JP2007184064A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device capable of reducing an electric load on an actuator in the optical pickup device in which recording and reproducing for a plurality of kinds of optical recording media can be performed, comatic aberration occurs in a specific direction in recording or reproducing at least one of them, and comatic aberration is corrected using the actuator with a tilt function. <P>SOLUTION: An objective lens actuator 11 mounted with an objective lens 8 for condensing an optical beam emitted from a light source to the recording surface of an optical disc 10 is tilted to an axis 30 perpendicular to the recording surface, and this makes an optical axis 8a of the objective lens 8 tilted by θs in the direction for correcting the specific comatic aberration to the axis 30. Consequently, in order to correct the comatic aberration occurring in the specific direction, the angle for tilting the objective lens 8 can be reduced compared with a conventional configuration. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical pickup device capable of recording information and reading information by irradiating an optical recording medium with a light beam, and more particularly to an electrical pickup device including an objective lens actuator having a function of tilting an objective lens. Related to reduction of load.

  In recent years, optical recording media such as compact discs (hereinafter referred to as CDs) and digital versatile discs (hereinafter referred to as DVDs) have become widespread and are generally used. In order to increase the amount of information in the optical recording medium, development relating to the high density of the optical recording medium has been actively performed. For example, the optical recording medium having a high density such as a Blu-ray disc (hereinafter referred to as BD). Has been put into practical use. When recording and reproducing these different optical recording media such as CD, DVD, and BD, the information recorded on the optical recording medium can be read or recorded by irradiating the optical recording medium with a light beam. An optical pickup device is used.

  For example, when reading information on different optical recording media using an optical pickup device, due to the difference in recording density, the wavelength of the light beam emitted from the light source of the optical pickup device or the information recording surface of the optical recording medium It is necessary to change the numerical aperture of the objective lens that collects the light beam. However, if a different apparatus must be used for each type of optical recording medium, there will be many inconveniences for the user, so that information recording is performed on a single optical recording medium such as a CD, DVD, or BD. Development of a device capable of reproduction has been actively conducted.

  Under such circumstances, the applicant of the present invention has a concept that the optical pickup apparatus that can record and read information on a plurality of optical recording media has a small number of parts and does not use expensive optical parts. Patent Document 1 proposes an optical pickup device that eliminates point aberration and coma aberration and can form a favorable spot of a light beam. Hereinafter, the optical pickup device will be described with reference to FIG. FIG. 7 is a perspective view showing a configuration of a conventional optical pickup device.

  In FIG. 7, reference numeral 100 denotes an optical pickup device, and the optical pickup device 100 includes light sources 1 and 2 that emit light beams having different wavelengths. Laser diodes are used for the light sources 1 and 2. The light source 1 emits a 790 nm light beam for CD, for example, and the light source 2 emits a 660 nm light beam for DVD, for example.

  The light beam emitted from the light source 1 passes through the parallel flat plate half mirror 3 and the parallel flat plate half mirror 4 while being refracted, and is reflected by the total reflection mirror 5 toward the information recording surface of the optical recording medium 10 to be collimator. The light is converted into parallel light by the lens 6, is polarized from elliptically polarized light to linearly polarized light by the quarter wavelength plate 7, and is at a depth of 1.2 mm from the information recording surface of the CD type optical disk 10 by the objective lens 8, that is, the inner surface of the CD. Focused on the recording surface.

  Then, the reflected light reflected by the information recording surface of the CD returns in the reverse direction to the optical system of the objective lens 8, the quarter wavelength plate 7, the collimator lens 6, the total reflection mirror 5, and the parallel plate half mirror 4, The light is reflected by the parallel plate half mirror 3 and guided to the light detection element 9. The photodetecting element 9 converts the received optical information into an electrical signal and outputs it to, for example, an RF amplifier (not shown). This electric signal is used as a reproduction signal of data recorded on the information recording surface of the CD, and further as a servo signal for performing focus control and tracking control.

  On the other hand, the light beam emitted from the light source 2 is reflected by the parallel plate half mirror 4 so as to coincide with the optical axis of the light beam emitted from the light source 1. The light beam reflected by the parallel flat plate half mirror 4 is reflected by the total reflection mirror 5 toward the information recording surface of the optical recording medium 10, converted into parallel light by the collimator lens 6, and elliptical by the quarter wavelength plate 7. The light is polarized from the polarized light to the linearly polarized light, and is condensed by the objective lens 8 onto the information recording surface of the DVD as the optical disk 10, that is, the recording surface at a depth of 0.6 mm on the inner surface of the DVD.

