JP4272964B2 - Optical disc drive - Google Patents

Description

  The present invention relates to an optical disc drive for reproducing information from an optical disc.

  An optical disk such as a CD-ROM rotates a disk on which information is recorded on a concentric or spiral track, irradiates the track with laser light, receives the reflected light with a light receiving element, and reads the stored information. Is. For this reason, the optical head of the optical disk drive is driven by a servo mechanism in order to accurately irradiate the track with laser light.

  With the recent increase in the density and rotation speed of optical discs, it is required to drive the optical head more accurately. For this reason, a separation type optical head that separates the optical head into a fixed part and a movable part is used.

  The optical head fixing part is fixed to the frame part of the optical disk drive, and has a beam light source, a light receiving part, and an optical system. The optical system guides the beam light from the laser light source to the optical head movable part and guides the beam light reflected on the optical disk to the light receiving part.

  Further, the optical head movable portion can advance and retreat in the disc radial direction of the optical disc. The optical head movable part has an objective lens. The objective lens is disposed close to the disk surface of the optical disk, and condenses the beam light from the beam light source on the optical disk. The beam light reflected on the optical disk enters the objective lens again and returns to the optical head fixing portion. Note that the optical axis direction of the beam light from the optical head fixed part to the optical head movable part is the same as the forward / backward direction of the optical head movable part, so that the beam light from the beam light source is reliably transmitted regardless of the position of the optical head movable part. The beam light incident on the optical head movable part and reflected on the optical disk returns to the optical head fixing part.

  Further, the conventional (non-separable) optical head absorbs the spherical aberration of the objective lens caused by the change in the wavelength of the semiconductor laser or the change in the thickness of the optical disk due to a change in temperature, as disclosed in Patent Document 1, for example. A plurality of correction lenses. The plurality of correction lenses are arranged in series on the optical path of the laser beam, and the light beam is condensed on the optical disk regardless of the temperature by moving at least one of the correction lenses with respect to the other correction lens. be able to.

However, if the correction lens is applied to the conventional separation type optical head, the optical path and the moving direction of the optical head movable portion are the same. As a result, the moving direction of the optical head movable portion and the moving direction of the correction lens are the same. Therefore, the acceleration due to the movement of the movable portion of the optical head is applied to the correction lens, and the direction of the acceleration is the movement direction of the correction lens. For this reason, the positional accuracy of the correction lens is lowered. In recent optical discs with higher density, it is necessary to ensure a higher positional accuracy of the correction lens. Therefore, an optical disc that achieves higher density in the above-mentioned conventional type separation type optical head. It is becoming difficult to read information from.
JP 2002-150598 A

  In view of the above problems, the present invention can absorb the spherical aberration of the objective lens caused by the variation in the wavelength of the semiconductor laser due to the temperature change and the variation in the thickness of the optical disc, and can secure the positional accuracy of the correction lens with high accuracy. It is an object to provide an optical disc drive.

  In order to achieve the above object, an optical disk drive according to the present invention corrects spherical aberration caused by an objective lens fixed to the optical head movable unit and an optical head driving means for moving the optical head movable unit in the first direction. A spherical aberration correction unit, and the spherical aberration correction unit includes a first deflection member that bends the light beam emitted from the optical head fixing portion by 90 degrees and deflects the light beam in a second direction, and a first deflection. A second deflecting member that bends the light beam deflected by the member and deflects the light beam in the first direction to enter the optical head movable portion, and a movable member disposed between the first deflecting member and the second. A correction lens; and a lens driving unit that moves the movable correction lens in the second direction to correct spherical aberration caused by the objective lens.

  According to the present invention, since the moving direction of the optical head movable part and the moving direction of the movable correction lens are orthogonal, the direction of the acceleration applied to the movable lens by the movement of the optical head movable part is orthogonal to the moving direction of the movable lens. To do. Therefore, the acceleration applied to the movable lens by the movement of the movable portion of the optical head hardly affects the position control of the movable lens, and the position control of the movable lens can be performed with high accuracy.

  The second direction may be a direction along the recording surface of the optical disk, or a direction perpendicular to the recording surface of the optical disk.

