designed to move together with HD.

  When recording and / or reproducing information on the second optical disk OD2 (for example, DVD), the light beam emitted from the semiconductor laser LD2 having a light source wavelength of 600 to 700 nm is emitted from the light source unit LDU in the optical pickup device of FIG. After exiting from the outside, it passes through the second diffractive element D2 to be separated into a main beam for recording / reproducing and a sub beam for detecting a tracking error signal, and the divergence angle is adjusted by the coupling lens CPL. The light passes through the two-wavelength plate HWP and the dichroic beam splitter DBS, is reflected by the polarization beam splitter PBS, passes through the collimator optical system COL, is converted into a parallel light beam, and then enters the rising mirror M.

  In FIG. 2, a part of the light beam incident on the rising mirror M is transmitted through the monitor lens ML, then enters the laser power monitor LPM, and is used for monitoring the laser power. On the other hand, the remainder of the light beam incident on the rising mirror M is reflected there, passes through the quarter-wave plate QWP, and then the objective lens OBJ (in this embodiment, it consists of two elements, but one may be used). Then, the light is focused on the information recording surface R2 (the thickness of the protective layer is 0.6 mm) of the optical disk OD2.

  The reflected light beam modulated by the information pits on the information recording surface R2 passes through the objective lens OBJ and the quarter-wave plate QWP again, is reflected by the rising mirror M, passes through the collimator optical system COL, and is further polarized. The light passes through the beam splitter PBS and is condensed on the light receiving surface of the photodetector PD by the sensor lens SL. A read signal of information recorded on the optical disk OD2 is obtained using the output signal of the photodetector PD.

  In addition, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the photodetector PD. Based on this detection, the objective lens OBJ is placed in the lens holder so that the focusing actuator and the tracking actuator of the objective lens actuator mechanism ACT appropriately image the light beam from the second semiconductor laser LD2 on the information recording surface R2 of the optical disk OD2. It is designed to move together with HD.

  When recording and / or reproducing information with respect to the third optical disk OD3 (for example, CD), the light beam emitted from the semiconductor laser LD3 having a light source wavelength of 700 to 800 nm in the optical pickup device of FIG. After exiting from the outside, it passes through the second diffractive element D2 to be separated into a main beam for recording / reproducing and a sub beam for detecting a tracking error signal, and the divergence angle is adjusted by the coupling lens CPL. The light passes through the two-wavelength plate HWP and the dichroic beam splitter DBS, is reflected by the polarization beam splitter PBS, passes through the collimator optical system COL, is converted into a parallel light beam, and then enters the rising mirror M.

  In FIG. 2, a part of the light beam incident on the rising mirror M is transmitted through the monitor lens ML, then enters the laser power monitor LPM, and is used for monitoring the laser power. On the other hand, the remainder of the light beam incident on the rising mirror M is reflected there, passes through the quarter-wave plate QWP, and then the objective lens OBJ (in this embodiment, it consists of two elements, but one may be used). Then, the light is focused on the information recording surface R3 (the thickness of the protective layer is 1.2 mm) of the optical disc OD3.

  The reflected light beam modulated by the information pits on the information recording surface R3 passes through the objective lens OBJ and the quarter-wave plate QWP again, is reflected by the rising mirror M, passes through the collimator optical system COL, and is further polarized. The light passes through the beam splitter PBS and is condensed on the light receiving surface of the photodetector PD by the sensor lens SL. A read signal of information recorded on the optical disc OD3 is obtained using the output signal of the photodetector PD.

  In addition, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the photodetector PD. Based on this detection, the objective lens OBJ is moved to the lens holder so that the focusing actuator and the tracking actuator of the objective lens actuator mechanism ACT appropriately image the light beam from the third semiconductor laser LD3 on the information recording surface R3 of the optical disk OD3. It is designed to move together with HD.

  FIG. 3 is a perspective view of a light source unit LDU in which a plurality of light emitting units and an actuator are integrally stored. In FIG. 3, the LD electrode E passes through the base B whose upper surface is covered with the case C. On the base B, a pair of support portions W1, W2 are implanted. The guide shaft GS supported at both ends by the support portions W1 and W2 penetrates the light emitting portion holder HD in the horizontal direction, and the light emitting portion holder HD is held movably along the guide shaft GS.