  The reflected light reflected from the information recording surface of the DVD returns to the reverse direction through the optical system of the objective lens 8, quarter-wave plate 7, collimator lens 6, total reflection mirror 5, and the parallel plate half mirror 4. Then, the light is reflected by the parallel plate half mirror 3 and guided to the light detection element 9. After being guided to the light detecting element 9, the information is converted into an electric signal and used as a reproduction signal of data recorded on the information recording surface of the DVD, as in the case of CD.

  In the optical pickup device 100, each of the parallel plate half mirrors 3 and 4 is made of an optical glass material BK7 (borosilicate crown glass), and the thicknesses (t1 and t2 respectively) are both predetermined thicknesses (for example, t1 = t2 = 2.5 mm). The parallel flat plate half mirror 3 has a predetermined angle φ1 (for example, φ1 = 43.6 °) around the x-axis orthogonal to the optical axis of the light beam emitted from the light source 1 (z-axis in FIG. 7). Rotated and arranged. Further, the parallel flat plate half mirror 4 is rotated by a predetermined angle φ2 (for example, φ2 = 45 °) around the y-axis orthogonal to the z-axis that is the optical axis of the light beam emitted from the light source 1. Is arranged at a predetermined distance d (for example, 8 mm) away from the parallel flat plate half mirror 3 on the optical axis of the light beam emitted from.

  As described above, by configuring the parallel flat plate half mirrors 3 and 4, astigmatism generated when the light beam emitted from the light source 1 passes through the parallel flat plate half mirrors 3 and 4 can be canceled. Further, it is possible to adjust the direction of occurrence of coma generated by transmitting through the parallel flat plate half mirrors 3 and 4 in the radial direction (specific direction) of the optical disc 10. For this reason, in the optical pickup device 100, the objective lens 8 provided in the optical pickup device 100 is replaced by an actuator (not shown) with a lens tilt function in order to correct coma aberration generated in the radial direction of the optical disc 10. The coma aberration is corrected by tilting in the radial direction.

  Since the light beam emitted from the light source 2 does not pass through the parallel plate half mirror 4, astigmatism and coma derived from this optical system do not occur. Therefore, in the optical pickup device 100, when the objective lens 8 is arranged so that the optical axis of the objective lens 8 is orthogonal to the disc surface of the optical disc 10 and CD information is read, the coma aberration is canceled out. When the objective lens 8 is tilted by an actuator by a predetermined angle and DVD information is read, the objective lens 8 is used without being tilted.

  As described above, the optical pickup apparatus 100 proposed by the present applicant in Patent Document 1 has a small number of parts, does not use expensive optical parts, eliminates astigmatism and coma, and provides a good light beam spot. The optical pickup device can be formed. However, in the optical pickup device 100 having the configuration of Patent Document 1, for example, it is necessary to considerably increase the inclination of the objective lens that is inclined by the actuator when reading CD information or the like. The problem is that it is considerably large and power consumption increases. Then, with the configuration of Patent Document 1, it is considered that the electrical burden on the actuator is further increased when it is considered to be compatible with an optical recording medium such as a BD.

In addition, in terms of contrivance in the arrangement of the actuator of the objective lens, in Patent Document 2, the tilt of the objective lens with respect to the reference optical disc is determined for an optical pickup device including an objective lens that can handle a plurality of types of optical recording media. An optical pickup device configured to tilt the objective lens integrally with the actuator so that the angle becomes the optimum angle, and tilt the objective lens with respect to other types of optical discs using the tilt function of the actuator to the optimum angle with respect to the optical disc Has been introduced. However, in this case as well, as described above, since the arrangement angle of the actuator including the objective lens is determined based on one type of optical recording medium, information other than the reference optical recording medium is read. In addition, there is a problem that an electrical load on the actuator is large.
JP 2005-228365 A JP 2002-373445 A

  In view of the above points, the present invention enables recording and reproduction of a plurality of types of optical recording media, and is configured to generate coma aberration in a specific direction when performing recording and reproduction of at least one of them. An object of the present invention is to provide an optical pickup device that can reduce the electrical load applied to the actuator in an optical pickup device that corrects the coma aberration using an actuator having a tilt function.

