JP2004259413A - Optical pickup device and objective lens therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact optical pickup device capable of recording and/or reproducing proper information, for example, in/from all of a high-density DVD, a conventional DVD, and a CD, and to provide an objective lens. <P>SOLUTION: This device is provided with a first optical path PT1 formed to only pass a luminous flux emitted from a first light source, a second optical path PT2 formed to only pass a luminous flux emitted from a second light source, a third optical path PT3 formed to only pass a luminous flux emitted from a third light source, a fourth optical path PT4 formed to pass both of the luminous fluxes emitted from the second and third light sources, and a fifth optical path PT5 formed to pass both of the luminous fluxes passed through the fourth and first optical paths PT4 and PT1. This arrangement of the optical paths enables an optical element suited to the recording and/or reproducing of information in different optical information recording media such as a CD, a DVD and a high-density DVD, and thus the degree of freedom of designing an optical pickup device is increased. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical pickup device and an optical element used for the same, and more particularly, to recording and / or recording information on three different optical information recording media using light beams emitted from three light sources having different light source wavelengths. Also, the present invention relates to an optical pickup device capable of reproducing and an objective lens used therein.
[0002]
[Prior art]
In recent years, research and development of a high-density optical disk system capable of recording / reproducing information using a blue-violet semiconductor laser having a wavelength of about 400 nm have been rapidly progressing. As an example, in an optical disk that performs information recording / reproduction with a specification of 0.85 NA and a light source wavelength of 405 nm (hereinafter, such an optical disk is referred to as a “high-density DVD” in this specification), a DVD (NA 0.6, light source wavelength 650 nm, It is possible to record 20 to 30 GB of information per surface on an optical disc having a diameter of 12 cm which is the same size as the storage capacity of 4, 7 GB.
[0003]
By the way, just being able to record / reproduce information appropriately on such a high-density DVD is not enough as a product of the optical pickup device. At present, in consideration of the fact that DVDs and CDs recording various kinds of information are sold, it is not enough to be able to record / reproduce information appropriately for high-density DVDs. Alternatively, enabling information to be appropriately recorded / reproduced on a CD also leads to an increase in the value of a product as a compatible type optical pickup device. From such a background, it is desired that the condensing optical system used in the compatible type optical pickup device can appropriately record / reproduce information on any of high-density DVD, conventional DVD, and CD. It is rare. An example of such a compatible type optical pickup device is described in, for example, Patent Document 1 below.
[Patent Document 1]
JP-A-2001-43559
[Problems to be solved by the invention]
When recording and / or reproducing information on a CD, a DVD, and a high-density DVD, it is generally necessary to use light sources having different wavelengths. However, how to arrange such a light source poses a problem. For example, in Patent Literature 1, information is recorded and / or reproduced from / to a DVD from a middle of an optical path through which a light beam from a first light source passes through for recording and / or reproducing information from / to a high-density DVD. Is arranged so that a light beam from a second light source for performing the above-described operation is made incident, and thereafter, an optical axis from a third light source for performing recording and / or reproduction of information on the CD is made incident. However, such an optical path arrangement has a problem in that the degree of freedom in designing the optical pickup device is limited. For example, in the case of using a type having two information recording surfaces as a high-density DVD, a beam expander including a plurality of optical elements movable in the optical axis direction is provided in an optical path through which a light beam from the first light source passes. The two-layer information recording is realized by arranging such a beam expander. However, in the technique of Patent Document 1, if such a beam expander is arranged, the first light source must be arranged at a farther place, and the optical pickup is required. The device cannot be made compact.
[0005]
The present invention has been made in view of such a problem, and has an optical pickup device that is compact and can appropriately record and / or reproduce information on, for example, all of high-density DVDs and conventional DVDs and CDs. And an objective lens.
