WO1993009535A1 - Mecanisme de detection de focalisation et tete optique et memoire optique l'utilisant - Google Patents

Mecanisme de detection de focalisation et tete optique et memoire optique l'utilisant Download PDF

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Publication number
WO1993009535A1
WO1993009535A1 PCT/JP1992/001441 JP9201441W WO9309535A1 WO 1993009535 A1 WO1993009535 A1 WO 1993009535A1 JP 9201441 W JP9201441 W JP 9201441W WO 9309535 A1 WO9309535 A1 WO 9309535A1
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WO
WIPO (PCT)
Prior art keywords
light
detection
optical
optical system
hologram element
Prior art date
Application number
PCT/JP1992/001441
Other languages
English (en)
Japanese (ja)
Inventor
Fumio Koyama
Masatoshi Yonekubo
Takashi Takeda
Toshio Arimura
Hidefumi Sakata
Osamu Yokoyama
Original Assignee
Seiko Epson Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Seiko Epson Corporation filed Critical Seiko Epson Corporation
Priority to JP05508321A priority Critical patent/JP3132001B2/ja
Priority to KR1019930702028A priority patent/KR100191884B1/ko
Publication of WO1993009535A1 publication Critical patent/WO1993009535A1/fr

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Classifications

    • 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
    • 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
    • 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
    • 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
    • G11B7/123—Integrated head arrangements, e.g. with source and detectors mounted on the same substrate
    • 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
    • G11B7/1353—Diffractive elements, e.g. holograms or gratings
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
    • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
    • G11B11/10532—Heads
    • G11B11/10541—Heads for reproducing
    • G11B11/10543—Heads for reproducing using optical beam of radiation
    • 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
    • G11B7/0912—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 push-pull method
    • 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
    • G11B7/0916—Foucault or knife-edge methods

