JP2008004169A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device which detects a temperature accurately corresponding to an amount of caused wavefront aberration and consequently can correct the wavefront aberration using only the detected temperature as a variable. <P>SOLUTION: A collimator lens 22 converts, in a standard position, incident laser beams into parallel beams and makes the parallel beams incident on an objective lens 7. The objective lens 7 converges the incident laser beams toward an optical disk D. The objective lens 7 is held by a lens holder 12. On the surface of the lens holder 12 facing the optical disk D, a temperature sensor 21 is installed close to the objective lens 7. A signal indicating a temperature detected by the temperature sensor 21 is input to a controller 23. In accordance with the temperature indicated by the input signal, the controller 23 controls a collimator lens actuator 24 so as to move the collimator lens 22 to a position at which wave front aberration caused by the objective lens 7 at the above temperature is corrected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical pickup that irradiates a recording surface of an optical disc with a laser beam for recording or reading information.

  Optical pickups used in various optical disk drive devices for reading optical information recorded on optical disks such as CDs (compact disks) and DVDs and writing optical information to optical disks are generally emitted from semiconductor lasers. The laser beam is converged on the recording surface of the optical recording medium.

  By the way, the size of each pit recorded on the recording surface of the optical disc is in the order of the wavelength of the laser beam used for the optical disc in order to maximize the recording density of the optical disc. Therefore, as the imaging performance of the objective lens used in such an optical pickup, a spherical aberration (RMS <0.07λ) that satisfies an allowable value called a so-called Marshall limit is required.

  By the way, at present, a plastic single lens is mainly used as an objective lens of an optical pickup for DVDs and CDs in order to reduce the weight of the entire optical pickup and to suppress the manufacturing cost. As a similar flow, in the Blu-ray Disc standard which is the next generation DVD (Digital Versatile Disc), a single plastic lens of NA 0.85 is used. However, when trying to achieve a high NA with such a single plastic lens, the occurrence of spherical aberration at the beam spot due to temperature change becomes prominent, and there was a temperature change of about 20 degrees Celsius from a state where the wavefront aberration is zero. Only spherical aberration will exceed the Marechal limit.

Therefore, conventionally, by moving the movable lens of the beam expander following the temperature change, the parallel light beam incident on the objective lens is changed, so that the spherical aberration generated in the disk surface beam spot by the objective lens becomes less than the Marechal limit. The structure which correct | amends like this is proposed (nonpatent literature 1). However, in this non-patent document 1, it is not clearly described in what location the sensor for detecting what physical quantity is installed, but the spherical aberration generated depending on the temperature change is directly detected by the optical sensor. In general, a configuration in which a movable lens follows this is generally used.
“O PLUS E” Vol.27, No.4, New Technology Communications, Inc., April 2005, p405

  However, when spherical aberration is detected by the optical sensor, the reflected light reflected by the recording surface of the optical disk must be separated and guided to a separately installed sensor, and the number of parts and weight of the entire pickup are increased. This will cause a cost increase.

  For this reason, it is conceivable to detect the temperature at which the temperature change is detected using a temperature sensor, but when the temperature sensor is simply installed, the detected temperature may not correspond to the amount of spherical aberration that has occurred. possible.

  Accordingly, an object of the present invention is to provide an optical disc drive apparatus that can correct spherical aberration using only the detected temperature as a variable by detecting a temperature that accurately corresponds to the amount of generated spherical aberration.

  The present invention employs the following means in order to solve the above problems.

  That is, the optical disk drive device according to the present invention is an optical pickup that irradiates an optical disk with laser light emitted from a semiconductor laser via an optical path that passes through a plurality of optical members, and the laser light in the optical path is divergent light. A collimating lens that is arranged at a traveling position and converts the laser light into parallel light when in a standard position, and holds the collimating lens, and the collimating lens is moved to the standard according to an input control signal. A collimating lens actuator that can be adjusted in position in the optical axis direction from a position; an objective lens that converges laser light transmitted through the collimating lens toward the optical disc; a lens holder that holds the objective lens; and the objective lens. The position of the beam waist of the focused laser beam is In order to match the recording surface, an automatic focus adjustment mechanism that adjusts the position of the objective lens in the optical axis direction together with the lens holder, and is installed in the lens holder close to the objective lens, and the temperature of the objective lens is adjusted. In response to a temperature sensor that outputs a temperature signal indicating the temperature signal and a temperature indicated by the temperature signal output from the temperature sensor, the objective lens uses a convergent light or a divergent light as an objective in order to correct spherical aberration generated at the temperature. And a controller for inputting a control signal to the collimating lens actuator so as to move the collimating lens to a position where it is incident on the lens.

