JPWO2007046256A1 - Optical head device and optical disk device - Google Patents

Abstract

In order to provide a compact optical head device capable of performing stable information recording / reproducing on a plurality of standard optical discs and an optical disc device equipped with the same, the optical head device is moved in the optical axis direction. A collimator lens 4 that corrects spherical aberration is provided, and the collimator lens 4 is used in common for a plurality of optical discs of different standards, and a standard that maximizes the moving distance of the collimator lens 4 among the optical discs of different standards. The movement range of the collimator lens 4 with respect to other optical discs is included in the movement range of the collimator lens 4 with respect to other optical discs.

Description

  The present invention relates to an optical head device capable of recording and / or reproducing information (hereinafter referred to as “recording / reproducing”) on a plurality of optical discs of different standards, and an optical disk device equipped with the optical head device.

  Conventionally, in order to increase the capacity of an optical disk, the size of information (bits) written on a track of the optical disk is reduced, and in order to perform recording / reproduction of information with respect to an optical disk having a large capacity, The size of the focused spot has been reduced by shortening the wavelength and increasing the numerical aperture of the objective lens.

  For example, in a CD (compact disc), the thickness of a disc substrate that becomes a light transmission layer (a transparent protective layer and a space layer provided on the information recording layer, also referred to as “transparent substrate”) is about 1.2 mm, The laser light wavelength is about 780 nm, the numerical aperture (NA) of the objective lens is 0.45, and the storage capacity is 650 MB. In a DVD (Digital Versatile Disc), the thickness of the disc substrate serving as a light transmission layer is about 0.6 mm, the laser beam wavelength is about 650 nm, the numerical aperture is 0.6, and the storage capacity is 4.7 GB. A DVD is, for example, a 1.2 mm thick disk in which two disk substrates having a thickness of about 0.6 mm are bonded together.

  In a high-density BD (Blu-ray Disc), the thickness of the light transmission layer is reduced to 0.1 mm, the laser light wavelength is about 405 nm, the numerical aperture is 0.85, and the storage capacity is 23 GB or more. The capacity has been increased. Further, in HDDVD (High Definition Digital Versatile Disc), the thickness of the disc substrate serving as a light transmission layer is 0.6 mm, which is the same as DVD, the laser light wavelength is about 405 nm, and the numerical aperture is 0.65. The capacity is increased to 18 GB or more.

  Thus, there are various standards for optical disks such as CD, DVD, BD, and HDDVD. In general, an optical disk recording / reproducing apparatus is capable of recording / reproducing information with respect to an optical disk of a plurality of standards (also referred to as “compatible recording / reproducing apparatus”). For example, a DVD recording / reproducing apparatus can generally record / reproduce information on a CD in addition to recording / reproducing information on / from a DVD. Further, in general, a BD recording / reproducing apparatus can perform recording / reproduction of information on a DVD and recording / reproduction of information on a CD in addition to recording / reproduction of information on a BD. Furthermore, an optical disk recording / reproducing apparatus capable of recording / reproducing information on all of CD, DVD, BD, and HDDVD is also conceivable. The compatible recording / reproducing apparatus is capable of recording / reproducing information on / from a conventional standard optical disk owned by a user, and thus is highly convenient and plays an important role in smoothly spreading the new standard optical disk.

  The compatible recording / reproducing apparatus is equipped with an optical head device capable of recording / reproducing information with a common optical system for various optical discs corresponding to each standard (see, for example, Patent Document 1). Since such an optical head device shares many optical systems, there is an advantage that it can be reduced in size and cost without increasing the number of components.

  A problem that becomes apparent due to the shortening of the wavelength of laser light and the increase of the numerical aperture of the objective lens accompanying an increase in the capacity of the optical disk is a variation in spherical aberration caused by a thickness error of the light transmission layer of the optical disk. Since the spherical aberration caused by the thickness error of the light transmission layer is proportional to the fourth power of the numerical aperture of the objective lens, the influence of the thickness error of the light transmission layer increases as the numerical aperture of the objective lens increases, and stable information Recording / reproduction becomes difficult.

  In order to perform stable recording / reproduction with respect to optical discs of a plurality of standards, depending on various conditions (laser light wavelength, numerical aperture of the objective lens, and thickness of the light transmission layer) set for each optical disc standard. Each generated spherical aberration must be corrected, and means for correcting the spherical aberration is required. Typical means for correcting the spherical aberration include a means that uses a beam expander by a relay lens in which a plurality of lenses are combined, and a collimator lens that converts a divergent light beam emitted from a light source into a substantially parallel light beam. There are means to use (for example, see Patent Documents 2 and 3). All of these means change the incident condition of the light beam to the objective lens by moving the lens position in the optical axis direction, and reduce the spherical aberration of the light beam condensed on the information recording layer of the optical disk. A correction method is adopted. In the present application, the optical means having a function of correcting spherical aberration is referred to as “spherical aberration correcting means”, and the spherical aberration correcting means including a correction lens such as a relay lens or a collimator lens is referred to as “spherical aberration correcting lens”. To tell. Further, in order to move the spherical aberration correcting means in the optical axis direction, driving means using an electromagnetic force or a motor is provided.

JP 2005-203004 A JP 2005-209325 A JP 2002-197712 A

  In the conventional optical head device described above, the amount of spherical aberration to be corrected differs depending on the thickness of the light transmission layer of the optical disk, the wavelength of the laser beam, and the numerical aperture of the objective lens, which are determined by each standard. The optimum position and moving distance of the spherical aberration correcting means for correcting the aberration are also different. Therefore, in the conventional optical head device, when the spherical aberration occurring in each of the plurality of standard optical disks is to be corrected by the common spherical aberration correction means, the optimum position of the spherical aberration correction means for each of the plurality of standard optical disks. Since the movement distance is different, the movement range of the spherical aberration correction means (or the lens driving stroke when the spherical aberration correction means is a spherical aberration correction lens) increases, and the size of the optical head device increases. there were. In particular, the optical disk has a plurality of information recording layers, and if the spherical aberration correction is performed in each of the multilayer information recording layers, the moving distance of the spherical aberration correcting means is further increased, so that the size of the optical head device is further increased. There was a problem of becoming.

  The present invention has been made to solve the above-described problems of the prior art, and is a compact optical head device capable of recording and reproducing information stably with respect to a plurality of standard optical discs, and an optical disc equipped with the same. An object is to provide an apparatus.

  The optical head device of the present invention is a device capable of recording and / or reproducing information with respect to a plurality of optical discs of different standards, a light source for irradiating light of a predetermined wavelength, and light from the light source Is used in common for a plurality of optical discs of different standards, and is installed on the optical path of light emitted from the light source, and moved from the light source by moving in the optical axis direction. Spherical aberration correction means for correcting spherical aberration in the information recording layer of the optical disc by changing the divergence angle or convergence angle of the emitted light, and driving means for moving the spherical aberration correction means in the optical axis direction. Among the plurality of optical discs of different standards, other standards are included within the moving range of the spherical aberration correcting unit relative to the standard optical disc having the maximum moving distance of the spherical aberration correcting unit. That includes movement range of the spherical aberration correction means for an optical disc, constitute the objective lens and the spherical aberration correction means in the moving range satisfy the condition of the spherical aberration correction means.

  An optical disc apparatus according to the present invention includes the optical head device described above, and includes a recording / reproducing unit that records and / or reproduces information on the optical disc, a disc discriminating unit that detects the type of the optical disc, and an optical disc detected by the disc discriminating unit. Control for selecting one of the plurality of objective lenses of the optical head device according to the type of the optical head device and moving it on the optical path by the objective lens switching means, and the spherical aberration correcting means of the optical head device Control means for performing control for moving the motor by the driving means.

  According to the present invention, the moving range of the spherical aberration correcting unit for all other standard optical discs is included in the moving range of the spherical aberration correcting unit for the standard optical disc having the maximum moving distance of the spherical aberration correcting unit. Further, since the optical head device is configured, it is possible to avoid an increase in the moving distance of the spherical aberration correcting means in the optical head device. Therefore, according to the present invention, it is possible to reduce the size of the optical head device and to reduce the size of the optical disk device on which the optical head device is mounted.

  Further, according to the present invention, since spherical aberration of a plurality of standard optical discs can be corrected, stable information recording / reproduction with respect to the optical disc can be performed.

  Furthermore, according to the present invention, an increase in the moving distance of the spherical aberration correcting means in the optical head device can be avoided, so that the spherical aberration correcting operation executed after the optical disk to be recorded and reproduced is replaced with an optical disk of a different standard. The time required can be shortened.