  The light emitting unit holder HD has a second semiconductor laser LD2 that is a light emitting unit and a third semiconductor laser LD3 that is another light emitting unit attached to the front surface, and a connecting portion HDb on the back surface. A harness H for power supply is provided between the semiconductor lasers LD2 and LD3 that irradiate light beams in the vertical direction and the LD electrode E, respectively.

  The connecting portion HDb has a plate shape, and a leaf spring SG is attached to the upper surface. A drive shaft DS, which is a drive member, is disposed between the connecting portion HDb and the leaf spring SG, and is appropriately pressed by the urging force of the leaf spring SG. One end of the drive shaft DS is a free end, and the other end is connected to a piezoelectric actuator PZ which is an electromechanical conversion element installed on the base B. On the base B, an encoder (not shown) that magnetically (or optically) detects the amount of movement of the connecting portion HDb (for example, magnetic information is arranged on the guide shaft GS, and a reading head is provided on the light emitting portion holder HD). A drive circuit DC is arranged to apply a voltage to drive and control the piezoelectric actuator PZ in response to a signal from The piezoelectric actuator PZ, the drive shaft DS, the connecting portion HDb, the leaf spring SG, and the drive circuit DC constitute an actuator. The drive circuit DC may be arranged separately from the base B and connected by wiring.

  The piezoelectric actuator PZ is formed by laminating piezoelectric ceramics formed of PZT (zircon / lead titanate) or the like. Piezoelectric ceramics have a property in which the center of gravity of the positive charge and the center of gravity of the negative charge in the crystal lattice do not coincide with each other, are themselves polarized, and extend when a voltage is applied in the polarization direction. However, since the distortion of the piezoelectric ceramics in this direction is very small and it is difficult to drive the driven member by the amount of distortion, a plurality of piezoelectric ceramics PE are stacked between the electrodes as shown in FIG. A laminated piezoelectric actuator PZ having a structure in which C is connected in parallel is provided as a practical one. In the present embodiment, this stacked piezoelectric actuator PZ is used as a drive source.

  Next, as a driving method of the light emitting unit holder HD by the light source unit LDU, for example, a technique disclosed in Japanese Patent Application Laid-Open No. 2000-208825 can be used. Such a driving method will be described below. In general, the multilayer piezoelectric actuator PZ has a small amount of displacement when a voltage is applied, but has a large generated force and sharp response. Therefore, as shown in FIG. 5 (a), when a pulse voltage having a substantially sawtooth waveform with a sharp rise and a slow fall is applied, the piezoelectric actuator PZ extends rapidly at the rise of the pulse and more than that at the fall. Shrink slowly. Therefore, when the piezoelectric actuator PZ is extended, the drive shaft DS is pushed out to the left side (the support portion W1 side) in FIG. 3 by the impact force, but the connection portion HDb of the light emitting portion holder HD and the leaf spring SG are It does not move together with the drive shaft DS, but slips between the drive shaft DS and stays at that position (may move slightly). On the other hand, when the pulse falls, the drive shaft DS returns more slowly than when the pulse rises. Therefore, the connecting portion HDb and the leaf spring SG do not slip with respect to the drive shaft DS, and the right side of FIG. Move to (support side W2 side). That is, the lens holder HD2 can be continuously moved at a desired speed by applying a pulse whose frequency is set to several hundred to several tens of thousands of hertz. As apparent from the above, as shown in FIG. 5B, when a pulse with a slow rise and a sharp fall is applied, the light emitting unit holder HD can be moved in the opposite direction. As another driving method, for example, the technique disclosed in JP-A-2002-218772 can be used.

  The generation of a pulse having a sawtooth waveform can be realized by converting a signal output from the microcomputer of the drive circuit DC into an analog signal by a D / A converter and amplifying it by an amplifier. The signal representing the waveform shape is preferably stored in advance in a memory (not shown) in accordance with the signal from the photodetector PD. For example, an optimum focused spot is obtained while driving the drive axis DS. Feedback control is also possible. The stored data includes, for example, the maximum voltage Vmax shown in FIG. 5, voltage hold times t1 and t2, the number of rising and falling stages, and the holding time Δt for one step at that time. In FIG. 5, the portion where the voltage changes relatively slowly is shown by a straight line. Strictly speaking, a pulse having this waveform is obtained by outputting a stepped signal from a microcomputer.