  Therefore, according to the present invention, it is possible to absorb the spherical aberration of the objective lens caused by the variation in the wavelength of the semiconductor laser due to the temperature change and the variation in the thickness of the optical disc, and the movable correction lens for correcting the spherical aberration and the focal length. It is possible to realize an optical disc drive capable of ensuring the position accuracy of the image with high accuracy.

  FIG. 1 shows the configuration of the optical disk drive according to the first embodiment of the present invention. In the embodiment described below, the direction of each member will be described using xyz orthogonal triaxial coordinates. The optical disc drive 100 includes a frame 101, an optical head fixing unit 110, an optical head movable unit 130, and a spindle motor 140. The optical disc 200 is fixed to the spindle motor 140 and rotates together with the spindle motor 140. Note that the rotation axis of the spindle motor 140 is parallel to the z-axis.

  An optical head fixing unit 110 is fixed to the frame 101 of the optical disc drive 100. The optical head fixing unit 110 includes a laser light source 111, a composite prism assay 112, a light amount monitor element 113, a light receiving element 114, and a deflection mirror 115. In the figure, the alternate long and short dash line is the optical path of the laser beam.

  Laser light emitted from the laser light source 111 passes through the composite prism assay 112, is reflected on the deflection mirror 115, and travels toward the optical head movable unit 130. The optical head movable unit 130 bends the laser light in the rotation axis direction (z-axis direction) of the optical disc 200. The laser beam bent by the optical head movable unit 130 is condensed by the objective lens 133 of the optical head movable unit 130 and projected onto the recording surface of the optical disc 200. The laser beam projected on the recording surface of the optical disc 200 is reflected and returned to the objective lens, and further returns to the optical head fixing unit 110 through the optical head movable unit 130. The laser light returned to the optical head fixing unit 110 is reflected by the deflecting mirror 115 and enters the composite prism assay 112, and further passes through the composite prism assay 112 and enters the light receiving element 114.

  A part of the laser light emitted from the laser light source 111 is branched by the beam splitter in the composite prism assay 112 and directed to the light quantity monitor element 113. The light quantity monitor element 113 is an element that receives a part of the light quantity emitted from the laser light source 111, and its photoelectric output value is proportional to the light quantity of the laser light source 111. That is, a stable laser output can be obtained by feeding back the output of the light quantity monitor element 113.

  In the optical disc 200, information is recorded on concentric tracks. Control means (not shown) of the optical disc drive 100 can irradiate the desired track with the laser light from the objective lens 133 by moving the optical head movable unit 130 in the x-axis direction that is the radial direction of the optical disc 200. Note that the central axis of the laser beam traveling from the optical head fixing unit 110 toward the optical head movable unit 130 and the laser beam traveling from the optical head movable unit 130 toward the optical head fixing unit 110 are parallel to the x axis. Therefore, regardless of the position of the optical head movable unit 130, the laser light traveling from the optical head fixed unit 110 toward the optical head movable unit 130 is surely incident on the optical head movable unit 130, and the optical head movable unit 130 fixes the optical head. The laser beam traveling toward the unit 110 surely enters the optical head fixing unit 110.

  The drive mechanism of the optical head movable unit 130 will be described below. The optical head movable unit 130 includes a carriage 134 on which an optical member such as an objective lens 133 is installed, and coils 131L and 131R attached to both sides of the carriage 134. The optical head movable unit 130 is guided by two guide shafts 122 extending in the x-axis direction and is movable only in the x-axis direction. Further, two center yokes 121L and 121R extending in the x-axis direction are installed on both sides in the y-axis direction of the optical head movable unit 130. Here, center yokes 121L and 121R are inserted into the coils 131L and 131R, respectively, and the coils 131L and 131R are movable along the center yokes 121L and 121R, respectively. Further, U-shaped side yokes 123L and 123R are connected to the outer sides of the center yokes 121L and 121R in the y-axis direction. The connected center yoke and side yoke form four sides of a quadrangle, and a magnet is disposed inside the four sides.

  The coil, yoke, and magnet constitute a so-called voice coil motor. When a current is passed through the coils 131L and 131R, the optical head movable unit 130 can move straight in the x-axis direction by a magnetic force acting between the magnetic field generated in the coil and the magnetic field generated by the magnet. Since the voice coil motor is a known technique (Japanese Patent Laid-Open No. 2000-90598, etc.), detailed description thereof is omitted. Reference numeral 120 denotes a flexible cable for carrying a control signal sent from the control means (not shown) of the optical disk drive 100 to the optical head movable unit 130.

