JP2008108378A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device precisely and stably determining a target objective lens set in an optical path by lens switching, without newly installing a detector. <P>SOLUTION: A ratio of an amplitude value of an S-shaped signal obtained by receiving a red laser beam B2 by a photodetector 9 while an aberration correction element 5 is set at an optimum value for correcting spherical aberration of a blue laser beam B1 to an amplitude value of an S-shaped signal obtained by receiving the red laser beam B2 by the photodetector 9 while the aberration correction element 5 is set at an optimum value for correcting spherical aberration of the red laser beam B2 is compared with a prescribed threshold. Thus, it is determined whether the objective lens La or Lb is disposed in the composed optical path. The lens is switched by an actuator 8 until the determination result agrees with the target objective lens. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus, and corresponds to a plurality of optical discs such as a CD (compact disc), a DVD (digital versatile disc), and a BD (Blu-ray Disc: a high density optical disc using a blue laser beam). The present invention relates to an optical disk device.

  For example, in an optical pickup that switches between a high NA (numerical aperture) blue objective lens used in BD and a red / infrared objective lens used in two wavelengths of DVD / CD, the objective used is If the lens is not set at a predetermined position in the optical path, proper recording and reproduction cannot be performed. In addition, if the blue laser beam for BD is incident on the red / infrared objective lens, the objective lens may be deteriorated. Therefore, it is necessary to determine whether the objective lens set in the optical path is the target objective lens in order to prevent an objective lens switching error.

In order to solve the above problems, various types of optical disc apparatuses and lens position detection methods have been proposed. For example, Patent Documents 1 to 4 propose an optical pickup and an optical disk device that detect a lens position using a detection device. Further, Patent Document 5 proposes an optical disk device that detects a lens position using a signal obtained from an optical disk.
JP 10-198969 A JP-A-9-305980 JP-A-10-326423 JP-A-9-180218 JP 2003-99958 A

  However, in the optical disk devices and the like described in Patent Documents 1 to 4, it is necessary to newly provide a detection device, resulting in an increase in cost, an increase in weight, an increase in size, and the like. In the optical disk device described in Patent Document 5, misclassification may occur due to variations in disk reflectivity.

  The present invention has been made in view of such a situation, and an object of the present invention is to determine whether the objective lens set in the optical path by switching the lens is a target objective lens without newly providing a detection device. It is an object of the present invention to provide an optical disc apparatus capable of stably discriminating the above with high accuracy.

  To achieve the above object, an optical disc apparatus according to a first aspect of the invention emits a first laser light source that emits a blue laser beam, a second laser light source that emits a red laser beam, and an infrared laser beam. A third laser light source; an optical path combining element that combines the optical paths of the blue, red, and infrared laser beams; and an aberration correction element that is disposed in the combined optical path and corrects the spherical aberration of at least one laser beam. A first objective lens that is arranged in the combined optical path and forms an image of the blue laser beam on the corresponding optical disk, and a red and infrared laser beam that are arranged in the combined optical path, respectively. And a second objective lens that forms an image on the optical disc corresponding to the optical disc, and a first objective lens and a second objective lens that are positioned at predetermined positions in the combined optical path. Actuators that switch the laser beam, a photodetector that receives the laser beam reflected from the optical disk and detects optical information, and an optical path that branches the optical path from each laser light source to the optical disk and the optical path from the optical disk to the optical detector An optical disk device having a branching element in an optical pickup, wherein the optical detector receives the red laser beam with the aberration correcting element set to an optimum value for correcting the spherical aberration of the blue laser beam. By obtaining the red laser beam with the photodetector in a state in which the amplitude value of the S-shaped signal obtained by this is set and the aberration correction element is set to the optimum value for correcting the spherical aberration of the red laser beam. By comparing the ratio of the amplitude value of the S-shaped signal with a predetermined threshold value, the objective lens disposed in the combined optical path can be compared with the first and second pairs. Determine which one of the lenses, determination result and performs the lens switching in the actuator until it matches the purpose of the objective lens.

