JP4138605B2 - Optical pickup - Google Patents

Description

  The present invention relates to an optical pickup capable of recording on a recording medium such as an optical disk and / or reproducing a recording medium such as an optical disk.

  As the recording density of optical discs increases, optical discs of various standards are used. For example, in addition to a CD (compact disc) family that records and reproduces signals with light having a wavelength of 780 nm, optical discs of a plurality of standards related to a DVD (digital video disc) that records and reproduces signals with light having a wavelength of 650 nm are also available. It is used. Furthermore, the standard of recording and reproducing signals with light having a wavelength of 405 nm and the light having the same wavelength of 405 nm are used without changing the NA (numerical aperture) of the DVD objective lens. Also, Blu-ray Disk (registered trademark, hereinafter referred to as BD), which has a cover glass thickness as thin as 0.1 mm and an objective lens with an NA as high as 0.85, has appeared. An optical pickup for recording and reproducing these plural types of optical discs by one unit is necessary, and several proposals have been made.

  The proposal trend is divided into two directions. One is a direction corresponding only to an optical disc in which the difference in the cover glass thickness falls within the conventional compatible technology range. The other is a direction in which the NA of the condensing lens is as high as 0.85 and the cover glass is as thin as 0.1 mm so that it can cope with BD. In this case, a pickup that exceeds the range of the conventional compatible technology is configured.

  As a technique in the former direction, there is one in which three light sources disclosed in Patent Document 1 are configured as one optical pickup. In this optical pickup, light sources having wavelengths of 430 nm, 635 nm, and 780 nm are used. As shown in FIG. 21, the light source 401 disclosed in Patent Document 1 is a combination of three light sources 401a to 401c each having a different wavelength, and the light emitted from the light source 401 is 1 The light is condensed by the individual objective lenses 404. However, in this case, since there is one objective lens 404, the relationship between the NA of the objective lens 404, the wavelength of the light source, and the cover glass thickness is determined as one combination. That is, for a wavelength of 430 nm, the NA of the objective lens is 0.65 and the cover glass thickness is 0.3 mm, and for a wavelength of 635 nm, the NA of the objective lens is 0.65 and the cover glass thickness is 0. .6 mm, and for a wavelength of 780 nm, the NA of the objective lens is 0.65 and the cover glass thickness is 1.2 mm.

On the other hand, as a technique for constructing an optical pickup having a cover glass with a thickness of 0.1 mm and adapted to an optical disc such as a BD, one having two objective lenses has been proposed. That is, for an optical disc such as a BD having a cover glass with a thickness of 0.1 mm, recording or reproduction is performed using an objective lens different from that for recording or reproducing an optical disc having a cover glass with another thickness. I try to play it. Also, it has been proposed to divide the optical system into two and mount two different lenses on an actuator which is a lens driving device. In this system, one optical system is specialized for BD.
JP-A-11-134702

  For example, a case where recording or reproduction of optical disks having different readout wavelengths and different cover glass thicknesses such as BD, DVD, and CD is performed with one optical pickup will be considered.

  First, when the pickup is configured so as to correspond to the three types of optical disks of high density DVD, DVD and CD described in Patent Document 1 with one objective lens, there is one objective lens. As described above, the relationship between the NA of the objective lens, the wavelength, and the cover glass thickness is determined by one combination. For this reason, it is apparent that this cannot be applied to a BD having a wavelength of 405 nm, an objective lens NA of 0.85, and a cover glass thickness of 0.1 mm. Considering the extension of the technique described in Patent Document 1, a method of inserting an optical phase compensation element into the optical system can be considered in order to compensate for the difference in the thickness of the cover glass and the NA of the objective lens. The cover glass thickness is 0.6 mm and 1.2 mm for DVD and CD with respect to 0.1 mm for BD, which is greatly different from 6 times or 12 times for BD. The NA of the objective lens is also different. Due to these factors, if an attempt is made to provide a wavefront conversion function for recording or reproducing all optical disks, a lens system suitable for the function becomes extremely complicated.