To achieve the above object, the present invention provides an infrared light source for CD and a red light source for DVD arranged at a first position, a blue light source for BD arranged at a second position, and the red light source. On the optical axis of the first light flux emitted from the outside or the red light source, the first light flux is arranged by being rotated by a predetermined angle around a first axis orthogonal to the optical axis of the first light flux. A first half mirror that refracts and transmits and reflects reflected light reflected by the optical recording medium to guide light detection means for detecting optical information contained in the reflected light; and On the optical axis, the first light beam that is rotated by a predetermined angle about a second axis that is orthogonal to the optical axis of the first light flux and the first axis, and that has passed through the first half mirror. Second light emitted from the blue light source while being refracted and transmitted through A second half mirror that reflects the light beam and coincides with the optical axis of the first light beam, and an objective lens that focuses the light beam from the second half mirror on the recording surface of the optical recording medium. An objective lens actuator having a tilt function that allows the lens to move in a focus direction and a radial direction of the optical recording medium, and tilts the objective lens in the radial direction, and the first light flux In the optical pickup device, coma aberration is generated in the radial direction by passing through the first and second half mirrors, and the coma aberration is corrected by tilting the objective lens by the tilt function. The optical axis of the objective lens is set to the coma with respect to the third axis orthogonal to the recording surface due to the inclination of the objective lens actuator In order to correct the difference, the objective lens is arranged so as to be inclined by an inclination angle θs in a direction in which the objective lens is inclined, and cancels the coma aberration generated by light beams emitted from the infrared light source and the red light source Therefore, when the angles at which the objective lens is inclined with respect to the third axis are θ1 and θ2, respectively, the inclination angle θs satisfies the following expression (1).
θs = (θ1 + θ2) / 3 (1)

  In order to achieve the above object, the present invention has a plurality of light sources that have different wavelengths and are disposed at either the first position or the second position, and are disposed at the first position. It is arranged on the optical axis of the first light beam emitted from the light source, rotated by a predetermined angle about the first axis orthogonal to the optical axis of the first light beam, and refracts the first light beam. A first light separation element that reflects the reflected light reflected by the optical recording medium and guides it to a light detection means that detects optical information of the reflected light, and the light of the first light flux On the axis, the first light beam that is rotated by a predetermined angle about a second axis that is orthogonal to the optical axis of the first light flux and the first axis, and that has passed through the first light separation element. The light beam is refracted and transmitted and emitted from the light source disposed at the second position. A second light separation element that reflects the second light flux to coincide with the optical axis of the first light flux, and an objective that focuses the light flux from the second light separation element on the recording surface of the optical recording medium. And a plurality of objective lens actuators having a tilt function that allows the objective lens to move in a focus direction and a radial direction of the optical recording medium, and tilts the objective lens in a predetermined direction. At least one of the light sources is disposed at each of the first and second positions, and the first light flux passes through the first and second light separation elements to cause coma aberration in the predetermined direction. In the optical pickup device in which the coma aberration is corrected by tilting the objective lens by the tilt function, the objective lens is moved to cancel the coma aberration. The objective lens corrects the coma aberration with respect to the third axis when the maximum angle among the angles inclined with respect to the third axis orthogonal to the recording surface is θmax. In order to perform this, the objective lens is arranged to be inclined at a predetermined angle between zero and θmax in a direction in which the objective lens is inclined.

  According to the present invention, in the optical pickup device having the above-described configuration, the objective lens actuator is tilted, and the objective lens is tilted by the predetermined angle.

  According to the present invention, in the optical pickup device configured as described above, the predetermined direction is the radial direction.

According to the present invention, in the optical pickup device having the above-described configuration, in order to cancel the coma aberration generated by the light beam emitted from the i-th light source among the n light sources arranged at the first position, When θi is an angle at which the objective lens needs to be tilted with respect to the third axis, and θs is the predetermined angle at which the objective lens is tilted, θs is expressed by the following formula 1. It is said.

  According to the first configuration of the present invention, the light source for CD, DVD, and BD is provided, and the light beam emitted from the light source for CD and DVD passes through the half mirror so that the radial direction of the optical recording medium is obtained. In an optical pickup device that corrects the coma generated in the lens using an objective lens actuator with a tilt function, the conventional objective lens is tilted to correct the above-mentioned coma aberration by tilting the objective lens actuator itself. The objective lens is tilted in advance by a predetermined amount in the direction it was in. For this reason, compared with the prior art, the angle at which the objective lens is tilted by the objective lens actuator can be reduced in order to correct the coma aberration caused by the light flux from the light sources for CD and DVD. On the other hand, by tilting the objective lens in advance, coma aberration also occurs in the light beam from the light source for BD, which conventionally does not generate coma because it does not pass through the half mirror, and correction thereof is necessary. Therefore, the objective lens may be tilted by an angle smaller than the angle at which the objective lens has been tilted most conventionally. That is, the optical pickup device of the present invention can be configured not to apply an excessive electrical load to the objective lens actuator.

