JP2006004547A - Optical pickup and disk-like optical recording medium recording and reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize an optical pickup consisting of a plurality of objective lenses and a plurality of rising mirrors corresponding to a plurality of kinds of media. <P>SOLUTION: A reflecting surface 201 of the rising mirror 251 is a pentagon in the shape of a figure projected to a plane parallel to the recording surface of an optical disk and a reflecting surface 203 of the rising mirror 252 is a pentagon in the shape of the figure projected to the plane parallel to the recording surface of the optical disk. The rising mirror 251 and the rising mirror 252 are combined by adjoining a portion of a segment ab<SB>1</SB>and a portion of a segment ab<SB>2</SB>and are lined up in such a manner the condensing spot by the first objective lens and the condensing spot by the second objective lens are aligned to the recording track direction of the optical disk. The rising mirror 251 changes the optical axis of the light beam made incident from the direction angular to the recording track direction 5 to an approximately perpendicular direction and guides the light to the first objective lens. The rising mirror 252 changes the optical axis of the light beam made incident from the direction angular to the recording track direction to the approximately perpendicular direction and guides the light to the second objective lens. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is an optical system for recording / reproducing an optical recording medium, and includes a light beam having a different recording / reproducing wavelength and a plurality of objective lenses having different numerical apertures, and writing and reading are performed on a plurality of recording media. The present invention relates to an optical pickup and an optical recording medium recording / reproducing apparatus that can be used.

  In recent years, recording media such as CD (Compact Disc), MD (Mini Disc), and DVD (Digital Versatile Disc) have been required to have a larger capacity, and various technologies have been developed to increase the capacity. Yes. In addition, it is required that various data such as music content data, video content data, and data for computer use can be freely recorded and reproduced on one medium. In particular, a new disc format (hereinafter referred to as a Blu-ray disc; BD) using a laser having a wavelength band of 405 nm has attracted much attention as a next-generation recording technology.

  When developing media for general use, compatibility and consistency between new and old media recording and playback devices are also important. Newly developed recording and playback devices can use legacy assets such as DVDs and CDs. It is preferable that However, it is not easy to design a device having compatibility between media having different disk structures and accompanying laser specifications.

  The simplest method is to provide a different optical system for each media specification and switch the dedicated objective lens for each wavelength used. For example, Patent Document 1 discloses a technique that enables reproduction of a plurality of optical recording media having different specifications by switching objective lenses having different numerical apertures. However, a plurality of types of light sources and an optical system switching mechanism for each wavelength lead to an increase in cost. Further, since the actuator is enlarged, it is disadvantageous for downsizing the apparatus.

  Therefore, a method is adopted in which a plurality of wavelength compatible optical systems sharing some optical systems, photodetectors, and the like are used. For example, these two beams are emitted as a two-wavelength compatible optical system of a DVD (Digital Versatile Disc) using the wavelength 655 nm band as recording / reproducing light and a CD (Compact Disc) using the wavelength 785 nm band as recording / reproducing light. An optical pickup using a so-called 1CAN 2 wavelength laser in which a laser element is provided in one package has been proposed.

  In such a two-wavelength compatible optical system sharing a part of the optical system, for example, spherical aberration proportional to the thickness of the protective substrate protecting the recording surface of the recording medium is generated. In the shared configuration, spherical light aberration caused by the thickness of the protective substrate when the DVD light beam is condensed on the DVD recording surface by the objective lens, and the CD light beam is recorded on the CD by the objective lens. It becomes difficult to design a sharable objective lens that can correct the spherical aberration caused by the thickness of the protective substrate when focused on the surface.

  Therefore, the optical beam imaging apparatus includes two objective lenses having different numerical apertures and a light source for emitting DVD and CD light beams, and according to the thickness of the protective substrate of the optical recording medium, that is, A technique for selecting an objective lens by a simple method depending on whether it is a CD or a DVD has been proposed (see Patent Document 2).

  When trying to realize a three-wavelength compatible optical system between a DVD and a CD and, for example, the above-mentioned new format BD, all three combinations of protective substrate thicknesses and wavelengths that need to be optimized It becomes more difficult to design an optical system optimized for the wavelength.

  As described above, since the two-wavelength compatible optical system between the DVD and the CD has been achieved, there is a method for dealing with three wavelengths by combining the two-wavelength compatible optical system + 1 wavelength optical system. For example, a CD / DVD two-wavelength compatible optical system and a BD single optical system are provided. However, in this method, it is important to consider the arrangement of the two-wavelength compatible optical system and the one-wavelength optical system, and the spatial interference of the condensing unit including the objective lens and the rising mirror in both optical systems. Conventionally, a certain distance is opened between the two objective lenses, which hinders downsizing.

Japanese Patent No. 3495123 Japanese Patent Laid-Open No. 11-134697

  The present invention has been made in view of the above-described conventional situation, and reduces the size of a condensing unit composed of an objective lens and an optical axis changing unit corresponding to a plurality of light beams and different types of light beams. An object of the present invention is to provide an optical pickup capable of being stably guided from different directions and a disc-shaped optical recording medium recording / reproducing apparatus using the optical pickup.

  In order to achieve the above-described object, an optical pickup according to the present invention is an optical pickup in which recording / reproduction with respect to individual disk-shaped optical recording media having different protective substrate thicknesses is performed using light beams having different wavelengths and numerical apertures. A first light source that emits a first light beam having a wavelength of 1, a second light source that emits a second light beam having a second wavelength, and a third light beam having a third wavelength , A first objective lens for condensing the first light beam and the second light beam on the recording surface of the disk-shaped optical recording medium, and a third light beam for the disk-shaped optical The second objective lens for focusing on the recording surface of the recording medium, and the optical axes of the first and second light beams incident along a plane parallel to the recording surface of the disk-shaped optical recording medium are approximately First up in the vertical direction First optical axis changing means having a reflective surface and a second reflection that raises the optical axis of the third light beam incident along a plane parallel to the recording surface of the disc-shaped optical recording medium in a substantially vertical direction. A second optical axis changing means having a surface; and a light receiving means for receiving the reflected beam reflected by the disk-shaped optical recording medium and converting it into an electrical signal.

  In the optical pickup according to the present invention, the first reflecting surface of the first optical axis changing means has a projected shape projected on a plane parallel to the recording surface of the disc-shaped optical recording medium, one side being a1 and the other side. Is a pentagon that can be separated by a first line segment connecting one point on one side and one point on the other side of the rectangle with b1 as the first optical axis changing means in the second optical axis changing means. The reflection surface 2 has a rectangular shape in which the projected shape projected onto a plane parallel to the recording surface of the disc-shaped optical recording medium has one side a2 and the other side b2 is a point on one side. It is a pentagon that can be separated by a second line segment connecting one point on the other side. The first optical axis changing unit and the second optical axis changing unit are combined so that a part of the first line segment and a part of the second line segment are in contact with each other on the projection plane.

