WO2007114371A1 - Optical pickup and information device - Google Patents

Abstract

An optical pickup (100) is provided with (i) a light source for outputting laser beams; (ii) an optical system (108 or the like) for guiding the outputted laser beams to one of a plurality of recording layers; (iii-1) a first light receiving element (114 or the like) for receiving returning beams reflected by the recording layers; (iii-2) a second light receiving element (114 or the like) for receiving stray light; (iv) a pin hole (117) having a prescribed opening section which selectively transmits a part of one returning beam reflected by one recording layer, among the returning beams, so as to be received by the first light receiving element; (v) an operating means (314c or the like) for operating RF signals based on the one received returning beam; (vi) an operation control means (314) for controlling the operating means to operate the RF signals based on operation coefficients, by calculating the operation coefficients based on a difference between one signal component which corresponds to the one returning beam and other signal component which corresponds to the stray light.

Description

 Specification

 Optical pickup and information equipment

 Technical field

 The present invention relates to a technical field of an optical pickup that irradiates a laser beam when data is recorded or reproduced on an information recording medium such as a DVD, and an information device including the optical pickup.

 Background art

 [0002] Information such as a multi-layer optical disc that optically records or reproduces information signals (data) using laser light, such as a double-layer CD or a dual-layer DVD A recording medium has been developed. In such a multilayer optical disc, the distance between the recording layer and the recording layer is wide, and the signal from the selected recording layer may deteriorate due to the influence of spherical aberration. There is a tendency to narrow the interval with the recording layer. However, when the distance between the recording layer and the recording layer becomes narrow, the desired light of the selected recording layer (hereinafter referred to as “one” is appropriately transmitted to the return light of the multilayer optical disk force due to so-called interlayer crosstalk. Reflected light reflected on other recording layers other than the one recording layer (hereinafter referred to as “referred to as“ one return light ”as appropriate”). The component of “stray light” is also included at a high level. Therefore, for example, the SZN ratio of signal components such as playback signals may decrease.

 In detail, it is generally known that a signal component of one return light and a stray light component in a multilayer optical disc are in a trade-off relationship. In other words, when the area of the light receiving area of the light receiving means is reduced, the stray light component can be lowered to a relatively low level to reduce the effect of stray light, but at the same time, the signal component of one return light is also reduced. The level will be relatively low and the SZN ratio will also decrease. On the other hand, when the area of the light-receiving region is increased, it is possible to bring the signal component of one return light to a relatively high level. At the same time, the stray light component also becomes a relatively high level. The technical problem will be that the ratio will also decrease.

[0004] Therefore, Non-Patent Document 1 describes a double-layer Blu-ray Disc. The following describes a technique for avoiding the incidence of stray light to a light receiving element by separating the push-pull signal from the signal light by a hologram element in a tracking method during recording or reproduction.

 [0005] Alternatively, in Non-Patent Document 2, in order to reduce the influence of stray light contained in signal components from each recording layer of a multilayer information recording medium, it is fixed in a confocal optical system. It describes a technique for spatial filtering (spatial removal) using a pinhole.

 [0006] Alternatively, in Patent Document 1, a technique for separating reflected light from each recording layer with high accuracy by utilizing the difference in the angle of the optical axis of the return light of each recording layer force of a two-layer type optical disc. It is described.

 [0007] Alternatively, Non-Patent Document 3 describes, for example, an optical pickup of a multi-layer information recording medium provided with a plurality of light receiving means respectively corresponding to orthogonal optical axes.

 [0008] Patent Document 1: Japanese Patent Laid-Open No. 2005-228436

 Non-Patent Document 1: "Development of 1-beam tracking system suitable for double-layer Blu-ray disc" Matsushita Electric Industrial Co., Ltd. AV Core Technology Development Center Opto Device Group IEICE Technical Report CPM2005-149 ( 2005-10)) The Institute of Electronics, Information and Communication Engineers ρ31-34

 Non-Patent Document 2: "3D Multi-layer Bit Recording Memory" Yoshimasa Kawada (Faculty of Engineering, Shizuoka University) Laser Symposium 2005

 Non-Special Reference 3: “SONY Experimental ¾etup” ISOM (International Symposium on Optical Memory) Lecture 2004

 Disclosure of the invention

 Problems to be solved by the invention

However, according to Non-Patent Document 1 described above, as shown in FIG. 14, in a light receiving element for receiving a focus error signal or an RF signal, stray light (“ (See the overlap between Stray light ”and“ Transmitted beam ”), and the SZN ratio of the signal component of the return light from the desired recording layer is reduced due to stray light. There will be technical problems.

 [0010] Alternatively, according to Non-Patent Document 2 described above, in a finite optical system including a confocal optical system, an optimum pinhole, for example, Z, is selected depending on the position of the recording layer or the position where tracking is performed. Since the position in the axial direction changes, there arises a technical problem that it becomes difficult to appropriately spatially filter the influence of stray light.

 [0011] Alternatively, according to Patent Document 1 and the like described above, a technical problem arises that it is difficult to manage or control various aberrations. Alternatively, when the recording layer is changed, a technical problem arises that it is necessary to optimize the position in the z-axis direction of the light receiver or the condensing lens that collects the return light.

 The present invention has been made in view of, for example, the conventional problems described above. For example, in an information recording medium such as a multilayer optical disk, data can be reproduced with higher accuracy while reducing the influence of stray light. Alternatively, it is an object to provide an optical pickup that enables recording and an information device including such an optical pickup.

 Means for solving the problem

 [0013] (Optical pickup)

 In order to solve the above problems, an optical pickup according to the present invention is an optical pickup that performs at least one of recording and reproduction of data on a recording medium including a plurality of recording layers, and a light source that irradiates laser light; An optical system that guides the irradiated laser light to one recording layer of the plurality of recording layers, and (i) reflection on the one recording layer due to the guided laser light. A light receiving means including a first light receiving element for receiving the one return light, and (ii) a second light receiving element for receiving the stray light reflected on the other recording layer of the plurality of recording layers; Based on the pinhole having a predetermined opening for selectively passing the one return light and allowing the first light receiving element to receive the received light, the RF corresponding to the data is received. Computing means for computing a signal; A calculation coefficient is calculated based on a difference between one signal component corresponding to the return light and another signal component corresponding to the stray light, and the RF signal is calculated based on the calculation coefficient. And an arithmetic control means for controlling the arithmetic means.

According to the optical pickup of the present invention, the laser light emitted from the light source is, for example, an objective lens. The light is guided to one of the plurality of recording layers and condensed by an optical system such as a lens, a beam splitter, or a prism. At the same time, one return light reflected on one recording layer is received by the light receiving means. Therefore, the focused laser beam guided to one recording layer can reproduce information pits and marks formed on the one recording layer. Therefore, it is possible to reproduce predetermined information with the optical disc power. Alternatively, the focused laser beam can form information pits and marks in one recording layer. Therefore, it is possible to record predetermined information on the optical disc. Subsequently, an RF signal corresponding to the data is calculated by the calculation means based on one return light.