  If comprised in this way, since the temperature sensor is installed in proximity to the objective lens in the lens holder, the temperature of the objective lens can be detected almost accurately. A temperature signal indicating the temperature of the objective lens detected by the temperature sensor is input to the controller. This controller inputs a control signal to the collimating lens actuator in order to move the collimating lens to a position where spherical aberration generated in the objective lens can be corrected at the temperature indicated by the input temperature signal. The collimating lens actuator that has received this control signal moves the collimating lens to a position determined by the control signal. As a result, the laser light emitted from the collimating lens 22 changes from parallel light to convergent light or divergent light, so that the objective lens 7 generates positive or negative spherical aberration. As a result, the spherical aberration originally caused by the temperature is canceled.

  The collimating lens may be disposed immediately after the semiconductor laser, or may be disposed at a location where the laser light once converted into parallel light or convergent light is again diverged by another lens. Further, the collimating lens may be composed of a single lens or a plurality of lenses. In the latter case, only a part of the plurality of lenses constituting the collimating lens may be adjusted by the collimating lens actuator.

  Further, when the laser light incident on the objective lens changes from parallel light to divergent light or convergent light, the position of the beam spot formed by the objective lens may move accordingly. An automatic focus adjustment mechanism is provided in the optical pickup in order to cancel the focus shift caused by that. With this automatic focus adjustment mechanism, the focal position can be immediately corrected even if the position of the beam spot is moved. According to a third aspect of the present invention, the automatic focusing mechanism includes the objective lens together with the lens holder in order to match the position of the beam waist of the laser beam converged by the objective lens with the recording surface of the optical disc. Is provided with an objective lens actuator for adjusting the position of the lens in the optical axis direction. The objective lens actuator is a kind of motor that uses electromagnetic force, and adjusts the position of the objective lens by the mutual electromagnetic action of the permanent magnet and the coil. A permanent magnet is provided in the lens holder, and the magnetic force generated by the permanent magnet is reduced. If the coil that generates electromagnetic force in the direction of the optical axis of the objective lens is fixed to the semiconductor laser, heat generated by the current supplied to the coil is prevented from being transmitted to the objective lens. it can.

  Embodiments of an optical pickup according to the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an optical disc drive apparatus according to an embodiment of the present invention. As shown in FIG. 1, this optical disk drive apparatus is composed of a thin box-shaped casing 1 incorporated in a housing of a personal computer (not shown) and a tray 2 that can be advanced and retracted from the casing 1. ing. When the tray 2 is pulled out from the casing 1, the optical disk D can be attached and detached. When the tray 2 is pushed into the casing 1, the optical disk D is accommodated in the casing 1 and the opening of the casing 1 is closed. Furthermore, in this example, in order to reduce the thickness of the entire optical disk drive device, the tray 2 incorporates a spindle 3 and a carriage 4 which are main components for exhibiting the original function as the optical disk drive device. ing. In addition, as a thin optical disk drive device employed in a so-called notebook personal computer, there is one in which a spindle 3 and a carriage 4 are incorporated in a casing side, and an upper surface of the casing is freely opened and closed by a lid. The present invention can be applied even to an optical disk drive device.

  In the optical disk apparatus shown in FIG. 1, on the upper surface of the tray 2, there is formed a disk mounting portion 2a that is recessed in accordance with the circular outer edge of the optical disk so that the optical disk D can be mounted and rotated. Yes. A spindle 3 is embedded in the center of the disk mounting portion 2a. The spindle 3 is rotated by a built-in direct drive motor with a shaft inserted into a hole drilled in the center of the optical disc D and clamped. As a result, the spindle 3 can rotate the optical disk D.