[0006]
[Means for Solving the Problems]
The optical pickup device according to claim 1, wherein the optical pickup device includes a first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), a third light source having a wavelength λ3 (λ2 <λ3), and an objective lens. An optical optical system, wherein the condensing optical system converges a light beam from the first light source onto an information recording surface of the first optical information recording medium via a protective layer having a thickness of t1. Recording and / or reproduction of information can be performed, and a light beam from the second light source is focused on the information recording surface of the second optical information recording medium via a protective layer having a thickness of t2. By doing so, it is possible to record and / or reproduce information. Further, the luminous flux from the third light source is passed through a protective layer having a thickness t3 (t1 <t3 and t2 <t3). By condensing the information on the information recording surface of the three-optical information recording medium, information can be recorded and / or reproduced. An optical pickup apparatus it is possible to perform,
The objective lens is configured to perform recording and / or reproduction on the first optical information recording medium, the second optical information recording medium, and the third optical information recording medium, respectively. A light source, and an inner region centered on an optical axis through which light beams respectively emitted from the third light source pass in common to form a condensed spot on each information recording surface; When performing recording and / or reproduction on the information recording medium and the second optical information recording medium, respectively, the light beams emitted from the first light source and the second light source respectively pass through in common to record each information. When recording and / or reproducing from / to the first optical information recording medium and an intermediate area around the optical axis that forms a converging spot on the surface, the light is emitted from the first light source. Light beam passes through and collects on the information recording surface. And an outer region around the optical axis so as to form a spot,
A first optical path through which only the light emitted from the first light source passes, a second optical path through which only the light emitted from the second light source passes, and a third optical path through which only the light emitted from the third light source passes A fourth light path through which the light beam emitted from the second light source and the light beam emitted from the third light source pass in common; a light beam passing through the fourth light path; and a light beam passing through the first light path Has a fifth optical path that passes in common,
The objective lens is disposed in the fifth optical path.
[0007]
FIG. 4 is a schematic diagram showing an optical path from each light source in the optical pickup device according to the first aspect. In FIG. 4, a first optical path PT1 through which only a light beam emitted from the first light source passes, a second optical path PT2 through which only a light beam emitted from the second light source passes, and only a light beam emitted from the third light source passes. The third light path PT3, the fourth light path PT4 through which the light beam emitted from the second light source and the light beam emitted from the third light source pass in common, the light beam passing through the fourth light path PT4, and the first light path PT1 A fifth optical path PT5 through which the passed light beam passes in common is formed. By arranging the optical paths in this manner, for example, an optical element suitable for recording and / or reproducing information on different optical information recording media such as a CD, a DVD, and a high-density DVD is arranged in each optical path. Because it is possible, the degree of freedom in designing the optical pickup device is increased. In addition, the objective lens may be arranged in the fifth optical path, and there is no need to provide an objective lens dedicated to a different optical information recording medium or a switching mechanism thereof, which contributes to cost reduction.
[0008]
The optical pickup device according to claim 2, wherein the optical pickup device includes a first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), a third light source having a wavelength λ3 (λ2 <λ3), and an objective lens. An optical optical system, wherein the condensing optical system converges a light beam from the first light source onto an information recording surface of the first optical information recording medium via a protective layer having a thickness of t1. Recording and / or reproduction of information can be performed, and a light beam from the second light source is focused on the information recording surface of the second optical information recording medium via a protective layer having a thickness of t2. By doing so, it is possible to record and / or reproduce information. Further, the luminous flux from the third light source is passed through a protective layer having a thickness t3 (t1 <t3 and t2 <t3). By condensing the information on the information recording surface of the three-optical information recording medium, information can be recorded and / or reproduced. An optical pickup apparatus it is possible to perform,
The objective lens is configured to perform recording and / or reproduction on the first optical information recording medium, the second optical information recording medium, and the third optical information recording medium, respectively. A light source, and an inner region centered on an optical axis through which light beams respectively emitted from the third light source pass in common to form a condensed spot on each information recording surface; When performing recording and / or reproduction on the information recording medium and the second optical information recording medium, respectively, the light beams emitted from the first light source and the second light source respectively pass through in common to record each information. When recording and / or reproducing from / to the first optical information recording medium and an intermediate area around the optical axis that forms a converging spot on the surface, the light is emitted from the first light source. Light beam passes through and collects on the information recording surface. And an outer region around the optical axis so as to form a spot,
A first optical path through which only the light emitted from the first light source passes, a second optical path through which only the light emitted from the second light source passes, and a third optical path through which only the light emitted from the third light source passes A fourth light path through which a light beam emitted from the first light source and a light beam emitted from the second light source pass in common; a light beam passing through the fourth light path; and a light beam passing through the third light path Has a fifth optical path that passes in common,
The objective lens is disposed in the fifth optical path.