In particular, according to the present invention, the first light receiving element selectively receives one return light at a relatively high level by a predetermined pinhole. At the same time, the second light receiving element receives stray light selectively, that is, at a relatively high level. Here, the “pinhole” according to the present invention includes an opening having a predetermined size, that is, a so-called hole, and allows laser light to be spatially filtered by passing through the opening. Means a possible member. Also, “selectively receiving one return light” according to the present invention means that a signal component of one return light is received at a relatively high level compared to the signal level of the other return light. Means that. It may mean that it includes both one return light and the other return light. The calculation coefficient is calculated based on the difference between one signal component corresponding to one return light and another signal component corresponding to stray light under the control of the calculation control means. Based on the calculated calculation coefficient, the calculation means is controlled to calculate the RF signal. In addition, the size of the opening of the pinhole may be the size including the maximum amount of the return light component, or the signal S / N ratio (Signal to Noise Ratio) may be the best size. It can be arbitrarily selected depending on the method of use.

Specifically, when one return light is focused at an opening of a predetermined pinhole, at this condensing point position, only the return light including the maximum amount of one return light component is present. Optionally, it can pass through this predetermined pinhole opening. On the other hand, in this case, since the stray light is not focused, the light diameter of the stray light beam is increased at a predetermined pinhole position. Therefore, since stray light spreads at the pinhole position, it cannot pass through the opening of the predetermined pinhole. It is possible to filter to

 As a result, in addition to significantly reducing the effect of stray light, the effect of stray light can be grasped quantitatively or qualitatively, and a predetermined calculation based on the calculation coefficient can be performed, thereby returning one return. The ideal signal component in the light (the desired return light) can be calculated, and data can be played back or recorded with higher accuracy when playing back or recording on a multilayer optical disc. It is.

 [0018] One aspect of the optical pickup of the present invention includes a variable-focus lens that condenses the one return light in the predetermined opening, and the variable-focus lens that condenses the one return light. First control means for applying a predetermined voltage;

 According to this aspect, under the control of the first control means, a predetermined voltage is applied to the variable focus lens so that one return light is focused at a predetermined pinhole position. Yes. Therefore, a given pinhole selectively passes one return light, that is, passes one return light at a relatively high level and spatially filters (spatially removes) stray light. Can be realized more effectively.

 As a result, by reducing the influence of stray light, it is possible to improve the SZN ratio of the signal component of one return light and to reproduce the data recorded on the multilayer optical disk with higher accuracy. Noh. In addition, by reducing the influence of stray light, it is possible to improve the SZN ratio of the signal component of one return light and to record data on a multilayer optical disk with higher accuracy.

 [0021] Another aspect of the optical pickup of the present invention further includes second control means for controlling a relative positional relationship between the predetermined opening and the light receiving means.

 [0022] According to this aspect, for example, the spatial positional relationship between the predetermined pinhole and the light receiving means (PD) (specifically, the positional relationship in the X-axis, y-axis, or z-axis direction) Based on the control of the positional relationship by the second control means that controls ()), it is possible to selectively pass one return light and spatially filter (remove spatially) stray light with high accuracy. It is.

[0023] In the aspect related to the second control means described above, the second control means includes a Z-axis direction which is an optical axis direction, an X-axis direction orthogonal to the Z-axis direction, and the Z-axis direction and the The relative positional relationship may be controlled based on the Y-axis direction that is orthogonal to the X-axis direction. Yes.

 With this configuration, one return light is controlled based on the control of the relative positional relationship between the predetermined pinhole and the light receiving means (PD) on the optical axis (so-called Z-axis direction). It is possible to more precisely realize that the stray light is spatially filtered (spatial removal) by selectively passing the light.

 [0025] In another aspect of the optical pickup of the present invention, the first light receiving element receives inner diameter light including an optical axis in the one return light, and the second light receiving element is the one return light. It does not include the optical axis in the light!

[0026] According to this aspect, the first light receiving element can selectively receive the inner diameter light including the optical axis of one return light at a relatively high level by the predetermined pinhole. The At the same time, the second light receiving element can selectively receive the outer diameter light that does not include the optical axis in one return light at a relatively high level.

In another aspect of the optical pickup of the present invention, the first control unit applies the predetermined voltage based on the one return light received by the first light receiving element.

[0028] According to this aspect, under the control of the first control means, the condensing point position determined with high accuracy based on, for example, the signal level of at least one return light received by the first light receiving element. A predetermined voltage corresponding to can be applied to the variable focus lens.

[0029] In another aspect of the optical pickup of the present invention, the second control unit is configured such that, based on the one return light received by the first light receiving element, the predetermined opening, the light receiving unit, Controls the relative positional relationship between.

[0030] According to this aspect, under the control of the second control means, at least the predetermined pinhole and the light receiving means based on, for example, the signal level of the one return light received by the first light receiving element. It is possible to control the relative positional relationship with high accuracy.

[0031] In the aspect related to the first and second light receiving elements described above, the first light receiving element is disposed relatively close to the optical axis of the laser beam, and the second light receiving element is separated from the optical axis. It may be configured to be placed relatively far away.

With this configuration, (i) the first light receiving element that can receive one return light more efficiently by being arranged, for example, on the inner peripheral side, and (ii), for example, the outer peripheral side Stray light by being placed in Based on the second light-receiving element that can receive light more efficiently, in addition to significantly reducing the effects of stray light, the effects of stray light can be grasped quantitatively or qualitatively with higher accuracy. It is possible.

 [0033] In another aspect of the optical pickup of the present invention, the pinhole includes a third light receiving element for receiving the one return light on an irradiation surface on which the return light is irradiated. 1 The control means applies the predetermined voltage based on the one return light received by the third light receiving element.

 [0034] According to this aspect, under the control of the first control means, at least the condensing point position determined with high accuracy based on, for example, the signal level of one return light received by the third light receiving element. A predetermined voltage corresponding to can be applied to the variable focus lens.

 [0035] In another aspect of the optical pickup of the present invention, the pinhole includes a third light receiving element for receiving the one return light on an irradiation surface on which the return light is irradiated. 2 The control means controls the relative positional relationship between the predetermined opening and the light receiving means based on the one return light received by the third light receiving element.

 According to this aspect, under the control of the second control means, at least based on, for example, the signal level of the one return light received by the third light receiving element, the predetermined pinhole and the light receiving means It is possible to control the relative positional relationship with high accuracy.

