WO2011118177A1 - 光学ヘッド及び光情報装置 - Google Patents
光学ヘッド及び光情報装置 Download PDFInfo
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- WO2011118177A1 WO2011118177A1 PCT/JP2011/001613 JP2011001613W WO2011118177A1 WO 2011118177 A1 WO2011118177 A1 WO 2011118177A1 JP 2011001613 W JP2011001613 W JP 2011001613W WO 2011118177 A1 WO2011118177 A1 WO 2011118177A1
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- light
- light receiving
- optical head
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1381—Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0908—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only
- G11B7/0909—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only by astigmatic methods
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/13—Optical detectors therefor
- G11B7/131—Arrangement of detectors in a multiple array
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1384—Fibre optics
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
- G11B2007/0009—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage
- G11B2007/0013—Recording, reproducing or erasing systems characterised by the structure or type of the carrier for carriers having data stored in three dimensions, e.g. volume storage for carriers having multiple discrete layers
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
- G11B7/127—Lasers; Multiple laser arrays
- G11B7/1275—Two or more lasers having different wavelengths
Definitions
- the present invention relates to an optical head that records or reproduces information on an information recording medium such as an optical disk or an optical card, and an optical information device including the optical head.
- a conventional optical head photodetector includes a light receiving unit and an arithmetic circuit that performs a predetermined operation on an electrical signal obtained by photoelectric conversion of a light beam received by the light receiving unit.
- the light receiving unit is located in the vicinity of the approximate center of the photodetector, and an aperture is provided on the light incident side of the photodetector (see, for example, Patent Document 1).
- FIG. 29 is a diagram showing a configuration of an optical system of a conventional optical head described in Patent Document 1.
- FIG. 30 is a diagram showing details of a detection optical system of a conventional optical head.
- FIG. 31 is a diagram showing a light receiving surface of a photodetector of a conventional optical head.
- the optical head includes a semiconductor laser 401, a collimator lens 402, a beam splitter 403, an objective lens 404, a detection means 406, a photodetector 407, an aperture 408, and a diffraction grating 409.
- the light beam emitted from the semiconductor laser 101 is separated into a plurality of different light beams by the diffraction grating 409.
- the light beam that has passed through the diffraction grating 409 is converted into a parallel light beam by the collimator lens 402 and passes through the beam splitter 403.
- the light beam that has passed through the beam splitter 403 is converged by the objective lens 404 to become so-called three-beam convergent light. This convergent light is applied to the recording layer of the optical disc 405.
- the light reflected and diffracted by the recording layer of the optical disc 405 passes through the objective lens 404 again and is reflected by the beam splitter 403.
- the objective lens 404 is driven in the optical axis direction (focus direction) and the radial direction (radial direction) of the optical disk 405 by an objective lens actuator (not shown).
- the light beam reflected by the beam splitter 403 passes through the detection means 406 and enters the photodetector 407.
- the aperture 408 configured between the detection unit 406 and the photodetector 407 blocks stray light incident on the light receiving unit of the photodetector 407.
- the photodetector 407 receives the light beam that has passed through the aperture 408.
- One aperture 408a is formed in the aperture 408, and the shape of the opening 408a is substantially circular with the optical axis as the center as shown by the broken line in FIG.
- FIG. 32 is a diagram showing the arrangement of the light receiving portions on the light receiving surface of the photodetector of the conventional optical head.
- the light beam that has passed through the detection means 406 is received by the four-divided light receiving unit 410, and a so-called focus error signal is generated.
- FIG. 33 is a view showing a light detection system of a conventional optical head
- FIG. 34 is a view showing a light beam formed in a four-divided light receiving portion of the light detector of the conventional optical head.
- the detection means 406 has a cylindrical surface 406a on the light incident surface side and a concave lens surface 406b on the light exit surface side.
- the detecting means 406 generates astigmatic differences with different focal positions at an angle of 90 degrees in a plane orthogonal to the optical axis.
- the direction of the cylindrical surface 406a is arranged at an angle inclined by approximately 45 degrees with respect to the four-divided light receiving unit 410 of the photodetector 407.
- the relative distance between the recording layer of the optical disk 405 and the objective lens 404 changes due to surface shake of the optical disk 405 or the like.
- the light beam 412a at the focal position has a circular shape
- the light beam 412b at the front focal line and the light beam 412c at the rear focal line have elliptical shapes orthogonal to each other.
- a so-called focus error signal is detected by calculating the difference between the sum signals of the diagonal light receiving areas of the four-divided light receiving section 410, and calculating all the light receiving area sum signals of the four-divided light receiving section 410. A signal is detected.
- the sub-beam light receiving unit 411 of the photodetector 407 receives the sub-beam in the so-called three-beam method that is focused on the recording layer track of the optical disc 405 and reflected from the recording layer. Tracking is performed by a so-called three-beam method using a so-called push-pull signal calculated based on the received light amount of the main beam 412 of the quadrant light receiving unit 410 and a signal calculated based on the received light amount of the sub beam 413 of the sub beam light receiving unit 411. An error signal is generated, and tracking servo is performed so that the objective lens 404 follows the track of the recording layer of the optical disc 405.
- the optical detector 407 is fixed to a holder (not shown) in advance, and the optical axis of the photodetector 407 is adjusted so that the light beam enters the approximate center of the four-divided light receiving unit 410. Then, after the position of the photodetector 407 is determined, the holder and the photodetector 407 are fixed to an optical base (not shown).
- the aperture 408 is desirably as small as possible so that unnecessary surface reflected light reflected by the surface of the optical base does not enter the quadrant light receiving unit 410 or the sub beam light receiving unit 411.
- the aperture diameter of the aperture 408 is a value that takes into account the relative positional deviation between the diameter of the light beam passing therethrough and the photodetector 407, the dimensional tolerance of the aperture 408, and the like.
- the lateral magnification of the so-called detection optical system which is the ratio of the focal length of the objective lens of the optical head and the focal length of the collimator lens, is increased.
- the stray light reflected from the other layer of the optical disc needs to be configured not to enter the sub-beam light receiving unit 411, and the outbound detection optical system must be downsized.
- the stray light reflected by the other layer enters the sub-beam light receiving unit 411, an offset is generated in the tracking error signal.
- the interference between the light reflected from the target self layer and the light reflected from the other layer causes the DC level of the tracking error signal to fluctuate, greatly degrading the performance of the tracking servo, and reducing the recording performance and reproduction performance. Will be.
- the strength of the holder that holds the aperture 408 is also greatly reduced.
- the dimensions of the optical head also increase, making it impossible to achieve both reduction in size of the optical head and improvement in reproduction performance.
- it is necessary to increase the lateral magnification of the detection optical system so that stray light reflected from the other layers of the optical disk does not enter the sub-beam light receiving unit 411. It is necessary to reduce the size of the optical head in the height direction by reducing the size of the optical system for detecting the return path of the optical head and reducing the size of the optical element and the light receiving element.
- FIG. 35 illustrates the relationship between the magnification of the detection optical system and the interval between the main beam and the sub beam on the photodetector, and the relationship between the magnification of the detection optical system and the interval between the two sub beams on the photodetector. It is a figure for doing.
- Table 1 shows the relationship between the magnification of the detection optical system and the interval between the main beam and the sub beam on the photodetector, and the relationship between the magnification of the detection optical system and the interval between the two sub beams on the photodetector. It is a table.
- the lateral magnification of the detection optical system generally used in the conventional optical head is about 6 times, and assuming that the distance between the main beam and the sub beam on the optical disk is 20 ⁇ m, the main beam 412 and the sub beam on the photodetector 407 are assumed to be 20 ⁇ m.
- the distance X from 413 is 120 ⁇ m.
- the lateral magnification of the detection optical system is set to 14 to 16 times, the interval X between the main beam 412 and the sub beam 413 on the photodetector 407 increases to 280 ⁇ m to 320 ⁇ m, The size of the photodetector 407 increases.
- the 4-split light receiving unit 410 and the sub-beam light receiving unit 411 An arithmetic circuit is arranged between the two. In this case, the stray light reflected from the other layer stray light or the surface of the optical base is also irradiated to the arithmetic circuit.
- the focus error signal is calculated based on the following formula (1), and the tracking error signal is calculated based on the following formula (2).
- A1 to A4 represent the outputs of the respective light receiving regions of the four-divided light receiving unit 410, and B1 and B2 represent the sub beam light receiving unit 411 divided into two. It represents the output of each light receiving area, and k represents the gain.
- the light amount of the sub beam 413 is smaller than the light amount of the main beam 412, and the light amount of the sub beam 413 is about 1/10 of the light amount of the main beam 412. Therefore, correction is performed by multiplying the difference value of the output of each light receiving area of the sub beam light receiving unit 411 by the gain k.
- the gain k is a value of about 1 to 5.
- the tracking error signal largely fluctuates because the signal obtained from the sub-beam fluctuates due to interference. Therefore, it is essential to reduce the amount of incident stray light from the other layer to the sub-beam light receiving unit 411.
- the present invention has been made to solve the above-described problems, and can reduce the size of an optical head and improve the quality of a focus error signal, a tracking error signal, and a reproduction signal.
- the object is to provide an information device.
- An optical head is an optical head that reproduces information from an information recording medium having two or more recording layers, and includes a light source that emits a light beam and a light beam emitted from the light source.
- An objective lens that focuses light on a medium; an astigmatism generator that generates astigmatism in a reflected light beam reflected by the information recording medium; a light beam splitter that splits an incident light beam; and the astigmatism generator
- a photodetector that detects the reflected light flux in which astigmatism has occurred, the photodetector including a light receiving portion that receives the reflected light flux, and a package that covers the light receiving portion.
- a plurality of light guide portions that are formed on a light receiving surface of the light receiving portion on the light beam incident side and guide the reflected light flux to the light receiving portion, and a light shielding portion that shields light other than the plurality of light guide portions.
- the light source emits a light beam.
- the objective lens focuses the light beam emitted from the light source on the information recording medium.
- the astigmatism generation unit generates astigmatism in the reflected light beam reflected by the information recording medium.
- the light beam splitting unit splits one of the light beam emitted from the light source and the reflected light beam reflected by the information recording medium.
- the photodetector detects the reflected light beam in which astigmatism is generated by the astigmatism generator.
- the photodetector includes a light receiving unit that receives the reflected light flux and a package that covers the light receiving unit.
- the package is formed on the light receiving surface of the light receiving unit on the light beam incident side, and includes a plurality of light guiding units that guide the reflected light beam to the light receiving unit, and a light shielding unit that blocks light other than the plurality of light guiding units.
