JP2004046915A - Optical recording medium playback device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recoding medium playback device capable of realizing larger capacity of an optical recording medium. <P>SOLUTION: The optical recording medium playback device has an optical recording medium having a plurality of recording layers and an optical head having a surface close facing the optical recording medium at a distance within the wavelength of light emitted from a light emission part and converging light emitted from the light emission part to any of the recording layers of the optical recording medium. Since the surfaces of the optical head and the optical recording medium are located in the vicinity of each other at the distance within the wavelength of light emitted from the light emission part, permeating evanescent light can be utilized for optical connection between the surfaces, and recording density of the optical recording medium can be enhanced. Since a plurality of the recording layers are provided and light is converged to the recording layers, the storage capacity of the optical recording medium can be further increased in proportion to the number of the recording layers. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording medium reproducing apparatus for reproducing information recorded on an optical recording medium.
[0002]
[Prior art]
2. Description of the Related Art An optical recording medium reproducing apparatus (optical disk system) for reading (reproducing) information recorded on an optical recording medium such as a CD (Compact Disk) and a DVD (Digital Versatile Disk) by an optical means is used. By irradiating the recording layer of the optical recording medium with light and detecting the intensity or the like of the light reflected from the recording layer, information is read from the optical recording medium (and writing is performed as necessary).
Here, in recent years, an optical recording medium reproducing device using near-field light has been receiving attention. In particular, a configuration using a solid immersion lens (SIL: Solid Immersion Lens) has a high numerical aperture NA, so that the focus (spot size) of a light beam can be narrowed, and a high recording density can be realized. In addition, the SIL system is promising because of its high affinity with the conventional optical disk optical system.
[0003]
[Problems to be solved by the invention]
However, in the SIL method, there is a limit to an increase in the storage capacity of the optical recording medium reproducing device. In the SIL method, since the recording density is determined by the wavelength of light, it is difficult to improve the recording density to a certain degree or more.
The present invention has been made to solve such a problem, and an object of the present invention is to provide an optical recording medium reproducing apparatus capable of increasing the capacity of an optical recording medium.
[0004]
[Means for Solving the Problems]
A. In order to achieve the above object, an optical recording medium reproducing apparatus according to the present invention includes: a light emitting unit that emits light; an optical recording medium having a plurality of recording layers capable of optically reading information; and a surface of the optical recording medium. An optical head having a surface that is close to and opposed to the light emitting unit at a distance within the emission wavelength thereof, and focuses light emitted from the light emitting unit to one of the recording layers of the optical recording medium; An optical member for converging return light returned from the optical recording medium in response to the light converged by the head, and a light receiving unit for receiving light converged by the optical member are provided. .
The optical recording medium reproducing device has an optical recording medium having a plurality of recording layers, a surface facing the optical recording medium at a distance within the emission wavelength of the light emitting unit, and is emitted from the light emitting unit. An optical head for focusing light on any of the recording layers of the optical recording medium. Since the surface of the optical head and the surface of the optical recording medium are close to each other at a distance within the emission wavelength, it is possible to use the seepage of evanescent light for optical connection between the surfaces. In this case, since the refractive index of the air layer or the like between the surfaces does not cause an optical problem, it is easy to increase the numerical aperture NA. As a result, the resolution of reading and writing, that is, the recording density of the optical recording medium can be improved.
Further, since the number of recording layers is plural and light is focused on the recording layers, it is possible to increase the storage capacity of the optical recording medium in accordance with the number of recording layers.
[0005]
(1) The return light may include any of light transmitted, reflected, or generated in any of the plurality of recording layers of the optical recording medium.
Any of transmitted light, reflected light, and generated light from the recording layer can be used for reading information from the recording layer.
[0006]
(2) The return light may be an incoherent light.
When the return light is incoherent, it is possible to prevent the return light from being multiple-reflected between a plurality of recording layers and causing noise. In this case, the optical recording medium can be designed without much consideration of light interference between recording layers, and for example, the thickness of the recording layer can be reduced.
In order to make the return light incoherent light, either the light emitted from the light emitting unit is made incoherent light, or the recording layer generates incoherent light in response to the incident light. Can be used.
[0007]
(3) The wavelength of the return light may be different from the wavelength of the light emitted from the light emitting unit.
Since the light emitted from the light emitting unit and the return light have different wavelengths, these lights can be more reliably separated.
For example, by generating fluorescence from the pits of the recording layer, it is possible to make the wavelength different between the light emitted from the light emitting unit and the return light.
[0008]
(4) The optical head may be a floating optical head that floats from the optical recording medium by a flow of air generated by relative movement with the optical recording medium.
The use of the floating optical head enables stable reading even when the optical head scans the optical recording medium.
Note that “relative” means that one or both of the optical recording medium and the optical head may be moved.
[0009]
(5) The optical recording medium reproducing apparatus may further include a recording layer identification unit that identifies a recording layer on which light emitted from the optical head is focused.
Using the recording layer identification means, it is possible to specify the recording layer on which reading and writing are being performed.
Here, the recording layer identification means may identify each recording layer by referring to a table representing a relationship between the depth of the recording layer and the intensity of the return light.
Since there is a correspondence between the depth of the recording layer and the intensity of the return light, by storing this correspondence in a table and referring to the table, it is possible to identify the recording layer on which light converges.
[0010]
(6) The optical recording medium reproducing device may further include a convergence position adjusting means for adjusting a convergence position of the convergent light from the optical head in a thickness direction of the optical recording medium. It becomes easy to converge light to an appropriate depth (position) for each recording layer. The convergence position adjusting means can be configured using, for example, any one of an afocal optical system, a variable refractive index element, and a wedge prism.
[0011]
(7) The optical recording medium reproducing device may further include a pinhole between the optical member and the light receiving unit.
It is possible to exclude stray light from light incident on the light receiving portion, particularly return light from a portion other than the recording layer where the light is focused.
Here, the light emitting section, the pinhole, and the light receiving section may be integrally formed on the same substrate.
It is possible to reduce the alignment deviation between the light emitting unit, the pinhole, and the light receiving unit, the fixing labor, and the positional deviation due to the temporal change.
For this formation, for example, semiconductor technology can be used. In addition, by limiting the size of the light receiving surface of the light receiving unit, it is possible to substantially integrally form the light receiving unit and the pinhole.
[0012]
(8) The optical recording medium reproducing device may further include a detection unit that detects at least one of focus, tracking, and a tilt state with respect to the optical recording medium.
The focus, tracking, and tilt states are information indicating a shift of the focus of the incident light on the recording layer in the optical axis direction, a shift of the position of the incident light on the track of the recording layer, and a tilt of the incident light on the optical recording medium. These pieces of information can be output from the detection means as, for example, a focus error signal, a tracking error signal, and a tilt signal.