  In addition, the angle at which the objective lens is tilted by tilting the objective lens actuator is determined with an emphasis on balance based on the amount of coma generated by each of the light beams emitted from the light sources for CD, DVD, and BD. In addition, even when recording or reproducing any type of optical recording medium, the objective lens actuator can be configured not to be excessively burdened when the objective lens is tilted. In addition, when the user uses CDs, DVDs, and BDs almost evenly, the total power consumption of the objective lens actuator can be reduced.

  Further, according to the second configuration of the present invention, it is possible to perform recording / reproduction of a plurality of types of optical recording media, and to perform coma aberration in a specific direction when performing recording / reproduction of at least one of them. In the optical pickup device that corrects the coma aberration using an actuator with a tilt function, the maximum angle at which the objective lens is conventionally tilted in the direction in which the objective lens corrects the coma aberration generated in a specific direction. Therefore, the angle at which the objective lens is tilted by using the objective lens actuator when correcting coma generated in a specific direction can be reduced as compared with the conventional art. On the other hand, by tilting the objective lens in advance, coma aberration occurs even for the light beam from the light source that has not generated coma aberration because it does not pass through the light separation element. The objective lens may be tilted by an angle smaller than the angle at which the objective lens is tilted most. In other words, the optical pickup device of the present invention can be configured not to apply an excessive load electrically to the objective lens actuator.

  Further, according to the third configuration of the present invention, in the optical pickup device having the second configuration described above, a configuration in which the objective lens is tilted by a predetermined angle in a predetermined direction can be easily realized.

  According to the fourth configuration of the present invention, in the optical pickup device having the second or third configuration, the configuration in which the objective lens is tilted in a predetermined direction by the objective lens actuator can be easily achieved. The configuration can be easily realized.

  According to the fifth configuration of the present invention, in the optical pickup device having any one of the second to fourth configurations, the angle at which the objective lens is tilted is the amount of coma generated by the light beam emitted from each light source. Therefore, when the objective lens is tilted, the objective lens actuator is not subjected to an excessive burden even when recording or reproducing any type of optical recording medium. it can. Further, when the user uses the optical recording medium corresponding to each light source almost evenly, the total power consumption of the objective lens actuator can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic perspective view showing the configuration of the optical system of the optical pickup device of this embodiment. In addition, the same code | symbol is attached | subjected about the part which overlaps with the conventional optical pick-up apparatus 100 shown in FIG. 7, and the description is abbreviate | omitted when there is no need in particular.

  Reference numeral 50 denotes an optical pickup device that reads information recorded on the recording surface of the optical disc 10 by irradiating the optical recording medium 10 such as a CD, DVD, and BD with a light beam and receiving reflected light. The optical disk 10 is an apparatus that can irradiate a light beam to write information on a recording surface. The configuration of the optical pickup device 50 is substantially the same as that of the conventional optical pickup device 100, and the configuration of the light sources 1 and 2, the point that the quarter wavelength plate 7 (see FIG. 7) is not provided, and the objective lens 8 are held. The arrangement of an objective lens actuator (not shown) with a tilt function is different.

  The quarter wavelength plate 7 may be arranged for the optical pickup device 50 of the present embodiment. In this case, for example, the quarter wavelength plate 7 is held by the objective lens actuator together with the objective lens 8. It doesn't matter.

  Reference numeral 1 denotes a two-wavelength integrated laser diode in which an infrared light source 1a for CD and a red light source 1b for DVD are integrated. The infrared light source 1a emits a light beam of 790 nm, for example, and the red light source 1b emits a light beam of 660 nm, for example. Reference numeral 2 denotes a blue light source, for example, a laser diode that emits a 405 nm light beam. The light source emitted from the light source passes through the parallel flat plate half mirrors 3 and 4, the infrared light source 1a and the red light source 1b are arranged at the first position 31, and the light beam emitted from the light source is a parallel flat plate half mirror. A position where the blue light source 2 that does not transmit through 3 and 4 and is reflected corresponds to the second position 32.

  As described above, since the objective lens actuator with a tilt function provided in the optical pickup device 50 is different from the conventional optical pickup device 100 in arrangement, this point will be described below. The configuration of the objective lens actuator 11 with a tilt function according to the embodiment will be described with reference to FIGS. Here, FIG. 2 is a schematic top view showing the configuration of the objective lens actuator 11 of the present embodiment, FIG. 3 is a schematic side view showing the configuration of the objective lens actuator 11 of the present embodiment, and FIG. It is AA and BB sectional drawing.