- the optical head since the light guide unit is formed on the light receiving surface of the light receiving unit on the light beam incident side, the optical head can be downsized as compared with the configuration including the aperture separately from the photodetector.
- a plurality of light guides are formed on the light receiving surface of the light receiving unit on the light beam incident side, stray light can be prevented from entering the light receiving unit, and a focus error signal, a tracking error signal, and a reproduction signal can be prevented. Quality can be improved.
- FIG. 1 It is a figure which shows the structure of the optical system of the optical head in Embodiment 1 of this invention.
- (A) is a figure which shows the bottom face of the photodetector in Embodiment 1 of this invention
- (B) is a figure which shows the side surface of the photodetector in Embodiment 1 of this invention
- (C) is a figure which shows the front of the photodetector in Embodiment 1 of this invention
- (D) is a figure which shows the structure remove
- (A) is a figure for demonstrating the surface reflection from the other layer in a 2 layer optical disk
- (B) is a figure for demonstrating the surface reflection from the other layer in a multilayer optical disk.
- (A) is a figure which shows the relationship between the distance of the main beam on the photodetector of the conventional optical head, and a sub beam, and other-layer stray light
- (B) is the optical of Embodiment 1 of this invention It is a figure which shows the relationship between the distance of the main beam on a photodetector of a head, and a sub beam, and other layer stray light.
- FIG. 16C is a view of the photodetector shown in FIG. 16B as viewed from above.
- FIG. 17 (A) is a front view which shows the structure of the photodetector in the 5th modification of Embodiment 1 of this invention
- (B) is a fragmentary sectional view of the photodetector shown in FIG. 17 (A).
- C) is a view of the photodetector shown in FIG. 17 (B) as viewed from above. It is a figure which shows the structure of the optical system of the optical head in Embodiment 2 of this invention. It is a figure which shows the structure of the hologram element shown in FIG. (A) is a side view which shows the structure of the photodetector in Embodiment 2 of this invention, (B) is a front view which shows the structure of the photodetector in Embodiment 2 of this invention.
- (A) is a front view showing the configuration of the photodetector according to Embodiment 4 of the present invention
- (B) is a sectional view taken along the line 26B-26B of the photodetector shown in FIG. 26 (A).
- FIG. 1 is a diagram showing the configuration of the optical system of the optical head according to Embodiment 1 of the present invention.
- the optical head 10 includes a semiconductor laser 101, a diffraction grating 102, a beam splitter 103, a collimator lens 104, an objective lens 105, an objective lens actuator 106, a cylindrical lens 108, and a photodetector 120.
- the semiconductor laser 101 emits a light beam.
- the light beam emitted from the semiconductor laser 101 as the light source is separated into a plurality of different light beams by the diffraction grating 102.
- the diffraction grating 102 splits the light beam emitted from the semiconductor laser 101.
- the diffraction grating 102 splits the light beam emitted from the semiconductor laser 101.
- the diffraction grating 102 divides the incident light beam into a main beam and first and second sub beams.
- the light beam transmitted through the diffraction grating 102 is reflected by the beam splitter 103, converted into a parallel light beam by the collimator lens 104, and enters the objective lens 105.
- the objective lens 105 focuses the light beam emitted from the semiconductor laser 101 on the optical disk 21.
- the light beam incident on the objective lens 105 becomes so-called three-beam convergent light and is applied to the optical disc 21.
- the objective lens 105 is driven in the optical axis direction (focus direction) and the tracking direction (radial direction) of the optical disk 21 by an objective lens actuator 106 (not shown in detail).
- the light beam reflected and diffracted by the recording layer of the optical disc 21 passes through the objective lens 105 and the collimator lens 104 again and enters the beam splitter 103.
- the light beam that has passed through the beam splitter 103 enters the cylindrical lens 108.
- the cylindrical lens 108 generates astigmatism in the reflected light beam reflected by the optical disk 21.
- the light beam that has passed through the cylindrical lens 108 enters the photodetector 120.
- the photodetector 120 detects a reflected light beam in which astigmatism is generated by the cylindrical lens 108.
- FIG. 2A to 2 (D) are a front view and a side view showing the configuration of the photodetector 120.
- FIG. 2A is a diagram showing a bottom surface of the photodetector in the first embodiment of the present invention
- FIG. 2B is a diagram showing a side surface of the photodetector in the first embodiment of the present invention.
- 2C is a diagram showing a front surface of the photodetector according to Embodiment 1 of the present invention
- FIG. 2D is a diagram illustrating the package 125 and the configuration of the photodetector in FIG. It is a figure which shows the structure except the adhesive agent 126.
- FIG. 1 is a diagram showing a bottom surface of the photodetector in the first embodiment of the present invention
- FIG. 2B is a diagram showing a side surface of the photodetector in the first embodiment of the present invention.
- 2C is a diagram showing a front surface of the photodetector according to Embodiment
- the photodetector 120 includes a light receiving unit 121, an arithmetic circuit 122, a terminal unit 123, and a package 125.
- the light receiving unit 121 receives the reflected light beam reflected by the optical disc 21.
- the arithmetic circuit 122 performs a predetermined operation on the electrical signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit 121.
- the package 125 covers the light receiving unit 121 and the arithmetic circuit 122.
- a light receiving portion 121, an arithmetic circuit 122, and a terminal portion 123 are formed on a substrate 127 made of a silicon wafer or the like, and a package 125 made of a resin such as silicone, glass, or metal is formed on the substrate 127 with an adhesive 126. Are pasted together.
- a light receiving portion 121 and an arithmetic circuit 122 are formed on the light incident side surface of the substrate 127, and a terminal portion 123 is formed on the surface facing the light incident side surface.
- the package 125 is formed on the light receiving surface of the light receiving unit 121 on the light beam incident side, and includes a plurality of light guiding units 124 that guide the reflected light beam to the light receiving unit 121 and a light shielding unit 114 that blocks light other than the plurality of light guiding units 124. Have.
- the terminal unit 123 is mounted on an FPC (flexible printed circuit board) 128 by soldering, and transmits a signal detected by the light receiving unit 121.
- the FPC 128 may be a circuit board.
- the light guide unit 124 is configured as an opening or a transmission unit in the package 125 and is accurately aligned with each light receiving region (not shown) of the light receiving unit 121.
- the package 125 is disposed on the incident light beam side.
- a shaded portion in FIG. 2C is a light shielding portion 114 that shields an incident light beam, and accurately blocks stray light from another layer different from the target recording layer. At this time, the transmittance of the light shielding portion 114 is desirably 10% or less.
- the light receiving unit 121 includes a plurality of light receiving regions, and the package 125 is formed with a light guide unit 124 for each light beam incident on each light receiving region of the light receiving unit 121.
- a light guide unit 124 may be provided on each light receiving region of the light receiving unit 121.
- a via hole is provided in the arithmetic circuit 122 formed of a laminated circuit, and the arithmetic circuit 122 and the terminal portion 123 provided on the bottom surface of the photodetector 120 are connected through the via hole.
- the terminal portion 123 may be connected to the arithmetic circuit 122 from the side surface of the photodetector 120 by wiring.
- the adhesive 126 may be applied to a region other than the light receiving unit 121 on the substrate 127, may be applied only to the four corners of the substrate 127, or may be applied to all surfaces on the upper surface of the substrate 127. .
- the material of the adhesive 126 is selected according to the balance between the transmittance due to the combination of the package 125, the light guide unit 124, and the adhesive 126 and the quality deterioration due to the light having a wavelength of 405 nm.
- FIG. 3 is a diagram illustrating the configuration of the light receiving unit 121 of the photodetector 120 and the configuration of the arithmetic circuit 122 according to the first embodiment of the present invention.
- the light receiving unit 121 includes a quadrant light receiving region 140, a first sub beam light receiving region 141a, and a second sub beam light receiving region 141b.
- the arithmetic circuit 122 includes first to seventh addition amplifiers 144a to 144g and first to fourth differential amplifiers 145a to 145d.
- the four-divided light receiving region 140 receives the main beam 142 out of the light flux that has passed through the cylindrical lens 108.
- the first differential amplifier 145a calculates the difference between the diagonal sum signals of the four-divided light receiving region 140, thereby detecting a so-called focus error signal.
- the first summing amplifier 144a detects the four-divided light receiving region 140.
- the RF signal is detected by calculating the sum of all signals.
- the second addition amplifier 144b and the third addition amplifier 144c each add a signal output from a region located diagonally to the four-divided light receiving region 140.
- the first differential amplifier 145a calculates a difference between the sum signal output from the second addition amplifier 144b and the sum signal output from the third addition amplifier 144c.
- the first addition amplifier 144a adds the sum signal output from the second addition amplifier 144b and the sum signal output from the third addition amplifier 144c.
- the first sub-beam light-receiving area 141a and the first sub-beam light-receiving area 141b of the photodetector 120 are focused and reflected on the track of the recording layer of the optical disc 21, and are reflected by the first sub-beam in the so-called three-beam method.
- 143a and the second sub beam 143b are received.
- the first sub-beam 143a and the second sub-beam 143b are received by the first sub-beam light receiving region 141a and the first sub-beam light receiving region 141b.
- the first sub-beam light receiving area 141a and the first sub-beam light receiving area 141b are each divided into two areas along the Y direction (direction perpendicular to the tracking direction).
- a push-pull signal calculated based on the main beam 142 received by the four-divided light receiving region 140 and a signal corresponding to the amount of light received by the first sub-beam light receiving region 141a and the first sub-beam light receiving region 141b are the sixth.
- the seventh addition amplifiers 144f and 144g and the second to fourth differential amplifiers 145b to 145d are generated, and tracking servo for causing the objective lens 105 to follow the track of the recording layer of the optical disc 21 is performed.
- the fourth addition amplifier 144d and the fifth addition amplifier 144e add signals output from areas adjacent to the X direction (tracking direction) of the four-divided light receiving area 140, respectively.
- the third differential amplifier 145c calculates a difference between the sum signal output from the fourth summing amplifier 144d and the sum signal output from the fifth summing amplifier 144e.
- the sixth addition amplifier 144f adds the signal output from the upper region of the first sub-beam light receiving region 141a and the signal output from the upper region of the second sub-beam light receiving region 141b.
- the seventh addition amplifier 144g adds the signal output from the area below the first sub-beam light receiving area 141a and the signal output from the area below the second sub-beam light receiving area 141b.
- the second differential amplifier 145b calculates a difference between the sum signal output from the sixth addition amplifier 144f and the sum signal output from the seventh addition amplifier 144g. Further, the fourth differential amplifier 145d calculates a difference between the differential signal output from the second differential amplifier 145b and the differential signal output from the third differential amplifier 145c.