 [0037] In the aspect according to the third light receiving means described above, the pinhole is formed on the irradiation surface on which the return light is irradiated due to the third light receiving element and the guided laser beam. At least a fourth light receiving element for receiving stray light reflected by the other recording layer, and the third light receiving element is disposed relatively close to the optical axis of the laser beam. The fourth light receiving element may be arranged relatively far from the optical axis.

[0038] According to this configuration, (i) the third light receiving element that can receive one return light more efficiently by being arranged, for example, on the inner peripheral side, and (ii), for example, the outer peripheral side Based on the fourth light receiving element that can receive stray light more efficiently, the effect of stray light can be reduced effectively and quantitatively or qualitatively. It is possible to grasp with higher accuracy. In another aspect of the optical pickup of the present invention, the shape and area of the light receiving means are defined based on optical characteristics or physical characteristics in the optical system or the predetermined opening. The

 [0040] According to this aspect, the shape and area of the light receiving means based on optical characteristics such as refractive index or physical characteristics such as magnetic, electrical or structural characteristics. Is defined. In particular, the “physical characteristic” according to the present invention may be a distance between a pinhole and a light receiving means, for example. Alternatively, the “physical property” may be, for example, the diameter of the opening of the pinhole. Therefore, this light receiving means can receive one return light while effectively reducing the influence of stray light.

 [0041] In another aspect of the optical pickup of the present invention, the light receiving means is divided into at least two parts in line symmetry or point symmetry.

 [0042] According to this aspect, for example, under the control of the first control means described above, based on one return light (signal level thereof) received by the light receiving means divided into at least two parts in line symmetry or point symmetry. Thus, the influence of light is reduced by a predetermined pinhole. Therefore, it is possible to improve the SZN ratio of the signal component of one return light and reproduce the data recorded on the multilayer optical disk with higher accuracy. By reducing the effect of stray light, it is possible to improve the SZN ratio of the signal component of one return light and to record data on a multilayer optical disc with higher accuracy.

 [0043] (Information equipment)

 In order to solve the above-described problems, an information device according to the present invention records the data by irradiating the optical disc with the above-described optical pickup of the present invention (including various aspects thereof) and the laser beam. Or recording / reproducing means for performing reproduction.

 [0044] According to the information device of the present invention, while enjoying the same benefits as the above-described various benefits of the optical pickup of the present invention, data is recorded on the optical disc, or data recorded on the optical disc is reproduced. can do.

 [0045] These effects and other advantages of the present invention will become more apparent from the embodiments described below.

[0046] As described above, according to the optical pickup of the present invention, the light source, the optical system, and the first light receiving element. A child, a second light receiving element, a predetermined pinhole, a calculation means, and a calculation control means. Therefore, by reducing the influence of stray light, the SZN ratio of the signal component of one return light can be improved and the data recorded on the multilayer optical disk can be reproduced with higher accuracy. By reducing the effect of stray light, it is possible to improve the SZN ratio of the signal component of one return light and to record data on a multilayer optical disk with higher accuracy.

[0047] Alternatively, the information device of the present invention includes a light source, an optical system, a first light receiving element, a second light receiving element, a predetermined pinhole, a calculation means, a calculation control means, and a recording / reproducing means. Therefore, by reducing the influence of stray light, the SZN ratio of the signal component of one return light can be improved and the data recorded on the multilayer optical disk can be reproduced with higher accuracy. By reducing the effect of stray light, it is possible to improve the SZN ratio of the signal component of one return light and to record data on a multilayer optical disk with higher accuracy.

 Brief Description of Drawings

 FIG. 1 is a block diagram showing a basic configuration of an information recording / reproducing apparatus and a host computer according to an embodiment of an information recording apparatus of the present invention.

 FIG. 2 is a block diagram schematically showing a more detailed configuration of the pickup 100 in the information recording / reproducing apparatus 300 in the example.

 FIG. 3 is a schematic diagram schematically showing a confocal optical system according to the present example.

 FIG. 4 is a schematic diagram schematically showing one specific example of an optical element for selecting one return light according to the present embodiment.

 FIG. 5 is a schematic diagram schematically showing another specific example of a light receiving element that receives one return light according to the present embodiment.

 FIG. 6 is a schematic diagram schematically showing another specific example (No. 1) of the optical element for selecting one return light according to the present embodiment.

 FIG. 7 is a schematic diagram schematically showing another specific example (No. 2) of the optical element for selecting one return light according to the present embodiment.

 FIG. 8 is a graph schematically showing a process of calculating a desired signal component based on signal components received at the inner and outer peripheral portions of the light receiving element according to the present embodiment.

FIG. 9 shows another specific example (part 3) of the optical element for selecting one return light according to the present embodiment. It is a schematic diagram shown typically.

 FIG. 10 is a schematic diagram schematically showing another specific example (No. 4) of the optical element for selecting one return light according to the present embodiment.

 FIG. 11 is a block diagram schematically showing a more detailed structure of the pickup 100 in the information recording / reproducing apparatus 300 in the second example.

 FIG. 12 is a schematic diagram schematically showing a confocal optical system according to a second example.

FIG. 13 is another schematic diagram schematically showing the confocal optical system according to the second example.

FIG. 14 is a plan view of a light receiving means according to a comparative example.

Explanation of symbols

 10 Optical disc

 100 optical pickup

 101 hologram laser

 102 LCD λ 2 plate

 103 Spherical aberration correction element

 104 Collimator lens

 108 Objective lens

 109 Actuator

 110 Objective lens Ζ Position sensor

 113 Hologram element

 114 photodetector

 117 (or 117a) pinhole

 300 Information recording and playback device

 302 Signal recording and playback means

 314 CPU

 314a Pinhole position controller

 314b Disc discriminator

 314c Operation unit

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in each embodiment in order with reference to the drawings.

 [0051] (1) Embodiment of information recording / reproducing apparatus

 First, the configuration and operation of an embodiment of the information recording apparatus of the present invention will be described in detail with reference to FIG. In particular, the present embodiment is an example in which the information recording apparatus according to the present invention is applied to an information recording / reproducing apparatus for an optical disc.

 [0052] (1 1) Basic configuration

 First, the basic configuration of the information recording / reproducing apparatus 300 and the host computer 400 in the embodiment of the information recording apparatus of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the basic configuration of the information recording / reproducing apparatus and the host computer according to the embodiment of the information recording apparatus of the present invention. The information recording / reproducing apparatus 300 has a function of recording recording data on the optical disc 100 and a function of reproducing recording data recorded on the optical disc 100.

 The internal configuration of the information recording / reproducing apparatus 300 will be described with reference to FIG. The information recording / reproducing apparatus 300 is an apparatus that records information on the optical disc 100 and reads information recorded on the optical disc 100 under the control of a CPU (Central Processing Unit) 314 for driving.