  FIG. 2 shows the optical head fixing unit 110. As shown in FIG. 2, the composite prism assay 112 includes a shaping prism 121a, a first triangular prism 121b, and a second triangular prism 121c.

  The laser light emitted from the laser light source 111 first enters the collimating lens 116 and is converted into a parallel light beam. Next, the laser light is incident on the shaping prism 121a. The laser light source 111 is a semiconductor laser light source, and the parallel light beam has an elliptical cross section due to its characteristics. The incident surface of the shaping prism 121a is inclined at a predetermined angle with respect to the central axis of the laser light, and the laser light incident on the shaping prism 121a is shaped into a substantially circular cross section.

  Next, the laser light is incident on the first prism 121b. The laser light is split into two light beams on the incident surface of the first prism 121b on the laser light source 111 side. One light beam passes through the first prism 121 b and travels toward the deflection mirror 115. The other light beam is reflected on the incident surface of the first prism 121 b and travels toward the light amount monitor element 113.

  On the other hand, the laser beam returning from the optical head movable unit 130 to the optical head 110 is reflected by the change mirror 115 and enters the first prism 121b. The laser beam is reflected by the incident surface of the first prism 121b on the laser light source 111 side and enters the second prism 112c. The laser light reflected by the reflecting surface of the second prism 121 c passes through the light beam separating element 116 and then enters the light receiving element 114 through the focusing lens 117. The light receiving element 114 is a photoelectric element having divided areas, and obtains a control signal and an information signal by an arithmetic circuit (not shown).

  FIG. 3 is an enlarged view of the optical head movable unit 130. As shown in FIG. 3, a spherical aberration correction unit 135 is attached to the front side of the optical head movable unit 130. The spherical aberration correction unit 135 includes a first reflecting prism 135a, a movable lens 135b, a second reflecting prism 135c, and a fixed lens group 135f. The first reflecting prism 135a, the movable lens 135b, and the second reflecting prism 135c are arranged in this order in the y-axis direction. The second reflecting prism 135c and the fixed lens group 135f are arranged side by side in the x-axis direction.

  Laser light emitted from the optical head fixing unit 110 toward the optical head movable unit 130 enters the first reflecting prism 135a. The laser beam is reflected by the incident surface of the first reflecting prism 135a and deflected by 90 degrees so that its optical axis is parallel to the y-axis and travels toward the movable lens 135b. Next, the laser light passes through the movable lens 135b and enters the second reflecting prism. The laser light is reflected by the incident surface of the second reflecting prism 135c and deflected by 90 degrees so that its optical axis is parallel to the x axis and travels toward the fixed lens group 135f. Next, the laser light passes through the fixed lens group 135f, is guided into the carriage 134, and is incident on the deflection mirror 134a disposed in the carriage 134. The laser beam is reflected by the incident surface of the deflecting mirror 134a and deflected by 90 degrees, and its optical axis is parallel to the z-axis and travels toward the objective lens 133.

  As described above, the laser light incident on the objective lens 133 is collected and incident on the optical disc 200, reflected on the optical disc 200, and returned to the objective lens 133. The laser light returned to the objective lens 133 returns to the optical head fixing unit 110 via the deflection mirror 134a, the fixed lens group 135f, the second reflecting prism 135c, the movable lens 135b, and the first reflecting prism 135a in order. In addition, it is good also as a structure which uses a reflective mirror instead of the 1st reflective prism 135a and the 2nd reflective prism 135c.

  The support and drive mechanism of the movable lens 135b will be described below with reference to FIG. FIG. 4 is an enlarged view of the spherical aberration correction unit 135.