  The objective lens actuator 11 is largely composed of a metallic base member 12 having ferromagnetism and a lens holder 13 of a resin molded product. A through hole (not shown) through which the laser beams from the light sources 1a, 1b, and 2 (see FIG. 1) pass is formed at substantially the center of the base member 12, and a lens holder 13 to be described in detail later is disposed. On the base member 12, a pair of permanent magnets 14a and 14b that are opposed to each other at a predetermined interval so as to sandwich the lens holder 13 are provided upright. Each of the permanent magnets 14a and 14b is fixed in a state of being magnetically integrated with the base member 12 by magnetically attaching the outer surfaces of the permanent magnets 14a and 14b to the projecting pieces 12a and 12b formed by bending from the base member 12. Is done.

  Further, the base member 12 is provided with a pair of yokes 15a, 15b that are opposed to each other in a direction substantially perpendicular to the facing direction of the permanent magnets 14a, 14b between the permanent magnets 14a, 14b. Each of these yokes 15 a and 15 b is formed by bending from the base member 12. Here, each of the yokes 15a and 15b effectively draws magnetic flux from each of the permanent magnets 14a and 14b, and mainly includes a focusing coil 16, tracking coils 17a and 17b, which will be described later, and a tilting coil disposed between them. A high-density magnetic flux is applied to the coils 27a and 27b, thereby playing a role of increasing the lens holder 13 drive efficiency.

  The lens holder 13 is held on a lens mounting surface (not shown) formed at the center of the upper portion thereof so that the optical axis of the objective lens 8 is oriented in the vertical direction. The yokes 15a and 15b penetrate through the objective lens 8 on the left and right. A focusing coil 16 is provided inside the side wall of the lens holder 13 so as to surround the optical axis of the objective lens 8, and is fixed to the lens holder 13 with an adhesive or the like. Also, tracking coils 17a and 17b are fixed to the outside of the side walls of the lens holder 13 opposite to the permanent magnets 14a and 14b, respectively, with an adhesive or the like. Each of the tracking coils 17a and 17b is formed in a pair on the left and right so as to face the yokes 15a and 15b, respectively, and is connected by a single line as a whole. Further, under the focus coil 16, tilt coils 27a and 27b are fixed with an adhesive or the like so as to surround the yokes 15a and 15b. The tilt coils 27a and 27b are also connected by a single line as a whole.

  Further, on the base member 12, a gel holder 18 of a resin molded product such as polycarbonate is fixed to the outer surface side of the projecting piece 12b on which one permanent magnet 14b is magnetically attached, and further, adjacent to the outside of the gel holder 18. A circuit board 19 is erected. One end of each of the conductive wires 20a, 20b, 20c, 20d, 20e, and 20f is connected to the circuit board 19 by soldering at three positions in the vertical direction on both the left and right sides. Each of these six wires 20a, 20b, 20c, 20d, 20e, and 20f is formed on the gel holder 18 at three positions in the vertical direction on the left and right sides, that is, on the left and right sides. The through holes 21a, 21b, 21c, 21d, 21e, and 21f are inserted.

  Further, the wires 20a to 20f are joined to the protrusions 13a and 13b protruding from the left and right sides of the lens holder 13 with an adhesive or the like, whereby the lens holder 13 is attached to the base member 12 by the wires 20a to 20f. And is supported so that it can swing. The other ends of the upper wires 20a and 20d are connected to the focusing coil 16 by soldering, and the other ends of the middle wires 20b and 20e are connected to the tracking coils 17a and 17b by soldering. The other ends of the lower wires 20c and 20f are connected to the tilt coils 27a and 27b by soldering.

  Moreover, the gel material which has silicon as a main component is filled in each through-hole 21a-21f of the gel holder 18 by which each wire 20a-20f was penetrated. Here, the gel material is obtained by injecting a low-viscosity gel material (sol) into each of the through holes 21a to 21f of the gel holder 18 and then curing the gel material by ultraviolet irradiation for a predetermined time.

  In the objective lens actuator 11 configured as described above, when current is supplied from the circuit board 19 to the focusing coil 16, the tracking coils 17a and 17b, and the tilt coils 27a and 27b through the wires 20a to 20f, Electromagnetic action occurs between the coils 16, 17a, 17b, 27a, 27b and the permanent magnets 14a, 14b, and the lens holder 13 is driven. It should be noted that the vibration generated in each of the wires 20a to 20f in response to the driving of the lens holder 13 is attenuated and suppressed by the gel material in each of the through holes 21a to 21f in the gel holder 18.

