JP2008251132A - Optical disk drive and information reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To complete an information reproduction from an optical disk in a short period of time. <P>SOLUTION: When information is recorded to the optical disk 100, focal points Fb1 and Fb2 of two blue light beams Lb1 and Lb2 are joined to a first target mark position PS1 and they are made to interfere with each other to form a first recording mark and when information is reproduced from the optical disk 100, reproducing signals of two series can be obtained by joining the focal points Fb1 and Fb2 of the two blue light beams Lb1 and Lb2 to the first and a second target mark positions PS1 and PS2 different from each other to generate blue reproducing light beams Lb3 and Lb4 from the first and the second recording marks located in positions different from each other in a recording layer 101 of the optical disk 100 and one reproducing signal having double reproducing speed can be formed by unifying these reproducing signals. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disk apparatus and an information reproducing method, and is suitable for application to an optical disk apparatus that records a hologram on an optical disk, for example.

  2. Description of the Related Art Conventionally, in an optical disc apparatus, a light beam is irradiated onto an optical disc such as a CD (Compact Disc), a DVD (Digital Versatile Disc), and a Blu-ray Disc (registered trademark, hereinafter referred to as BD), and the reflected light is read. Thus, information that can be reproduced is widely used.

  In such a conventional optical disc apparatus, information is recorded by irradiating the optical disc with a light beam to change the local reflectance of the optical disc.

  For this optical disc, the size of the light spot formed on the optical disc is given by approximately λ / NA (λ: wavelength of the light beam, NA: numerical aperture), and the resolution is also known to be proportional to this value. It has been. For example, Non-Patent Document 1 shows details of a BD that can record data of approximately 25 [GB] on an optical disk having a diameter of 120 [mm].

  By the way, various kinds of information such as various contents such as music contents and video contents, or various data for computers are recorded on the optical disc. In particular, in recent years, the amount of information has increased due to higher definition of video and higher sound quality of music, and an increase in the number of contents to be recorded on one optical disc has been demanded. It is requested.

  In view of this, there has also been proposed a method of increasing the recording capacity of one optical disc by overlapping recording layers in one optical disc (see, for example, Non-Patent Document 2).

  On the other hand, an optical disk apparatus using a hologram has been proposed as a method for recording information on the optical disk (see, for example, Non-Patent Document 3).

  For example, as shown in FIG. 1, the optical disk apparatus 1 condenses a light beam from an optical head 7 once in an optical disk 8 made of a photopolymer whose refractive index changes depending on the intensity of the irradiated light. By using the reflection device 9 provided on the back side (lower side in FIG. 1), the light beam is once again condensed at the same focal position from the opposite direction.

  The optical disc apparatus 1 emits a light beam composed of laser light from a laser 2, modulates the light wave by an acousto-optic modulator 3, and converts it into parallel light by a collimator lens 4. Subsequently, the light beam passes through the polarization beam splitter 5, is converted from linearly polarized light to circularly polarized light by the quarter wavelength plate 6, and then enters the optical head 7.

  The optical head 7 is adapted to record and reproduce information. The optical head reflects a light beam by a mirror 7A, condenses it by an objective lens 7B, and is rotated by a spindle motor (not shown). 8 is irradiated.

  At this time, the light beam is once focused inside the optical disc 8, then reflected by the reflecting device 9 disposed on the back side of the optical disc 8, and from the back side of the optical disc 8 to the same focal point inside the optical disc 8. Focused. Incidentally, the reflection device 9 includes a condenser lens 9A, a shutter 9B, a condenser lens 9C, and a reflection mirror 9D.

  As a result, as shown in FIG. 2 (A), a standing wave is generated at the focal position of the light beam, and the light spot size is formed in a shape in which two cones are bonded together on the bottom surfaces. A recording mark RM composed of a small hologram is formed. Thus, the recording mark RM is recorded as information.

  When a plurality of recording marks RM are recorded in the optical disk 8, the optical disk apparatus 1 rotates the optical disk 8 and arranges the recording marks RM along a concentric or spiral track to form one mark recording layer. And by adjusting the focal position of the light beam, each recording mark RM can be recorded so that a plurality of mark recording layers are stacked.

  As a result, the optical disc 8 has a multilayer structure having a plurality of mark recording layers therein. For example, in the optical disc 8, as shown in FIG. 2B, the distance (mark pitch) p1 between the recording marks RM is 1.5 [μm], the distance between tracks (track pitch) p2 is 2 [μm], and the interlayer The distance p3 is 22.5 [μm].

  Further, when reproducing information from the disc 8 on which the recording mark RM is recorded, the optical disc apparatus 1 closes the shutter 9B of the reflection device 9 so that the light beam is not irradiated from the back side of the optical disc 8.

  At this time, the optical disc apparatus 1 irradiates the recording mark RM in the optical disc 8 with the optical beam by the optical head 7 and causes the reproducing light beam generated from the recording mark RM to enter the optical head 7. The reproduction light beam is converted from circularly polarized light to linearly polarized light by the quarter wavelength plate 6 and reflected by the polarizing beam splitter 5. Further, the reproduction light beam is condensed by the condenser lens 10 and irradiated to the photodetector 12 through the pinhole 11.

At this time, the optical disc apparatus 1 detects the light amount of the reproduction light beam by the photodetector 12 and reproduces information based on the detection result.
Y. Kasami, Y. Kuroda, K. Seo, O. Kawakubo, S. Takagawa, M. Ono, and M. Yamada, Jpn. J. Appl. Phys., 39, 756 (2000) I. Ichimura etal, Technical Digest of ISOM'04, pp52, Oct. 11-15, 2005, Jeju Korea RR McLeod etal., “Microholographic multilayer optical disk data storage,” Appl. Opt., Vol. 44, 2005, pp3197

  Incidentally, in recent years, there is a demand not only for increasing the amount of information recorded on the optical disc 8, but also for reducing the time required for recording and reproduction by improving the recording speed and reproduction speed. In this case, it is conceivable that the optical disc apparatus 1 increases the rotational speed of the optical disc 8 or shortens the time required for reading the recording mark RM.

  However, the optical disc apparatus 1 has a limit on the increase in the rotational speed from the viewpoint of the strength of the optical disc 8 itself, the performance of the spindle motor, blurring, and the like, and to some extent the optical and physical reaction when reading the recording mark RM. Therefore, the upper limit of the reproduction speed is naturally determined.

  For this reason, the optical disk apparatus 1 has a problem that it is difficult to shorten the time required for reproducing information.

  The present invention has been made in view of the above points, and an object of the present invention is to propose an optical disc apparatus and an information reproduction method capable of completing information reproduction from an optical disc in a short time.

  In order to solve this problem, in the optical disc apparatus of the present invention, information is reproduced based on the standing wave recorded by irradiating the first and second lights from both sides of the disc-shaped volume recording medium. In the optical disc apparatus, a first focal position adjusting unit that adjusts a focal position where the first light is connected in the volume type recording medium by the first objective lens in the optical axis direction of the first light; Recording a standing wave on the volume type recording medium, second focus position adjusting means for adjusting the position of the focal point where the second light is connected in the volume type recording medium by the objective lens in the optical axis direction of the second light. The first focus position adjusting means and the second focus so that the first light is focused in the volume type recording medium and the second light is focused at the same position as the focus of the first light. Control the position adjustment means to re-create the information based on the standing wave of the volume recording medium. In this case, the first focus position adjusting means and the second focus position are adjusted so that the focal point where the first light is connected in the volume type recording medium and the focal point where the second light is connected in the volume type recording medium are different from each other. Control means for generating first and second reproduction lights from different standing waves by controlling the focus position adjustment means, and first and second detections for detecting the first and second reproduction lights, respectively. And a reproduction signal generating means for generating a reproduction signal by integrating the detection results of the first and second detection means.

  Thereby, when reproducing information, the first and second reproduction lights can be detected in parallel, so that the speed of reading information from the optical disk can be increased by integrating both detection results.

  In the information reproducing method of the present invention, there is provided an information reproducing method for reproducing information by irradiating predetermined light to a volume type recording medium having a disc shape and recording marks recorded over a plurality of mark layers. The position of the focal point where the first light is connected in the volume type recording medium is adjusted in the optical axis direction of the first light, and the position of the focal point where the second light is connected in the volume type recording medium is adjusted. By adjusting in the optical axis direction, control is performed so that the first light and the second light through the same objective lens are focused on the corresponding positions of different mark layers in the volume type recording medium. A focus control step for generating first and second reproduction lights based on recording marks of different mark layers, a detection step for detecting the first and second reproduction lights, respectively, and a detection result by the detection step. It was provided and a reproduction signal generation step of generating a reproduced signal by integrating.

  Thereby, when reproducing information, the first and second reproduction lights can be detected in parallel, so that the speed of reading information from the optical disk can be increased by integrating both detection results.

  According to the present invention, when reproducing information, the first and second reproduction lights can be detected in parallel, so that the speed of reading information from the optical disk can be increased by integrating both detection results. Thus, it is possible to realize an optical disc apparatus and an information reproduction method capable of completing information reproduction from an optical disc in a short time.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

(1) First Embodiment (1-1) Configuration of Optical Disc First, an optical disc 100 as a volume type recording medium in the first embodiment will be described. As shown in the external view of FIG. 3, the optical disc 100 as a whole is configured in a disk shape having a diameter of about 120 [mm], like a conventional CD, DVD, and BD, and a hole 100H is formed in the central portion. ing.

  Further, the optical disc 100 has a recording layer 101 for recording information as a center as shown in a cross-sectional view in FIG. 4A, and the recording layer 101 is sandwiched from both sides by the substrates 102 and 103. It is configured.

  Incidentally, the thickness t1 of the recording layer 101 is about 0.3 [mm], and the thicknesses t2 and t3 of the substrates 102 and 103 are both about 0.6 [mm].

  The substrates 102 and 103 are made of, for example, a material such as polycarbonate or glass, and both of them transmit light incident from one surface to the opposite surface with high transmittance. Further, the substrates 102 and 103 have a certain degree of strength and play a role of protecting the recording layer 101.

  Incidentally, the optical disc 100 has a substantially symmetric structure with the recording layer 101 as the center in the thickness direction, and consideration is given to suppressing the occurrence of warpage, distortion, etc. due to secular change as a whole. In addition, about the surface of the board | substrates 102 and 103, unnecessary reflection may be made to be prevented by anti-reflective coating.

  Similar to the optical disc 8 (FIG. 1), the recording layer 101 is made of a photopolymer whose refractive index changes depending on the intensity of irradiated light, and responds to a blue light beam having a wavelength of 405 [nm]. As shown in FIG. 4A, when two blue light beams Lb1 and Lb2 having relatively strong intensities interfere in the recording layer 101, a standing wave is generated in the recording layer 101. Thus, an interference pattern having properties as a hologram as shown in FIG. 2A is formed.

  Further, the recording layer 101 has a refractive index equivalent to that of the substrates 102 and 103 with respect to a blue light beam having a wavelength of 405 [nm], and the blue light is reflected at the boundary surface between the recording layer 101 and the substrate 103. The beam is hardly refracted.

  The optical disc 100 also has a reflection / transmission film 104 as a positioning layer on the boundary surface between the recording layer 101 and the substrate 102. The reflection / transmission film 104 is made of a dielectric multilayer film or the like, and transmits the blue light beams Lb1 and Lb2 and the blue reproduction light beam Lb3 having a wavelength of 405 [nm], and about the red light beam having a wavelength of 660 [nm]. It has a wavelength selectivity of transmitting at a rate of 50% and reflecting at a rate of about 50%.

  The reflection / transmission film 104 forms a tracking servo guide groove. Specifically, a spiral track is formed by lands and grooves similar to a general BD-R (Recordable) disk. Yes. This track is given an address consisting of a series of numbers for each predetermined recording unit, and the track on which information is recorded or reproduced can be specified by the address.

  Note that pits or the like may be formed in the reflective / transmissive film 104 (that is, the boundary surface between the recording layer 101 and the substrate 102) instead of the guide grooves, or the guide grooves and pits may be combined.

  When the red light beam Lr1 is irradiated from the substrate 102 side, the reflection / transmission film 104 transmits about half of the reflection / transmission film 104 to the substrate 103 side and reflects about half of the reflection / transmission film 104 toward the substrate 102 side. Hereinafter, the light beam transmitted at this time is referred to as a red transmitted light beam Lr2, and the reflected light beam is referred to as a red reflected light beam Lr3.

  For example, in the optical disc apparatus, the red reflected light beam Lr3 matches the focus Fr of the red light beam Lr1 collected by a predetermined objective lens OL1 with respect to a target track (hereinafter referred to as a target track). Therefore, it is assumed to be used for position control (that is, focus control and tracking control) of the objective lens OL1.

  In the following, the surface on the substrate 102 side of the optical disc 100 is referred to as a first surface 100A, and the surface on the substrate 103 side of the optical disc 100 is referred to as a second surface 100B.

  In practice, when information is recorded on the optical disk 100, as shown in FIG. 4A, the red light beam Lr1 is condensed by the position-controlled objective lens OL1, and is aligned with the target track of the reflective / transmissive film 104. To be burned.

  Further, the blue light beam Lb1 that shares the optical axis Lx with the red light beam Lr1 and is condensed by the objective lens OL1 passes through the substrate 102 and the reflective / transmissive film 104, and is behind the target track in the recording layer 101. In other words, it is focused on a position corresponding to (that is, the substrate 103 side). At this time, the focal point Fb1 of the blue light beam Lb1 is located farther than the focal point Fr on the common optical axis Lx with reference to the objective lens OL1.