- the objective lens 105 corresponds to an example of an objective lens
- the cylindrical lens 108 corresponds to an example of an astigmatism generation unit
- the diffraction grating 102 corresponds to an example of a light beam splitting unit
- the detector 120 corresponds to an example of a photodetector
- the light receiver 121 corresponds to an example of a light receiver
- the package 125 corresponds to an example of a package
- the plurality of light guides 124 correspond to an example of a plurality of light guides.
- the light shielding portion 114 corresponds to an example of a light shielding portion
- the quadrant light receiving region 140 corresponds to an example of a main beam light receiving portion
- the first sub beam light receiving region 141a corresponds to an example of a first sub beam light receiving portion
- the second sub-beam light receiving region 141b corresponds to an example of a second sub-beam light receiving unit.
- FIG. 4 is a diagram showing a configuration of a detection optical system including a cylindrical lens according to Embodiment 1 of the present invention.
- the cylindrical lens 108 has a cylindrical cylindrical surface 108a on the incident surface side of the light beam and a concave lens surface 108b having lens power on the exit surface side.
- the cylindrical surface 108a generates astigmatic differences with different focal positions at an angle of 90 degrees in a plane orthogonal to the optical axis.
- the direction of the cylindrical surface 108 a is arranged at an angle inclined by approximately 45 degrees with respect to the four-divided light receiving region 140 of the photodetector 120.
- FIG. 5 is a diagram showing the shape of the main beam on the quadrant light receiving area 140 at the front focal line, the rear focal line, and the focal position.
- the main beam 142a at the focal position has a circular shape
- the main beam 142b at the front focal line and the main beam 142c at the rear focal line have elliptical shapes orthogonal to each other.
- a light beam as shown in FIG. 5 is formed at the front focal line and the rear focal line.
- the light receiving unit 121 is arranged at the focal position in FIG.
- the lateral magnification ( ⁇ ) of the detection optical system is determined by the focal length of the objective lens 105, the focal length of the collimator lens 104, and the optical power of the concave lens surface 108b of the cylindrical lens 108.
- FIG. 6 is a cross-sectional view showing a partial configuration from the collimator lens 104 to the photodetector 120 of the optical head 10 according to Embodiment 1 of the present invention.
- the optical base 111 includes a semiconductor laser 101 (not shown), a diffraction grating 102 (not shown), a beam splitter 103, a collimator lens 104, an objective lens actuator 106 (not shown) for driving the objective lens 105, and a cylindrical lens 108. Hold.
- the photodetector 120 is fixed to the optical base 111 with an external jig (not shown).
- the photodetector 120 is configured to be adjustable on the optical base 111 in the Z direction (optical axis direction) and the XY plane (plane orthogonal to the optical axis).
- the position of the photodetector 120 on the XY plane is adjusted so that the main beam 142 incident on the quadrant light receiving region 140 of the photodetector 120 enters the approximate center of the quadrant light receiving region 140.
- the position in the Z direction is adjusted so that the light receiving unit 121 is arranged at the focal position of the astigmatic difference in a state where the objective lens 105 is focused on the recording layer of the optical disc 21.
- the main beam 142 incident on the four-divided light receiving region 140 becomes circular, and there is no offset in the focus error signal.
- the output of the focus error signal becomes 0 in a state where the objective lens 105 is focused on the recording layer of the optical disc 21. Further, rotation adjustment ( ⁇ Z) around the optical axis is performed so that the first sub-beam 143a and the second sub-beam 143b are incident on substantially the center of the first sub-beam light-receiving area 141a and the second sub-beam light-receiving area 141b. .
- the focus error signal balance is adjusted by adjusting the position of the XY plane, the tracking error signal is adjusted in detail by adjusting the rotation around the optical axis ( ⁇ Z), and the focus offset of the focus error signal is adjusted by adjusting the position in the Z direction. Adjustments are made.
- the first sub-beam 143a and the second sub-beam 143b are optically designed so as to be substantially incident on the first sub-beam light-receiving area 141a and the second sub-beam light-receiving area 141b. Further, by rotating and adjusting the entire photodetector 120 around the center of the optical axis so that the amplitude of the tracking error signal is maximized, the first sub-beam 143a, the second sub-beam 143b, and the first sub-beam light receiving region 141a are adjusted. And the fine adjustment of the positional relationship with the second sub-beam light receiving region 141b is performed.
- the RF signal is detected by adding all the light beams received by the four-divided light receiving region 140.
- the optical axis of the photodetector 120 is adjusted so that the main beam 142 enters the approximate center of the four-divided light receiving region 140 after holding the photodetector 120 with an external jig (not shown).
- the optical detector 120 is fixed to the optical base 111 in a positioned state. Reflected light from other layers becomes stray light and divergent light flux so that it does not enter the four-divided light receiving area 140, the first sub-beam light receiving area 141a, and the second sub-beam light receiving area 141b, and is reflected on the surface of the optical base 111.
- the light guide unit 124 has a small size as much as possible.
- the diameter or surface area of the light guide 124 is the diameter of the light beam passing through, the adjustment error when adjusting the optical axis of the photodetector 120, the relative positional deviation between the light guide 124 and the light receiver 121, and the light guide 124. It is a value that takes into account the dimensional tolerance of the.
- FIG. 7 is a diagram showing a configuration of the optical disc drive according to Embodiment 1 of the present invention.
- the optical disk drive 20 includes an optical head 10, a motor 203, a traverse 204, a control circuit 205, a signal processing circuit 206, and an input / output circuit 207.
- the optical disk drive 20 corresponds to an example of an optical information device.
- the optical disc 21 is fixed by being sandwiched between a clamper 201 and a turntable 202, and is rotated by a motor (rotating system) 203.
- the motor 203 rotates the optical disc 21.
- the optical head 10 is on a traverse (transfer system) 204.
- the traverse 204 moves the optical head 10 in the radial direction of the optical disc 21. Thereby, the irradiated light can be moved from the inner periphery to the outer periphery of the optical disc 21.
- the control circuit 205 controls the optical head 10 and the motor 203.
- the control circuit 205 performs focus control, tracking control, traverse control, rotation control of the motor 203, and the like based on the signal received from the optical head 10.
- the signal processing circuit 206 reproduces information from the reproduction signal (RF signal) and outputs the information to the input / output circuit 207 or sends the recording signal input from the input / output circuit 207 to the optical head 10 through the control circuit 205. To do.
- the optical disk drive 20 corresponds to an example of an optical information device
- the optical head 10 corresponds to an example of an optical head
- the motor 203 corresponds to an example of a drive unit
- the control circuit 205 corresponds to a control unit. It corresponds to an example.
- FIG. 8 is a diagram for explaining a method of fixing the photodetector 120 and the optical base 111. After the position adjustment of the XY plane of the photodetector 120, the position adjustment in the Z direction, and the rotation adjustment around the optical axis are performed and positioned by the external jig 138, the optical base 111 and the photodetector 120 are bonded. The adhesive 139 is adhesively fixed.
- FIG. 9A is a diagram for explaining surface reflection from another layer in the two-layer optical disc 21, and FIG. 9B is a diagram for explaining surface reflection from another layer in the multilayer optical disc 31.
- FIG. 9A shows the configuration of the optical disc 21 having two recording layers, and shows how stray light is generated from other layers when the convergent light 300 is condensed on a certain recording layer. In FIG. 9A, the light focused on the first recording layer L0 and the light reflected by the second recording layer L1 becomes the other layer stray light.
- FIG. 9B shows the configuration of the optical disc 31 having four recording layers, and shows how stray light is generated from other layers when the convergent light 300 is condensed on a certain recording layer.
- the light is focused on the third recording layer L2, and the light reflected by the first recording layer L0, the second recording layer L1, and the fourth recording layer L3 becomes the other layer stray light. .
- the layer interval d2 between the first recording layer L0 and the second recording layer L1 is defined as 25 ⁇ 5 ⁇ m in the standard, and is 20 ⁇ m at the minimum. The maximum is 30 ⁇ m. Therefore, the magnitude of the other layer stray light on the photodetector 120 is limited to some extent.
- the smallest layer interval d4min is likely to be smaller than that of the two-layer optical disc 21.
- the layer interval between the third recording layer L2 and the fourth recording layer L3 is the layer interval d4min.
- the farthest separated layer interval d4max is larger than that of the two-layer optical disc 21.
- the magnitude of the other-layer stray light in the photodetector 120 is significantly larger than that of the two-layer optical disk 21.
- the layer interval between the first recording layer L0 and the fourth recording layer L3 is the layer interval d4max.
- the detection optical system has a larger magnification (lateral magnification ⁇ ) to receive a four-divided light receiving region 140 that receives the main beam 142, and a first sub beam that receives the first sub beam 143a and the second sub beam 143b.
- the distance between the light receiving region 141a and the second sub-beam light receiving region 141b needs to be greatly separated.
- FIG. 10A is a diagram showing the relationship between the distance between the main beam and the sub beam on the photodetector of the conventional optical head and the stray light in the other layer
- FIG. 10B is a diagram illustrating the implementation of the present invention. It is a figure which shows the relationship between the distance of the main beam on a photodetector of the optical head of form 1, and a sub beam, and other layer stray light.
- the distance between the main beam 142 and the first sub beam 143a (or the second sub beam 143b) on the photodetector 120 is such that the main beam 142 and the first sub beam 143a (focused on the recording layer track of the optical disc 21).
- a value obtained by multiplying the distance from the second sub beam 143b) by the lateral magnification of the detection optical system is such that the main beam 142 and the first sub beam 143a (focused on the recording layer track of the optical disc 21.
- the main beam 142 and the first sub beam 143a on the photodetector 120 are used.
- the distance to (or the second sub beam 143b) is about 120 ⁇ m.
- the lateral magnification of the detection optical system is about 10 times in order to detect a stable tracking error signal. Necessary.
- the distance between the main beam 142 and the first sub beam 143a (or the second sub beam 143b) is about 200 ⁇ m.
- the interval between the main beam 142 and the first sub-beam 143a (or the second sub-beam 143b) on the track of the recording layer of the optical disc 21 is about 20 ⁇ m, but this value is from the inner periphery to the outer periphery of the optical disc 21. Since this affects the offset of the tracking error at the time of movement, the value is preset for each device, and generally 10 ⁇ m to 20 ⁇ m is selected.