By providing such a detecting means, it becomes possible to perform focus and tracking on each recording layer, or to adjust the tilt of the optical recording medium.
[0013]
B. An optical recording medium reproducing device according to the present invention includes: a light emitting unit that emits light; a stage that holds an optical recording medium having a plurality of recording layers that can optically read information; An optical head having a surface which is close to and opposed to a light emitting wavelength of the optical recording medium, and which converges light emitted from the light emitting element to any of the recording layers of the optical recording medium; and An optical member for converging the return light returned from the optical recording medium in response to the received light, and a light receiving unit for receiving the light converged by the optical member.
The optical recording medium is appropriately set on the stage. That is, the optical recording medium reproducing apparatus does not require the optical recording medium as an essential element, and allows the optical recording medium to be attached and detached.
The other components are not essentially different from the optical recording medium reproducing apparatus shown in A.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(1st Embodiment)
In the present embodiment, an optical recording medium reproducing apparatus 100 using a floating optical head 80 for reading information from the optical recording medium 10 is shown.
A. Details of configuration of optical recording medium 10
First, the configuration of the optical recording medium 10 will be described.
The optical recording medium 10 may be any type of read only (read only), write only (write only), and rewritable (rewritable). That is, the optical recording medium reproducing device 100 may perform any of reading, writing, and rewriting from the optical recording medium 10 in some cases.
The optical recording medium 10 can have a plurality of variations depending on how tracking is performed. 1A and 1B are enlarged sectional views of optical recording media 10A and 10B according to a configuration example of the optical recording medium 10, respectively.
[0015]
The optical recording medium 10A has a plurality of recording layers 11A and a lowermost groove layer 12A. Information is recorded on the recording layer 11A of the optical recording medium 10A in an optically readable form. Reflection type recording pits (or recording marks) are recorded on the recording layer 11A. The recording pits may be of a transmission type depending on the case. When light enters the recording pits, reflection or transmission of light occurs, and information can be read from the intensity of the reflected light or transmitted light.
[0016]
It is also possible to generate light (for example, fluorescence) different from the wavelength of the incident light from the recording pit, and read information using the generated light. This generated light may be either coherent light having coherence or incoherent light having no coherence.
Since ordinary fluorescent light is incoherent light, it is possible to generate incoherent light in accordance with information recorded from the recording layer 11 by scattering a fluorescent substance on the recording layer 11 and using this as recording pits.
[0017]
The groove layer 12A is a layer in which a guide groove (groove) serving as a reference for performing tracking when reading information recorded on the recording layer 11 is formed. Tracking can be performed using any of reflection, transmission, and generation of light from the groove.
[0018]
On the other hand, the optical recording medium 10B has a plurality of recording layers 11B, but does not have a groove layer unlike the optical recording medium 10A. Instead, a guide groove (groove) serving as a reference for performing tracking is formed in each of the recording layers 11B.
As the optical recording medium 10, any of the optical recording media 10A and 10B may be used.
[0019]
B. Details of the configuration of the flying optical head 80
Next, the floating optical head 80 will be described.
FIG. 2 is a schematic diagram illustrating a configuration example of the flying optical head 80.
The floating optical head 80 performs recording and / or reproduction of a signal on the optical recording medium 10 by using near-field optics. As shown in the drawing, a slider member 81, a second group lens 82, a suspension 83 and a focus adjustment mechanism 84. Note that the aberration correction element 126 is provided in the optical path of the light incident on the flying optical head 80.
The floating optical head 80 is a light collecting optical system that collects light on the optical recording medium 10 and is connected to the optical system of the optical recording medium reproducing device 100 through parallel light.
[0020]
The slider member 81 is supported by the suspension 83 so as to face the optical recording medium 10 similarly to a head slider used in a hard disk device or the like. Accordingly, when writing or reading a signal to or from the optical recording medium 10, the optical recording medium 10 floats on the optical recording medium 10 by about 100 nm or less due to an air flow generated between the optical recording medium 10 due to rotation of the optical recording medium 10 and the like. It is possible to travel while levitating by the amount (distance d).
The slider member 81 is provided with a through hole 81a penetrating at a predetermined position in the thickness direction. The second group lens 82 is disposed in the through hole 81a.
[0021]
The second group lens 82 includes an objective lens 85 and a solid immersion lens (SIL) 86, and can realize one or more numerical apertures NA.
The objective lens 85 has a first surface 85a whose one surface is a spherical or aspherical convex surface and a second surface 85b whose other surface is a spherical surface or an aspheric surface, and is a lens on the light source side.
The solid immersion lens 86 has a third surface 86a whose surface facing the objective lens 85 is a spherical or aspherical convex surface, and a fourth surface 86b whose other surface is substantially flat, The lens on the side facing the optical recording medium 10.
[0022]
The solid immersion lens 86 uses the oozing of evanescent light by the near-field optics between the fourth surface 86b and the optical recording medium 10 by bringing the fourth surface 86b and the optical recording medium 10 close to each other. By setting the distance d between the fourth surface 86b of the solid immersion lens 86 and the optical disk to about 100 nm or less, a numerical aperture NA of 1 or more is realized, and reading of the optical recording medium 10 with high resolution or the like is possible. And
[0023]
When the fourth surface 86b and the optical recording medium 10 are brought close to each other, the inflow and outflow of light between the fourth surface 86b and the optical recording medium 10 are performed by seepage of evanescent light. . As a result, the refractive index of the air layer between the fourth surface 86b and the optical recording medium 10 does not affect the light passing through the air layer, and the medium that transmits the light is substantially solid immersion. Only the lens 86 is provided.
Since the numerical aperture NA is proportional to the refractive index n of the medium, and the refractive index n of the solid immersion lens 86 is larger than the refractive index (n0 = 1) of the air layer, the numerical aperture NA can be increased. The numerical aperture NA can be appropriately set to 1 or more and 1 or less depending on the case.
[0024]
The suspension 83 can maintain an appropriate floating amount of the slider member 81 by providing a suspension spring having elasticity between itself and the slider member 81.
As the focus adjustment mechanism 84, for example, a variable refractive index element whose refractive index changes by application of a voltage or the like can be used. The variable refractive index element can be configured using a liquid crystal element or the like. By changing the refractive index, the optical path length changes and the position of the focal point can be adjusted. As a result, it is possible to appropriately select the recording layer 11 on which light is focused.
Further, by controlling the position of the focal point based on the focus error signal, it becomes possible to focus on the optimal position for each of the recording layers 11.
[0025]
The incident light from the objective lens 85 side is optically recorded via the objective lens 85, the focus adjustment mechanism 84, the solid immersion lens 86, and the air layer (distance d) between the floating optical head 80 and the optical recording medium 10. The light enters the recording layer 11 of the medium 10. The light reflected by the recording layer 11 exits the objective lens 85 as return light through the reverse path.