  On the other hand, a method of configuring an independent optical system for BD, separately providing different optical systems for other optical disks, separating the optical system into two, and mounting two lenses on the actuator However, there are the following problems. In order to drive two lenses, the lens holder portion becomes heavy, and the performance required for the actuator becomes severe. Further, for a BD having a thin cover glass, since the light is condensed by a high NA lens, it is necessary to cause the actuator to follow in the vicinity of the optical disk. On the other hand, in DVD and CD, it is necessary to follow the actuator at a position farther from the optical disc than in the case of BD. The actuator is required to have the highest tracking performance in order to achieve the performance for recording and playback of BDs. There are a lot of restrictions and it is extremely difficult. Further, there is a problem that the actuator is further increased in size as compared with the case where it is configured for BD alone.

  Accordingly, the present invention has been made to solve the above-described problem, and in an optical pickup having light sources of three different wavelengths, suitable recording without incurring an increase in the size of a lens driving device such as an actuator. An object of the present invention is to provide an optical pickup capable of recording and / or reproducing various disks having different reproduction wavelengths.

According to the optical pickup based on the present invention, the first optical disc, the second optical disc, and the third optical disc, which have different cover glass thicknesses and different wavelengths of light, can be used. The optical pickup is configured to emit information and record or reproduce information. A first light source that emits light having a wavelength suitable for the first optical disc; a first condenser lens that condenses the light emitted from the first light source on the first optical disc; A lens driving device that drives the first condenser lens with a magnet, a base portion that directly supports the magnet of the lens driving device, reflected light from the first optical disc, and output light from the first light source; A first optical system having a first light branching portion that branches in different directions and a first light receiving element that detects branched light from the first light branching portion is provided. In addition, a second light source that emits light having a wavelength suitable for the second optical disk, a third light source that emits light having a wavelength suitable for the third optical disk, and an output from the second light source. A second condensing lens that condenses the emitted light and the emitted light from the third light source on the second optical disc and the third optical disc, respectively, and a light control unit that changes the condensing position of the second condensing lens A second light branching unit for branching reflected light from the second optical disk and the third optical disk in a direction different from that of the light emitted from the second light source and the third light source; A second optical system having a second light receiving element for detecting the branched light from the light branching unit. Further, in the second optical system, the optical axis from the second light source to the second condensing lens and the optical axis from the third light source to the second condensing lens define the base portion of the base portion. The light control unit is configured to pass through a through hole penetrating in a direction substantially perpendicular to the surface, and the light control unit is stored in the through hole of the base unit.

  In the optical pickup described above, different condensing lenses are used for the first optical system and the second optical system, and the driving devices for the lenses are also different. For example, an optical system having a high NA condensing lens corresponding to BD can be used as the first optical system, and an optical system corresponding to CD, DVD, or the like can be used as the second optical system. Since the high-NA condenser lens in the first optical system is driven independently by the lens driving device, the performance of the lens driving device can be maximized.

  Further, at least a part of the optical axis of the second optical system passes through the base part that supports the lens driving device that drives the first optical system, and at least a part of the light control part is fixed to the base part. Therefore, the optical pickup can be made compact. Further, since the first optical system and the second optical system can be positioned with reference to the base portion, the mounting thereof is easy.

  Preferably, in the optical pickup, the light control unit is configured such that the second light source, the third light source, the second condenser lens, the second light branching unit, and the second light receiving element are directly or An indirectly fixed housing part and a magnet for generating a magnetic force for driving the housing part are included, and the magnet is fixed to the base part.

  According to this configuration, the casing fixed to the entire second optical system is driven by the magnet fixed to the base, so that the entire second optical system can be driven.

  Preferably, in the optical pickup, the light control unit includes a housing in which the second light source, the third light source, the second light branching unit, and the second light receiving element are directly or indirectly fixed. A lens holder for holding the second condenser lens, and the magnet are fixed to the base portion.

  According to this configuration, since the second condenser lens is fixed to the base portion via the lens holder, the light control unit does not drive the lens. As a result, the center of gravity of the movable portion is lowered, and more stable control in the focus direction is possible.

  More preferably, in the optical pickup, the housing portion is configured to be slidable via a shaft with respect to the base portion, and the shaft is coupled to the base portion, and At least a part of the shaft is stored in the base portion.

  According to this configuration, the casing portion is positioned by the shaft connected to the base portion. The lens driving device that drives the condenser lens of the first optical system is fixed to the base portion, and the first optical system and the second optical system can share a reference. Thereby, the shift of the optical axis in the first optical system and the second optical system can be further reduced. Further, since at least a part of the shaft is stored in the base portion, the optical pickup can be configured compactly.