  An optical disc apparatus according to a second aspect of the invention includes a first laser light source that emits a first laser beam having a short wavelength, a second laser light source that emits a second laser beam having a long wavelength, and first and second laser light sources. An optical path combining element that combines the optical paths of the laser beams, an aberration correction element that is disposed in the combined optical path and corrects the spherical aberration of at least one laser beam, and is disposed in the combined optical path. A first objective lens that forms an image on the optical disk corresponding to the laser beam and a second objective lens that is arranged in the combined optical path and forms an image on the optical disk corresponding to the second laser beam An actuator for switching lenses so that one of the first and second objective lenses is positioned at a predetermined position in the combined optical path, and a laser beam reflected by the optical disk An optical disc apparatus provided with an optical pickup that includes a photodetector that receives light to detect optical information and an optical path branching element that branches an optical path from each laser light source to the optical disc and an optical path from the optical disc to the optical detector. The amplitude value of the S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to an optimum value for correcting the spherical aberration of the first laser beam. And an amplitude value of an S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to an optimum value for correcting the spherical aberration of the second laser beam. To determine whether the objective lens arranged in the combined optical path is the first objective lens or the second objective lens.

  An optical disk apparatus according to a third invention is characterized in that, in the second invention, the first laser beam is a blue laser beam, and the second laser beam is a red laser beam.

  An optical disc apparatus according to a fourth aspect of the invention is a first laser light source that emits a first laser beam with a short wavelength, a second laser light source that emits a second laser beam with a long wavelength, and a second laser beam. A third laser light source that emits a third laser beam having a longer wavelength, an optical path combining element that combines the optical paths of the first to third laser beams, and at least one element disposed in the combined optical path An aberration correction element that corrects the spherical aberration of the laser beam, a first objective lens that is arranged in the combined optical path and forms an image of the first laser beam on the corresponding optical disk, and in the combined optical path A second objective lens that forms an image of the second and third laser beams on the corresponding optical discs, and a first objective lens and a second objective lens at a predetermined position in the combined optical path. Any of An actuator that switches the lens so that one is positioned, a photodetector that receives the laser beam reflected by the optical disc and detects optical information, an optical path from each laser light source to the optical disc, and an optical path from the optical disc to the photodetector And an optical path device having an optical path branching element for branching with the optical pickup, wherein the aberration correction element is set to an optimum value for correcting the spherical aberration of the first laser beam, and the second is set. The amplitude value of the S-shaped signal obtained by receiving the laser beam with the photodetector and the aberration correction element set to the optimum value for correcting the spherical aberration of the second laser beam are set in the second state. An objective lens disposed in the synthesized optical path by comparing the amplitude value of the S-shaped signal obtained by receiving the laser beam with the photodetector. First, and discriminates which one of the second objective lens.

  An optical disk apparatus according to a fifth aspect of the present invention is the optical disc apparatus according to the fourth aspect, wherein the first laser beam is a blue laser beam, the second laser beam is a red laser beam, and the third laser beam is red. It is an outside laser beam.

  An optical disc device according to a sixth aspect of the present invention is the optical disc apparatus according to any one of the second to fifth aspects, wherein the aberration correction element is set to an optimum value for correcting the spherical aberration of the first laser beam. In the state in which the amplitude value of the S-shaped signal obtained by receiving the laser beam by the photodetector and the aberration correction element are set to the optimum values for correcting the spherical aberration of the second laser beam. The amplitude value of the S-shaped signal is compared by comparing a ratio of the amplitude of the S-shaped signal obtained by receiving the laser beam with the S detector with a predetermined threshold value. To do.

