JP2006252614A - Optical pickup device and optical disk driving device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device capable of securing compatibility among various optical disks of different standards with simple constitution, and an optical disk driving device. <P>SOLUTION: The optical pickup device for converging a luminous flux from a light source on plural kinds of optical disk recording surfaces different in substrate thickness by using the common light source and a common objective lens to perform at least one or more operations of recording, reproducing and erasing is provided with an aperture changing means for changing an effective numerical aperture of the objective lens corresponding to the kind of an optical disk, and a luminous flux changing means for changing the convergence/divergence state of a luminous flux applied to the objective lens corresponding to the kind of an optical disk. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup apparatus and an optical disk drive apparatus that perform at least one of recording, reproduction, and erasing operations on a plurality of types of optical disks having different substrate thicknesses.

  The demand for higher recording density and larger capacity for optical disc systems has been increasing in recent years. In order to improve the recording density, it is effective to shorten the wavelength of the light used for the optical pickup and reduce the spot diameter of the collected light by increasing the numerical aperture NA of the objective lens used. . For example, an optical disc system having a wavelength of 405 nm and a numerical aperture NA of 0.85 has been put into practical use in contrast to the Blu-ray standard, while the DVD standard objective lens has a wavelength of 660 nm and a numerical aperture NA of 0.65. In the Blu-ray standard, the disc substrate thickness is made as thin as 0.1 mm so as not to deteriorate the tilt characteristic.

  On the other hand, the HD-DVD standard has been proposed in order to easily ensure the compatibility performance with the conventional CD standard and DVD standard. In the HD-DVD standard, backward compatibility is ensured by increasing the recording density at a wavelength of 405 nm and setting the substrate thickness to 0.6 mm, the same as DVD. That is, under the conditions of a wavelength of 780 nm and a substrate thickness of 1.2 mm for CD, and a wavelength of 660 nm and a substrate thickness of 0.6 mm for DVD, each was further subdivided into more detailed standards such as DVD + RW and DVD-RW. Therefore, a certain degree of compatibility was ensured. However, when the Blu-ray standard and the HD-DVD standard are compatible in the next generation, the wavelength 405 nm is the same, but the substrate thickness and numerical aperture are greatly different. There was concern that it would be difficult to ensure compatibility between the next generation.

  As one of the causes of the rapid increase in sales of optical disc drive products in recent years, the so-called multi-drive that is compatible with all the subdivided standards of DVD can be cited, and in the next generation, compatibility will be the first on the user side. Development to ensure is important.

  Patent document 1 is mentioned as a prior art with respect to the above subject. In this patent document 1, the spherical aberration due to the difference in substrate thickness is corrected by changing the numerical aperture for two types of optical disks having different substrate thicknesses by changing the distance between the two stops and the two-group objective lens. . The optical scanning device of Patent Document 1 can scan two different types of optical record carriers (1, 25) that require scanning beams (15) having different numerical apertures. The device has two stops (33, 32) at different positions along the optical axis of the path through which the radiation beam passes for the two types of discs. The first aperture (33) limits the numerical aperture of the radiation beam when the first type of record carrier (1) is scanned. The second stop (32) limits the numerical aperture of the radiation beam when the second type of record carrier (25) is scanned.

  In addition, in Patent Document 2, the numerical aperture is changed for two types of optical disks having different substrate thicknesses by using two light sources and polarizing filters having different polarization directions. That is, optical signals for reproducing signals by irradiating the signal recording surfaces 51a and 52a of the optical discs 51 and 52 with laser light through the objective lens 24 and guiding the laser light reflected by the signal recording surfaces 51a and 52a to the photodetector 40. Type playback device. For each of a plurality of types of optical disks 51 and 52 having different substrate thicknesses, the effective numerical aperture of the objective lens 24 is set in accordance with the thickness of the substrate so that the laser spot can be focused on the signal recording surface of the optical disk. An optical reproducing apparatus that adjusts an effective numerical aperture by switching so that light is transmitted without being stopped by the polarizing filter 31 or by the polarizing filter 31. Furthermore, an apparatus is disclosed in which the focal length is changed between the inner periphery and the outer periphery of the objective lens.

  By the way, in the disclosed technique of the above-mentioned Patent Document 1, a.) The accuracy of changing the distance between the two-group objective lenses is severe and large aberrations are likely to occur. B.) The working distance between the objective lens and the disk surface cannot be secured. c.) There is a disadvantage that the tilt characteristic of the objective lens is likely to be deteriorated because the position of one aperture (32) is largely deviated from the pupil position of the objective lens. Further, the disclosed technique of Patent Document 2 has the following disadvantages: a.) A plurality of light sources are required; b.) Spherical aberration due to the difference in substrate thickness cannot be corrected when the numerical aperture is increased. is there.