FIG. 2 is a diagram schematically showing a configuration of an optical system when recording / reproducing information on / from a standard A optical disk, which is an optical head device according to Embodiment 1 of the present invention. FIG. 2 is a diagram schematically showing a configuration of an optical system in the optical head device according to the first embodiment when information is recorded / reproduced on / from a standard B optical disc. 1 is a block diagram schematically showing a configuration of an optical disk device on which an optical head device according to Embodiment 1 is mounted. (A) and (b) schematically show the structure of an information recording layer of an optical disc of standard A and the structure of an information recording layer of an optical disc of standard B that are irradiated with a light beam by the optical head device according to the first embodiment. It is sectional drawing. (A) is a figure which shows the relationship between the position of a collimator lens when a light beam is irradiated to each information recording layer of the optical disk of standard A by the optical head apparatus based on Embodiment 1, and spherical aberration, (b). These are figures which show the relationship between the position of a collimator lens and spherical aberration when each optical recording device of the standard B irradiates each information recording layer with a light beam. The position of the collimator lens when the information recording layer of the standard A optical disk is irradiated with a light beam by the optical head device according to the first embodiment, and each information of the standard B optical disk by the optical head device according to the first embodiment. It is a figure which shows the position of the collimator lens when irradiating a recording layer with a light beam. The position of the collimator lens when the information recording layer of the standard A optical disk is irradiated with the light beam by the optical head device according to the first embodiment, and the information recording layer of the standard B optical disc by the optical head device according to the first embodiment. FIG. 4 is a diagram showing the position of a collimator lens when irradiating a light beam to the optical recording medium and the position of the collimator lens when irradiating each information recording layer of a standard C optical disk by the optical head device according to the first embodiment. (A) And (b) is a figure which shows roughly the structure of the principal part of the optical system of the optical head apparatus of a comparative example, (c) is each of the optical disk of the standard A with the optical head apparatus of a comparative example. It is a figure which shows the position of the collimator lens when irradiating the information recording layer with the light beam, and the position of the collimator lens when irradiating each information recording layer of the optical disc of the standard B with the optical head device of the comparative example. (A) And (b) is a figure which shows schematically the structure of the principal part of the optical system of the optical head apparatus based on Embodiment 2 of this invention, (c) is the light which concerns on Embodiment 2. FIG. The position of the collimator lens when the information recording layer of the standard A optical disk is irradiated with a light beam by the head device, and the time of irradiating the information recording layer of the standard B optical disk with the optical head device according to the second embodiment It is a figure which shows the position of this collimator lens. (A) And (b) is a figure which shows schematically the structure of the principal part of the optical system of the optical head apparatus based on Embodiment 2, (c) is the optical head apparatus based on Embodiment 2. The position of the collimator lens when the information recording layer of the standard A optical disc is irradiated with the light beam, and the collimator lens when the information recording layer of the optical disc of the standard B is irradiated with the light beam by the optical head device according to the second embodiment. FIG. An optical head device according to Embodiment 3 of the present invention uses an optical disk having a single information recording layer, an optical disk having two information recording layers, another optical disk having a single information recording layer, and two information recording layers. It is a figure which shows the position of the collimator lens when irradiating a light beam to another optical disk. FIG. 10 is a diagram schematically showing a configuration of an optical system when performing recording / reproduction of information with respect to an optical disc of standard A, which is an optical head device according to Embodiment 4 of the present invention. FIG. 10 is a diagram schematically showing a configuration of an optical system when recording / reproducing information on / from a standard C optical disk, which is an optical head device according to a fourth embodiment. FIG. 10 is a block diagram schematically showing a configuration of an optical disc device on which an optical head device according to Embodiment 4 is mounted. (A) is a figure which shows the relationship between the position of a collimator lens when a light beam is irradiated to each information recording layer of the optical disk of standard C by the optical head apparatus based on Embodiment 4, and spherical aberration, (b). Are the positions of the collimator lenses when the optical recording device irradiates each information recording layer of the standard A optical disk with the optical head device according to the fourth embodiment, and the optical head device according to the fourth embodiment. It is a figure which shows the position of a collimator lens when a light beam is irradiated to an information recording layer. FIG. 10 is a diagram schematically showing a configuration of another optical system of an optical head device according to Embodiment 4. FIG. 10 is a diagram schematically showing a configuration of another optical system of an optical head device according to Embodiment 4. FIG. 10 is a diagram schematically showing a configuration of another optical system of an optical head device according to Embodiment 4. An optical head device according to Embodiment 5 of the present invention uses an optical disk having a single information recording layer, an optical disk having two information recording layers, another optical disk having a single information recording layer, and two information recording layers. It is a figure which shows the position of the collimator lens when irradiating a light beam to another optical disk. By the optical head device of the comparative example, a light beam is applied to an optical disk having a single information recording layer, an optical disk having two information recording layers, another optical disk having a single information recording layer, and another optical disk having two information recording layers. It is a figure which shows the position of the collimator lens when irradiating.

Explanation of symbols

  1, 31a, 31c, 31d, 310, 311 light source, 2, 32a, 32c, 32d light beam, 3, 33a, 33c, 33d diffraction grating, 4, 34a, 34c, 34d polarization beam splitter, 41 transmission through polarization beam splitter Reflective surface, 5,35 collimator lens (spherical aberration correcting means), 6,36 1/4 wavelength plate, 7a, 7b, 7c, 7d objective lens, 8a standard A optical disk, 8b standard B optical disk, 8c standard C Optical disk, 8d standard D optical disk, 9,39 cylindrical lens, 10,40 sensor lens, 11,41 photodetector, 12 lens driving means, 14 objective lens switching means, 15 objective lens actuator, 16,17 recording / reproducing means 101 Disc discriminating means, 102 control means.

Embodiment 1 FIG.
FIG. 1 is an optical head device according to Embodiment 1 of the present invention, and is a diagram schematically showing the configuration of an optical system when recording / reproducing information on / from a standard A optical disk 8a. FIG. 2 is a diagram schematically showing a configuration of an optical system when recording / reproducing information on / from an optical disc 8b of a standard B different from the standard A, which is the optical head device according to the first embodiment. As shown in FIG. 1 and FIG. 2, the optical head device according to Embodiment 1 has a plurality of standard optical disks 8a and 8b (standard A optical disk 8a and standard) that are defined to record and reproduce with light of the same wavelength. Information can be recorded / reproduced on the B optical disk 8b).

  As shown in FIGS. 1 and 2, the optical head device according to Embodiment 1 includes a light source 1, a diffraction element 3, a polarization beam splitter 4, a collimator lens 5 serving as spherical aberration correcting means, 1 wavelength plate 6, objective lens 7a for standard A optical disc 8a, objective lens 7b for standard B optical disc 8b, cylindrical lens 9, sensor lens 10, photodetector 11, and collimator lens 5 Lens driving means 12 for moving the objective lens 7 in the optical axis direction, and objective lens switching means 14 which is a mechanism for placing either the objective lens 7a or the objective lens 7b on the optical path.

The light source 1 is, for example, a semiconductor laser, and emits a light beam (laser light) 2 having a wavelength λ ₁ . The diffraction element 3 divides the light beam 2 emitted from the light source 1 into a plurality of light beams. The polarization beam splitter 4 has a transmission / reflection surface 41 that transmits the p-polarized component and reflects the s-polarized component. The collimator lens 5 converts the spread angle (divergence angle or convergence angle) of the light beam 2. The quarter-wave plate 6 converts incident linearly polarized light into circularly polarized light, and converts incident circularly polarized light into linearly polarized light.

  The objective lens 7a is placed on the optical path by the objective lens switching means 14 when the information is recorded on and reproduced from the standard A disk 8a, and the light beam 2 is condensed on the information recording layer of the optical disk 8a. The objective lens 7b is placed on the optical path by the objective lens switching means 14 when the information is recorded / reproduced with respect to the standard B disk 8b, and the light beam 2 is condensed on the information recording layer of the optical disk 8b.

The lens driving unit 12 includes, for example, a guide mechanism (not shown) extending in the optical axis direction, and a driving force generating mechanism such as an electromagnetic force or a motor that moves the collimator lens 5 in the optical axis direction along the guide mechanism. Have. As shown in FIG. 1, the position of the collimator lens 5 when based on the light emission point of the light source 1 (i.e., the distance from the emission point of the light source 1 to the collimator lens 5) and z _5.

  The objective lens switching unit 14 slides the objective lens support member (not shown) that supports the objective lens 7a or the objective lens 7b and the objective lens support member, so that one of the objective lenses 7a and 7b is changed, for example. And an objective lens driving means (not shown) that can be selectively moved on the optical path of the light beam by electromagnetic force. Therefore, the objective lens 7a and the objective lens 7b are switched according to the optical disc of each standard, and information recording / reproduction with respect to the optical disc of a different standard can be executed by irradiating a focused spot of good quality.

  Next, the operation of the optical head device according to the first embodiment will be described. As shown in FIG. 1, the light beam 2 emitted from the light source 1 is divided into a plurality of light beams by the diffraction element 3. Of the divided light beams, the main light beam (the reference numeral “2” is also used for this light beam) is transmitted through the polarization beam splitter 4, the collimator lens 5, the quarter-wave plate 6, Then, the light passes through the objective lens 7a and is irradiated onto the standard A optical disc 8a. In FIG. 1, other light beams divided by the diffraction element 3 are not shown.

  The light beam 2 diffracted and reflected by the optical disk 8a is again transmitted through the objective lens 7a and converted into a substantially parallel light beam, then passes through the quarter-wave plate 6 and the polarization direction is rotated by 90 degrees. The light is converted into linearly polarized light, passes through the collimator lens 5, and enters the polarization beam splitter 4. The polarization beam splitter 4 reflects and deflects the light beam 2 reflected from the optical disk 8a and transmitted through the quarter-wave plate 6 and the collimator lens 5 by the transmission / reflection surface 41. The light beam 2 reflected by the transmission / reflection surface 41 passes through the cylindrical lens 9 for adding astigmatism and the sensor lens 10 for converting the light collecting magnification of the light beam 2 and enters the light detector 11. In addition, when conversion of a condensing magnification is unnecessary, it is not necessary to provide the sensor lens 10, and the sensor lens 10 should just be installed as needed.

  The photodetector 11 has a plurality of divided light receiving surfaces, and converts the light amount of the light beam 2 received by each divided light receiving surface into an electric signal. Based on the reflected light from the optical disk 8a, the divided light-receiving surface of the photodetector 11 is information on the recording information arranged in a defocus amount from the information recording layer of the optical disk 8a, a substantially concentric circle or a substantially spiral shape of the optical disk 8a. In order to be able to detect the track deviation amount of the focused spot from the track, the spherical aberration, and the reproduction signal of the recorded information, it is formed in a shape and arrangement corresponding to each detection method. A configuration for detecting a focus shift amount, a track shift amount, a spherical aberration, and a reproduction signal based on reflected light from an optical disc is known. For example, International Publication No. WO2005 / 117003 (Patent Document 4) discloses. Explained.