  According to the present invention, the S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to the optimum value for correcting the spherical aberration of the first laser beam. The amplitude value and the amplitude value of the S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to the optimum value for correcting the spherical aberration of the second laser beam. Are compared with each other to determine whether the objective lens arranged in the combined optical path is the first objective lens or the second objective lens. Therefore, it is possible to stably determine with high accuracy whether the objective lens set in the optical path by switching the lens is the target objective lens. Since the influence of spherical aberration that depends on the NA of the objective lens is used, erroneous discrimination due to variations in disk reflectivity can be eliminated. As a result, stable discrimination with high accuracy is possible, and switching errors of the objective lens are prevented. be able to. By comparing the amplitude value ratio of the S-shaped signal with a predetermined threshold value, if the amplitude value of the S-shaped signal is compared, the accuracy is further improved and a reliable determination is possible. Further, by using a long-wavelength second laser beam (for example, a red laser beam) that does not cause deterioration of the objective lens, it is possible to prevent the objective lens from being deteriorated.

  Embodiments of an optical disk device according to the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a schematic configuration of an embodiment of an optical disk device. The optical disc apparatus 20 is composed of an optical pickup 10 corresponding to three types of optical discs 11 having different use wavelengths, a control unit 12 for controlling the optical pickup 10, and the like, and recording information on all of the three types of optical discs 11.・ It is configured to allow playback.

  The three types of optical disks 11 assumed here are, for example, a first optical disk compatible with a blue laser (wavelength 405 nm) (a high-density optical disk using a blue laser beam; substrate thickness 0.1 mm, NA = 0.85). Second optical disc (DVD; substrate thickness: 0.6 mm, NA = 0.6 to 0.65) for red laser (wavelength 650 nm) Third optical disc (CD: substrate for infrared laser (wavelength 780 nm)) The thickness is 1.2 mm, NA = 0.45 to 0.5). However, the wavelength used is not limited to these. Further, the application target is not limited to the optical disc, and the present invention can be applied to optical information recording media other than the optical disc.

  In the optical pickup 10 shown in FIG. 1, 1a is a two-wavelength semiconductor laser for red / infrared, 1b is a semiconductor laser for blue, 2 is a dichroic prism, 3 is a polarization beam splitter, 4 is a collimating lens, and 5 is an aberration correction element. , 6 is a raising mirror, 7 is a quarter wave plate, 8 is an actuator, La is a red / infrared objective lens, Lb is a blue objective lens, and 9 is a photodetector. The optical configuration of the optical pickup 10 will be described below along the optical path.

  The optical pickup 10 has three laser light sources having different oscillation wavelengths. That is, the laser light source has two light sources mounted on the red / infrared two-wavelength semiconductor laser 1a and one light source mounted on the blue semiconductor laser 1b. When any one of the three laser light sources is turned on, optical information is recorded or reproduced on the corresponding optical disc 11. Laser beams B1, B2 or B3 emitted from the semiconductor lasers 1a and 1b enter the dichroic prism 2. The dichroic prism 2 is an optical path combining element that combines the optical paths of the blue, red, and infrared laser beams B1 to B3. Therefore, the blue laser beam B1 emitted from the semiconductor laser 1b is transmitted through the dichroic prism 2, and the red laser beam B2 or the infrared laser beam B3 emitted from the semiconductor laser 1a is reflected by the dichroic prism 2.

  The laser beam B 1, B 2, or B 3 emitted from the dichroic prism 2 enters the polarization beam splitter 3. The polarization beam splitter 3 is an optical path branching element that branches an optical path from each of the semiconductor lasers 1a and 1b to the optical disk 11 and an optical path from the optical disk 11 to the photodetector 9, and the laser beam B1, B2, or B3 is transmitted in the forward path. It arrange | positions so that the polarizing beam splitter 3 may permeate | transmit. The laser beam B 1, B 2, or B 3 that has passed through the polarization beam splitter 3 is converted into parallel light by the collimating lens 4 and then enters the aberration correction element 5.