  The carriage 4 incorporates an optical pickup, and two rails 5 and 6 are provided in a substantially rectangular notch 2b formed in the bottom surface of the disk mounting portion 2a along the radial direction with the spindle 3 as the center. Is slidably held. That is, the rails 5 and 6 are notched in parallel (and therefore in parallel with each other) in a single movement locus oriented in the radial direction around the spindle 3 on which an objective lens 7 to be described later moves. 2b. One rail 6 passes through a pair of guide followers 4 a protruding from one side edge of the carriage 4, and a fork 4 b protruding from the other side edge holds the other rail 5. As a result, the carriage 4 slides in the notch 2b so that an objective lens 7 described later moves in the radial direction around the spindle 3 (that is, the tracking direction of the optical disc D). Although not shown, a rack is formed at the tip of the guide follower 4a, while a worm gear meshing with the inner surface of the notch 2b facing the rack is incorporated in parallel with the rail 6. Yes. Therefore, the position of the carriage 4 is controlled by rotating the worm gear (not shown) by a motor (not shown).

  A window 4 d for exposing the objective lens 7 included in the optical pickup is formed in the upper surface of the carriage 4, and a cavity for accommodating the optical pickup is formed inside the carriage 4.

  2 shows an optical configuration of each optical component constituting the optical pickup built in the carriage 4 (however, the illustration of the reflecting member such as a reflecting mirror and the refractive member such as a prism is omitted, and the optical path is linearized. And a block configuration of the control circuit.

  The optical components constituting the optical pickup are the semiconductor laser 8, the beam splitter 9, the collimating lens 22, the objective lens 7, the sensor lens 25, and the light receiving element 26.

  The semiconductor laser 8 as a laser light source emits a laser beam in the blue-violet band (405 nm) in accordance with the Blu-ray Disc standard.

  The beam splitter 9 is held in the optical path of the laser light emitted from the semiconductor laser 8 as divergent light, transmits the laser light, and reflects the reflected light reflected by the optical disk D toward the sensor lens 25. It is a prism (polarization beam splitter).

  The collimating lens 10 is installed at a position where the laser light travels as divergent light in the optical path of the laser light emitted from the reaction body laser 8 and transmitted through the beam splitter 10. It is a positive lens that refracts so as to convert it into parallel light. The collimating lens 10 is held by a collimating lens actuator 24 so as to be able to advance and retreat and adjust its position only in the optical axis direction (that is, the direction of the beam axis of the laser beam emitted from the semiconductor laser 8).

  The objective lens 7 is a condensing lens (positive lens) that focuses the laser light transmitted through the collimating lens 10 onto the recording layer of the optical disc D. This objective lens 7 is a plastic single lens produced in accordance with the Blu-ray Disc standard, and therefore its numerical aperture (NA) is 0.85.

  The laser light focused on the recording layer by the objective lens 7 is reflected by the recording layer, and becomes modulated light according to the information recorded on the recording layer, and enters the objective lens 7 while diverging. In normal temperature, the light is converted into parallel light by the objective lens 7 and enters the collimating lens 10. Then, it is converted into convergent light by the collimator lens 22, enters the beam splitter 9, a part of the light is reflected, and enters the sensor lens 25. The sensor lens 25 converges the incident reflected light on the light receiving element 26. The light receiving element 26 detects the light amount of the entire reflected light received and transmits it as a reproduction signal to an output circuit (not shown), and also detects the distribution of the light amount of the reflected light, thereby producing a tracking signal and a focusing signal. Then, it is transmitted to the objective lens drive circuit 27 as a control device.

  The objective lens drive circuit 27 cancels the deviation from the recording surface of the optical disc D at the position of the laser light spot (beam waist) based on the state of the laser light indicated by the focusing signal transmitted from the light receiving element 25. The amount of movement of the lens 7 (the amount of movement of the lens holder 12) is calculated, and the objective lens actuator 10 is controlled based on the calculated amount of movement. The position is adjusted (focusing) in the optical axis direction so as to be formed on the recording surface of D. At the same time, the objective lens driving circuit 27 uses the tracking signal transmitted from the light receiving element 25 in order to finely adjust the tracking error due to insufficient tracking accuracy due to the movement of the entire carriage 4 and realize high-accuracy tracking. Based on this, the objective lens actuator 10 is controlled to adjust the position of the objective lens 7 in the tracking direction (the radial direction of the optical disc D clamped to the spindle 3).

  FIG. 3 is a perspective view of the objective lens actuator 10. In FIG. 3, an arrow z indicates a direction parallel to the optical axis of the objective lens 7 (that is, a direction perpendicular to the optical disc D clamped on the spindle 3, hereinafter referred to as “z direction” for convenience), and an arrow x indicates The tracking direction (that is, the direction in which the entire carriage 4 slides, hereinafter referred to as “x direction”) is indicated, and the arrow y indicates the z direction and the direction orthogonal to the x direction (hereinafter referred to as “y direction” for convenience). .