As shown in FIG. 2, the optical head device according to the first embodiment can record and reproduce information on an optical disc 8b of a standard B different from the standard A of the optical disc 8a. The optical head device according to Embodiment 1 includes an objective lens 7b corresponding to the standard of the optical disk 8b. The numerical aperture of the objective lens 7a and NA _a, the numerical aperture of the objective lens 7b is taken as NA _b, we have a relationship of NA b <NA _a. In FIG. 2, the objective lens switching means 14 moves the objective lens 7b on the optical path of the light beam. As shown in FIG. 2, even when the objective lens 7b is switched to record / reproduce information to / from the standard B optical disc 8b, the path through which the light beam 2 propagates is the same as that shown in FIG. It is the same.

In the optical head device of the present invention, the numerical aperture NA _a of the objective lens 7a is 0.7 or more. As will be described later, since the spherical aberration is proportional to the fourth power of the numerical aperture of the objective lens, light using an objective lens having a relatively large numerical aperture of 0.7 or more as in the optical head device of the first embodiment. In the case of the head device, spherical aberration correction means such as a collimator lens 5 is required. In the DVD standard where the numerical aperture of the objective lens is 0.65, the occurrence of spherical aberration is small, so that recording and reproduction can be performed without correcting the spherical aberration.

  FIG. 3 is a block diagram schematically showing a configuration of the optical disk device on which the optical head device according to the first embodiment is mounted. As shown in FIG. 3, the optical disc apparatus according to Embodiment 1 is, for example, an optical disc recording / reproducing device, and includes recording / reproducing means 16 including an optical head device, disc discriminating means 101 for discriminating the type of optical disc, and control. Means 102. The recording / reproducing means 16 includes a light source 1, a light detector 11, a lens driving means 12, an objective lens switching means 14, and an objective lens actuator 15 capable of moving the objective lens in the optical axis direction and the radial direction of the optical disk. (Not shown in FIGS. 1 and 2). The recording / reproducing means 16 also has other configurations necessary for recording / reproducing the optical disc, such as a mechanism (not shown) for rotating the optical disc on the turntable. The control means 102 performs defocus detection, tracking error detection, spherical aberration detection, and reproduction signal detection based on the detection signal of the light detector 11. Disc discriminating means 101 discriminates the type of the optical disc by selecting the amplitude of the defocus detection signal and the count number of each information recording layer of the multilayer disc as the characteristics of the optical disc. The control unit 102 controls the objective lens switching unit 14 based on the detection signal from the disc determination unit 101. At the time of recording / reproducing, the control unit 102 drives the collimator lens 5 based on detection signals of defocus detection, tracking error detection, spherical aberration detection, and reproduction signal detection and the detection signal of the disc discrimination unit 101. The objective lens actuator 15 that drives the lens driving means 12 and the objective lens to be controlled is controlled.

4A and 4B show the structure of the information recording layer of the standard A optical disk 8a and the structure of the information recording layer of the standard B optical disk 8b irradiated with the light beam by the optical head device according to the first embodiment. It is sectional drawing shown roughly. As shown in FIGS. 4A and 4B, the standard A optical disc 8a and the standard B optical disc 8b each have a plurality of information recording layers (shown by broken lines) in the optical disc. As shown in FIG. 4 (a), the optical disc 8a is (n is a positive integer) first to n LA ₁ layer is a first information recording layer of the information recording layer n layer to LA _n layer is the It has an information recording layer. Further, as shown in FIG. 4 (b), the optical disc 8b is, m from LB ₁ layer is a first information recording layer to the LB _m layer which is an information recording layer of the m (m is a positive integer) It has an information recording layer. 4 as (a), the respective information from the surface LA _S of the optical disc 8a recording layer _{LA 1, LA 2, ...,} respectively a distance to _{LA n, tA 1, tA 2} , ..., shown by tA _n . Further, FIG. 4 as shown in (b), the information from the surface LB _S of the optical disc 8b recording layer _{LB 1,} LB 2, ..., respectively a distance to _{LB n, tB 1, tB 2} , ..., tB m It shows with. A space layer is formed between the information recording layers.

4 (a) shows a state in which the light beam 2 having passed through the objective lens 7a of the numerical aperture NA _a is focused on LA ₁ layer and LA _n layer of the optical disc 8a standards A. Further, FIG. 4 (b) shows a state in which the light beam 2 having passed through the objective lens 7b of aperture NA _b is focused on LB ₁ layer and LB _m layer of the optical disc 8b standard B.

Hereinafter, a configuration for correcting spherical aberration with respect to each standard optical disk by the common collimator lens 5 will be described. The spherical aberration SA of the light beam condensed on a specific information recording layer is the difference in thickness t _d from the thickness of the light transmission layer in which the spherical aberration is already corrected in the initial state, the wavelength λ of the light beam, and the aperture There is a relationship of the following equation with the number NA.
SA∝t _d × NA ⁴ / λ
Therefore, even with the same thickness difference t _d and the same wavelength λ, if the numerical aperture NA used in the standard is different, the spherical aberration SA changes in proportion to the fourth power of NA. Further, when changing the information recording layer that is subject to recording and playback in the same optical disk, since the thickness difference t _d is changed, new spherical aberration is generated according to the thickness difference t _d. In addition, when switching to an optical disc of a different type, particularly an optical disc with a different standard, the thickness difference t _d , the wavelength λ, and the numerical aperture NA change according to the standard. Similarly, the thickness difference t _d , the wavelength λ, and the aperture A spherical aberration SA corresponding to the number NA occurs.

  The spherical aberration SA can be corrected as follows. The collimator lens 5 converts the divergence angle of the light beam 2 radiated from the light source 1 and makes the light beam 2 enter the objective lens 7a or the objective lens 7b. When the collimator lens 5 is moved in the optical axis direction, the light beam 2 emitted from the collimator lens 5 can be diverged or converged, and the incident condition of the light beam 2 on the objective lens 7a or the objective lens 7b is changed. Thus, the spherical aberration of the light beam 2 on the desired information recording layer of the optical disc 8a and the optical disc 8b can be changed. Therefore, when the information recording layer to be recorded / reproduced is switched in the same optical disc, or when the optical disc to be recorded / reproduced is switched to an optical disc of a different standard, the collimator is corrected so that the spherical aberration generated by the switching is corrected. The position of the lens 5 is moved to an optimum position by the lens driving means 12.

  As the spherical aberration correcting means, a liquid crystal element can be used instead of the collimator lens 5. However, in the optical head device according to the first embodiment, a case will be described in which a collimator lens (which may be a coupling lens or a relay lens) is adopted as the spherical aberration correction means. When the spherical aberration correction means is composed of a liquid crystal element, there arises a problem that the wavefront aberration is deteriorated if the positional relationship between the electrode pattern provided on the transparent electrode and the entrance pupil of the objective lens is shifted in order to give an electric field distribution to the liquid crystal. To do. The positional adjustment accuracy is on the order of several microns, which increases the manufacturing cost from the viewpoint of assembly. In order to prevent this, a method of integrating the liquid crystal element and the objective lens so that the positional relationship does not shift has been devised. However, in addition to increasing the weight of the movable part, a power supply line to the transparent electrode of the liquid crystal element is required. , Performance and manufacturing problems occur. Even in an optical head device that records and reproduces information with respect to an optical disk with a relatively small standard numerical aperture of 0.65, such as a DVD, spherical aberration is as much as possible in order to ensure a margin of recording characteristics. In some cases, a spherical aberration correcting liquid crystal element is applied to reduce the size. In such an optical head device, the spherical aberration correcting liquid crystal element operates without any problem in a configuration in which the positional relationship with the objective lens is shifted during operation by being disposed in the fixed portion. However, when the numerical aperture of at least one objective lens is as large as 0.7 or more as in the optical head device of the present invention, the spherical aberration correcting liquid crystal element is not fixed to the fixed portion unlike the optical head device for DVD use. If they are arranged, there is a problem that the deterioration of the wavefront aberration appears remarkably due to the occurrence of coma aberration due to the positional relationship with the objective lens deviating. In view of the above, it is more advantageous in terms of cost and performance to configure the spherical aberration correcting means with lens parts such as a collimator lens. For this reason, in the optical head device of the first embodiment, a case where a collimator lens is employed as the spherical aberration correction means will be described.

FIGS. 5A and 5B are diagrams showing changes in spherical aberration SA when the position of the collimator lens 5 is moved with respect to each information recording layer of the optical disc 8a of standard A and the optical disc 8b of standard B, respectively. It is. Taking the horizontal axis position z ₅ of the collimator lens 5 as z-direction, the spherical aberration SA in each information recording layer, a characteristic as a substantially V-or substantially U-shaped. Since the distances tA ₁ , tA ₂ ,... Or the distances tB ₁ , tB ₂ ,... From the surface of the optical disc to each information recording layer are different, as shown in FIGS. The characteristic of spherical aberration in each information recording layer is a characteristic that is relatively shifted in the z direction in proportion to the thickness difference of the light transmission layer between the information recording layers.

  In the standard of the optical disc on which information is recorded / reproduced by the optical head device according to the first embodiment, the light beam having the same wavelength is used. Therefore, the spread angle of the light beam 2 emitted from the collimator lens 5 is the standard of the optical disc. , And changes according to the position of the collimator lens 5. Therefore, the horizontal axis of FIGS. 5A and 5B corresponds to the spread angle of the light beam emitted from the collimator lens 5.

Usually, the objective lens is designed so that the spherical aberration is optimally corrected by the thickness of the light transmission layer provided on the information recording layer serving as a preset reference. Regarding the thickness setting of the light transmission layer in the design of the objective lens, various thickness settings are made depending on the purpose and application, and the degree of design freedom is relatively large. In particular, if optimal design is performed for each standard optical disc, the thickness of the light transmission layer for correcting spherical aberration in advance can be designed in any way. That is, for example, when considering the objective lens 7a for an optical disc of standard A, the thickness of the light transmission layer in which spherical aberration is optimally corrected under an incident condition at a certain divergence angle (including a parallel light flux state) is from LA ₁ layer. It may be either from the thicknesses tA ₁ to LA _n layer until tA _n, or, for example, is set to an intermediate thickness between the thickness tA ₂ and LA ₃ layer thickness tA ₃ of LA ₂ layers It may be. The same applies to the objective lens for optical discs of other standards such as standard B.