  Preferably, in the optical pickup, the light control unit is configured such that the second light source, the third light source, the second condenser lens, the second light branching unit, and the second light receiving element are directly or From the indirectly fixed casing, the magnet for generating magnetic force for driving the casing in a uniaxial direction, the second light source and the third light source built in the casing An optical deflection element that changes the direction of the emitted light of the first optical system, the guide unit limiting movement of the housing unit only to a direction parallel to the optical axis of the second optical system, the magnet, and the optical deflection. A control unit for controlling the element is fixed to the base unit.

  According to this configuration, the guide unit restricts the movement of the housing unit in a direction parallel to the optical axis of the second optical system, so that more stable control of the second optical system in the focus direction is possible. . Moreover, since it is sufficient to deal with only one direction, it is possible to simplify the arrangement of magnets and the like that are fixed to the base portion.

  Preferably, in the optical pickup, the light control unit is configured such that the second light source, the third light source, the second condenser lens, the second light branching unit, and the second light receiving element are directly or A housing part that is indirectly fixed, a light deflection element that changes the direction of light emitted from the second light source and the third light source, and a light output from the second light source and the third light source. A control unit that includes a wavefront conversion element that changes the spread of incident light, controls the light deflection element, and the housing part is fixed to the base part.

  According to this configuration, an apparatus for mechanically driving the second optical system is not necessary, and thus the focus direction and the radial direction in the second optical system can be controlled with a simple structure.

  According to the present invention, in an optical pickup having light sources of three different wavelengths, recording and / or reproduction of various disks having different suitable recording and reproducing wavelengths is performed without causing an increase in the size of a lens driving device such as an actuator. be able to.

(Embodiment 1)
Hereinafter, the optical pickup according to the first embodiment will be described with reference to FIGS. 1 is a plan view showing the structure of the optical pickup in the present embodiment, FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1, and FIG. 3 is an arrow along the line III-III in FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. 1, and FIG. 5 is a sectional view taken along line VV in FIG.

  In the following description, the wavelength of a light source that is currently used mainly as an optical pickup will be considered. In this embodiment, as an example, a laser having a wavelength of 405 nm corresponding to BD is used as the first light source, a light source having a wavelength of 650 nm corresponding to DVD is used as the second light source, and a wavelength of 780 nm corresponding to CD is used as the third light source. A case of using the light source will be described. The second light source and the third light source will be described using a two-wavelength single laser having two different light emitting points as the light source. However, a single laser configured separately is used. May be.

  As shown in FIG. 1, light having a wavelength of 405 nm emitted from the first light source 1 is converted into parallel light by a lens 4 (in this example, a collimator lens), and is passed through an optical branching element 2 made of, for example, a beam splitter. The light is condensed on the optical disk by one condenser lens 10. The reflected light from the optical disk is branched at this time by the light branching element 2 and enters the first light receiving element 3 through the condenser lens 5 and the cylindrical lens 6. As the first light receiving element 3, for example, an amplifying circuit built-in type light receiving element can be used.

  The lens driving device for driving the first condenser lens 10 in the direction of the optical axis of the light emitted from the first condenser lens 10 to the optical disk and the radial direction of the optical disk is constituted by an actuator 40 here. ing. The actuator 40 is provided with a magnet 14 on the base portion 11, and as shown in FIG. 1, the first condenser lens 10 is stored in the lens holder 13, and the lens holder 13 is attached to the power supply substrate 15. It is configured to be supported by a leaf spring 16. As described above, the first optical system is configured.

  As shown in FIG. 2, with respect to the housing 8, in addition to the rising mirror 7, the light branching element 2 including a beam splitter, the lens 4, and the light source 1 are disposed. Although not shown in FIG. 2, the first light receiving element 3, the condenser lens 5, and the cylindrical lens 6 are also arranged with reference to the housing 8. As shown in FIG. 2, the portion where the light source exists and the portion where the actuator 40 exists exist independently in the vertical direction in FIG. 2, and are in the vertical direction, that is, substantially perpendicular to the base portion 11. The optical path length in the direction is long.