As will be described later, aberration (mainly spherical aberration) caused by movement of the recording layer 11 is appropriately corrected by the aberration correction element 126.
[0026]
By adjusting the focal position and correcting the aberration as described above, it is possible to appropriately condense light on a desired recording layer 11, that is, read and write information.
In the present embodiment, it is possible to realize near-field optics to achieve a numerical aperture of one or more, and to read and write high-resolution optical recording medium 10, that is, to increase the capacity of optical recording medium 10. Become.
[0027]
The focus adjustment mechanism 84 can also be realized by means other than the variable refractive index element.
FIG. 3 is a schematic diagram illustrating a configuration of a floating optical head 80A in which a focus adjustment mechanism is realized by a pair of wedge prisms 87a and 87b.
The wedge-shaped portions of the wedge (wedge-shaped) prisms 87a and 87b are vertically overlapped to constitute a plate-like member 87 as a whole. By adjusting the relative positions of the wedge prisms 87a and 87b, the thickness of the plate member 87 can be changed. This change in thickness causes a change in the optical path length of light passing through the plate-like member 87. As a result, the focal position can be adjusted by moving one or both of the wedge prisms 87a and 87b.
[0028]
The focus adjusting mechanism 84 can be provided separately from the floating optical head 80.
FIG. 4 is a schematic diagram illustrating an example in which the focal position is adjusted using an afocal optical system 93 including a pair of lenses 91 and 92. The floating optical head 80B is not provided with a focus adjustment mechanism. Instead, the focal position on the optical recording medium 10 can be adjusted by incorporating the afocal optical system 93 into the optical system of the optical recording medium reproducing apparatus 100. By varying the distance between the pair of lenses 91 and 92, the angle of the incident light incident on the objective lens 85 can be delicately changed, and the focal position can be adjusted.
[0029]
It is also possible to add another optical element such as a mirror to the floating optical head 80. FIG. 5 is a configuration example of a floating optical head 80C having a mirror 88. A mirror 88 is provided above the objective lens 85, and the objective lens 85 inputs and outputs light to and from the optical system of the optical recording medium reproducing device 500 via reflection by the mirror 88.
The suspension 83A is connected to one side of the slider member 81 by a suspension spring.
[0030]
FIG. 6 is a configuration example of a floating optical head 80D having a condenser lens 89 and an optical fiber 95. The light emitted from the objective lens 85 is sent to one end of an optical fiber 95 via a mirror 88 and a condenser lens 89. The light emitted from one end of the optical fiber 95 enters the objective lens 85 via the condenser lens 89 and the mirror 88. That is, the floating optical head 80D inputs and outputs light to and from the optical system of the optical recording medium reproducing apparatus 100 via the optical fiber 95.
[0031]
C. Details of aberration correction element 126
The aberration correction element 126 is an optical element for correcting aberration (mainly spherical aberration) caused by movement of each recording layer 11 to improve the efficiency of converging light on the recording layer 11 of the optical recording medium 10, and for example, It can be configured using a liquid crystal element.
In the aberration correction liquid crystal element 126, the correction amount of the aberration can be changed according to the applied voltage. Therefore, it is possible to appropriately correct the aberration in accordance with the position of the focal point of the flying optical head 80.
[0032]
Spherical aberration refers to a phenomenon in which a light ray emitted from one point on the optical axis shifts back and forth after passing through the lens without converging on one point on the axis. The magnitude of the spherical aberration is represented by the amount of deviation.
This spherical aberration changes when the recording layer 11 for focusing is moved. Even if the spherical aberration is corrected for the central recording layer 11, if the focal position is moved to the shallow recording layer 11 or the deep recording layer 11, the spherical aberration increases.
[0033]
FIG. 7 is a graph showing the calculation results of the spherical aberration. The constituent material of the optical recording medium 10 is SiO ₂ The calculation is performed on the assumption that the central layer (the central recording layer 11) is about 500 μm below the center (the top of the curved surface) of the upper surface 86a of the solid immersion lens 86.
7A is a case where the focus position adjusting means is incorporated in the floating optical head 80, and FIG. 7B is a case where FIG. When installed outside). Here, the solid line and the broken line of the graph are the calculation results when the numerical aperture NA is 0.88 and 1.047, respectively.
For example, when the numerical aperture NA in FIG. 7A is 1.047, a fluctuation of spherical aberration of about 0.2λ (rms value) occurs with a movement amount of 50 μm. The spherical aberration of 0.2λ is within a range that can be corrected using a commercially available spherical aberration correcting liquid crystal element.
[0034]
The distance of 50 μm corresponds to 10 layers when the interval (layer interval) of the recording layers 11 is 5 μm. That is, by using a gradation type spherical aberration correction liquid crystal element manufactured by Asahi Glass Co., Ltd., reading from the optical recording medium 10 having about 10 recording layers 11 becomes possible. As a result, it is found that the storage capacity of the optical recording medium 10 can be increased to ten times or more as compared with the case of a single layer (when the numerical aperture NA is 1.047).
The setting of the layer spacing of 5 μm is smaller than that of a conventional DVD disk having a two-layer structure, but is a value sufficient to avoid Rayleigh scattering. This is effective when fluorescence detection is selected as a reproduction method.
[0035]
Since general fluorescent light is incoherent, it is possible to read information using the generation of incoherent light by dispersing fluorescent substances in the recording layer 11 so as to correspond to the pits.
Further, by using a light source that emits incoherent light (for example, a light source that does not emit laser light) as a light source (light source 121 described later) that emits incident light on the recording layer 11, the light from the recording layer 11 due to the incoherent light can be used. Reading of information can be realized. As described above, by reading information from the optical recording medium 10 using the incoherent light, light interference between the recording layers 11 is suppressed, and the optical recording medium 10 with a narrower layer interval can be read. It becomes.
[0036]
D. Overall configuration of optical recording medium reproducing device 100
FIG. 8 is a schematic diagram illustrating the overall configuration of the optical recording medium reproducing device 100. As shown in the figure, the optical recording medium reproducing apparatus 100 includes an optical recording medium 10, a light source (Light Source) 121, a collimator lens (Collimator Lens) 122, an anamorphic prism (Anamorphic Prism) 123 and 124, a non-polarizing beam splitter. (NPBS: Non-Polarization Beam Splitter) 125, Aberration Correcting Element (Spherical Aberration Compensator) 126, Polarization Beam Splitter (PBS: Polarization Beam Splitter) 127, Quarter Wave Plate (QWP: Quarter-Water Wave) Optical system 129, dichroic combiner r) 131, floating-type optical head 80 has a tilt servo unit 160.
[0037]
Also, a light source (Light Source) 141, a collimator lens (Collimator Lens) 142, an anamorphic prism (Anamorphic Prism) 143, 1644, a condenser lens (Condenser Lens) 151 to 153, a light receiving unit 30, a monitor PD (Front monitor PhotoD) ) 171 and 172.