  Further, the first optical axis changing means causes the first reflecting surface to cause the first light beam and the second light beam incident from a direction forming a first angle with respect to the tangential direction of the disc-shaped recording medium. The optical axis is changed in a direction substantially perpendicular to the traveling direction of the light beam and guided to the first objective lens, and the second optical axis changing means includes the first light beam and the second light beam. Are incident in a direction perpendicular to the traveling direction of the light beam by the second reflecting surface. Is changed and guided to the second objective lens.

  Further, the first optical axis changing means and the first objective lens located immediately above the first optical axis changing means and the second optical axis changing means and the second objective lens located immediately above it are condensed by the first objective lens. The spot and the condensing spot by the second objective lens are arranged side by side along the recording track direction of the disc-shaped optical recording medium.

  This optical pickup has a pentagonal figure center which is a projection shape in which the first angle is an angle θ and the first reflecting surface is projected onto a plane parallel to the recording surface of the disc-shaped optical recording medium, and the second reflecting surface. When the distance between the center of the pentagonal figure, which is the projection shape projected onto the plane parallel to the recording surface of the disk-shaped optical recording medium, is the distance d, dsin θ <(a1 + b2) / 2 is satisfied. The sum of the first angle and the second angle is preferably 90 degrees.

  In order to achieve the above-described object, a disk-shaped optical recording medium recording / reproducing apparatus according to the present invention includes a first light source that emits a first light beam having a first wavelength, and a second light source having a second wavelength. A second light source that emits a second light beam, a third light source that emits a third light beam having a third wavelength, and a first optical beam and a second optical beam into a disk-shaped optical recording medium A first objective lens that focuses light on the recording surface, a second objective lens that focuses the third light beam on the recording surface of the disk-shaped optical recording medium, and a recording surface of the disk-shaped optical recording medium. First optical axis changing means having a first reflecting surface for raising the optical axes of the first light beam and the second light beam incident along parallel planes in a substantially vertical direction, and a disc-shaped optical recording medium The optical axis of the third light beam incident along a plane parallel to the recording surface of An optical pickup comprising: a second optical axis changing unit having a second reflecting surface that rises in a vertical direction; and a light receiving unit that receives a reflected beam reflected by the disk-shaped optical recording medium and converts it into an electrical signal. Have. The first reflecting surface provided in the first optical axis converting means in this optical pickup has a projected shape projected on a plane parallel to the recording surface of the disc-shaped optical recording medium, one side being a1 and the other side being A pentagon which is formed by separating one corner of a rectangle b1 by a first line segment connecting one point on one side and one point on the other side, and is provided in the second optical axis conversion means. The second reflecting surface is a point on one side of one corner of a rectangle in which the projected shape projected on a plane parallel to the recording surface of the disc-shaped optical recording medium has one side a2 and the other side b2. And a pentagon that can be separated by a second line segment that connects one point on the other side. The first optical axis changing unit and the second optical axis changing unit are combined so that a part of the first line segment and a part of the second line segment are in contact with each other on the projection plane.

  The first optical axis changing means is configured to cause the first light beam and the second light beam incident from a direction forming a first angle with respect to the tangential direction of the disk-shaped recording medium to be reflected by the first reflecting surface. The optical axis is changed in a substantially vertical direction with respect to the beam traveling direction and guided to the first objective lens, and the second optical axis changing means is different from the first light beam and the second light beam. The optical axis of the third light beam that is incident from the direction that is at the second angle with respect to the tangential direction is changed by the second reflecting surface in a direction substantially perpendicular to the traveling direction of the light beam. Then, the light is guided to the second objective lens.

  The first optical axis changing means and the first objective lens located immediately above the second optical axis changing means and the second objective lens located immediately above the first optical axis changing means are a condensing spot by the first objective lens. The condensing spot by the second objective lens is arranged in parallel along the recording track direction of the disc-shaped optical recording medium.

  In the disk-shaped optical recording medium recording / reproducing apparatus according to the present invention, the optical pickup has a projection shape in which the first angle is an angle θ and the first reflecting surface is projected onto a plane parallel to the recording surface of the disk-shaped optical recording medium. When the distance between a pentagonal figure center and a pentagonal figure center which is a projection shape obtained by projecting the second reflecting surface onto a plane parallel to the recording surface of the disc-shaped optical recording medium is a distance d, It satisfies dsin θ <(a1 + b2) / 2. The sum of the first angle and the second angle is preferably 90 degrees.

  According to the present invention, when a combination of a two-wavelength compatible optical system + a one-wavelength optical system is used for three wavelengths, a condensing unit composed of an objective lens and an optical axis changing unit corresponding to the two-wavelength compatible optical system and one wavelength It is possible to reduce the size of the connecting portion with the condensing unit corresponding to the optical system, and to stably guide different types of light beams from different directions.

  Hereinafter, specific examples of the optical pickup according to the present invention will be described in detail with reference to the drawings. First, an optical system of an optical pickup 1 shown as a first specific example of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of the optical pickup 1 viewed from a direction perpendicular to the recording surface of the optical disc. FIG. It is sectional drawing seen from the parallel direction.

  In this specific example, as an example, the first optical disc 91 uses a light beam 94 having a wavelength of 405 nm as a recording / reproducing light, a Blu-ray disc (hereinafter referred to as BD), and the second optical disc 92 has a light beam 95 having a wavelength of 655 nm. An optical pickup having a three-wavelength compatible optical system such as a DVD (Digital Versatile Disc) that uses as a recording / reproducing light and a third optical disc 93 that uses a light beam 96 having a wavelength of 785 nm as a recording / reproducing light. To do. Note that the first protective substrate thickness of the first optical disc 91 that is a BD is 0.1 mm, the second protective substrate thickness of the second optical disc 92 that is a DVD is 0.6 mm, and the first protective substrate is a CD. The third protective substrate thickness of the third optical disc 93 is 1.2 mm.

  The optical pickup 1 includes a first optical system 10a having a light source and a lens group of a light beam 94, which is a BD recording / reproducing light, a light beam 95, which is a DVD recording / reproducing light, and a light beam 96, which is a CD recording / reproducing light. And a second optical system 10b having a light source for emitting light beams of two different wavelengths and a lens group adapted to the two different wavelengths.