  Although not shown in FIGS. 1 and 2, when a BD is used as an optical disk, a beam shaping prism that changes the beam shape may be provided between the lens 4 and the optical branching element 2. The light branching element 2 is a PBS (polarized beam splitter). In addition, a quarter-wave plate and a beam expander (or aberration compensating liquid crystal element) are provided between the optical branching element 2 made of PBS and the first condenser lens 10. With this quarter-wave plate, light incident on the BD can be circularly polarized, and extra aberration such as spherical aberration caused by BD cover glass thickness error in the beam expander (or aberration compensation liquid crystal element). Can be canceled. Further, an objective lens having a very high NA of 0.85 is used for the first condenser lens.

  The base portion 11 is formed with a through hole 12 for arranging the second optical system. The second optical system is an optical system for reproducing the optical disc by light from the second light source or the third light source.

  As shown in FIG. 3, the second optical system is formed using a through hole 12 in a direction substantially perpendicular to the surface of the base portion 11. The light source 21 serves as both the second light source and the third light source, and can emit light of two types of wavelengths from the light source 21. The light having a wavelength of 650 nm or the light having a wavelength of 780 nm emitted from the light source 21 is condensed on the optical disk by the second condenser lens 20 through the lens 24 composed of an NA conversion lens here. Here, an objective lens capable of condensing light of different wavelengths at different positions is used as the second condenser lens 20. The light collected on the optical disk is reflected, and the reflected light is diffracted by the diffraction element 22 as the second light branching portion and enters the second light receiving element 23.

  Here, both the light from the second light source and the light from the third light source are incident on the second light receiving element 23. In this embodiment, the second light receiving element 23 is constituted by an integrated light receiving and emitting unit housed in the package 25 together with the light source 21. Further, since the diffraction element 22 records and reproduces a DVD as an optical disk, the diffraction element 22 may be a diffraction element having polarization dependency using a liquid crystal having a function of a quarter-wave plate (hereinafter referred to as a polarization hologram). . By using this polarization hologram, the optical system for reproducing a DVD or CD using the light source 21 that also serves as the second and third light sources can be further simplified. As shown in FIG. 4, a coil 29 is provided on the outer periphery of the housing portion 26 that houses the second optical system, and the housing portion 26 is driven by energizing the coil 29.

  Hereinafter, the operation at the time of recording / reproducing in the optical pickup of the present embodiment will be described. As shown in FIG. 5, light having a wavelength of 405 nm emitted from the first light source 1 is condensed on the BD optical disc 51 via the corresponding first condenser lens 10. This first condenser lens is driven by an actuator 40 (only the periphery of the lens holder 13 is shown in FIG. 5). Further, light having a wavelength of 650 nm or 780 nm emitted from the light source 21 that also serves as the second and third light sources is condensed on the optical disk 52 (DVD or CD) via the second condenser lens 20. The reflected light from the optical disk 52 is branched by the diffraction element 22 and detected by the second light receiving element 23.

  The first condenser lens 10 is driven by an actuator 40 that ensures follow-up so as to be appropriate at the time of recording and reproducing BD. Therefore, the performance of the actuator 40 can be the same as the performance of the optical pickup that reproduces only BD.

  On the other hand, when reproducing a DVD or CD, the main part of the second optical system including the light source 21, the second condenser lens 20, the diffraction element 22, and the light receiving element 23 is housed in the casing 26. The second optical system is driven in the focus direction and the disk radial direction together with the casing unit 26.

  The driving device (light control unit) of the housing portion 26 is disposed in the through hole 12 formed in a direction substantially perpendicular to the surface of the base portion 11. The housing portion 26 can be driven by a magnet 28 attached to the base portion 11 and a coil 29 attached so as to be wound around the housing portion 26. The housing portion 26 is provided with a sliding portion 27 through which the sliding shaft 30 formed in the base portion 11 passes. The casing 26 is capable of linear movement in the longitudinal direction of the sliding shaft 30 and rotational movement about the sliding shaft 30.

  With this configuration, the actuator 40 that drives the high-NA first condenser lens 10 can be controlled in the focus direction and the radial direction in the second optical system without any change. It can be performed. Thereby, the performance of the lens driving device in the first optical system can be maximized. In addition, since the light control unit that drives the second optical system is stored in the base unit 11 to which the actuator 40 is fixed, the enlargement of the projection area of the entire optical pickup can be minimized.