  In addition, as another related to the present invention, there is a liquid crystal lens (optical path changing means) used for realizing an optical pickup capable of signal reproduction requiring a high transfer rate (see, for example, Patent Document 3). In the optical pickup described in Patent Document 3, the liquid crystal lens 15 is first linearly polarized light that is linearly polarized light having a first polarization plane or linearly polarized light that has a second polarization plane orthogonal to the first polarization plane. Either one of the second linearly polarized light is transmitted as it is, the other linearly polarized light is converged or diffused, and the condensing means records either the first linearly polarized light or the second linearly polarized light in the first recording. Focusing on the surface and condensing the other on the second recording surface, it is possible to perform focus servo control and tracking servo control for the two readout beams, and to accurately record information It is possible to trace and read two pieces of recorded information at the same time, and it is possible to read information at twice the speed of the conventional drive system using the same drive system. For example, signal reproduction requiring a high transfer rate such as HDTV is possible.

JP 2002-533860 A JP 09-50647 A JP-A-11-195240

  Accordingly, the present invention has been proposed in view of the above-described conventional situation, and provides an optical pickup device and an optical disc drive device that ensure compatibility with various configurations of various optical discs with a simple configuration. The purpose is to do.

  In the optical pickup device according to the first aspect of the present invention, a light source from a light source is condensed and recorded and reproduced on a plurality of types of optical disk recording surfaces having different substrate thicknesses using a common light source and a common objective lens. In an optical pickup device that performs at least one erasing operation, aperture changing means for changing the effective numerical aperture of the objective lens in accordance with the type of the optical disc, and incidence on the objective lens in accordance with the type of the optical disc And a light beam changing means for changing a convergent and divergent state of the light beam.

  According to a second aspect of the present invention, in the optical pickup device according to the first aspect, the types of the optical disc include a substrate thickness of 0.1 mm, a numerical aperture of 0.85 Blu-ray standard disc, a substrate thickness of 0.6 mm, An HD-DVD standard disc having a numerical aperture of 0.65 is included.

  According to a third aspect of the present invention, in the optical pickup device according to the first or second aspect, the aperture changing means includes a polarizing filter that changes a diameter of a transmitted light beam according to a polarization direction of the incident light beam, and an incident light beam. It is characterized by comprising a λ / 2 wavelength plate that rotates the polarization direction by 90 degrees.

  According to a fourth aspect of the present invention, in the optical pickup device according to the third aspect, the λ / 2 wavelength plate is a liquid crystal phase plate capable of rotating or not rotating the polarization direction of the incident light beam by 90 degrees depending on driving conditions. It is characterized by that.

  According to a fifth aspect of the present invention, in the optical pickup device according to the first or second aspect, the aperture changing means includes a polarization hologram in which the diameter of the transmitted light beam changes depending on the polarization direction of the incident light beam, and the incident light beam. It is characterized by comprising a λ / 2 wavelength plate that rotates the polarization direction by 90 degrees.

  According to a sixth aspect of the present invention, in the optical pickup device according to the fifth aspect, the λ / 2 wavelength plate is a liquid crystal phase plate capable of rotating or not rotating the polarization direction of the incident light beam by 90 degrees depending on driving conditions. It is characterized by that.

  According to a seventh aspect of the present invention, in the optical pickup device according to the first or second aspect, the aperture changing means is a liquid crystal shutter capable of changing a diameter of a transmitted light beam in accordance with a driving condition in accordance with the type of the optical disk. It is characterized by comprising.

  According to an eighth aspect of the present invention, in the optical pickup device according to the first or second aspect, the optical path changing unit includes an expander lens composed of two or more lens systems, and an optical disk with an interval between the lens groups. And a moving mechanism that can be changed according to the type of the apparatus.

  According to a ninth aspect of the present invention, in the optical pickup device according to the eighth aspect, the moving mechanism can further change the distance between the lens groups in accordance with each layer in the same optical disc having multiple recording layers. It is characterized by.

  According to a tenth aspect of the present invention, in the optical pickup device according to the eighth aspect, the expander lens is a color correction lens that corrects chromatic aberration of a focused spot formed on an optical disk recording surface. .

  According to an eleventh aspect of the present invention, in the optical pickup device according to the first or second aspect, the optical path changing means includes a collimating lens disposed in an optical path between the light source and the objective lens, and a collimating lens of the type of the optical disc. And a moving mechanism that moves in the direction of the optical axis correspondingly.

  According to a twelfth aspect of the present invention, in the optical pickup device according to the eleventh aspect, the moving mechanism further moves the collimating lens in the optical axis direction corresponding to each layer in the same optical disk having a plurality of recording layers. It is characterized by being able to.

  According to a thirteenth aspect of the present invention, in the optical pickup device according to the first or second aspect, the optical path changing unit includes a birefringent medium that changes a convergent divergence state of the emitted light beam according to a polarization direction of the incident light beam, It is characterized by comprising a λ / 2 wave plate that rotates the polarization direction of the incident light beam by 90 degrees.