  The aberration correction element 5 is an optical element that is arranged in the combined optical path and corrects the spherical aberration of at least one laser beam B1, B2, B3. Here, an expander lens is assumed as the aberration correction element 5. In general, in order to reduce the wavelength of the used light and increase the NA of the objective lens in order to cope with the higher density of the optical disc, the generation of spherical aberration due to the variation in the thickness of the transmission layer of the optical disc becomes a problem. For example, when the blue laser beam B1 is used, since the NA of the corresponding objective lens Lb is larger than the others, the generation of spherical aberration due to the error of the disk substrate becomes a problem. In order to correct this spherical aberration, the degree of collimation of the blue laser beam B1 incident on the objective lens Lb may be changed. Here, the air gap between the negative lens group and the positive lens group constituting the expander lens as the aberration correction element 5 (for example, the air gap between one negative lens and one positive lens) is changed. Therefore, the spherical aberration is corrected. The aberration correction is performed by setting an initial air interval corresponding to the set optical disk 11.

  The spherical aberration can also be corrected by disposing a liquid crystal correcting element in the optical path as the aberration correcting element 5 for correcting the spherical aberration. In the liquid crystal correction element, the light incident range is divided into a plurality of substantially circular electrode patterns centered on the optical axis of the objective lens. When the refractive index of the liquid crystal on each electrode pattern is changed by applying a voltage to the liquid crystal correction element, the phase of the transmitted light changes for each region. The spherical aberration can be corrected by adjusting the phase change. In this case, aberration correction is performed by setting the voltage to an initial value corresponding to the set optical disk 11.

  The laser beam B1, B2, or B3 emitted from the aberration correction element 5 is reflected by the rising mirror 6, passes through the quarter-wave plate 7, and is placed at a predetermined position in the optical path. The light is condensed by Lb and reaches the recording surface of the optical disk 11 to form an image. At this time, the blue objective lens Lb forms an image of the blue laser beam B1 on the corresponding optical disk 11, and the red / infrared objective lens La receives the red laser beam B2 or the infrared laser beam B3, respectively. The image is formed on the optical disk 11 corresponding to.

  The laser beam B1, B2 or B3 reflected by the recording surface of the optical disk 11 during information reproduction passes through the objective lens La or Lb and the quarter wavelength plate 7 in order, and is reflected by the rising mirror 6. Then, the light passes through the aberration correction element 5 and the collimating lens 4 in order, is reflected by the polarization beam splitter 3, and then reaches the light receiving surface of the photodetector 9 to form an image. The photodetector 9 detects the optical information of the received laser beam B1, B2 or B3 and outputs it as an electrical signal.

  The optical pickup 10 shown in FIG. 1 includes an actuator 8 for moving the objective lenses La and Lb during focusing, tracking, and the like. FIG. 2 shows a schematic configuration of the actuator 8. The actuator 8 has a function of performing lens switching so that one of the two objective lenses La and Lb is located at a predetermined position in the combined optical path. As shown in FIG. 2, tracking coils 17 are attached to the lens holder 15 at two locations, and the shaft 14 on the base 13 is centered by a combination with four magnets 16 arranged around the lens holder 15. The lens holder 15 is rotated. By rotating the lens holder 15, it is possible to perform switching so that one of the two objective lenses La and Lb is inserted into the optical path and the other is retracted outside the optical path.

  Of the two objective lenses La and Lb, if the objective lens corresponding to the optical disk 11 is not set at a predetermined position in the optical path, proper recording and reproduction cannot be performed. Therefore, in order to prevent switching errors between the objective lenses La and Lb, it is necessary to determine whether or not the objective lens set in the optical path is a target objective lens. In order to perform the determination and perform the lens switching with certainty, the control unit 12 (FIG. 1) performs the control described below in the optical disc apparatus 20.

  FIG. 3 shows control of switching of the objective lenses La and Lb and their confirmation by the control unit 12. When the optical disk 11 is set on the optical disk device 20, the target objective lens to be set in the optical path is determined. Then, the control part 12 starts the control operation shown in the flowchart of FIG. When the flow shown in FIG. 3 is entered, first, a switching operation to the target objective lens is performed (# 10). In this switching operation, if the rotational momentum of the lens holder 15 is too strong, the switching error occurs. If a switching error occurs, the process returns to the switching operation of step # 10 from the determination of step # 28 described later.