- the detection optical system in order to realize the miniaturization of the optical head 10, it is necessary to reduce the size of the detection optical system, and it is necessary to reduce the size of the detection optical system in consideration of the influence of other layer stray light. In consideration of the adverse effect of other layer stray light, it is necessary to increase the magnification of the detection optical system.
- the detection optical system can be downsized with only the objective lens 105 and the collimator lens 104 while maintaining the lateral magnification. At this time, it is stricter from the viewpoint of space to configure the holder that holds the photodetector 120 or the aperture that blocks stray light incident on the light receiving unit 121 as a separate member.
- the quadrant light receiving region 140, the first sub beam receiving region 141a, and the first sub light receiving region 141a and the first sub beam receiving region 141a and the first sub beam receiving region 141b are prevented from being incident on the first sub beam receiving region 141a and the first sub beam receiving region 141b.
- the lateral magnification of the detection optical system composed of the objective lens 105, the collimator lens 104, and the concave lens of the cylindrical lens 108 should be in the range of about 14 to 16 times. Is desirable.
- a holder for holding the photodetector 120 and an aperture as another member for blocking stray light incident on the light receiving unit 121 Need to be abolished.
- a region of the light guide portion 124 through which the light beam is transmitted is indicated by a one-dot chain line.
- FIGS. 11 and 12 are cross-sectional views of substantially the center of the quadrant light receiving region 140, the first sub-beam light receiving region 141a, and the first sub-beam light receiving region 141b of the photodetector 120 in FIG. 10B.
- the light detector 120 shown in FIGS. 11 and 12 is provided with three light guides 124 separately.
- FIG. 11 is a cross-sectional view showing a configuration example of the light guide portion of the photodetector in the first embodiment of the present invention
- FIG. 12 shows the photodetector in the first modification of the first embodiment of the present invention. It is sectional drawing which shows the structural example of this light guide part.
- the package 125 is made of resin or metal, and the transmittance of the package 125 is 10% or less.
- the light guide 124 is formed in the package 125 by the opening 124a. Further, the package 125 other than the plurality of openings 124 a becomes the light shielding portion 114.
- the package 125 is made of transparent glass or resin, and the transmittance of the package 125 is 90% or more.
- the light guide part 124 and the light shield part 114 are formed by depositing a light shielding film 129 made of a metal film or an optical film.
- the transmittance of the light shielding film 129 is preferably 10% or less.
- any of the photodetectors 120 in FIGS. 11 and 12 has stray light reflected on the surface of the optical base 111 or the optical element (mainly incident light beam or divergent light beam). Can be cut off with high accuracy.
- FIGS. 13A and 13B are diagrams showing fluctuations in the level of the tracking error signal due to the difference in the magnification of the detection optical system and the configuration of the light guide unit 124 according to the conventional and the first embodiment.
- FIG. 13A is a diagram showing a waveform of a tracking error signal obtained by a conventional optical head
- FIG. 13B is a waveform of a tracking error signal obtained by the optical head in Embodiment 1 of the present invention.
- FIG. 13A is a diagram showing a waveform of a tracking error signal obtained by a conventional optical head
- FIG. 13B is a waveform of a tracking error signal obtained by the optical head in Embodiment 1 of the present invention.
- the first sub-beam 143a and the second sub-beam 143b interfere with the other layer stray light and the light guide portion 124 is not separated into three as shown in FIG.
- the tracking error signal fluctuates irregularly and greatly due to the influence of interference.
- the first sub-beam 143a and the second sub-beam 143b generally have a light amount of about 1/10 that of the main beam 142, so that the influence of interference increases.
- the lateral magnification of the detection optical system is increased to reduce the interference between the first sub-beam 143a and the second sub-beam 143b and the other layer stray light in the first sub-beam light receiving area 141a and the second sub-beam light receiving area 141b.
- the lateral magnification of the detection optical system is increased, and the light guide unit 124 is divided into the four-divided light receiving region 140, the first sub-beam light receiving region 141a, and the second.
- Each of the light receiving areas of the sub-beam light receiving area 141b is configured with high accuracy.
- interference between the first sub-beam 143a and the second sub-beam 143b and the stray light from the other layer is greatly reduced.
- FIG. 13B a stable tracking error signal with little signal level fluctuation can be obtained. Can be obtained.
- the photodetector 120 includes a silicon wafer and includes a light receiving unit 121, an arithmetic circuit 122, and a terminal unit 123 connected to the arithmetic circuit 122 by internal wiring such as a via hole or side wiring.
- a package 125 made of resin, glass, or metal having a light guide portion 124 in which an opening is formed is bonded to a substrate 127 with an adhesive 126 with high accuracy.
- FIG. 14A is a side view showing the configuration of the photodetector in the second modification of the first embodiment of the present invention
- FIG. 14B is the photodetector shown in FIG. It is the figure which looked at from the upper part.
- FIG. 15A is a side view showing the configuration of the photodetector in the third modification example of Embodiment 1 of the present invention
- FIG. 15B is the photodetector shown in FIG. It is the figure which looked at from the upper part.
- the package 125 is made of transparent resin or glass.
- the light guide portion 124 of the package 125 is formed by depositing an antireflection film 130 on the surface on the incident light beam side, not the opening.
- a light shielding film 129 made of a metal film or an optical film is formed in a region other than the light guide portion 124 (the hatched portion in FIG. 14B) on the surface of the package 125 on the incident light beam side.
- the transmittance of the light shielding film 129 is desirably 10% or less.
- the antireflection film 130 may be deposited only on the incident light flux side of the light guide portion 124 of the package 125.
- the adhesive 126 when the adhesive 126 is applied only to the periphery of the photodetector 120, the incident light flux side of the package 125 from the viewpoint of transmittance. It is better to deposit the antireflection film 130 on the surface facing the surface. It is desirable that the transmittance of the light guide unit 124 be 90% or more by depositing the antireflection film 130 on the surface of the package 125 facing the surface on the incident light beam side. With this configuration, since the light receiving unit 121 is hermetically sealed, dust or the like does not adhere to the light receiving unit 121, so that an optical head having excellent reliability can be realized. At this time, the antireflection film 130 is deposited only in the region of the light guide 124, but the antireflection film 130 may be omitted.
- the photodetector 120 includes a silicon wafer and includes a light receiving unit 121, an arithmetic circuit 122, and a terminal unit 123 connected to the arithmetic circuit 122 by internal wiring such as a via hole or side wiring.
- a package 125 made of resin, glass, or metal having a light guide portion 124 with an opening formed on a substrate 127 is bonded with an adhesive 126 with high accuracy.
- FIG. 16A to FIG. The configuration shown in FIG.
- FIG. 16A is a front view showing the configuration of the photodetector in the fourth modification example of Embodiment 1 of the present invention
- FIG. 16B is the photodetector shown in FIG.
- FIG. 16C is a view of the photodetector shown in FIG. 16B as viewed from above.
- FIG. 16A shows the photodetector 120 with the package 125 removed.
- the photodetector 120 includes a light receiving unit 121, an arithmetic circuit 122, and a pad unit 131.
- a light receiving unit 121, an arithmetic circuit 122, and a pad unit 131 are formed on the substrate 127.
- the pad portion 131 and the circuit board 132 provided below the substrate 127 are connected by wire bonding 133.
- a terminal portion 123 is formed on the circuit board 132 capable of pattern configuration, and the terminal portion 123 is mounted on the FPC 128.
- the light receiving unit 121, the arithmetic circuit 122, the pad unit 131, the wire bonding 133, and the circuit board 132 are covered with a package 125 made of resin.
- a package 125 made of resin.
- the package 125 has a plurality of openings 124a. As shown in FIG. 16C, the plurality of openings 124 a are accurately positioned with respect to each light receiving region of the light receiving unit 121. With this configuration, the size of the photodetector 120 is increased, but since the configuration is simple, it can be manufactured relatively easily and inexpensively.
- the terminal portion 123, the light guide portion 124, and the package 125 may be configured as shown in FIGS. 17 (A) to 17 (C).
- FIG. 17A is a front view showing the configuration of the photodetector in the fifth modification example of Embodiment 1 of the present invention
- FIG. 17B is the photodetector shown in FIG.
- FIG. 17C is a view of the photodetector shown in FIG. 17B as viewed from above.
- FIG. 17A shows the photodetector 120 with the package 125 and the resin frame 134 removed.
- the photodetector 120 includes a light receiving unit 121, an arithmetic circuit 122, and a pad unit 131.
- a light receiving unit 121, an arithmetic circuit 122, and a pad unit 131 are formed on the substrate 127.
- the pad portion 131 and the circuit substrate 132 provided below the substrate 127 are connected by wire bonding 133.
- a terminal portion 123 is formed on the circuit board 132 capable of pattern configuration, and the terminal portion 123 is mounted on the FPC 128.
- the light receiving unit 121, the arithmetic circuit 122, the pad unit 131, the wire bonding 133, and the circuit board 132 are formed inside a resin frame 134 formed by resin molding, and the resin frame 134 is covered with the package 125. That is, the resin frame 134 is formed along the outer peripheral portion of the circuit board 132, and the package 125 is formed on the upper side of the resin frame 134. Formed to seal.
- the package 125 is made of a metal such as aluminum or iron and has a plurality of openings 124a. As shown in FIG. 17C, the plurality of openings 124 a are accurately positioned with respect to each light receiving region of the light receiving unit 121.
- the package 125 can be made of metal, and the package 125 is not deteriorated even by a light beam having a wavelength of 405 nm. Therefore, the size of the photodetector 120 is increased, but light detection with excellent reliability is possible. A device 120 can be realized.
- the terminal portion 123 is a so-called BGA disposed on the bottom surface of the photodetector 120.
- BGA bottom surface of the photodetector 120.
- a terminal portion 123 may be disposed on the side surface of the photodetector 120 as shown in FIG.
- the light guide portion 124 has a circular shape, but stray light can be generated as much as possible. It is good also as non-circular so that it may interrupt
- the shape of the light guide 124 may be, for example, a non-circular shape such as a quadrangular shape, an elliptical shape, a triangular shape, or a fan shape shown in FIG.
- the oscillation wavelength of the semiconductor laser 101 serving as the light source can be applied to approximately 780 nm for CD, approximately 650 nm for DVD, and approximately 405 nm for BD.
- the first embodiment has a more remarkable effect when applied to an optical head having a large magnification of a detection optical system that records or reproduces information on a multilayer medium having three or more layers. It does not prevent application to an optical head, for example, an optical head having a low detection magnification, or an optical head that records or reproduces information on a single-layer or double-layer medium, and a photodetector as in the optical head of the first embodiment. It is possible to reduce the stray light incident on the light receiving part.