[0009]
FIG. 5 is a schematic diagram showing an optical path from each light source in the optical pickup device according to the second aspect. In FIG. 5, a first optical path PT1 through which only a light beam emitted from the first light source passes, a second optical path PT2 through which only a light beam emitted from the second light source passes, and only a light beam emitted from the third light source passes. The third light path PT3, the fourth light path PT4 through which the light beam emitted from the first light source and the light beam emitted from the second light source pass in common, the light beam passing through the fourth light path PT4, and the third light path PT3 It has a fifth optical path PT5 through which the passed light beam passes in common. By arranging the optical paths in this manner, for example, an optical element suitable for recording and / or reproducing information on different optical information recording media such as a CD, a DVD, and a high-density DVD is arranged in each optical path. Because it is possible, the degree of freedom in designing the optical pickup device is increased. In addition, the objective lens may be arranged in the fifth optical path, and there is no need to provide an objective lens dedicated to a different optical information recording medium or a switching mechanism thereof, which contributes to cost reduction.
[0010]
An optical pickup device according to a third aspect of the present invention provides an optical pickup device including a first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), a third light source having a wavelength λ3 (λ2 <λ3), and an objective lens. An optical optical system, wherein the condensing optical system converges a light beam from the first light source onto an information recording surface of the first optical information recording medium via a protective layer having a thickness of t1. Recording and / or reproduction of information can be performed, and a light beam from the second light source is focused on the information recording surface of the second optical information recording medium via a protective layer having a thickness of t2. By doing so, it is possible to record and / or reproduce information. Further, the luminous flux from the third light source is passed through a protective layer having a thickness t3 (t1 <t3 and t2 <t3). By condensing the information on the information recording surface of the three-optical information recording medium, information can be recorded and / or reproduced. An optical pickup apparatus it is possible to perform,
The objective lens is configured to perform recording and / or reproduction on the first optical information recording medium, the second optical information recording medium, and the third optical information recording medium, respectively. A light source, and an inner region centered on an optical axis through which light beams respectively emitted from the third light source pass in common to form a condensed spot on each information recording surface; When performing recording and / or reproduction on the information recording medium and the second optical information recording medium, respectively, the light beams emitted from the first light source and the second light source respectively pass through in common to record each information. When recording and / or reproducing from / to the first optical information recording medium and an intermediate area around the optical axis that forms a converging spot on the surface, the light is emitted from the first light source. Light beam passes through and collects on the information recording surface. And an outer region around the optical axis so as to form a spot,
A first optical path through which only the light emitted from the first light source passes, a second optical path through which only the light emitted from the second light source passes, and a third optical path through which only the light emitted from the third light source passes A fourth light path through which the light beam emitted from the first light source and the light beam emitted from the third light source pass in common; a light beam passing through the fourth light path; and a light beam passing through the second light path And a fifth optical path that passes in common,
The objective lens is disposed in the fifth optical path.
[0011]
FIG. 6 is a schematic diagram showing an optical path from each light source in the optical pickup device according to the third aspect. In FIG. 6, a first optical path PT1 through which only a light beam emitted from the first light source passes, a second optical path PT2 through which only a light beam emitted from the second light source passes, and only a light beam emitted from the third light source passes. The third light path PT3, the fourth light path PT4 through which the light beam emitted from the first light source and the light beam emitted from the third light source pass in common, the light beam passing through the fourth light path PT4, and the second light path PT2. A fifth optical path PT5 through which the passed light beam passes in common. By arranging the optical paths in this manner, for example, an optical element suitable for recording and / or reproducing information on different optical information recording media such as a CD, a DVD, and a high-density DVD is arranged in each optical path. Because it is possible, the degree of freedom in designing the optical pickup device is increased. In addition, the objective lens may be arranged in the fifth optical path, and there is no need to provide an objective lens dedicated to a different optical information recording medium or a switching mechanism thereof, which contributes to cost reduction.
[0012]
An optical pickup device according to a fourth aspect is the optical pickup device according to any one of the first to third aspects, wherein the axes of the at least two light beams coincide with each other in the optical path through which at least two light beams pass. Therefore, information can be recorded and / or reproduced more appropriately.
[0013]
According to a fifth aspect of the present invention, in the optical pickup device according to any one of the first to fourth aspects, a 波長 wavelength plate is disposed in the fifth optical path, so that the optical pickup device is more appropriately. It becomes possible to detect a recording signal and the like.
[0014]
According to a sixth aspect of the present invention, in the optical pickup device according to any one of the first to fifth aspects, a chromatic aberration correction element is disposed in the fifth optical path, so that the chromatic aberration is corrected. Thus, information can be recorded and / or reproduced more appropriately. In the embodiment described later, a diffractive structure or the like is provided on the optical surface of the objective lens to serve also as a chromatic aberration correction element. However, the chromatic aberration correction element does not necessarily need to be integrated with the objective lens. A body element may be provided or incorporated in a beam expander.