Definitions

  • the present invention relates to a focus detection mechanism that detects the focus of a light beam on a target surface and is suitable for use in an optical storage device and the like, and an optical head and an optical storage device using the same.
  • optical storage devices that form / detect minute bits, it is essential to converge the luminous flux from the light-emitting source to an extremely small light spot on the target surface. To achieve this, focus detection using reflected light from the target surface is generally required.However, in order to reduce the size of the optical storage device, it can be efficiently mounted on an optical head and has high performance. There is a long-awaited need to achieve this, and various systems using hologram elements and the like have been proposed.
  • Fig. 31 uses a linear diffraction grating 5 engraved at unequal intervals, enabling focus detection and the reproduction signal essential for optical storage devices. And various error signals can be obtained relatively easily, so it is regarded as an effective method.
  • the target surface reflected light that has been converted into a substantially parallel light beam by the objective lens 6 is split by the unequally spaced diffraction grating 5 into a first-order light and a first-order earth diffracted light.
  • the ruled line interval of the diffraction grating 5 is appropriately determined.-The primary light 7 is converged only in the grating arrangement direction (y), and the simultaneously generated + primary light 8 is diverged only in the y direction. ing. These luminous fluxes are converged by the collimating lens 9 arranged in this order. At this time, the diffracted lights 7 and 8 are located before the focal plane 9 f of the collimating lens 9 in the y direction.
  • the light In the notch direction (X), which converges backward and is not affected by the diffraction grating 5, the light converges to the original focal point 9 f of the collimator lens 9, resulting in the focal point of the collimator lens 9. It becomes a non-point convergent light beam that forms a circle of least confusion before and behind the point plane 9f.
  • the target surface reflected light that has exited the objective lens 6 deviates from the parallel light beam at the time of focusing and converges or diverges, and the light beam focus position moves back and forth.
  • the light is projected onto the two photoelectric conversion elements 10 and 11 that are placed in steps at the position of the circle of least confusion of ⁇ 1st order light.
  • the shape of the light spot changes complementarily from the vertical camellia circle to the horizontal camellia circle, and a focusing error signal is obtained as differential output by the elements 10 and 11 having a light-receiving surface with an intricate shape. ing.
  • the method of using the deformation of the astigmatism spot for focus detection has twice the sensitivity than the so-called spot size method that simply detects spot blur without using the astigmatism, and also uses a detector. It is superior to the so-called knife-edge method in that it must exactly match the conjugate position of the target surface during focusing, because manufacturing tolerances can be greatly reduced.Excellent focusing using astigmatic spots There is a need for a detection method.
  • An object of the present invention to solve the above-mentioned problems, to enable a flat detector to be placed in the same plane, to enable good focus detection while being easy to manufacture, and to perform focus detection without any trouble even when the wavelength of a light source fluctuates.
  • An object of the present invention is to provide a mechanism and an optical head and an optical storage device using the same. Disclosure of the invention
  • a detection optical system that converges reflected light from a focus target surface
  • a pair of light detection means arranged on the same plane that is substantially conjugate with the target surface with respect to the detection optical system
  • a longitudinal direction of the light detecting means is arranged substantially along a diffraction direction by the hologram element
  • the hologram element has an in-phase and periodic light modulation rate pattern substantially along a hyperbolic group or a corrected hyperbolic group,
  • a pair of astigmatic II folded light beams whose HI-folded beam cross-sectional shape changes complementarily by the hologram element are detected by the pair of light detecting means,
  • —Focusing on the target surface is detected by calculating a difference between outputs of the pair of light detecting means.
  • a detection optical system that converges reflected light from a focus target surface
  • a pair of light detection means disposed on the same plane that is substantially conjugate with the target surface with respect to the detection optical system
  • a longitudinal direction of the light detecting means is arranged substantially along a diffraction direction by the hologram element
  • the hologram element is divided into two or more regions, and each of the divided regions has an in-phase and periodic light modulation rate pattern substantially along a hyperbolic group or a corrected hyperbolic group,
  • the astigmatic diffracted light beams diffracted by different regions of the hologram element are separated from each other,
  • a pair of astigmatic diffracted light beams which are diffracted by different regions of the hologram element and whose beam cross-sectional shapes change complementarily, are detected by the pair of light detecting means;
  • a focus on the target surface is detected by calculating a difference between outputs of the pair of light detection means.
  • a detection optical system that converges the reflected light of the reproduction or recording light beam from the optical storage medium surface
  • a pair of light detection means groups arranged on the same plane that is substantially conjugate with the target surface with respect to the detection optical system
  • Each of the pair of light detection means groups comprises two light detection means, and the longitudinal direction of the light detection means is arranged substantially along the direction of diffraction by the hologram element;
  • the hologram element is divided into two by a dividing line corresponding to the tangent and tangential directions of the surface of the optical recording medium, and the divided areas are substantially in-phase with each other in a hyperbolic group or a corrected hyperbolic group. And having a periodic light modulation rate pattern,
  • the astigmatic diffracted light beams diffracted by different regions of the hologram element are separated from each other,
  • the beam cross-sectional shape changes with the same tendency,
  • a light beam group composed of the two astigmatism light beams is defined as an astigmatism light beam group
  • a pair of astigmatism light beams whose beam cross-sectional shape changes complementarily is detected by the pair of light detection means groups.
  • the two astigmatic diffracted light beams diffracted from the same area of the hologram element are detected by the light detecting means to obtain a total output, and a difference between the two total outputs is calculated to detect a tracking error of the light beam. It is characterized by doing.
  • a detection optical system for collecting reflected light of a reproduction or recording light beam from the optical storage medium surface
  • a pair of light detection means disposed on the same plane that is substantially conjugate with the target surface with respect to the detection optical system
  • the longitudinal direction of the light detection means is placed substantially along the direction of diffraction by the hologram element
  • the hologram element is divided into two by a dividing line corresponding to the track tangential direction of the optical storage medium surface, and the in-phase and period are substantially along the hyperbolic group or the hyperbolic group captured in each of the divided areas. It has a typical light modulation rate pattern and is blazed ::
  • the astigmatic diffracted light beams folded by different regions of the hologram element are separated from each other,
  • a pair of the astigmatic diffracted light beams diffracted by different regions of the hologram element and having a beam cross-sectional shape that changes complementarily are detected by a pair of the light detection means, and the light detection means is a long light detection element. And another light detection element surrounding at least one of the light detection elements,
  • An output difference between the output of the long light detection element and the output of the another light detection element surrounding at least a part of the long light detection element is calculated, and a difference between the pair of the output differences is calculated.
  • a light head characterized in that a tracking error is detected by calculating a difference between outputs of the pair of long light detecting means. Further, in the optical storage device according to the present invention, the light for irradiating the reproduction or recording beam onto the optical storage medium is focused based on a source and a focus detection result of the light head. Focusing means for performing tracking adjustment, and tracking means for performing tracking adjustment based on the detection result of the tracking error of the optical head.
  • FIG. 1 to 30 show an embodiment of a focus detection mechanism and an optical head and an optical storage device according to the present invention.
  • FIG. 1 is a schematic diagram of a hologram pattern suitable for use in the present invention.
  • FIG. 2 is an explanatory diagram showing a state of diffraction by a hologram, and
  • FIG. 3 is another explanatory diagram showing details of diffraction by a hologram.
  • FIG. 4 is a main cross-sectional view of the focus detection mechanism according to the first embodiment of the present invention.
  • FIG. 5 is an explanatory diagram of a photoelectric conversion element in the focus detection mechanism of the first embodiment.