  The driving of the lens holder 13 will be described in more detail. When a current is supplied to the focusing coil 16, the lens holder 13 is driven in the vertical direction in FIG. Allows focus adjustment. Further, when a current is supplied to the tracking coils 17a and 17b, the lens holder 13 is driven in the left-right direction in FIG. 2 (the paper surface direction in FIG. 3) to enable tracking adjustment. Note that the horizontal direction in FIG. 2 corresponds to the radial direction of the optical disc 10.

  Further, when a current in a certain direction is supplied to the coils 27a and 27b for tilting, in FIG. 2, for example, the right side of the lens holder 13 moves to the front side of the paper and the left side of the lens holder 13 moves to the back side of the paper. When 8 is tilted to the left and a current in the opposite direction is supplied, the objective lens 8 is tilted to the right. That is, the tilt coils 27a and 27b allow the objective lens 8 to be tilted in the radial direction of the optical disk 10 (the left-right direction in FIG. 2), and in the optical pickup device 50 as well as the conventional optical pickup device 100. Correction of coma generated in the radial direction of the optical disk 10 can be performed.

  Note that the configuration of the objective lens actuator with a tilt function of the present embodiment is an example, and the configuration of the objective lens actuator 11 is not limited to the configuration of the present embodiment.

  Next, how the objective lens actuator 11 configured as described above is arranged in the optical pickup device 50 will be described. FIG. 5 is a schematic diagram schematically showing a relationship between the objective lens actuator 11 and some other optical components in the optical pickup device 50 of the present embodiment. As shown in FIG. 5, the objective lens actuator 11 has the objective lens 8 with respect to the optical axis 30 of the light beam emitted from the light sources 1 a, 1 b, 2 (see FIG. 1) and reflected by the total reflection mirror 5. The optical axis 8a is disposed so as to be inclined by an inclination angle θs, for example, rightward in the drawing. The optical axis 30 is an axis orthogonal to the recording surface of the optical disc 10, and the horizontal direction in FIG. 5 corresponds to the radial direction.

  Hereinafter, the method of determining the tilt angle θs and the tilt direction will be described, but in order to make the description easy to understand, the description will be made in comparison with the arrangement of the objective lens actuator 11 in the conventional optical pickup device 100. FIG. 6 is an explanatory diagram for explaining a method of determining the tilt angle θs of the objective lens in the optical pickup device 50 of the present embodiment. FIG. 6A shows the state of the objective lens actuator 11 of the present embodiment. FIG. 6B is a diagram illustrating a state of the conventional objective lens actuator 11. Also in FIG. 6, the left-right direction corresponds to the radial direction of the optical disc 10.

  As shown in FIG. 6B, the conventional objective lens actuator 11 is not tilted with respect to the optical axis 30 (the optical axis 8a of the objective lens 8 coincides with the optical axis 30). . In this case, the light beams emitted from the infrared light source 1a (CD light source) and the red light source 1b (DVD light source) pass through the parallel plate half mirrors 3 and 4 in the radial direction of the optical disk 10. Since coma is generated, in order to correct this coma, for example, as shown in FIG. 6 (b), when recording / reproducing CD information, θ1 with respect to the optical axis 30 and DVD information When recording / reproducing is performed, it is necessary to tilt the objective lens 8 to the right in the figure by θ2 with respect to the optical axis 30.

  Note that θ1 and θ2 shown here are schematically shown and do not always satisfy θ1 <θ2, and the values of θ1 and θ2 vary depending on the optical design of the objective lens 8 or the like. In addition, the direction in which the objective lens 8 is tilted to correct coma aberration is set to the right direction. However, depending on the configuration of the optical pickup device 50, this is not the right direction but the left direction. However, the tilting direction is the same for CD and DVD.

  In the case of the conventional configuration, the angle at which the objective lens 8 is tilted (for example, θ2) becomes considerably large, so that an electrical load when the objective lens actuator 11 tilts the objective lens 8 becomes large. Therefore, as shown in FIG. 6A, the objective lens actuator 11 provided in the optical pickup device 50 of the present embodiment is generated when the optical axis 8a of the objective lens 8 records and reproduces information on CDs and DVDs. Is tilted so as to be tilted by a tilt angle θs in a direction for correcting coma aberration (rightward in FIG. 6), thereby reducing the angle at which the objective lens 8 is tilted by using the tilt function of the objective lens actuator 11 as compared with the prior art. The objective is to reduce the electrical load applied to the objective lens actuator 11.