[0015]
An optical pickup device according to a seventh aspect is characterized in that, in the invention according to any one of the first to sixth aspects, a spherical aberration correction element is arranged in an optical path through which a light beam from the first light source passes. I do.
[0016]
According to an eighth aspect of the present invention, in the optical pickup device according to any one of the first to sixth aspects, a spherical aberration correction element is disposed in an optical path through which a light beam from the second light source passes. I do.
[0017]
According to a ninth aspect of the present invention, in the optical pickup device according to any one of the first to sixth aspects, a spherical aberration correction element is disposed in an optical path through which a light beam from the third light source passes. I do.
[0018]
According to a tenth aspect of the present invention, in the optical pickup device according to any one of the sixth to ninth aspects, the spherical difference correction element is a beam expander. It can correspond to the optical information recording medium of the type having.
[0019]
According to an eleventh aspect of the present invention, in the optical pickup device according to any one of the first to tenth aspects, an optical element having a negative refractive power is disposed in an optical path through which the second light flux passes. Therefore, the light beam from the first light source can be made incident on the objective lens in a state of a parallel light beam, and the light beam from the second light source can be made incident on the objective lens in a divergent state. Therefore, information can be recorded and / or reproduced more appropriately on each optical information recording medium. Incidentally, the optical element having a negative refractive power includes a diffractive element in addition to a concave lens.
[0020]
An optical pickup device according to a twelfth aspect is the optical pickup device according to any one of the first to eleventh aspects, wherein an optical path through which the light beam emitted from the first light source passes and a light beam emitted from the second light source are used. Two of an optical path that passes and an optical path through which a light beam emitted from the third light source passes are disposed on the same plane that intersects the optical axis of the objective lens, and the remaining optical paths are the two optical paths. It is characterized by being arranged at a predetermined distance from a point where the plane where the optical path is arranged and the optical axis of the objective lens intersect, so that the luminous flux emitted from the first light source is Two of the optical path, the optical path of the light beam emitted from the second light source, and the optical path of the light beam emitted from the third light source are arranged on the same plane that intersects the optical axis of the objective lens. So it passes through these two light paths Two light sources for emitting a beam, can be placed on the same plane, thereby obtaining a compact structure. Further, since the remaining optical paths are arranged at a predetermined distance from a point where the plane on which the two optical paths are arranged and the optical axis of the objective lens intersect, the remaining optical paths are Since the optical system from the light source that emits the light beam passing through to the crossing point can be a dedicated optical system, the optical system is more excellent in optical characteristics.
[0021]
The objective lens according to claim 13 is used for the optical pickup device according to any one of claims 1 to 12.
[0022]
In the present specification, in the narrow sense, the objective lens is a light condensing function that is arranged to face the optical information recording medium at the position closest to the optical information recording medium when the optical information recording medium is loaded in the optical pickup device. And, in a broad sense, together with the lens, a lens operable at least in the optical axis direction by an actuator. Therefore, in this specification, the numerical aperture NA of the optical element on the optical information recording medium side (image side) refers to the numerical aperture NA of the surface of the optical element closest to the optical information recording medium. Further, in the present specification, the required numerical aperture NA is a numerical aperture defined by the standard of each optical information recording medium, or the information of each optical information recording medium, according to the wavelength of the light source used. The numerical aperture of an objective lens having diffraction-limited performance capable of obtaining a spot diameter required for recording or reproduction is shown.
[0023]
Regarding the distinction between the inner region, the intermediate region, and the outer region of the objective lens, a diffraction structure, a NPS (Non Periodic Surface) structure, or the like is provided in the intermediate region and the outer region, and the intermediate region passes through the intermediate region. The luminous flux having the wavelength λ3 is flared, and the luminous flux having the wavelength λ2 and the luminous flux having the wavelength λ3 which have passed through the outer region are flare. Or the like, by blocking the transmission of the light beam of wavelength λ3 in the intermediate region and the outer region, and preventing the transmission of the light beam of wavelength λ2 in the outer region. Here, “flare” means that the wavefront aberration becomes 0.07λ1rms, 0.07λ2rms, or 0.07λ3rms or more when information is recorded or reproduced on the first, second, or third optical information recording medium. That means. In the case where a diffractive structure is used, the method also includes using different orders of diffracted light for at least one optical information recording medium when recording or reproducing information on the first, second, and third optical information recording media.