  • FIG. 6 is an explanatory diagram of the operation of the focus detection mechanism of the first embodiment.
  • FIG. 1 is a schematic diagram of a hologram pattern suitable for use in the present invention.
  • FIG. 2 is an explanatory diagram showing a state of diffraction by a hologram
  • FIG. 3 is another explanatory diagram showing details of
  • FIG. 7 is a graph of a forcing single error signal by the focus detection mechanism of the first embodiment.
  • FIG. 8 is a front view of a photoelectric conversion element having another configuration in the focus detection mechanism of the first embodiment.
  • FIG. 9 is an explanatory diagram of a hologram element of an optical head according to a second embodiment of the present invention.
  • FIG. 10 is a cross-sectional view of the optical head of the second embodiment. 1 is a front view of the photoelectric conversion element of the optical head of the second embodiment,
  • FIG. 12 is a perspective view of a main part of the optical head of the second embodiment, and
  • FIG. FIG. 14 is a perspective view of a main part showing another configuration example of the optical head of the second embodiment.
  • FIG. 14 is a perspective view of a main part showing still another configuration example of the optical head of the second embodiment. is there.
  • FIG. 15 is a front view of the photoelectric conversion element of the optical head according to the second embodiment of the present invention.
  • FIG. 16 is an explanatory diagram of the hologram element of the optical head according to the fourth embodiment of the present invention.
  • FIG. 17 is a front view of the photoelectric conversion element in the optical head of the fourth embodiment. It is a figure.
  • FIG. 18 is a main cross-sectional view of a focus detection mechanism showing a fifth embodiment of the present invention.
  • FIG. 19 is an essential sectional view of an optical head showing a sixth embodiment of the present invention.
  • FIG. 20 is a schematic sectional view of a hologram element used for the optical head of the sixth embodiment.
  • FIG. 21 is a front view of the photoelectric conversion element in the optical head of the sixth embodiment.
  • FIG. 22 is a main cross-sectional view of a focus detection mechanism according to a seventh embodiment of the present invention.
  • FIG. 23 is a cross-sectional view of a focus detection mechanism according to another configuration of the seventh embodiment.
  • FIG. Figure 24 shows the book
  • FIG. 25 is a main cross-sectional view of an optical head according to an eighth embodiment of the present invention.
  • FIG. 25 is a front view of a photoelectric conversion element in the optical head according to the eighth embodiment, and FIG. It is a principal sectional view of the optical head which shows the other structure of an Example.
  • FIG. 27 is a main cross-sectional view of the optical head according to the ninth embodiment of the present invention.
  • FIG. 28 is a main cross-sectional view of a focus detection mechanism according to a tenth embodiment of the present invention
  • FIG. 29 is a main cross-sectional view of a focus detection mechanism showing another configuration of the tenth embodiment. is there.
  • FIG. 30 is a front view of an optical head photoelectric conversion element according to an i-th embodiment of the present invention.
  • FIG. 31 is a main cross-sectional view of a conventional focus detection mechanism using a diffraction grating
  • FIG. 32 is a perspective view of a main part of a conventional optical head using a diffraction grating.
  • FIGS. 1 to 8 show a first embodiment according to the present invention.
  • FIG. 1 is an explanatory view of a hologram 15 suitable for use in the focus detection mechanism of the present invention.
  • the pattern 15 p formed on the glass substrate 15 b is represented by an equation expressed by rectangular coordinates (X, y) on the substrate plane, where c is a constant.
  • hyperbolic patterns 15 p are calculated using the constants f and L
  • a general synthetic hologram is used in which a photosensitive agent applied on a glass substrate 15b is exposed through a mask having a desired pattern, and the glass substrate 15b is etched after development. Can be applied in the same way.
  • FIG. 2 (a) and 2 (b) are explanatory views showing the state of diffraction by the hologram 15.
  • FIG. 2 (a) when the parallel light 16 is vertically incident on the hologram 15 described above, the light beam incident on the point (x, y) becomes the pattern 15p of this part. It will be diffracted in the arrangement direction.
  • Fig. 2 (b) the slope of the tangent of the hyperbola at (X, y) is
  • the pattern 15 P When the pattern 15 P completely complies with the hyperbolic equation, it is inevitable that aberrations due to deviation from paraxial appear. This aberration is not a problem for practical use, but in order to correct it, a correction term that is close to the equation may be added, the amplitude and phase modulation rate may be adjusted, or the substrate 15b may be curved. Also in this case, the necessary correction is slight, and the pattern for realizing the above does not substantially change from the hyperbola.
  • the parallel light 16 incident on the hologram surface has a finite diameter, the range of the emitted light can be limited. For example, as shown in Fig.
  • 2 0 B is two line segments of 2 a ⁇ X ⁇ 2 a on the X axis and 2 b-2 a ⁇ y ⁇ 2 b + 2 a on the y axis,
  • the hologram element does not necessarily need to include the origin (0, 0) of the hyperbola within the substrate area, and uses only a part of the extraneous pattern corresponding to the incident range of the finite phantom beam to separate the beam. .
  • the amplitude and the phase light modulation rate during one period are appropriately determined to increase or decrease the amount of diffracted light of a specific order, It is also possible to obtain an appropriate hologram element according to the application, for example, by changing the light distribution.
  • the blaze angle is selected, for example, the relative intensity of the + 1st-order light and the 0th-order light can be appropriately determined.
  • the absolute value of the focus distance that appears before and after in the x and y directions can also be changed. For example
  • the diffracted light that converges in the main diffraction direction and diverges in a direction perpendicular to the main diffraction direction is referred to as primary first-order light, and conversely, diverges in the generated diffraction direction.
  • the diffracted light converging in the direction perpendicular to this is called + 1st-order light, and the two are distinguished.
  • FIG. 4 is a layout diagram showing a configuration example of a focus detection mechanism using a hologram element as described above.
  • the divergent light from the semiconductor laser 21 is converted into a parallel light by the collimator lens 22 and reaches the hologram element 23 disposed immediately thereafter.
  • the hologram element 23 has a hyperbolic pattern having the asymptote of the above-mentioned inclination ⁇ 1, and the position where the incident optical axis is displaced in the y direction from the origin of the group of hyperbolas as shown in FIG. Off-axis pattern that passes through.
  • both the first-order diffracted light and the first-order diffracted light are dispersed from the optical axis, and only the straight-order 0th-order light passes through the objective lens 24 arranged at an appropriate distance and passes through the recording Z reproduction beam converging on the optical recording medium surface 25. Has formed.
  • the reflected light from the medium surface 25 of the incident beam is diverged, travels backward, is converted into a substantially parallel light beam by the objective lens 24, and is diffracted again to the hologram element 23.
  • the collimating lens 22 is disposed immediately after the hologram element 23, and in this case, the soil first-order diffracted lights 26 and 27 are also converged by the collimating lens 22.
  • the long side extends along the radiation direction from the optical axis 28 as shown in Fig. 5 on the focal plane 22f of the collimator lens 22.
  • rectangular photoelectric conversion elements 29 and 30 are provided.
  • the luminous flux of the focal length soil f incident on the collimator lens 22 will be the focal length of the collimator lens 22 Than F Therefore, the first-order diffracted light 26 incident on the collimate lens while diverging in the e direction and converging at + f in the y direction while diverging in the e direction is:
  • a focal line is connected behind by ⁇ , and a focal line is connected just before or in the y direction.
  • the + 1st-order diffracted light 27 forms a focal line slightly forward in the X direction and a focal line slightly backward in the y direction, and the diffracted lights 26, 27 Both are astigmatic convergence beams that connect the circle of least confusion on the same plane near the focal plane 22 f of the collimator lens 22.
  • the diffracted lights 26, 27 are astigmatic convergence beams that connect the circle of least confusion on the same plane near the focal plane 22 f of the collimator lens 22.
  • the diffraction angle of the ⁇ first-order zero-fold light 26, 27 changes with the wavelength fluctuation, and the incident position on the photoelectric conversion elements 29, 30 moves in the radiation direction accordingly. Since the transducers 29 and 30 are long in the radial direction, this movement does not affect the output.
  • the reflected light passing through the objective lens 24 deviates from the parallel light beam at the time of focusing and converges or diverges. That is, when the medium surface 25 is closer to the focal point of the objective lens 24, the light beam diverges, and when it is farther away, the light beam converges conversely. Therefore, when the medium 25 is near, the light beam is collected rearward when the collimator lens 22 is in the image plane, and moves toward the near side when the medium 25 is far. As a result, as shown in FIG. 6, the shapes of the light spots 31 and 32 projected on the rectangular photoelectric conversion elements 29 and 30 are as shown in FIG. 6A when the medium 25 is close.