  According to a fourteenth aspect of the present invention, in the optical pickup device according to the thirteenth aspect, the λ / 2 wavelength plate is a liquid crystal phase plate capable of rotating or not rotating the polarization direction of the incident light beam by 90 degrees depending on driving conditions. It is characterized by that.

  According to a fifteenth aspect of the present invention, in the optical pickup device according to the first or second aspect, the optical path changing unit includes a polarization hologram that changes a convergent divergence state of the emitted light beam according to a polarization direction of the incident light beam, and an incident light And a λ / 2 wave plate that rotates the polarization direction of the light beam to be rotated by 90 degrees.

  According to a sixteenth aspect of the present invention, in the optical pickup device according to the fifteenth aspect, the λ / 2 wavelength plate is a liquid crystal phase plate capable of rotating or not rotating the polarization direction of the incident light beam by 90 degrees depending on driving conditions. It is characterized by that.

  The invention according to claim 17 is characterized in that the optical pickup device according to any one of claims 1 to 16 is mounted.

  According to the first and second aspects of the invention, 1) since the aperture changing means for the light beam incident on the objective lens without changing the configuration of the objective lens and the light flux changing means are provided independently, Compared with the method of changing the distance between the group objective lenses, tolerances such as lens movement can be loosened, the condensed spot is less deteriorated, and recording / reproduction quality can be ensured. 2) The objective lens can be implemented as a single lens. Therefore, it is not necessary to use a two-group objective lens as in Patent Document 1, and a working distance between the objective lens and the disk surface can be secured. 3) Since not only the aperture changing means using the polarization direction but also the light flux changing means are used in combination, the aperture limitation in which the spherical aberration of the substrate thickness is corrected is also applied to a standard disk having a larger numerical aperture than that of Patent Document 2. Is possible.

  According to the third aspect of the invention, 1) it is only necessary to mount the λ / 2 plate in the fixed portion by setting the polarizing filter as an opening, and to mount only a light polarizing filter on the actuator. The burden is reduced and the speed can be increased. 2) In Patent Document 2, two light sources are required, but by using a λ / 2 plate, a single light source can be used, so that the apparatus can be reduced in size and cost.

  According to the fourth aspect of the present invention, the movement mechanism of the λ / 2 plate is required in the third aspect, but the movement mechanism becomes unnecessary by using the liquid crystal phase plate, and the downsizing of the apparatus is realized.

  According to the invention of claim 5, 1) as in the case of claim 3, it is only necessary to place a λ / 2 plate on the fixed portion and mount a lightweight polarization hologram on the actuator, and drive the actuator. The burden is reduced and the speed can be increased. 2) Further, according to the third aspect of the invention, the polarized light that does not pass through the annular zone between 4a and 4b is reflected and becomes flare light of the signal detection unit. This adverse effect can be reduced and the signal quality can be improved.

  According to the sixth aspect of the present invention, the movement mechanism of the λ / 2 plate is required in the fifth aspect, but the movement mechanism becomes unnecessary by using the liquid crystal phase plate, and the downsizing of the apparatus is realized.

  According to the invention of claim 7, it is necessary to mount both the 47a and the 47b on the actuator by selecting the opening region using the liquid crystal element in which the transparent electrode is formed, but a multilayer deposited film is necessary. This eliminates the need for a polarizing filter or a polarizing hologram that requires a fine lattice shape or a complicated layer structure, thereby realizing cost reduction.

  According to the invention of claim 8, the mechanism of claim 1 or the like requires a mechanism for inserting and removing the concave lens in the optical path, but by using the expander lens, the moving lens is moved slightly in the optical axis direction. This improves the size of the entire optical system.

  According to the ninth aspect of the present invention, the expander lens can also be used as a spherical aberration correction means that generates multiple layers, and thus the entire optical system can be reduced in size and cost.

  According to the invention of claim 10, the expander lens composed of two or more lens systems has a large degree of freedom in combination of the glass material and focal length of each lens, and on the optical disk recording surface generated by the objective lens and the collimating lens. The chromatic aberration of the condensed spot can be corrected. Therefore, even when the wavelength fluctuates due to the internal temperature of the apparatus or the light emission output of the light source, since the condensing position of the spot formed on the optical disk recording surface does not change, stable recording / reproduction can always be performed.

  According to the invention of claim 11, by using the collimating lens for the light beam changing means, unnecessary parts are not required, and the entire optical system can be downsized.

  According to the invention of claim 12, when the disk is a multi-layer recording layer, the light beam changing means using the collimating lens is generated depending on the thickness of the substrate up to each recording layer by further moving the collimating lens at each position. Spherical aberration can be corrected. That is, since it can also be used as a means for correcting spherical aberration generated by multiple layers, it is possible to further reduce the size and cost of the entire optical system.