  Further, the sliding shaft 30 is provided so as to be connected to the base portion 11, and the lens holder 13 and the like of the actuator 40 are attached with the base portion 11 as a reference. Accordingly, it is possible to reduce the deviation between the movement of the first condenser lens 10 in the optical axis direction and the movement of the casing 26 that houses the main part of the second optical system in the optical axis direction.

(Embodiment 2)
Next, the second embodiment will be described with reference to FIGS. In the description of the present embodiment, the configuration different from that of the first embodiment will be mainly described. Components having the same functions as those in the first embodiment are given the same reference numerals, and the description thereof will not be repeated. Here, FIG. 6 is a plan view showing the structure of the optical pickup in the present embodiment, FIG. 7 is an end view taken along arrow VII-VII in FIG. 6, and FIG. 8 is a view taken along line VIII-VIII in FIG. It is sectional drawing which shows the housing | casing part of an arrow cross section, and the structure of the circumference | surroundings.

  In the present embodiment, the configuration of the first optical system that condenses the light emitted from the light source 1 by the first condenser lens 10 and records / reproduces it on the optical disc is the same as that of the first embodiment.

  Regarding the configuration of the second optical system that uses the second condenser lens 20 to condense the light emitted from the light source 21 serving as the second and third light sources onto the optical disc for recording and reproduction, Different from Form 1. As shown in FIG. 6, the second condenser lens 20 is fixed to the lens holder 31. The lens holder 31 includes a horizontal plate that directly holds the second condenser lens 20, and a vertical plate that is connected to both ends of the lens holder 31 and fixes the horizontal plate to the base portion 11. The second condenser lens 20 is always stationary with respect to the base portion 11 by being fixed by the lens holder 31 in this way.

  The light emitted from the light source 21 serving as both the second light source and the third light source is condensed on the optical disk by the second condenser lens 20 via the NA conversion lens 24. The reflected light from the optical disk is branched by the diffraction element 22 to become diffracted light, and is received by the second light receiving element 23. Of the main part of the second optical system configured as described above, the rest except the second condenser lens 20 is a package 25 in which the light source 21 and the light receiving element 23 are accommodated as shown in FIG. At the same time, it is housed in the casing 26 and driven integrally.

  As described above, the lens holder 31 for fixing the second condenser lens 20 can be attached to the base portion 11 to which the actuator 40 for driving the first condenser lens 10 is fixed. Thereby, the through-hole 12 provided in the base part 11 can be made smaller than the through-hole in Embodiment 1. This is because the casing portion 26 itself is designed to be slimmer than in the case of the first embodiment because the casing portion 26 is configured not to store the second condenser lens 20.

  Similarly to the first embodiment, the housing 26 is driven by attaching a magnet 28 to the base 11 and energizing a coil (not shown) attached to the housing 26. Further, similarly to the first embodiment, the housing portion 26 is provided with a sliding portion 27 through which the sliding shaft 30 formed in the base portion 11 passes.

  According to the configuration of this embodiment, the center of gravity of the housing portion 26 as the movable portion with respect to the sliding shaft 30 is lowered, and control in a more stable focus direction is possible.

  Similarly to the first embodiment, the sliding shaft 30 is formed to be connected to the base portion 11, and the lens holder 13 of the actuator 40 and the like are attached based on the base portion 11. Accordingly, it is possible to reduce a deviation between the movement of the first condenser lens 10 in the optical axis direction and the movement of the casing 26 in the optical axis direction.

(Embodiment 3)
Next, Embodiment 3 will be described with reference to FIGS. In the description of the present embodiment, the configuration different from that of the first embodiment will be mainly described. Components having the same functions as those in the first embodiment are given the same reference numerals, and the description thereof will not be repeated. Here, FIG. 9 is a plan view showing the structure of the optical pickup in the present embodiment, FIG. 10 is an end view taken along the line XX in FIG. 9, and FIG. 11 shows the structure of the optical device. FIG. 12 is an enlarged view, FIG. 12 is an enlarged view showing the wiring structure of the control unit and the optical device, and FIG. 13 is a plan view showing the positional relationship between the base part and the housing part.

  Also in the present embodiment, as shown in FIG. 9, the configuration of the first optical system that condenses the light emitted from the light source 1 by the first condenser lens 10 and records / reproduces it on the optical disk is the same as the embodiment. 1 is the same.