The information recording / reproducing apparatus 300 includes an optical disc 100, an optical pickup 301, a signal recording / reproducing means 302, an address detecting unit 303, a CPU (drive control means) 314, a spindle motor 306, a memory 307, and a data input / output control means 308. , And a bus 309.

 The host computer 400 includes a CPU (host control means) 401, a memory 402, an operation control means 403, an operation button 404, a display panel 405, a data input / output control means 406, and a bus 407. The

[0056] In particular, the information recording / reproducing apparatus 300 may be configured to be communicable with an external network by housing the host computer 400 provided with communication means such as a modem in the same casing. Alternatively, for example, the CPU (host control means) 401 of the host computer 400 provided with communication means such as i-link directly controls the information recording / reproducing apparatus 300 via the data input / output control means 308 and the bus 309. Communicate with external network by You can configure it to be possible.

 The optical pickup 301 performs recording / reproduction on the optical disc 100, and includes a semiconductor laser device and a lens. More specifically, the optical pickup 301 irradiates the optical disc 100 with a light beam such as a laser beam at a first power as a read light during reproduction, and modulates with a second power as a write light at the time of recording. Irradiate while letting go.

 The signal recording / reproducing means 302 records or reproduces the optical disc 100 by controlling the optical pickup 301 and the spindle motor 306. More specifically, the signal recording / reproducing means 302 is constituted by, for example, a laser diode driver (LD dryer) and a head amplifier. The laser diode driver drives a semiconductor laser (not shown) provided in the optical pickup 301. The head amplifier amplifies the output signal of the optical pickup 301, that is, the reflected light of the light beam, and outputs the amplified signal. More specifically, the signal recording / reproducing means 302 determines the optimum laser power by OPC pattern recording and reproduction processing together with a timing generator (not shown) under the control of the CPU 314 during OPC (Optimum Power Control) processing. A semiconductor laser (not shown) provided in the optical pickup 301 is driven so that the above can be performed. In particular, the signal recording / reproducing means 302, together with the optical pickup 301, constitutes an example of the “recording / reproducing means” according to the present invention.

 The address detection unit 303 also detects an address (address information) in the optical disc 100 for the reproduction signal power output by the signal recording / reproducing unit 302, for example, including a pre-format address signal.

 The CPU (drive control means) 314 controls the entire information recording / reproducing apparatus 300 by giving instructions to various control means via the bus 309. Note that software or firmware for operating the CPU 314 is stored in the memory 307. In particular, the CPU 314 constitutes an example of “control means” according to the present invention.

 The spindle motor 306 rotates and stops the optical disc 100 and operates when accessing the optical disc. More specifically, the spindle motor 306 is configured to rotate and stop the optical disc 100 at a predetermined speed while receiving spindle servo from a servo unit or the like (not shown).

[0062] The memory 307 is used by the buffer area for recording / reproducing data and the signal recording / reproducing means 302. Used in general data processing and OPC processing in the information recording / reproducing device 300 such as an area used as an intermediate buffer when converting to incoming data. The memory 307 has a program for operating as a recorder device, that is, a ROM area in which firmware is stored, a buffer for temporarily storing recording / playback data, a variable necessary for the operation of the firmware program, and the like. The RAM area to be stored is configured.

 The data input / output control means 308 controls external data input / output to / from the information recording / reproducing apparatus 300, and stores and retrieves data in / from the data buffer on the memory 307. Connected to the information recording / reproducing apparatus 300 via an interface such as SCSI or ATAPI! The drive control command issued from the external host computer 400 (hereinafter referred to as a host as appropriate) is the data input / output control means. It is transmitted to CPU 314 via 308. Similarly, recording / reproduction data is transmitted / received to / from the host computer 400 via the data input / output control means 308.

 [0064] In the host computer 400, the CPU (host control means) 401, the memory 402, the data input / output control means 406, and the bus 407 are substantially the same as the corresponding components in the information recording / reproducing apparatus 300. It is.

 The operation control means 403 receives and displays an operation instruction for the host computer 400. For example, the operation control means 403 transmits an instruction by the operation button 404 to the CPU 401, for example, recording or reproduction. Based on the instruction information from the operation control means 403, the CPU 401 transmits a control command (command) to the information recording / reproducing apparatus 300 via the data input / output means 406 to control the entire information recording / reproducing apparatus 300. You may comprise as follows. Similarly, the CPU 401 can transmit a command requesting the information recording / reproducing apparatus 300 to transmit the operation state to the host. As a result, since the operation state of the information recording / reproducing apparatus 300 such as recording or reproduction can be grasped, the CPU 401 displays the operation state of the information recording / reproducing apparatus 300 on the display panel 405 such as a fluorescent tube or LCD via the operation control means 403. Can output

[0066] One specific example of using the information recording / reproducing apparatus 300 and the host computer 400 in combination as described above is a household device such as a recorder device that records and reproduces video. This recorder device records video signals such as broadcast reception tuners and external connection jacks on a disc. And a device that outputs video signals played back from a disc to an external display device such as a TV.

. The program stored in the memory 402 is executed by the CPU 401 to operate as a recorder device. In another specific example, the information recording / reproducing apparatus 300 is a disk drive (hereinafter referred to as a drive as appropriate), and the host computer 400 is a personal computer workstation. The host computer such as a personal computer and the drive are connected via SCSI / ATAPI data input / output control means 308 (406), and the application such as writing software installed in the host computer controls the disk drive. To do.

[0067] (2) Optical pickup

 Next, with reference to FIG. 2, a more detailed configuration of the pickup 100 included in the information recording / reproducing apparatus 300 according to the present embodiment will be described. FIG. 2 is a block diagram schematically showing a more detailed configuration of the pickup 100 in the information recording / reproducing apparatus 300 according to the present embodiment.

 As shown in FIG. 2, the optical pickup 301 includes a hologram laser 101, a diffraction grating 102, a spherical aberration correction element 103, a collimator lens 104, a half mirror 105, an objective lens 108, and an actuator unit 109. Objective lens Z position sensor 110, condenser lens 112, hologram element 113, photodetector 114, pin hole 117, actuator 118 for changing the position of pin hole 117, and change in the position of pin hole 117. And a driver 119 to be controlled.

The hologram laser 101 constitutes a specific example of the “light source” of the present invention, and includes a laser chip, a substrate, a light receiving element, a hologram element, and the like that can emit laser light LB having a plurality of wavelengths (not shown). Configured. The laser chip and the light receiving element are arranged on the same substrate, and the hologram element is provided facing the laser beam LB output side of the substrate. The laser chip may emit a laser beam LB corresponding to the type of the optical disc 100 having a plurality of types. The hologram laser 11 may have functions as a plurality of light sources and detectors. Alternatively, instead of the hologram laser 101 including a laser chip and a light receiving element as a whole, a configuration including a plurality of laser chips and a plurality of light receiving elements separately may be adopted! The diffraction grating 102 diffracts laser light emitted from the hologram laser 101 into 0th-order light, + first-order diffracted light, and first-order diffracted light.