  According to the invention of claim 13, since the birefringent medium is thin and lightweight, it can be mounted on the objective lens actuator together with the objective lens. Therefore, even in the case of diverging light, there is no adverse effect such as deterioration of the shape of the focused spot due to the axis deviation of the objective lens, so that good recording / reproducing performance can be realized.

  According to the fourteenth aspect of the present invention, the λ / 2 plate moving mechanism is required in the thirteenth aspect. However, by using the liquid crystal phase plate, the moving mechanism becomes unnecessary and the apparatus can be downsized. <Claim 1

  According to the invention of claim 15, 1) since the polarization hologram is thin and lightweight, it can be mounted on the objective lens actuator together with the objective lens. Therefore, even in the case of diverging light, there is no adverse effect such as deterioration of the shape of the focused spot due to the axis deviation of the objective lens, so that good recording / reproducing performance can be realized. 2) Further, the manufacturing cost is low, and the cost can be reduced.

  According to the sixteenth aspect of the invention, in the fifteenth aspect, the moving mechanism of the λ / 2 plate is necessary. However, by using the liquid crystal phase plate, the moving mechanism becomes unnecessary and the apparatus can be downsized.

  The optical disk drive apparatus according to claim 17, wherein the optical pickup apparatus as described above is mounted, and a common light source and a common objective lens are used for each of various optical disks of different standards due to differences in substrate thickness. Since an appropriate opening can be selected by correcting the above, it is possible to realize an optical disk drive device that ensures compatibility with a simple configuration.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIGS. 1 (a) and 1 (b) are configuration diagrams showing a first embodiment of an optical pickup device according to the present invention as a main part. In the figure, reference numeral 1 denotes a hologram unit, which includes a laser light source 1L, a hologram element 1h for diffracting reflected light from the disk to obtain a necessary signal, and a plurality of regions for generating various signals. The light receiving element 1p is configured.

  The divergent light beam from the hologram unit 1 is converted into parallel light by the collimator lens 2 and is condensed on the recording surface of the optical disc 61 by the objective lens 5 after the opening diameter is limited by the opening 4a. The reflected light from the disc is incident on the hologram unit 1 again, and a track signal, a focus signal, an information signal, and the like are generated by the light receiving element 1p. The objective lens 5 is servoed by an actuator (not shown) according to a track signal or a focus signal, and always follows the movement of the disk to focus a diffraction-limited spot on the disk recording surface.

  On the other hand, when the optical disc 62, which is different from the above-described optical disc 61 and has a different substrate thickness (interval between the disc surface and the recording layer), is inserted into the apparatus, the aperture changing means replaces the aperture 4a with the aperture 4b. Further, a concave lens 3 is inserted in front of the collimating lens as a light beam changing means. As the opening changing means, for example, in the schematic configuration diagram of FIG. 3A, the opening member 41 has openings 4a and 4b having different diameters, and the opening is switched by moving in the arrow direction. In addition, the aperture member may be an aperture shutter used in a camera or the like. Similarly, the concave lens 3 can be inserted into the optical path by moving in the direction of the arrow (see FIG. 1). Each of the aperture changing means and the light flux changing means has an appropriate moving mechanism (not shown) for moving the aperture and the concave lens.

  Here, for example, if the objective lens 5 is designed to focus the spot on the recording surface with respect to the substrate thickness of the optical disc 61, the objective lens 5 has a spherical surface for the optical disc 62 having a different substrate thickness. Aberration will occur. This aberration can be corrected by using the concave lens 3 to change the convergence / divergence state of the light beam incident on the objective lens. An example of verification is shown in FIG. 2 and Tables 1 and 2. FIG. 2A shows a design example of an objective lens unit corresponding to the Blu-ray standard, and FIG.

  In FIG. 2A, the objective lens 5 is a product conforming to the Blu-ray standard that collects a parallel light beam having a wavelength of 405 nm on an optical disk recording surface having a substrate thickness of 0.1 mm at NA 0.85. The focal length f is 2.74 mm, the diameter of the opening 4a is φ4.66 mm, and the on-axis wavefront aberration is 0.0057λrms. Table 1 below shows lens data of the objective lens 5.

  The three-surface and four-surface aspherical shape Z of the objective lens is represented by the following general formula (1), where h is the distance from the central axis, R is the curvature radius, and the reciprocal of R, that is, the curvature is c.

  FIG. 2B is a diagram in which the light source position and the working distance are adjusted in the case of an optical disk having a substrate thickness of 0.6 mm using the same light source and objective lens. By setting the light source position to 47.432 mm from infinity and the working distance to 1.290 mm, the on-axis wavefront aberration can be reduced to 0.0221 λrms. The diameter of the opening 4b at this time is φ3.62 mm and NA 0.65. Table 2 below shows lens data at that time.