  For each information recording layer in which the optical transmission layer of the optical disc has a different thickness, the design that minimizes the spherical aberration characteristics (optimum design) is, for example, the shape (curvature, etc.) of the lens surface of the objective lens and the thickness of the lens. It can be realized by optimizing the above. If the objective lens is a diffractive lens having a concentric groove structure on the lens surface, the optimum design can be achieved by optimizing the groove depth and groove pitch. Such a design is a normal lens design technique.

  For example, Japanese Patent Application Laid-Open No. 2004-69810 (Patent Document 5) or Japanese Patent Application Laid-Open No. 2002-324333 (Patent Document 6) commonly uses a diffraction type objective lens for a plurality of optical disks having different recording densities. An optical element for an optical system that can be used is shown. In these documents, a technique for providing an annular structure centering on the optical axis on the surface of an optical element and forming a plurality of uneven structures in each annular zone is shown. According to this technology, in addition to correcting the spherical aberration due to the thickness error of the light transmission layer, even if the light transmission layer having a thickness other than the thickness of the light transmission layer set by the standard is optimized, It has been shown that it is possible to correct spherical aberration in accordance with the thickness. However, there are many methods for designing the spherical aberration of this type of objective lens, the groove structure of the diffractive surface is various, and is not limited to the groove structure disclosed in Patent Documents 5 and 6.

  Therefore, for example, by applying the above-described technique, the spherical aberration correction characteristics of the collimator lens 5 can be shifted in the z direction as shown in FIGS. 5 (a) and 5 (b). In the first embodiment, the standard A is set so that the movement range of the collimator lens 5 with respect to another standard optical disk is included in the movement range of the collimator lens 5 with respect to the standard optical disk where the movement distance of the collimator lens 5 is the maximum. The design of the objective lens for the optical disc of any one of the standards B and B is adjusted, and the spherical aberration correction characteristic by the collimator lens 5 for the optical disc of the standard A or the standard B is shifted in the z direction.

That is, in order to perform spherical aberration correction on all the information recording layers from the LA ₁ layer to the LA _n layer of the standard A optical disc 8a, the position of the collimator lens 5 is as shown in FIG. It is necessary to ensure a lens driving stroke in the range of PA ₁ ≦ z ₅ ≦ PA _n . In order to perform spherical aberration correction on all information recording layers from the LB ₁ layer to the LB _m layer of the standard B optical disc 8b, as shown in FIG. 5B, the collimator lens 5 has PB ₁ ≦ PB ₁ ≦ It is necessary to secure the lens driving stroke of the lens driving means so that the range of z ₅ ≦ PB _m can be moved. However, when the lens driving stroke of the collimator lens 5 that needs to be secured for the standard A optical disk 8a is larger than the lens driving stroke of the collimator lens 5 secured for the standard B optical disk 8b, As shown in FIG. 6, the optical head device according to the first embodiment satisfies the relationship of PA ₁ ≦ PB ₁ and PB _m ≦ PA _n . With this configuration, as long as the lens driving stroke required for the spherical aberration correction for the standard A optical disc 8a is secured as the lens driving stroke of the collimator lens 5 by the lens driving means 12, the standards A and B can be used. Spherical aberration can be corrected for the information recording layer of any optical disc. In FIG. 6, black circles correspond to the bottom (V-shaped tip) position of the spherical aberration SA characteristic (V-shaped characteristic) of FIGS. 5 (a) and 5 (b).

  As a result, the required amount of the lens driving stroke of the collimator lens 5 driven by the lens driving unit 12 can be reduced, and the lens driving unit 12 can be reduced in weight and the entire optical system can be reduced in size. In addition, spherical aberration of a plurality of optical discs of different standards can be corrected, and stable information recording / reproduction can be performed. Furthermore, since the lens driving stroke is reduced, the time required for the spherical aberration correction operation can be shortened.

  In the above description, the optical head apparatus and the optical disk apparatus capable of recording / reproducing information with respect to the optical disks of the two standards A and B have been described. However, as shown in FIG. 7, the present invention also provides a spherical surface in an optical head device capable of recording / reproducing information with respect to optical discs of three or more standards, for example, standard A, standard B, and standard C. Movement of spherical aberration correction means relative to other standard optical disks (standard A, B optical disks) within the movement range of spherical aberration correction means relative to a standard optical disk (standard C optical disk) with the maximum movement distance of aberration correction means By configuring the range to be included, the same effect can be obtained.

Embodiment 2. FIG.
FIGS. 8A and 8B are diagrams schematically showing the configuration of the main part of the optical system of the optical head device of the comparative example, and FIG. 8C shows the standard A according to the optical head device of the comparative example. FIG. 5 is a diagram showing the position of a collimator lens when irradiating each information recording layer of the optical disc of FIG. 4 with a light beam and the position of the collimator lens when irradiating each information recording layer of the standard B optical disc with the optical head device of the comparative example It is. FIGS. 9A and 9B are diagrams schematically showing the configuration of the main part of the optical system of the optical head device according to Embodiment 2 of the present invention, and FIG. The position of the collimator lens when the information recording layer of the standard A optical disk is irradiated with the light beam by the optical head device according to the second embodiment and the information recording layer of the standard B optical disc by the optical head device according to the second embodiment It is a figure which shows the position of the collimator lens when irradiating with a light beam. Further, FIGS. 10A and 10B are diagrams schematically showing a configuration of a main part of the optical system of the optical head device according to the second embodiment, and FIG. 10C according to the second embodiment. The position of the collimator lens when the information recording layer of the standard A optical disk is irradiated with the optical head device by the optical head device and the information recording layer of the standard B optical disc are irradiated with the light beam by the optical head device according to the second embodiment. It is a figure which shows the position of the collimator lens at the time. Each figure shows only the optical path from the collimator lens 5 to each standard optical disk, and shows the optical path when each standard optical disk is recorded and reproduced. FIGS. 8C, 9C, and 10C show the spherical aberration correction characteristics of the collimator lens 5 in each configuration. 8 (a) and 8 (b), 9 (a) and 9 (b), 10 (a) and 10 (b), the same or corresponding configurations as those shown in FIG. 1 or 2 are the same. A sign is attached.

  The optical head device according to the second embodiment, like the optical head device according to the first embodiment, is a standard optical disc that uses an objective lens having a relatively large numerical aperture of 0.7 or more that requires spherical aberration correction. Is an optical head device capable of recording / reproducing information on / from a plurality of optical discs having different standards. Further, the spherical aberration correcting means of the optical head device according to the second embodiment is configured by a lens component such as a collimator lens as described in the first embodiment.

8A, 8B, and 8C are different in the incident angle condition of the standard A objective lens 7a and the standard B objective lens 7b, but even if the design of the objective lenses 7a and 7b is adjusted, FIG. 7 shows a comparative example in which the relationship PA ₁ ≦ PB ₁ and PB _m ≦ PA _n of the spherical aberration correction characteristics shown in FIG. 6 cannot be satisfied. In such a case, FIG. 9A, FIG. 9B, FIG. 9C, or FIG. 10A, FIG. 10B, FIG. It is possible to satisfy the relationship PA ₁ ≦ PB ₁ and PB _m ≦ PA _n of the spherical aberration correction characteristics shown.

FIGS. 9A, 9B, and 9C show the phase optical element 20 in the optical path (position facing the objective lens 7a) when recording / reproducing information on / from the standard A optical disk 8a. An example is shown in which the light beam 2 is arranged and given a phase difference, and the light beam 2 is diverged or converged (however, in FIGS. 9A, 9B, and 9C, the case of diverging). The phase optical element 20 has a spherical surface of the light beam 2 collected by the objective lens 7a as compared with the case where the phase optical element 20 is not arranged in the optical path (FIGS. 8A, 8B, and 8C). It is a lens element or a diffractive element that has an effect of giving an offset to aberration. When the phase optical element 20 is a lens element, the divergence angle of the light beam 2 transmitted through the phase optical element 20 depends on the shape and refractive index of the lens, and when the phase optical element 20 is a diffractive element, the groove shape. Alternatively, the convergence angle can be changed by a predetermined amount. If the divergence angle or the convergence angle is changed by the arrangement of the phase optical element 20, the incident condition to the objective lens can be changed, and the relationship of spherical aberration correction characteristics PA ₁ ≦ PB ₁ and PB The spherical aberration correction characteristic of the standard A can be shifted in the z direction so as to satisfy _m ≦ PA _n .

The optical head device of the first embodiment satisfies the spherical aberration correction characteristic relationship PA ₁ ≦ PB ₁ and PB _m ≦ PA _n shown in FIG. 6 only by the design of the objective lens 7a or the objective lens 7b. I made it. On the other hand, in the optical head device according to the second embodiment, the relationship PA ₁ ≦ PB _{1 of} the spherical aberration correction characteristics, depending on the design of the phase optical element 20 or the combination of the design of the phase optical element 20 and the design of the objective lens. In addition, PB _m ≦ PA _n is satisfied.

10A, 10B, and 10C, the phase optical element 21 and the phase optical element 22 are inserted in front of the objective lens 7a and the objective lens 7b (collimator lens side) of both standards. ing. By adjusting the divergence angle or the convergence angle by the phase optical element 21 and the phase optical element 22 and shifting the spherical aberration correction characteristics in the z direction (+ direction and − direction), respectively, the spherical aberration correction characteristics shown in FIG. The relationship PA ₁ ≦ PB ₁ and PB _m ≦ PA _n are satisfied.

  The phase optical elements 20 and 21 may be integrated with the objective lens 7a and the holder member, and the phase optical element 22 may be integrated with the objective lens 7b and the holder member. In such a case, when the objective lens follows the eccentricity of the data track of the optical disk, it is possible to prevent the occurrence of optical axis deviation.