  As shown in FIG. 3, the optical pickup 10 has a substantially prismatic shape with the major axis direction in the x direction and a wire fixing mount 11 fixed to the inside of the carriage 4 and a long length in the x direction. A lens holder 12 having an approximately prismatic shape that is oriented in the axial direction and substantially the same length as the wire fixing mount 11 and is supported by the wire fixing mount 11 so as to be swingable via eight wires W, and the lens holder 12, a pair of tracking coils 13 and 14 wound around both ends in the x direction, a focus coil 15 and 16 fixed to a pair of side surfaces facing the y direction in the lens holder 12, and a rectangular plate, respectively. A focus which has a shape equivalent to a U-shaped cross section and is fixed in the carriage 4 so as to surround the lens holder 12 from the tray 2 side. A pair of focus magnets (permanent magnets) 18, 18 fixed to the respective focus coils 15, 16 on the inner surface of each portion extending in the z direction of the focus actuator base 17. Two tracking actuator bases 19 having a shape equivalent to that of a rectangular plate bent into a U-shaped cross section and fixed in the carriage 4 so as to surround the tracking coils 13 and 14 from the tray 2 side, 19, a pair of tracking magnets (permanent magnets) 20 and 20 fixed so as to sandwich the tracking coils 13 and 14 on the inner surface of each portion extending in the z direction in each tracking actuator base 19, and the center of the lens holder 12 At the opening end on the optical disc D side of the through-hole penetrating in the z direction An objective lens 7 fitted toward the optical axis in the z-direction have, from the temperature sensor 21 for fixed near the outer edge of the objective lens 7 in the upper surface of the lens holder 12 is constituted. Of the components described above, the wire fixing mount 11, the lens holder 12, the focus actuator base 17, and the tracking actuator bases 19 and 19 are metal magnetic material components.

  Both ends of the wire fixing mount 11 are formed as ears 11a and 11a whose thickness in the y direction is reduced in order to earn a stroke of the wire W. Similarly, the outer sides of the tracking coils 13 and 14 in the lens holder 12 are also formed as ears 12a and 12a whose thickness in the y direction is reduced in order to increase the stroke of the wire W. Between the ears 11a, 12a of the wire fixing mount 11 and the lens holder 12 facing each other, there are four wires W that are axially oriented in the y direction and arranged at equal intervals in the z direction, respectively. It is fixed through. As a result, the lens holder 12 can be translated in the x and z directions while maintaining the posture in which the optical axis of the objective lens 7 is directed in the z direction. Of the eight wires W in total, two serve as electric wires for supplying power to both tracking coils 13 and 14 at the same time, and the other two electric wires for supplying electric power to both focus coils 15 and 16 simultaneously. The remaining four also serve as signal lines for extracting detection signals from the temperature sensor 21.

  Each of the focus coils 15 and 16 is wound around a flat prismatic resin core. The bottom surface of the core is fixed to the side surface of the lens holder 12.

  Each of the focus magnets 18 and 18 has a flat prismatic shape whose bottom surface is approximately the same size as each of the focus coils 15 and 16, and is vertically divided into two in the z direction on the surface facing the focus coils 15 and 16. Have magnetic poles.

  Each tracking magnet 20 has a prismatic shape having the same height in the z direction as each of the focus magnets 18, 18, and there are magnetic poles at both ends in the y direction.

  Therefore, when a current in a predetermined direction is supplied to the focus coils 15 and 16 from the objective lens drive circuit (not shown) through the wires W, the focus coils 15 and 16 are coupled with the magnetic force generated from the focus magnets 18 and 18. An electromagnetic force is generated in one direction in the z direction, and the lens holder 12 (and hence the objective lens 7) moves in that direction by a distance proportional to the power of the current. When a current in the reverse direction is supplied, the lens holder 12 (and hence the objective lens 7) moves in the reverse direction by a distance proportional to the power of the current. Thereby, the objective lens 7 is focused.