  Next, the red laser beam B2 is emitted from the semiconductor laser 1a (FIG. 1) (# 12). Then, the aberration correction element 5 is set to an optimum value for correcting the spherical aberration of the red laser beam B2 (that is, the optimum value of the red laser) (# 14), and the red laser beam B2 is detected by the photodetector 9 in the set state. By receiving the light, the amplitude value of the S-shaped signal (that is, the S-shaped amplitude value) S1 is measured (# 16). The S-shaped signal can be obtained by a focusing operation in which the objective lenses La and Lb in the optical path are moved up and down by the actuator 8. When the first acquisition of the S-shaped amplitude value S1 (# 16) is completed, the aberration correction element 5 is set to the optimum value for correcting the spherical aberration of the blue laser beam B1 (that is, the blue laser optimum value) (# 18). In this setting state, the red laser beam B2 is received by the photodetector 9, thereby measuring the amplitude value (that is, the S-shaped amplitude value) S2 of the S-shaped signal (# 20). When the second acquisition of the S-shaped amplitude value S2 (# 20) is completed, the process proceeds to step # 22.

  If the combination of the objective lenses La and Lb arranged in the optical path and the setting state of the aberration correction element 5 is different, the steps # 16 and # 20 are performed regardless of the type of the optical disk 11 set in the optical disk device 20. The obtained S-shaped amplitude values S1 and S2 are also different. FIG. 4 shows the S-shaped signal obtained by each combination and its amplitude values S1 and S2. As can be seen from FIG. 4, when the objective lens La for red / infrared is selected as the objective lens arranged in the optical path, when the setting of the aberration correction element 5 is the optimum value of the red laser, a certain size is obtained. S-shaped amplitude S1 (upper left column) can be obtained, but when the aberration correction element 5 is set to the blue laser optimum value, the obtained S-shaped amplitude value S2 (upper right column) is small. When the blue objective lens Lb is selected as the objective lens arranged in the optical path, the above is reversed. That is, when the setting of the aberration correction element 5 is the blue laser optimum value, a certain amount of S-shaped amplitude S2 (lower right column) can be obtained, but when the setting of the aberration correction element 5 is the red laser optimum value. The obtained S-shaped amplitude value S1 (lower left column) is small.

  As described above, by using the fact that the S-shaped amplitude values S1 and S2 are different depending on the combination of the objective lenses La and Lb arranged in the optical path and the setting state of the aberration correcting element 5, the S-shaped amplitude value obtained can be obtained. It is possible to determine the objective lenses La and Lb arranged in the optical path from S1 and S2. From this point of view, in step # 22, a predetermined threshold is provided for the S-shaped amplitude value ratio S1 / S2, and it is determined whether or not the S-shaped amplitude ratio S1 / S2 is larger than the threshold. In this determination, if the S-shaped amplitude ratio S1 / S2 is larger than the threshold value, the objective lens arranged in the optical path is determined as the red / infrared objective lens La (# 24), and the S-shaped amplitude ratio S1. When / S2 is not larger than the threshold value, the objective lens arranged in the optical path is determined as the blue objective lens Lb (# 26). After the discrimination of steps # 24 and # 26, it is judged whether or not the discrimination result matches the target objective lens (# 28). If they match, it means that there is no switching error between the objective lenses La and Lb, and the control operation is terminated. If they do not match, the process returns to step # 10, and the lens switching operation is continued by the actuator 8 until the discrimination result matches the target objective lens La or Lb (# 10 to # 28). Thereby, the switching mistake of the objective lenses La and Lb can be prevented.

  As in the optical disk device 20 described above, the red light beam B2 is received by the photodetector 9 with the aberration correction element 5 set to the optimum value for correcting the spherical aberration of the blue laser beam B1. Obtained by receiving the red laser beam B2 with the photodetector 7 in a state where the amplitude value S2 of the S-shaped signal and the aberration correction element 5 are set to the optimum values for correcting the spherical aberration of the red laser beam B2. A configuration for discriminating whether the objective lens arranged in the combined optical path is an objective lens for blue or red / infrared by comparing the amplitude value S1 of the S-shaped signal Thus, it is possible to accurately determine whether the objective lenses La and Lb set in the optical path by switching the lens are target objective lenses without providing a new detection device. Can to determine. Since the influence of spherical aberration that depends on the NA of the objective lenses La and Lb is used, erroneous discrimination due to variations in disk reflectivity can be eliminated. As a result, stable discrimination with high accuracy is possible, and switching of objective lenses is possible. Mistakes can be prevented.