  The movable lens 135b is sandwiched and supported by leaf springs 135d and 135e extending from the carriage 134 in the y-axis direction. The ends of the leaf springs 135d and 135e on the carriage 134 side are fixed in slits 134b and 134c formed in the carriage 134, respectively, to form a parallel leaf spring. Therefore, the displacement of the movable lens 135b is limited to the direction and amount in which the leaf spring can be deformed. Specifically, the movable lens 135b is mainly displaced in the bending direction of the leaf spring. That is, the movable lens 135b is greatly displaced in the y-axis direction and is slightly displaced in the bending direction of the leaf spring (x-axis direction). Since the necessary amount of displacement of the movable lens 135b is sufficiently smaller than the length of the leaf springs 135d and 135e in the x-axis direction, the displacement in the x-axis direction accompanying the displacement of the movable lens 135b in the y-axis direction is very small. . Therefore, it can be said that the displacement direction of the movable lens 135b is limited only to the y-axis direction.

  The movable lens 135b is displaced in the y-axis direction by a drive mechanism using a solenoid and a permanent magnet. This drive mechanism will be described below.

  A conductive cable is wound around the movable lens 135b. This cable is wound around the optical axis of the movable lens 135 b and constitutes a solenoid 154. Accordingly, when a direct current is passed through the cable, a magnetic flux in the optical axis direction of the movable lens 135b is generated so as to surround the solenoid 154.

  Further, the two permanent magnets 156a and 156b are arranged so as to be close to the solenoid 154 and sandwich the solenoid 154. The permanent magnets 156a and 156b are arranged side by side in the x-axis direction, and in particular, the permanent magnet 156b is arranged between the leaf springs 135d and 135e. The permanent magnets 156a and 156b are arranged so that the N pole is close to the solenoid 154 and the S pole is separated from the solenoid 154 in the x-axis direction. Accordingly, a magnetic flux in the x-axis direction (direction from the lower right to the upper left in FIG. 4) from the permanent magnet 156a to the solenoid 154 is generated in a portion of the solenoid 154 adjacent to the permanent magnet 156a. Similarly, a magnetic flux in the x-axis direction (the direction from the upper left to the lower right in FIG. 4) from the permanent magnet 156b to the solenoid 154 is generated in a portion of the solenoid 154 adjacent to the permanent magnet 156b.

  In this state, if a current flows through the solenoid 154 so that a current flows from the bottom to the top in the vicinity of the permanent magnet 156a (and so a current flows from the top to the bottom in the figure near the permanent magnet 156b), the Fleming According to the left-hand rule, a force in the y-axis direction is applied to the solenoid 154 so as to displace the movable lens 135b toward the first reflecting prism 135a. On the other hand, when a current is applied to the solenoid 154 so that a current flows from the top to the bottom in the figure in the vicinity of the permanent magnet 156a, a force in the y-axis direction that displaces the movable lens 135b toward the second reflecting prism 135c. Works on solenoid 154.

  The magnitude of the force generated in the solenoid by passing the current through the solenoid 154 is determined by the magnetic flux density passing through the solenoid, the number of turns of the coil, and the magnitude of the current. If the displacement amount of the movable lens 135b is very small, the magnetic flux density passing through the solenoid can be regarded as almost constant regardless of the position of the movable lens 135b. Therefore, the force generated in the solenoid, that is, the force for displacing the movable lens 135b The magnitude can be changed by varying the magnitude of the current.

  The leaf springs 135d and 135e are a kind of cantilever beams having slits 134b and 134c as fulcrums, respectively. Therefore, the amount of deformation of the leaf spring with respect to the force generated in the solenoid is determined by the material, cross-sectional shape, and length of the leaf spring. Since the material, sectional shape, and length of the leaf spring are determined in advance, the amount of deformation of the leaf spring is determined only by the force generated in the solenoid.

  Therefore, the movable lens 135b can be moved to a desired position by changing the current flowing through the solenoid 154. The magnitude of this current is controlled by the control means of the optical disc drive 100, and therefore the control means can move the movable lens 135b to an arbitrary position. The optical head fixing unit 110 is provided with a sensor (not shown) that detects the degree of spherical aberration of the objective lens 133, and the control means corrects the spherical aberration most effectively from the detection result of the sensor. The position of the movable lens 135b is calculated.

  The number and position of permanent magnets are not limited to the configuration of the present embodiment, and any permanent magnets may be used as long as they generate a force in the y-axis direction when a direct current is passed through the cable. For example, the S pole of each magnet may be directed to the solenoid, or the permanent magnets may be arranged in the z-axis direction. Furthermore, it is good also as a structure which arrange | positions a permanent magnet in each of the position which divides the circumference part of a solenoid into 3 equal parts, 4 equal parts, or more.