  On the other hand, when current in a predetermined direction is supplied to both tracking coils 13 and 14 from an objective lens drive circuit (not shown) through each wire W, the tracking coils 13 and 14 are coupled with the magnetic force generated by each tracking magnet 20. Electromagnetic force is generated in one direction in the x direction, and the lens holder 12 (and hence the objective lens 7) moves in that direction by a distance proportional to the power of the current. When power in the reverse direction is supplied, the lens holder 12 (and hence the objective lens 7) moves in the reverse direction by a distance proportional to the power of the current. Thereby, the tracking error of the objective lens 7 is adjusted.

  The temperature sensor 21 is, for example, a CMOS temperature sensor IC, and generates an output voltage (temperature signal) that is linear with respect to a temperature change. Accordingly, since the temperature sensor 21 is disposed in the vicinity of the outer edge of the objective lens 7 on the upper surface of the lens holder 12, an output voltage corresponding to the temperature of the objective lens 7 is generated and shown in FIG. Input to the controller 23. The temperature sensor 21 may output the detected temperature as a digital signal.

  The collimating lens actuator 24 described above has the same configuration as that obtained by removing the tracking coils 13 and 14, the tracking magnets 20 and the temperature sensor 21 from the objective lens actuator 10 shown in FIG. The description of the configuration is omitted. However, in the collimating lens actuator 24, configurations corresponding to the focus coils 15 and 16 and the focus magnets 18 and 18 in the objective lens actuator are referred to as a “correction coil” and a “correction magnet”, respectively. In a standard state in which no current is supplied to the correction coil, the collimator lens 22 converts the laser light emitted as divergent light from the semiconductor laser 8 into parallel light (that is, the front focal point of the semiconductor laser 8 is At a position overlapping with a position optically equivalent to the light emitting point). When a current in a predetermined direction is supplied to the correction coil, the collimator lens 22 is moved by a distance proportional to the power of the current in one direction, and when a current in the reverse direction is supplied, the collimator lens 22 is reversed. Moving.

  The controller 23 stores the temperature and the position of the collimating lens 22 in advance in association with each other based on the input output voltage (that is, a signal indicating the temperature of the objective lens 7 detected by the temperature sensor 21). , Or by executing a function prepared in advance, the correction amount (the moving direction and the moving amount) of the collimating lens 22 is calculated. Then, the current of the direction and power corresponding to the calculated correction amount is supplied to the correction coil of the collimating lens actuator 24.

  As a result, when the temperature of the objective lens 7 is still lower than the design value, a current in a predetermined direction is supplied to the correction coil of the collimating lens actuator 24, and as shown in FIG. 7 side is moved. As a result, the laser light incident on the objective lens 7 from the collimating lens 22 becomes convergent light (in a state in which positive spherical aberration is generated), and the negative spherical aberration generated by the objective lens 7 is canceled out, so that the spherical aberration becomes zero. To.

  When the temperature of the objective lens 7 rises to the design value, the power supply to the correction coil is stopped, so that the collimator lens 22 returns to the design position as shown in FIG. As a result, the laser light incident on the objective lens 7 from the collimator lens 22 becomes parallel light, and the state of the spherical aberration zero of the objective lens 7 is utilized as it is.

  When the temperature of the objective lens 7 further rises, a reverse current is supplied to the correction coil of the collimating lens actuator 24, and the collimating lens 22 is moved to the beam splitter 8 side as shown in FIG. As a result, the laser light incident on the objective lens 7 from the collimating lens 22 becomes divergent light (a state in which a negative spherical aberration is generated), canceling the positive spherical aberration generated by the objective lens 7 and reducing the spherical aberration to zero. To.

  According to the optical disk drive apparatus of the present embodiment described above, the temperature sensor 21 is provided in the vicinity of the objective lens 7, so that the temperature detected by the temperature sensor 21 is the temperature of the objective lens 7 itself. Can be considered. Since the temperature of the objective lens 7 and the value of the spherical aberration generated by the objective lens 7 are in a substantially linear relationship with the numerical aperture (NA) of the objective lens as a proportional constant, based on the temperature, The value of spherical aberration caused by the objective lens 7 can be indirectly known.

  In this case, the reflected light from the optical disk is usually separated using a separate beam splitter to detect spherical aberration. However, when such an optical configuration is adopted, the number of optical components increases, and the weight of the entire carriage 4 increases. As a result, the tracking response deteriorates and the problem of cost increase arises. On the other hand, if the temperature sensor is configured to detect the temperature as the measurement value, only the temperature sensor 21 is added, so that there is almost no problem of weight increase or cost increase.