  • the primary spot 31 is a vertical ellipse and the primary spot 32 is a horizontal ellipse.
  • the circle of least confusion as shown in (b).
  • the medium 25 is far away, as in (C).
  • Primary boss 3 1 is a horizontally long ellipse and + primary boss 32 is a vertically long ellipse.
  • the long-elliptical slot whose major axis coincides with the long side of the photoelectric conversion elements 29 and 30 has a larger photoelectric conversion output, so the photoelectric conversion element 29 on the-primary side and the photoelectric conversion of the + 1st order If the output of the element 30 is differentiated, a focusing error signal S as shown in FIG. 7 is obtained.
  • a difference signal between the obtained error signal and the control target value is obtained, and if necessary, an appropriate order of complementarity is added to the difference signal to obtain a drive signal for the actuator.
  • the two photoelectric conversion elements 29 and 30 for obtaining the differential output can be placed in the same plane, and the step size is strictly controlled. There is no need for this, and the manufacture of devices is greatly facilitated, especially for composite devices incorporated in the same package as the semiconductor laser.
  • the change in the diffraction angle is compensated for by the long photoelectric conversion elements 29 and 30 with respect to the wavelength fluctuation, and the focal line positions are moved back and forth by the same amount, so that the center of the differential is not shifted. Even when a light source such as a semiconductor laser whose emission wavelength is liable to change is used, the advantages of the hologram can be fully utilized.
  • the output difference between the case where the medium is near and the case where the medium is far can be increased and decreased, and the width of the short side is small.
  • the output becomes smaller when the light spots 31 and 32 become horizontally elliptical.
  • the shape of the photoelectric conversion elements 29 and 30 is not limited to a rectangle, but may be an ellipse as long as it is long.
  • the shape of the photoelectric conversion elements 29 and 30 may be rectangular or the like, or, for example, a mask may be provided on the front surface of the photoelectric conversion element to limit the light receiving region to an appropriate shape.
  • a splitting element 33 having peripheral regions 33 s on both sides of a long central region 33 c along the diffraction direction is used, and the central region 33 c and the peripheral region 33 are used.
  • the output difference from s may be used instead of one of the photoelectric conversion elements 29 and 30. In this way, even when the light spots 31 and 32 become horizontally elliptical, the surrounding light amount can be effectively used for detection, which is preferable.
  • the peripheral region 33s may be provided separately on both sides of the central region 33c as shown in the figure to add the output, or may be provided so as to surround the central region 33c. .
  • the focus detection mechanism of the present invention is not only suitably applied to the optical storage device described above, but also an optical probe type shape measuring device or the like which requires a similar high-performance focusing sensor. It can also be applied to devices such as an atomic force microscope that optically captures the movement of the cantilever, and can provide compact and highly reliable focus detection.
  • the child 35 is composed of two symmetrical regions 35 A and 35 B corresponding to each other via a dividing line 35 p as shown in FIG. 9A.
  • the above-described hyperbolic patterns particularly off-axis patterns deviated in the y-direction from the hyperbolic origin as shown in FIG. 3 (c) are formed.
  • the half area 35A the left half of the off-axis pattern rotated clockwise by 80 degrees is drawn, and in the right half area 35B, the same off-axis pattern is counter-inverted. The right half of a clockwise rotation of 80 degrees is shown.
  • FIG. 10 is an explanatory view of the optical head of the magneto-optical recording / reproducing apparatus configured using the above-mentioned hologram element 35.
  • the divergent light from the semiconductor laser 38 is collimated by the collimator lens 39.
  • the light is converted into parallel light, reaches the hologram element 35 disposed immediately thereafter, and travels straight.
  • the 0th-order light passes through the objective lens 40 disposed at an appropriate distance and is collected on the recording medium surface 41.
  • a recording Z reproduction beam is formed.
  • the reflected light of the incident beam from the medium surface 41 becomes divergent light, travels backward, is converted into a substantially parallel light beam by the objective lens 40, and reaches the hologram element 35 again.
  • the two areas 35 A of the hologram element 35 , 35B form first-order diffracted lights 36A and 36B and + first-order diffracted lights 37A and 37B, respectively.
  • the hologram element 35 is arranged such that the division line 35 p is parallel to the track groove direction of the optical storage medium 41.
  • the diffracted lights 36 A, 36 B, 37 A, and 37 B are converged by the collimator lens 39, and as shown in FIG. 11, are shifted to the left and right along the dividing line 35 p of the hologram element 35.
  • a rectangular photoelectric conversion element 44 A, 44 B which is long along the radiation direction. 45 A and 45 B are provided, all of which are placed on the same plane.
  • two polarizing plate analyzers 46 and 47 are provided, respectively.
  • the transmission axes 46a and 47a are disposed so that they are turned to the right and left from the polarization axis of the semiconductor laser by an appropriate angle.
  • the diffracted light incident on the photoelectric conversion elements 44 A, 44 B, 45 A, and 45 B is minimum on the focal plane 39 f of the collimating lens 39 as in the case described above.
  • the circle of confusion It is a non-point convergent light flux.
  • the primary spots 42A, 42B projected on the photoelectric conversion elements 44A, 44B, and +1 projected on the photoelectric conversion elements 45A, 45B At the next spots 43A and 43B, the shape changes complementarily between the vertical ellipse and the horizontal ellipse. Therefore, using the outputs VIA, V1B, V2A, and V.2B of the photoelectric conversion elements 44A, 44B, 45A, and 45B,
  • the recording / reproducing beam is always output on the medium surface. Can converge.
  • a tracking error signal can be obtained. That is, if the value of the above equation is 0, the tracking is normal, and if the value is positive or negative, the tracking is off. Therefore, if tracking control of the objective lens is performed so that this signal has a constant value, the recording / reproducing beam can always be converged on the track.
  • a difference signal between the error signal and the control target value is obtained in the same manner as in the case of the focusing described above, and if necessary, an appropriate complementary value ⁇ is added thereto. And the like are known.
  • the analyzers 46 and 47 are provided for detecting the magneto-optical signal.
  • the medium reflected light of the reproduction beam incident on the semiconductor laser 38 with a unique polarization plane is transmitted between the eraser and the recording bit: the rotation directions of the polarization planes due to the force effect are mutually different. The opposite is true. Therefore, if, for example, one rotation occurs in the transmission direction 46a of the analyzer 46 arranged in the left photoelectric conversion elements 44A and 45B in the erasing section, the left photoelectric conversion element 44 The amount of light reaching A, 45B increases, and the amount of light from the right-handed photoelectric conversion elements 44B, 45A decreases.
  • the magneto-optical recording signal can be reproduced.
  • the differential output between the primary light and the primary light is obtained, so that the diffraction efficiency between the primary light and the primary light is higher. Even at different times or when defocusing occurs, it is possible to efficiently remove the in-phase light amount fluctuation noise and the like by taking advantage of the differential detection, and obtain a high-quality reproduced signal.
  • the light amount itself of the medium reflected light is modulated, so that the light amounts incident on the photoelectric conversion elements 44 A, 44 B, 45 A, 45 B all increase or decrease in the same manner. Therefore, in order to reproduce the pre-bit signal,
  • the optical head according to the present embodiment has a configuration with an extremely small number of components, and can obtain all the signals necessary for the magneto-optical recording device while being small in size and low in cost.
  • all the outputs of the four photoelectric conversion elements can be used for calculation of any signal, and can be generated by a calculation different from any of the signals, so that there is no waste of light quantity and crosstalk between signals. It is possible to obtain high quality magneto-optical signals, pre-pit signals and various error signals.
  • the photoelectric conversion element is long along the diffraction direction even with respect to the wavelength fluctuation of the light source, there is no effect due to the movement of the diffraction bot, and the astigmatic luminous flux of each astigmatic light flux is not affected.
  • an optical storage device equipped with the optical head of the present embodiment and controlling the focusing and tracking as described above has a high quality. It is supported by output signals, has high reliability and high performance, and has a small head, which makes the entire device smaller.
  • the step size is strict. There is no need to manage the device, and the manufacture of devices is greatly facilitated, especially for composite devices that incorporate a photoelectric conversion device in the same package as the semiconductor laser.