[0038]
The optical recording medium reproducing apparatus 100 has a scanning unit (not shown) for scanning the optical recording medium 10 with a light beam emitted from the semiconductor laser 121 in order to read information from the entire surface of the optical recording medium 10. . For example, by rotating the optical recording medium 10 and moving the floating optical head 80 in the radial direction with respect to the center of rotation of the optical recording medium 10, optical recording is performed by light emitted from the floating optical head 80. It is possible to scan almost the entire surface of the medium 10.
[0039]
The light source 121 is a light source used for generating an RF signal and a focus error signal, and has a wavelength λ of, for example, 400 nm. Reading from the optical recording medium 10 can be performed with higher resolution by shortening the wavelength.
The collimator lens 122 converts the light emitted from the light source 121 into substantially parallel light.
The anamorphic prisms 123 and 124 form an anamorphic optical system, appropriately shape the light emitted from the collimator lens 122, and send the light to the non-polarizing beam splitter 125.
The non-polarizing beam splitter 125 reflects a part of the incident light and transmits the other, and the ratio of the amount of reflection to the amount of transmission is set to, for example, 1: 9.
The aberration correction element 126 is an optical element that corrects the aberration caused by the movement of the recording layer 11 to improve the focusing performance of light to the optical recording medium 10 as described above. Can be configured.
[0040]
The polarization beam splitter 127 is an optical element that transmits light having a predetermined polarization component and reflects light having another polarization component.
The quarter-wave plate 128 is an optical element that imparts a quarter-wave phase difference to orthogonally polarized components.
The afocal optical system 129 is composed of a pair of lenses as described above, and by changing the distance between the lenses, the condensing position at which the light emitted from the light source 121 is condensed on the optical recording medium 10 is adjusted. In addition, it is possible to select the recording layer 11 on which reading or the like is performed.
The dichroic combiner 131 is an optical element that combines light of a plurality of wavelengths, and in this case, combines light emitted from the light sources 121 and 141.
[0041]
The light source 141 is a light source used for generating a tracking error signal.
The collimator lens 142 converts light emitted from the light source 141 into substantially parallel light.
The anamorphic prisms 143 and 144 constitute an anamorphic optical system, and convert the light emitted from the collimator lens 142 into a shape corresponding to the dichroic combiner 131.
The condenser lenses 151 to 153 focus light on the light receiving unit 30 and the monitor PDs 171 and 172.
The monitor PDs 171 and 172 monitor the outputs of the light sources 121 and 141, respectively.
[0042]
The light source 141 and the anamorphic prisms 143 and 144 are useful when the optical recording medium 10 has a tracking groove layer 12A. On the other hand, when each recording layer 11B has a groove for tracking like the optical recording medium 10B, the light from the light source 121 is used for information reading and tracking, excluding the light source 141 and the anamorphic prisms 143 and 144. It can be used for both applications.
[0043]
E. FIG. Configuration of light receiving unit 30
The light receiving unit 30 includes a hologram element 31, a pinhole 32, and light receiving elements 33 to 35.
The hologram element 31 is an optical element that diffracts light incident from the polarization beam splitter 122 by a hologram and causes the light to enter each of the light receiving elements 33 to 35. Tracking and focusing are performed by forming an appropriate diffraction pattern in advance. Is inserted for the purpose of generating a beam pattern suitable for both servo signals.
[0044]
The pinhole 32 has a hole formed corresponding to the focal point of the light incident on the light receiving element 33 from the hologram element 31, passes light passing near the focal point of the incident light, and receives light other than that. To block incident light.
The convergent light on the optical recording medium 10 and the convergent light on the light receiving element 33 have focal points corresponding to each other. For this reason, by passing the light converged on the light receiving element 33 through the pinhole 32, stray light from the recording layer 11 other than the focal point on the optical recording medium 10, that is, the recording layer 11 which is not being read out, (Reflected light from the layer) can be excluded, and the S / N ratio of the signal can be improved.
[0045]
It is considered effective to adopt, for example, a value about the diameter of an Airy disk (1.22λ / NA) as the diameter φ of the hole. The Airy disk of the focused light on the light receiving element 33 side corresponds to the Airy disk of the focused light on the recording layer 11 of the optical recording medium 10. Therefore, it is considered that stray light can be removed from the light incident on the light receiving element 33 by passing only the light of the focused light on the light receiving element 33 side within the Airy disk. If the diameter φ of the hole is too large than the diameter of the Airy disk, stray light increases in the light incident on the light receiving element 33. On the other hand, if the diameter φ of the hole is too small than the diameter of the Airy disk, the intensity of light incident on the light receiving element 33 decreases.
Assuming that the numerical aperture NA (numerical aperture of the condenser lens 151) of light incident on the light receiving element 33 (return light from the optical recording medium 10) is about 0.1 and the wavelength λ of the light source 121 is 400 nm, the diameter φ of the hole is Is about 5 μm.
[0046]
The light receiving element 33 is an element for receiving the return light from the optical recording medium 10 and generating information recorded on the optical recording medium 10 as an RF signal.
The light receiving elements 34 and 35 are elements for receiving return light from the optical recording medium 10 and generating a tracking error signal for performing tracking on the optical recording medium 10.
The light receiving element 33 and the light receiving elements 34 and 35 are light receiving elements corresponding to the light sources 121 and 141, respectively, and preferably have a sensitive wavelength range corresponding to the emission wavelength of each of the light sources 121 and 141.
[0047]
Here, the means for detecting which of the plurality of recording layers 11 the light is converging will be described.
FIG. 9 shows the depth of focus, the output RF signal (FIG. 9A), and the focus error signal (FE signal) when reproducing the optical recording medium 10 using the optical recording medium reproducing apparatus 100 (FIG. 14 is a graph showing the relationship with B)). By adjusting the depth of focus to each layer, the RF signal is maximized. The FE signal increases or decreases by shifting the depth of focus from the center of each layer.
[0048]
This is because the loss of incident light that has entered the optical recording medium 10 increases as it goes to the deep recording layer 11. Then, it is necessary to change the amount of incident light).
As described above, since the light amount of the return light corresponds to the depth of the recording layer 11, the light amount value of the return light from the vicinity of the center of each recording layer 11 (the value near the center value) is a reference for identifying the recording layer 11. (Reference value). Therefore, a table representing the correspondence between each recording layer 11 and a reference value (the amount of return light from near the center of the layer) is stored in a storage unit (not shown) of the optical recording medium reproducing apparatus 100, and is referred to. Thus, the recording layer 11 on which the beam has been converged can be specified based on the amount of return light.