The spherical aberration correction element 103 performs optimal spherical aberration correction according to the substrate thickness of the optical disc 100.

 The collimator lens 104 converts the incident laser light LB into substantially parallel light and causes the half mirror 105 to radiate humans.

 The half mirror 105 transmits 100% of the laser beam LB incident from the hologram laser 101 side as it is and reflects the laser beam LB (that is, the reflection of the laser beam LB from the optical disc 100) that also receives the side force of the optical disc 100. Light) is transmitted by 90% and reflected by 10%. 10% of the reflected light reflected by the half mirror 105 is condensed on the photodetector 114 via the condenser lens 112 and the hologram element 113.

 [0074] The aperture limiting element 106 includes, for example, a liquid crystal shirt or the like, and the numerical aperture (NA: Numerical) of the objective lens 108 on the emission side of the laser beam LB according to the substrate thickness (in other words, the type) of the optical disc 100. Aperture) can be changed substantially! ,.

 The pinhole 117 is a member that includes an opening having a predetermined size, a so-called hole, and is capable of spatially filtering the laser light by passing through the opening.

 The objective lens 108 constitutes a specific example of the “optical system” of the present invention. The objective lens 108 collects the incident laser beam LB and irradiates it on the recording surface of the optical disc 100.

 The actuator unit 109 constitutes another specific example of the “optical system” of the present invention, and has a drive mechanism for changing the arrangement position of the objective lens 108. More specifically, the actuator unit 109 moves the position of the objective lens 108 in the focus direction (the Z direction, that is, the left and right direction in FIG. 2).

 [0078] The objective lens Z position sensor 110 is an absolute or relative position in the Z direction of the objective lens (that is, an absolute or relative position in the direction along the optical axis of the laser beam LB or in the focus direction). ). Further, the objective lens Z position sensor 110 outputs the measured position of the objective lens in the Z direction to a disc determination unit 314b described later.

The condensing lens 112 fluoresces the reflected light reflected by the half mirror 105. The hologram element 113 is disposed between the condensing lens 112 and the condensing point of the reflected light collected by the condensing lens 112. The hologram element 113 divides the reflected light spot formed on the hologram element 113 into a plurality of divided spot areas, and collects a part of the reflected light in each spot area in the photodetector 114. Shine.

 The photodetector 114 constitutes one specific example of the “light receiving means” of the present invention. The photodetector 114 receives a part of the reflected light in a plurality of spot regions collected by the hologram element 113 and receives the light. Detect the intensity level. The photodetector 114 outputs the detected light intensity level and the like to the calculation unit 314c described later.

 The CPU 314 includes a pinhole position control unit 314a, a disk determination unit 314b, and a calculation unit 314c therein.

 The pinhole position control unit 314a controls the position of the pinhole 117, for example, in the Z-axis direction together with the driver 119 described above.

 The disc discriminating unit 314b is based on the absolute or relative position in the Z direction of the objective lens output from the objective lens Z position sensor 110 and the detection signal of the reflected light output from the hologram laser 101. Then, the type (or substrate thickness) of the optical disk 100 loaded on the information recording / reproducing apparatus 300 is discriminated.

 The calculation unit 314c constitutes one specific example of the “calculation means” of the present invention, and is based on the light intensity level output from the photodetector 114! / Calculate the amount of ingredients.

 [0086] (3) A specific example of an optical element for selectively receiving one return light by the light receiving means

 Next, referring to FIG. 3 and FIG. 4, an optical element for selectively receiving one return light according to the present embodiment by the light receiving means (hereinafter referred to as “an optical element for selecting one return light” as appropriate). An example of a specific example will be described.

[0087] (3-1) Confocal optical system

 First, the confocal optical system according to the present embodiment will be described with reference to FIG. FIG. 3 is a schematic diagram schematically showing the confocal optical system according to the present embodiment. The optical axis direction in FIG. 3 and FIG. 4 described later is shown as the Z-axis direction.

As shown in FIG. 3, the confocal position is generally different for each recording layer. This implementation here The “confocal position” according to the example is a position where the laser beam is irradiated, focused on one recording layer, and scattered or reflected by the return light power converging lens, and is focused again. . In addition, the condensing position and the confocal position in one recording layer may have a conjugate relationship.

Specifically, under the control of the CPU 314, the return light focused and scattered or reflected by the laser beam LB force L1 layer by the actuator unit 109 and the objective lens 108 is reflected by the condenser lens 112. Again, focusing is performed at the confocal position “XI” in the Z-axis direction. On the other hand, under the control of the CPU 314, the laser beam LB is focused on the L2 layer by the actuator unit 109 and the objective lens 108, and the returned light that is scattered or reflected is again returned to the Z-axis direction by the condenser lens 112. Is focused at the confocal position “X2”. A specific example of “one return light” according to the present invention is “return light focused on and scattered or reflected on the L1 layer” or “return light focused on and scattered or reflected on the L2 layer”. It is composed of “light”.

 [0090] As described above, the focal point position and the confocal position in each recording layer are generally associated one-to-one. According to this confocal optical system, it is possible to perform fine adjustment at the time of designing the optical path with higher accuracy. Therefore, it is preferable to cope with time-series changes in the confocal position.

 [0091] A specific example of an optical element that selects the return light of (3-2)

 Next, referring to FIG. 4, a specific example of an optical element for selecting one return light according to the present invention will be described. FIG. 4 is a schematic diagram schematically showing one specific example of the optical element for selecting one return light according to the present embodiment.

[0092] As shown in FIG. 4, under the control of the CPU 314, the laser light LB is focused on the L2 layer by the actuator unit 109 and the objective lens 108, and the return light scattered or reflected is collected. The optical lens 112 focuses again at the confocal position “X2” in the Z-axis direction. In particular, according to the present embodiment, the pin hole 117 whose position can be changed in the Z-axis direction is provided. Then, under the control of the pinhole position control unit 314a, the opening of the pinhole 117 and the confocal position “X2” can be substantially matched. It should be noted that the position of the pinhole 117 can be changed not only in the Z-axis direction but also in the X-axis direction and the Y-axis direction orthogonal to the Z-axis direction. [0093] Specifically, when the return light of the L2 layer force is focused on the pinhole 117, at this confocal position “X2,” only the return light including the maximum component of the return light of the L2 layer force is obtained. Can selectively pass through the opening of this pinhole 117. On the other hand, in this case, since stray light (for example, return light from the L1 layer) is not focused, the diameter of the stray light beam is increased at the position of the pinhole 117. Therefore, since stray light spreads at the pinhole position, it can hardly or completely pass through the opening of the pinhole 117, so that stray light components can be spatially filtered (blocked) to the maximum. Is possible. When the return light from the L1 layer is focused on the pinhole 117, for example, the stray light component such as the return light from the L2 layer is spatially filtered by the pinhole 117 located at the confocal position “XI”. The actions that can be performed can be generally described in the same manner.