  • a similar light head is to be constructed using a conventional linear grating hologram element, as shown in Fig. 32, four photoelectric conversion elements are replaced by at least two base substrates 48a, 4b. It was necessary to make two pieces each on 8b and arrange them separately on both sides of the semiconductor laser.
  • the semiconductor laser 38 may be provided with a heat sink 50 provided on the base substrate 74 as shown in FIG. 12 or cut out at the center of the base substrate 51 as shown in FIG.
  • the structure may be such that the portion 5 la is provided and the heat sink 52 is disposed at the center of the cutout portion 51 a.
  • the heat sink 53 may be a cantilever structure, and the base substrate 49 may be inserted and arranged below the beam.
  • the photoelectric conversion elements used for detection can be formed on the same base substrate, not only the dimensional control during assembly is easy, but also the head, pump, signal processing, and signal processing are performed on the same base substrate. It is easy to mount arithmetic circuits etc. in a monolithic manner, and it is also easy to achieve further downsizing and higher performance.
  • the azimuth angles of the transmission axes 46 a and 47 a of the analyzers 46 and 47 were set to be appropriate. By changing this angle, the angle of the magneto-optical recording signal with respect to the amount of incident light was changed. The degree of modulation can be changed.
  • the angle so that the degree of modulation can be increased while suppressing noise proportional to the amount of incident light.
  • the polarizing plates instead of using the polarizing plates as the analyzers 46 and 47, another element having an analyzing function, for example, a polarizing beam splitter using a multilayer film may be used.
  • the rotation angles of the hyperbolic pattern in the regions 35A and 35B of the hologram element, and the directions of generation of the primary light and the primary light of the regions 35A and 35B are as described above. There is no need to limit. Furthermore, the combinations for obtaining various signals Other than this, any signal can be used as long as a similar signal can be obtained.
  • the focus detection and tracking are performed in the same manner for other types of optical recording devices and optical heads.
  • Detection and pre-bit detection are possible, and an optical storage device that performs focusing control, tracking control, and signal reproduction can be configured based on the detection and pre-bit detection.
  • read-only optical disk devices such as so-called compact disks and video disks
  • write-once disk devices such as dye recording type and hole-burning type
  • rewritable disk devices of phase change recording type can be used for These discs do not have magneto-optical bits, and the bits are all reflectance-modulated bits. Therefore, the analyzer having the above-described configuration is unnecessary. It is desirable to increase efficiency.
  • FIG. 15 shows a third embodiment in which the second embodiment is modified, and the same reference numerals as those described above denote the same functional members.
  • the four-valued photoelectric conversion elements are elongated along the direction of diffraction separation as shown in FIG. 11 and are arranged radially, whereas in this example, two photoelectric conversion elements are provided as shown in FIG. each of the photoelectric conversion element 4 4 a ', 4 4 B 5, 4 5 a', 4 5 B ' is a elongated in a direction parallel to each other.
  • the spot position deviation is not compensated for by the element shape. The placement error can be improved.
  • the diffracted lights 42A, 42B, 43A, and 43B are arranged at close angles such as ⁇ 80 ° with respect to the dividing line, the photoelectric conversion element 44A ', Since the longitudinal directions of 44B ', 45A', and 45B are roughly along the diffraction direction, the effect of complementing the movement of the robot when the wavelength varies is not impaired on a practical level. This is effective because a manufacturing error in the scale direction can be compensated.
  • FIGS. 16 to 17 show a fourth embodiment in which the second embodiment described above is modified
  • the same reference numerals as those described above represent similar functional members.
  • the hologram patterns in the left and right regions of the dividing line are the same off-axis pattern, and the spots can be separated by changing the pattern rotation angles in the left and right regions 35A and 35B.
  • the hologram element 55 of the present embodiment the hologram pitches of the areas 55A and 55B are changed.
  • the left and right patterns are basically different in the degree of off-axis from the origin of the force hyperbola generating the luminous flux with the same focus distance ⁇ f, so that the diffraction separation angles are different.
  • the diffracted light beams 56 A, 56 B, 57 A and 57 B by the respective regions 55 A and 55 B can be arranged on a straight line.
  • a pattern with a large pitch that is, a pattern with a small degree of off-axis is drawn by rotating by 90 degrees
  • a part with a small pitch that is, a degree of off-axis is large. If the pattern is drawn by rotating the pattern by ⁇ 90 degrees, the ⁇ 1st-order diffraction robots 58 B and 59 B in the area 55 B will be two spots 58 A and 59 A in the area 55 A Appears in a straight line outside of.
  • the corresponding four photoelectric conversion elements 60 A, 60 B, 61 A, and 61 B are also arranged linearly, and the spot movement at the time of wavelength fluctuation is reduced. This is effective because it can completely compensate and, as in the previous embodiment, can reduce the manufacturing tolerance in the diffraction separation direction.
  • FIG. 18 shows a fifth embodiment of the present invention, and the same reference numerals as those described above denote the same functional members.
  • the divergent light from the semiconductor laser 21 is collimated by the collimating lens 22, then passes through the beam splitter 62, passes through the objective lens 24, and passes on the optical storage medium surface 25.
  • the reflected light of the incident beam from the medium surface 25 becomes divergent light, travels backward, is converted into a substantially parallel light beam by the objective lens 24, and is transmitted to the hologram element 63 arranged on the optical path bent by the beam splitter 62.
  • the hologram element 63 has a hyperbolic pattern similar to that of the above-described first embodiment.
  • the ⁇ 1st-order diffracted light emitted in this manner is refracted by the condenser lens 64 disposed immediately thereafter.
  • the condenser lens 64 On the focal plane 64 f of the focusing lens 64, two photoelectric conversion elements 29, 30 is provided.
  • the hologram element 63 can be of a split type as in the second embodiment, and four photoelectric conversion elements can be provided to form the same optical head and optical storage device.
  • the efficiency of the zero-order light can be reduced as described above, and the efficiency of the ⁇ first-order light can be increased instead.
  • the amount of light reaching the photoelectric conversion elements 29, 30 can be reduced. Many are preferred.
  • the focal length of the condenser lens 64 is made longer than the focal length of the collimator lens 22, the longitudinal magnification of the optical system for detection with respect to the medium side can be independently adjusted to be higher. Therefore, it is possible to widen the astigmatic difference of the detection light beam while securing the light use efficiency of the semiconductor laser, and it is possible to increase the focus error detection sensitivity.
  • FIGS. 19 to 21 show a sixth embodiment of the present invention, and the same reference numerals as those described above denote the same functional members.
  • the hologram element 65 placed in the parallel optical path is a divided hologram element 65 having a pattern similar to that of the second embodiment described above, and the respective areas 65 A and 65 A are formed by the blazing method described above.
  • One of the ⁇ 1st-order lights of 5B, for example, is configured so that only the intensity of the light beam diffracted to the right of the dividing line 65P is increased. It is known that such blazing can be realized, for example, in a transmission type hologram element 65 by forming a sawtooth cross section 65c that rises to the left as shown in FIG. If the blazing angle is set appropriately, the light intensity can be reduced to almost zero for light diffracted to the left.
  • the diffracted light on the return path involved in detection is the primary light 66 B of the region 65 B diffracting rightward of the dividing line 65 p and the + primary light 67 of the region 65 A A only.
  • the photoelectric conversion elements 68 B and 69 A corresponding to the two light beams 66 B and 67 A are provided on the detection surface in the same plane.
  • the two photoelectric conversion elements 68 B and 69 A are provided with two peripheral areas 68 Bs and 69 As on both sides of the central area 68 Bc and 69 Ac, respectively. It is a dividing element, and the dividing lines are provided along the respective diffraction directions. Assuming that the photoelectric conversion output of each area 6 8 B c, 6 8 B s, 6 9 A c, 6 9 A s is V 1 c, V is, V 2 c, V 2 s, focusing •
  • the error signal is
  • the magneto-optical reproduction signal can be obtained at Further, if analyzers having different azimuths of transmission axes are provided on the front surfaces of the photoelectric conversion elements 68B and 69A, the magneto-optical reproduction signal can be obtained.
  • the optical head according to the present embodiment also has a configuration with an extremely small number of components and requires only one side of the light source to be provided with the light detecting means. All the signals required for a magneto-optical recording device can be obtained at low cost. In addition, since all the outputs of the photoelectric conversion means can be used for calculating any of the signals, it is possible to obtain high-quality magneto-optical signals, pre-bit signals, and various error signals without wasting light. is there.