  As described above, the spherical aberration generated can be made sufficiently small by changing the convergence / divergence state of the light beam incident on the objective lens for the standards having different substrate thicknesses and numerical apertures. The convergent and divergent state of the light beam varies depending on the insertion / extraction of the concave lens and the focal length of the concave lens as shown in FIG. 1, and it can be seen that by adapting this, various standards with different substrate thicknesses can be accommodated.

[Second Embodiment]
As the aperture changing means, in addition to the above, a polarizing filter that may or may not transmit depending on the polarization direction of the incident light beam in a certain region may be used. Reference numeral 42 in FIG. 3 (b) denotes a polarizing filter in which regions are formed. The inside of the opening 4b is a region that transmits light in all polarization directions, and the annular region between 4a and 4b transmits vertically polarized light. The area to be transmitted and the outside of 4a are areas that do not transmit in all polarization directions. When a light beam having vertically polarized light is incident on the polarizing filter, the light beam limited by the aperture 4a is transmitted. Here, when a λ / 2 plate 43 having a delay axis in the 45-degree direction is inserted as shown in FIG. 3C, the polarization direction rotates in the horizontal direction and enters the polarization filter. Therefore, the light beam limited by the opening 4b is transmitted from the polarizing filter.

  Normally, the objective lens is servoed by an actuator and always follows the movement of the disk. However, in order not to cause an axial deviation of the aperture with respect to the objective lens, the aperture needs to be moved in the same manner as the objective lens. Therefore, in the form using the opening 41 as shown in FIG. 3A, it is necessary to mount the opening and its moving mechanism on the actuator. If the polarizing filter 42 is thus opened, the λ / 2 plate 43 is formed. It is only necessary to mount a lightweight member such as 42 on the actuator so that the actuator is disposed on the fixed portion, and the driving load of the actuator can be reduced and the speed can be increased.

[Third Embodiment]
Further, as shown in FIG. 3D, a λ / 2 plate may be used as the liquid crystal element 44, and the driving condition may be switched by the driving power supply 45, and the polarization direction of the light beam transmitted through the liquid crystal element is set to be vertical or horizontal. Can be changed (liquid crystal phase plate). In the above-described embodiment, the movement mechanism of the λ / 2 plate is necessary. However, by using such a liquid crystal phase plate, the movement mechanism becomes unnecessary and the apparatus can be downsized.

[Fourth Embodiment]
In addition to this, the aperture changing means can be configured using a polarization hologram that may or may not diffuse depending on the polarization direction of the incident light beam for a certain region. Reference numeral 46 in FIG. 4 (a) denotes a polarization hologram in which a region is formed. The inside of the opening 4b is a region that transmits in all polarization directions, and the annular region between 4a and 4b transmits vertically polarized light. , A region that diffuses polarized light in the horizontal direction by diffraction, and a region outside 4a is a region that does not transmit in all polarization directions. When a light beam having vertical polarization enters the polarization hologram 46, the light beam limited by the opening 4a is transmitted. Here, when a λ / 2 plate 43 having a delay axis in the 45-degree direction is inserted as shown in FIG. 4B, the polarization direction rotates in the horizontal direction and enters the polarization hologram 46. Therefore, the light beam limited by the aperture 4b is transmitted from the polarization hologram 46.

  Similar to the above-described configuration, it is only necessary to arrange the λ / 2 plate in the fixed portion and mount a lightweight member such as 46 on the actuator, and the driving load of the actuator can be reduced and the speed can be increased. Furthermore, in the above configuration, the polarized light that does not pass through the annular zone between 4a and 4b is reflected and becomes flare light of the signal detection unit, but the polarization hologram diffuses such a light flux, so that Such adverse effects can be reduced, and the signal quality is improved.

[Fifth Embodiment]
Further, as shown in FIG. 4C, the polarization direction of the light beam transmitted through the liquid crystal element can be changed to be vertical or horizontal by using the λ / 2 plate as the liquid crystal element 44 and switching the driving conditions by the driving power supply 45. Yes (liquid crystal phase plate). Therefore, in the previous embodiment, a moving mechanism for the λ / 2 plate was necessary. However, by using the liquid crystal phase plate, the moving mechanism becomes unnecessary and the apparatus can be downsized.

[Sixth Embodiment]
As the aperture changing means, a liquid crystal shutter combining a liquid crystal element and a polarizing plate can be used. Reference numeral 47 in FIG. 4D denotes a liquid crystal shutter. A liquid crystal element 47a can change the polarization direction of the light beam transmitted through the annular zone between the openings 4a and 4b under the control of the drive power supply 45. That is, the transparent electrode 47a is formed in the shape of the annular zone between the openings 4a and 4b. When an electric field is applied to the transparent electrode 47a, the liquid crystal molecules rotate to pass incident polarized light. Since no electric field is applied to the inside of 4b, the incident polarized light is always rotated by 90 degrees and emitted. The outside of 4a is in a state where it does not transmit in all polarization directions, for example, a state like a normal light shielding plate. Reference numeral 47b denotes a polarizing plate that transmits horizontally polarized light over the entire surface.