[0049]
The knife edge method can be used to generate the focus error signal. The knife edge method is a method of disposing a knife edge that asymmetrically shields a part of return light reflected by the optical recording medium 10. By taking the difference between the outputs from the light receiving elements 34 and 35, a focus error signal can be obtained.
Although the absolute intensity of the focus error signal differs in each recording layer 11 as described above, the focus error signal can be generated by using the DC level corresponding to each recording layer 11 as a reference.
[0050]
The output of the tracking error signal can be performed by performing arithmetic processing on outputs from the light receiving elements 34 and 35 based on the push-pull method. A tracking error signal is output using reflected light from the groove of the recording layer 11, and tracking adjustment (tracking servo) to the optical recording medium 10 can be performed based on the tracking error signal.
[0051]
It is also conceivable to use a DPD (Differential Phase Detection) method to obtain a tracking error signal. The DPD method requires that the pit depth of the groove be a certain depth of λ / 4, which means that it is difficult to increase the number of recording layers 11B. For this reason, the present embodiment employs the push-pull method. However, this is based only on the ease of manufacturing the recording layer 11, and does not absolutely exclude the application of the DPD method.
In addition, when burying of pits is used for tilt detection described later, it is conceivable to use a sample servo method for generating a tracking error signal from the viewpoint of the manufacturing efficiency of the optical recording medium 10.
[0052]
F. Tilt servo unit 160
The tilt servo (skew servo) unit 160 performs optical recording based on a detection result of tilt (tilt (tilt, skew) of the optical recording medium 10 with respect to the optical axis of light incident on the optical recording medium 10 from the floating optical head 80). This is an adjustment mechanism for adjusting the incident light so as to be perpendicularly incident on the surface of the medium 10.
[0053]
Since the optical recording medium 10 has a multilayer structure, if the optical recording medium 10 is inclined with respect to the optical axis A of the incident light, the information reading position shifts for each recording layer 11. This is illustrated in FIG. Here, FIG. 10A shows a case where the surface of the optical recording medium 10 is perpendicular to the optical axis A of the incident light (no inclination), and FIG. 3 shows a case where the surface of the optical recording medium 10 is inclined by the angle θ.
[0054]
In FIG. 10A, the pits at the same position (a planar position on the surface of the optical recording medium 10B) of each recording layer 11B can be read by the incident light on the optical axis A, whereas FIG. In B), it can be seen that reading from the pit at the same position on each recording layer 11B cannot be performed with the incident light of the same optical axis A. That is, a positional shift (an offset amount at a position different for each recording layer 11B) occurs for each recording layer 11B according to the inclination θ of the optical recording medium 10.
[0055]
The tilt servo unit 160 is used to correct the tilt of the optical recording medium 10, and the tilt of the floating optical head 80 with respect to the optical recording medium 10 is adjusted (including the tilt of the optical recording medium 10 itself). I do.
In order to detect the tilt (tilt, skew) of the optical recording medium 10, for example, a method of embedding a pit serving as a tilt reference at the same position on each recording layer 11 is considered (embedded pits proposed by ASMO). method). The optical axis of the light incident on the optical recording medium 10B is adjusted so that the reference pits are aligned on the same optical axis (see FIG. 10A).
In addition to the tilt detection, a method using a change in the position of the reflected light according to the inclination of the optical recording medium 10 (a method of differentially detecting the movement of the position of the reflected light by the tilt sensor), a DVD -A method used in a RAM, a method using coma, and the like are also conceivable.
[0056]
(Operation of Optical Recording Medium Reproducing Apparatus 100)
Light emitted from the light source 121 is converted into substantially parallel light by a collimator lens 122, shaped by anamorphic prisms 123 and 124, and incident on a non-polarizing beam splitter 125. Part of the light that has entered the non-polarizing beam splitter 125 enters the monitor PD 171 via the condenser lens 152, and the output is monitored.
[0057]
Most of the light that has entered the non-polarizing beam splitter 125 enters the aberration correction element 126, and thereafter enters the quarter-wave plate 128 via the polarizing beam splitter 127. The incident linearly polarized light is converted into circularly polarized light by the quarter-wave plate 128, and enters the optical recording medium 10 via the afocal optical system 129, the dichroic combiner 131, and the floating optical head 80.
Light incident on the optical recording medium 10 is reflected by the recording layer 11 and becomes return light. This return light passes through the floating optical head 80, the dichroic combiner 131, and the afocal optical system 129, is converted to linearly polarized light orthogonal to the outward path by the quarter wavelength plate 128, and is reflected by the polarization beam splitter 127. The light is converged on the light receiving unit 30 by the condenser lens 151, and an RF signal and a focus error signal are generated.
[0058]
The light emitted from the light source 141 is converted into substantially parallel light by the collimator lens 142, shaped by the anamorphic prisms 143 and 144, and incident on the dichroic combiner 131. Part of the light incident on the dichroic combiner 131 is incident on the monitor PD 172 via the condenser lens 153, and the output of the light source 141 is monitored.
[0059]
Most of the light that has entered the dichroic combiner 131 enters the optical recording medium 10 via the floating optical head 80. The light incident on the optical recording medium 10 is reflected by the surface on which the tracking pattern is formed (the groove layer 11A in FIG. 1A and the recording layer 11B in FIG. 1B), and becomes return light. The return light passes through the floating optical head 80, the dichroic combiner 131, and the afocal optical system 129, is converted into linearly polarized light by the quarter-wave plate 128, is reflected by the polarization beam splitter 127, and is received by the condenser lens 151. 30 and a tracking error signal is generated.
[0060]
The optical recording medium reproducing device 100 according to the present embodiment has the following features.
(1) An optical head having one or more numerical apertures NA can be realized for the optical recording medium 10 having a plurality of recording layers. That is, by using an optical head close to the optical recording medium 10, the numerical aperture NA can be increased, and the optical recording medium 10 can be read (and possibly written) with high resolution.
Since the optical recording medium 10 has a plurality of (for example, about ten) recording layers 11, the storage capacity can be easily increased.
[0061]
(2) Since the optical head can be constituted by a floating optical system (floating optical head 80), the stability when reading and writing on an optical recording medium having a plurality of recording layers is improved.
[0062]
(3) Light (eg, fluorescence) having a wavelength different from the wavelength of the incident light is generated from the recording pit by the incidence of the light, so that the efficiency of information reading can be improved.
Here, by using the light generated from the recording pits as incoherent light, light interference between the recording layers 11 can be reduced. As a result, when designing the recording layer 11, it becomes possible to ignore the interference of light and to consider only scattering such as Rayleigh scattering.
[0063]
(4) Recording of information is performed on the recording layer 11 in the optical recording medium 10, not on the surface of the optical recording medium 10. For this reason, even if dust or the like adheres to the optical recording medium 10, the effect on reading is relatively small.