  Further, the blue light beam Lb2 having the same wavelength as that of the blue light beam Lb1 and sharing the optical axis Lx has an optical characteristic equivalent to that of the objective lens OL1 from the opposite side of the blue light beam Lb1 (that is, the substrate 103 side). The light is condensed and irradiated by the lens OL2. At this time, the focal point Fb2 of the blue light beam Lb2 is set to the same position as the focal point Fb1 of the blue light beam Lb1 by controlling the position of the objective lens OL2.

  As a result, on the optical disc 100, a standing wave is generated by the blue light beams Lb1 and Lb2 at the positions of the focal points Fb1 and Fb2 corresponding to the back side of the target track in the recording layer 101, and the recording has a relatively small interference pattern. A mark RM is recorded.

  At this time, in the recording layer 101, the blue light beams Lb1 and Lb2 which are both converged light are overlapped, and a standing wave is generated in a portion where the intensity is not less than a predetermined intensity, so that a recording mark RM is formed. For this reason, as shown in FIG. 2 (A), the recording mark RM generally has a shape in which two cones are bonded to each other at the bottom surfaces, and a central portion (a portion where the bottom surfaces are bonded together). Is slightly constricted.

  Incidentally, with respect to the recording mark RM, the diameter RMr of the constricted portion at the center is expressed as follows when the wavelengths of the blue light beams Lb1 and Lb2 are λ [m] and the numerical apertures of the objective lenses OL1 and OL2 are NA (1) ).

  Further, the height RMh of the recording mark RM can be obtained by the following equation (2), where n is the refractive index of the objective lenses OL1 and OL2.

  For example, when the wavelength λ is 405 [nm], the numerical aperture NA is 0.5, and the refractive index n is 1.5, the diameter RMr = 0.97 [μm] from the formula (1) and the height from the formula (2). RMh = 9.72 [μm].

  Further, the optical disc 100 is designed such that the thickness t1 (= 0.3 [mm]) of the recording layer 101 is sufficiently larger than the height RMh of the recording mark RM. For this reason, the optical disc 100 records the recording mark RM while switching the distance from the recording reflective film 104 in the recording layer 101 (hereinafter referred to as depth), as shown in FIG. In addition, it is possible to perform multilayer recording in which a plurality of mark recording layers are stacked in the thickness direction of the optical disc 100.

  In this case, the depth of the recording mark RM is changed by adjusting the depths of the focal points Fb1 and Fb2 of the blue light beams Lb1 and Lb2 in the recording layer 101 of the optical disc 100. For example, in the optical disc 100, when the distance p3 between the mark recording layers is set to about 15 [μm] in consideration of the mutual interference between the recording marks RM, about 20 mark recording layers are formed in the recording layer 101. can do. The distance p3 may be set to various values other than about 15 [μm] in consideration of the mutual interference between the recording marks RM.

  On the other hand, in the optical disc 100, when information is reproduced, as shown in FIG. 4B, the red light beam Lr1 collected by the objective lens OL1 is reflected and transmissive film 104 as in the case of recording the information. The objective lens OL1 is position-controlled so as to be focused on the target track.

  In the optical disc 100, the focal point Fb1 of the blue light beam Lb1 transmitted through the substrate 102 and the reflective / transmissive film 104 via the same objective lens OL1 corresponds to the “back side” of the target track in the recording layer 101, and the first Is focused on a position having a target depth (hereinafter referred to as a first target mark position PS1).

  At this time, the recording mark RM (hereinafter referred to as the first recording mark RM1) recorded at the first target mark position PS1 generates a blue reproduction light beam Lb3 due to the property as a hologram. The blue reproduction light beam Lb3 has optical characteristics equivalent to those of the blue light beam Lb2 irradiated during recording of the first recording mark RM1, and is in the same direction as the blue light beam Lb2, that is, from within the recording layer 101. The process proceeds while diverging toward the substrate 102 side.

  In addition to such a configuration, the optical disc 100 is configured such that the position of the objective lens OL2 is controlled based on the red transmitted light beam Lr2 formed by transmitting the red light beam Lr1 through the reflective / transmissive film 104.

  Further, in the optical disc 100, the focal point Fb2 of the blue light beam Lb2 transmitted through the substrate 103 via the objective lens OL2 corresponds to the “back side” of the target track in the recording layer 101, and is different from the first target depth. Is focused on a position having a target depth (hereinafter referred to as a second target mark position PS2).

  At this time, the recording mark RM (hereinafter referred to as the second recording mark RM2) recorded at the second target mark position PS2 is, like the first recording mark RM, due to the properties as a hologram, the blue reproduction light beam Lb4. Is generated. The blue reproduction light beam Lb4 has the same optical characteristics as the blue light beam Lb1 irradiated when the second recording mark RM2 is recorded, and is in the same direction as the blue light beam Lb1, that is, from within the recording layer 101. The process proceeds while diverging toward the substrate 103 side.

  As described above, when information is recorded on the optical disc 100, the focal points Fb1 and Fb2 overlap in the recording layer 101 by using the red light beam Lr1 for position control and the blue light beams Lb1 and Lb2 for information recording. The recording mark RM is formed as the information at the position, that is, the target mark position on the back side of the target track and the target depth in the reflective / transmissive film 104.

  Further, when recorded information is reproduced, the optical disc 100 uses the red light beam Lr1 and the red transmitted light beam Lr2 for position control, and the blue light beams Lb1 and Lb2 for information reproduction, so that the focal points Fb1 and Fb2 are used. The blue reproduction light beams Lb3 and Lb4 are respectively generated from the first recording mark RM1 and the second recording mark RM2 recorded at the first target mark position PS1 and the second target mark position PS2, respectively. ing.

(1-2) Configuration of Optical Disc Device Next, the optical disc device 20 corresponding to the optical disc 100 described above will be described. As shown in FIG. 5, the optical disc apparatus 20 is configured to control the whole by a control unit 21.

  The control unit 21 is mainly configured by a CPU (Central Processing Unit) (not shown), reads various programs such as a basic program and an information recording program from a ROM (Read Only Memory) (not shown), and stores them in a RAM (Random) (not shown). Various processes such as an information recording process are executed by expanding in (Access Memory).

  For example, when the control unit 21 receives an information recording command, recording information, and recording address information from an external device (not shown) with the optical disc 100 loaded, the control unit 21 supplies the driving command and recording address information to the driving control unit 22. The recording information is supplied to the signal processing unit 23. Incidentally, the recording address information is information indicating an address at which the recording information is to be recorded among the addresses attached to the recording layer 101 or the reflection / transmission film 104 of the optical disc 100.

  The drive control unit 22 drives and controls the spindle motor 24 in accordance with the drive command to rotate the optical disc 100 at a predetermined rotation speed, and controls the sled motor 25 to drive the optical pickup 26 with the moving shafts 25A and 25B. Are moved to a position corresponding to the recording address information in the radial direction of the optical disc 100 (that is, the inner circumferential direction or the outer circumferential direction).

  The signal processing unit 23 generates a recording signal by performing various signal processing such as predetermined encoding processing and modulation processing on the supplied recording information, and supplies the recording signal to the optical pickup 26.

  As shown in FIG. 6, the optical pickup 26 has a substantially U-shaped side surface. As shown in FIGS. 4 (A) and 4 (B), the optical pickup 26 is focused on the optical disk 100 from both sides. The beam can be irradiated.

  The optical pickup 26 performs focus control and tracking control based on the control of the drive control unit 22 (FIG. 5), so that a track (hereinafter, referred to as recording address information in the recording layer 101 or the reflective transmission film 104 of the optical disc 100). This is called a target track), and a recording mark RM corresponding to the recording signal from the signal processing unit 23 is recorded (the details will be described later).

  When the control unit 21 receives, for example, an information reproduction command and reproduction address information indicating the address of the recording information from an external device (not shown), the control unit 21 supplies the drive command to the drive control unit 22 and also reproduces the reproduction processing command. Is supplied to the signal processing unit 23.

  As in the case of recording information, the drive control unit 22 controls the spindle motor 24 to rotate the optical disc 100 at a predetermined rotational speed, and controls the sled motor 25 to control the optical pickup 26 for reproduction addressing. Move to a position corresponding to the information.

  The optical pickup 26 performs focus control and tracking control based on the control of the drive control unit 22 (FIG. 4), so that the track (that is, the target) indicated by the reproduction address information in the recording layer 101 or the reflection / transmission film 104 of the optical disc 100 is obtained. The irradiation position of the light beam is aligned with the track), and the light beam with a predetermined light amount is irradiated. At this time, the optical pickup 26 detects the reproduction light beam generated from the recording mark RM of the recording layer 101 in the optical disc 100 and supplies a detection signal corresponding to the amount of light to the signal processing unit 23 (details). Will be described later).

  The signal processing unit 23 generates reproduction information by performing various signal processing such as predetermined demodulation processing and decoding processing on the supplied detection signal, and supplies the reproduction information to the control unit 21. In response to this, the control unit 21 sends the reproduction information to an external device (not shown).

  As described above, the optical disc apparatus 20 controls the optical pickup 26 by the control unit 21 to record information on the target track in the recording layer 101 of the optical disc 100 and reproduce information from the target track. .

(1-3) Configuration of Optical Pickup Next, the configuration of the optical pickup 26 will be described. As schematically shown in FIG. 7, the optical pickup 26 is provided with a large number of optical components, and is roughly divided into a first surface position control optical system 30, a second surface position control optical system 50, and a first surface. An information optical system 60 and a second surface information optical system 80 are included.

(1-3-1) Configuration of Position Control Optical System The first surface position control optical system 30 and the second surface position control optical system 50 are mainly an objective lens based on the red light beam Lr1 and the red transmitted light beam Lr2. The positions 38 and 51 are controlled.

(1-3-1-1) Configuration of First Surface Position Control Optical System The first surface position control optical system 30 irradiates the first surface 100A of the optical disc 100 with the red light beam Lr1, and causes the optical disc 100 to A red reflected light beam Lr3 formed by reflecting the red light beam Lr1 is received.

  In FIG. 8 corresponding to FIG. 7, the laser diode 31 of the first surface position control optical system 30 can emit red laser light having a wavelength of about 660 [nm]. Actually, the laser diode 31 emits a predetermined amount of red light beam Lr1 made of divergent light based on the control of the control unit 21 (FIG. 5) and makes it incident on the collimator lens 32. The collimator lens 32 converts the red light beam Lr1 from diverging light to parallel light and makes it incident on the non-polarizing beam splitter 34 via the slit 33.

  The non-polarizing beam splitter 34 transmits the red light beam Lr1 at a rate of about 50% on the reflection / transmission surface 34A and makes it incident on the correction lens 35. The correction lenses 35 and 36 cause the red light beam Lr1 to diverge once and then converge to enter the dichroic prism 37.

  The reflection / transmission surface 37S of the dichroic prism 37 has so-called wavelength selectivity in which the transmittance and the reflectance differ depending on the wavelength of the light beam, and transmits the red light beam at a rate of approximately 100%. Is reflected at a rate of almost 100%. Therefore, the dichroic prism 37 transmits the red light beam Lr1 through the reflection / transmission surface 37S and makes it incident on the objective lens 38.

  The objective lens 38 condenses the red light beam Lr1 and irradiates it toward the first surface 100A of the optical disc 100. At this time, as shown in FIG. 4A, the red light beam Lr1 is transmitted through the substrate 102 and reflected by the reflection / transmission film 104, and becomes a red reflected light beam Lr3 directed in the opposite direction to the red light beam Lr1.

  The objective lens 38 is designed to be optimized for the blue light beam Lb1, and the red light beam Lr1 has a numerical aperture (NA) depending on the optical distance between the slit 33 and the correction lenses 35 and 36. : Numerical Aperture) acts as a condenser lens with 0.41.

  Thereafter, the red reflected light beam Lr3 is sequentially transmitted through the objective lens 38, the dichroic prism 37, and the correction lenses 36 and 35 to become parallel light, and then enters the non-polarized beam splitter 34.

  The non-polarizing beam splitter 34 irradiates the mirror 40 by reflecting the red reflected light beam Lr3 at a ratio of about 50%, and reflects the red reflected light beam Lr3 again by the mirror 40, and then collects the condensing lens 41. To enter.

  The condensing lens 41 converges the red reflected light beam Lr3, gives astigmatism by the cylindrical lens 42, and irradiates the photodetector 43 with the red reflected light beam Lr3.

  By the way, in the optical disc apparatus 20, since there is a possibility that the rotating optical disc 100 may be decentered or face-blurred, the relative position of the target track with respect to the first surface position control optical system 30 may vary.

  Therefore, in order to make the focus Fr (FIG. 4A) of the red light beam Lr1 follow the target track in the first surface position control optical system 30, the focus Fr is a focus direction that is in the proximity direction or the separation direction with respect to the optical disc 100. It is necessary to move in the tracking direction which is the direction of the optical disk 100 and the direction of the inner circumference or the outer circumference of the optical disc 100.

  Therefore, the objective lens 38 can be driven in the biaxial direction of the focus direction and the tracking direction by the biaxial actuator 38A.

  In the first surface position control optical system 30 (FIG. 8), the focusing state when the red light beam Lr1 is collected by the objective lens 38 and applied to the reflective / transmissive film 104 of the optical disc 100 is red by the condenser lens 41. The optical positions of the various optical components are adjusted so that the reflected light beam Lr3 is reflected and reflected in the focused state when the photodetector 43 is irradiated.

  As shown in FIG. 9A, the photodetector 43 has four detection areas 43A, 43B, 43C, and 43D that are divided in a lattice pattern on the surface irradiated with the red reflected light beam Lr3. Incidentally, the direction (vertical direction in the figure) indicated by the arrow a1 corresponds to the traveling direction of the track when the red light beam Lr1 is irradiated onto the reflective / transmissive film 104 (FIG. 3).