  The optical pickup 1 includes a light source unit 11 that emits a light beam 94 having a wavelength of 405 nm, and a diffraction grating 13 that branches the light beam emitted from the light source unit 11 into a main beam and a sub beam as an outward optical system of the first optical system 10a. The collimating lens 15 for converting the divergent light beam into a parallel light beam, the beam splitter 17 for branching the outgoing light and the return light, the light receiving element 19 for adjusting the outgoing light beam, and the diameter of the outgoing light beam transmitted through the beam splitter 17. An expander 21 that expands and a collimator lens 23 that converts the light beam transmitted through the expander 21 into parallel light again.

  Further, as shown in FIG. 2, the optical pickup 1 raises the optical axis of the light beam 94 incident along a plane parallel to the recording surface of the optical disc in a substantially vertical direction and guides it to the first objective lens 29. A rising mirror 251 having a reflecting surface, a λ / 4 plate 27 for converting the linearly polarized light beam 94 whose optical axis has been changed by the rising mirror 251 into circularly polarized light, and light positioned directly above the rising mirror 251. And a first objective lens 29 that condenses the beam 94 on the BD recording surface. The rising mirror 251 forms a beam rising portion 25 in combination with a rising mirror 252 to be described later. Details of the rising mirror 251 will be described later.

  Further, the optical pickup 1 is a return optical system of the first optical system, on the BD recording surface of the light beam 94 and the condenser lens 31 that collects the return light branched from the emitted light by the beam splitter 17. A condenser lens 33 that condenses the reflected return light on the photodetector, and a photodetector 35 that receives the reflected light and converts it into an electrical signal.

  In the first optical system 10a, the light source unit 11 is a light source for recording / reproducing light for BD applied in this specific example, and includes a first laser element (not shown). The first laser element emits a linearly polarized light beam 94 having a wavelength of 405 nm for BD recording / reproduction as a first wavelength.

  The diffraction grating 13 transmits the light beam emitted from the light source unit 11 and branches it into a main beam and a sub beam. The light beam transmitted through the diffraction grating 13 is converted into parallel light by the collimator lens 15 and enters the beam splitter 17. The beam splitter 17 transmits the P-polarized component and reflects the S-polarized component of the incident light beam. The reflected S-polarized light component enters the light receiving element 19 for adjusting the light beam. The expander 21 expands the beam diameter of the P-polarized component transmitted through the beam splitter 17. The collimating lens 23 converts the light beam whose diameter is enlarged again into parallel light. The light beam 94 reflected by the reflection surface of the rising mirror 251 is condensed on the recording surface of the BD via the first objective lens 69.

  The first objective lens 29 can focus a light beam 94 having a first wavelength on a BD as a first optical disk having a first protective substrate thickness 91a. The numerical aperture of the first objective lens 29 is 0.85. The first objective lens 29 includes a diffractive element 291 for correcting spherical aberration caused by a protective substrate thickness error that protects the recording surface of the BD. As the diffractive element 291, for example, a blazed diffractive element having a sawtooth cross section with respect to the transmitting optical axis and NA of 0.85 can be used. In the optical pickup 1, the first objective lens 29 and the diffraction element 291 are fixed to each other and driven by one actuator.

  Next, the second optical system 10b of the optical pickup 1 will be described. The optical pickup 1 includes, as an outward optical system of the second optical system 10b, a light source unit 12 that emits light beams having different wavelengths, and a diffraction grating 14 that branches the light beam emitted from the light source unit 12 into a main beam and a sub beam. The light beam passes through the collimating lens 24 for converting the divergent light beam into a parallel light beam, the first beam splitter 18 for branching the outgoing light and the return light, the light receiving element 20 for adjusting the outgoing light beam, and the first beam splitter 18. An expander 22 that expands the outgoing light beam diameter, and a collimator lens 24 that converts the light beam transmitted through the expander 22 into parallel light again.

  Further, the optical pickup 1 has a light beam 95 incident on a plane parallel to the recording surface of the optical disk and a reflecting surface that guides the light beam 96 to the second objective lens 28 by raising the optical axis of the light beam 96 in a substantially vertical direction. , A λ / 4 plate 26 for converting the linearly polarized light beam 95 and the light beam 96 whose optical axes are changed by the rising mirror 252 to circularly polarized light, and the rising mirror 252. And a second objective lens 28 for condensing the light beam 95 on the DVD recording surface and the light beam 96 on the CD recording surface. The raising mirror 252 is combined with the raising mirror 251 to form the beam raising portion 25. Details of the rising mirror 252 will be described later.

  Further, the optical pickup 1 is a return optical system of the second optical system 10b, and a condensing lens 30 for condensing the return light branched from the emitted light by the first beam splitter 18 and a light beam according to the type. A second beam splitter 32 for guiding the light beam to the light detector, a condenser lens 34 for condensing the return light reflected on the DVD recording surface of the light beam 95 on the light detector, and receiving the reflected light. A light detector 36 for converting the light beam 96 into an electric signal; a polarizing optical element 38 for compensating the aberration of the light beam 96; and a light detector 40 for receiving the return light of the light beam 96 and converting it into an electric signal.

  The light source unit 12 is a so-called 1 CAN two-wavelength laser (hereinafter referred to as a two-beam LD) in which a light source for recording / reproducing light for DVD and a light source for recording / reproducing light for CD applied in this specific example are provided in one package. And a second laser element and a third laser element (not shown). The second laser element emits a linearly polarized light beam 95 having a wavelength of 655 nm for DVD recording / reproduction as the second wavelength. Further, the third laser element emits a linearly polarized light beam 96 having a wavelength of 785 nm for CD recording / reproduction as a third wavelength.

  The diffraction grating 14 transmits the light beam emitted from the light source unit 12 and branches it into a main beam and a sub beam. The light beam that has passed through the diffraction grating 14 is converted into parallel light by the collimator lens 24 and is incident on the first beam splitter 18. The first beam splitter 18 transmits the P-polarized component of the incident light beam and reflects the S-polarized component. The reflected S-polarized light component enters the light receiving element 20 for adjusting the light beam. The expander 22 expands the beam diameter of the P-polarized component transmitted through the first beam splitter 18. The collimating lens 24 converts the light beam whose diameter is enlarged again into parallel light. The light beam 95 and the light beam 96 reflected by the reflecting surface of the rising mirror 252 are condensed on the recording surface of the DVD or CD via the second objective lens 28.