  As described above, according to the present embodiment, the moving direction of the optical head movable portion and the moving direction of the spherical aberration correcting movable lens 135b are orthogonal to each other, and therefore the movable lens 135b is moved by the movement of the optical head movable portion 130. The direction of acceleration applied to is orthogonal to the moving direction of the movable lens 135b. Therefore, the acceleration applied to the movable lens 135b by the movement of the optical head movable unit 130 hardly affects the position control of the movable lens 135b, and the position control of the movable lens 135b can be performed with high accuracy.

  In the first embodiment of the present invention described above, the movable lens 135b moves in the y-axis direction, that is, in the direction perpendicular to the moving direction of the optical head movable unit 130 and parallel to the disk surface of the optical disk 200. However, the present invention is not limited to the above configuration. That is, other configurations in which the movable lens moves in another direction orthogonal to the moving direction of the optical head movable portion are also included in the present invention. A second embodiment of the present invention described below is an optical disc system having such a configuration.

  The basic configuration of the optical disk drive of this embodiment is the same as that of the first embodiment of the present invention except for the spherical aberration correction unit. Therefore, a detailed description of the basic configuration of the optical disk drive of the present embodiment is omitted. Note that members having the same functions as those in the first embodiment of the present invention are given the same or similar reference numerals as those in the first embodiment of the present invention.

  FIG. 5 is an enlarged view of the optical head movable unit 130 of the present embodiment. As shown in FIG. 5, a spherical aberration correction unit 1135 is attached to the front side of the optical head movable unit 130. The spherical aberration correction unit 1135 includes a first reflecting prism 1135a, a movable lens 1135b, a second reflecting prism 1135c, and a fixed lens group 1135f. The first reflecting prism 1135a, the movable lens 1135b, and the second reflecting prism 1135c are arranged in this order in the z-axis direction. The second reflecting prism 1135c and the fixed lens group 1135f are arranged side by side in the x-axis direction. In the figure, the alternate long and short dash line is the optical path of the laser beam.

  Laser light emitted from the optical head fixing unit 110 toward the optical head movable unit 130 enters the first reflecting prism 1135a. The laser light is reflected by the incident surface of the first reflecting prism 1135a and deflected by 90 degrees, and its optical axis is parallel to the z-axis and travels toward the movable lens 1135b. Next, the laser light passes through the movable lens 1135b and enters the second reflecting prism. The laser light is reflected by the incident surface of the second reflecting prism 1135c and deflected by 90 degrees, and its optical axis is parallel to the x-axis and goes toward the fixed lens group 1135f. Next, the laser light passes through the fixed lens group 1135f, is guided into the carriage 134, and enters the deflection mirror 134a disposed in the carriage 134. The laser beam is reflected by the incident surface of the deflecting mirror 134a and deflected by 90 degrees, and its optical axis is parallel to the z-axis and travels toward the objective lens 133.

  As described above, the laser light incident on the objective lens 133 is collected and incident on the optical disc 200, reflected on the optical disc 200, and returned to the objective lens 133. The laser light returning to the objective lens 133 returns to the optical head fixing unit 110 via the deflection mirror 134a, the fixed lens group 1135f, the second reflecting prism 1135c, the movable lens 1135b, and the first reflecting prism 1135a in this order. Note that a configuration in which a reflection mirror is used instead of the first reflection prism 1135a and the second reflection prism 1135c may be employed.

  The movable lens 1135b is sandwiched and supported by leaf springs 1135d and 1135e extending in the y-axis direction from a protruding portion 1134d protruding from the carriage 134 in the x-axis direction. The support and drive mechanism of the movable lens 1135b will be described below with reference to FIG. FIG. 6 is an enlarged view of the spherical aberration correction unit 1135.