 As a result, the effect of stray light is remarkably reduced, so that the SZN ratio of the signal component of the return light from the desired recording layer is improved, and data is reproduced during reproduction or recording on a multilayer optical disc. Reproduction or recording can be realized with higher accuracy.

 [0095] (3-3) Other specific example of optical element for selecting return light

 Next, with reference to FIG. 5, another specific example of a light receiving element for receiving one return light according to the present invention will be described. FIG. 5 is a schematic diagram schematically showing another specific example of the light receiving element that receives one return light according to the present embodiment. Note that “A surface” is a view of the pinhole as viewed from the side irradiated with the return light, and “B surface” is a view of the pinhole as viewed from the light receiving element 114a side.

 [0096] As shown in [Eight sides] in FIG. 5, the pinhole 117 may include, for example, a light receiving region divided into four on the surface irradiated with the return light. Accordingly, the return light can be received before passing through the pinhole 117. As a result, compared with the case where light is received by the light receiving element 114a after passing through the return light pinhole 117, the position of the pinhole 117 is controlled based on the signal level of stray light, or by a liquid crystal lens described later. It is possible to appropriately control the focal point position. Alternatively, the pinhole 117 may be provided with a light receiving area divided into two in an inner peripheral area and an outer peripheral area in addition to or instead of the light receiving area divided into four.

[0097] (4) Other examples 1 Next, with reference to FIG. 6, another example (part 1) of the optical element for selecting one return light according to the present embodiment will be described. FIG. 6 is a schematic diagram schematically showing another specific example (No. 1) of the optical element for selecting one return light according to the present embodiment. Note that, in other specific examples (part 1), the same reference numerals are given to the configurations that are substantially the same as the configurations in the above-described specific example, and description thereof will be omitted as appropriate.

 [0098] As shown in FIG. 6, the laser beam LB force is focused on the L2 layer and scattered by the actuator unit 109 and the objective lens 108 under the control of the CPU 314 in substantially the same manner as in FIG. 4 described above. Alternatively, the reflected return light is focused again at the confocal position “X2” in the Z-axis direction by the condenser lens 112. In particular, according to the present embodiment, the pinhole 117a whose position is fixed in the Z-axis direction and the liquid crystal lens 118 (that is, one specific example of a variable focus lens capable of changing the focal position) ). Under the control of the CPU 314, the confocal position of the return light can be adjusted in the Z-axis direction by the liquid crystal lens 118, so that the opening of the pinhole 117a and the confocal position “X2” are substantially coincident. It is possible to Refer to pages 57 to 58 of Applied Physics 63rd No. 1 (1994) for the detailed mode of the liquid crystal lens (liquid crystal layer) that constitutes a specific example of the variable focus lens. Please refer to pages 59 to 62 of Applied Physics No. 63 卷 No. 1 (1994) for more detailed aspects of the electro-optic lens that constitutes the variable focus lens.

 As a result, the SZN ratio of the signal component of the return light from the desired recording layer is improved by remarkably reducing the influence of stray light in substantially the same manner as described above with reference to FIG. When reproducing or recording on an optical disc, it is possible to realize data reproduction or recording with higher accuracy.

 [0100] In particular, in another specific example, in order to change the confocal position, it is not necessary to include a mechanical drive device such as a motor, so that the optical pickup can be reduced in size and thickness. . In addition, since it is not necessary to provide a mechanical drive device, it is possible to reduce the power consumption of the optical pickup.

 [0101] (5) Other examples 2 —

Next, referring to FIG. 7 and FIG. 8, an optical element for selecting one return light according to the present embodiment Another specific example (part 2) will be described. FIG. 7 is a schematic diagram schematically showing another specific example (No. 2) of the optical element for selecting one return light according to the present embodiment. FIG. 8 is a graph schematically showing a process of calculating a desired signal component based on signal components received at the inner and outer peripheral portions of the light receiving element according to the present embodiment. In the other specific example (No. 2), the same reference numerals are given to the configurations that are substantially the same as the configurations in the above-described specific example, and the description thereof will be omitted as appropriate.

 [0102] As shown in FIG. 7, for example, by the optical element such as the pinhole 117 described above, the inner peripheral portion of the light receiving element 114a (see also the lower part of FIG. 7) is selectively, ie, The return light from the L2 layer is received at a relatively high level. At the same time, the outer peripheral portion of the light receiving element 114a (see also the lower side of FIG. 7) selectively receives stray light (for example, return light from the L1 layer) at a relatively high level. Under the control of the CPU 314, the optical system is based on the signal component from the L2 layer corresponding to the return light from the L2 layer and the signal component from the L1 layer corresponding to the stray light from the L1 layer. It is possible to guide light to the L2 or L1 layer. A specific example of the “first light receiving element” according to the present invention is configured by the inner peripheral portion of the light receiving element 114a, and the “second light receiving element” according to the present invention is configured by the outer peripheral portion of the light receiving element 114a. Let's make a concrete example of this.

 [0103] Further, the signal component may be at least one of an RF signal, a wobble signal, and an address signal (LPP). Alternatively, the signal component may be a control signal for performing focus servo or tracking servo.

 Specifically, as shown in the upper graph of FIG. 8, under the control of the CPU 314 or the arithmetic unit 314c, for example, the inner periphery of the light receiving element 114a (“PD (Photo Detector) in FIG. The signal component detected at the outer periphery of the light receiving element 114a (see “PD outer periphery” in FIG. 8) is used as a difference component from the signal component detected at the inner periphery of By subtracting), it is possible to detect the ideal signal component in the return light from the L2 layer (or L1 layer) that is not affected by stray light. The process of offsetting this signal component is expressed as the following equation (1).

 [0105] (desired signal component)

= (Signal component of the inner periphery of the light receiving element) One “K” X (Signal component of the outer peripheral part of the light receiving element) ...... Formula (1)

 However, “K” is a variable coefficient. In particular, the coefficient “κ” is optimized to minimize stray light from other layer forces depending on the change in position of the light receiving element in the axial direction and the size of the pinhole. This optimization is performed on an individual basis based on experimental, theoretical, empirical, simulation, etc.

 More specifically, the signal component detected at the inner periphery of the light receiving element 114a is expressed by the following equation (2), and the signal component detected at the outer periphery of the light receiving element 114a is expressed by the following equation (3) Consider the case indicated by).

[0107] (Signal component of the inner periphery of the light receiving element)

 = "L2" + "L2" + "L2" + "L 1" + "L2" + "L2" + "L 1"

 = 5 X "L2" + 2 X "L1" ...... Formula (2)

 However, “L2” is a signal component corresponding to the return light from the L2 layer, and “L1” is a signal component corresponding to the return light from the L1 layer.