  • the photoelectric conversion element is long along the diffraction direction even with respect to the wavelength variation of the light source, there is no effect due to the movement of the diffraction spot, and the two non-point convergent light beams Since the focal line position moves back and forth by approximately the same amount, the center of the differential does not deviate, and even when using a light source such as a semiconductor laser whose emission wavelength is liable to fluctuate, the advantages of the hologram element can be fully utilized. We can make use of it. Therefore, the optical storage device equipped with the optical head of the present embodiment and controlling the focusing and tracking as described above can provide a high-quality output signal, high reliability, high performance, and a small size. As a result, the entire device can be downsized.
  • the long directions of the photoelectric conversion elements 68 B and 69 A can be made parallel based on the above-described modification.
  • the diffraction spots can be separated by changing the pattern pitch. Wear.
  • the present invention can be similarly applied to the case where the light beam is separated on the return path as in the fifth embodiment.
  • FIGS. 22 to 23 show a seventh embodiment of the present invention.
  • the divergent light from the semiconductor laser 21 passes through the hologram element 75 and passes through the condenser lens 76.
  • the beam is converged and forms a recording Z reproduction beam to be received on the recording medium 25.
  • the reflected light travels backward in the optical path and is refracted by the condenser lens 76, and reaches the hologram element 75 again to generate ⁇ first-order diffracted lights 78 and 79.
  • the diffracted lights 78 and 79 form a two-point astigmatic light flux in a manner similar to the above-mentioned case that passes through the lens after diffraction, and when both light fluxes are focused, the emission end of the semiconductor laser 21 is focused. Connect the circle of least confusion on f.
  • the convergence position of the light beam moves rearward when the medium 25 is close, and moves forward when the medium 25 is far. Therefore, the same two photoelectric conversion elements 29 and 30 as in the first embodiment are provided in the plane of the emission end of the semiconductor laser 21 to perform focus detection. At this time, only the focusing lens 76 or the entire finite system 80 from the focusing lens 76 to the photoelectric conversion elements 29 and 30 is moved back and forth by an actuator (not shown) so that the focusing 'error signal obtained at this time becomes a constant value. By driving, the recording / reproducing beam can be always converged on the medium surface.
  • the hologram element 75 is arranged in the convergent light path.
  • the hologram separates the convergent light beam, if the ⁇ 1st-order diffracted light 78 and 79 are used together, a slight curve correction is required for the pattern. Even if the correction is performed, the astigmatism common to the two light beams is generated. As a result, the astigmatism of the primary light beam 78 is large, and the astigmatic difference of the + first light beam 79 is small. I cannot escape from the phenomenon.
  • the necessary correction amount is small and the pattern shape is not much different from the hyperbola.
  • astigmatism generated at the time of separation is also small, and if a force that hardly causes a problem for detection is needed, the photoelectric conversion elements 29, 30 are required according to the diameter of the circle of least confusion.
  • the detection sensitivity may be made uniform by changing the width of the detection.
  • the diffracted light on the outward path by the hologram element is transmitted to the objective lens. It was easy to disperse the light outside the optical path as unnecessary light by adjusting the distance in the optical path. In a finite system, the distance to the condenser lens 76 is limited, so it is not so easy to take a sufficient distance, but if this distance is not enough, for example, 0 in the return path of the outgoing + 1st order light Since the next light overlaps with the minus first light of the return light of the 0th light on the outward path and interferes with the focus detection, the position of the hologram element 75 should be determined in consideration of this point.
  • the hologram element 75 is provided with an aperture stop by using unnecessary return light passing through an optical path distant from the optical axis as compared with the desired diffracted lights 78 and 79 on the return path, the above-described restriction is imposed. Can be reduced.
  • a beam splitter 81 may be provided in the convergent light path, the light path may be divided into the forward path and the return path, and a finite system may be configured such that only the return path passes through the hologram element 75.
  • unnecessary diffracted light on the outward path is not generated, so that the hologram element sets the diffraction efficiency of the 0th-order light to almost zero and increases the efficiency of the ⁇ 1st-order light as in the previous embodiment. It is desirable. It is also preferable to improve the detection sensitivity by inserting a negative lens on the detection side as necessary and increasing only the vertical magnification on the detection side. Furthermore, if the detection lens is intentionally given an appropriate astigmatism, the above-mentioned unnecessary astigmatism generated in the hologram of the convergent light path can be canceled out, which is extremely effective.
  • the hologram element 75 is of a split type similar to that of the second embodiment, and four photoelectric conversion elements are provided. In this case, tracking is also performed by driving the entire finite system from the condenser lens 76 to the photoelectric conversion element.
  • Finite optical head can be configured extremely simply by the present invention.
  • Finite-type heads have few adjustment items during manufacturing, can be made even smaller, and have high reliability after manufacturing. Therefore, they are preferable for miniaturizing optical storage devices and ensuring reliability.
  • FIGS. 24 to 26 show an eighth embodiment of the present invention, which shows another embodiment in which a finite system head is constructed, and which is used to eliminate the above-mentioned influence of unnecessary astigmatism.
  • the hologram element 85 is divided into two left and right regions 85A and 85B by a dividing line 85p as in the second embodiment.
  • the diffraction direction is, for example, 80 in the clockwise and counterclockwise directions. Separated by rotation.
  • Each of the regions 85A and 85B has a corrected hyperbolic pattern.
  • the astigmatic difference of the diffracted light beam is large in the -first light beams 86A and 86B, and the + first light beam 87 and
  • the astigmatism of the primary light flux 86B of one area 85B and the astigmatic difference of the + primary light flux 87A of the other area 85A are reduced in the hologram element & 5 of this embodiment.
  • the focus distance f unique to each of the patterns of the areas 85A and 85B is changed so as to be equal. ⁇ ⁇
  • the diffracted light beams 86 B and 87 A given equal astigmatic difference form the smallest circle of confusion with the same diameter on the same plane 76 f, and the convergence position of the light beam moves before and after focusing. I do. Since each light beam has the opposite astigmatic difference, at the minimum confusion circle position at the time of focusing, astigmatism spots and zots that change vertically to horizontally long ellipse are obtained.
  • the photoelectric conversion elements 88B and 89A are divided elements having the peripheral areas 88Bs and 89As on the rain side of the central areas 88Bc and 89Ac as described above. The output difference between the central area and the peripheral area is used.
  • the other diffracted light fluxes S 7 B and 86 A in each area will have astigmatic differences that differ greatly in magnitude. In this embodiment, the total light amount is not used for calculating the forcing-error signal.
  • V1Bc + V1Bs + V2Ac + V2As It can be obtained in one (V1A + V2B).
  • (V1Bc + V2As) and (V2Ac + V1Bs) can be handled collectively, which is convenient because a connection can be made on the photoelectric conversion element. Furthermore, if the addition capacity of the photoelectric conversion element relating to the calculation of the magneto-optical signal (V1Bc + V2As + V2Ac + V1Bs) is made equal to the addition capacity relating to (V1A + V2B) It is preferable because common mode noise can be efficiently removed by differential detection.
  • the influence of unnecessary astigmatism when the astigmatism generating hologram is placed in the convergent light path can be eliminated in the detection stage.
  • both the ⁇ 1st-order diffracted lights that change complementarily to each other are used, good focus detection is possible, and changes in the diffraction angle are long even with wavelength fluctuations.
  • the advantage of the hologram can be fully utilized even when using a light source such as a semiconductor laser in which the emission wavelength is easily changed without the center of the differential being shifted.
  • the force described for the type that separates the spot by changing the diffraction direction on the left and right of the dividing line 85p is also used for the type that separates the spot by changing the diffraction separation angle on the left and right as described above.
  • the hologram element 85 of the present embodiment can be blazed in the same manner as in the sixth embodiment. That is, in FIG. 26, when the hologram element 85, is blazed so as to increase the light intensity of the light fluxes 86B, 87A having the same astigmatic difference, the light intensity of the other two face-folded lights (not shown) is obtained. Can be made almost zero, and only the two sets of photoelectric conversion elements 88 B and 89 A which are divided elements need to be provided. Assuming that the outputs of the photoelectric conversion elements 88 Bc, & 8 Bs, 88 Ac, and 88 As are Vic, Vis, V2 c, and V2 s, respectively, the focusing error signal is