  The end portions of the leaf springs 1135d and 1135e on the projecting portion 1134d side of the carriage 134 are fixed in slits 1134b and 1134c formed in the projecting portion 1134d to form parallel leaf springs. Accordingly, the displacement of the movable lens 1135b is limited to the direction and amount in which the leaf spring can be deformed. Specifically, the movable lens 1135b is mainly displaced in the bending direction of the leaf spring. That is, the movable lens 1135b is greatly displaced in the z-axis direction and is slightly displaced in the bending direction of the leaf spring (y-axis direction). Since the necessary displacement amount of the movable lens 1135b is sufficiently smaller than the length of the leaf springs 1135d and 1135e in the y-axis direction, the displacement in the y-axis direction accompanying the displacement of the movable lens 1135b in the z-axis direction is very small. . Therefore, it can be said that the displacement direction of the movable lens 1135b is limited only to the z-axis direction.

  The movable lens 1135b is displaced in the z-axis direction by a drive mechanism using a solenoid and a permanent magnet. This drive mechanism will be described below.

  A conductive cable is wound around the movable lens 1135b. This cable is wound around the optical axis of the movable lens 1135 b and constitutes a solenoid 154. Accordingly, when a direct current is passed through the cable, a magnetic flux in the optical axis direction of the movable lens 1135b is generated so as to surround the solenoid 154.

  Further, the two permanent magnets 156a and 156b are arranged so as to be close to the solenoid 154 and sandwich the solenoid 154. The permanent magnets 156a and 156b are arranged side by side in the y-axis direction, and in particular, the permanent magnet 156b is arranged between the leaf springs 1135d and 1135e. Further, the permanent magnets 156a and 156b are arranged so that the N pole is close to the solenoid 154 and the S pole is separated from the solenoid 154 in the y-axis direction. Accordingly, a magnetic flux in the y-axis direction (the direction from the upper right to the lower left in FIG. 6) from the permanent magnet 156a to the solenoid 154 is generated in a portion of the solenoid 154 adjacent to the permanent magnet 156a. Similarly, a magnetic flux in the y-axis direction (the direction from the lower left to the upper right in FIG. 6) from the permanent magnet 156b to the solenoid 154 is generated in a portion of the solenoid 154 adjacent to the permanent magnet 156b.

  In this state, if a current is passed through the solenoid 154 so that a current flows from the lower right to the upper left in the vicinity of the permanent magnet 156a (so that a current flows from the upper left to the lower right in the figure near the permanent magnet 156b), According to Fleming's left-hand rule, a force in the z-axis direction that causes the movable lens 1135b to be displaced toward the first reflecting prism 1135a acts on the solenoid 154. On the other hand, when a current is passed through the solenoid 154 so that a current flows from the upper left to the lower right in the vicinity of the permanent magnet 156a, the movable lens 1135b is displaced in the z-axis direction so as to be displaced toward the second reflecting prism 1135c. A force acts on the solenoid 154.

  The magnitude of the force generated in the solenoid by passing the current through the solenoid 154 is determined by the magnetic flux density passing through the solenoid, the number of turns of the coil, and the magnitude of the current. If the displacement amount of the movable lens 1135b is very small, the magnetic flux density passing through the solenoid can be regarded as almost constant regardless of the position of the movable lens 1135b. Therefore, the force generated in the solenoid, that is, the force for displacing the movable lens 1135b The magnitude can be changed by varying the magnitude of the current.

  The leaf springs 1135d and 1135e are a kind of cantilever beams having slits 1134b and 1134c as fulcrums, respectively. Therefore, the amount of deformation of the leaf spring with respect to the force generated in the solenoid is determined by the material, cross-sectional shape, and length of the leaf spring. Since the material, sectional shape, and length of the leaf spring are determined in advance, the amount of deformation of the leaf spring is determined only by the force generated in the solenoid.

  Therefore, the movable lens 1135b can be moved to a desired position by changing the current flowing through the solenoid 154. The magnitude of this current is controlled by the control means of the optical disc drive 100, and therefore the control means can move the movable lens 1135b to an arbitrary position. The optical head fixing unit 110 is provided with a sensor that detects the degree of spherical aberration of the objective lens 133, and the control means is a movable lens that most effectively corrects spherical aberration based on the detection result of the sensor. The position of 1135b is calculated.