  By the way, in the conventional configuration, since the light beam emitted from the blue light source 2 (light source for BD) reaches the optical disk 10 without passing through the parallel plate half mirrors 3 and 4, no coma aberration is generated. There is no need to tilt the objective lens 8 by the objective lens actuator 11. However, when the objective lens actuator 11 is tilted and the optical axis 8a of the objective lens 8 is tilted by θs with respect to the optical axis 30 as described above, the light beam emitted from the blue light source 2 is also coma. Since aberration occurs, it is necessary to tilt the objective lens 8 in the opposite direction by the amount (θs) where the objective lens 8 is tilted.

  Therefore, the angle θs at which the objective lens 8 is tilted by tilting the objective lens actuator 11 is the maximum angle θmax at which the objective lens 8 is tilted by the tilt function of the objective lens actuator 11 in the conventional configuration (θ2 in FIG. 6 is On the other hand, when the recording / reproducing of the BD is performed, the electrical load applied to the objective lens actuator 11 is increased, which is not preferable. Therefore, it is necessary that the angle θs for tilting the objective lens 11 by tilting the objective lens actuator 11 does not exceed θmax.

In the present embodiment, further, it is assumed that the CD, DVD, and BD optical discs 10 are equally used, and the electric power applied to the objective lens actuator 11 when recording / reproducing one of the optical discs 10 is performed. In order to prevent excessive load, and to minimize the total power consumption consumed by the objective lens actuator 11, the objective lens 8 is provided with various inclination angles [theta] s in advance so that the objective lens 8 is tilted in advance. The optical disk 10 is set to have an average value (see the following formula (1)) of angles (θ1, θ2, 0 in the order of CD, DVD, BD).
θs = (θ1 + θ2) / 3 (1)

  Note that the value of θs does not necessarily have to be an average value as described above, and may be in a range that does not exceed the above θmax, that is, an angle between 0 and θmax. Further, in the present embodiment, the configuration in which the objective lens 8 is tilted in advance with respect to the optical axis 30 (see FIG. 5) is achieved by tilting the objective lens actuator 11, but is not necessarily limited to this configuration. The present invention can be changed without departing from the scope of the present invention. That is, for example, the objective lens 8 may be arranged in a tilted state on the lens holder 13 (see FIG. 3) provided in the objective lens actuator 11.

Further, in the present embodiment, for the light source provided in the optical pickup device 50, the infrared light source 1a and the red light source 1b are disposed at the first position 31, and the blue light source 2 (both in FIG. 1). However, the present invention is not limited to this configuration, and an infrared light source may be disposed at the first position 31, and a red light source and a blue light source may be disposed at the second position. A plurality of light sources may be arranged for each of the first position 31 and the second position 32. When the arrangement is made as described above, the inclination angle θs for inclining the optical axis 8a of the objective lens 8 with respect to the optical axis 30 is set as an average value of the inclination angles in which the objective lens 8 is conventionally inclined. Is given by θs in Equation 1 below. In Equation 1, n is the number of light sources arranged at the first position 31, and θi is emitted from the light source for the i-th light source among n light sources arranged at the first position 31. This is an angle at which the optical axis 8 a of the objective lens 8 needs to be inclined with respect to the optical axis 30 in order to cancel the coma aberration that occurs.

  In addition, in this embodiment, the direction of coma generated by the light beam emitted from the light source disposed at the first position 31 of the optical pickup device 50 is adjusted so as to be the radial direction of the optical disc 10, and this direction Although the objective lens 8 and the objective lens actuator 11 are inclined, the direction in which the coma aberration occurs is not necessarily the radial direction, and can be changed as appropriate. Also, the configuration of the optical system of the optical pickup device can be modified or improved within the scope of ordinary knowledge possessed by those skilled in the art.

  The present invention enables recording / reproduction of a plurality of types of optical recording media, and is configured to generate coma aberration in a specific direction when recording / reproduction of at least one of them. The optical axis of the objective lens mounted on the objective lens actuator is a direction that cancels coma generated in a specific direction with respect to the axis perpendicular to the recording surface of the optical recording medium. Are inclined at a predetermined angle.

  For this reason, the angle at which the objective lens is tilted can be reduced by the tilt function of the objective lens actuator, and the electrical load applied to the objective lens actuator can be reduced as compared with the conventional art.