  The second objective lens 28 is a so-called two-zone lens, and applies a light beam 95 having a second wavelength to a DVD as a second disk having a second protective substrate thickness 92a. The light beam 96 having the third wavelength can be focused on the CD as the third optical disk having the protective substrate thickness 93a. The numerical aperture of the second objective lens 28 is 0.60 for the second wavelength and 0.45 for the third wavelength. The second objective lens 28 includes a diffraction element 281 for correcting spherical aberration caused by a protective substrate thickness error that protects the recording surface of a DVD or CD. As the diffractive element 281, for example, a blazed diffractive element having a sawtooth cross section with respect to the transmitting optical axis and having an NA of 0.6 can be used. In the optical pickup 1, the second objective lens 28 and the diffraction element 281 are fixed to each other and driven by one actuator.

  The optical pickup 1 has a structure in which a first optical system 10a and a second optical system 10b, which are separately arranged, are connected by a beam rising portion 25, and a rising mirror 251 and a first objective lens 69, The rising mirror 252 and the second objective lens 28 are incorporated in the same unit.

  Hereinafter, the arrangement of the raising mirror 251 and the raising mirror 252 in the beam raising unit 25 in the optical pickup 1 will be described with reference to FIGS.

  The raising mirror 251 and the raising mirror 252 may be configured such that the reflector is installed at an angle that changes the optical axis of the light beam in a substantially vertical direction, or the optical axis of the light beam is changed in a substantially vertical direction. It may be an optical prism having a reflecting surface. In the case of a reflecting plate, the above-described projection surfaces 202 and 204 of the reflecting surface are projected figures of the reflecting plate, and in the case of an optical prism, the above-described projection surfaces 202 and 204 mean the bottom shape of the optical prism. Here, a description will be given using a projection plane in consideration of the case of a reflector.

As shown in FIG. 3A, the rising mirror 251 has a reflecting surface 201, and the shape of the projection surface 202 obtained by projecting the reflecting surface 201 onto a plane parallel to the optical disk recording surface is such that one side is a1 and the other is The basic shape is a rectangle whose side is b1. Raising mirror 251, from the basic shape, and the point _{P a1} and the point _{P b1} in a plane perpendicular to the line segment ab ₁ connecting the points _{P b1} on the point _{P a1} and edges b1 on the side a1 of the projection plane 202 It is a shape that can be made by cutting the apex between. Therefore, the projection shape obtained by projecting the raising mirror 251 onto a plane parallel to the optical disk recording surface is a pentagon.

Further, as shown in FIG. 3B, the rising mirror 252 has a reflecting surface 203, and the shape of the projection surface 204 obtained by projecting the reflecting surface 203 on a plane parallel to the optical disc recording surface is set to one side a2. The basic shape is a rectangle having the other side b2. Raising mirror 252, from the basic shape, and the point _{P a2} and a point _{P b2} in a plane perpendicular to the line segment ab ₂ connecting the points _{P b2} on point _{P a2} and edges b2 on the side a2 of the projection plane 204 It is a shape that can be made by cutting the apex between. Therefore, the projection shape obtained by projecting the rising mirror 252 onto a plane parallel to the optical disk recording surface is a pentagon.

Then, as shown in FIG. 4, the beam raising unit 25 of the optical pickup 1 includes a raising mirror 251 and a raising mirror 252 that are part of the line segment ab ₁ and part of the line segment ab _{2 on} the projection plane. Are combined to touch.

  FIG. 5 shows a state where the beam condensing portion with respect to the recording surface of the optical pickup 1 is viewed from a plane parallel to the recording surface of the optical disk. The x axis shown in FIG. 5 coincides with the radial direction of the optical disc, the y axis coincides with the recording track direction, that is, the tangential direction of the optical disc, and the z axis coincides with the perpendicular direction of the recording surface of the optical disc. FIG. 2 described above is a cross-sectional view of the objective lens and the light beam separation rising portion as seen from the direction of arrow A shown in FIGS. 4 and 5.

  The raising mirror 251 is provided so that the light beam 94 is incident from a direction that forms an angle θ with respect to the tangential direction, and the light beam 94 is substantially perpendicular to the traveling direction of the light beam 94 by the reflecting surface 201. The optical axis is changed in the direction, and the light is guided to the first objective lens 29 provided immediately above the rising mirror 251. Further, the rising mirror 252 makes the light beam 95 and the light beam 96 emitted from the same light source unit 12 enter from a direction different from the incident direction of the light beam 94 and at an angle φ with respect to the tangential direction. The optical axis is changed in a substantially vertical direction with respect to the traveling direction of the light beam by the reflecting surface 203, and the light is guided to the second objective lens 28 provided immediately above the rising mirror 252. It has become.

  The rising mirror 251 and the first objective lens 29 positioned immediately above the rising mirror 251 and the second objective lens 28 positioned immediately above the rising mirror 252 and the second objective lens 28 positioned directly above the mirror 251 are mutually connected by a lens holder 97 shown by a broken line in FIG. The condensing spot by the first objective lens 29 and the condensing spot by the second objective lens 28 are juxtaposed along the optical disc recording track direction. Further, the lens holder 97 is translationally driven in the focus direction and the tracking direction by an objective lens driving unit (not shown in FIG. 5).

  Here, when the distance between the graphic center of the projection surface 202 of the reflection surface 201 and the graphic center of the projection surface 204 of the reflection surface 203 is a distance d, d satisfies the relationship dsin θ <(a1 + b2) / 2. Determine the angle θ. At this time, the sum of the angle θ and the angle φ is preferably 90 degrees.

  In the optical pickup 1 having the configuration described above, the linearly polarized beam emitted from the light source unit 11 in the first optical system 10 a passes through the diffraction element 13 and is branched into the main beam and the two sub beams, and is collimated by the collimator lens 15. It is converted into a light beam and enters the beam splitter 17. The P-polarized light beam incident on the beam splitter 17 is transmitted approximately 100%, passes through the expander 21, is expanded in beam diameter, and is converted back to parallel light by the collimator lens 23. In the first optical system 10 a corresponding to the light beam 94, the P-polarized light beam 94 is changed in optical axis by the rising mirror 251 and is incident on the λ / 4 plate 27. Here, the light beam which has been P-polarized light is converted into circularly polarized light. The circularly polarized light beam 94 is condensed on the recording surface of the optical disc 91 by the first objective lens 29.

  The light beam 94 reflected on the recording surface is transmitted through the first objective lens 29 and the λ / 4 plate 27 to become linearly polarized light, the optical axis is changed by the rising mirror 251, and the light detector 94 by the condenser lens 33. 35 is collected.