  On the other hand, with respect to the configuration of the second optical system that uses the second condenser lens 20 to condense the light emitted from the light source 201 serving as the second and third light sources onto the optical disc for recording and reproduction, Different from the configuration of the first embodiment. In the third embodiment, the optical device 200 configured integrally with the light source 201 is provided. The optical device 200 includes a light source 201 serving as both a second light source and a third light source, and an optical deflection element 202 having a function of moving emitted light from the light source in the direction of the arrow in FIG. 11 (the left-right direction in FIG. 11). It is constituted by. The movement of the condensing point in the radial direction of the optical disk is realized by the optical device 200 constituting the light source portion. That is, the light emitted from the light source 201 passes through the inside of the optical device 200, and the condensing point is moved by changing the emission position from the optical device 200 at that time.

  Here, the light emitted from the light source 201 serving as both the second light source and the third light source is condensed on the optical disc by the second condenser lens 20 via the NA conversion lens 24. The reflected light from the optical disk is branched by the diffraction element 22 to become diffracted light, and is received by the second light receiving element 23. The main part of the second optical system configured as described above is housed in the housing part 26. In addition, a driving device that drives the housing portion 26 includes the base portion 11, the housing portion 26, and a magnet 28. However, in the present embodiment, unlike the first embodiment, the drive device that drives the housing portion 26 performs only control of the focus direction.

  Accordingly, in the through hole 12 provided in the base portion 11, the gap between the inner surface of the through hole 12 and the housing portion 26 is such that the inner surface of the through hole 12 is different from the guide portion of the housing portion 26. It is made small enough. Here, by making the inclination prevention direction by the housing part 26 and the through hole 12 orthogonal to the inclination prevention direction by the sliding shaft 30 and the sliding part 27, a sliding mechanism that is more resistant to inclination can be obtained. Realize. This structure will be described with reference to FIG.

  In the V direction in FIG. 13, the inclination is minimized by making the gap between the through hole 12 and the housing portion 26 as small as possible. Here, the outer surface of the housing portion 26 is configured to have an elliptical horizontal cross section, and a relatively large gap is formed in the direction orthogonal to the V direction to facilitate sliding. Yes. On the other hand, the sliding shaft 30 and the sliding portion 27 have a gap in the W direction as small as possible, thereby minimizing the inclination in the W direction. Since the X direction and the W direction are orthogonal to each other, the casing portion 26 can minimize the inclination with respect to the base portion 11. Here, a guide portion is configured by the outer surface of the housing portion 26, the inner surface of the through hole 12, the sliding shaft 30, and the sliding portion 27. With this configuration, the housing unit 26 can be driven in a stable focus direction.

  As shown in FIG. 11, the light deflection element 202 constituting the optical device 200 is an element that controls the traveling direction of light by changing the refractive index of the refracting portions 250 a to 250 d by the electro-optic effect. The light traveling direction is controlled by applying a voltage. Here, in order to control the light deflection element 202, a control circuit 261 as a control unit is provided on the back surface of the base unit 11. The control circuit 261 and the optical deflection element 202 are connected by a cable 262 via a laser mount portion 263.

  By changing the traveling direction of the light by the light deflecting element 202, the light source moves relatively when viewed from the second condenser lens 20. Thereby, the condensing point of the light emitted from the second condensing lens 20 also moves. Accordingly, if the moving direction is set to a direction perpendicular to the track of the optical disk, the position of the condensing point can be controlled in the radial direction of the optical disk, that is, in the radial direction.

(Embodiment 4)
Next, Embodiment 4 will be described with reference to FIGS. In the description of the present embodiment, the configuration different from that of the first embodiment will be mainly described. Components having the same functions as those in the first embodiment are given the same reference numerals, and the description thereof will not be repeated. Here, FIG. 14 is a plan view showing the structure of the optical pickup in the present embodiment, FIG. 15 is an end view taken along arrow XIV-XIV in FIG. 14, and FIG. 16 shows the structure of the optical device. 17 is an enlarged view, FIG. 17 is a perspective view showing the structure of the wavefront conversion element, FIG. 18 is an explanatory view showing the function of the wavefront conversion element, and FIG. 19 is an enlarged view of a part of the wavefront conversion element. FIG. 20 is an enlarged view showing a wiring structure of the control unit and the optical device.