  Also in an optical head device corresponding to three or more standard optical discs, the same effect can be obtained by providing a similar phase optical element and adjusting the divergence angle or the convergence angle by this phase optical element.

  As described above, also in the optical head device of the second embodiment, as in the first embodiment, the lens driving stroke of the collimator lens by the lens driving means 12 is a lens necessary for spherical aberration correction for the standard A optical disc 8a. As long as the driving stroke is ensured, spherical aberration can be corrected for the information recording layer of both the standard A and standard B optical discs. As a result, the required amount of the lens driving stroke of the collimator lens by the lens driving unit 12 can be reduced, and the lens driving unit 12 can be reduced in weight and the entire optical system can be reduced in size. Further, the spherical aberration of each standard optical disc can be corrected, and stable information recording and reproduction can be performed. Furthermore, the time required for the spherical aberration correction operation can be shortened by reducing the lens driving stroke.

Embodiment 3 FIG.
In general, in an optical disc, not all information recording layers are user data areas. An optical disc has a system information recording area in which system data necessary for system operation is stored, a disc identification data area in which disc identification data is stored, and a recording power used for adjusting the recording power before the recording operation. There is a data area such as an adjustment area that is accessed at the start of the recording / reproducing operation of the optical disk and stores data used for normal operation of the system during recording or reproduction. In many cases, the data area storing data used for normal operation of the system is provided in a specific information recording layer. For this reason, in the case of a multi-layer optical disc, the specific information recording layer has higher necessity and importance of access than other information recording layers. Agility of movement is also required.

For example, it is assumed that the LA ₂ layer (FIG. 4A) of the standard A optical disc 8a and the LB ₂ layer (FIG. 4B) of the standard B optical disc 8b are the specific information recording layers. When a recording / reproducing operation is started with respect to an unknown optical disk, the optical head device firstly includes the specific recording layer in which the system information recording area, the disk identification data area, the recording power adjustment area, and the like exist. It is necessary to access the LA ₂ layer or the LB ₂ layer. Therefore, the position z ₅ of the collimator lens 5, so that the spherical aberration is minimized, the _two-layer LA for the optical disc 8a, it is desirable to match the LB ₂ layers with respect to the optical disk 8b.

In the optical head apparatus according to the third embodiment, like the first or second embodiment, changing the spherical aberration correction characteristic by shifting the collimator lens 5 in the z-direction, the position PA ₂ and the collimator lens of the collimator lens 5 The position PB ₂ is set close to each other (desirably, the position PA ₂ and the position PB ₂ are set as the shortest distance). By doing so, the position of the collimator lens 5 is the position of the collimator lens 5 near the position PA ₂ or the position PB _{2 at} the start of recording / reproduction, regardless of which standard optical disc is the unknown optical disc. Correction can be performed with minimal movement. Therefore, when reading system data in the system information recording area or disk identification data in the disk identification data area, or when reading data in the recording power adjustment area to optimally adjust the recording power, it is possible to move quickly It becomes.

  FIG. 11 shows an optical head device according to Embodiment 3 of the present invention, in which an information recording layer is a single-layer optical disc, an information recording layer is a two-layer optical disc, an information recording layer is another single-layer optical disc, and an information recording layer. FIG. 5 is a diagram showing a position of a collimator lens when a light beam is irradiated on another optical disc having two layers. FIG. 11 shows a plurality of optical discs of different standards. The information recording layer is a two-layer DISC1-DL, the information recording layer is a single-layer DISC1-SL, the information recording layer is a two-layer DISC2-DL, and the information recording layer is a single layer. The spherical aberration correction characteristic of the collimator lens for each optical disc is shown by taking the layer DISC2-SL as an example. In FIG. 11, specific information recording layers having a system information recording area, a disc identification data area, a recording power adjustment area, and the like are L0 (DISC1), SL (DISC1), L1 (DISC2), and SL (DISC2), respectively. It has become.

  In the example shown in FIG. 11, the position of the collimator lens that minimizes spherical aberration in a specific information recording layer in which a system information recording area, a disk identification data area, an optical recording power adjustment area, and the like of an optical disk exist has a plurality of different standards. The optical discs are configured to be close to each other. In the example shown in FIG. 11, as in the first embodiment, the collimator lens moves within the range of movement of the collimator lens with respect to the optical disc of the standard (here, DISC1-DL) that maximizes the distance traveled by the collimator lens. The movement range of the collimator lens with respect to the optical disk is included.

  In the optical head devices of the first to third embodiments, the objective lens 7a and the objective lens 7b corresponding to each standard optical disc are used, and the objective lens used according to the standard of the optical disc to be recorded and reproduced is used. select. However, in the optical head devices of Embodiments 1 to 3, one objective lens may be a lens (compatible type objective lens) corresponding to a plurality of optical disks of different standards. In that case, one objective lens may be configured to support optical disks of all standards, or may include a plurality of objective lenses corresponding to a plurality of standards. In addition, the optical head devices of Embodiments 1 to 3 may include an objective lens corresponding to a plurality of standards and an objective lens corresponding to one standard.

  Similar to the objective lens described in the first embodiment, such an objective lens is, for example, optimized by optimizing the shape of the lens surface (curvature, etc.), the thickness of the lens, or the like, or concentric with the lens surface. In the case of a diffraction type objective lens having a groove structure, the spherical aberration can be optimally designed for a light transmitting layer having a desired thickness by a method such as optimizing the groove depth and groove pitch.

  In the optical head devices according to the first to third embodiments, the spherical aberration correcting lens is the collimator lens 5. However, as a spherical aberration correcting lens, a coupling lens as shown in Patent Document 3 can be used. A relay lens may be used. Also in this case, if the movement range of the spherical aberration correction means with respect to the optical disc of the other standard is included in the movement range of the spherical aberration correction means with respect to the optical disc of the standard having the maximum movement distance of the spherical aberration correction means. It is possible to reduce the driving stroke of the spherical aberration correcting means.

  Further, as in the first embodiment, the optical head device of the third embodiment includes at least one standard optical disc that uses an objective lens having a relatively large numerical aperture of 0.7 or more that requires spherical aberration correction. An optical head device capable of recording / reproducing a plurality of optical discs of different standards. Furthermore, the spherical aberration correction means is configured by lens parts such as a collimator lens, for example, as in the first embodiment.

Embodiment 4 FIG.
FIG. 12 is a diagram schematically showing a configuration of an optical system when recording / reproducing information on the standard A optical disk 8a, which is an optical head device according to the first embodiment of the present invention. FIG. 10 is a diagram schematically showing a configuration of an optical system when recording / reproducing information on / from an optical disc 8c of a standard C different from the standard A in the optical head device according to the fourth embodiment. As shown in FIG. 12 and FIG. 13, the optical head device according to the fourth embodiment is based on a plurality of standards (standard A and standard C) that are defined to be recorded / reproduced with light of different wavelengths for each optical disk standard. Information can be recorded and reproduced on the optical disks 8a and 8c. 12 and 13, the same reference numerals are given to the same or corresponding components as those in FIGS. 1 and 2.

  The optical head device according to the fourth embodiment is an optical head device capable of recording / reproducing information on / from a plurality of optical discs having different standards, as in the first embodiment. The optical head device according to the fourth embodiment can record and reproduce information on a standard optical disc that uses an objective lens having a relatively large numerical aperture of 0.7 or more, which requires spherical aberration correction. Further, the spherical aberration correcting means of the optical head device according to the fourth embodiment is constituted by a lens component such as a collimator lens as in the first embodiment.

The optical head device of the fourth embodiment, a light source 31a that emits light of wavelength lambda _a (primary example is a semiconductor laser), a light source 31c that emits light of wavelength lambda _c (primary example is a semiconductor laser) I have. Further, the optical head device of the fourth embodiment is provided with a polarizing beam splitter 34a for light with a wavelength lambda _a, and a polarizing beam splitter 34c for light with a wavelength lambda _c.

When recording / reproducing information on / from the standard A optical disc 8a, as shown in FIG. 12, the objective lens 7a is placed on the optical path, and the light beam 32a emitted from the light source 31a is irradiated with the light beam. The light beam is divided into a plurality of light beams by the diffraction element 33a, the light beam 32a as a main is incident on the polarization beam splitter 34a with respect to the wavelength lambda _a. In FIG. 12, the other light beams after the division are not shown. The light beam 32a reflected by the polarization beam splitter 34a is transmitted through the polarization beam splitter 34c, and a collimator lens 35 that converts the spread angle (divergence angle or convergence angle) of the light beam 32a. The light beam 32a that is linearly polarized light is circularly polarized. It passes through a quarter-wave plate 36 to be converted into The light beam 32a that has passed through the quarter-wave plate 36 is condensed by the objective lens 7a and irradiated onto the optical disc 8a that conforms to the standard A. The light beam 32a diffracted and reflected by the optical disk 8a is again transmitted through the objective lens 7a and converted into a substantially parallel light beam, then transmitted through the quarter-wave plate 36 and the collimator lens 35, and further, the polarization beam splitter 34c. Then, the light passes through the polarization beam splitter 34 c and is received by the photodetector 41 through the cylindrical lens 39 and the sensor lens 40. The photodetector 41 has a plurality of divided light receiving surfaces, and converts the light amount of the light beam 32a received by each light receiving surface into an electrical signal.