  The second embodiment is different from the first embodiment in the structure of the objective lens actuator 10 (therefore, the collimating lens actuator 24 having the same configuration as the objective lens actuator 10 except for the tracking coil, the tracking magnet, and the temperature sensor). Only the structure is different, and other configurations are common.

  That is, in the objective lens actuator 10 of Example 1 described above, each coil (tracking coils 13 and 14, focus coils 15 and 16) is provided on the lens holder 12 which is a movable portion, and each magnet (tracking magnet 20 and focus magnet). 18) was fixed to the carriage 4. However, in this case, since current is supplied to each coil, Joule heat is generated by its own resistance component. Therefore, since the objective lens 7 is heated by this Joule heat, it causes an extra temperature rise in the objective lens. This means that the amount of spherical aberration correction generated on the high temperature side must be increased, which requires an increase in the movement stroke of the collimating lens actuator.

  Therefore, in the second embodiment, the coils (tracking coils 13 and 14, focus coils 15 and 16) are fixed to the carriage 4 side, and the magnet (tracking magnet 20 and focus magnet 18) is fixed to the lens holder 12. Thus, Joule heat generated in each coil (tracking coils 13, 14 and focus coils 15, 16) is prevented from being directly conducted to the objective lens 7.

  Specifically, the structure of the objective lens actuator 10 according to the second embodiment will be described with reference to the perspective view of FIG. In FIG. 6, parts having the same functions as those of the objective lens actuator 10 according to the first embodiment are denoted by the same reference numerals. The definition of each direction in FIG. 6 is the same as that in FIG.

  As shown in FIG. 6, the optical pickup 10 has a substantially prismatic shape with the major axis direction in the x direction and a wire fixing mount 11 fixed to the inside of the carriage 4, and is long in the x direction. A lens holder 12 having an approximately prismatic shape that is axially oriented and substantially the same length as the wire fixing mount 11, and is supported by the wire fixing mount 11 so as to be swingable via four wires W, and the lens holder 12, a pair of focus magnets 18 and 18 fixed to the center of each side surface facing the y direction, and both sides of the focus magnets (permanent magnets) 18 and 18 on each side surface (on both sides in the x direction), respectively. A shape equivalent to a total of four tracking magnets (permanent magnets) 20 fixed and a portion corresponding to each arm of a Greek cross-shaped plate folded into a U-shaped cross section. And the actuator base 30 fixed in the carriage 4 so as to surround the lens holder 12 from the tray 2 side, and the focus magnets 18 and 18 on the inner surface of each portion of the actuator base 30 extending in the z direction. A pair of focus coils 15 and 16 fixed opposite to each other, and each side facing the x direction in each portion of the actuator base 30 extending in the z direction are fixed to face each tracking magnet 20. Four tracking coils 13, 13, 14, 14, an objective lens 7 fitted in the opening end on the optical disc D side of a through hole that penetrates the center of the lens holder 12 in the z direction, and an objective lens on the upper surface of the lens holder 12 7 and a temperature sensor 21 fixed in the vicinity of the outer edge. There. Of the above-described components, the wire fixing mount 11, the lens holder 12, and the actuator base 30 are resin molded products.

  Both ends of the wire fixing mount 11 are formed as ears 11a and 11a whose thickness in the y direction is reduced in order to earn a stroke of the wire W. Similarly, both ends in the x direction of the lens holder 12 are also formed as ears 12a and 12a whose thickness in the y direction is reduced in order to earn a stroke of the wire W. Between the ears 11a, 12a of the wire fixing mount 11 and the lens holder 12 facing each other, two wires W that are axially oriented in the y direction and arranged in the z direction pass through. It is fixed. As a result, the lens holder 12 can be translated in the x and z directions while maintaining the posture in which the optical axis of the objective lens 7 is directed in the z direction. The total of four wires W also serve as signal lines for taking out detection signals from the temperature sensor 21.

  Each of the focus coils 15 and 16 is wound around a flat prismatic resin core. The bottom surface of the core is fixed to the inner surface of each portion of the actuator base 30 that extends in the z direction.

  Each of the focus magnets 18 and 18 has a flat prismatic shape whose bottom surface is approximately the same size as each of the focus coils 15 and 16, and is vertically divided into two in the z direction on the surface facing the focus coils 15 and 16. Have magnetic poles.