[0024]
In this specification, the first optical information recording medium refers to, for example, a high-density DVD-based optical disk, and the second optical information recording medium refers to a DVD-ROM, DVD-Video used for reproduction only, and reproduction. / Includes various DVD-type optical disks such as DVD-RAM, DVD-R, and DVD-RW that also serve as recording. The third optical information recording medium refers to a CD-type optical disc such as a CD-R or CD-RW. Incidentally, the thickness t1 of the protective layer of the first optical information recording medium and the thickness t2 of the protective layer of the second optical information recording medium may be t1 = t2 or t1 <t2. .
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 shows that information can be recorded / reproduced on / from a high-density DVD (also referred to as a first optical disc), a conventional DVD (also referred to as a second optical disc), and a CD (also referred to as a third optical disc). 1 is a schematic sectional view of an optical pickup device according to an embodiment of the present invention. FIG. 2 is a view of the configuration of FIG. 1 taken along line II-II and viewed in the direction of the arrow, and FIG. 3 is a view of the configuration of FIG. 1 taken along line III-III and viewed in the direction of the arrow. is there.
[0026]
In FIGS. 1 and 2, a light beam emitted from a first semiconductor laser 101 (wavelength λ1 = 380 nm to 450 nm) as a first light source is converted into a parallel light beam by a collimator (first collimator) 102, and then transmitted through a diffraction element 103. The beam passes through to generate a tracking error detection sub-beam, and the beam shape is corrected by a beam shaper (104, 105) composed of a prism, passes through a polarizing beam splitter 106, and enters a beam expander having optical elements 107, 108. I do. The beam expanders (107, 108) in which at least one (preferably, the optical element 107) is movable in the optical axis direction have a function of changing (here, enlarging) the beam diameter of the parallel beam. It should be noted that the beam expander is provided here, in addition to having a spherical aberration correction function, in the case of, for example, a high-density DVD of a type having two layers of information recording surfaces, the optical element 107 is moved in the optical axis direction. By doing so, the information recording surface can be selected. A similar beam expander may be arranged in an optical path through which light beams from the second semiconductor laser 201 and the third semiconductor laser 301 described later pass.
[0027]
In FIG. 1, a light beam transmitted through a beam expander (107, 108) is reflected by a rising mirror (reflection element) 109, and a light beam of wavelength λ1 is transmitted, but a light beam of wavelengths λ2 and 3 is reflected. An inner region, an intermediate region, and an outer region of an objective lens including two optical elements 113 and 114 in the form of a parallel light beam passing through a mirror (second wavelength selective element) 110, passing through a quarter-wave plate 111, and Through the protective layer (thickness t1 = 0.1 to 0.7 mm) of the first optical disc 115, and is focused on the information recording surface thereof to form a focused spot.
[0028]
The light flux modulated and reflected by the information pits on the information recording surface again passes through the objective lenses (114, 113), the quarter-wave plate 111, and the dichroic mirror 110, is reflected by the rising mirror 109, and is expanded by the beam expander. The light passes through (108, 107), is reflected by the polarization beam splitter 106, passes through the sensor lens 116, is given astigmatism by the cylindrical lens 117, and is incident on the light receiving surface of the photodetector 118. Using the signal, a signal for reading information recorded on the first optical disk 115 is obtained.
[0029]
Further, a change in the light amount due to a change in the shape and position of the spot on the photodetector 118 is detected, and focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 120 moves the objective lenses (113, 114) integrally so that the light beam from the first semiconductor laser 101 is focused on the information recording surface of the first optical disc 115. ing.
[0030]
In the present embodiment, a part of the light beam emitted from the first semiconductor laser 101 is reflected from the polarization beam splitter 106, collected by the condenser lens 121, and incident on the power sensor 122. Can monitor the laser power.
[0031]
1 and 3, a light beam emitted from a second semiconductor laser 201 (wavelength λ2 = 600 nm to 700 nm) as a second light source is converted into a parallel light beam by a collimator (second collimator) 202, and then a diffraction element 203, a tracking error detection sub-beam is generated, the beam shape is corrected by a beam shaper (204, 205) composed of a prism, passed through a polarization beam splitter 206, and then passed through a dichroic mirror (first wavelength selective element). ) 208.
[0032]
In FIG. 1, the light beam transmitted through the dichroic mirror 208 is reflected by the dichroic mirror 110, passes through the quarter-wave plate 111, passes through the concave lens 109 and becomes a divergent light beam, and passes through the two optical elements 113 and 114. The light flux passing through the inner region and the intermediate region of the objective lens (other than that, flare otherwise) passes through the protective layer (thickness t2 = 0.1 to 0.7 mm) of the second optical disk 115 '. The light is focused on the information recording surface to form a focused spot.