When recording / reproducing information on / from the standard C optical disc 8c, as shown in FIG. 13, the objective lens 7c is placed on the optical path, and the light beam 32c emitted from the light source 31c is irradiated with the light beam. The light beam is divided into a plurality of light beams by the diffraction element 33c, the light beam 32c as a main is incident on the polarization beam splitter 34c with respect to the wavelength lambda _c. In FIG. 13, the other light beams after the division are not shown. The light beam 32c reflected by the polarization beam splitter 34c is a collimator lens 35 that converts the spread angle (divergence angle or convergence angle) of the light beam 32c, and a quarter wavelength that converts the linearly polarized light beam 32c into circularly polarized light. Pass through plate 36. The light beam 32a that has passed through the quarter-wave plate 36 is condensed by the objective lens 7a and irradiated onto the optical disc 8a that conforms to the standard A. The light beam 32a diffracted and reflected by the optical disk 8a is again transmitted through the objective lens 7a and converted into a substantially parallel light beam, then transmitted through the quarter-wave plate 36 and the collimator lens 35, and further, the polarization beam splitter 34c. Then, the light passes through the polarization beam splitter 34 c and is received by the photodetector 41 through the cylindrical lens 39 and the sensor lens 40. The photodetector 41 has a plurality of divided light receiving surfaces, and converts the light amount of the light beam 32a received by each light receiving surface into an electrical signal.

  As for the light detector 41, as in the light detector 11 according to the first embodiment of the present invention, the defocus from the information recording layer of the optical disk 8a and the optical disk 8c is based on the reflected light from the optical disk 8a and the optical disk 8c. According to each detection method so as to be able to detect the amount, the track deviation amount of the focused spot from the information track in which the recording information is arranged substantially concentrically or spirally on the optical disc 8a and the optical disc 8c, and the reproduction signal of the recording information. A divided light receiving surface is formed.

  Furthermore, another light receiving surface for detecting the tilt angle of the optical disc 8a and the optical disc 8c and the spherical aberration amount of the focused spot may be formed, and a detection optical element for distributing the light beam to these light receiving surfaces is provided. It may be.

  The collimator lens (spherical aberration correction lens) 35 includes a lens driving unit 12 and moves the collimator lens 35 in the optical axis direction by a driving force generated by an electromagnetic force or a motor.

  FIG. 14 is a block diagram schematically showing a configuration of an optical disk device in which the optical head device according to the fourth embodiment is mounted. As shown in FIG. 14, the optical disc apparatus according to the fourth embodiment is, for example, an optical disc recording / reproducing apparatus, and includes a recording / reproducing means 17 including the configuration of an optical head device, and a disc discriminating means 101 for discriminating the type of optical disc. And control means 102. The recording / reproducing means 17 includes light sources 31a and 31c, a light detector 41, a lens driving means 12, an objective lens switching means 14, and an objective lens that can move the objective lens in the optical axis direction and the radial direction of the optical disc. And an actuator 15 (not shown in FIGS. 12 and 13). The control means 102 performs defocus detection, tracking error detection, spherical aberration detection, and reproduction signal detection based on the detection signal of the light detector 41. The disc discriminating means 101 discriminates the type of the optical disc by selecting the amplitude of the defocus detection signal and the count number in each recording layer of the multilayer recording disc as the characteristics of the optical disc. The control unit 102 controls the objective lens switching unit 14 based on the detection signal from the disc determination unit 101. The control unit 102 also detects the lens driving unit 12 and the objective lens actuator 15 based on the detection signals of defocus detection, tracking error detection, spherical aberration detection, and reproduction signal detection, and the detection signal of the disc discrimination unit 101. To control.

  FIG. 15A is a diagram showing the relationship between the position of the collimator lens and the spherical aberration SA when each information recording layer of the standard C optical disc is irradiated with a light beam by the optical head device according to the fourth embodiment. FIG. 15B shows the position of the collimator lens when the information recording layer of the standard A optical disk is irradiated with a light beam by the optical head device according to the fourth embodiment, and the standard by the optical head device according to the fourth embodiment. It is a figure which shows the position of the collimating lens when each information recording layer of the optical disk of C is irradiated with a light beam. In FIG. 15A, the horizontal axis (movement position z of the collimator lens) is the distance from the reference light source, and here is the distance from the light source 31a that emits light of the wavelength used in the standard A. With respect to the movement of the collimator lens 35, the spherical aberration in each information recording layer has a substantially V-shaped or U-shaped characteristic. The basic concept of this characteristic is the same as in FIGS. 5A and 5B described in the first embodiment.

The wavelength λ _{c of the} light beam used for the standard C optical disc 8c is different from the wavelength λ _{a of the} light beam used for the standard A and standard B optical discs 8a and 8b. Further, when the wavelength of the light beam is different, the refractive power of the lens on which the light beam is incident is different. Therefore, the focal length of the collimator lens 35 with respect to the light beam having the wavelength lambda _c is different from the focal length of the collimator lens 35 with respect to the light beam of wavelength lambda _a. For example, if the collimator lens 35 is a normal refractive lens, the wavelength λ _{c of the} light beam used for the standard C optical disc 8c is the wavelength λ _{c of the} light beam used for the standard A and standard B optical discs 8a and 8b. If it is longer than _a, the focal length of the collimator lens 35 is longer for the light beam used for the standard C optical disc 8c.

The optical head device shown in FIG. 12 and FIG. 13 receives reflected light from each optical disc with a single light detector 41 for light beams having different wavelengths (light reception of light beams of each wavelength of the light detector). The optical path length from each light source (semiconductor laser) 31a, 31c to the collimator lens 35 and the optical path length from the collimator lens 35 to the light detector 41 need to be equal. is there. Therefore, for example, when the wavelength λ _{c of the} light beam used for the standard C optical disc 8c is longer than the wavelength λ _{a of the} light beam used for the standard A optical disc 8a, the collimator lens as a whole in the standard C 5 must be shifted in the direction of increasing the position z ₃₅ (the shift amount in the z direction is assumed to be zc).

In the optical head device according to the fourth embodiment, in consideration of the shift of the collimator lens 35 due to the difference in wavelength, the collimator lens moves within the range of movement of the collimator lens with respect to the standard optical disc in which the movement distance of the collimator lens is maximum. The objective lens is designed so as to include the range of movement of the collimator lens with respect to optical discs of all the standards. That is, as shown in FIG. 15 (b), when the position of the collimator lens 35 and the _{z 35} is the k (k from LC ₁ layer is a first information recording layer of the optical disc 8c standard C is In order to perform spherical aberration correction on all the information recording layers up to the LC _k layer, which is a positive integer information recording layer, the collimator lens 35 requires a lens driving stroke in the range of PC ₁ ≤z ₃₅ ≤PC _k. It is. Position PC ₁ and PC _k collimator lens 35, considering also differences in the focal length due to a difference between the wavelength lambda _a and lambda _c, it is necessary to a value shifted by zc in the z direction. By this shift, the position PC ₁ of the collimator lens 35 changes to the position PC ₁ ′, and the position PC _k of the collimator lens 35 changes to the position PC _k ′.

When the moving distance of the collimator lens 35 with respect to the standard C is the maximum, as shown in FIG. 15B, the collimator with respect to the optical disk of another standard is within this range of PC ₁ ′ ≦ z ₃₅ ≦ PC _k ′. The lens movement range (PA ₁ ≦ z ₃₅ ≦ PA _{n in} FIG. 15B) is included. When the moving distance of the collimator lens with respect to another standard is maximized, this range of PC ₁ ′ ≦ z ₃₅ ≦ PC _k ′ is included in the moving range with respect to the optical disk of another standard with the maximum moving distance. To.

  As described in the first embodiment, the method for optimizing the spherical aberration by shifting the spherical aberration correction characteristic in the z direction, for example, optimizing the lens surface shape (curvature, etc.) and the lens thickness. There is a way to do it. In addition, for the method of optimally designing spherical aberration by shifting the spherical aberration correction characteristics in the z direction, the groove depth and groove pitch are optimal for diffractive objective lenses with a concentric groove structure on the lens surface. There are also methods such as Similarly to the second embodiment, the diffractive optical elements 20 to 22 can be used for optimal design with the same configuration.

  In the fourth embodiment, two types of standards A and C have been described as examples. However, the present invention is also applicable to cases where one or more standards other than these are added.

FIG. 16 is a diagram schematically showing a configuration of another optical system of the optical head device according to the fourth embodiment. In FIG. 16, the same reference numerals are given to the same or corresponding components as those shown in FIGS. 12 and 13. The optical head device shown in FIG. 16 is a diagram showing the configuration of an optical head apparatus capable of recording and reproducing with respect to an optical disk 8d standard D using a light beam of wavelength lambda _d. The optical head device shown in FIG. 16 includes a light source (semiconductor laser) 31d that emits a light beam 32d, a diffraction grating 33d, a polarization beam splitter 34d, and an objective lens 7d. Different from the device.

In the optical head device shown in FIG. 16, the relationship between the lens driving strokes of the lens driving means 12 for driving the collimator lens 35 for each information recording layer of each standard optical disc is the same as that of the optical head device in FIG. In addition, the movement range of the collimator lens with respect to the optical disc of the other standard is included in the movement range of the collimator lens with respect to the optical disc of the standard in which the movement distance of the collimator lens 35 is the maximum. Here, the position z ₃₅ of the collimator lens with respect to the optical disc of each standard is a distance from the reference light source, as in FIG.

  FIG. 17 is a diagram schematically showing a configuration of another optical system of the optical head device according to the fourth embodiment. In FIG. 17, the same or corresponding elements as those shown in FIG. FIG. 17 is a configuration example using a light source 310 in which two light sources 31c, 31d are integrated into one package among the light sources 31a, 31c, 31d of FIG. According to the configuration example of FIG. 17, the number of parts is small compared to the configuration example of FIG. 16, and the configuration is small and advantageous in terms of cost.

  FIG. 18 is a diagram schematically showing a configuration of another optical system of the optical head device according to the fourth embodiment. In FIG. 17, the same or corresponding elements as those shown in FIG. FIG. 18 is a configuration example using a light source 311 in which three light sources 31a, 31c, and 31d are integrated into one package among the light sources 31a, 31c, and 31d in FIG. The configuration example of FIG. 18 has a smaller number of parts than the configuration example of FIG. 16, is small, and is advantageous in terms of cost.