  The photodetector 43 detects a part of the red reflected light beam Lr3 by the detection areas 43A, 43B, 43C, and 43D, respectively, and generates detection signals SDA1, SDB1, SDC1, and SDD1 according to the amount of light detected at this time, respectively. These are sent to the signal processing unit 23 (FIG. 4).

  The signal processing unit 23 performs focus control by a so-called astigmatism method, calculates a focus error signal SFE1 according to the following equation (3), and supplies this to the drive control unit 22.

  The focus error signal SFE1 represents the amount of deviation between the focal point Fr of the red light beam Lr1 and the reflective / transmissive film 104 of the optical disc 100.

  The signal processing unit 23 performs tracking control by a so-called push-pull method. The signal processing unit 23 calculates a tracking error signal STE1 according to the following equation (4) and supplies the tracking error signal STE1 to the drive control unit 22.

  The tracking error signal STE1 represents the amount of deviation between the focal point Fr of the red light beam Lr1 and the target track in the reflective / transmissive film 104 of the optical disc 100.

  The drive control unit 22 generates a focus drive signal SFD1 based on the focus error signal SFE1, and supplies the focus drive signal SFD1 to the biaxial actuator 38A, whereby the red light beam Lr1 is applied to the reflective / transmissive film 104 of the optical disc 100. The objective lens 38 is feedback-controlled (that is, focus control) so as to be focused.

  Further, the drive control unit 22 generates a tracking drive signal STDr based on the tracking error signal STE1 and supplies the tracking drive signal STD1 to the biaxial actuator 38A, whereby the red light beam Lr1 is reflected and transmitted by the reflective / transmissive film 104 of the optical disc 100. The objective lens 38 is feedback-controlled (that is, tracking control) so as to focus on the target track.

  In this way, the first surface position control optical system 30 irradiates the reflection / transmission film 104 of the optical disc 100 with the red light beam Lr1, and supplies the light reception result of the red reflection light beam Lr3, which is the reflected light, to the signal processing unit 23. It is made like that. In response to this, the drive control unit 22 performs focus control and tracking control of the objective lens 38 so as to focus the red light beam Lr1 on the target track of the reflection / transmission film 104 (hereinafter collectively referred to as position control). ).

(1-3-1-2) Configuration of Second Surface Position Control Optical System On the other hand, in the second surface position control optical system 50, the red light beam Lr1 is applied to the reflection / transmission film 104 (FIG. 4A) of the optical disc 100. The position of the objective lens 51 is controlled based on the transmitted red transmitted light beam Lr2.

  Incidentally, the objective lens 51 is configured integrally with the biaxial actuator 51A, and by the biaxial actuator 51A, as in the objective lens 38, the focus direction which is the approaching direction or the separation direction to the optical disc 100, It can be driven in a biaxial direction with a tracking direction which is a circumferential direction or a circumferential direction.

  The red transmitted light beam Lr2 passes through the recording layer 101 and the substrate 103 of the optical disc 100 and then becomes divergent light and enters the objective lens 51. The red transmitted light beam Lr <b> 2 is converted into substantially parallel light by the objective lens 51, reflected by the galvanometer mirror 52, and then incident on the relay lens 53.

  Subsequently, the red transmitted beam Lr <b> 2 is converted into convergent light to some extent by the fixed lens 55 of the relay lens 53 and is incident on the dichroic prism 56.

  The reflection / transmission surface 56S of the dichroic prism 56 has wavelength selectivity like the reflection / transmission surface 37S of the dichroic prism 37, reflects the red light beam at a rate of almost 100%, and substantially reflects the blue light beam. It is designed to transmit at a rate of 100%. For this reason, the dichroic prism 56 reflects the red transmitted light beam Lr 2 on the reflection / transmission surface 56 </ b> S and makes it incident on the condenser lens 57.

  The condensing lens 57 converges the red transmitted light beam Lr2 and irradiates the photodetector 59 with astigmatism by the cylindrical lens 58.

  By the way, there is a possibility that the optical disc 100 may cause surface blurring as described above. For this reason, as described above, the position of the objective lens 38 is controlled by the first surface position control optical system 30, the drive control unit 22 (FIG. 4), and the like.

  At this time, the optical axis Lx of the red transmitted light beam Lr2 changes as the objective lens 38 moves. Here, if the objective lens 51 is fixed at a reference position, the focus of the red light beam is deviated from the focus Fr1 of the red light beam Lr1, and the blue light beam shown in FIG. The focal point Fb2 of Lb2 cannot be made coincident with the focal point Fb1 of the blue light beam Lb1.

  Therefore, in the second surface position control optical system 50, the amount of deviation between the focal point of the objective lens 51 relating to the red light beam and the focal point Fr1 of the red light beam Lr1 in the reflection / transmission film 104 is determined by the condenser lens 57 as the red transmitted light beam Lr2. The optical positions of the various optical components are adjusted so that the light is reflected and reflected in the irradiation state when the light is irradiated onto the photodetector 59.

  As shown in FIG. 9B, the photodetector 59 has four detection areas 59A, 59B, 59C, and 59D divided in a lattice pattern on the surface irradiated with the red transmitted light beam Lr2, as with the photodetector 43. Have. Incidentally, the direction (vertical direction in the figure) indicated by the arrow a2 corresponds to the track traveling direction in the reflective / transmissive film 104 (FIG. 4A) when the red transmitted light beam Lr2 is irradiated.

  The photodetector 59 detects a part of the red transmitted light beam Lr2 by the detection areas 59A, 59B, 59C, and 59D, respectively, and generates detection signals SDA2, SDB2, SDC2, and SDD2 according to the detected light amount, respectively. These are sent to the signal processing unit 23 (FIG. 4).

  The signal processing unit 23 performs focus control by a so-called astigmatism method, calculates a focus error signal SFE2 according to the following equation (5), and supplies this to the drive control unit 22.

  The focus error signal SFE2 represents the amount of shift in the focus direction between the focal point of the objective lens 51 relating to the red light beam and the focal point Fr of the red light beam Lr1 in the reflection / transmission film 104.

  The signal processing unit 23 performs tracking control using a push-pull signal. The signal processing unit 23 calculates a tracking error signal STE2 according to the following equation (6) and supplies the tracking error signal STE2 to the drive control unit 22.

  This tracking error signal STE2 represents the amount of deviation in the tracking direction between the focal point of the objective lens 51 relating to the red light beam and the focal point Fr of the red light beam Lr1 in the reflection / transmission film 104.

  Further, the signal processing unit 23 generates a tangential error signal necessary for tangential control. This tangential control is to eliminate the deviation between the focal point of the objective lens 51 relating to the red light beam and the focal point Fr of the red light beam Lr1 in the reflection / transmission film 104 in the tangential direction (that is, the tangential direction of the track). Control.

  Specifically, the signal processing unit 23 performs tangential control using a push-pull signal. The signal processing unit 23 calculates a tangential error signal SNE2 according to the following equation (7), and sends this to the drive control unit 22. Supply.

  This tangential error signal SNE2 represents the amount of deviation in the tangential direction between the focal point of the objective lens 51 relating to the red light beam and the focal point Fr of the red light beam Lr1 in the reflection / transmission film 104.

  In response to this, the drive control unit 22 generates a focus drive signal SFD2 based on the focus error signal SFE2, and supplies the focus drive signal SFD2 to the biaxial actuator 51A, whereby the focus of the objective lens 51 relating to the red light beam. The focus of the objective lens 51 is controlled so as to reduce the amount of deviation of the red light beam Lr1 from the focal point Fr in the reflection / transmission film 104.

  The drive control unit 22 generates a tracking drive signal STD2 based on the tracking error signal STE2, and supplies the tracking drive signal STD2 to the biaxial actuator 51A. The objective lens 51 is tracking-controlled so as to reduce the amount of deviation of the red light beam Lr1 from the focal point Fr in the transmission film 104.

  Further, the drive control unit 22 generates a tangential drive signal SND2 based on the tangential error signal SNE2, and supplies the tangential drive signal SND2 to the galvanometer mirror 52, whereby the focus on the red light beam of the objective lens 51 is increased. The tangential control is performed to adjust the angle of the reflecting surface 52A of the galvano mirror 52 so as to reduce the amount of deviation of the red light beam Lr1 from the focal point Fr in the reflective / transmissive film 104.

  In this way, the second surface position control optical system 50 receives the red transmitted light beam Lr2 incident on the objective lens 51 from the second surface 100B of the optical disc 100 and supplies the light reception result to the signal processing unit 23. Has been made. In response to this, the drive control unit 22 performs focus control and tracking control of the objective lens 51 and galvanometer so that the focal point of the objective lens 51 concerning the red light beam coincides with the focal point Fr of the red light beam Lr1 in the reflection / transmission film 104. Tangential control by the mirror 52 (hereinafter collectively referred to as position control) is performed.

(1-3-2) Configuration of Information Optical System On the other hand, the first surface information optical system 60 and the second surface information optical system 80 mainly irradiate the optical disc 100 with blue light beams Lb1 and Lb2, and also reproduce blue reproduced light. The beams Lb3 and Lb4 are detected.

(1-3-2-1) Irradiation of Blue Light Beam on First Surface In FIG. 10 corresponding to FIG. 7, the laser diode 61 of the first surface information optical system 60 is a blue laser beam having a wavelength of about 405 [nm]. It is made to be able to inject. In practice, the laser diode 61 emits a blue light beam Lb0 made of divergent light based on the control of the control unit 21 (FIG. 5) and makes it incident on the collimator lens 62. The collimator lens 62 converts the blue light beam Lb0 from diverging light into parallel light and makes it incident on the half-wave plate 63.

  At this time, the blue light beam Lb0 is adjusted so that, for example, the ratio of the p-polarized component and the s-polarized component is approximately 50% by rotating the polarization direction at the half-wave plate 64 by a predetermined angle. After the intensity distribution is shaped by the prism 64, the light is incident on the surface 65 A of the polarization beam splitter 65.

  The polarization beam splitter 65 is configured to reflect or transmit the light beam on the reflection / transmission surface 65S at a different rate depending on the polarization direction of the light beam. For example, the reflection / transmission surface 65S reflects an s-polarized light beam and transmits a p-polarized light beam.

  In practice, the polarization beam splitter 65 reflects the s-polarized component, which is about 50% of the blue light beam Lb0, by the reflection / transmission surface 65S to form the blue light beam Lb1, and enters the quarter-wave plate 66 from the surface 65B. At the same time, the remaining 50% of the p-polarized light component is transmitted as a blue light beam Lb2, and is incident on the shutter 81 from the surface 65D.

  The quarter-wave plate 66 converts the blue light beam Lb1 from linearly polarized light to circularly polarized light and irradiates the movable mirror 67, and is reflected by the movable mirror 67 and converts the blue light beam Lb1 from circularly polarized light to linearly polarized light. Then, the light is again incident on the surface 65B of the polarization beam splitter 65.

  At this time, the blue light beam Lb1 is converted from s-polarized light to left-circularly polarized light by, for example, the quarter-wave plate 66, converted from left-circularly polarized light to right-circularly polarized light when reflected by the movable mirror 67, and then again 1 / 4 wavelength plate 66 converts right circularly polarized light into p polarized light. That is, the polarization direction of the blue light beam Lb1 is different when it is emitted from the surface 65B and when it is incident on the surface 65B after being reflected by the movable mirror 67.

  The polarization beam splitter 65 transmits the blue light beam Lb1 as it is through the reflection / transmission surface 65S according to the polarization direction (p-polarization) of the blue light beam Lb1 incident from the surface 65B, and passes from the surface 65C to the polarization beam splitter 68. It is made to enter.

  As a result, the first surface information optical system 60 extends the optical path length of the blue light beam Lb1 by the polarizing beam splitter 65, the quarter wavelength plate 66, and the movable mirror 67.

  The reflection / transmission surface 68S of the polarization beam splitter 68 reflects, for example, an s-polarized light beam and transmits a p-polarized light beam. In practice, the polarization beam splitter 68 transmits the blue light beam Lb1 as it is through the reflection / transmission surface 68S, and converts it from linearly polarized light (p-polarized light) to circularly polarized light (right circularly polarized light) by the quarter wavelength plate 69. Then, the light is incident on the relay lens 70.

  The relay lens 70 converts the blue light beam Lb1 from parallel light into convergent light by the movable lens 71, converts the blue light beam Lb1 that has become divergent light after convergence into the convergent light again by the fixed lens 72, and the dichroic prism. 37 is incident.

  Here, the movable lens 71 is moved in the optical axis direction of the blue light beam Lb1 by the actuator 71A. In practice, the relay lens 70 can change the convergence state of the blue light beam Lb1 emitted from the fixed lens 72 by moving the movable lens 71 by the actuator 71A based on the control of the control unit 21 (FIG. 5). Has been made.

  The dichroic prism 37 reflects the blue light beam Lb1 by the reflection / transmission surface 37S in accordance with the wavelength of the blue light beam Lb1, and makes it incident on the objective lens 38. Incidentally, when the blue light beam Lb1 is reflected on the reflection / transmission surface 37S, the polarization direction of the circularly polarized light is inverted, and is converted from, for example, right circularly polarized light to left circularly polarized light.

  The objective lens 38 condenses the blue light beam Lb1 and irradiates the first surface 100A of the optical disc 100 with it. Incidentally, the objective lens 38 acts as a condensing lens having a numerical aperture (NA) of 0.5 with respect to the blue light beam Lb1 due to the optical distance to the relay lens 70 and the like.