  When a light beam having a polarization in the vertical direction is incident on the liquid crystal shutter 47, a light beam having a polarization in the horizontal direction limited by the opening of 4a is emitted from 47a, and then transmitted through 47b. Next, when an electric field is applied to the liquid crystal element by the driving power supply 45, the vertically polarized light in the annular zone between the openings 4a and 4b is shielded by the polarizing plate 47b, and a light beam having a diameter of 4b is emitted.

  As described above, in the configuration in which the opening region is selected using the liquid crystal element on which the transparent electrode is formed, it is necessary to mount both 47a and 47b on the actuator. A polarizing hologram that requires a filter, a fine grating shape, or a complicated layer structure is not required, and cost reduction is realized.

[Seventh Embodiment]
Next, a specific example of the light beam changing means will be shown. As the light beam changing means, an expander lens that changes the convergence / divergence state of the emitted light beam by changing the group interval of two or more lens systems can be used. Reference numeral 3 in the schematic configuration diagram of FIG. 5A denotes an expander lens, which includes a fixed lens 31 and a moving lens 32 that moves in the optical axis direction by an expander actuator 33. The expander lens 31 is disposed in the optical path between the collimating lens 2 and the opening 4a shown in FIG. 1A. For example, in the case of the disk 61 in FIG. In the case of the disk 62 in (b), the moving lens moves to cause the divergent light beam to enter the objective lens. In the configuration using a simple concave lens as shown in FIG. 1, a mechanism for inserting / removing the concave lens into / from the optical path was required. However, by using an expander lens, it is only necessary to move the moving lens slightly in the optical axis direction. The entire system can be downsized.

  The expander lens 3 composed of two or more lens systems has a large degree of freedom in combining the glass material and focal length of each lens, and corrects the chromatic aberration of the focused spot on the optical disk recording surface generated by the objective lens and collimating lens. can do. With this configuration, even when the wavelength fluctuates due to the internal temperature of the apparatus or the light emission output of the light source, the focal position of the spot formed on the optical disc recording surface does not change, so stable recording / reproduction is always possible. Become.

[Eighth Embodiment]
The expander lens as the light beam changing means having the above configuration is generated by the substrate thickness up to each recording layer if the moving lens is further moved at each position when the disk 61 or 62 is a multi-layer recording layer. Spherical aberration can be corrected. That is, since it can also be used as a means for correcting spherical aberration generated by multiple layers, the entire optical system can be further reduced in size and cost.

[Ninth Embodiment]
As other light beam changing means, a means for changing the convergence / divergence state of the emitted light beam by moving a collimating lens that collimates the light beam from the light source in the optical axis direction can be used. Reference numeral 21 shown in FIG. 5B denotes a collimating lens having an actuator 22 that moves the collimating lens in the optical axis direction. The collimating lens 21 is disposed in the optical path between the hologram unit 1 and the opening 4a, for example, similarly to the collimating lens shown in FIG. 1A, and the emitted light from the collimating lens is shown in FIG. In the case of the disk 61, the parallel light beam is entered, and in the case of the disk 62 in FIG. 1B, the lens moves in the optical axis direction so that the divergent light beam enters the objective lens. By using such a collimating lens 21 for the light beam changing means, unnecessary parts are not required, and the entire optical system can be downsized.

[Tenth embodiment]
In the light beam changing means using the collimating lens 21, when the disk 61 or 62 is a multi-layer recording layer, the collimating lens is further moved at each position to correct spherical aberration caused by the substrate thickness up to each recording layer. It is also possible to support two layers. That is, since it can also be used as a correction means for correcting spherical aberration caused by multiple layers, it is possible to further reduce the size and cost of the entire optical system.

[Eleventh embodiment]
Further, as the light beam changing means, a combination means of a birefringent medium that changes the convergence and divergence state of the emitted light beam according to the polarization direction of the incident light beam and a λ / 2 wavelength plate that rotates the polarization direction of the incident light beam by 90 degrees. Can be used. Reference numeral 34 in FIG. 6A denotes a birefringent medium. The birefringent medium has a configuration in which a concave lens-shaped liquid crystal is sandwiched between glass plates at the center (shaded portion) as in the liquid crystal lens disclosed in, for example, [Patent Document 3]. Due to the polarization selectivity of the liquid crystal, the light beam passes through the birefringent medium without being subjected to a lens action, because the refractive index of the liquid crystal and that of glass are the same for the polarized light in the direction parallel to the plane of FIG. On the other hand, when the polarization direction is changed to the direction perpendicular to the paper surface by inserting the λ / 2 plate 35 in FIG. 6B, the refractive index of the liquid crystal and that of the glass are different. For example, when the refractive index of the liquid crystal is larger, the luminous flux Since the lens receives a diverging lens action, spherical aberration can be corrected according to the type of optical disk. Since the birefringent medium is thin and lightweight, it can be mounted on the objective lens actuator together with the objective lens. Therefore, even in the case of diverging light, there is no adverse effect such as deterioration of the shape of the focused spot due to the axis deviation of the objective lens, so that good recording / reproducing performance can be realized.