[0108] (Signal component of the outer periphery of the light receiving element)

= 2 X “L2” + 5 X “L1” …… Equation (3).

Accordingly, in addition to the above-described equations (1), (2), and (3), the coefficient “K” is set to “2Ζ5 (2/5)”, so that the following equation (la ) And the ideal signal component in the return light from the L2 layer can be calculated.

[0110] (Ideal signal component in the return light from the L2 layer)

 = 5 X "L2" + 2 X "L1" One K {2 X "L2" + 5 X "L1"}

 = (21/5) X TL2J Equation (la).

As a result, (i) the signal component of the return light from the L2 layer selectively received at the inner periphery of the light receiving element 114a, that is, at a relatively high level, and (ii) the light receiving element 114a Based on the signal component of the return light from the L1 layer that is selectively received at the outer periphery, the ideal signal component in the return light of the L2 layer can be calculated.

[0112] Alternatively, the coefficient “K” is changed to “5Z2 (5/2)” in addition to the above-described equations (1), (2), and (3). Equation (lb) is obtained, and ideal signal generation in the return light from the L1 layer is obtained. Minutes can be calculated.

 [0113] (Ideal signal component in the return light from the L1 layer)

 = 5 X "L2" + 2 X "L1" One K {2 X "L2" + 5 X "L1"}

 = (-T21 / 2J) X TLIJ ...... Formula (lb).

 [0114] As a result, (i) the signal component of the return light from the L2 layer selectively received at the inner periphery of the light receiving element 114a, that is, at a relatively high level, and (ii) the light receiving element 114a Based on the signal component of the return light from the L1 layer that is selectively received at the outer periphery, the ideal signal component in the return light of the L1 layer can be calculated.

 As a result of the above, according to another specific example (No. 2) of the optical element that selects one return light according to the present embodiment, in addition to significantly reducing the influence of stray light, stray light Quantitatively or qualitatively grasping the effects of noise and using them actively, it is possible to calculate the ideal signal component in the desired return light. It is possible to realize data reproduction or recording with higher accuracy.

 [0116] Alternatively, as shown in the lower side of FIG. 7, by changing the area of the inner periphery of the light receiving element, an ideal signal component in the desired return light based on the degree of the influence of stray light Can be calculated with higher accuracy. Specifically, when the light diameter of the return light is relatively large (that is, when the amount of the return light irradiated to the light receiving element is relatively large), the radius of the inner periphery of the light receiving element is relatively If the light diameter of the return light is relatively small (that is, the amount of the return light irradiated to the light receiving element is relatively small), the light receiving element You may make it make the radius of an inner peripheral part relatively small.

 [0117] (6) Other examples 3

 Next, with reference to FIG. 9, another example (part 3) of the optical element for selecting one return light according to the present embodiment will be described. FIG. 9 is a schematic diagram schematically showing another specific example (part 3) of the optical element for selecting one return light according to the present embodiment. In the other specific example (No. 3), the same reference numerals are given to the configurations substantially the same as the configuration in the above-described specific example, and the description thereof will be omitted as appropriate.

As shown in FIG. 9, by making the confocal position of the return light from a desired recording layer such as the L2 layer substantially the same as that of the light receiving element 114b by the hologram element 113, for example, It is possible to selectively receive return light from a desired recording layer such as the L2 layer, that is, at a relatively high level. In particular, the shape and area of the light receiving element 114b are optical characteristics or physical (magnetic or electrical) characteristics in an optical element such as the hologram element 113 and an optical system such as the condenser lens 112, for example. It is possible to specify based on this. In addition, the shape and area of the light receiving element 114b can be defined based on various characteristics of the optical element and the optical system so that stray light such as return light from the L1 layer is not irradiated. It is.

 As a result, by effectively reducing the influence of stray light based on the shape and area of the light receiving element, the SZN ratio of the signal component of the return light from the desired recording layer is improved, and the multi-layer type When reproducing or recording on a disk, it is possible to achieve data reproduction or recording with higher accuracy.

 [0120] (7) Other examples 4

 Next, another specific example (No. 4) of the optical element for selecting one return light according to the present embodiment will be described with reference to FIG. FIG. 10 is a schematic diagram schematically showing another specific example (No. 4) of the optical element for selecting one return light according to the present embodiment. In the other specific examples (No. 4), the same reference numerals are given to the configurations that are substantially the same as the configurations in the one specific example described above, and the description thereof will be omitted as appropriate.

 [0121] As shown in FIG. 10, the hologram element 113 indicates the condensing point position of the signal light corresponding to the RF signal out of the return light from the desired recording layer such as the L2 layer, for example. Set to approximately the same position as 14r. Therefore, in the RF light receiving element 114r, it is possible to selectively receive the signal light corresponding to the RF signal out of the return light from the desired recording layer, that is, at a relatively high level. .

 [0122] Alternatively, the focal point position of the signal light corresponding to the focus error signal (FE signal) or tracking error signal (TE signal) out of the return light from the desired recording layer can be changed to the FEZTE light receiving element 114f. , Make it almost the same position. Therefore, the light receiving element 114f for FEZTE can selectively receive the signal light corresponding to the FE signal or TE signal out of the return light from the desired recording layer, that is, at a relatively high level. It is.

[0123] Alternatively, instead of the position where the “0th order light” of the return light is irradiated, “+ 1st order light” or 1st order light When the RF light receiving element 114r is arranged at the position where the RF light receiving element 114r is irradiated, for example, stray light such as return light of the L1 layer force can be effectively reduced from being irradiated to the RF light receiving element 114r. It is pretty.

 [0124] As a result, the SZN ratio of the signal component of the return light from the desired recording layer is improved by effectively reducing the influence of stray light based on the arrangement and roles of the plurality of light receiving elements. When reproducing or recording on a type of optical disc, it is possible to achieve data reproduction or recording with higher accuracy.

 [0125] (8) Optical pickup according to the second embodiment

 Next, with reference to FIG. 11, a more detailed configuration of the pickup 100 included in the information recording / reproducing apparatus 300 according to the present embodiment will be described. FIG. 11 is a block diagram schematically showing a more detailed configuration of the pickup 100 in the information recording / reproducing apparatus 300 according to the second embodiment.

 As shown in FIG. 11, the optical pickup 301 according to the second embodiment includes a hologram laser 101, a diffraction grating, and the collimator lens 104 and the condensing lens 112 omitted from the above-described embodiments. 102, spherical aberration correction element 103, half mirror 105, objective lens 108, actuator unit 109, objective lens Z position sensor 110, hologram element 113, photo detector 114, and pinhole 117. . Since these components are generally the same as those in the above-described embodiment, the description thereof is omitted for convenience.