  At this time, as shown in FIG. 4A, the blue light beam Lb1 is transmitted through the substrate 102 and the reflective / transmissive film 104 and is focused in the recording layer 101. Here, the position of the focal point Fb1 of the blue light beam Lb1 is determined by the convergence state when the blue light beam Lb1 is emitted from the fixed lens 72 of the relay lens 70. That is, the focal point Fb1 moves to the first surface 100A side or the second surface 100B side in the recording layer 101 according to the position of the movable lens 71.

  Specifically, the first surface information optical system 60 is designed so that the moving distance of the movable lens 71 and the moving distance of the focal point Fb1 of the blue light beam Lb1 are substantially proportional to each other. mm], the focal point Fb1 of the blue light beam Lb1 is moved by 30 [μm].

  In practice, the first surface information optical system 60 has the focal point Fb1 (FIG. 3) of the blue light beam Lb1 in the recording layer 101 of the optical disc 100 when the position of the movable lens 71 is controlled by the control unit 21 (FIG. 5). The depth d1 of (B)) (that is, the distance from the reflective / transmissive film 104) is adjusted.

  The blue light beam Lb1 becomes divergent light after converging to the focal point Fb1, passes through the recording layer 101 and the substrate 103, is emitted from the second surface 100B, and enters the objective lens 51 (details will be described later).

  As described above, the first surface information optical system 60 irradiates the blue light beam Lb1 from the first surface 100A side of the optical disc 100 to position the focal point Fb1 of the blue light beam Lb1 in the recording layer 101, and further, the relay lens 70. The depth d1 of the focal point Fb1 is adjusted according to the position of the movable lens 71 in FIG. Hereinafter, an optical path that the blue light beam Lb1 follows in the first surface information optical system 60 is referred to as a blue light path 1.

(1-3-2-2) Irradiation of the blue light beam on the second surface In FIG. 7, the polarization beam splitter 65 of the first surface information optical system 60 is p-polarized light on the reflection / transmission surface 65S as described above. The blue light beam Lb0 is transmitted at a rate of about 50%, and is incident on the shutter 81 from the surface 65D as the blue light beam Lb2.

  In FIG. 11 corresponding to FIG. 7, the shutter 81 of the second surface information optical system 80 is configured to block or transmit the blue light beam Lb <b> 2 based on the control of the control unit 21 (FIG. 5). When the light beam Lb2 is transmitted, it is incident on the polarization beam splitter 82.

  Incidentally, as the shutter 81, for example, a mechanical shutter that blocks or transmits the blue light beam Lb2 by mechanically moving a blocking plate that blocks the blue light beam Lb2, or the blue color by changing the voltage applied to the liquid crystal panel. A liquid crystal shutter or the like that blocks or transmits the light beam Lb2 can be used.

  The reflection / transmission surface 82S of the polarization beam splitter 82 transmits, for example, a p-polarized light beam at a rate of about 100% and reflects an s-polarized light beam at a rate of about 100%. In practice, the polarization beam splitter 82 transmits the p-polarized blue light beam Lb2 as it is, reflects it by the mirror 83, and then converts it from linearly polarized light (p-polarized light) to circularly polarized light (left-circularly polarized light) by the quarter wavelength plate 84. ) And then incident on the relay lens 53.

  The relay lens 53 is configured in the same manner as the relay lens 70, and includes a movable lens 54, an actuator 54A, and a fixed lens 55 corresponding to the movable lens 71, the actuator 71A, and the fixed lens 72, respectively.

  The relay lens 53 converts the blue light beam Lb2 from parallel light into convergent light by the movable lens 54, converts the blue light beam Lb2 that has become divergent light after convergence into the convergent light again by the fixed lens 55, and changes the optical axis. Incident light is incident on a galvanometer mirror 52.

  Similarly to the relay lens 70, the relay lens 53 moves the movable lens 54 by the actuator 54 </ b> A based on the control of the control unit 21 (FIG. 5), thereby changing the convergence state of the blue light beam Lb <b> 2 emitted from the fixed lens 55. It can be changed.

  The galvanometer mirror 52 reflects the blue light beam Lb2 and makes it incident on the objective lens 51. Incidentally, when the blue light beam Lb2 is reflected, the polarization direction of the circularly polarized light is reversed, and is converted from, for example, left circularly polarized light to right circularly polarized light.

  The galvanometer mirror 52 can change the angle of the reflecting surface 52A. By adjusting the angle of the reflecting surface 52A according to the control of the control unit 21 (FIG. 5), the traveling direction of the blue light beam Lb2 is changed. It can be adjusted.

  The objective lens 51 condenses the blue light beam Lb2 and irradiates the second surface 100B of the optical disc 100 with it. This objective lens has optical characteristics similar to those of the objective lens 38, and the numerical aperture (NA) of the blue light beam Lb2 is 0.5 because of the optical distance from the relay lens 53 and the like. It will act as a condenser lens.

  At this time, the blue light beam Lb2 passes through the substrate 103 and is focused in the recording layer 101 as shown in FIG. Here, the position of the focal point Fb <b> 2 of the blue light beam Lb <b> 2 is determined by the convergence state when it is emitted from the fixed lens 55 of the relay lens 53. That is, the focal point Fb2 moves to the first surface 100A side or the second surface 100B side in the recording layer 101 according to the position of the movable lens 54, similarly to the focal point Fb1 of the blue light beam Lb1.

  Specifically, like the first surface information optical system 60, the second surface information optical system 80 is designed so that the moving distance of the movable lens 54 and the moving distance of the focal point Fb2 of the blue light beam Lb2 are substantially proportional. For example, when the movable lens 54 is moved by 1 [mm], the focal point Fb2 of the blue light beam Lb2 is moved by 30 [μm].

  In practice, the second surface information optical system 80 controls the position of the movable lens 54 in the relay lens 53 as well as the position of the movable lens 54 in the relay lens 70 by the control unit 21 (FIG. 5). The depth d2 of the focal point Fb2 (FIG. 4A) of the blue light beam Lb2 in the layer 101 is adjusted.

  At this time, in the optical disc apparatus 20, the focus on the red light beam of the objective lens 51 follows the focus Fr of the red light beam Lr1, that is, the target track, by the position control of the second surface position control optical system 50 (FIG. 8). It is made like that.

  At this time, the optical axis Lx of the blue light beam Lb2 emitted from the objective lens 51 coincides with the optical axes Lx of the red light beam Lr1 and the blue light beam Lb1 emitted from the objective lens 38.

  That is, the second surface information optical system 80 can irradiate the blue light beam Lb2 so that the focal point Fb2 of the blue light beam Lb2 is focused on the position corresponding to the target track in the recording layer 101 (that is, the back side). .

  Here, in the second surface information optical system 80, when the movable lens 54 of the relay lens 53 is position-controlled complementarily with the movable lens 71 of the relay lens 70, the focal point Fb2 of the blue light beam Lb2 is set to the blue light beam Lb1. It can be adjusted to the focal point Fb1.

  The blue light beam Lb2 is focused at the focal point Fb2, and then passes through the recording layer 101, the reflective / transmissive film 104 and the substrate 102 while diverging, and is emitted from the first surface 100A and incident on the objective lens 38. Has been made.

  As described above, the second surface information optical system 80 irradiates the blue light beam Lb2 from the second surface 100B side of the optical disc 100 to position the focal point Fb2 of the blue light beam Lb2 in the recording layer 101, and further relays the relay lens 53. The depth d2 of the focal point Fb2 is adjusted according to the position of the movable lens 54 in FIG. Hereinafter, an optical path that the blue light beam Lb2 follows in the second surface information optical system 80 is referred to as a blue light path 2.

(1-3-2-2) Reception of Blue Light Beam on First Surface The optical disc 100 transmits the blue light beam Lb2 irradiated from the objective lens 51 of the second surface information optical system 80 to the second surface 100B. The light is emitted as divergent light from the first surface 100A (details will be described later). Incidentally, the blue light beam Lb2 becomes circularly polarized light (for example, right circularly polarized light).

  At this time, in the first surface information optical system 60, as shown in FIG. 11, the blue light beam Lb2 is converged to some extent by the objective lens 38, is reflected by the dichroic prism 37, and enters the relay lens 70. Incidentally, when the blue light beam Lb2 is reflected by the reflection / transmission surface 37S, the polarization direction of the circularly polarized light is inverted, and is converted from, for example, right circularly polarized light to left circularly polarized light.

  Subsequently, the blue light beam Lb2 is converted into parallel light by the fixed lens 72 and the movable lens 71 of the relay lens 70, and further converted from circularly polarized light (left circularly polarized light) to linearly polarized light (p polarized light) by the quarter wavelength plate 69. Then, the light enters the polarizing beam splitter 68.

  The polarization beam splitter 68 reflects the blue light beam Lb2 by the reflection / transmission surface 68S in accordance with the polarization direction of the blue light beam Lb2, and causes the light to enter the condenser lens 73. The condensing lens 73 condenses the blue light beam Lb 2 and irradiates the photodetector 75 via the pinhole plate 74.

  Here, as shown in FIG. 12A, the pinhole plate 74 is arranged so that the hole 74H is separated from the focal point of the blue reproduction light beam Lb3 collected by the condenser lens 73 (FIG. 10). Therefore, the blue light beam Lb2 is almost blocked. As a result, the photodetector 75 hardly detects the amount of light of the blue light beam Lb2.

  On the other hand, when the first recording mark RM1 has been recorded on the recording layer 101, the optical disc 100 has a hologram when the focal point Fb1 of the blue light beam Lb1 is focused on the first recording mark RM1, as described above. Therefore, the blue reproduction light beam Lb3 is generated from the first recording mark RM1.

  The blue reproduction light beam Lb3 is a reproduction of the light beam irradiated in addition to the blue light beam Lb1 when the first recording mark RM1 is recorded, that is, the blue light beam Lb2 on the principle of hologram. . Therefore, the blue reproduction light beam Lb3 is finally irradiated onto the photodetector 75 by passing through the same optical path as the blue light beam Lb2 in the first surface information optical system 60.

  In this case, as shown in FIG. 12A, the pinhole plate 74 is arranged so that the focal point of the blue reproduction light beam Lb3 collected by the condenser lens 73 (FIG. 10) is located in the hole 74H. Therefore, the blue reproduction light beam Lb3 is passed as it is.

  As a result, the photodetector 75 generates the detection signal SD3 corresponding to the light quantity of the blue reproduction light beam Lb3 without being affected by the blue light beam Lb2, and supplies this to the signal processing unit 23 (FIG. 5). Has been made.

  In this case, the reproduction detection signal SD3 represents information recorded on the optical disc 100 as a recording mark RM. Therefore, the signal processing unit 23 generates reproduction information by performing predetermined demodulation processing, decoding processing, and the like on the reproduction detection signal SD3 and supplies the reproduction information to the control unit 21.

  Thus, the first surface information optical system 60 receives the blue reproduction light beam Lb3 incident on the objective lens 38 from the first surface 100A of the optical disc 100 and supplies the light reception result to the signal processing unit 23. ing. Hereinafter, an optical path that the blue reproduction light beam Lb3 follows in the first surface information optical system 60 is referred to as a blue light path 3.

(1-3-2-4) Reception of Blue Light Beam on Second Surface By the way, the blue light beam Lb1 irradiated from the objective lens 38 of the first surface information optical system 60 (FIG. 10) is an optical disc as described above. After converging once in 100 recording layers 101, it becomes divergent light and enters the objective lens 51.

  At this time, in the second surface information optical system 80, the blue light beam Lb1 is converged to some extent by the objective lens 51, then reflected by the galvanometer mirror 52 and incident on the relay lens 53. Incidentally, when the blue light beam Lb1 is reflected by the reflecting surface 78S, the polarization direction of the circularly polarized light is inverted, and is converted from, for example, left circularly polarized light to right circularly polarized light.

  Subsequently, the blue light beam Lb1 is incident on the surface 56A of the dichroic prism 56 via the fixed lens 55 of the relay lens 53. Here, the dichroic prism 56 transmits the blue light beam Lb1 due to the wavelength selectivity of the reflection / transmission surface 56S, emits it from the surface 54C, and makes it incident on the movable lens 54.

  Thereafter, the blue light beam Lb1 is converted into parallel light by the movable lens 54, further converted from circularly polarized light (right circularly polarized light) to linearly polarized light (s polarized light) by the quarter wavelength plate 84, and then reflected by the mirror 83. Then, the light enters the polarization beam splitter 82.

  The polarization beam splitter 82 reflects the blue light beam Lb1 according to the polarization direction of the blue light beam Lb1 and makes it incident on the condenser lens 85. The condensing lens 85 converges the blue light beam Lb1 and irradiates the photodetector 87 via the pinhole plate 86.

  Here, as shown in FIG. 12B, the pinhole plate 86 is disposed so that the hole 86H is separated from the focal point of the reproduction light beam Lb1 collected by the condenser lens 85 (FIG. 11). Therefore, the blue light beam Lb1 is almost blocked. As a result, the photodetector 87 hardly detects the amount of light of the blue light beam Lb1.

  On the other hand, when the second recording mark RM2 is recorded on the recording layer 101, the optical disc 100 has a hologram when the focal point Fb2 of the blue light beam Lb2 is focused on the second recording mark RM2, as described above. Therefore, the blue reproduction light beam Lb4 is generated from the second recording mark RM2.

  This blue reproduction light beam Lb4 is a reproduction of the light beam irradiated in addition to the blue light beam Lb2 when the second recording mark RM2 is recorded, that is, the blue light beam Lb1 on the principle of hologram. . Therefore, the blue reproduction light beam Lb4 passes through the same optical path as the blue light beam Lb1 in the second surface information optical system 80, and is finally irradiated to the photodetector 87.