[Twelfth embodiment]
As a similar configuration (not shown), as the light beam changing means, the λ / 2 plate 35 is used as a liquid crystal element as in the case of FIG. 3 (d), and the polarization of the light beam transmitted through the liquid crystal element by switching the driving condition with a driving power source. The direction can be changed to vertical or horizontal. Therefore, in the previous embodiment, a moving mechanism for the λ / 2 plate was necessary. However, by using the liquid crystal phase plate, the moving mechanism becomes unnecessary and the apparatus can be downsized.

[Thirteenth embodiment]
Further, as the light beam changing means, a combination means of a polarization hologram that changes the convergent divergence state of the emitted light beam according to the polarization direction of the incident light beam and a λ / 2 wavelength plate that rotates the polarization direction of the incident light beam by 90 degrees is used. be able to.

  Reference numeral 36 in FIG. 6C denotes a polarization hologram. Since the polarization hologram has polarization selectivity with respect to the diffraction efficiency, the incident light passes through the element as zero-order light without generating first-order or higher-order diffracted light for the polarized light in the direction parallel to the paper surface of (c). On the other hand, when the polarization direction is changed to the direction perpendicular to the paper surface by inserting the λ / 2 plate 35 as shown in FIG. 6D, the diffraction efficiency of the primary light increases, and the incident light is diverged as the primary light. Receives lens action. Therefore, spherical aberration correction can be performed in accordance with the type of optical disk.

  Since the polarization hologram is thin and lightweight, it can be mounted on the objective lens actuator together with the objective lens. Therefore, even in the case of diverging light, there is no adverse effect such as deterioration of the shape of the focused spot due to the axis deviation of the objective lens, so that good recording / reproducing performance can be realized. Further, the manufacturing cost is low, and the cost can be reduced.

[Fourteenth embodiment]
Further, as the light beam changing means, the λ / 2 plate 35 in FIG. 6D is fixed as a liquid crystal element, and the polarization condition of the light beam incident on the polarization hologram is changed to vertical or horizontal by switching the driving condition with a driving power source. Can be changed to Therefore, in the previous embodiment (FIG. 6D), a moving mechanism for the λ / 2 plate was necessary. However, by using a liquid crystal phase plate as in this embodiment, the moving mechanism becomes unnecessary and the device can be downsized. The

[Fifteenth embodiment]
The optical pickup device as described above is used in an optical disk drive device. An exemplary embodiment of an optical disk drive device on which an optical pickup device is mounted is shown in the main configuration diagram of FIG. In the figure, reference numeral 1 is a hologram unit, and 2 is an expander lens that is also used as a collimating lens. The lenses 21 and 22 collimate a light beam from a light source. The lens 22 has an actuator and is movable in the optical axis direction.

  Reference numeral 47 denotes a liquid crystal shutter, which includes the liquid crystal element 47a and the polarizing plate 47b shown in FIG. Reference numeral 5 denotes an objective lens having an objective lens actuator 51. When the target optical disk is the disk 61, the parallel light beam from the opening 4a is incident on the objective lens to perform recording / reproduction. When the disk 62 is used, the lens 22 moves to the objective lens, and the liquid crystal shutter is driven by the driving power source 45 so that the divergent light beam from the opening 4b is incident to perform recording and reproduction. This optical disk drive device uses a common light source and a common objective lens, and can correct aberrations due to differences in substrate thickness and select an appropriate aperture for each of various standard optical disks. It is possible to realize an optical disk drive device that ensures compatibility with a simple configuration.