  According to the light source unit of the present embodiment, since the light emitting unit holder HD can be driven to an arbitrary position by the actuator, the axis L2 of the light beam of the second semiconductor laser LD2 mounted thereon, or the third semiconductor laser LD3. 1 can be made to coincide with the optical axis of the condensing optical system of the optical pickup device shown in FIG. 1, and therefore the influence of the deviation of the optical axis of the light source can be avoided. Further, for example, when information is recorded and / or reproduced on a DVD (or CD) having a plurality of information recording layers having different protective layer thicknesses, the second semiconductor laser is used in accordance with the information recording layer used. By moving the LD 2 (or the third semiconductor laser LD 3) in the optical axis direction, spherical aberration can be corrected during information recording and / or reproduction.

  As is clear from the above, the first semiconductor laser can be incorporated into the light source unit LDU, and three or more semiconductor lasers can be arranged in a straight line on the light emitting unit holder, so The semiconductor laser can also be configured to coincide with the optical axis of the condensing optical system. Further, the light emitting portions of the semiconductor laser may be arranged in a matrix, and the axis of the light beam from one of the semiconductor laser light emitting portions may be made to coincide with the axis of the condensing optical system by using two actuators. . In addition, since the light source unit LDU incorporates an actuator, it is very easy to attach to and adjust the optical pickup device.

  FIG. 6 is a schematic configuration diagram showing a modification of the light source unit according to the present embodiment. In FIG. 6, in the light source unit LDU, two semiconductor lasers LD1 and LD2 are arranged with the axes L1 and L2 of the emitted light beams inclined with respect to each other. Further, in the same light source unit LDU, a small mirror SM that can be rotated around a point P and an actuator AC that provides rotational power to the small mirror SM are arranged. Since the actuator AC is the same as the configuration shown in FIG. 3, the illustration and description of a partial configuration are omitted.

  In the state shown in FIG. 6, the light beam emitted from the semiconductor laser LD1 is reflected by the small mirror M as the optical axis changing element and emitted to the outside of the light source unit LDU. The axis L1 of the light beam coincides with the axis of the objective lens OBJ shown as the condensing optical system. However, the axis L2 of the light beam emitted from the semiconductor laser LD2 does not coincide with the axis of the objective lens OBJ. Therefore, when recording and / or reproducing information using a light beam emitted from the semiconductor laser LD2, the actuator AC is driven to rotate the small mirror SM, so that the axis L2 of the light beam of the semiconductor laser LD2 is changed. It can be made to coincide with the axis of the objective lens OBJ. When information is recorded and / or reproduced again using the light beam emitted from the semiconductor laser LD1, the small mirror SM may be returned to the position shown in FIG. 6 by the actuator AC.

  FIG. 7 is a schematic configuration diagram illustrating another modification of the light source unit. This modification is a combination of a single semiconductor laser LD and a small mirror SM that can be rotationally driven by an actuator AC in the light source unit LDU. Since the actuator AC is the same as the configuration shown in FIG. 3, the illustration and description of a partial configuration are omitted. According to this modification, the light beam emitted from the semiconductor laser LD is reflected by the small mirror SM as the optical axis changing element and emitted from the light source unit LDU, but the small mirror SM is held by the actuator AC. The position of the small mirror SM is moved so that the most appropriate information signal is output from the photodetector PD because the position of the light beam received by the photodetector PD is changed by slightly rotating the holder MD. Can be made. In addition, it is preferable that the small mirror SM has two rotation axes orthogonal to each other and can be independently rotated by two actuators.

  Here, whether or not the light beam received by the photodetector PD is at an optimum position using the information signal output from the photodetector PD in response to the reflected light beam from the information recording surface being received by the light receiving surface. A method of detecting whether or not will be described. 8A to 8D are diagrams showing the relative position of the incident light beam L with respect to the light receiving surface RP of the photodetector. FIGS. 8E to 8I are diagrams showing waveforms obtained by processing the information signal output from the photodetector correspondingly.