  In this case, as shown in FIG. 12B, the pinhole plate 86 is arranged so that the focal point of the blue reproduction light beam Lb4 collected by the condenser lens 85 (FIG. 11) is located in the hole 86H. Therefore, the blue reproduction light beam Lb4 is passed as it is.

  As a result, the photodetector 87 generates the detection signal SD4 corresponding to the light quantity of the blue reproduction light beam Lb4 without being affected by the blue light beam Lb1, as in the case of the photodetector 75, and generates this detection signal SD4. 5).

  In this case, the reproduction detection signal SD4 represents information recorded on the optical disc 100 as the recording mark RM. Therefore, the signal processing unit 23 generates reproduction information by performing predetermined demodulation processing, decoding processing, and the like on the reproduction detection signal SD4 and supplies the reproduction information to the control unit 21.

  As described above, the second surface information optical system 80 receives the blue reproduction light beam Lb4 incident on the objective lens 51 from the second surface 100B of the optical disc 100 and supplies the light reception result to the signal processing unit 23. ing. Hereinafter, the optical path that the blue reproduction light beam Lb2 follows in the second surface information optical system 80 is referred to as a blue light path 4.

(1-3-3) Adjustment of Optical Path Length By the way, as described above, the optical pickup 26 of the optical disc device 20 records the blue light beam from the blue light beam Lb0 by the polarizing beam splitter 65 (FIG. 9) when recording information. By separating Lb1 and Lb2 and causing the blue light beams Lb1 and Lb2 to interfere with each other in the recording layer 101 of the optical disc 100, the recording mark RM is recorded at the target mark position in the recording layer 101. .

  The laser diode 61 that emits the blue light beam Lb0 has a recording mark RM as a hologram correctly recorded on the recording layer 101 of the optical disc 100 in accordance with general hologram forming conditions. The length needs to be equal to or larger than the hologram size (that is, the height RMh of the recording mark RM).

  In practice, in the laser diode 61, like a general laser diode, this coherent length is a value obtained by multiplying the length of a resonator (not shown) provided in the laser diode 61 by the refractive index of the resonator. Therefore, it is considered to be approximately 100 [μm] to 1 [mm].

  On the other hand, in the optical pickup 26, the blue light beam Lb1 passes through the optical path in the first surface information optical system 60 (FIG. 10), is irradiated from the first surface 100A side of the optical disc 100, and the blue light beam Lb2 is second. The light is irradiated from the second surface 100B side of the optical disc 100 through the optical path in the surface information optical system 80 (FIG. 11). That is, in the optical pickup 26, since the optical paths of the blue light beams Lb1 and Lb2 are different from each other, a difference occurs in the optical path length (that is, the length of the optical path from the laser diode 61 to the target mark position).

  Further, in the optical pickup 26, as described above, the depth of the target mark position (target depth) in the recording layer 101 of the optical disc 100 is adjusted by adjusting the positions of the movable lenses 71 and 54 in the relay lenses 70 and 53. It has been made to change. At this time, the optical pickup 26 changes the optical path lengths of the blue light beams Lb1 and Lb2 by changing the depth of the target mark position.

  However, in order to form an interference pattern in the optical pickup 26, the difference in optical path length between the blue light beams Lb1 and Lb2 is reduced from the coherent length (ie, approximately 100 [μm] to 1 [mm] depending on the general hologram forming conditions. ]) It needs to be as follows.

  Therefore, the control unit 21 (FIG. 5) adjusts the optical path length of the blue light beam Lb1 by controlling the position of the movable mirror 67. In this case, the control unit 21 uses the relationship between the position of the movable lens 71 in the relay lens 70 and the depth of the first target mark position, and moves the movable mirror 67 according to the position of the movable lens 71, thereby The optical path length of the blue light beam Lb1 is changed.

  As a result, in the optical pickup 26, the difference in optical path length between the blue light beams Lb1 and Lb2 can be suppressed to be equal to or less than the coherent length, and the first recording mark made of a good hologram at the first target mark position PS1 in the recording layer 101. RM1 can be recorded.

  As described above, the control unit 21 of the optical disc apparatus 20 controls the position of the movable mirror 67 to suppress the difference in optical path length between the blue light beams Lb1 and Lb2 in the optical pickup 26 to be equal to or less than the coherent length. A good recording mark RM can be recorded at a target mark position in 100 recording layers 101.

(1-4) Recording and Reproducing Information (1-4-1) Recording Information on Optical Disc When recording information on the optical disc 100, the control unit 21 (FIG. 5) of the optical disc apparatus 20 is externally connected as described above. When an information recording command, recording information, and recording address information are received from a device (not shown) or the like, the driving command and recording address information are supplied to the drive control unit 22 and the recording information is supplied to the signal processing unit 23.

  At this time, the drive controller 22 causes the first surface position control optical system 30 (FIG. 8) of the optical pickup 26 to irradiate the red light beam Lr1 from the first surface 100A side of the optical disc 100, and the red reflected light that is the reflected light. Based on the detection result of the beam Lr3, focus control and tracking control (that is, position control) of the objective lens 38 are performed, thereby causing the focus Fr of the red light beam Lr1 to follow the target track corresponding to the recording address information.

  At this time, the focal point Fb1 of the blue light beam Lb1 is focused by the position-controlled objective lens 38, thereby being positioned behind the target track.

  Further, the control unit 21 adjusts the depth d1 of the focal point Fb1 (FIG. 4A) to the target depth by adjusting the position of the movable lens 71 in the relay lens 70. As a result, the focal point Fb1 of the blue light beam Lb1 is adjusted to the first target mark position PS1.

  On the other hand, the control unit 21 controls the shutter 81 of the second surface information optical system 80 (FIG. 11) to transmit the blue light beam Lb2 and to irradiate the blue light beam Lb2 from the second surface 100B side of the optical disc 100. .

  Further, the control unit 21 performs focus control of the objective lens 51 based on the detection result of the red transmitted light beam Lr2 emitted from the first surface 100A side of the optical disc 100 by the second surface position control optical system 50 (FIG. 8). By performing tracking control and tangential control by the galvanometer mirror 52, the focal point of the objective lens 51 relating to the red light beam is made to coincide with the focal point Fr of the red light beam Lr1 in the reflection / transmission film 104.

  At this time, the focal point Fb2 of the blue light beam Lb2 is focused by the position-controlled objective lens 51, and is located behind the target track, like the focal point Fb1 of the blue light beam Lb1.

  The control unit 21 adjusts the depth d2 of the blue light beam Lb2 (FIG. 4A) by adjusting the position of the movable lens 54 in the relay lens 53 in accordance with the position of the movable lens 71 in the relay lens 70. To do. As a result, the focal point Fb2 of the blue light beam Lb2 is adjusted to the second target mark position PS2.

  Here, the control unit 21 adjusts the positions of the movable lenses 71 and 54 of the relay lenses 70 and 53 to complementary positions, thereby adjusting the focus Fb2 of the blue light beam Lb2 to the focus Fb1 of the blue light beam Lb1.

  In addition, the control unit 21 adjusts the position of the movable mirror 67 according to the position of the movable lens 54 in the relay lens 70, and suppresses the difference in optical path length between the blue light beams Lb1 and Lb2 to be equal to or less than the coherent length.

  Thus, the control unit 21 of the optical disc apparatus 20 can satisfactorily form the first recording mark RM1 due to the interference of the blue light beams Lb1 and Lb2 with respect to the first target mark position PS1 in the recording layer 101 of the optical disc 100. .

  Here, the signal processing unit 23 (FIG. 4) generates a recording signal representing binary data of a value “0” or “1” based on recording information supplied from an external device (not shown) or the like. Accordingly, for example, the laser diode 61 emits the blue light beam Lb0 when the recording signal has the value “1”, and does not emit the blue light beam Lb0 when the recording signal has the value “0”. .

  Thus, in the optical disc apparatus 20, when the recording signal has the value “1”, the first recording mark RM1 is formed at the first target mark position PS1 in the recording layer 101 of the optical disc 100, and when the recording signal has the value “0”. Since the first recording mark RMRM1 is not formed at the first target mark position PS1, the value “1” or “0” of the recording signal at the first target mark position PS1 depends on the presence or absence of the first recording mark RM1. As a result, the record information can be recorded on the recording layer 101 of the optical disc 100.

(1-4-2) Reproduction of Information from Optical Disc When reproducing information from the optical disc 100, the control unit 21 (FIG. 5) of the optical disc apparatus 20 uses the first surface of the optical pickup 26 as in the case of recording information. The position control optical system 30 (FIG. 8) irradiates the red light beam Lr1 from the first surface 100A side of the optical disc 100, and based on the detection result of the red reflected light beam Lr3 that is the reflected light, the drive control unit 22 Focus control and tracking control (that is, position control) of the lens 38 are performed.

  Further, the control unit 21 performs focus control of the objective lens 51 based on the detection result of the red transmitted light beam Lr2 emitted from the first surface 100A side of the optical disc 100 by the second surface position control optical system 50 (FIG. 8). By performing tracking control and tangential control by the galvanometer mirror 52, the focal point of the objective lens 51 relating to the red light beam coincides with the focal point Fr1 of the red light beam Lr1 in the reflection / transmission film 104.

  Further, the control unit 21 irradiates the blue light beam Lb1 from the first surface 100A side of the optical disc 100 by the first surface information optical system 60 (FIG. 10). At this time, the focal point Fb1 of the blue light beam Lb1 is focused by the position-controlled objective lens 38, thereby being positioned behind the target track.

  Further, the control unit 21 adjusts the position of the movable lens 71 in the relay lens 70 to adjust the focus Fb1 of the blue light beam Lb1 to the first target mark position PS1.

  Incidentally, the control unit 21 is configured to prevent erroneous erasure of the recording mark RM by the blue light beam Lb1 by suppressing the emission power of the laser diode 61 during reproduction.

  In addition, the control unit 21 irradiates the blue light beam Lb2 from the second surface 100B side of the optical disc 100 by the second surface information optical system 80 (FIG. 10). At this time, the focal point Fb2 of the blue light beam Lb2 is condensed by the position-controlled objective lens 51, thereby being positioned behind the target track.

  Further, the control unit 21 adjusts the position of the movable lens 54 in the relay lens 53 independently of the position of the movable lens 71 in the relay lens 70, so that the focal point Fb2 of the blue light beam Lb2 is different from the first target mark position PS1. 2 Set to the target mark position PS2.

  That is, the optical pickup 26 irradiates the first target mark position PS1 and the second target mark position PS2 in the recording layer 101 of the optical disc 100 with blue light beams Lb1 and Lb2 as so-called reference lights from both sides. Accordingly, when the first recording mark RM1 and the second recording mark RM2 are respectively recorded at the first target mark position PS1 and the second target mark position PS2, the blue reproduction light beam Lb3 and Lb4 is generated on the first surface 100A side and the second surface 100B side, respectively.

  At this time, the optical disc apparatus 20 detects the light amounts of the blue reproduction light beam Lb3 and the blue reproduction light beam Lb4 by the first surface information optical system 60 and the second surface information optical system 80, respectively, thereby detecting the detection signals SD3 and SD4, respectively. Generate.

  On the other hand, when the first recording mark RM1 is not recorded at the first target mark position PS1, the optical disc apparatus 20 does not generate the blue reproduction light beam Lb3 from the first target mark position PS1, so the first surface information optical The system 60 generates a detection signal SD3 indicating that the blue reproduction light beam Lb3 has not been received.

  Similarly, when the second recording mark RM2 is not recorded at the second target mark position PS2, the optical disc apparatus 20 does not generate the blue reproduction light beam Lb4 from the second target mark position PS2. The optical system 80 generates a detection signal SD4 indicating that the blue reproduction light beam Lb4 has not been received.

  Thereafter, the signal processing unit 23 generates reproduction information by performing various signal processing such as the above-described demodulation processing and decoding processing on the detection signals SD3 and SD4, and supplies the reproduction information to the control unit 21. .

  The control unit 21 integrates a plurality of pieces of reproduction information into one piece of reproduction information by a predetermined information integration process, and then sends the information to an external device (not shown). As a result, the optical disc apparatus 20 can apparently obtain a reproduction speed that is twice as high as the reproduction by the blue reproduction light beams Lb3 and Lb4 at a normal reproduction speed.

  The optical disc device 20 reproduces information based on only one piece of reproduction information obtained by the blue light beam Lb1 and the blue reproduction light beam Lb3 by controlling the liquid crystal panel 81 to block the blue light beam Lb2, for example. You may make it do.

(1-5) Operation and Effect In the above configuration, the control unit 21 of the optical disc apparatus 20 according to the first embodiment performs the optical pickup 26 when recording information on the optical disc 100 and reproducing information from the optical disc 100. The first surface position control optical system 30 (FIG. 8) irradiates the red light beam Lr1 from the first surface 100A side of the optical disk 100, and based on the detection result of the reflected red light beam Lr3, the objective lens By performing the focus control and tracking control (ie, position control) 38, the focus Fr of the red light beam Lr1 follows the target track corresponding to the recording address information.

  Further, the control unit 21 performs focus control of the objective lens 51 based on the detection result of the red transmitted light beam Lr2 emitted from the first surface 100A side of the optical disc 100 by the second surface position control optical system 50 (FIG. 8). Then, by performing tracking control and tangential control by the galvanometer mirror 52, the focal point of the objective lens 51 relating to the red light beam coincides with the focal point Fr of the red light beam Lr1 in the reflection / transmission film 104.