- the optical head in the second embodiment is different from the first embodiment in the tracking error signal detection method.
- the tracking error signal is detected by the so-called three-beam method using the diffraction grating 102.
- the so-called one-beam method (APP (advanced push-pull) method) using a hologram element is used. Tracking error signal is detected. Further, with the change of the tracking error signal detection method, the arrangement of the light receiving regions of the light receiving unit 121 and the arrangement of the plurality of light guide units 124 are different.
- FIG. 18 is a diagram showing the configuration of the optical system of the optical head according to Embodiment 2 of the present invention.
- the optical head 11 includes a semiconductor laser 101, a beam splitter 103, a collimator lens 104, an objective lens 105, an objective lens actuator 106, a cylindrical lens 108, a hologram element 150, and a photodetector 220.
- the semiconductor laser 101 emits a light beam having an oscillation wavelength of about 405 nm.
- the hologram element 150 is disposed between the beam splitter 103 and the cylindrical lens 108, and divides the beam into light beams for generating a tracking error signal by a so-called one beam method (APP method).
- the hologram element 150 is disposed between the objective lens 105 and the cylindrical lens 108 and divides the reflected light beam reflected by the optical disc 21.
- the light beam emitted from the semiconductor laser 101 is reflected by the beam splitter 103, converted into a parallel light beam by the collimator lens 104, and enters the objective lens 105.
- the objective lens 105 focuses the light beam emitted from the semiconductor laser 101 on the optical disk 21.
- the objective lens 105 is driven in the optical axis direction (focus direction) and the tracking direction (radial direction) of the optical disk 21 by an objective lens actuator 106 (not shown in detail).
- the light beam reflected and diffracted by the recording layer of the optical disc 21 passes through the objective lens 105 and the collimator lens 104 again and enters the beam splitter 103.
- the light beam that has passed through the beam splitter 103 is divided into a plurality of parts by the hologram element 150 and enters the cylindrical lens 108.
- the cylindrical lens 108 generates astigmatism in the reflected light beam reflected by the optical disk 21.
- the light beam that has passed through the cylindrical lens 108 enters the photodetector 120.
- the photodetector 120 detects a reflected light beam in which astigmatism is generated by the cylindrical lens 108.
- FIG. 19 is a diagram showing a configuration of the hologram element 150 shown in FIG.
- the solid line indicates the division pattern of the hologram element 150, and the broken line indicates the shape of the light beam passing through the hologram element 150.
- the hologram element 150 includes a main beam region 151 where a main beam is incident, and first and second APPs where interference light between ⁇ first order light and zeroth order light diffracted by the recording layer of the optical disc 21 (31) is incident. It includes main regions 152 and 153 and first and second APP sub-regions 154 and 155 in which only the 0th-order light is incident.
- FIG. 20A is a side view showing the configuration of the photodetector in the second embodiment of the present invention
- FIG. 20B is a front view showing the configuration of the photodetector in the second embodiment of the present invention.
- FIG. 20A and 20B show a relative positional relationship between the light receiving unit 221 of the photodetector 220 and the light guide unit 224 of the package 225.
- FIG. 20A and 20B show a relative positional relationship between the light receiving unit 221 of the photodetector 220 and the light guide unit 224 of the package 225.
- the light detector 220 includes a light receiving unit 221, an arithmetic circuit 222, a terminal unit 223, and a package 225.
- the light receiving unit 221 receives the reflected light beam reflected by the optical disc 21.
- the arithmetic circuit 222 performs a predetermined operation on the electrical signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit 221.
- the package 225 covers the light receiving unit 221 and the arithmetic circuit 222.
- the package 225 is formed on the light receiving surface of the light receiving unit 221 on the light beam incident side, and includes a plurality of light guiding units 224 that guide the reflected light beam to the light receiving unit 221 and a light shielding unit 214 that blocks light other than the plurality of light guiding units 224. Have.
- a light receiving portion 221, an arithmetic circuit 222, and a terminal portion 223 are formed on a substrate 227 made of a silicon wafer or the like, and a package 225 made of a resin such as silicone, glass, or metal is formed on the substrate 227 with an adhesive 226. Are pasted together.
- a light receiving portion 221 and an arithmetic circuit 222 are formed on the light incident side surface of the substrate 227, and a terminal portion 223 is formed on the surface facing the light incident side surface.
- the shape of the light guide 224 is indicated by a one-dot chain line, and the light-shielding part 214 that shields the incident light beam is indicated by oblique lines.
- the light shielding portion 214 preferably has a transmittance of 10% or less.
- the light receiving unit 221 includes a quadrant light receiving region 240, a first APP main beam light receiving region 156, a second APP main beam light receiving region 157, a first APP sub boom light receiving region 158, and a second APP sub boom light receiving region 159. .
- the light beam that has passed through each divided area of the hologram element 150 enters each light receiving area.
- the light beam (main beam 142) transmitted through the main beam region 151 is incident on the four-divided light receiving region 240.
- the light beam (APP main beam 165) transmitted through the first and second APP main regions 152 and 153 is incident on the first APP main beam light receiving region 156 and the second APP main beam light receiving region 157.
- the light flux (APP sub beam 166) transmitted through the first and second APP sub-regions 154 and 155 enters the first APP sub-boom light receiving region 158 and the second APP sub-boom light receiving region 159.
- the light receiving unit 221 includes a plurality of light receiving regions, and the light guides 224 are individually formed in the package 225 for the light beams incident on the light receiving regions of the light receiving unit 221.
- the light guides 224 are individually formed in the package 225 for the light beams incident on the light receiving regions of the light receiving unit 221.
- three light guide portions 224 corresponding to the main beam 142, the APP main beam 165, and the APP sub beam 166 are formed in the package 225.
- a light guide unit 224 may be provided in each light receiving region of the light receiving unit 221.
- the shapes of the plurality of light guides 224 are circular and elliptical.
- the shape of the light guide 224 corresponding to the quadrant light receiving region 240 is circular, and the shape of the light guide 224 corresponding to the first and second APP main beam light receiving regions 156 and 157 is elliptical.
- the shape of the light guide part 224 corresponding to the first and second APP sub-boom light receiving areas 158 and 159 is elliptical.
- the focus error signal is generated by calculating the differential of the diagonal sum signal of the quadrant light receiving area 240, and the RF signal is generated by calculating the sum of all the signals of the quadrant light receiving area 240. .
- a so-called push-pull signal is generated by obtaining a differential signal between the first and second APP main beam light receiving regions 156 and 157, and the generated push-pull signal and the first and second push-pull signals are generated.
- a tracking error signal in the so-called APP method is generated.
- FIG. 21 is a diagram for explaining a tracking error signal calculation method according to Embodiment 2 of the present invention.
- the tracking error signal is calculated based on the following equation (3).
- Tracking error signal (B1-B2) -k (B3-B4) (3)
- B1 represents the output of the first APP main beam light receiving region 156
- B2 represents the output of the second APP main beam light receiving region 157
- B3 represents the first
- the output of the APP sub-beam light receiving area 158 is represented
- B4 represents the output of the second APP sub-beam light receiving area 159
- k represents the gain.
- the gain k is usually set to 0.5 to 5.
- the tracking error signal becomes a servo signal that is not affected by interference from other layers of stray light, and an optical head having stable recording performance and reproduction performance is realized. it can.
- the plurality of light guides 224 have a circular shape and an elliptical shape.
- a non-circular shape such as a square shape, a triangular shape, or a fan shape may be used.
- the shapes of the plurality of light guides 224 may be all circular or different shapes.
- the adhesive 226 may be applied to all surfaces of the substrate 227, or may be applied only to the peripheral portion of the substrate 227.
- the material of the adhesive 226 is the same as in the first embodiment, the transmittance due to the combination of the configuration of the package 225, the light guide unit 224, and the adhesive 226, and the quality deterioration of the adhesive 226 with respect to light having a wavelength of 405 nm, It is selected according to the balance with the bonding strength.
- the objective lens 105 corresponds to an example of an objective lens
- the cylindrical lens 108 corresponds to an example of an astigmatism generation unit
- the hologram element 150 corresponds to an example of a light beam splitting unit
- light detection The detector 220 corresponds to an example of a photodetector
- the light receiving unit 221 corresponds to an example of a light receiving unit
- the package 225 corresponds to an example of a package
- the plurality of light guide units 224 correspond to an example of a plurality of light guide units.
- the light shielding portion 214 corresponds to an example of a light shielding portion
- the quadrant light receiving region 240 corresponds to an example of a main beam light receiving portion
- the first and second APP main beam light receiving regions 156 and 157 receive first sub beam light reception.
- the first and second APP sub-beam light receiving regions 158 and 159 correspond to an example of the second sub-beam light receiving unit.
- FIG. 22 is a cross-sectional view showing a configuration of the photodetector in the second embodiment of the present invention
- FIG. 23 is a cross-sectional view showing a configuration of the photodetector in the modification of the second embodiment of the present invention.
- . 22 and 23 show cross sections including the center of the four-divided light receiving region 240 and the centers of the first and second APP sub-beam light receiving regions 158 and 159.
- the light guide 224 is formed in the package 225 by depositing the antireflection film 230 on transparent glass or transparent resin as in the first embodiment.
- the light guide 224 may be formed in the package 225 by forming an opening in a metal or opaque resin.
- a light-shielding film (light-shielding part) 229 for shielding stray light is deposited in a region other than the light guide part 224 on the surface of the package 225.
- stray light may be shielded by the transmittance characteristics of the material constituting the package 225.
- the transmittance of the light shielding film 229 is desirably 10% or less.
- the light guide unit 224 has the antireflection film 230 only on the surface on the incident light beam side.
- the transmittance of the light guide unit 224 after the antireflection film is deposited is desirably 90% or more. If the transmittance is sacrificed, the antireflection film 230 deposited on the light guide unit 224 may be omitted.
- Embodiment 3 Next, an optical head according to Embodiment 3 of the present invention will be described.
- the optical head in Embodiment 3 all the arithmetic circuits are shielded from light.
- the configuration of the optical head in the third embodiment is the same as that of the optical head shown in FIG.
- FIG. 24A is a front view showing the configuration of the photodetector according to Embodiment 3 of the present invention
- FIG. 24B is a cross-sectional view of the photodetector shown in FIG. 24A taken along the line 24B-24B.
- FIG. 24A is a front view showing the configuration of the photodetector according to Embodiment 3 of the present invention
- FIG. 24B is a cross-sectional view of the photodetector shown in FIG. 24A taken along the line 24B-24B.