  Here, the light-receiving surface RP is divided into four parts, top, bottom, left and right (2 × 2). In FIG. 8, the vertical (y) direction matches the track groove direction of the optical disk, and the horizontal (x) direction matches the track radius direction of the optical disk. The signal from each of the areas A to D is processed using the detected photodetector. More specifically, a focus error (FE) signal and a track error (TE) signal in a state where focus servo is applied to the optical disk are observed. As an example, the astigmatism method is used for the focus servo, and the FE signal is expressed by (photoelectric conversion signal in area A + photoelectric conversion signal in area C) − (photoelectric conversion signal in area B + photoelectric conversion signal in area D). It is obtained. In any one of the optical elements arranged in the optical path from the light source to the light detector, a positional deviation occurs for some reason, and as a result, the light beam condensed on the light receiving surface RP becomes the reference position of the light receiving surface RP. On the other hand, when it is shifted up and down (directions of areas A and D or B and C) (see FIG. 8C), as shown in FIG. The cross track signal generated when traversing greatly wraps around the FE signal, and the focus servo operation becomes unstable. However, in this case, since the focus servo operation for the optical disk of the objective lens is maintained, the positional deviation amount of any optical element arranged in the optical path from the light source to the photodetector is relatively small, A normal focus servo operation can be obtained by appropriately adjusting the optical element so that the light beam condensed on the light receiving surface RP substantially matches the reference position of the light receiving surface RP. Therefore, the optimum position is searched by appropriately rotating the small mirror SM. When the center of the collected light beam coincides with the reference position of the light receiving surface RP, an FE signal waveform having a small amplitude is obtained as shown in FIG. You can see that they match.

  On the other hand, the push servo method is used for the track servo as an example, and the TE signal is obtained by (photoelectric conversion signal of area A + photoelectric conversion signal of area B) − (photoelectric conversion signal of area C + photoelectric conversion signal of area D). It is what In any one of the optical elements arranged in the optical path from the light source to the light detector, a positional deviation occurs for some reason, and as a result, the light beam condensed on the light receiving surface RP becomes the reference position of the light receiving surface RP. On the other hand, if it is shifted to the left or right (directions of areas A and C or B and D) (see FIG. 8 (a) or 8 (b)), as shown in FIG. Can the TE signal waveform offset to the + side be obtained, or as shown in FIG. 8F, the TE signal waveform can be obtained with the waveform center offset to the-side, but does the track servo operation become unstable? Or, there is a problem that the spot focused on the optical disk is not positioned at the center of the track. However, in this case, since the focus servo operation for the optical disk of the objective lens is maintained, the positional deviation amount of any optical element arranged in the optical path from the light source to the photodetector is relatively small, A normal focus servo operation can be obtained by appropriately adjusting the optical element so that the light beam condensed on the light receiving surface RP substantially matches the reference position of the light receiving surface RP. Therefore, the optimum position is searched by appropriately rotating the small mirror SM. When the center of the collected light beam coincides with the reference position of the light receiving surface RP, a TE signal waveform having a waveform center of approximately 0 is obtained as shown in FIG. It can be seen that the position matches the reference position.

  FIG. 9A is a schematic configuration showing another modification of the light source unit. This modification is a combination of a single semiconductor laser LD and a coupling lens CUL that can be driven in the optical axis direction by an actuator AC in the light source unit LDU. Since the actuator AC is the same as the configuration shown in FIG. 3, the illustration and description of a partial configuration are omitted. For example, spherical aberration caused by the difference in the protective layer thickness of the optical disc can be corrected by changing the divergence angle (or convergence angle) of the light beam. Therefore, according to this modification, the lens holder HD holding the coupling lens CUL is driven in the optical axis direction by the actuator AC so as to suppress the spherical aberration within an allowable range. Since the actuator AC according to the present embodiment has high responsiveness, it can sufficiently cope with a case where random access is made to a plurality of information recording surfaces provided on the same optical disc.

  FIG. 9B is a schematic configuration showing another modification of the light source unit. This modification is a combination of a single semiconductor laser LD that can be driven in the optical axis direction by an actuator AC and a coupling lens CUL in the light source unit LDU. Since the actuator AC is the same as the configuration shown in FIG. 3, the illustration and description of a partial configuration are omitted. For example, spherical aberration caused by the difference in the protective layer thickness of the optical disc can be corrected by changing the divergence angle (or convergence angle) of the light beam. Therefore, according to this modification, the light source holder HD holding the semiconductor laser LD is driven in the optical axis direction by the actuator AC so as to suppress the spherical aberration within an allowable range. Since the actuator AC according to the present embodiment has high responsiveness, it can sufficiently cope with a case where random access is made to a plurality of information recording surfaces provided on the same optical disc. Of course, a collimator may be used as the coupling lens.