  Further, when recording information on the optical disc 100, the control unit 21 uses the two blue light beams Lb1 (FIG. 10) and Lb2 (FIG. 11) to position the movable lenses 71 and 54 of the relay lenses 70 and 53. Are controlled in a complementary manner, and the focal points Fb1 and Fb2 of the blue light beams Lb1 and Lb2 are both adjusted to the first target mark position PS1 (FIG. 4A), so that the first in the recording layer 101 of the optical disc 100 is obtained. A recording mark RM1 is formed.

  On the other hand, when reproducing information from the optical disc 100, the control unit 21 controls the positions of the movable lenses 71 and 54 of the relay lenses 70 and 53 independently of each other, and the focal points Fb1 and Fb1 of the two blue light beams Lb1 and Lb2. By aligning Fb2 with the first target mark position PS1 and the second target mark position PS2 which are different from each other (FIG. 4B), the first recording marks located at the depths d1 and d2 in the recording layer 101 of the optical disc 100 Blue reproduction light beams Lb3 and Lb4 are generated from RM1 and the second recording mark RM2, respectively.

  At this time, the control unit 21 detects the light amounts of the blue reproduction light beams Lb3 and Lb4 by the photodetectors 75 and 87, respectively, and integrates two reproduction signals obtained by performing predetermined signal processing to double the reproduction signals. One reproduction signal having a reproduction speed is generated.

  Accordingly, the control unit 21 of the optical disc apparatus 20 can record only one recording mark RM at the same time due to the fundamental restriction of information recording using a hologram when recording information, but at the same time two recording marks can be recorded at the time of reproducing information. That is, it is possible to generate blue reproduction light beams Lb3 and Lb4 from the first recording mark RM1 and the second recording mark RM2, respectively, to obtain two systems of reproduction signals in parallel, and to integrate these, the double speed reproduction signal Can be obtained.

  At this time, the control unit 21 merely controls the positions of the movable lenses 71 and 54 of the relay lenses 70 and 53 that are complementary to each other when information is recorded, independently of each other when information is reproduced. Since the focal points Fb1 and Fb2 of the beams Lb1 and Lb2 can be focused on the desired first recording mark RM1 and second recording mark RM2, respectively, optical components for adjusting the focal points Fb1 and Fb2 independently of each other No need to add

  As a result, the optical disk apparatus 20 has an upper limit on the rotational speed of the optical disk 100 due to the physical strength of the optical disk 100 or surface blurring during high-speed rotation, and the upper limit of the information reproduction speed is inevitably determined. Even so, the apparent reproduction speed can be improved by a factor of about two by simultaneously reading and integrating the two systems of information.

  Originally, the optical disk apparatus 20 requires two systems of blue light beams Lb1 and Lb2 in principle when recording the recording mark RM on the optical disk 100. Has an optical system. For this reason, the optical disk apparatus 20 does not need to add another optical system in order to perform two systems simultaneous reproduction, and the other optical system that has not been used when reproducing information using only one optical system is used. It can be used effectively.

  For example, the control unit 21 of the optical disc apparatus 20 disassembles information to be recorded into two systems at the time of recording information, and information corresponding to the disassembled target mark positions at different depths in the same target track. By recording each of them, the original information can be obtained by integrating the two systems of information obtained at the time of reproduction.

  Further, since the reflection / transmission film 104 on which the track is formed has wavelength selectivity, the optical disc 100 can reflect the red light beam Lr1 at about a half rate and transmit the red light beam Lr1 at a half rate. The beams Lb1 and Lb2 and the blue reproduction light beams Lb3 and Lb4 can be transmitted with high transmittance.

  Accordingly, the optical disc apparatus 20 can receive the red reflected light beam Lr3 and the red transmitted light beam Lr2 by the first surface position control optical system 30 and the second surface position control optical system 50 (FIG. 8), respectively. The positions of the objective lenses 38 and 51 can be controlled so that both the focal point Fr of the red light beam Lr1 and the focal point of the objective lens 51 relating to the red light beam follow the target track.

  By the way, as in the patent application (Japanese Patent Application No. 2006-249804) by the same inventor and the same applicant as the present invention, the position of the objective lens 51 is controlled by receiving the blue light beam Lb1 after passing through the optical disc 100. For example, when the code to be recorded is the value “0” and the recording mark RM is not formed, the position of the objective lens 51 cannot be temporarily controlled because the blue light beam Lb1 is not irradiated. In particular, when the value “0” continues for a while, the position of the objective lens 51 cannot be controlled for a long period of time, so that the objective lens 51 may be greatly deviated from the ideal position.

  On the other hand, the optical disk apparatus 20 according to the present invention controls the position of the objective lens 51 using the red transmitted light beam Lr2 based on the red light beam Lr1 dedicated to position control irradiated with a predetermined light amount. It is possible to always perform stable position control without being influenced by the above.

  According to the above configuration, when the control unit 21 of the optical disc device 20 according to the first embodiment records information on the optical disc 100, the control unit 21 selects the focal points Fb1 and Fb2 of the two blue light beams Lb1 and Lb2. Also, the first recording mark RM1 is formed by causing interference with the first target mark position PS1, while when reproducing information from the optical disc 100, the focal points Fb1 and Fb2 of the two blue light beams Lb1 and Lb2 are different from each other. By aligning with the first target mark position PS1 and the second target mark position PS2, respectively, the blue reproduction light beam from the first recording mark RM1 and the second recording mark RM2 at different positions in the recording layer 101 of the optical disc 100, respectively. Two playback signals can be obtained by generating Lb3 and Lb4. It is possible to generate one reproduction signal becomes twice the playback speed by.

(2) Second Embodiment (2-1) Configuration of Optical Disc In the second embodiment, the optical disc 100 (FIGS. 3 and 4) in the first embodiment is used as it is. The recording method is different from that of the first embodiment.

  That is, in the second embodiment, as a preliminary formatting process, the blue light beams Lb1 and Lb2 having a wavelength of 405 [nm] are entirely irradiated from both the first surface 100A side and the second surface 100B side. Thus, as schematically shown in FIG. 13A, a hologram is formed in the recording layer 101 substantially uniformly throughout.

  When the recording layer 101 is focused and irradiated with a blue light beam Lb1 having a predetermined intensity, a hologram near the focal point Fb1 of the blue light beam Lb1 as schematically shown in FIG. 13B. Is destroyed, and a recording mark RM is formed which is a portion where the hologram is destroyed.

  As a result, as schematically shown in FIG. 13C, when the blue light beam Lb1 having the same wavelength as that at the time of formatting is irradiated on the portion of the recording medium 101 where the recording mark RM is not formed, Due to the properties as a hologram, the reproduction light beam Lb3 is generated from the irradiated portion of the blue light beam Lb1.

  On the other hand, since the hologram is destroyed at the location where the recording mark RM is recorded, even if the blue light beam Lb1 is irradiated, it does not exhibit the properties as a hologram, and the blue reproduction light beam Lb3 is not generated.

  Therefore, for example, the values “0” and “1” when the information is displayed in binary are assigned to “without recording mark RM (ie, hologram not destroyed)” and “with recording mark RM (ie, hologram destroyed)”, respectively. As a result, information can be recorded on and reproduced from the recording medium M. Incidentally, in this case, as compared with the first embodiment, the value “0” or “1” is oppositely associated with the presence or absence of the hologram, that is, the presence or absence of the blue reproduction light beam.

  As described above, in the recording and reproduction of information using the hologram, the hologram is formed as a whole by being formatted in advance, and then in one of the recording and reproduction of information, one beam is used as in the blue light beam Lb1. The light beam is used.

(2-2) Configuration of Optical Disc Device Next, the optical disc device 120 in the present embodiment will be described. The optical disc apparatus 120 has a control unit 121 instead of the control unit 21 and an optical pickup 126 instead of the optical pickup 26, as compared with the optical disc apparatus 20 in the first embodiment shown in FIG. Although the points are different, the other parts are almost the same.

  Like the control unit 21, the control unit 121 is mainly configured by a CPU (not shown), reads various programs such as a basic program and an information recording program from a ROM (not shown), and develops them in a RAM (not shown). Various processes such as an information recording process are executed.

  The optical disc apparatus 120 records information at a position corresponding to the target track in the recording layer 101 of the optical disc 200 by controlling the optical pickup 126 by the control unit 121 as in the optical disc apparatus 20 in the first embodiment. In addition, information is reproduced from a position corresponding to the target track.

(2-3) Configuration of Optical Pickup Next, the configuration of the optical pickup 126 will be described. The optical pickup 126 is greatly different in that a laser diode 181 equivalent to the laser diode 61 in the optical pickup 26 is added, as shown in FIG.

  That is, the optical pickup 126 is similar to the optical pickup 26 (FIG. 7) in terms of the first surface position control optical system 30 and the second surface position control optical system 50, but the first surface information optical system 60 and Instead of the second surface information optical system 80, a first surface information optical system 160 and a second surface information optical system 180 are provided.

(2-3-1) Irradiation of blue light beam on first surface As in the first embodiment, the laser diode 61 of the first surface information optical system 60 emits blue laser light having a wavelength of about 405 [nm]. It is made to be able to do. Actually, as shown in FIG. 15 corresponding to FIG. 14, the laser diode 61 emits a blue light beam Lb 1 made of divergent light based on the control of the control unit 21 (FIG. 5) and makes it incident on the collimator lens 62.

  The blue light beam Lb1 is converted from diverging light into parallel light by the collimator lens 62, and the polarization direction is rotated by a predetermined angle by the half-wave plate 63 to be, for example, s-polarized light, and then the intensity distribution is shaped by the anamorphic prism 64. Then, the light is incident on the surface 68C of the polarization beam splitter 68.

  The polarization beam splitter 68 reflects or transmits the light beam on the reflection / transmission surface 68S at a different rate depending on the polarization direction of the light beam. For example, the reflection / transmission surface 68S reflects an s-polarized light beam and transmits a p-polarized light beam.

  In practice, the polarization beam splitter 68 reflects the blue light beam Lb1 of s-polarized light by the reflection / transmission surface 68S and makes it incident on the quarter-wave plate 69. The quarter wavelength plate 69 converts the blue light beam Lb1 from linearly polarized light (s-polarized light) to circularly polarized light (right circularly polarized light) and then enters the relay lens 70.

  Thereafter, the blue light beam Lb1 is irradiated onto the first surface 100A of the optical disc 100 from the objective lens 38 through the same optical path as in the first embodiment.

(2-3-2) Irradiation of Blue Light Beam on Second Surface The second surface information optical system 180 includes a laser diode 61, a collimator lens 62, a half-wave plate 63, an anamorphic prism 64, and a polarization beam splitter 68, respectively. A corresponding laser diode 181, collimator lens 182, half-wave plate 183, anamorphic prism 184, and polarizing beam splitter 185 are provided.

  As shown in FIG. 16 corresponding to FIG. 14, the laser diode 181 emits the blue light beam Lb2 and makes it incident on the polarization beam splitter 185 via the collimator lens 182, the half-wave plate 183, and the anamorphic prism 184 sequentially. . At this time, the blue light beam Lb2 is converted into, for example, p-polarized light by the half-wave plate 183.

  The polarization beam splitter 185 reflects or transmits the light beam at the reflection / transmission surface 185S at a different rate depending on the polarization direction of the light beam, similarly to the reflection / transmission surface 82S of the polarization beam splitter 82 in the first embodiment. Has been made. For example, the reflection / transmission surface 185S reflects an s-polarized light beam and transmits a p-polarized light beam.

    In practice, the polarizing beam splitter 185 transmits the blue light beam Lb2 that is p-polarized light through the reflection / transmission surface 185S and makes it incident on the quarter-wave plate 84. The quarter-wave plate 84 converts the blue light beam Lb2 from linearly polarized light (p-polarized light) to circularly polarized light (left-handed circularly polarized light) and then enters the relay lens 53.

  Thereafter, the blue light beam Lb2 is irradiated from the objective lens 51 onto the second surface 100B of the optical disc 100 through the same optical path as in the first embodiment. Incidentally, the blue light beam Lb2 becomes circularly polarized light (for example, right circularly polarized light) as in the first embodiment.

(2-3-3) Reception of Blue Light Beam on First Surface When the first recording mark RM1 is not recorded on the recording layer 101 and the hologram remains on the optical disc 100, as described above, the blue light When the focal point Fb1 of the beam Lb1 is focused on the first target mark position PS1, the blue reproduction light beam Lb3 is generated from the first target mark position PS1 due to the property as a hologram.

  The blue reproduction light beam Lb3 is finally irradiated to the photodetector 75. The photodetector 75 generates a detection signal SD3 corresponding to the light amount of the blue reproduction light beam Lb3, and supplies the detection signal SD3 to the signal processing unit 23 (FIG. 5). The signal processing unit 23 generates reproduction information by performing predetermined demodulation processing, decoding processing, and the like on the reproduction detection signal SD3, and supplies the reproduction information to the control unit 21.

(2-3-4) Receiving the blue light beam on the second surface On the other hand, in the optical disc 100, when the second recording mark RM2 is not recorded on the recording layer 101 and the hologram remains, as described above, When the focal point Fb2 of the blue light beam Lb2 is focused on the second target mark position PS2, the blue reproduction light beam Lb4 is generated from the second target mark position PS2 due to the property as a hologram.

  The blue reproduction light beam Lb4 is finally irradiated to the photodetector 87. The photodetector 87 generates a detection signal SD4 corresponding to the light quantity of the blue reproduction light beam Lb4 and supplies it to the signal processing unit 23 (FIG. 5). The signal processing unit 23 generates reproduction information by performing predetermined demodulation processing and decoding processing on the reproduction detection signal SD4, and supplies the reproduction information to the control unit 21.