- the photodetector 320 includes a light receiving unit 221, an arithmetic circuit 222, a terminal unit 223, and a package 325.
- the light receiving unit 221 receives the reflected light beam reflected by the optical disc 31.
- the arithmetic circuit 222 performs a predetermined operation on the electrical signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit 221.
- the package 325 covers the light receiving unit 221 and the arithmetic circuit 222.
- a light receiving portion 221, an arithmetic circuit 222, and a terminal portion 223 are formed on a substrate 227 made of a silicon wafer or the like, and a package 325 made of a resin such as silicone, glass, or metal is formed on the substrate 227 with an adhesive 226. Are pasted together.
- a light receiving portion 221 and an arithmetic circuit 222 are formed on the light incident side surface of the substrate 227, and a terminal portion 223 is formed on the surface facing the light incident side surface.
- a plurality of light guides 324 are formed on the package 325 on the light receiving surface of the light receiving unit 221 on the light beam incident side.
- the shape of the light guide portion 324 is indicated by a one-dot chain line.
- the light receiving unit 221 includes a quadrant light receiving region 240, a first APP main beam light receiving region 156, a second APP main beam light receiving region 157, a first APP sub boom light receiving region 158, and a second APP sub boom light receiving region 159. .
- FIG. 24A is a view of the photodetector 320 as viewed from the incident light beam side.
- the other-layer stray light from the optical disc 31 has an elliptical shape depending on the amount of defocus in the recording layer of the optical disc 31.
- the other-layer stray light also enters the arithmetic circuit 322. At this time, when stray light is incident on the amplifier portion of the arithmetic circuit 322, noise is generated in the output signal, and an offset is generated in the focus error signal, tracking error signal, and RF signal, so that recording characteristics and reproduction characteristics are greatly deteriorated.
- the light shielding portion (light shielding film) 329 is deposited in a region other than the light guide portion 324 on the surface of the package 325 made of transparent glass or transparent resin. Is done. At this time, the transmittance of the light shielding portion 329 is desirably 10% or less. Further, the transmittance of the light guide unit 324 is desirably 90% or more. With this configuration, it can be seen that the other-layer stray light and the stray light are reflected on the surface of the light shielding portion 329 without entering the arithmetic circuit 322.
- a plurality of light guides 324 may be created by openings formed in the package 325.
- a plurality of light guide portions 324 may be created by not forming the light shielding portions 329 only in regions corresponding to the plurality of light guide portions 324.
- a plurality of light guides 324 may be created by forming an antireflection film only in a region corresponding to the plurality of light guides 324.
- the photodetector 320 corresponds to an example of a photodetector
- the light receiving unit 221 corresponds to an example of a light receiving unit
- the package 325 corresponds to an example of a package
- a plurality of light guide units 324 corresponds to an example of a plurality of light guide units
- the light shielding unit 329 corresponds to an example of a light shielding unit
- the quadrant light receiving region 240 corresponds to an example of a main beam light receiving unit
- the regions 156 and 157 correspond to an example of the first sub-beam light receiving unit
- the first and second APP sub-beam light receiving regions 158 and 159 correspond to an example of the second sub-beam light receiving unit
- the calculation circuit 322 includes the calculation unit. It corresponds to an example.
- FIG. 25 is a cross-sectional view showing the configuration of the photodetector in the modification of the third embodiment of the present invention.
- the light shielding portion 329 is formed on the incident light beam side of the package 325.
- a configuration in which a light shielding portion (aluminum reflective film or optical film) 329 serving as a reflective portion is deposited on the surface of the arithmetic circuit 222 may be employed. That is, the light shielding portion 329 may be formed between the adhesive 226 and the substrate 227 including the light receiving portion 221 and the arithmetic circuit 222.
- the transmittance of the light shielding portion 329 is desirably 10% or less, and the transmittance of the package 325 is desirably 90% or more.
- an antireflection film may be deposited on the surface of the package 325 on the incident light beam side and / or on the surface facing the incident light beam side surface.
- Embodiment 4 an optical head according to Embodiment 4 of the present invention will be described.
- the optical head in the fourth embodiment is different from the third embodiment in that at least one of a plurality of light guides is formed in the incident light beam side package of the arithmetic circuit.
- the configuration of the optical head in the fourth embodiment is the same as that of the optical head shown in FIG.
- FIG. 26A is a front view showing the configuration of the photodetector according to Embodiment 4 of the present invention
- FIG. 26B is a cross-sectional view taken along line 26B-26B of the photodetector shown in FIG. FIG.
- the photodetector 420 includes a light receiving unit 221, an arithmetic circuit 422, a terminal unit 223, and a package 425.
- the light receiving unit 221 receives the reflected light beam reflected by the optical disc 31.
- the arithmetic circuit 422 performs a predetermined calculation on the electrical signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit 221.
- the package 425 covers the light receiving unit 221 and the arithmetic circuit 422.
- the arithmetic circuit 422 includes a first arithmetic circuit 42 a that generates a focus error signal, a second arithmetic circuit 42 b that generates a tracking error signal, and a third arithmetic circuit 42 c that generates a reproduction signal of the optical disc 31. .
- a light receiving portion 221, an arithmetic circuit 422, and a terminal portion 223 are formed on a substrate 227 made of a silicon wafer or the like, and a package 425 made of a resin such as silicone, glass, or metal is formed on the substrate 227 with an adhesive 226. Are pasted together.
- a light receiving portion 221 and an arithmetic circuit 422 are formed on the light incident side surface of the substrate 227, and a terminal portion 223 is formed on the surface facing the light incident side surface.
- the light receiving unit 421 includes a four-divided light receiving region 240 that receives the main beam, first and second APP main beam light receiving regions 156 and 157 that receive the APP main beam 165, and an APP sub beam 166. And first and second APP sub-beam light receiving regions 158 and 159 for receiving light.
- the focus error signal is generated by calculating the differential of the diagonal sum signal of the quadrant light receiving area 240, and the RF signal is generated by calculating the sum of all the signals of the quadrant light receiving area 240. .
- a so-called push-pull signal is generated by obtaining a differential signal between the first and second APP main beam light receiving regions 156 and 157, and the generated push-pull signal and the first and second push-pull signals are generated.
- a tracking error signal in the so-called APP method is generated.
- output signals from the individual light receiving regions are input to the arithmetic circuit 422, and arithmetic processing is performed by the arithmetic circuit 422 configured by multilayer circuits such as an addition amplifier, a differential amplifier, and an amplification amplifier.
- the arithmetic circuit 422 calculates a signal corresponding to the light amount of the light beam received by the four-divided light receiving region 240, thereby generating a focus error signal, and the first and second APP main beam light reception.
- a second arithmetic circuit 42b that generates a tracking error signal by calculating signals corresponding to the light amounts of the light beams received in the regions 156 and 157 and the first and second APP sub-beam light receiving regions 158 and 159;
- the third arithmetic circuit 42c generates a reproduction signal of the recording layer of the optical disc 21 (31) using the output signal of the arithmetic circuit 42a and / or the second arithmetic circuit 42b.
- a plurality of light guides 424 are formed on the package 425 on the light receiving surface of the light receiving part 221 on the light beam incident side.
- a plurality of openings 424a are formed in the package 425 on the circuit surface on the light flux incident side of the third arithmetic circuit 42c. That is, the package 425 is formed on the light receiving surface of the light receiving unit 221 on the light beam incident side, and a plurality of light guiding units 424 that guide the reflected light beam to the light receiving unit 221 and a light shielding unit 329 that blocks light other than the plurality of light guiding units 424.
- an opening 424 formed on the circuit surface on the light beam incident side of the third arithmetic circuit 42c In FIG. 26A, the shapes of the light guide portion 424 and the opening portion 424a are indicated by alternate long and short dash lines.
- a light shielding portion 329 is provided on the surface of the arithmetic circuit 422.
- the light shielding portion 329 is made of a metal film such as aluminum.
- the f characteristic required when the reproduction signal is deteriorated by ⁇ 3 dB is 130 MHz or more. If there is a metal film on the amplifiers of the first arithmetic circuit 42a that generates the signal that is the source of the RF signal and the third arithmetic circuit 42c that performs the calculation of the RF signal, the influence of the load capacity of the metal film is very small. As a result, the f characteristic deteriorates to 100 MHz or less.
- an opening 424a is formed in a part of the surface of the amplifier of the first arithmetic circuit 42a and the third arithmetic circuit 42c related to the operation for generating the reproduction signal.
- the photodetector 420 corresponds to an example of a photodetector
- the light receiving unit 221 corresponds to an example of a light receiving unit
- the package 425 corresponds to an example of a package
- a plurality of light guide units 424 Corresponds to an example of a plurality of light guides
- the opening 424a corresponds to an example of an opening
- the light shielding part 329 corresponds to an example of a light shielding part
- the four-divided light receiving region 240 corresponds to an example of a main beam light receiving part.
- the first and second APP main beam light receiving areas 156 and 157 correspond to an example of the first sub beam light receiving part
- the first and second APP sub beam light receiving areas 158 and 159 correspond to the second sub beam light receiving part.
- the arithmetic circuit 422 corresponds to an example of an arithmetic unit
- the first arithmetic circuit 42a corresponds to an example of a first arithmetic circuit
- the second arithmetic circuit 42b corresponds to an example of a second arithmetic circuit.
- third operation Road 42c corresponds to an example of the third arithmetic circuit.
- the opening 424a is created by not forming the light shielding portion 329 only in the region corresponding to the opening 424a.
- the surface shape of the opening 424a formed on the circuit surface on the incident light beam side of the third arithmetic circuit 42c is a circular shape or a non-circular shape such as a rectangle, a sector, or a triangle. May be.
- a plurality of light guides 424 formed on the light receiving surface on the incident light beam side of the light receiving unit 221 and an opening 424a formed on the circuit surface on the incident light beam side of the arithmetic circuit 422 are made of different materials and It may be formed by a construction method.
- the plurality of light guides 424 formed on the light receiving surface on the incident light beam side of the light receiving unit 221 may be an optical film such as an antireflection film.
- the opening 424a corresponding to each of the first arithmetic circuit 42a and the third arithmetic circuit 42c is provided.
- the present invention is not particularly limited thereto, and the third arithmetic circuit 42a and the third arithmetic circuit 42c are not limited thereto.
- An opening 424a corresponding to only the circuit 42c may be provided.
- the package may have an opening on the circuit surface on the light beam incident side of the third arithmetic circuit.
- Embodiment 5 an optical head according to Embodiment 5 of the present invention will be described.