  FIG. 10 is a schematic configuration diagram illustrating another modification of the light source unit. This modification is a combination of a single semiconductor laser LD and a diffraction grating SD that can be driven in the direction orthogonal to the optical axis by an actuator AC in the light source unit LDU. Since the actuator AC is the same as the configuration shown in FIG. 3, the illustration and description of a partial configuration are omitted. According to this modification, the light beam emitted from the semiconductor laser LD passes through the diffraction grating SD as the optical axis changing element and is emitted from the light source unit LDU. Here, when the position of the diffraction grating SD is the reference position, the passing light beam travels straight through the diffraction grating SD (A direction shown in FIG. 10), but when the diffraction grating SD is shifted from the reference position in the direction perpendicular to the optical axis, The passing light beam is bent in the B direction or the C direction (the emission angle of the axis of the light beam is changed). By utilizing this, the actuator AC slightly drives each holder DD holding the diffraction grating SD in the direction orthogonal to the optical axis so that the most appropriate information signal is output from the photodetector (not shown). Can be. As the diffraction grating SD, the embodiment described in Japanese Patent Application Laid-Open No. 2003-329969 can be used.

  FIG. 11 is a schematic configuration diagram illustrating another modification of the light source unit. This modification is a combination of a single semiconductor laser LD and a beam shaping element BS that can be driven in the direction orthogonal to the optical axis by an actuator AC in the light source unit LDU. Since the actuator AC is the same as the configuration shown in FIG. 3, the illustration and description of a partial configuration are omitted. For example, when the cross-sectional shape of the light beam emitted from the semiconductor laser LD is an ellipse, the beam shaping element BS is used to shape it so as to approximate a circle, but the axis of the incident light beam and the beam shaping element BS If the optical axis does not match, astigmatism is particularly caused. Therefore, according to the present modification, aberration such as astigmatism can be suppressed by slightly driving the holder BSD holding the beam shaping element BS in the direction perpendicular to the optical axis by the actuator AC. Although not shown, in view of the occurrence of astigmatism when the distance between the semiconductor laser LD and the beam shaping element BS in the optical axis direction is inappropriate, the beam shaping element BS is compared with the semiconductor laser LD. Another drive mechanism for driving the lens in the optical axis direction can also be configured using the actuator AC. Regarding the beam shaping element BS, for example, those disclosed in JP-A-2001-167466, JP-A-2003-178480, etc. can be used.

  FIG. 12 is a schematic perspective view showing a photodetector driving apparatus according to the second embodiment. In the present embodiment, the photodetector PD can be moved two-dimensionally with respect to the base B by two actuators AC1 and AC2. The actuators AC1 and AC2 are the same as the actuator AC shown in FIG. Actuator AC2 moves stage Y in the direction perpendicular to the optical axis (upward in the figure) with respect to base B, and actuator AC1 moves stage X with photodetector PD attached to stage Y in the direction perpendicular to the optical axis. (Horizontal in the figure). In the case of a photodetector PD having a light-receiving surface divided into four, as described above with reference to FIG. 8, the photodetector PD is aligned with the axis of the light beam L using the FE signal and the TE signal. Actuators AC1 and AC2 can be driven and controlled.

  Since the photodetector PD can be attached to the outer peripheral surface of a housing (not shown) of the optical pickup device, it is easy to secure a space for a drive mechanism for moving the photodetector PD, and the design of the optical system and the actuator The degree of freedom increases. Further, the light beam emitted from the light source does not affect the path or the phase wavefront until it reaches the light receiving unit. For this reason, driving the actuator causes a change in the imaging performance of the light beam on the optical disk, and the passing light beam vignetts due to the aperture or effective area provided in the optical element in the optical system. Can be suppressed.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate.

It is a top view which shows roughly the structure of the optical pick-up apparatus of this Embodiment. It is the figure which looked at the structure of FIG. 1 in the arrow II direction. It is a perspective view of the light source unit LDU which accommodated the several light emission part and the actuator integrally. FIG. 3 is a perspective view showing a multilayer piezoelectric actuator PZ having a structure in which a plurality of piezoelectric ceramics PE are stacked and electrodes C are connected in parallel therebetween. It is a figure which shows the waveform of the voltage pulse applied to the piezoelectric actuator PZ. It is a schematic block diagram which shows the modification of the light source unit concerning this Embodiment. It is a schematic block diagram which shows the modification of the light source unit concerning this Embodiment. 8A to 8D are diagrams showing the relative position of the incident light beam L with respect to the light receiving surface RP of the photodetector. FIGS. 8E to 8I are diagrams showing waveforms obtained by processing a signal output from the photodetector correspondingly. It is a schematic block diagram which shows the modification of the light source unit concerning this Embodiment. It is a schematic block diagram which shows the modification of the light source unit concerning this Embodiment. It is a schematic block diagram which shows the modification of the light source unit concerning this Embodiment. It is a schematic perspective view which shows the drive device of the photodetector concerning 2nd Embodiment.