(2-4) Recording and Reproducing Information (2-4-1) Recording Information on Optical Disc When recording information on the optical disc 100, the control unit 121 (FIG. 5) of the optical disc device 120 is externally connected as described above. When an information recording command, recording information, and recording address information are received from a device (not shown) or the like, the driving command and recording address information are supplied to the drive control unit 22 and the recording information is supplied to the signal processing unit 23.

  At this time, similarly to the first embodiment, the drive controller 22 causes the first surface position control optical system 30 (FIG. 8) of the optical pickup 126 to irradiate the red light beam Lr1 from the first surface 100A side of the optical disc 100. The focus Fr of the red light beam Lr1 corresponds to the recording address information by performing focus control and tracking control (that is, position control) of the objective lens 38 based on the detection result of the red reflected light beam Lr3 that is the reflected light. Follow the target track.

  At this time, the focal point Fb1 of the blue light beam Lb1 is focused by the position-controlled objective lens 38, thereby being positioned behind the target track.

  Further, the control unit 121 adjusts the depth d1 of the focal point Fb1 (FIG. 4A) to the target depth by adjusting the position of the movable lens 71 in the relay lens 70. As a result, the focal point Fb1 of the blue light beam Lb1 is adjusted to the first target mark position PS1.

  Further, the control unit 121 performs focus control of the objective lens 51 based on the detection result of the red transmitted light beam Lr2 emitted from the first surface 100A side of the optical disc 100 by the second surface position control optical system 50 (FIG. 8). By performing tracking control and tangential control by the galvanometer mirror 52, the focal point of the objective lens 51 relating to the red light beam is made to coincide with the focal point Fr of the red light beam Lr1 in the reflection / transmission film 104.

  At this time, the focal point Fb2 of the blue light beam Lb2 is focused by the position-controlled objective lens 51, and is located behind the target track, like the focal point Fb1 of the blue light beam Lb1.

  Further, the control unit 121 adjusts the position of the movable lens 54 in the relay lens 53 independently of the position of the movable lens 71 in the relay lens 70, thereby adjusting the depth d2 of the blue light beam Lb2 (FIG. 4A). adjust. As a result, the focal point Fb2 of the blue light beam Lb2 is adjusted to the second target mark position PS2.

  In the second embodiment, the control unit 121 adjusts the positions of the movable lenses 71 and 54 of the relay lenses 70 and 53 independently of each other even when information is recorded.

  As a result, the control unit 121 of the optical disc apparatus 120 can form the first recording mark RM1 at the first target mark position PS1 by the blue light beam Lb1 in the recording layer 101 of the optical disc 100, and at the same time. Thus, the second recording mark RM2 can be formed at the second target mark position PS2 by the blue light beam Lb2.

  By the way, the signal processing unit 23 divides the recording information into the first divided recording information and the second divided recording information by a predetermined data dividing process, and binary data (that is, the value “0” or “1”) constituting each divided recording information. ) Are respectively generated and supplied to the laser diodes 61 and 181, respectively.

  That is, the laser diode 61 does not emit the blue light beam Lb1 when the first divided recording information has the value “0”, and emits the blue light beam Lb1 when the first divided recording information has the value “1”. Similarly, the laser diode 181 does not emit the blue light beam Lb2 when the second divided recording information has the value “0”, and emits the blue light beam Lb2 when the second divided recording information has the value “1”.

  As a result, the optical disc device 120 does not record anything when the first divided recording information is the value “0” with respect to the first target mark position PS1 in the recording layer 101 of the optical disc 100, leaving a hologram, and the first divided recording information. When the value is “1”, the first recording mark RM1 can be recorded. At the same time, when the second divided recording information is the value “0”, no recording can be performed on the second target mark position PS2. The second recording mark RM2 can be recorded when the hologram is left and the second divided recording information is the value “1”.

  Incidentally, the control unit 121 divides and records information into two recording mark layers (hereinafter referred to as divided recording), for example, on the TOC (Table of Contents) of the optical disc 100 and the like. Information related to correspondence is recorded as management information.

  As described above, the optical disc apparatus 120 has two systems in which the recording information is divided into two positions corresponding to the target track in the recording layer 101 of the optical disc 100, that is, the first target mark position PS1 and the second target mark position PS2. As the divided recording information, the first recording mark RM1 and the second recording mark RM2 independent of each other can be recorded simultaneously.

(2-4-2) Reproduction of Information from Optical Disc When the controller 121 (FIG. 5) of the optical disc apparatus 120 reproduces information from the optical disc 100, the first surface position control optical system is the same as when recording information. 30 (FIG. 14) irradiates the red light beam Lr1 from the first surface 100A side of the optical disc 100, and based on the detection result of the red reflected light beam Lr3 that is the reflected light, the drive control unit 22 focuses the objective lens 38. Control and tracking control (that is, position control) are performed.

  The control unit 121 performs focus control of the objective lens 51 based on the detection result of the red transmitted light beam Lr2 emitted from the first surface 100A side of the optical disc 100 by the second surface position control optical system 50 (FIG. 14). By performing tracking control and tangential control by the galvanometer mirror 52, the focal point of the objective lens 51 relating to the red light beam coincides with the focal point Fr1 of the red light beam Lr1 in the reflection / transmission film 104.

  Here, the first surface information optical system 160 and the second surface information optical system 180 (FIGS. 15 and 16) indicate the position of the movable lens 71 in the relay lens 70, as in the information optical system 60 in the first embodiment. By adjusting, the focal point Fb1 of the blue light beam Lb1 is adjusted to the first target mark position PS1, and at the same time, the position of the movable lens 54 in the relay lens 53 is adjusted independently of the position of the movable lens 71 in the relay lens 70 to adjust the blue light. By adjusting the focus Fb2 of the beam L21 to the second target mark position PS2, from the first target mark position PS1 and the second target mark position PS2, depending on the presence or absence of the first recording mark RM1 and the second recording mark RM2, Blue reproduction light beams Lb3 and Lb4 are simultaneously generated, respectively.

  The first surface information optical system 160 and the second surface information optical system 180 detect the light amounts of the blue reproduction light beams Lb3 and Lb4 by the photodetectors 75 and 87, respectively, and the detection signals SD3 and SD4 according to the detected light amounts. Are generated and supplied to the signal processing unit 23 (FIG. 6).

  Thus, the optical pickup 126 focuses the blue light beams Lb1 and Lb2 as so-called reference lights on the first target mark position PS1 and the second target mark position PS2 in the recording layer 101 of the optical disc 100, respectively. When the first recording mark RM1 or the second recording mark RM2 is not recorded, the blue reproduction light beams Lb3 and Lb4 are respectively generated, the respective light amounts are detected by the photodetectors 75 and 87, and the detection signals SD3 and SD4 are generated. Has been made to get.

  Thus, in the optical disc apparatus 120, depending on whether the first recording mark RM1 or the second recording mark RM2 is recorded at the first target mark position PS1 and the second target mark position PS2 in the recording layer 101 of the optical disc 100. Each of the values “1” or “0” can be independently recognized as information.

  In addition, when information is recorded on the optical disc 100 in a divided manner, the control unit 121 integrates two types of reproduction information into one piece of reproduction information by a predetermined information integration process, as in the first embodiment. The data is sent to an external device (not shown). As a result, similarly to the first embodiment, the optical disc apparatus 120 can apparently obtain a reproduction speed that is twice as high by only reproducing at the normal reproduction speed with the blue reproduction light beams Lb3 and Lb4.

  Note that the optical disc apparatus 120 is based on only one piece of reproduction information obtained by the blue light beam Lb1 and the blue reproduction light beam Lb3 by not emitting the blue light beam Lb2 from the laser diode 71 under the control of the control unit 121, for example. The information may be reproduced.

(2-5) Operation and Effect In the above configuration, the control unit 121 of the optical disc apparatus 120 according to the second embodiment performs an optical pickup when recording information on the optical disc 100 and reproducing information from the optical disc 100. The first surface position control optical system 30 (FIG. 14) 126 irradiates the red light beam Lr1 from the first surface 100A side of the optical disc 100, and based on the detection result of the red reflected light beam Lr3, which is the reflected light, the objective. By performing focus control and tracking control (that is, position control) of the lens 38, the focus Fr of the red light beam Lr1 follows the target track corresponding to the recording address information.

  The control unit 121 controls the focus of the objective lens 51 based on the detection result of the red transmitted light beam Lr2 emitted from the first surface 100A side of the optical disc 100 by the second surface position control optical system 50 (FIG. 14). Then, by performing tracking control and tangential control by the galvanometer mirror 52, the focal point of the objective lens 51 relating to the red light beam coincides with the focal point Fr of the red light beam Lr1 in the reflection / transmission film 104.

  Furthermore, when recording information on the optical disc 100, the control unit 121 uses the two blue light beams Lb1 (FIG. 15) and Lb2 (FIG. 16) to position the movable lenses 71 and 54 of the relay lenses 70 and 53. Are controlled independently of each other, and the focal points Fb1 and Fb2 of the blue light beams Lb1 and Lb2 are respectively adjusted to the first target mark position PS1 and the second target mark position PS2 (FIG. 4B), thereby A first recording mark RM1 and a second recording mark RM2 are formed in parallel in the recording layer 101.

  Further, when reproducing information from the optical disc 100, the control unit 121 controls the positions of the movable lenses 71 and 54 of the relay lenses 70 and 53 independently of each other, and focuses Fb1 and Fb2 of the two blue light beams Lb1 and Lb2. Are matched with the first target mark position PS1 and the second target mark position PS2 which are different from each other (FIG. 4B), thereby the first recording mark RM1 positioned at the depths d1 and d2 in the recording layer 101 of the optical disc 100. And blue reproduction light beams Lb3 and Lb4 are generated from the second recording mark RM2, respectively.

  Accordingly, the control unit 121 of the optical disc apparatus 120 performs two independent recordings for two target mark positions corresponding to the target track of the optical disc 100 and having different depths, both during recording and reproduction of information. Marks can be recorded simultaneously, and two independent reproduction signals can be obtained from the two target mark positions.

  At this time, the controller 121 divides the recording information into the first divided recording information and the second divided recording information at the time of recording the information and records the divided information at the first target mark position PS1 and the second target mark position PS2, respectively. By integrating the detection signals SD3 and SD4 respectively obtained from the first target mark position PS1 and the second target mark position PS2 at the time of reproduction and generating one reproduction signal at a double reproduction speed, apparently 2 Double recording speed and double reproduction speed can be obtained.

  As a result, the optical disc apparatus 20 has an upper limit on the rotational speed of the optical disc 100 due to physical strength of the optical disc 100 and surface blurring during high-speed rotation, and the formation and reading of the recording mark RM due to optical constraints and physical constraints. Even if the minimum required time is inevitably determined, the information is divided into two systems and recorded, and the information of the two systems is read and integrated at the same time. The speed and playback speed can be increased by a factor of about two.

  In addition, since the reflection / transmission film 104 on which the track is formed has wavelength selectivity, the optical disc 100 can reflect the red light beam Lr1 at a rate of about half and transmit the red light beam Lr1 at a rate of about half. The beams Lb1 and Lb2 and the blue reproduction light beams Lb3 and Lb4 can be transmitted with high transmittance.

  Accordingly, the optical disk device 120 can receive the red reflected light beam Lr3 and the red transmitted light beam Lr2 by the first surface position control optical system 30 and the second surface position control optical system 50 (FIG. 14), respectively. The positions of the objective lenses 38 and 51 can be controlled so that both the focal point Fr of the red light beam Lr1 and the focal point of the objective lens 51 relating to the red light beam follow the target track.

  Furthermore, since the optical disk device 120 controls the position of the objective lens 51 using the red transmitted light beam Lr2 as in the optical disk device 20 in the first embodiment, the code to be recorded as in the case of using the blue light beam Lb1. Thus, stable position control can be performed at all times without being affected by the above.

  According to the above configuration, when the information is recorded on the optical disc 100, the control unit 121 of the optical disc device 120 according to the second embodiment divides the recording information, and the blue light beam based on each divided recording information. The first recording mark RM1 and the second recording mark RM2 are formed independently of each other by aligning the focal points Fb1 and Fb2 of Lb1 and Lb2 with the first target mark position PS1 and the second target mark position PS2 different from each other. When reproducing information, the focal points Fb1 and Fb2 of the two blue light beams Lb1 and Lb2 are adjusted to the first target mark position PS1 and the second target mark position PS2, respectively, so that the first recording mark RM1 and the second recording mark A reproduction signal obtained based on the blue reproduction light beams Lb3 and Lb4 generated according to the presence or absence of RM2 By coupling can speed both the recording speed and reproducing speed.

(3) Other Embodiments In the second embodiment described above, a hologram is previously formed as a format on the entire surface of the optical disc 100, and the recording mark RM is recorded to destroy the hologram. However, the present invention is not limited to this. For example, as shown in FIG. 17A, a recording layer made of a photopolymer having a uniform refractive index is used. By condensing the light beam, its refractive index or reflectance changes to form a recording mark RM. As shown in FIG. 17B, the recording mark is based on the change in the refractive index or reflectance of the light beam. Various optical discs, such as an optical disc capable of detecting the presence or absence of RM, can record and reproduce the recording mark RM by one light beam and can form a plurality of mark recording layers in the recording layer. You may be allowed to use

  In this case, it is only necessary that the light beam irradiating the optical disc is appropriately adjusted in light amount, irradiation time, etc. according to the type of optical disc, recording method, and the like.

  In the second embodiment described above, the two blue reproduction light beams Lb3 and Lb4 are generated through the two blue light paths, and the two reproduction signals obtained at this time are integrated and doubled. However, the present invention is not limited to this, and for example, three or four or more blue light paths are provided, and three or four or more are generated. Three or four or more reproduction signals obtained by generating the blue reproduction light beam may be integrated to obtain a reproduction speed of 3 times or 4 times or more.