(5) Focusing of light is also performed on the recording layer 11 in the optical recording medium 10, not on the surface of the optical recording medium 10. For this reason, even when a reblicant (lubricant) is interposed between the lower surface of the flying optical head 80 and the optical recording medium 10, the reblicant is hardly affected by heat or the like due to the converged light.
[0064]
(6) The convergence of light to the recording layer 11 of the optical recording medium 10 can be improved by shaping light by the anamorphic prism and correcting spherical aberration by the aberration correction element. This contributes to reading of the optical recording medium 10 with high resolution, reduction of stray light, and the like.
(7) The focal position with respect to the optical recording medium 10 is adjusted by using the afocal optical system 129. Therefore, there is no need to provide a focus position adjusting means in the flying optical head 80, and the configuration can be simplified.
(8) Since the light receiving unit 30 has the pinhole 32, it is possible to improve the S / N ratio of the RF signal by excluding stray light from the recording layers 11 other than the recording layer 11 on which reading is desired.
[0065]
(Second embodiment)
FIG. 11 is a schematic diagram showing an optical recording medium reproducing device 200 according to the second embodiment of the present invention. As shown in the figure, the optical recording medium reproducing apparatus 200 includes an optical recording medium 10B, a light receiving / emitting element 221 with a pinhole, a polarizing beam splitter 222, a collimator / focus lens 223, a mirror 224, and an aberration correction element (Spherical aberration compensator) 225. , A floating optical head 80, a light receiving unit 30A (hologram element 31A, light receiving elements (PD: Photo Diodes) 33A to 35A), a monitor PD (Front Monitor Photo Diode) 226, and a tilt servo unit 227.
[0066]
The light emitted from the light emitting / receiving element with pinhole 221 is incident on the optical recording medium 10B via the polarization beam splitter 222, the collimator / focus lens 223, the mirror 224, the aberration correction element 225, and the floating optical head 80.
The return light reflected from the optical recording medium 10B passes through the floating optical head 80, the aberration correction element 225, the mirror 224, the collimator / focus lens 223, the polarization beam splitter 222, and the light receiving / emitting element 221 with a pinhole and the light receiving element 221. The light enters the unit 30A.
[0067]
In this embodiment, a pinhole-equipped light emitting / receiving element 221 in which a semiconductor laser, a pinhole, and a light receiving element are integrated is used. As described in the first embodiment, the diameter of the pinhole is as small as 5 μm, for example. For this reason, it is not always easy to accurately form a pinhole having a fine hole, assemble it with a light receiving element, and fix it. Further, there is a possibility that the positional accuracy is deteriorated due to aging. In particular, in a dynamic optical system in which light scans on the optical recording medium 10, it is considered that the possibility of the aging problem increases.
In the present embodiment, the use of the light receiving / emitting element 221 with a pinhole facilitates formation of a pinhole, assembly with a light receiving element, etc., and aging.
[0068]
As in the first embodiment, the optical recording medium reproducing apparatus 200 includes a light scanning unit (not shown) for reading information from the entire surface of the optical recording medium 10 and a recording layer 11 of the optical recording medium 10. There is a focus adjusting means (not shown) for focusing the light emitted from the floating optical head 80.
[0069]
In the optical recording medium 10B, as described above in the first embodiment, a groove serving as a reference for tracking is formed in each recording layer 11B.
The light emitting / receiving element with pinhole 221 includes a semiconductor laser (for example, a wavelength of 658 nm) as a light source for reading information from the optical recording medium 10B, a light receiving element for receiving return light from the optical recording medium 10B, and a light receiving element. A pinhole for removing stray light from incident light is integrally formed. The details of the configuration of the pinhole-equipped light emitting / receiving element 221 will be described later.
[0070]
The polarization beam splitter 222 is an optical element that transmits light of a predetermined polarization component and reflects light of another polarization component (for example, transmits P-polarized light and reflects S-polarized light).
The collimator / focus lens 223 converts the light emitted from the light emitting / receiving element 221 with a pinhole into parallel light, and converges the return light reflected from the optical recording medium 10B to form a light receiving / emitting element 221 with a pinhole and a light receiving element. It is an optical element that is incident on 33A to 35A.
The floating optical head 80 is an optical element that converges light emitted from the pinhole-equipped light emitting / receiving element 221 on the recording layer 11B of the optical recording medium 10B, as described in the first embodiment.
The mirror 224 is a reflection element for changing (deflecting) the direction of light.
[0071]
The light receiving unit 30A has a configuration that is basically similar to the light receiving unit 30 described in the first embodiment. However, the light receiving unit 30A is not provided with a pinhole. This is because, in the present embodiment, since the light receiving unit 30A does not generate the RF signal, there is no need to reduce stray light.
[0072]
FIG. 12 is a perspective view illustrating a confocal laser coupler (CLC) 50 which is a specific configuration example of the light emitting / receiving element 221 with a pinhole.
The confocal laser coupler 50 has a light emitting unit 52 and a light receiving unit 53 formed on a semiconductor substrate 51. The light emitting section 52 is composed of a semiconductor laser LD (for example, light emission wavelength of 658 nm) having a cavity length direction in a direction along the surface of the semiconductor substrate 51, and a reflecting mirror M provided on an emission end face thereof. The light receiving unit 53 includes a light receiving element (photodiode) PD disposed on the opposite side of the reflecting mirror M from the portion where the semiconductor laser LD is formed.
Here, θ1 is the inclination of the reflecting mirror, GaAs of [0,1, −1] plane is used for the semiconductor substrate 51, and {1,1,1} B plane is set to, for example, 54.7 ° as the reflecting surface. it can.
[0073]
The light receiving unit 53 is arranged at a position (confocal) where the return light emitted from the light emitting unit 52 and reflected by the optical recording medium 10B is converged by the collimator / focus lens 223. Since the light emitting unit 52 and the light receiving unit 53 are close to each other, the outgoing light emitted from the light emitting unit 52 enters the light receiving unit 53 when returning along a reverse path. The distance between the light emitting unit 52 and the light receiving unit 53 can be, for example, within the diameter of the Airy disk (1.22λ / NA), which is the diffraction limit.
Further, by reducing the size of the light receiving surface of the light receiving section 53, it becomes possible to remove stray light substantially in the same manner as when a pinhole is separately added. That is, the light receiving section 53 is substantially integrated with the pinhole by setting the light receiving surface to the size of the pinhole shown in the first embodiment (for example, about the diameter of the Airy disk or less). I have.
[0074]
As described above, in the confocal laser coupler 50, a light receiving section 53 (a light receiving section 53 having a size of an Airy disk) is provided near the light emitting section 52 (light emitting point) and spatially band-limited by a size of an Airy disk. ) Is formed.