  The number and position of permanent magnets are not limited to the configuration of the present embodiment, and any permanent magnets may be used as long as they generate a z-axis direction force when a direct current is passed through the cable. For example, the S pole of each magnet may be configured to face the solenoid, or the permanent magnet may be configured in the x-axis direction. Furthermore, it is good also as a structure which arrange | positions a permanent magnet in each of the position which divides the circumference part of a solenoid into 3 equal parts, 4 equal parts, or more.

  As described above, according to the present embodiment, since the moving direction of the optical head movable portion and the moving direction of the spherical aberration correcting movable lens 1135b are orthogonal, the movable lens 1135b is moved by the movement of the optical head movable portion 130. The direction of acceleration applied to is orthogonal to the moving direction of the movable lens 1135b. Therefore, the acceleration applied to the movable lens 1135b by the movement of the optical head movable unit 130 hardly affects the position control of the movable lens 1135b, and the position control of the movable lens 1135b can be performed with high accuracy.

  In the first embodiment and the second embodiment described above, the reflecting prism 135a is configured so that the moving direction of the movable lens for correcting spherical aberration can be made orthogonal to the moving direction of the optical head movable portion. The laser beam is bent 90 degrees using (1351a in the second embodiment) and 135b (1135b in the second embodiment). However, the present invention is not limited to the above-described configuration, and other means capable of bending the laser light (or other light beam for pickup) may be used instead of the reflecting prism.

  That is, as shown in FIG. 7, the reflection mirrors 160 a and 160 b may be used instead of the reflection prisms 135 a and 135 b (FIG. 4) of the first embodiment. Alternatively, as shown in FIG. 8, a configuration may be adopted in which reflecting mirrors 1160a and 1160b are used instead of the reflecting prisms 1135a and 1135b (FIG. 6) of the second embodiment.

1 is a schematic diagram of an optical disk drive according to a first embodiment of the present invention. It is the schematic of the optical head fixing | fixed part of the 1st Embodiment of this invention. It is the schematic of the optical head movable part of the 1st Embodiment of this invention. It is the schematic of the spherical aberration correction unit of the 1st Embodiment of this invention. It is the schematic of the optical head movable part of the 2nd Embodiment of this invention. It is the schematic of the spherical aberration correction unit of the 2nd Embodiment of this invention. It is the schematic of what used the reflective mirror instead of the reflective prism in the spherical aberration correction unit of the 1st Embodiment of this invention. It is the schematic of using the reflective mirror instead of the reflective prism in the spherical aberration correction unit of the 2nd Embodiment of this invention.

Explanation of symbols

100 Optical disk drive 110 Optical head fixing unit 130 Optical head movable unit 134 Carriage 135 Spherical aberration correction unit 135a First reflective prism 135b Movable lens 135c Second reflective prism 135d Plate spring 135e Plate spring 154 Solenoid 156a Permanent magnet 156b Permanent magnet 160a Reflection mirror 160b Reflection mirror 200 Optical disc

Claims (4)

An optical head movable part equipped with an objective lens for condensing a light beam on the recording surface of the optical disc;
An optical head fixing unit that irradiates the optical head movable unit with a light beam in a first direction along the recording surface of the optical disc and receives the light beam reflected by the recording surface of the optical disc;
An optical head driving means for moving the optical head movable portion in the first direction;
A spherical aberration correction unit that is fixed to the optical head movable portion and corrects spherical aberration due to the objective lens;
Have
The spherical aberration correction unit is
A first deflecting member that bends the light beam emitted from the optical head fixing portion by 90 degrees and deflects the light beam in a second direction;
A second deflecting member that bends the light beam deflected by the first deflecting member and deflects the light beam in the first direction so as to enter the movable optical head;
A movable correction lens disposed between the first deflection member and the second deflection member;
It said movable correction lens is moved in the second direction to correct the spherical aberration by the objective lens, and a lens driving means,
The optical disk drive according to claim 1, wherein the second direction is a direction along a recording surface of the optical disk.   2. The optical disc drive according to claim 1, wherein the first and second deflecting members are prisms.   2. The optical disk drive according to claim 1, wherein the first and second deflecting members are reflection mirrors. The spherical aberration correcting unit further wherein a second deflecting member disposed between the objective lens, an optical disk drive according to any one of claims 1 to claim 3, characterized in that it has a fixed correction lens .

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