[0033]
The light flux modulated and reflected by the information pits on the information recording surface is reflected again by the objective lenses (114, 113), the quarter-wave plate 111, and the dichroic mirror 110, and passes through the concave lens 209 and the dichroic mirror 208. Is reflected by the polarization beam splitter 206, passes through the sensor lens 216, is given astigmatism by the cylindrical lens 217, and is incident on the light receiving surface of the photodetector 218. A read signal of the information recorded at 115 'is obtained.
[0034]
Further, a change in the light amount due to a change in the shape and position of the spot on the photodetector 218 is detected, and focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 120 moves the objective lenses (113, 114) integrally so that the light beam from the second semiconductor laser 201 is focused on the information recording surface of the second optical disc 115 '. Has become.
[0035]
In the present embodiment, a part of the light beam emitted from the second semiconductor laser 201 is reflected from the polarization beam splitter 206, is collected by the condenser lens 221 and is incident on the power sensor 222. Can monitor the laser power.
[0036]
Further, in FIG. 3, a light beam emitted from a third semiconductor laser 301 (wavelength λ3 = 770 nm to 830 nm), in which a hologram element and a light receiving element are integrated as a third light source, passes through a convex lens 302 and then becomes a dichroic mirror. Reflected at 208.
[0037]
In FIG. 1, a light beam transmitted through a dichroic mirror 208 passes through a concave lens 109, becomes a divergent light beam having a predetermined finite magnification, is reflected by a dichroic mirror 110, passes through a quarter-wave plate 111, and passes through two optical elements. The luminous flux that has passed only through the inner region of the objective lens composed of 113 and 114 (other portions are flared) passes through the protective layer (thickness t3 = 1.2 mm) of the third optical disk 115 ″ and its information recording surface. The convex lens 302 and the concave lens 109 constitute a coupling element.
[0038]
The light flux modulated and reflected by the information pits on the information recording surface is reflected again by the objective lenses (114, 113), the quarter-wave plate 111, and the dichroic mirror 110, passes through the concave lens 209, and is transmitted by the dichroic mirror 208. The light is reflected, passes through the convex lens 302, and returns to the original third semiconductor laser 301. The third semiconductor laser 301 incorporates a hologram element and a light receiving element (not shown) as an integrated package, and the returned light flux is diffracted by the hologram, enters the light receiving element, and uses the output signal to generate a third light. And a read signal of the information of the optical disk is obtained.
[0039]
In addition, a change in light amount due to a change in the shape and position of the spot on the light receiving element is detected, and focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 120 moves the objective lenses (113, 114) integrally so that the light beam from the third semiconductor laser 301 is focused on the information recording surface of the third optical disc 115 ″. Has become.
[0040]
In the optical pickup device of the present embodiment, as shown in FIG. 3, the axis (optical path) of the light beam emitted from the second semiconductor laser 201 and the axis (optical path) of the light beam emitted from the third semiconductor laser 301. Are arranged on the same plane that intersects the optical axis of the objective lens (113, 114). Further, as shown in FIG. 1, the axis (optical path) of the light beam emitted from the first semiconductor laser 101 is a plane on which the optical axes of the second semiconductor laser 201 and the third semiconductor laser 301 are arranged, and an objective lens. It is arranged at a predetermined distance Δ from a point P where the optical axis of (113, 114) intersects.
[0041]
In the present embodiment, the first semiconductor laser 101 to the dichroic mirror 110 form a first optical path, the second semiconductor laser 201 to the dichroic mirror 208 form a second optical path, and the third semiconductor laser 301 To the dichroic mirror 208 form a third optical path, the dichroic mirror 208 to the dichroic mirror 110 form a fourth optical path, and the dichroic mirror 110 to the optical disks 115, 115'115 "form a fifth optical path. That is, the present embodiment corresponds to the first aspect of the present invention.
[0042]
Further, according to the present embodiment, the second semiconductor laser 201 and the third semiconductor laser 301 can be installed on the same substrate (not shown), and the second semiconductor laser 201 and the third semiconductor laser 301 are attached. The first semiconductor laser 101 can be mounted on a substrate different from the substrate that has been used, so that a so-called two-layer structure can be obtained, and information can be recorded and / or reproduced on three different optical disks. Although it is possible, the configuration can be made compact. It goes without saying that the first semiconductor laser 101 may be mounted on the surface opposite to the surface of the substrate on which the second semiconductor laser 201 and the third semiconductor laser 301 are mounted.