  Also in the present embodiment, as shown in FIG. 14, the configuration of the first optical system that condenses the light emitted from the light source 1 by the first condenser lens 10 and records / reproduces it on the optical disk is the same as the embodiment. 1 is the same.

  On the other hand, regarding the configuration of the second optical system that records and reproduces the light emitted from the light source 301 serving as the second and third light sources on the optical disk by using the second condenser lens 20, Different from the configuration of the first embodiment. In the fourth embodiment, an optical device 300 configured integrally with the light source 301 is provided.

  Further, in the present embodiment, the casing 26 is not mechanically driven. For this reason, the housing portion 26 is fixed to the base portion 11 while being inserted into the through hole 12 of the base portion 11. Further, the casing portion 26 of the present embodiment is not provided with a coil that is provided in the casing portion 26 in the above embodiment. In the present embodiment, control of the focusing point of the second focusing lens 20 in the focusing direction (control of the focusing point on the optical disc in the optical axis direction) and control in the radial direction (tracking to the optical disc) Is controlled by the optical device 300.

  Thereby, control to the focus direction of a condensing point and control to a radial direction can be performed with the simplest form. Furthermore, it is only necessary to mount the control unit of the optical device on the base unit 11, and the slide shaft provided in the above embodiment is not necessary, so that the space of the base unit 11 can be further reduced. Note that the control of the condensing point in the focus direction in this case is much easier to realize than compensating for the large difference in cover glass thickness described above.

  The operation of this optical device 300 will be described below. As shown in FIG. 16, the optical device 300 includes a light source 301, a light deflection element 302, and a wavefront conversion element 330. The optical deflection element 302 has the same function as the optical deflection element 202 of the optical device 200 of the third embodiment. As shown in FIG. 16, the wavefront conversion element 330 has a function of changing the spread angle of the light emitted from the light source 301. In this way, by changing the divergence angle, the curvature of the wavefront of the light entering the second condenser lens 20 through the NA conversion lens 24 is slightly changed, and accordingly the condensing point of the second condenser lens 20 is changed. Will also move in the direction of the optical axis.

  Here, an example of the wavefront conversion element 330 will be described. The wavefront conversion element 330 described here uses liquid crystal. In the wavefront conversion element 330, a phase shift is given to incident light according to the distance from the center thereof. Therefore, as shown in FIG. 17, the elements are arranged concentrically. Even when the light incident on the wavefront conversion element 330 with the same phase is the plane wave WFin, when the light passes through the wavefront conversion element 330, the emitted light changes to a spherical wave WFo as shown in FIG. As this element, a device in which minute liquid crystal cells 331 capable of electrically changing the refractive index are arranged in a matrix as shown in FIG. 19 can be used.

  Further, the light deflection element 302 and the wavefront conversion element 330 are controlled via the power feeding unit 340 by a control circuit 361 as a control unit provided in the base 311. As shown in FIG. 20, one end of a cable 362 is connected to the control circuit 361. The other end of the cable 362 is connected to the laser mount unit 363, and a control signal from the control circuit 361 is transmitted to the power supply unit 340 shown in FIG. 16 via the cable 362 and the laser mount unit 363.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It does not become the basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the claims. Further, all modifications within the meaning and scope equivalent to the scope of the claims are included.