  On the other hand, in the second optical system 10 b of the optical pickup 1, a light beam 95 for DVD recording / reproducing having a wavelength of 655 nm or a light beam 96 for CD recording / reproducing having a wavelength of 785 nm is irradiated from the light source unit 12. The light is transmitted and branched into a main beam and two sub beams, converted into a parallel light beam by the collimating lens 16, and incident on the first beam splitter 18. The P-polarized light beam that has entered the first beam splitter 18 is transmitted approximately 100%, passes through the expander 22, is expanded in beam diameter, and is converted back to parallel light by the collimator lens 24. In the second optical system 10 b corresponding to the light beam 95 or the light beam 96, the P-polarized light beam 95 or the light beam 96 is changed in optical axis by the rising mirror 252 and enters the λ / 4 plate 26. Here, the light beam which has been P-polarized light is converted into circularly polarized light. The circularly polarized light beam 95 or light beam 96 is condensed on the recording surface of the optical disk 92 or the optical disk 93 by the second objective lens 28.

  The light beam 95 or light beam 96 reflected on the recording surface is transmitted through the second objective lens 28 and the λ / 4 plate 26 to become linearly polarized light, and the optical axis is changed by the rising mirror 252. If the light beam is a DVD recording / reproducing light beam 95 having a wavelength of 655 nm, the light beam is reflected by the second beam splitter 73 and condensed on the photodetector 36 by the condenser lens 34. When the light beam is a CD recording / reproducing light beam 96 having a wavelength of 785 nm, the light beam passes through the second beam splitter 73, passes through the polarizing optical element 38, and is collected on the photodetector 40.

  According to the optical pickup 1 shown as a specific example of the present invention, the projection shape when the rising mirror 251 and the reflecting surface of the rising mirror 252 are projected onto a plane parallel to the recording surface of the optical disc is a pentagon. In addition, the distance d between the figure center of the projection figure of the reflection surface 201 and the figure center of the projection figure of the reflection surface 203 satisfies dsin θ <(a1 + b2) / 2, thereby The size can be reduced, and different types of light beams can be stably guided from different directions.

  In the optical pickup 1 described above, an optical system in which a BD light source and a lens group are configured independently and an optical system in which a DVD and CD light source and lens group are optimized are used. However, a CD light source and lens group are used. And an optical system in which the light source and lens group for DVD and BD are optimized may be used.

  An optical system of an optical pickup 2 shown as a second specific example of the present invention will be described with reference to FIGS. In the example described with reference to FIGS. 6 and 7, the characteristics of the objective lens differ depending on the combination of light beams having different wavelengths to be adapted, but basically the lens configuration shown in FIG. 1 can be applied.

  As in the previous example of the optical pickup 2 shown as the second specific example, the first optical disc 91 uses a light beam 94 having a wavelength of 405 nm as recording / reproducing light, and is referred to as a BD, a second optical disc. Three-wavelength compatible with a DVD (Digital Versatile Disc) 92 using a light beam 95 having a wavelength of 655 nm as recording / reproducing light, and a CD (Compact Disc) having a third optical disk 93 using a light beam 96 having a wavelength of 785 nm as recording / reproducing light. Has an optical system.

  The optical pickup 2 includes a light source that emits light beams having two different wavelengths, that is, a light beam 94 that is BD recording / reproducing light and a light beam 95 that is DVD recording / reproducing light, and a lens group that is adapted to two different wavelengths. A first optical system 50a and a first optical system 50b having a light source and a lens group of a light beam 96 which is a CD recording / reproducing light are configured.

  The optical pickup 2 is emitted from the light source unit 51 as a forward optical system of the first optical system 50a and a light source unit 51 that emits light beams having different wavelengths of a light beam 94 having a wavelength of 405 nm and a light beam 95 having a wavelength of 655 nm. A diffraction grating 53 that branches the light beam into a main beam and a sub beam, a collimator lens 55 that converts a divergent light beam into a parallel light beam, a first beam splitter 57 that branches outgoing light and return light, and an outgoing light beam adjustment A light receiving element 59, an expander 61 that expands the diameter of the outgoing light beam that has passed through the first beam splitter 57, and a collimator lens 63 that converts the light beam that has passed through the expander 61 into parallel light again.

  Further, the optical pickup 2 is a reflecting surface that guides the light beam 94 or the light beam 95 incident along a plane parallel to the recording surface of the optical disc to the first objective lens 69 by raising the optical axis of the light beam 94 in a substantially vertical direction. , A λ / 4 plate 67 for converting the linearly polarized light beam 94 or the light beam 95 whose optical axis has been changed by the rising mirror 251 into circularly polarized light, and the rising mirror 251. A first objective lens 69 for condensing the light beam 94 on the BD recording surface and the light beam 95 on the DVD recording surface; As the raising mirror, the above-described beam raising unit 25 formed by combining the raising mirrors 251 and 252 can be used.

  Further, the optical pickup 2 is a return optical system of the first optical system 50a, and a condensing lens 71 for condensing the return light branched from the emitted light by the first beam splitter 57, and the light beam according to the type. A second beam splitter 73 for guiding the light beam to the photodetector, a condenser lens 75 for condensing the return light reflected on the BD recording surface of the light beam 94 on the photodetector, and receiving the reflected light. A light detector 77 for converting the light beam 95 into an electric signal; a polarizing optical element 79 for compensating for aberration of the light beam 95; and a light detector 81 for receiving the return light of the light beam 95 and converting it into an electric signal.

  In the first optical system 50a, the light source unit 51 includes a so-called 1CAN two-wavelength laser in which a light source for recording / reproducing light for BD and a light source for recording / reproducing light for DVD, which are applied in this specific example, are provided in one package. Hereinafter, it is referred to as a two-beam LD.), Which includes a first laser element and a second laser element (not shown). The first laser element emits a linearly polarized light beam 94 having a wavelength of 405 nm for BD recording / reproduction as a first wavelength. The second laser element emits a linearly polarized light beam 95 having a wavelength of 655 nm for DVD recording / reproduction as the second wavelength.

  The diffraction grating 53 transmits the light beam emitted from the light source unit 51 and branches it into a main beam and a sub beam. The light beam that has passed through the diffraction grating 53 is converted into parallel light by the collimator lens 55 and enters the first beam splitter 57. The first beam splitter 57 transmits the P-polarized component of the incident light beam and reflects the S-polarized component. The reflected S-polarized light component enters the light receiving element 59 for adjusting the light beam. The expander 61 expands the beam diameter of the P-polarized component transmitted through the beam splitter 57. The collimating lens 63 converts the light beam whose diameter is enlarged again into parallel light. The light beam 94 reflected by the reflection surface of the rising mirror 251 is condensed on the recording surface of the BD via the first objective lens 69.