Explanation of symbols

AC, AC1, AC2 Actuator ACT Objective lens Actuator mechanism B Base BS Beam shaping element BSD Holder C Case COL Collimator CPL Coupling lens CDU Light source unit D1 Diffraction element D2 Diffraction element DBS Dichroic beam splitter DC Drive circuit DD Holder DS Drive axis E Electrode GS Guide shaft H Harness HD Light emitting part holder HDb Connecting part LD, LD1 to LD3 Semiconductor laser LDU Light source unit LPM Laser power monitor M Mirror M Small mirror MD Holder ML Monitor lens OBJ Objective lens PBS Polarizing beam splitter PD Photodetector PZ Piezoelectric actuator RP Light-receiving surface SD Diffraction grating SL Sensor lens SM Small mirror W1, W2 Supporting part

Claims (12)

A light source unit; and a condensing optical system including an objective lens that condenses the light beam from the light source unit on an information recording surface of an optical information recording medium, and condenses the light beam emitted from the light source. An optical pickup device configured to record and / or reproduce information by focusing on an information recording surface of the optical information recording medium via an optical system,
The light source unit integrally incorporates a light emitting unit and an actuator that moves the light emitting unit in an optical axis direction and / or a direction intersecting the optical axis.   The optical pickup device according to claim 1, wherein a plurality of the light emitting units are provided. A light source unit; and a condensing optical system including an objective lens that condenses the light beam from the light source unit on an information recording surface of an optical information recording medium, and condenses the light beam emitted from the light source. An optical pickup device configured to record and / or reproduce information by focusing on an information recording surface of the optical information recording medium via an optical system,
The light source unit integrally includes a light emitting unit, a coupling lens that emits a light beam emitted from the light emitting unit and changes the divergence, and an actuator that moves the coupling lens in the optical axis direction. An optical pickup device characterized by being incorporated.   A light detector that receives a reflected light beam from the information recording surface; and the actuator is configured to generate the light emitting unit based on an information signal output from the light detector according to the reflected light beam from the information recording surface. The optical pickup device according to claim 1, wherein the optical pickup device is driven. A light source unit; and a condensing optical system including an objective lens that condenses the light beam from the light source unit on an information recording surface of an optical information recording medium, and condenses the light beam emitted from the light source. An optical pickup device configured to record and / or reproduce information by focusing on an information recording surface of the optical information recording medium via an optical system,
The light source unit integrally incorporates a light emitting unit, an optical axis changing element that changes the direction of the axis of a light beam emitted from the light emitting unit, and an actuator that moves the optical axis changing element. Optical pickup device.   The optical pickup device according to claim 5, wherein the optical axis changing element is a mirror, and the actuator rotationally drives the mirror.   6. The optical pickup device according to claim 5, wherein the optical axis changing element is a diffraction grating, and the actuator drives the diffraction grating in a direction crossing the optical axis.   A light detector that receives a reflected light beam from the information recording surface, and the actuator is configured to detect the optical axis based on an information signal output from the light detector according to the reflected light beam from the information recording surface. 8. The optical pickup device according to claim 5, wherein the change element is driven.   A light source unit used in the optical pickup device according to claim 1.   A condensing optical system including a light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and a beam shaping element disposed between the light source and the objective lens; And an actuator that drives the beam shaping element, and records information by condensing the light beam emitted from the light source onto the information recording surface of the optical information recording medium via the condensing optical system. And / or an optical pickup device adapted to perform reproduction. A light source, a condensing optical system including an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, a photodetector for receiving a reflected light beam from the information recording surface, and the light An actuator for driving the detector, and recording and / or recording information by condensing the light beam emitted from the light source onto the information recording surface of the optical information recording medium via the condensing optical system. An optical pickup device adapted to perform reproduction,
Based on the information signal output from the photodetector in response to the reflected light beam from the information recording surface, the actuator drives the photodetector in a direction crossing the light beam incident on the photodetector. An optical pickup device characterized by the above. The actuator applies a voltage to the electromechanical conversion element, a driving member fixed to one end of the electromechanical conversion element, a movable member movably held on the driving member, and the electromechanical conversion element And a drive circuit, wherein the drive member and the movable member are moved relative to each other by expanding and contracting the electromechanical conversion element according to a voltage applied from the drive circuit. The optical pickup device according to claim 1.

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