Accordingly, the light reflected from the focused recording layer 11B returns to the light receiving section 53 without fail. Therefore, by focusing the light emitted from the confocal laser coupler 50 on the desired recording layer 11B, the reflected light from the recording layer 11B can be incident on the light receiving section 53, and the position of the light receiving section 53 can be adjusted. No adjustment (alignment) is required. As a result, a signal from the focused recording layer 11B can be reliably captured. This also leads to the fact that the field of view of the flying optical head 80 is less susceptible to movement or the like.
[0075]
As described above, even in a dynamic operation environment in which the optical recording medium 10 is scanned using the optical recording medium reproducing apparatus 200, the focus servo is applied so as to maintain the focus on the desired recording layer 11B. The confocal system can be maintained (light incident on the light receiving unit 53 can be secured).
Further, the light receiving unit 53 is formed by forming a light receiving element having a pinhole size by a semiconductor process or the like, and is integrated with the pinhole. For this reason, there is no displacement between the pinhole and the light receiving element, and aging does not matter in this regard.
[0076]
In this embodiment, the confocal laser coupler 50 outputs only an RF signal, and uses the outputs of the light receiving elements 33A to 35A to generate a focus error signal and a tracking error signal. This is for the purpose of simplifying the structure of the confocal laser coupler 50 and improving the production yield.
However, as will be described later, a configuration is also possible in which a focus error signal and a tracking error signal can be generated from the output of the confocal laser coupler.
[0077]
(Third embodiment)
FIG. 13 is a schematic diagram illustrating an optical recording medium reproducing device 300 according to the third embodiment of the present invention. As shown in the figure, the optical recording medium reproducing apparatus 300 includes an optical recording medium 10A, a light receiving / emitting element 221 with a pinhole, a polarizing beam splitter 222, a collimator / focus lens 223, a dichroic combiner 324, an aberration correction element 225, and floating optics. It has a head 80, a light receiving unit 30A (hologram element 31A, light receiving elements 33A to 35A), a monitor PD 226, and a tilt servo unit 227.
[0078]
The optical recording medium reproducing device 300 includes a semiconductor laser 351, a collimator lens 352, and an aberration correction element 353, and differs from the optical recording medium reproducing device 200 of the second embodiment in this point. Therefore, the optical recording medium reproducing device 300 has a dichroic combiner 324 instead of the mirror 224 of the optical recording medium reproducing device 200.
Further, as the optical recording medium 10, a recording layer 11A is not provided with a groove, and an optical recording medium 10A having a separate tracking groove layer 12A is used.
[0079]
The light emitted from the light emitting / receiving element with pinhole 221 enters the optical recording medium 10A via the polarization beam splitter 222, the collimator / focus lens 223, the dichroic combiner 324, the aberration correction element 225, and the floating optical head 80. .
The return light reflected from the recording layer 11A of the optical recording medium 10A passes through the floating optical head 80, the aberration correction element 225, the dichroic combiner 324, the collimator / focus lens 223, and the polarization beam splitter 222, and is received by a pinhole. The light enters the light emitting element 221 and the light receiving unit 30A.
[0080]
The light emitted from the semiconductor laser 351 is incident on the optical recording medium 10A via the collimator lens 352, the aberration correction element 353, the dichroic combiner 324, the aberration correction element 225, and the floating optical head 80. The return light reflected from the groove layer 12A of the optical recording medium 10A passes through the floating optical head 80, the aberration correction element 225, the dichroic combiner 324, the collimator / focus lens 223, and the polarization beam splitter 222, and is received on the light receiving unit 30A. Incident on.
[0081]
In the second embodiment, the detection of the RF signal, the focus error signal, the tracking error signal, and the tilt is performed only by the light emitted from the light emitting / receiving element with pinhole 221.
On the other hand, in the present embodiment, the generation of the RF signal, the focus error signal, and the tilt detection signal is performed by the light emitted from the light emitting / receiving element with pinhole 221, and the generation of the tracking error signal is performed by the light emitted from the semiconductor laser 351. It is carried out. Here, the wavelength of the light emitting / receiving element with pinhole 221 and the semiconductor laser 351 can be set to 658 nm for the former and 780 nm for the latter, for example.
As described above, the tracking error signal is generated using the light source (semiconductor laser 351) and the groove layer 12A that are separate from the RF signal, thereby improving the reliability of tracking.
[0082]
In this embodiment, since the recording layer 11A is not provided with a groove for tracking, the necessity of the tilt servo is increased as compared with the second embodiment.
The other points are not essentially different from the second embodiment, and the description is omitted.
[0083]
(Fourth embodiment)
In the present embodiment, a case is described in which an optical recording medium reproducing device 400 having a pinhole-equipped light emitting / receiving element 221 capable of generating a tracking error is used. At this time, the overall configuration of the optical recording medium reproducing device 400 can use the configuration already described in the second and third embodiments, and thus the overall configuration is omitted.
In the present embodiment, since a tracking error can be generated by the light receiving / emitting element 221 with the pinhole, the necessity of providing the light receiving unit 30A is reduced.
[0084]
FIG. 14 is a perspective view showing a confocal laser coupler 70 as another configuration example of the light emitting / receiving element 221 with a pinhole.
As shown in the figure, a confocal laser coupler 70 includes a semiconductor laser LD on a semiconductor substrate 71, a triangular pyramid-shaped semiconductor structure 72 having three reflecting surfaces M11, M12, and M13, and two quadrant photodiodes. The light receiving unit 73 includes a PDR (PDR1, PDR2, PDR3, PDR4) and a PDL (PDL1, PDL2, PDL3, PDL4).
The two four-division photodiodes PDR and PDL are each divided into four substantially quadrangular by two division lines crossing each other.
[0085]
The reflection surface M11 is provided to face one of the emission end faces of the semiconductor laser LD, and reflects light emitted from the semiconductor laser LD.
The emitted light reflected by the reflection surface M11 is converged and irradiated on the optical recording medium 10 by the floating optical head 80, and the return light reflected from the optical recording medium 10 is converged by the collimator / focus lens 223 and confocal laser coupler 70 Is returned to.
This return light is reflected by the reflecting surfaces M12 and M13, and irradiates the four-division photodiodes PDR and PDL, respectively.
[0086]
By performing calculations on signals obtained from the four-division photodiodes PDR1 to PDR4 and PDL1 to PDL4, a focus error signal, a tracking error signal, and the like can be generated. Further, an RF signal can be generated based on the sum total of the outputs from the entire four-division photodiodes PDR1 to PDR4 and PDL1 to PDL4.
By limiting the size of the semiconductor structure 72 to, for example, an Airy disk (diameter: 1.22 λ / NA), the light emitting / receiving element 221 with a pinhole can be configured.
[0087]
(Other embodiments)
The embodiment of the present invention is not limited to the above embodiment, and can be extended and changed. Extended and modified embodiments are also included in the technical scope of the present invention.