- the difference from Embodiments 1 to 4 is that not only a light source for BD that emits light having a wavelength of 405 nm, but also a light source for DVD that emits light having a wavelength of 650 nm, and light having a wavelength of 780 nm.
- emit is mounted, and it is the point made into the structure which can respond to multilayer BD, DVD, and CD.
- FIG. 27 is a diagram showing the configuration of the optical system of the optical head in the fifth embodiment of the present invention.
- the optical head 12 includes a diffraction grating 102, a beam splitter 103, a collimator lens 104, an objective lens 105, an objective lens actuator 106, a cylindrical lens 108, a hologram element 150, a flat plate beam splitter 170, a blue semiconductor laser 191, and a wavelength.
- a semiconductor laser 192 and a photodetector 520 are provided.
- Blue semiconductor laser 191 emits blue light having a wavelength of 405 nm.
- the two-wavelength semiconductor laser 192 emits red light having a wavelength of 650 nm and emits infrared light having a wavelength of 780 nm.
- the flat beam splitter 170 reflects red light or infrared light emitted from the two-wavelength semiconductor laser 192 toward the objective lens 105 and reflects light (blue light, red light or red light) reflected by the optical disc 21 (31). Infrared light) is transmitted.
- the photodetector 520 detects a reflected light beam in which astigmatism is generated by the cylindrical lens 108.
- FIG. 28 is a front view showing the configuration of the photodetector in the fifth embodiment of the present invention.
- the photodetector 520 includes a light receiving unit 521, an arithmetic circuit 522, and a terminal unit (not shown and package 525.
- the light receiving unit 521 receives a reflected light beam reflected by the optical disc 21 (31). A predetermined calculation is performed on the electrical signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit 521.
- the package 525 covers the light receiving unit 521 and the arithmetic circuit 522.
- a light receiving portion 521, an arithmetic circuit 522, and a terminal portion are formed on a substrate (not shown) formed of a silicon wafer or the like, and a package 525 formed of a resin such as silicone, glass, or metal is an adhesive on the substrate. 226 is pasted together.
- a light receiving portion 521 and an arithmetic circuit 522 are formed on the light incident side surface of the substrate, and a terminal portion is formed on the surface facing the light incident side surface.
- the package 525 is formed on the light receiving surface of the light receiving unit 521 on the light beam incident side, and includes a plurality of light guiding units 524 that guide the reflected light beam to the light receiving unit 521 and a light shielding unit 514 that blocks light other than the plurality of light guiding units 524.
- a shape of the opening 524 is indicated by a one-dot chain line, and the light shielding portion 514 is indicated by a diagonal line.
- the areas other than the light guide 524 are shielded by a light shielding film, resin or metal, and the light guide 524 transmits the incident light flux.
- the transmittance of the light shielding part 514 is desirably 10% or less, and the transmittance of the light guide part 524 is desirably 90% or more.
- the light receiving unit 521 includes a first four-divided light receiving region 180, a second four-divided light receiving region 161, a first APP main beam receiving region 156, a second APP main beam receiving region 157, and a first APP sub-beam receiving region. 158, a second APP sub-beam receiving area 159, a first sub-beam receiving area 160a, a second sub-beam receiving area 160b, a third sub-beam receiving area 162a, and a fourth sub-beam receiving area 162b.
- the first four-divided light receiving region 180 receives the blue main beam 142 having a wavelength of 405 nm and the red main beam 242 having a wavelength of 650 nm.
- the first and second APP main beam light receiving regions 156 and 157 receive the blue light APP main beam 165 having a wavelength of 405 nm.
- the first and second APP sub-beam light receiving regions 158 and 159 receive the blue light APP sub-beam 166 having a wavelength of 405 nm.
- the first sub-beam receiving region 160a receives a first sub-beam 243a of red light having a wavelength of 650 nm
- the second sub-beam receiving region 160b receives a second sub-beam 243b of red light having a wavelength of 650 nm.
- a focus error signal is detected based on the main beam 242
- a tracking error signal in the so-called three-beam method is detected based on the push-pull signal of the main beam 242 and the signals of the first sub beam 243a and the second sub beam 243b. Is done.
- the second quadrant light receiving region 161 receives an infrared main beam 342 having a wavelength of 780 nm.
- the third sub-beam receiving region 162a receives a first sub-beam 343a of infrared light having a wavelength of 780 nm
- the fourth sub-beam receiving region 162b receives a second sub-beam 343b of infrared light having a wavelength of 780 nm. Is received.
- a focus error signal is detected based on the main beam 342, and a tracking error signal in the so-called three-beam method is detected based on the push-pull signal of the main beam 342 and the signals of the first sub beam 343a and the second sub beam 343b. Is done.
- One light guide portion 524 that transmits a light beam incident on the region 162b is formed.
- one light guide 524 that transmits the light beam incident on the first and second APP main beam light receiving regions 156 and 157 is formed, and the light beam incident on the first and second APP sub beam light receiving regions 158 and 159.
- One light guide portion 524 that transmits light is formed.
- the light shielding part 514 is formed in a region excluding the light guide part 524.
- information can be recorded or reproduced on optical disks (BD, DVD and CD) corresponding to three different wavelengths, and not only single-layer and double-layer optical disks but also multilayer optical disks 31
- Information can be recorded or reproduced on the optical head, and an optical head having excellent recording characteristics and reproduction characteristics can be realized.
- the BD tracking error signal detection method in the fifth embodiment is a one-beam method (APP method), but may be a three-beam method.
- At least one of the plurality of light guides 524 may be formed on the circuit surface on the light beam incident side of the third arithmetic circuit.
- the shapes of the plurality of light guides 524 are the same as in Embodiments 2 to 4, and the method for forming the plurality of light guides 524 is also the same as in Embodiments 2 to 4.
- optical disk drive 20 shown in FIG. 7 may include the optical head according to any one of the second to fifth embodiments.
- An optical head is an optical head that reproduces information from an information recording medium having two or more recording layers, and includes a light source that emits a light beam and a light beam emitted from the light source.
- An objective lens that focuses light on a medium; an astigmatism generator that generates astigmatism in a reflected light beam reflected by the information recording medium; a light beam splitter that splits an incident light beam; and the astigmatism generator
- a photodetector that detects the reflected light flux in which astigmatism has occurred, the photodetector including a light receiving portion that receives the reflected light flux, and a package that covers the light receiving portion.
- a plurality of light guide portions that are formed on a light receiving surface of the light receiving portion on the light beam incident side and guide the reflected light flux to the light receiving portion, and a light shielding portion that shields light other than the plurality of light guide portions.
- the light source emits a light beam.
- the objective lens focuses the light beam emitted from the light source on the information recording medium.
- the astigmatism generation unit generates astigmatism in the reflected light beam reflected by the information recording medium.
- the light beam splitting unit splits one of the light beam emitted from the light source and the reflected light beam reflected by the information recording medium.
- the photodetector detects the reflected light beam in which astigmatism is generated by the astigmatism generator.
- the photodetector includes a light receiving unit that receives the reflected light flux and a package that covers the light receiving unit.
- the package is formed on the light receiving surface of the light receiving unit on the light beam incident side, and includes a plurality of light guiding units that guide the reflected light beam to the light receiving unit, and a light shielding unit that blocks light other than the plurality of light guiding units.
- the optical head can be downsized as compared with the configuration provided with the aperture separately from the photodetector.
- stray light can be prevented from entering the light receiving unit, and a focus error signal, a tracking error signal, and a reproduction signal can be prevented. Quality can be improved.
- the light beam dividing unit divides the incident light beam into a main beam and first and second sub beams, and the light receiving unit receives the main beam.
- a first sub-beam light-receiving unit that receives the first sub-beam, and a second sub-beam light-receiving unit that receives the second sub-beam, and the plurality of light guide units include the main beam light-receiving unit, It is preferable that the first sub-beam light receiving unit and the second sub-beam light receiving unit are individually formed on the light-receiving surfaces on the light beam incident side of the first sub-beam light receiving unit.
- the plurality of light guides are individually formed on the light receiving surfaces of the main beam receiving unit, the first sub beam receiving unit, and the second sub beam receiving unit on the light beam incident side. Can be greatly reduced. Further, since portions other than the plurality of light guide portions of the package can be reinforced, the strength of the package can be improved, the package size can be reduced, and the optical head can be further miniaturized. .
- a shape of the light guide portion is a circle. According to this configuration, since the shape of the light guide portion is circular, the shape of the light guide portion can be matched with the shape of the light beam incident on the light receiving portion, so that the light guide portion can be further reduced.
- the shape of the light guide is non-circular. According to this configuration, since the shape of the light guide unit is non-circular, the shape of the light guide unit can be matched with the shape of the light receiving unit, so that stray light incident on the light receiving unit can be further reduced.
- the package is preferably made of resin. According to this configuration, the optical head can be reduced in weight by configuring the package with resin, and a plurality of light guide portions can be easily formed in the package.
- the package is preferably made of silicone. According to this configuration, by configuring the package with silicone, it is possible to prevent deterioration of the package quality due to irradiation with blue light having a wavelength of, for example, 405 nm.
- the package is made of any one of resin, glass, and metal, and the plurality of light guides have openings formed in any of the resin, glass, and metal. It is preferable to include.
- a plurality of light guides can be easily formed by forming openings in a package made of any of resin, glass, and metal.
- the package is made of either resin or glass
- the light shielding portion is made of either a metal film or an optical film formed on the surface of either the resin or the glass. It is preferable to include.
- the light beam splitting unit is disposed between the objective lens and the astigmatism generating unit and splits the reflected light beam reflected by the information recording medium.
- the reflected light beam reflected by the information recording medium is divided by the light beam dividing unit disposed between the objective lens and the astigmatism generating unit, so-called APP (Advanced Push) is used.
- the tracking error signal can be detected by the pull method.
- the light beam splitting unit is disposed between the light source and the objective lens, and splits the light beam emitted from the light source.
- the tracking error signal is obtained by the three-beam method, so-called DPP (differential push-pull) method. Can be detected.
- the photodetector further includes a calculation unit that performs a predetermined calculation on an electric signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit, and the package includes: Preferably, the calculation unit is covered, and the light shielding unit blocks all light beams incident on the calculation unit.
- the calculation unit performs a predetermined calculation on the electrical signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit.
- the package covers the calculation unit.
- the light blocking unit blocks all light beams incident on the calculation unit. Therefore, stray light incident on the calculation unit can be completely blocked, noise generated when a light beam enters the calculation unit can be reduced, and a stable focus error signal, tracking error signal, and reproduction signal are generated. can do.