  In the fourth embodiment, similarly to the third embodiment, the system information recording area in which system data necessary for system operation is stored and the recording power used for recording power adjustment before the recording operation are stored. The position of the collimator lens that minimizes the spherical aberration in a specific recording layer having an adjustment region or the like may be configured to be close between a plurality of optical disks of different standards. In such a configuration, the same effect as that of the optical head device of Embodiment 3 can be obtained.

  In the fourth embodiment, the objective lens corresponding to each standard is used individually and the objective lens to be used is selected according to the standard of the optical disk to be used. A lens (compatible objective lens) compatible with a standard optical disc may be used. In that case, one objective lens may have a configuration corresponding to all the standards, or may include a plurality of objective lenses corresponding to a plurality of standards. Moreover, an objective lens corresponding to a plurality of standards and an objective lens corresponding to one standard may be provided. Even in such an objective lens, as described in the first embodiment, for example, by optimizing the shape (curvature, etc.) of the lens surface, the thickness of the lens, etc., or concentrically on the lens surface In the case of a diffraction type objective lens having a groove structure, the spherical aberration can be optimally designed for a light transmission layer having an arbitrary thickness by a method such as optimizing the groove depth and groove pitch.

  In the fourth embodiment, the spherical aberration correction unit is the collimator lens 35, but a coupling lens or a relay lens may be used as the spherical aberration correction unit. Also in this case, if the movement range of the spherical aberration correction means with respect to the optical disc of the other standard is included in the movement range of the spherical aberration correction means with respect to the optical disc of the standard having the maximum movement distance of the spherical aberration correction means. It is possible to reduce the driving stroke.

Embodiment 5 FIG.
There are two types of optical discs: a single layer (SL) disc with one information recording layer and a dual layer (DL) disc having an information recording layer L0 and an information recording layer L1. The optical head device of the fifth embodiment is an optical head device capable of recording / reproducing information on all these information recording layers. In the following, an optical head device applicable to two standard optical discs, standard A and standard B, will be described. However, the types of optical disk standards to which the optical head device of the fifth embodiment can be applied may be three standards or more standards, and the number of standards that can be applied is not particularly limited. In the optical head device according to the fifth embodiment, the wavelength of the light beam applied to the optical disk is not particularly limited. As in the case of the first to fourth embodiments, the optical head device of the fifth embodiment has a spherical aberration correction unit common on the optical path when information is recorded / reproduced on / from a plurality of optical discs of different standards. For example, a collimator lens is arranged.

  The configuration of the optical head device according to the fifth embodiment is shown in FIGS. 1, 2, 9A and 10B, 10A and 10B, FIGS. 12, 13, 16, 17, This is the same as one of the configurations of the optical head devices of Embodiments 1 to 4 shown in FIG. In the optical head device according to the fifth embodiment, the optical components in which the mutual positional relationship is important are a semiconductor laser, a collimator lens, an objective lens, and an optical disc as light sources. The explanation is centered.

First, the standard and the optical component will be described. As described here, the numerical aperture NA _a of an objective lens used in the optical disk of the standard A 0.85, the numerical aperture NA _b of the objective lens used in the optical disk of the standard B 0.65. That is, in the fifth embodiment, the numerical aperture NA _a is larger than the numerical aperture NA _b , the numerical aperture NA _a is 0.7 or more, and the numerical aperture NA _b is 0.65 or less.

  The light source and spherical aberration correcting means (for example, a collimator lens) are commonly used for the standard A optical disc and the standard B optical disc. The collimator lens is driven in the direction of the optical axis by the driving means so as to optimize the spherical aberration of the light condensed on the optical disc in accordance with the type of the optical disc.

  In the fifth embodiment, a case where a collimator lens is employed as the spherical aberration correction unit will be described, but the spherical aberration correction unit is not limited to the collimator lens. As the spherical aberration correction means, a liquid crystal element, a coupling lens, or a relay lens can be used. However, when the spherical aberration correcting means is composed of a liquid crystal element, if there is a deviation in the positional relationship between the electrode pattern provided on the transparent electrode to give the electric field distribution to the liquid crystal and the entrance pupil of the objective lens, the wavefront aberration This causes the problem of deterioration. Therefore, when the spherical aberration correcting means is composed of a liquid crystal element, the positional relationship adjustment accuracy is on the order of several microns, which increases the manufacturing cost from the viewpoint of assembly. In order to prevent an increase in cost, it is possible to integrate the liquid crystal element and the objective lens so that the positional relationship is not shifted. However, in addition to increasing the weight of the movable part, a power supply line to the transparent electrode of the liquid crystal element is required. , Performance and manufacturing problems occur.

  Further, in an optical head device that records and reproduces information with respect to an optical disk with a relatively small standard numerical aperture of 0.65, such as a DVD, a spherical surface is used as much as possible in order to ensure a recording characteristic margin. There are devices to which a spherical aberration correction liquid crystal element is applied in order to reduce the aberration. In such an optical head device, the spherical aberration correcting liquid crystal element operates without any problem in a configuration in which the positional relationship with the objective lens is shifted during operation by being disposed in the fixed portion. However, when the numerical aperture of at least one objective lens is as large as 0.7 or more as in the optical head device of the present invention, the spherical aberration correcting liquid crystal element is disposed in the fixed portion. Unlike the head device, there arises a problem that the wavefront aberration is remarkably deteriorated due to the occurrence of coma aberration caused by the positional relationship with the objective lens deviating. In view of the above, it is more advantageous in terms of cost and performance to configure the spherical aberration correcting means with lens parts such as a collimator lens. For this reason, in the optical head device of the fifth embodiment, a case where a collimator lens is employed as the spherical aberration correction means will be described.

  Next, optical discs of each standard will be described. As described above, there are two-layer discs (DL discs) and single-layer discs (SL discs) in the optical discs of the respective standards. As standard A optical discs, there are two types of DL discs with two information recording layers (hereinafter referred to as “DISC1-DL”) and SL discs with a single information recording layer (hereinafter referred to as “DISC1-SL”). is there. In addition, as a standard B optical disc, the information recording layer is a two-layer DL disc (hereinafter referred to as “DISC2-DL”) and the information recording layer is a single-layer SL disc (hereinafter referred to as “DISC2-SL”). There is.

  The thickness of the transparent layer from the disc surface of the SL disc to the information recording layer and the thickness of the transparent layer from the disc surface of the DL disc to the information recording layer are different for each standard. As shown in FIG. 19 to be described later, the thickness of the transparent layer from the disc surface (z = 0) to the information recording layer SL (DISC1) in the standard A SL disc is the disc surface (z = 0) to the thickness of the transparent layer from the information recording layer L0 (DISC1). Further, the thickness of the transparent layer from the disk surface (z = 0) to the information recording layer SL (DISC2) in the standard B SL disk is the same as the information recording layer L0 (z = 0) from the disk surface (z = 0) in the standard B DL disk. DISC2) is set approximately between the thickness of the transparent layer up to DISC2) and the thickness of the transparent layer from the disc surface (z = 0) to the information recording layer L1 (DISC2) in the standard B DL disc. For this reason, the spherical aberration caused by the difference in thickness of the transparent layer in the information recording layer L0 (DISC2) and the information recording layer L1 (DISC2) in the standard B DL disc can be reduced as much as possible, and recording / reproduction can be performed without correcting the spherical aberration. It is a possible optical disk system.

  As described above, some optical disc standards enable recording and reproduction of DL discs without correcting spherical aberration. However, in the L0 layer and the L1 layer that are not corrected for spherical aberration, at least spherical aberration remains, so that the optimum recording / reproducing characteristics are not obtained. It is necessary to correct spherical aberration for the recording layer. In particular, in an optical head device configured by a compatible optical system and using a common spherical aberration correction means, such as the optical head device of the present invention, it is desired to perform spherical aberration correction for both standards.

  The characteristics of the optical head device according to the fifth embodiment will be described. FIG. 19 is a diagram showing the spherical aberration correction characteristics of the collimator lens for various optical disks of the optical head device of the fifth embodiment, similar to FIG. 11 described in the third embodiment.

  As shown in FIG. 19, the optical head device of the fifth embodiment is configured such that the driving stroke of the other standard B falls within the driving stroke range of the standard A where the driving stroke of the spherical aberration correcting means is large. ing. The information recording layer under the condition (PLI) in which a parallel light beam is incident on the objective lens so that the driving stroke of the other standard B falls within the driving stroke range of the standard A where the driving stroke of the spherical aberration correcting means is large. An objective lens for a standard A optical disc capable of condensing light is mounted at any position between L0 (DISC1) and the information recording layer L1 (DISC1). That is, when the light is condensed on the information recording layer SL (DISC1) of the standard A SL disk (or the information recording layer L0 (DISC1) of the standard A DL disk), the incident light beam to the objective lens is a non-parallel light beam. And when the light is condensed on the SL layer of the SL disk of the standard B, the incident light beam to the objective lens is a parallel light beam. By constructing a compatible optical system by combining such objective lenses, the driving stroke of the spherical aberration correcting means used in common in both standards can be reduced.

  Hereinafter, for comparison, a comparative example in which the driving stroke of the spherical aberration correcting unit is set large will be described.