(1) For example, the optical recording medium reproducing apparatus may be either a fixed type in which the optical recording medium is steadily installed or a removable (removable) type in which the optical recording medium is detachably installed. In the case of the removable system, the optical recording medium reproducing device is provided with an optical recording medium holding means such as a stage (table), and the optical recording medium holding means holds the optical recording medium.
[0088]
(2) Regarding the return light from the optical recording medium, the case where mainly the reflected light from the recording layer is used has been described. Can read information from an optical recording medium.
[0089]
(3) A disc-shaped or other appropriate shape can be adopted as the shape of the optical recording medium.
Further, information can be recorded on the optical recording medium by various means. That is, the optical recording medium referred to here may be any device as long as information can be read by optical means, and the writing means is not limited.
[0090]
(4) In the above embodiment, the case where the optical recording medium reproducing apparatus is used for reproducing (reading) the information recorded on the optical recording medium is mainly described, but the information recorded on the optical recording medium by the optical recording medium reproducing apparatus is used. Writing, erasing, etc. may be performed. For example, means for optically writing information, such as a magneto-optical disk, can be provided to an optical recording medium reproducing apparatus.
[0091]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an optical recording medium reproducing apparatus capable of increasing the capacity of an optical recording medium.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view of a configuration example of an optical recording medium.
FIG. 2 is a perspective view illustrating a configuration example of a flying optical head.
FIG. 3 is a perspective view illustrating a configuration example of a flying optical head.
FIG. 4 is a schematic diagram illustrating an example in which a focal position is adjusted using an afocal optical system.
FIG. 5 is a perspective view illustrating a configuration example of a flying optical head.
FIG. 6 is a perspective view illustrating a configuration example of a floating optical head.
FIG. 7 is a graph showing spherical aberration.
FIG. 8 is a schematic diagram showing the overall configuration of the optical recording medium reproducing device according to the first embodiment of the present invention.
FIG. 9 is a graph showing the relationship between the depth of focus and the output RF signal and focus error signal when the optical recording medium is reproduced using the optical recording medium reproducing apparatus.
FIG. 10 is a diagram for explaining that, when the optical recording medium is inclined with respect to the optical axis of incident light, the information reading position shifts for each recording layer.
FIG. 11 is a schematic diagram illustrating an overall configuration of an optical recording medium reproducing device according to a second embodiment of the present invention.
FIG. 12 is a perspective view illustrating a confocal laser coupler which is a specific configuration example of a light emitting / receiving element with a pinhole.
FIG. 13 is a schematic diagram illustrating an overall configuration of an optical recording medium reproducing device according to a third embodiment of the present invention.
FIG. 14 is a perspective view illustrating a configuration example of a confocal laser coupler.
[Explanation of symbols]
10, 10A, 10B optical recording medium
11, 11A, 11B each recording layer
12A Groove layer
30 Light receiving unit
31 Hologram element
32 pinhole
33 light receiving element
50 confocal laser coupler
51 Semiconductor substrate
52 Light emitting unit
53 Receiver
80, 80A, 80B, 80C, 80D Floating Optical Head
81 Slider member
82 2nd lens
83 suspension
84 Focus adjustment mechanism
85 Objective lens
86 solid immersion lens
87 plate member
87a, 87b Wedge prism
88 mirror
89 Condenser lens
91,92 lens
93 Afocal optical system
95 Optical fiber
100 Optical recording medium reproducing apparatus
121 light source
121 Semiconductor Laser
122 Collimator lens
122 Polarizing beam splitter
123,124 Anamorphic prism
125 non-polarizing beam splitter
126 Aberration correction element
127 Polarizing beam splitter
128 wave plate
129 Afocal optical system
131 dichroic combiner
141 light source
142 Collimator lens
143,144 Anamorphic prism
151-153 Condenser lens
160 tilt servo unit
171,172 Monitor PD

Claims (15)

A light emitting unit that emits light,
An optical recording medium having a plurality of recording layers capable of optically reading information,
The optical recording medium has a surface that is closely opposed to the surface of the light emitting unit at a distance within the emission wavelength of the light emitting unit, and focuses light emitted from the light emitting unit to any of the recording layers of the optical recording medium. An optical head,
Corresponding to the light focused by the optical head, an optical member for focusing return light returned from the optical recording medium,
A light receiving unit that receives the light converged by the optical member,
An optical recording medium reproducing apparatus, comprising: A light emitting unit that emits light,
A stage for holding an optical recording medium having a plurality of recording layers capable of optically reading information,
The optical recording medium has a surface that is closely opposed to the surface of the light emitting unit at a distance within the emission wavelength of the light emitting unit, and focuses light emitted from the light emitting unit to any of the recording layers of the optical recording medium. An optical head,
Corresponding to the light focused by the optical head, an optical member for focusing return light returned from the optical recording medium,
A light receiving unit that receives the light converged by the optical member,
An optical recording medium reproducing apparatus, comprising: 2. The optical recording medium reproducing apparatus according to claim 1, wherein the return light includes any of light transmitted, reflected, or generated in any of the plurality of recording layers of the optical recording medium. The optical recording medium reproducing device according to claim 1, wherein the return light is an incoherent light. The optical recording medium reproducing apparatus according to claim 1, wherein a wavelength of the return light is different from a wavelength of light emitted from the light emitting unit. 2. The optical recording medium reproducing apparatus according to claim 1, wherein the optical head is a floating optical head that floats from the optical recording medium by a flow of air generated by a relative movement with the optical recording medium. . 2. The optical recording medium reproducing apparatus according to claim 1, further comprising a recording layer identification unit that identifies a recording layer on which light emitted from the optical head is focused. 8. The optical recording medium reproducing apparatus according to claim 7, wherein the recording layer identification unit identifies each recording layer by referring to a table representing a relationship between the depth of the recording layer and the intensity of the return light. . 2. The optical recording apparatus according to claim 1, wherein the optical recording medium reproducing apparatus further comprises a convergence position adjusting means for adjusting a convergence position of the convergent light from the optical head in a thickness direction of the optical recording medium. Media playback device. 10. The optical recording medium reproducing apparatus according to claim 9, wherein the convergence position adjusting means includes an afocal optical system. 10. The optical recording medium reproducing apparatus according to claim 9, wherein the convergence position adjusting means includes a variable refractive index element. 10. The optical recording medium reproducing apparatus according to claim 9, wherein the convergence position adjusting means includes a wedge prism. The optical recording medium reproducing apparatus according to claim 1, further comprising a pinhole between the optical member and the light receiving unit. 14. The optical recording medium reproducing apparatus according to claim 13, wherein the light emitting unit, the pinhole, and the light receiving unit are integrally formed on a same substrate. 2. The optical recording medium reproducing apparatus according to claim 1, further comprising a detection unit that detects at least one of a focus state, a tracking state, and a tilt state with respect to the optical recording medium.

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