  • the tracking error signal is
  • the magneto-optical reproduction signal can be obtained at Further, if the analyzers 70 and 71 having different detection angles are provided in front of the respective photoelectric conversion elements 88 B and 89 A, the magneto-optical reproduction signal can be obtained.
  • the optical head configured as described above has a small number of adjustment items at the time of manufacture because it is a finite system. — It can be made much smaller, and has high reliability after manufacturing. It is only necessary to dispose the photoelectric conversion elements 88B and 89A only on the side, which is preferable because the manufacture is easier.
  • the hologram element 85 ′ can be sufficiently moved from the light source. It can be placed at a remote location. In this case, the distance between the light source and the photoelectric conversion element can be increased while the diffraction angle of the hologram is kept small, so that the manufacturing is further facilitated and preferable.
  • FIG. 27 shows a ninth embodiment of the present invention, and the same reference numerals as those described above denote the same functional members.
  • the divergent light from the semiconductor laser 38 is bent at the beam splitter 91 and is made parallel by the collimator lens 39.
  • An objective lens 40 is arranged in the parallel light beam, and the light passing therethrough forms a recording Z reproduction beam that converges on the storage medium surface 41.
  • the objective lens 40 is movable in a direction perpendicular to the track groove of the storage medium 41, and the beam can be moved to a desired track by moving the objective lens 40.
  • a lens shift sensor 92 for providing the amount of movement of the objective lens 40 at this time is provided.
  • the light reflected by the medium surface is converted into a substantially parallel light beam again by the objective lens 40, travels backward in the optical path, is converged by the collimating lens 39, and is incident on the beam splitter 91.
  • the light beam that travels straight here then enters the hologram element 95 through the negative detection lens 93 arranged.
  • the hologram element 95 is divided into two left and right regions 95A and 95B by a dividing line 95p as in the fourth embodiment, and the spots of each region are divided into the left and right regions. Is changed by changing the diffraction separation angle at.
  • Each region has a corrected hyperbolic pattern, and generates four astigmatic light beams 96 A, 96 B, 97 A, and 97 B.
  • each photoelectric conversion output is V 1 A, V 1 B, V 2 A, V 2 B
  • the focusing error signal is
  • the objective lens 40 is driven in the focus direction so that the value becomes a constant value, and the recording Z reproduction beam can always be converged on the medium surface 41. Also, the tracking error signal is
  • the error signal generates an offset.
  • the lens shift sensor 92 is provided to correct the offset, and the offset can be removed by multiplying the output of the lens shift sensor by an appropriate coefficient and adding it to the tracking error signal. Therefore, if the tracking servo control of the objective lens 40 is performed so that the corrected tracking error signal has a constant value, the recording / reproducing beam can always be converged on the track.
  • the lightweight objective lens 40 since only the lightweight objective lens 40 can perform the tracking operation, it is suitable for use where high-speed tracking is required.
  • a magneto-optical signal can be detected by providing an analyzer in the same manner as described above.
  • the negative detection lens 93 provided for detection has a high vertical magnification to improve the focus detection sensitivity. Further, as described above, it is effective to intentionally impart astigmatism to the detection lens 93 to cancel unnecessary astigmatism generated in the hologram element 95 in the converging light path.
  • all necessary signals can be obtained while being small in size and low in cost.
  • all the outputs of the four photoelectric conversion elements can be used for the operation of any signal, and can be generated by an operation different from any of the signals, so that there is no waste of light amount and there is no crosstalk between signals. It is possible to obtain few and high quality signals.
  • the wavelength of the light source fluctuates, there is no influence due to the movement of the diffraction lens, and the light source such as a semiconductor laser whose emission wavelength is liable to fluctuate without a shift of the differential center of focus detection. Even when used, the advantages of the hologram element can be fully utilized. Therefore, the optical storage device equipped with the optical head according to the present embodiment is supported by high-quality output signals, has high reliability and high performance, and can be downsized by the small head.
  • FIGS. 28 to 29 show a tenth embodiment of the present invention.
  • the divergent light from the semiconductor laser 21 is collimated by the collimating lens 22 and is oblique.
  • To the reflection-type hologram element 100 which is arranged in the hologram.
  • the objective lens 24 On the outward path, only the specularly reflected zero-order light passes through the objective lens 24 disposed at an appropriate distance to form a recording Z reproduction beam converging on the optical storage medium 25.
  • the reflected light becomes divergent light, travels backward, is converted into a substantially parallel light beam by the objective lens 24, and reaches the hologram element 100 again to be diffracted.
  • the diffracted light is refracted by the collimating lens 22 and received by the photoelectric conversion elements 101 and 102 arranged in the same plane near the focal plane 22 f of the collimator lens 22. .
  • the hologram element 100 is a pattern that generates a non-point-collected luminous flux similar to some of the preceding hologram elements by applying one-dimensional correction to the above-described hyperbolic pattern with respect to the inclination direction of the reflection surface.
  • the hologram element 100 is of a split type as in the second embodiment, and four photoelectric conversion elements are provided to form the same optical head and optical storage device as in the embodiment.
  • the hologram element 100 When the hologram element 100 is arranged obliquely as described above and the diffraction direction in which the light beam is generated is set to the inclined direction, one of the diffracted light beams becomes the same as when the hologram element is arranged in the convergent light path.
  • the astigmatism of the other beam becomes smaller and the astigmatism of the other beam becomes smaller, or the angle of the diffracted light from the specularly reflected light differs for ⁇ 1st order light, and the distance of the robot from the center is two Changes such as differences appear.
  • the direction of diffraction of the light beam by the reflection hologram element 100 be in a direction perpendicular to the tilt direction than in the case shown in the figure.
  • the reflection hologram element 100 is constituted by the segmented hologram element 100, as described above, if the reflection hologram element 100 is blazed to use one light flux in each area, the above-described astigmatism is obtained. The problem of the difference in the distance can be avoided, and good focus detection is possible even when the diffraction direction is made coincident with the tilt direction, which is preferable.
  • the hologram element 105 is a reflection type in a finite optical system as shown in FIG. 29, a similar detection system can be configured by performing one-dimensional correction as in this embodiment.
  • the diffraction direction in which the luminous flux is generated is orthogonal to the inclination direction. They can also be placed. The effect obtained by brazing is the same as described above.
  • FIG. 30 shows an eleventh embodiment of the present invention, in which the photoelectric conversion element 29 or the photoelectric conversion element 30 has the same configuration as that of the first embodiment, as shown in FIG. 4 strips
  • the light receiving areas 110a, 110b, 110c, 110d are arranged in parallel to form a quadrant element 110.
  • the projected light spot 31 will be as shown in FIG. Because the position of can swing from side to side
  • quadrant 110 may be replaced with either one of the photoelectric conversion elements 29 and 30, or one of them may be used.
  • the calculation for obtaining various signals may be performed in a manner that the addition and the subtraction are reversed depending on the modification of the equation, but this is a change within the scope of the present invention.
  • the focus detection mechanism in the focus detection mechanism according to the present invention, two photoelectric conversion elements for obtaining a differential output can be arranged in the same plane, so that manufacturing with improved dimensional accuracy is easy. Furthermore, the advantage of the hologram element can be fully utilized even when a light source such as a semiconductor laser whose emission wavelength is liable to be changed without the center of the differential being shifted with respect to the wavelength change. Further, the optical head of the present invention has a configuration with an extremely small number of parts, is small in size and low in cost, and can efficiently obtain a signal required for the optical storage device. Signal and various error signals. Further, the optical storage device of the present invention equipped with the above-mentioned optical head can be realized at a low cost with a simple configuration and high performance. As described above, the present invention has a great effect in this field, and the possibility of using the present invention is extremely high.