These are the schematic perspective views which show the structure of the optical system of the optical pick-up apparatus of this embodiment. These are the schematic top views which show the structure of the objective lens actuator with which the optical pick-up apparatus of this embodiment is provided. These are the schematic side views which show the structure of the objective lens actuator with which the optical pick-up apparatus of this embodiment is provided. These are AA and BB sectional drawing of FIG. These are the schematic diagrams which show typically the relationship between an objective-lens actuator and another one part optical component in the optical pick-up apparatus of this embodiment. These are explanatory drawings for explaining a method of determining the tilt angle θs of the objective lens in the optical pickup device of the present embodiment. These are the schematic perspective views which show the structure of the optical system of the conventional optical pick-up apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 2 wavelength integrated laser diode 1a Infrared light source 1b Red light source 2 Blue light source 3 Parallel plate half mirror (1st light separation element)
4 Parallel plate half mirror (second light separation element)
8 Objective lens 8a Optical axis of objective lens 10 Optical disc (optical recording medium)
11 Objective lens actuator 30 Optical axis (third axis)
31 First position 32 Second position

Claims (5)

An infrared light source for CD and a red light source for DVD disposed in the first position;
A blue light source for BD arranged at the second position;
On the optical axis of the first light beam emitted from the infrared or red light source, the first light beam is disposed at a predetermined angle around the first axis orthogonal to the optical axis of the first light beam, A first half mirror that refracts and transmits a light beam, reflects reflected light reflected by the optical recording medium, and guides the light to light detection means that detects optical information of the reflected light;
The first half mirror is disposed on the optical axis of the first light flux by being rotated by a predetermined angle about a second axis orthogonal to the optical axis of the first light flux and the first axis. A second half mirror that refracts and transmits the first light flux that has passed through the second light source and reflects the second light flux emitted from the blue light source to coincide with the optical axis of the first light flux;
An objective lens for condensing the light beam from the second half mirror on the recording surface of the optical recording medium is mounted, the objective lens can be moved in a focus direction and a radial direction of the optical recording medium, and the objective An objective lens actuator having a tilt function for tilting the lens in the radial direction,
The first light flux passes through the first and second half mirrors to generate coma aberration in the radial direction, and the coma aberration is corrected by tilting the objective lens by the tilt function. In the optical pickup device,
The objective lens is tilted by the tilt of the objective lens actuator so that the optical axis of the objective lens corrects the coma aberration with respect to a third axis orthogonal to the recording surface. It is arranged to incline in the direction by an inclination angle θs,
When the angles of inclination of the objective lens with respect to the third axis are set to θ1 and θ2, respectively, in order to cancel the coma aberration generated by the light beams emitted from each of the infrared light source and the red light source, The inclination angle θs satisfies the following expression (1).
θs = (θ1 + θ2) / 3 (1) A plurality of light sources having different wavelengths and disposed at either the first position or the second position;
Arranged on the optical axis of the first light beam emitted from the light source disposed at the first position, rotated by a predetermined angle around the first axis orthogonal to the optical axis of the first light beam. The first light separation element that refracts and transmits the first light flux and reflects the reflected light reflected by the optical recording medium to lead to light detection means for detecting optical information of the reflected light. When,
The first light separation is arranged on the optical axis of the first light flux by being rotated by a predetermined angle about a second axis orthogonal to the optical axis of the first light flux and the first axis. The first light beam transmitted through the element is refracted and transmitted, and the second light beam emitted from the light source disposed at the second position is reflected to coincide with the optical axis of the first light beam. A second light separation element to be
An objective lens for condensing the light beam from the second light separation element on the recording surface of the optical recording medium is mounted, the objective lens can be moved in a focus direction and a radial direction of the optical recording medium, and An objective lens actuator having a tilt function for tilting the objective lens in a predetermined direction,
At least one of the plurality of light sources is disposed in each of the first and second positions,
The first light flux passes through the first and second light separation elements to generate coma aberration in the predetermined direction, and the coma aberration is corrected by tilting the objective lens by the tilt function. In the optical pickup device
In order to cancel the coma aberration, when the maximum angle among the angles for tilting the objective lens with respect to the third axis orthogonal to the recording surface is θmax,
The objective lens is disposed such that its optical axis is inclined at a predetermined angle between zero and θmax in a direction in which the objective lens is inclined with respect to the third axis in order to correct the coma aberration. An optical pickup device.   The optical pickup device according to claim 2, wherein the objective lens actuator is tilted and the objective lens is tilted by the predetermined angle.   The optical pickup device according to claim 2, wherein the predetermined direction is the radial direction. Of the n light sources arranged at the first position, it is necessary to incline the objective lens with respect to the third axis in order to cancel the coma aberration generated by the light beam emitted from the i-th light source. 5. The θ is expressed by the following Equation 1, where θ i is a certain angle and θs is the predetermined angle for tilting the objective lens. 2. An optical pickup device according to item 1.

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