  By comparing the ratio of the amplitude value of the S-shaped signal with a predetermined threshold (# 22), if the amplitude value of the S-shaped signal is compared, the accuracy can be further improved and reliable discrimination is possible. Become. For example, if red / infrared objective lens La is selected, S1> S2, and if blue objective lens Lb is selected, if S1≈S2, the threshold value is 1.5-2. It is preferable to set to. It is also preferable to average the measured values of the S-shaped amplitude value ratio S1 / S2 and set the threshold in the middle. For example, S1 / S2 = 2.5 when the red / infrared objective lens La is selected, and S1 / S2 = 0.5 when the blue objective lens Lb is selected. The threshold value may be 1.5. If 1 is set as the threshold value, the control can be performed more easily because it is sufficient to compare the S-shaped amplitude value S1 and the S-shaped amplitude value S2.

  In general, a lens material for DVD / CD is not designed to use a short wavelength laser. For this reason, when the short wavelength blue laser beam B1 is incident on the red / infrared objective lens La, the objective lens La is melted or the coating provided on the surface of the objective lens La is peeled off. It will occur. Since the optical disk device 20 is configured to use the long-wavelength red laser beam B2 that does not cause the objective lens La to be deteriorated, the objective lens La can be prevented from being deteriorated. Even when the infrared laser beam B3 is used for discrimination instead of the red laser beam B2, the deterioration of the objective lens La can be similarly prevented.

  In the configuration of the optical pickup 10 that switches between the red / infrared objective lens La and the blue objective lens Lb as in the present embodiment, the infrared laser beam B3 is discriminated instead of the red laser beam B2. It may be used. Further, in the configuration of the optical pickup that switches between the red objective lens and the blue objective lens, the red laser beam may be used for discrimination, and the infrared objective lens and the blue objective lens are switched. In the configuration of the optical pickup, an infrared laser beam may be used for discrimination.

1 is a schematic configuration diagram schematically showing an embodiment of an optical disc device. The top view which shows schematic structure of the actuator in FIG. The flowchart which shows control of the switching of an objective lens, and its confirmation. Explanatory drawing which shows S character amplitude which changes with the combination of the objective lens arrange | positioned in an optical path, and the setting state of an aberration correction element.

Explanation of symbols

B1 Blue laser beam (first laser beam)
B2 Red laser beam (second laser beam)
B3 Infrared laser beam (third laser beam)
Lb Blue objective lens (first objective lens)
La Red / Infrared objective lens (second objective lens)
1b Blue semiconductor laser (first laser light source)
1a Red / infrared semiconductor laser (second and third laser light sources)
2 Dichroic prism (light path synthesis element)
3 Polarizing beam splitter (optical path branching element)
4 Collimating lens 5 Aberration correction element (expander lens)
6 Raising mirror 7 1/4 wavelength plate 8 Actuator 9 Optical detector 10 Optical pickup 11 Optical disk 12 Control unit 13 Base 14 Axis 15 Lens holder 16 Magnet 17 Tracking coil 20 Optical disk device

Claims (6)