  FIG. 20 shows an optical disc device having a single information recording layer, an optical disc DISC1-DL having two information recording layers, another optical disc DISC2-SL having a single information recording layer, and an optical head device of a comparative example. It is a figure which shows the position of a collimator lens when an information recording layer irradiates a light beam to the other two optical disks DISC1-DL. FIG. 20 shows a collimator lens in a case where the standard A objective lens has a characteristic of condensing light on SL (DISC1) which is an SL layer and DL (DISC1) which is an L0 layer under parallel light beam incidence conditions (PLI). The spherical aberration correction characteristic is shown. A driving stroke of the collimator lens when correcting spherical aberration in the information recording layer L0 (DISC1) (or information recording layer SL (DISC1)) and the information recording layer L1 (DISC1) of the optical disc of standard A is defined as La. Also, the position of the collimator lens when spherical aberration is corrected in the information recording layer L0 (DISC1) (or information recording layer SL (DISC1)) of the standard A optical disc, and the information recording layer L0 (DISC2 of the standard B optical disc). ) Or the distance difference Lab from the position of the collimator lens when spherical aberration is corrected by the information recording layer L1 (DISC2). At this time, the total driving stroke in the standard A and the standard B is necessarily larger than the driving stroke La considered only in the standard A. Here, FIG. 20 shows a case where the wavelengths of light used in the standard A and the standard B are different, and the SL layer of the SL disk of the standard A in FIG. 20 (or the L0 layer of the DL disk of the standard A). The distance difference Lb0 between the position of the collimator lens when the spherical aberration is corrected in (1) and the position of the collimator lens when the spherical aberration is corrected by the SL layer of the standard B SL disk is the focal point of the collimator lens due to the wavelength difference used. It shows how it occurs as a difference in distance.

  Therefore, if the wavelengths of light used in the standards A and B are the same, the distance difference Lb0 in FIG. 20 becomes zero, and the SL layer of the SL disk of the standard B and the L0 layer and L1 of the DL disk of the standard B The position of the collimator lens for correcting the spherical aberration of the layer may be considered in a state shifted to the left in FIG. 20 by Lb0. As a result, the total drive stroke TL in the standards A and B is as follows. It becomes larger than the drive stroke La considered only by the standard A. Similarly to FIG. 20, FIG. 19 described above shows a case where the wavelengths of light used in the standards A and B are different, and the same concept as FIG. 20 is used.

  On the other hand, the optical head device of the fifth embodiment, as shown in FIG. 19, focuses light on the SL layer of the standard A SL disk (or the L0 layer of the standard A DL disk). Since the incident light beam to the standard A objective lens is incident as a non-parallel light beam, an increase in the driving stroke of the spherical aberration correcting unit can be suppressed, and the size of the spherical aberration correcting unit can be reduced. The time required for switching can be shortened.

  Further, when condensing light on the SL layer of the standard A SL disk (or the L0 layer of the standard A DL disk), the incident light to the objective lens is made incident as a non-parallel light beam, and the standard B SL disk. When condensing light on the SL layer, a compatible objective lens of standard A and standard B that allows the incident light beam to be incident on the objective lens as a parallel light beam may be used, and the driving stroke of the spherical aberration correcting means is the same as described above. The optical system of the entire optical head device can be reduced in size.

  In the above description, with respect to the standard B, the incident light to the objective lens is a parallel light flux when condensing on the SL layer of the SL disk, but the present invention is not limited to this. A non-parallel light beam may be used. In this case, the spread angles of the non-parallel light beams when the light is condensed on the standard A and standard B SL layers must be different. However, in general, when a non-parallel light beam is incident on an objective lens, image height aberration occurs when the objective lens is shifted in a direction perpendicular to the optical axis. It is desirable and advantageous from the viewpoint of securing a performance margin.

  Further, in order to make a difference in the divergence angle of the non-parallel light beam when the light is condensed on the SL layer of the standard A SL disk and the SL layer of the standard B SL disk, A phase optical element that changes the divergence angle or the convergence angle of the light beam described in the second embodiment may be inserted between the spherical aberration and the spherical aberration. Further, the phase optical element may be switched according to the standard.

  Furthermore, the phase optical element may be configured to be driven integrally with a corresponding standard objective lens.

  In the above description, the optical disc apparatus capable of recording and reproducing information with respect to the optical discs of the two types of standards A and B has been described. However, the present invention is not limited to this, and the standard A In addition to the standard B, it may be an optical disk apparatus capable of recording / reproducing information on a standard C optical disk.

  In the fifth embodiment, similarly to the third embodiment, the system information recording area in which system data necessary for system operation is stored and the recording power used for recording power adjustment before the recording operation are stored. The position of a collimator lens (spherical aberration correction lens) that minimizes spherical aberration in a specific recording layer (here, L0 layer and SL layer) having an adjustment area or the like is close between a plurality of optical discs of different standards. If it is configured, it is possible to obtain the same effect as in the third embodiment. That is, it is set so that L0 (DISC2) and L1 (DISC2) of the other standard B are located in a range closer to L0 (DISC1) than an intermediate position between L0 (DISC1) and L1 (DISC1) in FIG. Thus, the same effect as in the third embodiment can be obtained.

Claims (14)

An optical head device capable of recording and / or reproducing information on a plurality of optical discs of different standards,
A light source that emits light of a predetermined wavelength;
An objective lens for condensing the light from the light source on the optical disc;
Commonly used for a plurality of optical discs of different standards, installed on the optical path of the light emitted from the light source, and moved in the optical axis direction to change the divergence angle or convergence angle of the light emitted from the light source. A spherical aberration correction means for correcting the spherical aberration in the information recording layer of the optical disc,
Drive means for moving the spherical aberration correction means in the optical axis direction,
Among the plurality of different standard optical discs, the movement of the spherical aberration correction unit with respect to another standard optical disc is within the movement range of the spherical aberration correction unit with respect to the standard optical disc with the maximum movement distance of the spherical aberration correction unit. An optical head device, wherein the objective lens and the spherical aberration correcting means are configured so as to satisfy a movement range condition of the spherical aberration correcting means that a range is included.   By adjusting at least one of the shape of the objective lens, the refractive index of the objective lens, and the diffractive structure of the objective lens, the moving lens satisfies the moving range condition of the spherical aberration correcting means. The optical head device according to claim 1, wherein the optical head device is characterized in that:   2. The optical head device according to claim 1, wherein the spherical aberration correcting means is any one of a collimator lens, a coupling lens, a relay lens, and a liquid crystal element. A plurality of the objective lenses;
Objective lens switching means for selectively placing any one of the plurality of objective lenses on the optical path;
The optical head device according to claim 1, wherein a numerical aperture of at least one of the plurality of objective lenses is 0.7 or more.   2. The optical head device according to claim 1, wherein the objective lens used for the plurality of optical disks of different standards includes an objective lens corresponding to the plurality of optical disks of different standards.   2. The optical head device according to claim 1, further comprising means for changing a divergence angle or a convergence angle of transmitted light that is disposed on an optical axis of light emitted from the light source. The optical discs of the plurality of different standards are
A first standard optical disc;
A second standard optical disc,
The optical disc of the first standard is
A single-layer disc of the first standard in which the information recording layer is a single layer;
Including a first standard dual-layer disc having two information recording layers,
The first standard double-layer disc is:
The transparent layer depth from the optical disc surface to the information recording layer is the same as the transparent layer depth from the single-layer disc surface to the information recording layer, and the system information recording area or disc identification data area or recording power adjustment of the optical disc Having two information recording layers including a specific information recording layer in which the area exists,
The optical disc of the second standard is
A single-layer disc of the second standard in which the information recording layer is a single layer;
Including a second-layer disc of the second standard having two information recording layers,
The dual-layer disc of the second standard is
A first information recording layer in which a transparent layer depth from the surface of the optical disc to the information recording layer is set to a transparent layer depth smaller than a transparent layer depth from the surface of the single-layer disc to the information recording layer;
A second information recording layer set to a transparent layer depth larger than the transparent layer depth from the surface of the single-layer disc to the information recording layer,
Recording specific information in which the system information recording area or the disc identification data area or the recording power adjustment area of the optical disc exists in either the first information recording layer or the second information recording layer,
Information recording / recording on the single-layer disc of the second standard optical disc and the divergence angle or convergence angle of the light incident on the objective lens when recording / reproducing information on the single-layer disc of the first standard optical disc 2. The optical head device according to claim 1, wherein a divergence angle or a convergence angle of a light beam incident on the objective lens during reproduction is different.   The numerical aperture of the objective lens for recording / reproducing information with respect to the optical disc of the first standard is larger than the numerical aperture of the objective lens for recording / reproducing information with respect to the optical disc of the second standard, and the first standard. The light incident on the objective lens when recording / reproducing the single-layer disk of the optical disk is non-parallel light beam and incident on the objective lens when recording / reproducing the single-layer disk of the second standard optical disk 8. The optical head device according to claim 7, wherein the light to be emitted is parallel light flux. Each of the plurality of different standard optical disks has an information recording layer including a specific information recording layer in which a system information recording area or a disk identification data area or a recording power adjustment area of the optical disk exists,
The positions of the spherical aberration correcting means that minimize the spherical aberration in the information recording layer including the specific information recording layer in which the system information recording area, the disc identification data area, or the recording power adjustment area of the optical disc is present are different from each other. The optical head device according to claim 1, wherein the optical head device is configured to be close to a standard between optical discs. The light source emits a light beam of a single wavelength;
The optical head device according to claim 1, wherein the wavelengths of the light beams used according to the standard of the optical disc are the same. The light source emits light beams of different wavelengths;
The optical head device according to claim 1, wherein the wavelength of the light beam used differs according to the standard of the optical disc.   2. The optical head device according to claim 1, wherein the spherical aberration correcting unit corrects spherical aberration in each information recording layer of the optical disc for an optical disc having a plurality of information recording layers. It has a photodetector that receives the return light from optical discs with different wavelengths and generates a reproduction signal,
The range of movement of the spherical aberration correcting means for a plurality of optical discs of different standards having different wavelengths is set in consideration of the optical path difference due to the spherical aberration correcting means caused by the difference in wavelength. 2. An optical head device according to 1. A recording / reproducing means for recording and / or reproducing information with respect to an optical disc, comprising the optical head device according to claim 4;
Disc discriminating means for detecting the type of the optical disc;
Control for selecting any of the plurality of objective lenses of the optical head device according to the type of the optical disc detected by the disc discriminating means and moving it on the optical path by the objective lens switching means, and An optical disc apparatus comprising: control means for performing control for moving the spherical aberration correcting means of the optical head device by the driving means.

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