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Abstract

Mecanisme de détection de focalisation dans lequel la lumière réfléchie par la surface d'un objet (25) est diffractée par un élément holographique (23). La lumière diffractée comprend deux faisceaux astigmatiques convergents qui forment de moindres cercles de confusion sur de longs organes photodétecteurs (29) et (30) dans le même plan à proximité du plan focal (22f) d'une lentille (22). On obtient un signal de focalisation en fonction d'une sortie différentielle des deux organes photodétecteurs. Etant donné que deux faisceaux diffractés présentent de moindres cercles de confusion dans le même plan, les organes photodétecteurs peuvent être placés horizontalement, et on peut réaliser aisément un mécanisme de détection de focalisation présentant une meilleure précision dimensionnelle. Malgré l'utilisation d'un élément holographique, les fluctuations de longueur d'onde peuvent être absorbées, ce qui rend le dispositif extrêmement fiable.
PCT/JP1992/001441 1991-11-08 1992-11-06 Mecanisme de detection de focalisation et tete optique et memoire optique l'utilisant WO1993009535A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP05508321A JP3132001B2 (ja) 1991-11-08 1992-11-06 合焦検出機構ならびにこれを用いた光ヘッド及び光記録装置
KR1019930702028A KR100191884B1 (ko) 1991-11-08 1992-11-06 초점검출기구 및 그것을 사용한 광헤드와 광기억장치

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP3/293329 1991-11-08
JP29332991 1991-11-08
JP33724591 1991-12-19
JP3/337245 1991-12-19
JP8554192 1992-04-07
JP4/85541 1992-04-07

Publications (1)

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WO1993009535A1 true WO1993009535A1 (fr) 1993-05-13

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JP (1) JP3132001B2 (fr)
KR (1) KR100191884B1 (fr)
WO (1) WO1993009535A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1058100C (zh) * 1994-10-25 2000-11-01 株式会社三协精机制作所 光拾取装置

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01179237A (ja) * 1987-12-28 1989-07-17 Olympus Optical Co Ltd 光学式ピックアップ装置

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01179237A (ja) * 1987-12-28 1989-07-17 Olympus Optical Co Ltd 光学式ピックアップ装置

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1058100C (zh) * 1994-10-25 2000-11-01 株式会社三协精机制作所 光拾取装置

Also Published As

Publication number Publication date
KR930703669A (ko) 1993-11-30
KR100191884B1 (ko) 1999-06-15
JP3132001B2 (ja) 2001-02-05

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