It is a top view which shows the structure of the optical pick-up in Embodiment 1 based on this invention. It is II-II arrow sectional drawing in FIG. It is an III-III arrow end view in FIG. FIG. 4 is a sectional view taken along arrow IV-IV in FIG. 1. It is a VV arrow sectional view in FIG. It is a top view which shows the structure of the optical pick-up in Embodiment 2 based on this invention. It is an VII-VII arrow end view in FIG. It is sectional drawing which shows the housing | casing part of the VIII-VIII arrow cross section in FIG. 6, and the surrounding structure. 6 is a plan view showing a structure of an optical pickup according to Embodiment 3. FIG. FIG. 10 is an end view taken along the line XX in FIG. 9. It is an enlarged view which shows the structure of an optical device. It is an enlarged view which shows the wiring structure of a control part and an optical device. It is a top view which shows the positional relationship of a base part and a housing | casing part. FIG. 10 is a plan view showing a structure of an optical pickup in a fourth embodiment. It is a XV-XV arrow end view in FIG. It is an enlarged view which shows the structure of an optical device. It is a perspective view which shows the structure of a wavefront conversion element. It is explanatory drawing which shows the function of a wavefront conversion element. It is the front view which expanded a part of wavefront conversion element. It is an enlarged view which shows the wiring structure of a control part and an optical device. It is a figure which shows the structure of the conventional optical pick-up.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 1st light source, 3 1st light receiving element, 10 1st condensing lens, 11 base part, 13 Lens holder, 20 2nd condensing lens, 21, 201, 301 Light source (2nd light source, 1st 3 light source), 23 second light receiving element, 26 casing, 28 magnet, 30 sliding shaft (axis), 31 lens holder, 40 actuator (lens driving device), 51, 52 optical disc, 202, 302 light deflection Element, 261, 361 Control circuit (control unit), 330 Wavefront conversion element.

Claims (6)

Light that records or reproduces information by emitting light of a wavelength suitable for each optical disc to the first optical disc, the second optical disc, and the third optical disc, each having a different cover glass thickness and different wavelength of the suitable light A pickup,
A first light source that emits light having a wavelength suitable for the first optical disc, a first condenser lens that condenses the emitted light from the first light source on the first optical disc, and the first A lens driving device for driving the condenser lens of the lens with a magnet, a base portion directly supporting the magnet of the lens driving device , and a direction in which reflected light from the first optical disc is different from light emitted from the first light source A first optical system having a first light branching part that branches into a first light receiving part and a first light receiving element that detects a branched light from the first light branching part,
A second light source that emits light having a wavelength suitable for the second optical disk, a third light source that emits light having a wavelength suitable for the third optical disk, light emitted from the second light source, and A second condensing lens that condenses the emitted light from the third light source on the second optical disc and the third optical disc, respectively, a light control unit that changes the condensing position of the second condensing lens, A second light branching section for branching reflected light from the second optical disk and the third optical disk in a direction different from the light emitted from the second light source and the third light source; and the second light A second optical system having a second light receiving element for detecting branched light from the branching unit,
In the second optical system, the optical axis from the second light source to the second condensing lens and the optical axis from the third light source to the second condensing lens are arranged so that the base portion is on the surface of the base portion. Configured to pass through a through-hole penetrating in a substantially vertical direction ,
An optical pickup in which the light control unit is housed in the through hole of the base unit. The light control unit includes a housing in which the second light source, the third light source, the second condensing lens, the second light branching unit, and the second light receiving element are directly or indirectly fixed. Including a body part and a magnet for generating a magnetic force for driving the housing part,
The optical pickup according to claim 1, wherein the magnet is fixed to the base portion. The light control unit includes a housing unit in which the second light source, the third light source, the second light branching unit, and the second light receiving element are directly or indirectly fixed, and the housing unit Including a magnet for generating a magnetic force for driving
The optical pickup according to claim 1, wherein the lens holder that holds the second condenser lens and the magnet are fixed to the base portion.   The housing portion is configured to be slidable with respect to the base portion via a shaft, the shaft is coupled to the base portion, and at least a part of the shaft is The optical pickup according to claim 2, wherein the optical pickup is stored in a unit. The light control unit includes a housing in which the second light source, the third light source, the second condenser lens, the second light branching unit, and the second light receiving element are directly or indirectly fixed. A body, a magnet for generating a magnetic force for driving the casing in a uniaxial direction, and a direction of light emitted from the second light source and the third light source built in the casing An optical deflection element to be
A guide unit that restricts movement of the housing unit only in a direction parallel to the optical axis of the second optical system, the magnet, and a control unit that controls the light deflection element are fixed to the base unit. The optical pickup according to claim 1, wherein the optical pickup is provided. The light control unit includes a housing in which the second light source, the third light source, the second condensing lens, the second light branching unit, and the second light receiving element are directly or indirectly fixed. A body part, a light deflection element that changes the direction of light emitted from the second light source and the third light source, and the second
And a wavefront conversion element that changes a spread of light emitted from the third light source,
The optical pickup according to claim 1, wherein a control unit that controls the optical deflection element and the housing unit are fixed to the base unit.

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