[0043]
As described above, the present invention has been described with reference to the embodiments. However, the present invention should not be construed as being limited to the above embodiments, and it is needless to say that modifications and improvements can be made as appropriate. For example, the first semiconductor laser 101 and the second semiconductor laser 201 may be exchanged, or the first semiconductor laser 101 and the third semiconductor laser 301 may be exchanged. For example, a diffraction element having a similar function may be arranged instead of the concave lens 209. If the shape of the light beam emitted from the second semiconductor laser 201 is within an allowable range, it is not always necessary to provide the beam shapers (204, 205). Further, the substrate provided with the first semiconductor laser 101 and the like and the substrate provided with the second semiconductor laser 201 and the like are unitized, and after the components are assembled on the respective substrates, the substrates may be joined together. Good, thereby improving the assemblability.
[0044]
For example, a spherical aberration correction element having the same function as the beam expanders (107, 108) may be arranged in an optical path through which a light beam emitted from the second semiconductor laser 201 or the third semiconductor laser 301 passes. In this case, the number of components can be reduced by disposing in the optical path through which at least two of the light beams emitted from the three light sources pass.
[0045]
【The invention's effect】
According to the present invention, it is possible to provide an optical pickup device and an objective lens which are compact and can appropriately record and / or reproduce information on, for example, all of a high-density DVD and conventional DVDs and CDs.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an optical pickup device according to an embodiment of the present invention.
FIG. 2 is a view of the configuration of FIG. 1 cut along a line II-II and viewed in a direction of an arrow.
FIG. 3 is a view of the configuration of FIG. 1 cut along a line III-III and viewed in a direction of an arrow.
FIG. 4 is a schematic diagram showing an optical path from each light source in the optical pickup device according to the first embodiment.
FIG. 5 is a schematic diagram showing an optical path from each light source in the optical pickup device according to the second embodiment.
FIG. 6 is a schematic diagram showing an optical path from each light source in the optical pickup device according to the third embodiment.
[Explanation of symbols]
101 First semiconductor laser 107, 108 Beam expander 109 Start-up mirror 110 Dichroic mirror 113, 114 Objective lens 115, 115 ', 115 "Optical disk 201 Second semiconductor laser 308 Dichroic mirror 301 Third semiconductor laser

Claims (13)

A light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), a third light source having a wavelength λ3 (λ2 <λ3), and a condensing optical system including an objective lens; The optical system condenses the light beam from the first light source on the information recording surface of the first optical information recording medium via the protective layer having a thickness of t1, thereby performing information recording and / or reproduction. Recording and / or reproducing information by condensing a light beam from the second light source on the information recording surface of the second optical information recording medium via the protective layer having a thickness of t2. Further, the light flux from the third light source is collected on the information recording surface of the third optical information recording medium via a protective layer having a thickness t3 (t1 <t3 and t2 <t3). An optical pick that can record and / or reproduce information by illuminating A-up apparatus,
The objective lens is configured to perform recording and / or reproduction on the first optical information recording medium, the second optical information recording medium, and the third optical information recording medium, respectively. A light source, and an inner region centered on an optical axis through which light beams respectively emitted from the third light source pass in common to form a condensed spot on each information recording surface; When performing recording and / or reproduction on the information recording medium and the second optical information recording medium, respectively, the light beams emitted from the first light source and the second light source respectively pass through in common to record each information. When recording and / or reproducing from / to the first optical information recording medium and an intermediate area around the optical axis that forms a converging spot on the surface, the light is emitted from the first light source. Light beam passes through and collects on the information recording surface. And an outer region around the optical axis so as to form a spot,
A first optical path through which only the light emitted from the first light source passes, a second optical path through which only the light emitted from the second light source passes, and a third optical path through which only the light emitted from the third light source passes A fourth light path through which the light beam emitted from the second light source and the light beam emitted from the third light source pass in common; a light beam passing through the fourth light path; and a light beam passing through the first light path Has a fifth optical path that passes in common,
The optical pickup device, wherein the objective lens is disposed in the fifth optical path. A light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), a third light source having a wavelength λ3 (λ2 <λ3), and a condensing optical system including an objective lens; The optical system condenses the light beam from the first light source on the information recording surface of the first optical information recording medium via the protective layer having a thickness of t1, thereby performing information recording and / or reproduction. Recording and / or reproducing information by condensing a light beam from the second light source on the information recording surface of the second optical information recording medium via the protective layer having a thickness of t2. Further, the light flux from the third light source is collected on the information recording surface of the third optical information recording medium via a protective layer having a thickness t3 (t1 <t3 and t2 <t3). An optical pick that can record and / or reproduce information by illuminating A-up apparatus,
The objective lens is configured to perform recording and / or reproduction on the first optical information recording medium, the second optical information recording medium, and the third optical information recording medium, respectively. A light source, and an inner region centered on an optical axis through which light beams respectively emitted from the third light source pass in common to form a condensed spot on each information recording surface; When performing recording and / or reproduction on the information recording medium and the second optical information recording medium, respectively, the light beams emitted from the first light source and the second light source respectively pass through in common to record each information. When recording and / or reproducing from / to the first optical information recording medium and an intermediate area around the optical axis that forms a converging spot on the surface, the light is emitted from the first light source. Light beam passes through and collects on the information recording surface. And an outer region around the optical axis so as to form a spot,
A first optical path through which only the light emitted from the first light source passes, a second optical path through which only the light emitted from the second light source passes, and a third optical path through which only the light emitted from the third light source passes A fourth light path through which a light beam emitted from the first light source and a light beam emitted from the second light source pass in common; a light beam passing through the fourth light path; and a light beam passing through the third light path Has a fifth optical path that passes in common,
The optical pickup device, wherein the objective lens is disposed in the fifth optical path. A light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), a third light source having a wavelength λ3 (λ2 <λ3), and a condensing optical system including an objective lens; The optical system condenses the light beam from the first light source on the information recording surface of the first optical information recording medium via the protective layer having a thickness of t1, thereby performing information recording and / or reproduction. Recording and / or reproducing information by condensing a light beam from the second light source on the information recording surface of the second optical information recording medium via the protective layer having a thickness of t2. Further, the light flux from the third light source is collected on the information recording surface of the third optical information recording medium via a protective layer having a thickness t3 (t1 <t3 and t2 <t3). An optical pick that can record and / or reproduce information by illuminating A-up apparatus,
The objective lens is configured to perform recording and / or reproduction on the first optical information recording medium, the second optical information recording medium, and the third optical information recording medium, respectively. A light source, and an inner region centered on an optical axis through which light beams respectively emitted from the third light source pass in common to form a condensed spot on each information recording surface; When performing recording and / or reproduction on the information recording medium and the second optical information recording medium, respectively, the light beams emitted from the first light source and the second light source respectively pass through in common to record each information. When recording and / or reproducing from / to the first optical information recording medium and an intermediate area around the optical axis that forms a converging spot on the surface, the light is emitted from the first light source. Light beam passes through and collects on the information recording surface. And an outer region around the optical axis so as to form a spot,
A first optical path through which only the light emitted from the first light source passes, a second optical path through which only the light emitted from the second light source passes, and a third optical path through which only the light emitted from the third light source passes A fourth light path through which the light beam emitted from the first light source and the light beam emitted from the third light source pass in common; a light beam passing through the fourth light path; and a light beam passing through the second light path And a fifth optical path that passes in common,
The optical pickup device, wherein the objective lens is disposed in the fifth optical path. 4. The optical pickup device according to claim 1, wherein axes of the at least two light beams coincide with each other in the optical path through which at least two light beams pass. 5. The optical pickup device according to claim 1, wherein a 板 wavelength plate is disposed in the fifth optical path. The optical pickup device according to claim 1, wherein a chromatic aberration correction element is disposed in the fifth optical path. 7. The optical pickup device according to claim 1, wherein a spherical aberration correction element is arranged in an optical path through which a light beam from the first light source passes. 7. The optical pickup device according to claim 1, wherein a spherical aberration correction element is arranged in an optical path through which a light beam from the second light source passes. 7. The optical pickup device according to claim 1, wherein a spherical aberration correction element is disposed in an optical path through which a light beam from the third light source passes. 10. The optical pickup device according to claim 7, wherein the spherical difference correction element is a beam expander. 11. The optical pickup device according to claim 1, wherein an optical element having a negative refractive power is arranged in an optical path through which the second light beam passes. Two of an optical path through which a light beam emitted from the first light source passes, an optical path through which a light beam emitted from the second light source passes, and an optical path through which a light beam emitted from the third light source passes, Are arranged on the same plane crossing the optical axis of the objective lens,
The remaining optical paths are arranged at a predetermined distance from a point where the plane on which the two optical paths are arranged and the optical axis of the objective lens intersect. 11 optical pickup device. An objective lens used in the optical pickup device according to claim 1.

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