A first laser light source emitting a blue laser beam;
A second laser light source that emits a red laser beam;
A third laser light source that emits an infrared laser beam;
An optical path combining element that combines the optical paths of the blue, red, and infrared laser beams;
An aberration correction element that is arranged in the combined optical path and corrects the spherical aberration of at least one laser beam;
A first objective lens disposed in the combined optical path for imaging a blue laser beam onto a corresponding optical disk;
A second objective lens that is arranged in the combined optical path and focuses the red and infrared laser beams on the corresponding optical disks;
An actuator that performs lens switching so that one of the first and second objective lenses is located at a predetermined position in the combined optical path;
A photodetector for detecting optical information by receiving a laser beam reflected by the optical disc;
An optical path branching element that branches an optical path from each laser light source to the optical disk and an optical path from the optical disk to the photodetector;
Is an optical disk device equipped with an optical pickup,
An amplitude value of an S-shaped signal obtained by receiving the red laser beam with the photodetector in a state where the aberration correction element is set to an optimum value for correcting the spherical aberration of the blue laser beam, and the aberration correction element Is set to an optimum value for correcting the spherical aberration of the red laser beam, and the ratio of the amplitude value of the S-shaped signal obtained by receiving the red laser beam with the photodetector is compared with a predetermined threshold value. Thus, it is determined whether the objective lens arranged in the combined optical path is the first objective lens or the second objective lens, and the actuator is used until the determination result matches the target objective lens. An optical disc apparatus characterized by switching lenses. A first laser light source that emits a first laser beam having a short wavelength;
A second laser light source that emits a long-wavelength second laser beam;
An optical path combining element that combines the optical paths of the first and second laser beams;
An aberration correction element that is arranged in the combined optical path and corrects the spherical aberration of at least one laser beam;
A first objective lens that is disposed in the combined optical path and forms an image of the first laser beam on the corresponding optical disk;
A second objective lens that is arranged in the combined optical path and forms an image of the second laser beam on the corresponding optical disk;
An actuator that performs lens switching so that one of the first and second objective lenses is located at a predetermined position in the combined optical path;
A photodetector for detecting optical information by receiving a laser beam reflected by the optical disc;
An optical path branching element that branches an optical path from each laser light source to the optical disk and an optical path from the optical disk to the photodetector;
Is an optical disk device equipped with an optical pickup,
An amplitude value of an S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to an optimum value for correcting the spherical aberration of the first laser beam; An amplitude value of an S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to an optimum value for correcting the spherical aberration of the second laser beam; To discriminate which of the first objective lens and the second objective lens the objective lens arranged in the combined optical path is.   3. The optical disc apparatus according to claim 2, wherein the first laser beam is a blue laser beam, and the second laser beam is a red laser beam. A first laser light source that emits a first laser beam having a short wavelength;
A second laser light source that emits a long-wavelength second laser beam;
A third laser light source for emitting a third laser beam having a longer wavelength than the second laser beam;
An optical path combining element that combines the optical paths of the first to third laser beams;
An aberration correction element that is arranged in the combined optical path and corrects the spherical aberration of at least one laser beam;
A first objective lens that is disposed in the combined optical path and forms an image of the first laser beam on the corresponding optical disk;
A second objective lens that is arranged in the combined optical path and focuses the second and third laser beams on the corresponding optical disks;
An actuator that performs lens switching so that one of the first and second objective lenses is located at a predetermined position in the combined optical path;
A photodetector for detecting optical information by receiving a laser beam reflected by the optical disc;
An optical path branching element that branches an optical path from each laser light source to the optical disk and an optical path from the optical disk to the photodetector;
Is an optical disk device equipped with an optical pickup,
An amplitude value of an S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to an optimum value for correcting the spherical aberration of the first laser beam; An amplitude value of an S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to an optimum value for correcting the spherical aberration of the second laser beam; To discriminate which of the first objective lens and the second objective lens the objective lens arranged in the combined optical path is.   5. The optical disk according to claim 4, wherein the first laser beam is a blue laser beam, the second laser beam is a red laser beam, and the third laser beam is an infrared laser beam. apparatus.   An amplitude value of an S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to an optimum value for correcting the spherical aberration of the first laser beam; An amplitude value of an S-shaped signal obtained by receiving the second laser beam with the photodetector in a state where the aberration correction element is set to an optimum value for correcting the spherical aberration of the second laser beam; 6. The optical disk apparatus according to claim 2, wherein the amplitude value of the S-shaped signal is compared by comparing the ratio of the S-signal with a predetermined threshold value.

Images