- the photodetector further includes a calculation unit that performs a predetermined calculation on an electric signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit
- the package includes: The arithmetic unit is covered, and the arithmetic unit generates a focus error signal, a second arithmetic circuit that generates a tracking error signal, and a third signal that generates a reproduction signal of the information recording medium.
- the package further includes an opening formed on a circuit surface on the light beam incident side of the third arithmetic circuit.
- the calculation unit performs a predetermined calculation on the electrical signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit.
- the package covers the calculation unit.
- the first arithmetic circuit generates a focus error signal
- the second arithmetic circuit generates a tracking error signal
- the third arithmetic circuit generates a reproduction signal of the information recording medium.
- the package further includes an opening formed on the circuit surface on the light beam incident side of the third arithmetic circuit.
- the opening is formed on the circuit surface on the light beam incidence side of the third arithmetic circuit that generates the reproduction signal, when the package arranged on the upper part of the arithmetic unit is formed of a metal film, the metal Due to the load capacity of the film, it is possible to prevent the f characteristic of the reproduction signal generated by the third arithmetic circuit from being lowered.
- the opening is preferably formed by a different material and method.
- the plurality of light guides formed on the light receiving surface of the light receiving unit on the light beam incident side and the opening formed on the circuit surface on the light beam incident side of the third arithmetic circuit are mutually connected. Since it is formed by different materials and construction methods, it is possible to form an optimum light guide portion and opening according to the purpose, and it is possible to reduce the size and increase the performance of the optical head.
- An optical head is an optical head for reproducing information from an information recording medium having two or more recording layers, the light source emitting a light beam, and the light beam emitted from the light source as the information.
- An objective lens for focusing on a recording medium; an astigmatism generating section for generating astigmatism in a reflected light flux reflected by the information recording medium; and the reflected light flux in which astigmatism is generated by the astigmatism generating section.
- a light detector that receives the reflected light beam, and a predetermined operation on an electrical signal obtained by photoelectrically converting the reflected light beam received by the light receiver.
- a package that covers the light receiving unit and the calculation unit, and the calculation unit includes a first calculation circuit that generates a focus error signal and a second calculation that generates a tracking error signal. And a third arithmetic circuit for generating a reproduction signal of the information recording medium, and the package includes an opening formed on a circuit surface on a light beam incident side of the third arithmetic circuit, and the opening And a light shielding part that shields light other than the part.
- the light source emits a light beam.
- the objective lens focuses the light beam emitted from the light source on the information recording medium.
- the astigmatism generation unit generates astigmatism in the reflected light beam reflected by the information recording medium.
- the photodetector detects the reflected light beam in which astigmatism is generated by the astigmatism generator.
- the photodetector covers a light receiving unit that receives a reflected light beam, a calculation unit that performs a predetermined calculation on an electrical signal obtained by photoelectrically converting the reflected light beam received by the light receiving unit, and a light receiving unit and a calculation unit.
- Package
- the calculation unit includes a first calculation circuit that generates a focus error signal, a second calculation circuit that generates a tracking error signal, and a third calculation circuit that generates a reproduction signal of the information recording medium.
- the package includes an opening formed on the circuit surface on the light flux incident side of the third arithmetic circuit, and a light shielding portion that shields light other than the opening.
- the opening is formed on the circuit surface on the light beam incidence side of the third arithmetic circuit that generates the reproduction signal, when the package arranged on the upper part of the arithmetic unit is formed of a metal film, the metal Due to the load capacity of the film, it is possible to prevent the f characteristic of the reproduction signal generated by the third arithmetic circuit from being lowered.
- An optical information device includes an optical head according to any one of the above, a drive unit for rotationally driving an information recording medium, and a control unit for controlling the optical head and the drive unit. Is provided. According to this configuration, the optical head described above can be applied to an optical information device.
- the optical head and the optical information apparatus according to the present invention have a stable tracking control function and a function capable of realizing a low information error rate, and realize recording and reproduction of information on a BD multilayer medium, and recording performance and reproduction. It is useful as an external storage device for computers with stable performance.
- the optical head and optical information apparatus according to the present invention can also be applied to a video recording apparatus such as an optical disk recorder or a video reproduction apparatus such as an optical disk player.
- the optical head and the optical information device according to the present invention can be applied to a car navigation system, a portable music player, a digital still camera, and a digital video camera.
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Abstract
Description
トラッキングエラー信号=(A3+A4)-(A1+A2)-k(B2-B1)・・・(2)
図1は、本発明の実施の形態1における光学ヘッドの光学系の構成を示す図である。
次に、本発明の実施の形態2における光学ヘッドについて説明する。
次に、本発明の実施の形態3における光学ヘッドについて説明する。実施の形態3における光学ヘッドでは、演算回路を全て遮光している。なお、実施の形態3における光学ヘッドの構成は、図18に示す光学ヘッドと同じである。
次に、本発明の実施の形態4における光学ヘッドについて説明する。実施の形態4における光学ヘッドが実施の形態3と異なる点は、演算回路の入射光束側のパッケージに複数の導光部のうちの少なくとも1つが形成される点である。なお、実施の形態4における光学ヘッドの構成は、図18に示す光学ヘッドと同じである。
次に、本発明の実施の形態5における光学ヘッドについて説明する。実施の形態1~4と異なる点は、405nmの波長を有する光を出射するBD用の光源だけでなく、650nmの波長を有する光を出射するDVD用の光源、及び780nmの波長を有する光を出射するCD用の光源を搭載し、多層BD、DVD及びCDに対応可能な構成とした点である。
Claims (15)
- 2層以上の記録層を有する情報記録媒体から情報を再生する光学ヘッドであって、
光束を出射する光源と、
前記光源から出射した光束を前記情報記録媒体に集光する対物レンズと、
前記情報記録媒体で反射された反射光束に非点収差を発生させる非点収差発生部と、
入射した光束を分割する光束分割部と、
前記非点収差発生部によって非点収差が発生した前記反射光束を検出する光検出器とを備え、
前記光検出器は、
前記反射光束を受光する受光部と、
前記受光部を被覆するパッケージとを含み、
前記パッケージは、前記受光部の光束入射側の受光面上に形成され、前記反射光束を前記受光部へ導く複数の導光部と、前記複数の導光部以外を遮光する遮光部とを有することを特徴とする光学ヘッド。 - 前記光束分割部は、入射した光束を、メインビームと、第1及び第2のサブビームとに分割し、
前記受光部は、前記メインビームを受光するメインビーム受光部と、前記第1のサブビームを受光する第1のサブビーム受光部と、前記第2のサブビームを受光する第2のサブビーム受光部とを含み、
前記複数の導光部は、前記メインビーム受光部、前記第1のサブビーム受光部及び前記第2のサブビーム受光部の光束入射側の受光面上にそれぞれ個別に形成されていることを特徴とする請求項1記載の光学ヘッド。 - 前記導光部の形状は、円形であることを特徴とする請求項1又は2記載の光学ヘッド。
- 前記導光部の形状は、非円形であることを特徴とする請求項1又は2記載の光学ヘッド。
- 前記パッケージは、樹脂により構成されていることを特徴とする請求項1~4のいずれかに記載の光学ヘッド。
- 前記パッケージは、シリコーンにより構成されていることを特徴とする請求項5記載の光学ヘッド。
- 前記パッケージは、樹脂、ガラス及び金属のいずれかにより構成され、
前記複数の導光部は、前記樹脂、前記ガラス及び前記金属のいずれかに形成された開口部を含むことを特徴とする請求項1~4のいずれかに記載の光学ヘッド。 - 前記パッケージは、樹脂及びガラスのいずれかにより構成され、
前記遮光部は、前記樹脂及び前記ガラスのいずれかの表面に形成された金属膜及び光学膜のいずれかを含むことを特徴とする請求項1~4のいずれかに記載の光学ヘッド。 - 前記光束分割部は、前記対物レンズと前記非点収差発生部との間に配置され、前記情報記録媒体で反射された反射光束を分割することを特徴とする請求項1~8のいずれかに記載の光学ヘッド。
- 前記光束分割部は、前記光源と前記対物レンズとの間に配置され、前記光源から出射した光束を分割することを特徴とする請求項1~8のいずれかに記載の光学ヘッド。
- 前記光検出器は、前記受光部で受光した前記反射光束を光電変換することにより得られた電気信号に所定の演算を施す演算部をさらに含み、
前記パッケージは、前記演算部を被覆し、
前記遮光部は、前記演算部に入射する光束をすべて遮光することを特徴とする請求項1~10のいずれかに記載の光学ヘッド。 - 前記光検出器は、前記受光部で受光した前記反射光束を光電変換することにより得られた電気信号に所定の演算を施す演算部をさらに含み、
前記パッケージは、前記演算部を被覆し、
前記演算部は、フォーカスエラー信号を生成する第1の演算回路と、トラッキングエラー信号を生成する第2の演算回路と、前記情報記録媒体の再生信号を生成する第3の演算回路とを含み、
前記パッケージは、前記第3の演算回路の光束入射側の回路面上に形成される開口部をさらに有することを特徴とする請求項1~10のいずれかに記載の光学ヘッド。 - 前記受光部の光束入射側の受光面上に形成された前記複数の導光部と、前記第3の演算回路の光束入射側の回路面上に形成された前記開口部とは、互いに異なる材料及び工法により形成されることを特徴とする請求項12記載の光学ヘッド。
- 2層以上の記録層を有する情報記録媒体から情報を再生する光学ヘッドであって、
光束を出射する光源と、
前記光源から出射した光束を前記情報記録媒体に集光する対物レンズと、
前記情報記録媒体で反射された反射光束に非点収差を発生させる非点収差発生部と、
前記非点収差発生部によって非点収差が発生した前記反射光束を検出する光検出器とを備え、
前記光検出器は、
前記反射光束を受光する受光部と、
前記受光部で受光した前記反射光束を光電変換することにより得られた電気信号に所定の演算を施す演算部と、
前記受光部及び前記演算部を被覆するパッケージとを含み、
前記演算部は、フォーカスエラー信号を生成する第1の演算回路と、トラッキングエラー信号を生成する第2の演算回路と、前記情報記録媒体の再生信号を生成する第3の演算回路とを含み、
前記パッケージは、前記第3の演算回路の光束入射側の回路面上に形成された開口部と、前記開口部以外を遮光する遮光部とを有することを特徴とする光学ヘッド。 - 請求項1~14のいずれかに記載の光学ヘッドと、
情報記録媒体を回転駆動するための駆動部と、
前記光学ヘッド及び前記駆動部を制御する制御部とを備えることを特徴とする光情報装置。
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