  The first objective lens 69 can focus the light beam 94 having the first wavelength on the BD as the first optical disk having the first protective substrate thickness 91a. The numerical aperture of the first objective lens 69 is 0.85. The first objective lens 69 includes a diffraction element 291 for correcting spherical aberration caused by a protective substrate thickness error that protects the recording surface of the BD. As the diffractive element 291, for example, a blazed diffractive element having a sawtooth cross section with respect to the transmitting optical axis and having an NA of 0.85 can be used.

  The first objective lens 69 is a so-called two-zone lens, and a second light beam 94 having a first wavelength with respect to a BD as a first disk having a first protective substrate thickness 91a is applied to the second objective lens 69. The light beam 95 having the second wavelength can be focused on the DVD as the second optical disk having the protective substrate thickness 92a. The numerical aperture of the first objective lens 69 is 0.85 for the first wavelength and 0.60 for the second wavelength. The first objective lens 69 includes a diffractive element 691 for correcting spherical aberration caused by a protective substrate thickness error that protects the recording surface of the BD or DVD. As the diffractive element 691, for example, a blazed diffractive element having a sawtooth cross section with respect to the transmitting optical axis and having an NA of 0.85 can be used.

  Next, the second optical system 50b of the optical pickup 2 will be described. The optical pickup 2 is a forward optical system of the second optical system 50b, and a light source unit 52 that emits a light beam for CD recording / reproducing light, and a light beam emitted from the light source unit 52 is branched into a main beam and a sub beam. A diffraction grating 54, a collimating lens 56 for converting a divergent light beam into a parallel light beam, a beam splitter 58 for branching outgoing light and return light, a light receiving element 60 for adjusting outgoing light beam, and outgoing light transmitted through the beam splitter 58 An expander 62 that expands the beam diameter and a collimator lens 64 that converts the light beam transmitted through the expander 62 into parallel light again.

  Further, the optical pickup 2 has a reflection surface that raises the optical axis of the light beam 96 incident along a plane parallel to the recording surface of the optical disc in a substantially vertical direction and guides it to the second objective lens 68. A mirror 252, a λ / 4 plate 66 for converting the linearly polarized light beam 96 whose optical axis has been changed by the rising mirror 252 to circularly polarized light, and the light beam 96 positioned directly above the rising mirror 252 on the CD recording surface And a second objective lens 68 for condensing the light. The raising mirror 252 is combined with the raising mirror 251 to form the beam raising portion 25.

  Further, the optical pickup 2 is a return optical system of the second optical system 50b, and a condensing lens 70 for condensing the return light branched from the emitted light by the beam splitter 58, and a CD recording surface of the light beam 96. A condenser lens 72 that condenses the reflected light reflected on the photodetector, and a photodetector 74 that receives the reflected light and converts it into an electrical signal.

  The light source unit 52 is a light source for recording / reproducing light for CD applied in this specific example, and includes a third laser element (not shown). The third laser element emits a linearly polarized light beam 96 having a wavelength of 785 nm for CD recording / reproduction as a third wavelength.

  The diffraction grating 54 transmits the light beam emitted from the light source unit 52 and branches it into a main beam and a sub beam. The light beam that has passed through the diffraction grating 54 is converted into parallel light by the collimator lens 56 and enters the beam splitter 58. The beam splitter 58 transmits the P-polarized component and reflects the S-polarized component of the incident light beam. The reflected S-polarized light component enters the light receiving element 60 for adjusting the light beam. The expander 62 expands the beam diameter of the P-polarized component transmitted through the beam splitter 58. The collimating lens 64 converts the light beam having an enlarged diameter again into parallel light. The light beam 96 reflected by the reflecting surface of the rising mirror 252 is condensed on the recording surface of the CD via the second objective lens 68.

  The second objective lens 68 can collect the light beam 96 having the third wavelength with respect to the CD as the third optical disk having the third protective substrate thickness 93a. The numerical aperture of the second objective lens 68 is 0.45. The second objective lens 68 includes a diffractive element 681 for correcting spherical aberration caused by a protective substrate thickness error that protects the CD recording surface. As the diffractive element 681, for example, a blazed diffractive element having a sawtooth cross section with respect to the transmitting optical axis and having an NA of 0.45 can be used. In the optical pickup 2, the second objective lens 68 and the diffraction element 681 are fixed to each other and driven by one actuator.

  The relationship between the dimensions of each side of the rising mirror 251 and the rising mirror 252, the assembling method, and the mounting position with respect to the optical disc is the same as that of the optical pickup 1 described above.

  As a result, the optical pickup 1 also allows the reflection surfaces of the rising mirror 251 and the rising mirror 252 to have a pentagonal projection shape when projected onto a plane parallel to the recording surface of the optical disk, and further reflect the reflection. By reducing the distance d between the figure center of the projected figure on the surface 201 and the figure center of the projected figure on the reflecting surface 203 to satisfy dsin θ <(a1 + b2) / 2, the connected portion can be reduced in size. Thus, different types of light beams can be stably guided from different directions.

  FIG. 8 shows an optical disk recording / reproducing apparatus 101 to which the optical pickup shown in FIGS. 1 and 6 is applied as a specific example of the present invention.

  The optical disk recording / reproducing apparatus 101 includes a spindle motor 103 as a driving means for rotating an optical disk 102 as an optical recording medium, an optical pickup 104 according to the present invention, and a feed motor 105 as the driving means. This optical disc recording / reproducing apparatus 101 is a recording / reproducing apparatus that realizes compatibility between three standards capable of recording / reproducing on three types of optical discs 102 having different formats.

  As an optical disk that can be used in this specific example, a BD that uses a light beam having a wavelength of 405 nm as recording / reproducing light, a DVD that uses a light beam having a wavelength of 655 nm as recording / reproducing light, and a light beam having a wavelength of 785 nm are used as recording / reproducing light. CD to play. The optical disc 91, the optical disc 92, and the optical disc 93 described in the upper part correspond to the optical disc 102 shown in FIG.

  Here, the spindle motor 103 and the feed motor 105 are driven and controlled in accordance with the disk type by a servo control unit 109 that is controlled based on a command from the system controller 107 that also serves as a disk type discriminating unit. The optical disk 92 and the optical disk 93 are driven at a predetermined rotational speed.

  The optical pickup 104 is the optical pickup described with reference to FIGS. 1 and 6, and irradiates a recording layer of an optical disc with a different standard with a light beam having a different wavelength, and reflects the reflected light of the light beam on the recording layer. To detect. The optical pickup 104 supplies a signal corresponding to each light beam from the detected reflected light to the preamplifier unit 120.

  The output of the preamplifier unit 120 is sent to a signal modulator / demodulator and error correction code block (hereinafter referred to as a signal modulation / demodulation & ECC block) 108. The signal modulation / demodulation unit and ECC block 108 performs signal modulation, demodulation, and addition of an ECC (error correction code). The optical pickup 104 irradiates a recording layer of the optical disk 102 that rotates in accordance with instructions from the signal modulation / demodulation unit and the ECC block 108, and records or reproduces a signal on the optical disk 102.

  The preamplifier unit 120 is configured to generate a focus error signal, a tracking error signal, an RF signal, and the like based on a signal corresponding to a light beam detected differently for each format. Depending on the type of optical recording medium to be recorded or reproduced, a predetermined control such as demodulation and error correction processing based on the BD, DVD, or CD standard is performed by the servo control circuit 109, the signal modulation / demodulation unit, the ECC block 108, and the like. Is performed.

  Here, for example, if the recording signal demodulated by the signal modulation / demodulation & ECC block 108 is for computer data storage, it is sent to the external computer 130 via the interface 111. Thereby, the external computer 130 or the like can receive a signal recorded on the optical disc 102 as a reproduction signal.

  In addition, if the recording signal demodulated by the signal modulation / demodulation & ECC block 108 is for audio visual, it is digital / analog converted by the D / A conversion unit of the D / A and A / D converter 112 and supplied to the audio visual processing unit 113. Is done. Audio visual processing is performed by the audio visual processing unit 113 and transmitted to an external imaging / projection device (not shown) or the like via the audio visual signal input / output unit 114.

  In the optical pickup 104, for example, control of a feed motor 105 for moving to a predetermined recording track on the optical disk 102, control of a spindle motor 103, and two axes for holding an objective lens serving as a light condensing means in the optical pickup 104 The servo control circuit 109 controls driving of the actuator in the focusing direction and driving in the tracking direction.

  The servo control circuit 109 operates the optical coupling efficiency variable element disposed in the optical pickup 104, and the optical coupling efficiency in the optical pickup 104, that is, the total light amount of light emitted from a laser light source such as a semiconductor laser element and the optical disk. Control is performed so that the ratio of the amount of light collected on 102 is changed according to the recording mode, the reproduction mode, or the type of the optical disk 102.

  The laser control unit 121 controls the laser light source of the optical pickup 104. In particular, in this specific example, the laser control unit 121 performs control to vary the output power of the laser light source between the recording mode and the reproduction mode. Also, control is performed to vary the output power of the laser light source depending on the type of the optical disk 102. The laser control unit 121 switches the laser light source of the optical pickup 104 in accordance with the type of the optical disc 102 detected by the disc type discrimination unit 115.

  The disc type discriminating unit 115 can detect different formats of the optical disc 102 based on the surface reflectivity, the shape and the external shape among BD, DVD, and CD. Each block constituting the optical disc recording / reproducing apparatus 101 is configured to be able to perform signal processing based on the specification of the optical disc to be mounted in accordance with the detection result in the disc type discriminating unit 115.

  The system controller 107 determines the type of the optical disk 102 based on the detection result sent from the disk type determination unit 115. As a method for discriminating the type of the optical recording medium, if the optical recording medium is of a type that is housed in a cartridge, a detection hole is provided in the cartridge and detection is performed using a contact detection sensor or a push switch.

  A servo control circuit 109 functioning as an optical coupling efficiency control unit is controlled by the system controller 107 and controls the optical coupling efficiency in the optical pickup 104 according to the determination result of the disk type determination unit 115. The servo control circuit 109 performs recording and / or reproduction by, for example, detecting the relative position between the optical pickup 104 and the optical disk 102 (including the case of detecting the position based on the address signal recorded on the disk 102). The area can be determined. Then, the servo control circuit 109 controls the optical coupling efficiency in the optical pickup 104 according to the determination result of the recording area to be recorded and / or reproduced.

  According to the optical disc recording / reproducing apparatus 101 described above, the distance between the objective lenses of the optical pickup can be reduced by setting the optical axis rising portion of the optical pickup as shown in FIGS. A condensing part including a mirror and an objective lens can be reduced in size.

  The present invention can be applied to disk formats other than those described in the specific examples as long as the optical pickup performs recording and reproduction with respect to optical recording media having different protective substrate thicknesses using light beams of different wavelengths. For example, optical discs include various types of recording / reproducing discs using optical modulation recording, optical discs including so-called “magneto-optical recording”, “phase change recording”, “dye recording”, etc., specifically “CD-R / RW "," DVD-RAM "," DVD-R / RW "," DVD + RW ", etc., or various magneto-optical recording media. An optical disc is an optical disc in which a recording layer is divided into at least two or more recording regions having different optimum recording and / or reproducing light power on the recording layer, and an optical disc in which a plurality of recording layers are laminated via a transparent substrate. Can also be used.

1 is a plan view seen from a direction perpendicular to a recording surface of an optical disc for explaining an optical system of an optical pickup shown as a specific example of the present invention. FIG. 5 is an enlarged view for explaining a cross section of the periphery of a light collecting portion of an optical pickup shown as a first specific example when viewed from a direction parallel to the recording surface of an optical disc. It is a perspective view explaining the reflective member which has a mirror surface used as a 1st raising mirror and a 2nd raising mirror of the said optical pick-up. It is a perspective view explaining the raising mirror part which combined the 1st raising mirror and the 2nd raising mirror of the said optical pick-up. It is the top view which looked at joining of the 1st raising mirror and 2nd raising mirror of the said optical pick-up from the optical disk side. It is a block diagram explaining the optical system of the optical pick-up shown as a 2nd example of this invention. FIG. 7 is an enlarged view for explaining the vicinity of a recording surface of an optical system of an optical pickup shown as a second specific example. 1 is a configuration diagram illustrating an optical disc recording / reproducing apparatus to which an optical pickup shown as a specific example of the present invention is applied.

Explanation of symbols

  1, 2 optical pickup, 10a first optical system, 10b second optical system, 11, 12 light source unit, 13, 14 diffraction grating, 15, 16 collimating lens, 17, 18 beam splitter, 19.20 light receiving element, 21, 22 expander, 23, 24 collimating lens, 25 beam riser, 251, 252 rise mirror, 26, 27 λ / 4 plate, 28 second objective lens, 29 first objective lens, 30, 31 condensing Lens, 32 second beam splitter, 33, 34, 38 condenser lens, 35, 36, photodetector, 91 first optical disk, 92 second optical disk, 93 third optical disk, 94 light beam 94 (405 nm) ), 95 light beam (655 nm), 96 Light beam (785nm)

Claims (6)

In an optical pickup that performs recording / reproduction with respect to individual disk-shaped optical recording media having different protective substrate thicknesses by light beams having different wavelengths and numerical apertures,
A first light source that emits a first light beam having a first wavelength;
A second light source that emits a second light beam having a second wavelength;
A third light source that emits a third light beam having a third wavelength;
A first objective lens that focuses the first light beam and the second light beam on a recording surface of a disk-shaped optical recording medium;
A second objective lens for condensing the third light beam on the recording surface of the disc-shaped optical recording medium;
A first reflecting surface having a first reflecting surface for raising the optical axes of the first and second light beams incident along a plane parallel to the recording surface of the disc-shaped optical recording medium in a substantially vertical direction. An optical axis changing means;
Second optical axis changing means having a second reflecting surface for raising the optical axis of the third light beam incident along a plane parallel to the recording surface of the disc-shaped optical recording medium in a substantially vertical direction;
Light receiving means for receiving a reflected beam reflected by the disk-shaped optical recording medium and converting it into an electrical signal;
The first reflecting surface is formed by projecting a projected shape projected on a plane parallel to the recording surface of the disc-shaped optical recording medium, with one corner of a rectangle having one side a1 and the other side b1 on one side. It is a pentagon that can be separated by a first line segment connecting one point and one point on the other side, and the second reflecting surface is projected onto a plane parallel to the recording surface of the disc-shaped optical recording medium. The projected shape can be obtained by separating one corner of a rectangle with one side a2 and the other side b2 by a second line segment connecting one point on one side and one point on the other side 5 The first optical axis changing unit and the second optical axis changing unit have a square shape so that a part of the first line segment and a part of the second line segment are in contact with each other on the projection plane. Combined with
The first optical axis changing means reflects the first light beam and the second light beam incident from a direction forming a first angle with respect to a tangential direction of the disc-shaped recording medium, as the first reflection. The optical axis is changed in a substantially vertical direction with respect to the traveling direction of the light beam by the surface and guided to the first objective lens, and the second optical axis changing means includes the first light beam and the first light beam. The third light beam incident from a direction different from the second light beam and forming a second angle with respect to the tangential direction is caused to travel in the traveling direction of the light beam by the second reflecting surface. On the other hand, the optical axis is changed in a substantially vertical direction and guided to the second objective lens,
The first optical axis changing means and the first objective lens located immediately above the first optical axis changing means and the second optical axis changing means and the second objective lens located immediately above the first optical axis changing means are condensed by the first objective lens. An optical pickup, characterized in that the spot and the light condensing spot by the second objective lens are arranged side by side along the recording track direction of the disc-shaped optical recording medium. A pentagonal figure center which is a projection shape obtained by projecting the first reflecting surface onto a plane parallel to the recording surface of the disc-shaped optical recording medium, and the second reflecting surface, wherein the first angle is an angle θ. When the distance between the center of the pentagonal figure, which is a projection shape projected onto a plane parallel to the recording surface of the disk-shaped optical recording medium, is a distance d,
dsin θ <(a1 + b2) / 2
The optical pickup according to claim 1, wherein:   2. The optical pickup according to claim 1, wherein the sum of the first angle and the second angle is 90 degrees. Individual disk-shaped optical recording media having different protective substrate thicknesses are rotationally driven and moved in the radial direction of the disk-shaped optical recording medium by the feeding means, and the wavelength and numerical aperture are changed according to the type of the disk-shaped optical recording medium. In a disk-shaped optical recording medium recording / reproducing apparatus that has an optical pickup that performs recording / reproduction with different light beams, and controls the rotation of the disk-shaped optical recording medium and the movement of the optical pickup according to recording and / or reproducing operations.
The above optical pickup
A first light source that emits a first light beam having a first wavelength;
A second light source that emits a second light beam having a second wavelength;
A third light source that emits a third light beam having a third wavelength;
A first objective lens that focuses the first light beam and the second light beam on a recording surface of a disk-shaped optical recording medium;
A second objective lens for condensing the third light beam on the recording surface of the disc-shaped optical recording medium;
A first reflecting surface having a first reflecting surface for raising the optical axes of the first and second light beams incident along a plane parallel to the recording surface of the disc-shaped optical recording medium in a substantially vertical direction. An optical axis changing means;
Second optical axis changing means having a second reflecting surface for raising the optical axis of the third light beam incident along a plane parallel to the recording surface of the disc-shaped optical recording medium in a substantially vertical direction;
Light receiving means for receiving a reflected beam reflected by the disk-shaped optical recording medium and converting it into an electrical signal;
The first reflecting surface is formed by projecting a projected shape projected on a plane parallel to the recording surface of the disc-shaped optical recording medium, with one corner of a rectangle having one side a1 and the other side b1 on one side. It is a pentagon that can be separated by a first line segment connecting one point and one point on the other side, and the second reflecting surface is projected onto a plane parallel to the recording surface of the disc-shaped optical recording medium. The projected shape can be obtained by separating one corner of a rectangle with one side a2 and the other side b2 by a second line segment connecting one point on one side and one point on the other side 5 The first optical axis changing unit and the second optical axis changing unit have a square shape so that a part of the first line segment and a part of the second line segment are in contact with each other on the projection plane. Combined with
The first optical axis changing means reflects the first light beam and the second light beam incident from a direction forming a first angle with respect to a tangential direction of the disc-shaped recording medium, as the first reflection. The optical axis is changed in a substantially vertical direction with respect to the traveling direction of the light beam by the surface and guided to the first objective lens, and the second optical axis changing means includes the first light beam and the first light beam. The third light beam incident from a direction different from the second light beam and forming a second angle with respect to the tangential direction is caused to travel in the traveling direction of the light beam by the second reflecting surface. On the other hand, the optical axis is changed in a substantially vertical direction and guided to the second objective lens,
The first optical axis changing means and the first objective lens located immediately above the first optical axis changing means and the second optical axis changing means and the second objective lens located immediately above the first optical axis changing means are condensed by the first objective lens. A disc-shaped optical recording medium recording / reproducing apparatus, characterized in that the spot and the focused spot by the second objective lens are juxtaposed along the recording track direction of the disc-shaped optical recording medium. A pentagonal figure center which is a projection shape obtained by projecting the first reflecting surface onto a plane parallel to the recording surface of the disc-shaped optical recording medium, and the second reflecting surface, wherein the first angle is an angle θ. When the distance between the center of the pentagonal figure, which is a projection shape projected onto a plane parallel to the recording surface of the disk-shaped optical recording medium, is a distance d,
dsin θ <(a1 + b2) / 2
5. The disk-shaped optical recording medium recording / reproducing apparatus according to claim 4, wherein:   5. The disk-shaped optical recording medium recording / reproducing apparatus according to claim 4, wherein the sum of the first angle and the second angle is 90 degrees.

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