  In this case, an expander is provided in each blue light path so that the focus Fb of the blue light beam Lb irradiated to the optical disc 100 can be adjusted to a different position (depth), and a pin provided immediately before the photodetector. What is necessary is just to be able to detect the light quantity of only a desired blue reproduction light beam by the hall plate.

  Furthermore, in the first and second embodiments described above, the case where different information is recorded on different mark recording layers has been described. However, the present invention is not limited to this, and for example, as shown in FIG. In the layer 101, the same information is recorded in two corresponding mark recording layers, that is, the master layers YS1, YS2,... And the mirror layers YR1, YR2,. Information may be sequentially read from the YR, and the comparison correction processing may be performed in the control units 21 and 121 and the like.

  As a result, for example, the hologram (that is, the formatted state), the recording mark RM, etc. in one of the master layer YS and the mirror layer YR is destroyed for some reason, or the detection signal SD3 or Even if SD4 represents abnormal reproduction information, it is possible to increase the possibility that correct information can be corrected in the comparison and correction process.

  Furthermore, in the first and second embodiments described above, the case where the depth of the target mark position in the optical disc 100 (that is, the distance from the reflective / transmissive film 104) is adjusted by the relay lenses 70 and 53 will be described. However, the present invention is not limited to this. For example, the target mark position can be changed by changing the depth of the target mark position by moving a single condenser lens, or by performing focus control of the objective lenses 38 and 51. You may make it change the depth of the said target mark position by other methods, such as changing the depth of a position.

  Further, in the first and second embodiments described above, the case where the optical axes of the red light beam Lr1 and the blue light beam Lb1 are made to coincide is described, but the present invention is not limited to this, for example, red light beam The optical axes of the beam Lr1 and the blue light beam Lb1 are tilted by a predetermined angle, and the target track and the target mark position are not intentionally matched (that is, provided with an offset) when viewed from the first surface 100A or the second surface 100B of the optical disc 100. You may do it.

  Further, in the first and second embodiments described above, the case where the focus error signal is generated by the astigmatism method in the first surface position control optical system 30 (FIGS. 7 and 14) has been described. However, the present invention is not limited to this, and the focus error signal may be generated by another method such as a knife edge method or a Foucault method. The same applies to the generation of the focus error signal in the second surface position control optical system 50 (FIGS. 7 and 14).

  Further, the generation of the tracking error signal in the first surface position control optical system 30 is not limited to the push-pull method, and the tracking error signal is generated by another method such as a three-beam method or a differential push-pull method. May be. The same applies to the second surface position control optical system 60.

  In these cases, an optical element such as a diffraction grating may be provided in place of the cylindrical lenses 42 and 58 in accordance with each error signal generation method, and the photodetectors 43 and 59 correspond to each error signal generation method. It suffices if the detection area is divided by the divided pattern, and the signal processing unit 23 may generate each error signal by performing arithmetic processing corresponding to each error signal generation method.

  Furthermore, in the first and second embodiments described above, in the first surface position control optical system 30, the non-polarizing beam splitter 34 transmits the red light beam Lr1 and reflects the red reflected light beam Lr3. As described above, the present invention is not limited to this. For example, a polarizing beam splitter is used, and the polarization direction of the light beam is appropriately changed by a combination of a half-wave plate, a quarter-wave plate, etc. The beam Lr1 may be transmitted and the red reflected light beam Lr3 may be reflected. The same applies to the second surface position control optical system 50.

  Further, in the first and second embodiments described above, the case where the reflection / transmission film 104 is provided between the recording layer 101 and the substrate 102 in the optical disc 100 has been described. However, the present invention is not limited to this. For example, the reflective / transmissive film 104 may be provided between the recording layer 101 and the substrate 103, or in other locations such as the inside of the substrate 102 or the inside of the recording layer 101.

  Furthermore, in the first and second embodiments described above, a light beam for performing position control of the objective lenses 38 and 51 (referred to as a position control light beam) is a red light beam having a wavelength of about 660 [nm]. The case where the light beam for forming the recording mark RM (referred to as a recording light beam) is a blue light beam having a wavelength of about 405 [nm] has been described, but the present invention is not limited to this. The position control light beam and the recording light beam may have arbitrary wavelengths.

  In this case, the reflection / transmission film 104 only needs to have a property of reflecting and transmitting the position control light beam at a ratio of about half according to the wavelength and transmitting the recording light beam according to the wavelength. . The recording layer 101 may be any material that responds to the wavelength of the recording light beam.

  Incidentally, when the wavelength of the recording light beam is changed, the size of the recording mark RM changes as shown in the above formulas (1) and (2), so the distance p1 between the recording marks RM and the distance between the tracks. It is preferable to appropriately change p2 and the distance p3 between the mark recording layers.

  Furthermore, in the first and second embodiments described above, the reflection / transmission film 104 has wavelength selectivity, thereby reflecting a position control light beam having a wavelength of about 660 [nm] and a wavelength of about 405 [nm]. However, the present invention is not limited to this. For example, the reflection / transmission film 104 has polarization selectivity, the polarization direction of the position control light beam, and the recording light beam. The position control light beam may be reflected and the recording light beam may be transmitted by making the direction of polarization different.

  Further, in the above-described embodiment, the diameter of the optical disk 100 is about 120 [mm], the thickness t1 of the recording layer 101 is about 0.3 [mm], and the thicknesses t2 and t3 of the substrates 102 and 103 are about 0.0. Although the case of 6 mm is described, the present invention is not limited to this, and other values may be used. In this case, after considering the thickness of the recording layer 101 and the substrates 102 and 103, the refractive index of each material, and the like, the optical characteristics of each optical component and the like so that the blue light beams Lb1 and Lb2 are focused on the target mark position. What is necessary is just to set arrangement | positioning.

Further, in the above-described embodiment, the expander 70 and the control unit 21 as the first focus position adjusting unit, the expander 53 and the control unit 21 as the second focus position adjusting unit, and the control as the control unit. The case where the optical disk apparatus 20 as the optical disk apparatus is configured by the unit 21, the photodetectors 75 and 87 as the first and second detection means, the control section 21 as the reproduction signal generation means and the signal processing section 23 has been described. However, the present invention is not limited to this, and the first focal position adjustment means, the second focal position adjustment means, the control means, the first and second detection means, and the reproduction, which have various other circuit configurations. The optical disc apparatus may be constituted by the signal generating means.

  The present invention can be used in an optical disc apparatus that records a large amount of music content, video content, or various data on an optical disc as a recording medium.

It is a basic diagram which shows the structure of the conventional standing wave recording-type optical disk apparatus. It is a basic diagram which shows the mode of formation of a hologram. It is a basic diagram which shows the external appearance structure of the optical disk by one Embodiment of this invention. It is a basic diagram which shows the internal structure of the optical disk by 1st Embodiment. 1 is a schematic diagram illustrating a configuration of an optical disc device according to an embodiment of the present invention. It is a basic diagram which shows the external appearance structure of an optical pick-up. It is a basic diagram which shows the structure of the optical pick-up by 1st Embodiment. It is a basic diagram which shows the optical path of the red light beam by 1st Embodiment. It is a basic diagram which shows the structure of the detection area | region in a photodetector. It is a basic diagram which shows the optical path (1) of the blue light beam by 1st Embodiment. It is a basic diagram which shows the optical path (2) of the blue light beam by 1st Embodiment. It is a basic diagram with which it uses for description of the selection of the light beam by a pinhole. It is a basic diagram which shows the information recording and reproducing principle by 2nd Embodiment. It is a basic diagram which shows the structure of the optical pick-up by 2nd Embodiment. It is a basic diagram which shows the optical path (1) of the blue light beam by 2nd Embodiment. It is a basic diagram which shows the optical path (2) of the blue light beam by 2nd Embodiment. It is a basic diagram which shows the recording and reproducing principle of the information by other embodiment. It is a basic diagram which shows the structure of the mark recording layer in mirroring recording.

Explanation of symbols

  20, 120... Optical disk device, 21, 121... Control unit, 22... Drive control unit, 23... Signal processing unit, 26, 126 ... Optical pickup, 30. , 61, 181... Laser diode, 34... Unpolarized beam splitter, 37, 56... Dichroic prism, 38, 51... Objective lens, 38A, 51A, 54A, 71A. , 87... Photodetector, 50... Second surface position control optical system, 52... Galvano mirror, 53 and 70... Relay lens, 54 and 71. , 68, 82, 185... Polarizing beam splitter, 66... Quarter wave plate, 67... Movable mirror, 74, 86... Pinhole plate, 80. DESCRIPTION OF SYMBOLS 1 ... Shutter, 100 ... Optical disk, 101 ... Recording layer, 102, 103 ... Substrate, 104 ... Reflection transmission film, Lr1 ... Red light beam, Lr2 ... Red transmission light beam, Lr3 ... Red reflection Light beam, Lb0, Lb1, Lb2... Blue light beam, Lb3, Lb4... Blue reproduction light beam, Fr, Fb1, Fb2... Focus, RM, RM1, RM2.

Claims (12)

In an optical disc apparatus for reproducing information based on standing waves recorded by irradiating first and second lights from both sides of a disc-shaped volume type recording medium,
First focus position adjusting means for adjusting the position of the focal point where the first light is connected in the volume type recording medium by the first objective lens in the optical axis direction of the first light;
Second focus position adjusting means for adjusting the position of the focal point where the second light is connected in the volume type recording medium by the second objective lens in the optical axis direction of the second light;
When recording the standing wave on the volume type recording medium, the first light is focused in the volume type recording medium, and the second light is at the same position as the focal point of the first light. When the first focus position adjusting means and the second focus position adjusting means are controlled to focus, and the information is reproduced based on the standing wave of the volume type recording medium, the first light is The first focus position adjusting means and the second focus position adjusting means are arranged so that the focal point formed in the volume type recording medium and the focal point formed by the second light in the volume type recording medium are different from each other. Control means for generating first and second reproduction lights from different standing waves by controlling, respectively;
First and second detection means for detecting the first and second reproduction lights, respectively;
An optical disc apparatus comprising: reproduction signal generation means for generating a reproduction signal by integrating the detection results of the first and second detection means. The volume recording medium is
When the information is recorded as the recording mark, the information is divided into predetermined recording units, and is distributed and recorded at mutually corresponding positions on the different mark layers by the first light and the second light. And
The reproduction signal generating means includes
The optical disc apparatus according to claim 1, wherein the reproduction signal corresponding to the information before the division is generated by combining the detection results of the first and second detection means. The volume recording medium is
When the recording mark is recorded, the same information is recorded at mutually corresponding positions on the different mark layers by the first light and the second light,
The reproduction signal generating means includes
The optical disk apparatus according to claim 1, wherein the reproduction signal is generated by performing predetermined error correction processing on the detection results of the first and second detection means. The first and second detection means are:
The mixed reproduction light in which the first and second reproduction lights are mixed is converged, and the first or second reproduction is performed by a pinhole provided in accordance with a focusing position of the first or second reproduction light. The optical disk apparatus according to claim 1, wherein one of the reproduction lights is selected and detected. A predetermined third light is irradiated onto the volume type recording medium through the first objective lens with the optical axis aligned with the first light, and the return light from the positioning layer provided on the volume type recording medium. The optical disk apparatus according to claim 1, further comprising: first position control means for controlling the position of the first objective lens based on the first objective lens. The positioning layer is formed with a track representing the recording position of the recording mark,
6. The optical disc apparatus according to claim 5, wherein the first position control means controls the position of the objective lens after recognizing the track based on the return light. The third light has a wavelength different from that of the first and second lights,
6. The positioning layer according to claim 5, wherein the positioning layer transmits the first light and the second light by wavelength selectivity, reflects the third light at a predetermined ratio, and transmits the remaining light at the remaining ratio. The optical disk device described. 8. The optical disk apparatus according to claim 7, further comprising second position control means for controlling the position of the second objective lens based on the transmitted light transmitted through the positioning layer. . In the volume type recording medium, a hologram is previously formed and then the hologram is locally destroyed to form the recording mark.
The said 1st and 2nd detection means detects that the said recording mark is recorded when the said 1st and 2nd reproduction | regeneration light is not detected. Optical disk device. The volume type recording medium has a predetermined reflectivity uniformly, and the recording mark is formed by locally changing the volume type recording medium and changing the reflectivity.
2. The optical disc apparatus according to claim 1, wherein the first and second detection units detect the first and second reproduction lights that change as the reflectance changes. 3. The recording layer of the volume type recording medium has a predetermined refractive index uniformly, and the recording mark is formed by locally modifying the volume type recording medium and changing the refractive index.
2. The optical disc apparatus according to claim 1, wherein the first and second detection units detect the first and second reproduction lights that change as the refractive index changes. 3. In an information reproducing method for reproducing information by irradiating predetermined light to a volume type recording medium in which a recording mark is recorded in a disc shape and is recorded across a plurality of mark layers,
The position of the focal point where the first light is connected in the volume type recording medium is adjusted in the optical axis direction of the first light, and the position of the focal point where the second light is connected in the volume type recording medium is the second position. By adjusting in the optical axis direction of the light, the first light and the second light through the same objective lens are respectively located at positions corresponding to each other in different mark layers in the volume type recording medium. A focus control step of controlling to focus, and generating first and second reproduction lights based on the recording marks of the different mark layers;
A detection step of detecting the first and second reproduction lights, respectively.
A reproduction signal generation step of generating a reproduction signal by integrating the detection results of the detection step.

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