(a), (b) is a block diagram which shows the 1st Embodiment of an optical pick-up apparatus by the principal part. It is a figure which shows the example of a design of an objective lens part, (a) is a Blu-ray standard, (b) shows the case equivalent to HD-DVD standard. (a)-(d) is a schematic block diagram explaining various embodiment of an opening change means, respectively. (a)-(d) is a schematic block diagram explaining a polarization hologram (aperture changing means), respectively. (a)-(b) is a schematic block diagram explaining various embodiment of a light beam change means, respectively. (a)-(d) is a schematic block diagram explaining other embodiment of a light beam change means. It is a principal part block diagram of the optical disk drive device of this invention carrying an optical pick-up apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hologram unit 1L ... Laser light source 1h ... Hologram element 1p ... Light receiving element 2, 21 ... Collimator lens 22 ... Actuator 3 ... Concave lens (light beam changing means)
DESCRIPTION OF SYMBOLS 3 ... Expander lens 31 ... Fixed lens 32 ... Moving lens 33 ... Expander actuator 34 ... Birefringence medium 35 ... Lambda / 2 plate 36 ... Polarization hologram 41, 4a, 4b ... Aperture 42 ... Polarization filter (aperture)
43 ... λ / 2 plate 44 ... Liquid crystal element (liquid crystal phase plate)
45 ... Driving power source 46 ... Polarization hologram 47 ... Liquid crystal shutter 47a ... Liquid crystal element 47b ... Polarizing plate 5 ... Objective lenses 61, 62 ... Optical disc

Claims (17)

An optical pickup that uses a common light source and a common objective lens to focus light beams from the light source on a plurality of types of optical disk recording surfaces having different substrate thicknesses and perform at least one operation of recording, reproduction, and erasing In the device
Aperture changing means for changing the effective numerical aperture of the objective lens corresponding to the type of the optical disk, and a light flux changing means for changing the convergence / divergence state of the light flux incident on the objective lens corresponding to the type of the optical disk. A characteristic optical pickup device.   The types of the optical disc include a Blu-ray standard disc having a substrate thickness of 0.1 mm and a numerical aperture of 0.85, and an HD-DVD standard disc having a substrate thickness of 0.6 mm and a numerical aperture of 0.65. The optical pickup device according to claim 1.   The aperture changing means is composed of a polarizing filter that changes the diameter of the transmitted light beam according to the polarization direction of the incident light beam, and a λ / 2 wavelength plate that rotates the polarization direction of the incident light beam by 90 degrees. The optical pickup device according to claim 1 or 2.   4. The optical pickup device according to claim 3, wherein the λ / 2 wavelength plate is a liquid crystal phase plate capable of rotating or not rotating the polarization direction of the incident light beam by 90 degrees depending on driving conditions.   The aperture changing means is composed of a polarization hologram in which the diameter of the transmitted light beam changes depending on the polarization direction of the incident light beam, and a λ / 2 wavelength plate that rotates the polarization direction of the incident light beam by 90 degrees. The optical pickup device according to claim 1 or 2.   6. The optical pickup device according to claim 5, wherein the λ / 2 wavelength plate is a liquid crystal phase plate capable of rotating or not rotating the polarization direction of the incident light beam by 90 degrees depending on driving conditions.   3. The optical pickup device according to claim 1, wherein the aperture changing means is constituted by a liquid crystal shutter capable of changing a diameter of a transmitted light beam according to a driving condition in accordance with the type of the optical disk.   The optical path changing means includes an expander lens composed of two or more lens systems, and a moving mechanism that can change the distance between the lens groups in accordance with the type of the optical disk. The optical pickup device according to claim 1 or 2.   9. The optical pickup device according to claim 8, wherein the moving mechanism can further change the interval between the lens groups in accordance with each layer in the same optical disc having multiple recording layers.   9. The optical pickup device according to claim 8, wherein the expander lens is a color correction lens that corrects chromatic aberration of a focused spot formed on an optical disk recording surface.   The optical path changing means includes a collimating lens disposed in the optical path between the light source and the objective lens, and a moving mechanism that moves the collimating lens in the optical axis direction according to the type of the optical disc. The optical pickup device according to claim 1 or 2.   12. The optical pickup device according to claim 11, wherein the moving mechanism can further move the collimating lens in the optical axis direction corresponding to each layer in the same optical disc having a plurality of recording layers.   The optical path changing means is composed of a birefringent medium that changes the convergent divergence state of the emitted light beam according to the polarization direction of the incident light beam, and a λ / 2 wavelength plate that rotates the polarization direction of the incident light beam by 90 degrees. The optical pickup device according to claim 1, wherein:   14. The optical pickup device according to claim 13, wherein the λ / 2 wavelength plate is a liquid crystal phase plate capable of rotating or not rotating the polarization direction of the incident light beam by 90 degrees depending on driving conditions.   The optical path changing means is composed of a polarization hologram that changes a convergent divergence state of the emitted light beam according to a polarization direction of the incident light beam, and a λ / 2 wavelength plate that rotates the polarization direction of the incident light beam by 90 degrees. 3. The optical pickup device according to claim 1, wherein the optical pickup device is characterized in that:   16. The optical pickup device according to claim 15, wherein the λ / 2 wave plate is a liquid crystal phase plate capable of rotating or not rotating the polarization direction of the incident light beam by 90 degrees depending on driving conditions. An optical disk drive device, comprising the optical pickup device according to any one of claims 1 to 16.

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