  Each tracking magnet 20 has a prismatic shape having the same height in the z direction as each of the focus magnets 18, 18, and there are magnetic poles at both ends in the y direction.

  Each tracking coil 13, 14 is wound around a flat prismatic resin core. The bottom surface of the core is fixed to both side surfaces of each portion of the actuator base 30 extended in the z direction.

  The temperature sensor 21 is, for example, a CMOS temperature sensor IC, and generates an output voltage that is linear with respect to a temperature change. Accordingly, since the temperature sensor 21 is disposed in the vicinity of the outer edge of the objective lens 7 on the upper surface of the lens holder 12, an output voltage corresponding to the temperature of the objective lens 7 is generated and shown in FIG. Input to the controller 23. The temperature sensor 21 may output the detected temperature as a digital signal.

  According to the second embodiment, currents are supplied to the coils 13 to 16 from an objective lens driving circuit (not shown) to the coils 13 and 14 for tracking or focusing, whereby the coils 13 to 16 are caused to have Joule heat. Even if this occurs, there is almost no conduction of heat directly to the objective lens 7 through the solid substance. Although it cannot be denied that heat is transmitted to the objective lens 7 by heat radiation and air convection, the transmission speed is slower than that in the case of direct conduction. Accordingly, even when the movement stroke of the collimator lens 22 by the collimator lens actuator 24 is limited, the spherical aberration generated by the objective lens 7 is suppressed to zero over a long time by making full use of the stroke. Can do.

  Other configurations and operations in the second embodiment are exactly the same as those in the first embodiment described above, and thus description thereof is omitted.

1 is an overall perspective view of an optical disc drive apparatus according to an embodiment of the present invention. The figure which shows the optical structure of the optical component which comprises an optical pick-up, and a circuit block The perspective view which shows the structure of the objective-lens actuator by Example 1. FIG. Optical configuration diagram showing an example of the position of the collimated lens after adjustment when the temperature of the objective lens is lower than the set temperature Optical configuration diagram showing an example of the position of the collimated lens after adjustment when the temperature of the objective lens is higher than the set temperature The perspective view which shows the structure of the objective-lens actuator by Example 2. FIG.

Explanation of symbols

2 Tray 3 Spindle 4 Carriage 7 Objective Lens 8 Semiconductor Laser 10 Objective Lens Actuator 12 Lens Holder 22 Collimating Lens 23 Controller 24 Collimating Lens Actuator D Optical Disc

Claims (3)

In an optical pickup that irradiates an optical disk with laser light emitted from a semiconductor laser via an optical path passing through a plurality of optical members,
A collimating lens that is disposed at a position where the laser light travels as divergent light in the optical path, and that converts the laser light into parallel light at a standard position;
A collimating lens actuator that holds the collimating lens and can adjust the position of the collimating lens in the optical axis direction from the standard position in accordance with an input control signal;
An objective lens for converging laser light transmitted through the collimating lens toward the optical disc;
A lens holder for holding the objective lens;
An automatic focus adjustment mechanism that adjusts the position of the objective lens in the optical axis direction together with the lens holder in order to match the position of the beam waist of the laser light focused by the objective lens with the recording surface of the optical disc;
A temperature sensor installed in the lens holder in proximity to the objective lens and outputting a temperature signal indicating the temperature of the objective lens;
Corresponding to the temperature indicated by the temperature signal output from the temperature sensor, the collimating lens actuator controls the objective lens to move the collimating lens to a position that corrects the spherical aberration generated in the beam spot at the temperature. An optical pickup comprising a controller for inputting a signal. The focus adjusting mechanism includes a beam splitter that separates a laser beam reflected by the recording surface of the optical disc from the optical path;
A light receiving element that receives the laser beam separated by the beam splitter;
Based on the state of the laser beam received by the light receiving element, a control device for determining the amount of movement of the objective lens for canceling the deviation of the beam waist position from the recording surface;
2. An optical pickup according to claim 1, wherein said optical pickup is used as an objective lens actuator for adjusting the position of said lens holder in the optical axis direction by an amount of movement obtained by said control device. The objective lens actuator generates an electromagnetic force in the optical axis direction of the objective lens based on a permanent magnet provided in the lens holder and a magnetic force generated by the permanent magnet while being fixed to the semiconductor laser. The optical pickup according to claim 2, further comprising a coil.