 [8-12] (8-1) Confocal optical system according to Example 2 (when focused on L2 layer)

 Next, with reference to FIG. 12, the confocal optical system according to the second example when focused on the L2 layer will be described. FIG. 12 is a schematic diagram schematically showing the confocal optical system according to the second example. In FIG. 12, the optical axis direction is shown as the Z-axis direction.

Here, the “infinite optical system” according to the present embodiment is a general term for optical pickups in which the light beam incident on the objective lens is parallel light (collimated light). The number of parts increases. The “finite optical system” according to the present embodiment is a general term for pickups in which the light beam incident on the objective lens is a divergent light, and the collimating lens for the forward path and the backward path is not necessary, but the NA of the effective objective lens Therefore, the objective lens must have high performance. It is

 As shown in FIG. 12, even in a finite optical system, the confocal position is generally different for each recording layer. Specifically, under the control of the CPU 314, the laser beam LB force is focused on the L2 layer by the actuator unit 109 and the objective lens 108, and the returned light force scattered or reflected by the half mirror 105 is again used in the Z-axis direction. Is focused at the confocal position “X2”. On the other hand, when focused on the L2 layer, the stray light from the L1 layer (see the dotted line in FIG. 12) is also collected at the position “XI” near the light receiving element with the confocal position “X2” force. A specific example of “one return light” according to the present invention is configured by “return light focused on and scattered or reflected by the L2 layer”. Further, a specific example of “stray light” according to the present invention is configured by “stray light from the L1 layer when focused on the L2 layer”.

 [0130] (8-2) Confocal optical system according to the second example (when focused on the L1 layer)

 Next, with reference to FIG. 13, the confocal optical system according to the second example when focused on the L1 layer will be described. FIG. 13 is another schematic diagram schematically showing the confocal optical system according to the second example. In FIG. 13, the optical axis direction is shown as the Z-axis direction.

 As shown in FIG. 13, in the finite optical system focused on the L1 layer, the laser beam LB force is focused on the L1 layer by the actuator unit 109 and the objective lens 108 under the control of the CPU 314. The focused, scattered or reflected return light is focused again at the confocal position “X2” in the Z-axis direction by the half mirror 105. On the other hand, when focused on the L1 layer, the stray light from the L2 layer (see the dotted line in FIG. 13) is collected at the position “XI” where the confocal position “X2” force is also close to the light receiving element. In addition, another specific example of “one return light” according to the present invention is configured by “return light focused on and scattered or reflected by the L1 layer”. A specific example of “stray light” according to the present invention is configured by “stray light from the L2 layer when focused on the L1 layer”.

As described above, also in the finite optical system, the condensing point position and the confocal position in each recording layer are generally associated one-to-one. According to the confocal point optical system related to the finite optical system, it is possible to reduce the number of parts when designing the optical path. [0133] The present invention is not limited to the above-described embodiments, and the entire specification can be changed as appropriate without departing from the gist or concept of the invention which can be read, and an optical pickup with such a change. In addition, information devices are also included in the technical scope of the present invention.

 Industrial applicability

The optical pickup and information device according to the present invention can be used for an optical pickup that irradiates a laser beam when data is recorded or reproduced on an information recording medium such as a DVD. It can be used for information equipment provided with.

Claims

The scope of the claims  [1] An optical pickup that performs at least one of data recording and reproduction on a recording medium having a plurality of recording layers,  A light source that emits laser light;  An optical system for guiding the irradiated laser light to one recording layer of the plurality of recording layers;  Due to the guided laser beam, (i) a first light receiving element for receiving one return light reflected on the one recording layer, and (ii) another of the plurality of recording layers A light receiving means including a second light receiving element for receiving stray light reflected on the recording layer; and a pin having a predetermined opening for selectively passing the one return light and receiving the first light receiving element The hall,  An arithmetic means for calculating an RF signal corresponding to the data based on the one return light received;  An operation coefficient is calculated based on a difference between one signal component corresponding to the one return light and another signal component corresponding to the stray light, and the RF signal is calculated based on the operation coefficient. Calculation control means for controlling the calculation means so as to calculate  An optical pickup comprising: [2] A variable focus lens for condensing the one return light at the predetermined opening,  First control means for applying a predetermined voltage to the variable focus lens so as to collect the one return light; and  The optical pickup according to claim 1, further comprising: [3] The optical pickup according to [1], further comprising a second control means for controlling a relative positional relationship between the predetermined opening and the light receiving means. [4] The second control means includes an optical axis direction Z-axis direction and an X-axis direction orthogonal to the Z-axis direction. 4. The optical pickup according to claim 3, wherein the relative positional relationship is controlled based on the Z-axis direction and a Y-axis direction orthogonal to the X-axis direction. [5] The first light receiving element receives inner diameter light including an optical axis in the one return light, and 2. The optical pickup according to claim 1, wherein the second light receiving element receives outer diameter light that does not include an optical axis in the one return light. 6. The light according to claim 2, wherein the first control means applies the predetermined voltage based on the one return light received by the first light receiving element. Pick up.  [7] The second control means is based on the one return light received by the first light receiving element. 4. The optical pickup according to claim 3, wherein a relative positional relationship between the predetermined opening and the light receiving means is controlled. [8] The first light receiving element is disposed relatively close to the optical axis of the laser beam, and the second light receiving element is disposed relatively far from the optical axis. The optical pickup according to item 1. [9] The pinhole has a third light receiving element for receiving the one return light on an irradiation surface irradiated with the return light,  The first control means is based on the one return light received by the third light receiving element. 3. The optical pickup according to claim 2, wherein the predetermined voltage is applied.  [10] The pinhole has a third light receiving element for receiving the one return light on an irradiation surface irradiated with the return light,  The second control means is based on the one return light received by the third light receiving element. 4. The optical pickup according to claim 3, wherein a relative positional relationship between the predetermined opening and the light receiving means is controlled. [11] The pinhole is formed on the other recording layer of the plurality of recording layers due to the third light receiving element and the guided laser beam on the irradiation surface irradiated with the return light. At least a fourth light receiving element for receiving the stray light that is reflected  The third light receiving element is disposed relatively close to the optical axis of the laser beam, and the fourth light receiving element is disposed relatively far from the optical axis. The optical pickup according to item 8. [12] The shape and area of the light receiving means are the same as those in the optical system or the predetermined opening. 2. The optical pickup according to claim 1, wherein the optical pickup is defined based on an optical characteristic or a physical characteristic.  13. The optical pickup according to claim 1, wherein the light receiving means is divided into at least two parts in line symmetry or point symmetry. [14] The optical pickup according to claim 1;  A recording / reproducing means for recording or reproducing the data by irradiating the optical disc with the laser beam;  An information device comprising: