WO2001018801A1 - Tete optique - Google Patents
Tete optique Download PDFInfo
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- WO2001018801A1 WO2001018801A1 PCT/JP2000/005889 JP0005889W WO0118801A1 WO 2001018801 A1 WO2001018801 A1 WO 2001018801A1 JP 0005889 W JP0005889 W JP 0005889W WO 0118801 A1 WO0118801 A1 WO 0118801A1
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- Prior art keywords
- electrode
- power supply
- phase correction
- correction element
- voltage
- Prior art date
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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
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1343—Electrodes
- G02F1/134309—Electrodes characterised by their geometrical arrangement
-
- 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
- G11B7/095—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 specially adapted for discs, e.g. for compensation of eccentricity or wobble
- G11B7/0956—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 specially adapted for discs, e.g. for compensation of eccentricity or wobble to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc
-
- 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
- G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
- G11B7/1369—Active plates, e.g. liquid crystal panels or electrostrictive elements
-
- 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
- G11B7/1372—Lenses
- G11B7/1374—Objective lenses
-
- 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
- G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
- G11B7/13925—Means for controlling the beam wavefront, e.g. for correction of aberration active, e.g. controlled by electrical or mechanical means
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2203/00—Function characteristic
- G02F2203/18—Function characteristic adaptive optics, e.g. wavefront correction
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B2220/00—Record carriers by type
- G11B2220/20—Disc-shaped record carriers
- G11B2220/25—Disc-shaped record carriers characterised in that the disc is based on a specific recording technology
- G11B2220/2537—Optical discs
Definitions
- the present invention relates to an optical head device for recording and reproducing information on an optical recording medium such as an optical disk.
- DVDs which are optical discs, record digital information at a higher density than CDs, which are also optical discs.
- Optical head devices for reproducing DVDs use light sources with wavelengths shorter than 780 nm for CDs.
- the diameter of the spot focused on the optical disk surface is reduced by setting the numerical aperture (NA) of the objective lens to 50 nm or 635 nm, or the numerical aperture (NA) of the objective lens to 0.6, which is larger than 0.45 of the CD.
- One method is to add a tilt axis to the objective lens actuator that normally moves in two axial directions, the tangential direction and the radial direction of the optical disc, so that the objective lens is tilted according to the detected tilt angle.
- This additional method has problems that spherical aberration cannot be corrected and the structure of the actuator becomes complicated.
- this correction method there is a method in which the wavefront difference is corrected by a phase correction element provided between the objective lens and the light source. With this correction method, it is possible to increase the allowable amount of tilt and unevenness of thickness of the optical disk only by incorporating an element into the optical head device without making a major modification to the actuator.
- Japanese Patent Application Laid-Open No. H10-202623 is disclosed in Japanese Patent Application Laid-Open No. H10-202263.
- a voltage is applied to the divided electrodes formed by dividing the electrodes on each of a pair of substrates sandwiching a birefringent material such as a liquid crystal that constitutes the phase correction element, and the birefringence is applied.
- the refractive index of the conductive material is changed according to the tilt angle of the optical disk, and the phase (wavefront) of the transmitted light generated by the change in the refractive index is corrected for the coma caused by the tilt of the optical disk. It is a method.
- the electrodes provided in the phase correction element are divided into a plurality of electrodes, and voltages that are different control signals are applied to the electrodes.
- the electrodes provided in the phase correction element are divided into a plurality of electrodes, and voltages that are different control signals are applied to the electrodes.
- the amount of change in the wavefront is the same, so it is difficult to change it continuously.
- an external signal cannot be applied to the region between the divided electrodes, light transmission may be reduced due to light scattering or the like. Therefore, it has been desired to reduce the number of divided electrodes as much as possible to reduce the number of areas between the electrodes. Disclosure of the invention
- the present invention has been made to solve the above problems, and has a light source, an objective lens for condensing light emitted from the light source on an optical recording medium, and a light source and an objective lens.
- a phase correction element for changing the wavefront of emitted light provided, at least one of which has an anisotropic optical medium sandwiched between a pair of transparent substrates, and has a different surface on the pair of substrates. Electrodes for applying a voltage to the anisotropic optical medium are respectively formed, a plurality of power supply portions are formed at different positions on at least one of the electrodes, and different voltages can be supplied to the plurality of power supply portions.
- An optical head device comprising: a phase correction element configured as described above; and a control voltage generation means for outputting a voltage for changing a wavefront to the phase correction element.
- a light source an objective lens for condensing the light emitted from the light source on the optical recording medium; and a phase correction element provided between the light source and the objective lens for changing the wavefront of the emitted light.
- the electrode on which the power supply unit is formed is divided into a plurality of divided electrodes, and one or more power supply units are disposed on each of the divided electrodes, and two or more of the power supply units are provided as described above.
- An optical head device is provided that is conductively connected via a thin film resistor.
- each of the plurality of power supply units is an annular body and is disposed concentrically with each other, and any one of the plurality of power supply units with respect to a luminous flux radius of light emitted from the light source and passing through the phase correction element.
- the ratio of the radius of the torus is 0.65 to 0.85, and the ratio of the radius of the other one of the toroids to the light flux radius is 0.2 to 0.4, wherein the optical head device is provided.
- the present invention also provides the above optical head device, wherein only one of the pair of substrates is a transparent substrate.
- the present invention provides the above optical head device, wherein the anisotropic optical medium is a liquid crystal. Further, the present invention provides the above optical head device, wherein a sheet resistance of an electrode material forming the electrode having the power supply portion is 100 or more.
- the present invention provides the above optical head device, wherein all of the thin film resistors have a resistance value in a range from 100 ⁇ to 100 k ⁇ .
- the present invention provides the above optical head device, wherein the sheet resistance of the electrode material forming the electrode is 100 times or more as large as the sheet resistance of the power supply part material forming the power supply part.
- the above-mentioned electrode material provides the above optical head device comprising a zinc oxide film to which gallium is added or a zinc oxide film to which gallium and silicon are added.
- FIG. 1 is a conceptual cross-sectional view showing an example of the principle configuration of the optical head device of the present invention.
- FIG. 2 is a cross-sectional view illustrating an example of the phase correction element according to the present invention.
- FIG. 3 is a diagram showing spherical aberration when the thickness unevenness of the optical disc is 0.3 mm.
- FIG. 4 is a schematic plan view showing an example in which a conventional lead wire (wiring) is used for the electrode pattern of the phase correction element according to the present invention.
- FIG. 5 is a circuit diagram showing an equivalent circuit of the phase correction element in FIG.
- FIG. 6 is a diagram illustrating an example of a phase change amount generated by the phase correction element according to the present invention.
- FIG. 7 is a schematic plan view showing an example of an electrode pattern and a thin film resistor of the phase correction element according to the present invention.
- FIG. 8 is a circuit diagram showing an example of an equivalent circuit of the phase correction element in FIG.
- FIG. 9 is a schematic plan view illustrating an electrode pattern of the phase correction element according to the first embodiment.
- FIG. 10 is a diagram illustrating the wavefront aberration when the optical disc has a tilt of 1 °.
- FIG. 11 is a diagram illustrating a phase change generated by the phase correction element of the first embodiment (when there is no lens shift).
- FIG. 12 is a diagram illustrating a phase change generated by the phase correction element according to the first embodiment (when there is a rightward lens shift).
- FIG. 13 is a schematic diagram illustrating an electrode pattern of the phase correction element according to the second embodiment.
- FIG. 14 is a diagram illustrating a phase change generated by the phase correction elements of the second, third, and fifth embodiments.
- FIG. 15 is a schematic diagram showing an electrode pattern of a phase correction element in Examples 3 and 6.
- FIG. 16 is a schematic diagram illustrating an electrode pattern of the phase correction element according to the fourth embodiment.
- FIG. 17 is a schematic plan view showing one electrode pattern of the phase correction element of the sixth embodiment.
- FIG. 1 shows an example of the principle configuration of the optical head device of the present invention.
- the optical head device shown in FIG. 1 is for reproducing information recorded on an optical disk 8 such as a CD or DVD, and the light emitted from a light source, for example, a semiconductor laser 1 is, for example, a holo-lam-type polarization beam.
- a light source for example, a semiconductor laser 1
- the light is focused on the optical disc 8 by the objective lens 6 installed in the actuator 7.
- the pair of substrates constituting the phase correction element 4 are both transparent. Both substrates may not be transparent, and only one may be transparent, which will be described later.
- the condensed light is reflected by the optical disk 8, and passes through the objective lens 6, the quarter-wave plate 5, the starting mirror 11, the phase correction element 4, and the collimating lens 3 in reverse order, and then, The light is diffracted by the polarization beam splitter 2 and enters the photodetector 9.
- the reflected light is amplitude-modulated by information recorded on the surface of the optical disk, and the recorded information is read by the light detector 9 as a light intensity signal. be able to.
- the polarization beam splitter 2 includes, for example, a polarization hologram, and strongly diffracts light having a polarization component in an anisotropic direction (a direction having a difference in refractive index) and guides the light to the photodetector 9.
- a voltage is output to the phase correction element 4 by the phase correction element control circuit 10, which is a control voltage generation means, so that the intensity of, for example, a reproduction signal of the optical disk obtained from the photodetector 9 is optimized.
- the voltage output from the phase correction element control circuit 10 is a voltage corresponding to the amount of tilt of the optical disc or the amount of shift of the objective lens, and is a voltage that is substantially changed and applied to the electrode of the phase correction element 4.
- the rising mirror 111 reflects the light emitted from the semiconductor laser 1 in the direction of about 90 ° and makes it incident on the optical disk.
- the thickness of the optical head device (in the direction perpendicular to the surface of the optical disk 8) This is an optical component that is preferably used to reduce the thickness.
- a material obtained by depositing a highly reflective film such as aluminum on a glass surface is used.
- the optical path of the light emitted from the semiconductor laser 1 was changed using the rising mirror 111, but from the beginning, the semiconductor laser 1 did not use the rising mirror 111.
- the direction of the emitted light may be perpendicular to the surface of the optical disc 8.
- Optical crystals such as lithium niobate and liquid crystals can be used as the anisotropic optical medium. It is preferable to use a liquid crystal as the anisotropic optical medium because the substantial refractive index can be easily controlled by a voltage as low as about 6 V and can be continuously controlled according to the magnitude of the voltage. Furthermore, mass productivity is higher than that of optical crystals such as lithium niobate, which is preferable. Therefore, the case where a liquid crystal material is used as the anisotropic optical medium will be described below.
- the liquid crystal material used is preferably a nematic liquid crystal used for display applications, and may be twisted by adding a chiral agent.
- glass acrylic resin, epoxy resin, vinyl chloride resin, polycarbonate resin, or the like can be used, but a glass substrate is preferable in terms of durability and the like. Therefore, the case where glass is used as the material of the substrate will be described below.
- the sealing material 22 includes, for example, a glass spacer and a conductive spacer in which, for example, a resin surface is coated with gold or the like.
- an electrode 24a On the inner surface of the glass substrate 21a, an electrode 24a, an insulating film 25 mainly composed of silica, etc., and an alignment film 26 are arranged in this order from the inner surface, and on the inner surface of the glass substrate 21b.
- the outer surface of the liquid crystal cell may be coated with an antireflection film.
- the electrode 24a is wired in a pattern so that it can be connected to the phase correction element control circuit by a connection line at the electrode lead portion 27.
- the electrode 24b is conductively connected to the electrode 24a formed on the glass substrate 21a by the above-described conductive spacer coated with gold or the like. In section 27, it can be connected to the phase correction element control circuit by a connection line.
- FIG. 2 does not show that the electrode 24 b and the electrode 24 a are in contact with the sealing material 22, but that the electrode 24 b and the electrode 24 a are in contact with the sealing material parallel to the plane of the drawing and both electrodes are conductive.
- the liquid crystal cell 23 is filled inside the liquid crystal cell, and the liquid crystal molecules 28 shown in FIG. 2 are homogenized in one direction. In a state of alignment.
- a plurality (two or more) of power supply units for supplying different voltages to at least different positions in the plane of at least one of the electrodes 24 a and 24 b is provided. Is formed. In other words, two or more power supply parts are formed for one electrode, and two or more power supply parts (total of four or more) are formed for both electrodes.
- the pretilt angle of the liquid crystal molecules 28 is 2 to 10 °.
- a polyimide film obtained by rubbing the polyimide film in the left and right direction parallel to the paper of FIG. 2 or a silica film is preferable. Those obtained by oblique deposition are preferable.
- the difference between the ordinary refractive index and the extraordinary refractive index of the liquid crystal is 0.1 to 0.2, and the distance between the liquid crystal cells is 2 to 5 It is preferable to set it to about ⁇ m.
- the material of the electrodes 24a and 24b should have higher transmittance.
- a transparent conductive film such as an ITO film or a zinc oxide film may be used.
- the phase correction element 4 is used as a transmission element.
- one of the electrodes 24a and 24b is made of a material having high reflectance such as aluminum or chrome, and the phase correction element 4 is formed. It can be used as a reflective element. At this time, the phase capturing element 4 can be installed at this position instead of the start-up mirror 11 in FIG. If the electrode on which light is first incident (for example, electrode 24a) is a transparent electrode with high transmittance and the other electrode (for example, electrode 24b) is an electrode with high reflectivity, phase correction can be performed. The light incident on the element 4 passes through the transparent electrode 24a and the liquid crystal and is reflected by the electrode 24b, and then passes through the liquid crystal and the transparent electrode 24a again to the optical disk 8.
- the electrode on which light is first incident for example, electrode 24a
- the other electrode for example, electrode 24b
- phase correction can be performed.
- the light incident on the element 4 passes through the transparent electrode 24a and the liquid crystal and is reflected by the electrode 24b, and then passes through the liquid crystal and the transparent electrode 24a again to the optical
- phase correction element 4 If a reflective element is used as the phase correction element 4 as described above, that is, if one of a pair of substrates constituting the complementary element is a transparent substrate, the rising mirror 11 in FIG. Since the element 4 can be replaced, the number of parts is reduced, and the thickness of the optical head device can be reduced, which is preferable. In this case, the light incident on the phase correction element 4 passes through the liquid crystal 23 twice at an angle of approximately 45 °, which is different from the case of the transmission type.
- the liquid crystal cell interval (the thickness of the liquid crystal layer in the liquid crystal cell) may be set in advance.
- a dichroic aperture limiting layer for changing the luminous flux diameter according to the wavelength of the diffraction grating or light source is laminated on the phase correction element 4, or a dichroic aperture limiting is provided on the outer surface of the glass substrates 21a and 21b. Layers can also be formed directly, and in this case, productivity is improved as compared with the case where individual components are newly added, which is preferable. In the case of laminating the wave plates, a force for directly laminating the glass substrate on the optical disk side, or a laminated glass substrate may be further laminated.
- a power supply unit which is a member for supplying a voltage, which is formed on an electrode on a substrate that sandwiches the anisotropic optical medium and constitutes the phase correction element according to the present invention, will be described.
- the resistivity of the power supply unit becomes equipotential within the power supply unit when a voltage is applied that is extremely small compared to the resistivity of the electrode.
- one (one surface) electrode is formed for each of the pair of substrates, and a total of two (two surfaces) electrodes are formed.
- the electrodes are preferably formed on opposing surfaces of the pair of substrates. Examples of these electrode and power supply units include the following.
- each power supply part may be formed at a position facing between the two electrodes. It may be formed at a position that does not face.
- one electrode is a continuous electrode and the other is a continuous electrode.
- one electrode is divided into a plurality of electrodes to make a divided electrode.
- Two or more power supply sections are formed at different positions on one continuous electrode, and two or more power supply sections are formed on one of the other divided electrodes.
- Two or more power supply portions are formed at different positions on one continuous electrode, and two or more power supply portions are formed on all other divided electrodes.
- No feeder is formed on one continuous electrode, and two or more feeders are formed on all of the other multiple split electrodes, facing one feeder. Different voltages can be applied between the electrode to be supplied and the electrode facing the other power supply unit.
- both electrodes are divided into multiple electrodes, each of which is a single electrode
- (h)-Two or more power supply sections are formed on some or all of the plurality of divided electrodes, and no power supply section is formed on the other plurality of divided electrodes, facing one power supply section.
- a different voltage can be applied between the divided electrode to be applied and the divided electrode facing the other power supply unit.
- Two or more power supply portions are formed on a part or all of one of the plurality of divided electrodes, and two or more power supply portions are formed on one of the other plurality of divided electrodes.
- Two or more power supply portions are formed on some or all of the plurality of divided electrodes, and two or more power supply portions are formed on all of the other plurality of divided electrodes.
- each power supply unit functions as follows. First, an example will be described in which the electrodes on both sides are one continuous electrode. When two or more power supply sections are formed on only one of the electrodes, the electrode having only one power supply section becomes the common electrode C (equipotential), and the two or more power supply sections (SS 2, S 3 - ⁇ ⁇ ) and between, i.e. cs There cs 2, cs 3 ⁇ ⁇ 'voltage that different between is supplied.
- a different voltage between is not the opposite supplied T, and may be the shape and size of the feed portions between such S have T 2 and S 2, T 3 and S 3 are different from each other,
- the shape and size should be appropriate for the purpose. In addition, even when they face each other, their shapes and sizes may be changed as needed.
- one of the electrodes on the two surfaces is divided into a plurality of divided electrodes (U 1N U 2 , U 3 ... ), And the other is a single continuous electrode, and is divided into a plurality of feed portions (S i, S 2, if the S 3 ⁇ ⁇ ⁇ ) having, between the divided electrode and the power supply unit, U - S ⁇ l ⁇ - s 2, u 3 - s 3, ⁇
- Each of the power supply units also functions in the same manner for the other electrode modes described above.
- the number of feed sections depends on the purpose and shape, but the wavefront can be changed by the required amount if about 10 per electrode.
- phase correction element which electrically connects a power supply unit for supplying a voltage.
- phase correction element for example, two or more of the above-described power supply portions formed on electrodes on the same substrate are conductively connected on the substrate surface by a thin film resistor formed of a conductive thin film.
- the effect obtained by providing a thin film resistor will be described in detail below, taking the case of correcting spherical aberration as an example.
- FIG. 4 is a diagram showing wavefront aberration (spherical aberration) generated when the thickness of the optical disk is increased by 0.3 mm from the design value of 0.6 mm.
- wavefront aberration sinospherical aberration
- FIG. 4 shows an example in which conventional wiring is used for the electrode pattern of the phase capturing element according to the present invention, which is used for correcting the spherical aberration as described above, and has no thin film resistance.
- the hatched portion in FIG. 4 is a transparent electrode 30 formed of a high-resistance transparent conductive film, and the power supply portions 32, 33, and 34 are formed concentrically around the power supply portion 31.
- the power supply units 31 to 34 are connected to an external signal source by the wiring indicated by the thick bold line in the figure, the power supply units 31 and 34 receive the signal 1, the power supply unit 32 receives the signal 3, and the power supply unit. 3 3 is supplied with signal 2 and can apply voltage to each feed.
- FIG. 5 is an equivalent circuit diagram of the electrode pattern of the phase correction element of FIG. Points 35, 36, 37, and 38 in FIG. 5 correspond to the power supply units 31, 32, 33, and 34 shown in FIG.
- the resistance is the resistance between the power supply parts 31 and 32 caused by the transparent electrode 3 ⁇
- R 2 and R 3 are the resistances between the power supply parts 32 and 33 and the power supply parts 33 and 34. It is anti.
- the resistance of the power supply unit and the resistance of the wiring between the power supply unit and the external signal source are sufficiently smaller than the resistances R 2 and R 3 caused by the transparent electrode 30 and are ignored in the equivalent circuit.
- FIG. 3 is a diagram comparing the cutting plane passing through the center point for the relationship between the magnitude of the spherical aberration and the conductive position, aberration distribution potential distribution shape by setting the voltage V 1, V 2, V 3 appropriately It can match the shape.
- the alignment direction of the liquid crystal molecules inside the phase correction element changes continuously depending on the location by applying a voltage. Therefore, in the voltage distribution that changes continuously as described above, the orientation direction changes continuously depending on the location, and the substantial refractive index difference ⁇ of the liquid crystal birefringence is continuous. Change. Since the wavefront of the incident light shifts in phase according to the magnitude of ⁇ n, the amount of phase shift can be changed according to the magnitude of the applied voltage. Therefore, the wavefront aberration can be canceled out and corrected by applying a voltage corresponding to the generated aberration amount.
- FIG. 7 is a diagram showing an example of the electrode pattern of the phase correction element and the thin film resistor 45 (in the present invention) according to the present invention.
- the transparent electrode 40, the power supply sections 41, 42, 43, 44 and the signals 1 and 2 are the same as in FIG. 4, and the power supply section 4 2 is conductively connected to the power supply sections 41 and 44 using the thin film resistor 45 and the signal is supplied. The difference is that 1 can be applied.
- points 46, 47, 48, and 49 correspond to the power supply sections 41, 42, 43, and 44, respectively, and resistors R 2 and R 3 correspond to the power supply sections 41 and 42, 42 and 43, as in FIG.
- the resistance of the transparent electrode 40 between 43 and 44 is shown, respectively.
- R s indicates the resistance of the thin film resistor 45, and divides the voltage supplied from the signal 1 so that the point 47 has a desired voltage. Therefore, in the example using the conventional wiring, the voltage at point 47 (corresponding to point 36 in FIG. 5) is obtained from the signal 3 generated from another signal source. Since 3 is unnecessary, it can be operated with fewer signal sources than before. Voltage V 3 at the point 47 is obtained from the formula was calculated using Ohm law rule (1).
- V 3 (R 2 (Ri + R S ) VJ + R.RSV / 2 +
- the above voltage V by the signal 1 in the configuration, a was set voltage of divide point 47, may divide the voltage V 2 by the signal 2 min with the same principle.
- the electrodes, the power supply section, the resistance values of the thin film resistors, and the materials are described. It is preferable that the ratio P T Bruno P S of the sheet resistance P T of the electrode material forming the sheet resistance P s and the electrode power supply section material forming the feed unit 1 0 0 0 or more.
- P T / ps is small, a relatively large current also flows through the electrode, and a voltage drop occurs in the power supply unit in contact with the electrode, which may make it difficult to obtain a desired voltage distribution. Therefore, as the sheet resistance of the electrode material is higher than the material of the power supply portion, the potential is easily changed continuously between adjacent power supply portions, and a desired potential distribution can be obtained.
- Setting p ⁇ / ⁇ s to 100 0 0 or more is a standard for satisfying this condition.
- the feeding portion materials include copper, gold, aluminum, metal material such as chromium is preferable in view of conductivity • durability, if 1 0 one 8 ⁇ 1 0- 7 ⁇ ⁇ about m specific resistance at room temperature metal Other materials may be used.
- a transparent conductive film such as an ITO film can be used, and it is preferable because a light-shielding portion is eliminated as compared with a case where a metal material is used, so that light transmittance is increased.
- the transparent conductive film has a higher specific resistance than the metal film, it is necessary to increase the film thickness in order to reduce the sheet resistance.
- the wiring material on the electrode lead-out part 27 (see Fig. 2) for applying a voltage to the power supply part from an external phase correction element control circuit may be a transparent conductive film such as an ITO film, or a metal such as chromium or nickel. It may be a membrane. In particular, in the case of a metal such as nickel which can be connected by solder, an external signal line can be easily connected by solder, which is preferable.
- the electrode material must be transparent and have a higher sheet resistance than the material of the power supply. It is necessary. It is preferable to use an ITO film or the like which is a transparent conductive film. The higher the sheet resistance of the ITO film is, the better it is. Further, 1 since the better to more than k Omegazeta port possible p s to about 1 Omega / mouth, preferably from easier to produce such a film thickness of the power supply unit can be reduced.
- the 0 0 0 film 0 0 3 film has a high specific resistance and good etching properties, and is excellent in light transmittance and durability. It is a suitable material.
- the transmittance of the film changes, so that the addition amount is preferably set to 1 to 10% by mass. Even when gallium and silicon are added together, the transmittance of the film changes, so that the total added amount is preferably 1 to 20% by mass.
- the material of the thin film resistor it is necessary to use a material having R 3 that satisfies the relationship of the equation (1).
- R 3 a material having R 3 that satisfies the relationship of the equation (1).
- the shape and size of the power supply unit will be described. It is preferable that the shape and size of the power supply unit be changed according to the situation as described above. That is, the change in the wavefront generated by the phase correction element depends on the shape and size of the power supply unit, and may be changed according to the type of the wavefront aberration to be corrected and the wavefront shape to be generated.
- the wavefront aberration includes coma, spherical aberration, and astigmatism.
- coma is an aberration generated by tilting an optical disc, and passes around a straight line passing through the center of the incident light beam on the phase correction element and parallel to the element surface and parallel to the rotation direction of the optical disc. It has a shape that overlaps when rotated by 80 °. Therefore, the power supply unit is preferably arranged so as to be symmetrical with respect to the above-mentioned parallel straight line. Specifically, for example, a generally rectangular or linear power supply section is provided at the center of one continuous electrode, and a power supply section (such as an arc) at the periphery of the electrode is provided at the periphery. . Then, the power supply units are arranged so that those power supply units are symmetric with respect to the above-described straight line. It is preferable to dispose the power supply section in this manner because coma aberration can be most effectively corrected.
- the plurality of power supply units are each annular and are arranged concentrically with each other.
- the ratio of the radius of one of the toroids to the luminous flux radius of the light emitted from the light source passing through the phase capturing element is 0.65 to 0.85, and It is preferable that the ratio of the radii of another torus different from the above is 0.2 to 0.4.
- the ratio of the radius of the torus means the average value of the ratio of the inner radius to the ratio of the outer radius.
- one toroid that is a power supply unit has an optical axis.
- area (area C) which is formed in the area A with the center of the circle and surrounded by a circle with a radius ratio of 0.2 and a circle with a radius of 0.4 (area C)
- the accuracy is extremely high and spherical aberration is corrected. It is preferable to provide a feeding part of one different torus with its optical axis and center aligned.
- the circle with the radius ratio of 0.65 and the circle with the radius of 0.85 is smaller than the region A,
- a toric can be added to a region where the probability that the maximum value of the spherical aberration exists is high, and that another toric can be added so that the spherical aberration can be finely adjusted.
- the feeding part of the torus is further positioned in the region near the optical axis (region B) including the optical axis and having a radius ratio smaller than 0.2. It is more preferable to provide them together so that the spherical aberration can be finely adjusted.
- the electrode is a divided electrode and the area B is divided from other areas (area A, the same area, etc.), it is possible to correct the spherical aberration with extremely high accuracy as described above, and it is sufficient. It is.
- a power feeding portion having a different shape for each of a pair of continuous electrodes, so that one electrode corrects coma aberration and the other electrode corrects spherical aberration.
- one electrode corrects coma aberration and the other electrode corrects spherical aberration.
- one of a pair of electrodes as one continuous electrode having a power supply unit and the other as a divided electrode divided into a plurality of electrodes, both a continuous aberration distribution and a stepwise aberration distribution are generated. It can also be done.
- Wavefront aberrations such as coma, spherical aberration, and astigmatism are generated by the optical head device as a system. Therefore, by incorporating the phase correction element of the present invention into the optical head device, the wavefront aberration is obtained. Can be effectively corrected.
- the phase correction element in the present invention has a function of changing the wavefront shape of transmitted light, it can be used for other purposes, such as changing the focal position of light as well as correcting the wavefront aberration, based on the same principle.
- it can be used to change the focal position of transmitted light simply by changing the optical magnification, or to change the traveling direction of light by tilting the transmitted wavefront and emitting it.
- the shape, number, position, method of dividing the electrodes, and the like of the power supply unit may be appropriately set according to a desired change in the wavefront.
- the electrode provided with the power supply unit is divided into a plurality of divided electrodes, and each divided electrode is provided with one or more power supply units. It is preferable that the above is conductively connected by a thin film resistor. If two or more power supply units to be conductively connected are power supply units on the same split electrode, a continuous voltage distribution can be generated, and if power supply units on different split electrodes are non-continuous, It can be used when distribution is required and is preferred.
- the optical head device can be operated with a smaller number of external signal sources by connecting two or more power supply units conductively using thin film resistors. Also, in the case of a configuration in which one of the connection destinations of the thin film resistor is a power supply unit and the other is a split electrode having no power supply unit! /, The same effect can be obtained. Examples are shown below.
- the optical head device of this example includes a phase correction element that captures coma generated by tilting the optical disk, and this phase correction element can be used even if the objective lens shifts in the radial direction of the optical disk.
- the feature is that an appropriate phase (wavefront) distribution for correction can be obtained without integrally driving the objective lens and the phase correction element.
- the optical head device incorporating the phase correction element in this example is shown in FIG. FIG. 9 shows the electrode pattern of the phase correction element in this example.
- the hatched portion is a transparent electrode 60, which is a continuous electrode formed of an ITO film, and the thick line portion is a metal as a power supply portion.
- Electrodes 61 to 66 are connected to a signal source (not shown) outside the phase correction element by a metal wiring 67 for power supply, and can supply an arbitrary voltage by signals 1 to 6, respectively.
- the width of the metal electrodes 62 to 65 is 100 ⁇ m and the length is 1.5 mm.
- the width of the metal electrodes 61 and 66 is 100 / zm and the length of the arc is 6 mm.
- the electrode pattern was formed as follows. First, an ITO film was formed on a glass substrate by a sputtering method, and then patterned using a photolithography technique. At this time, the ITO film around the metal wiring portion was removed by etching so that the metal electrode portion left the ITO film, and the metal wiring portion was insulated from the transparent electrode 60. Next, the metal electrode and metal wiring of Fig. 9 were formed by the lift-off method.
- the metal electrode material used here was aluminum.
- the area shown by the broken line in FIG. 9 is the effective pupil through which the light beam passes when there is no shift of the objective lens, and the shape of the electrode is along the shift direction of the objective lens (left-right direction in the figure). It is longer by the amount of shift.
- phase correction element of this example a phase change for canceling the wavefront aberration was obtained as follows.
- FIG. 11 shows the phase change generated by the phase correction element when there is no lens shift.
- the phase change is expressed in units of nm.
- each of the left half region in the opposite direction to the 140 nm (almost rectangular portion) and the 140 nm (peripheral portion of the effective pupil) A phase change occurs with the magnitude of the numerical value, and the curve between these regions is a contour line.
- one contour line represents about 47 nm.
- the electrode facing the electrode having the six power supply portions has a single power supply portion composed of one continuous transparent electrode, and is always at the OV potential.
- the high-resistance transparent electrode 60 is electrically connected to the metal electrodes 61 to 66 having different potentials, the potential varies depending on the location and a uniform voltage distribution is generated.
- the orientation direction of the liquid crystal molecules inside the phase correction element changes due to the application of a voltage, and the orientation direction varies according to the non-uniform voltage distribution described above.
- the phase change ⁇ n Depends on location.
- d is the distance between the substrates of the liquid crystal cell
- ⁇ ⁇ is the substantial difference in the refractive index at each point of the liquid crystal cell, which changes according to the applied voltage.
- Fig. 12 shows the phase change caused by the phase correction element to correct the wavefront aberration (mainly coma aberration) generated at a lens shift of 0.3 mm and a disc tilt angle of 1 °.
- 1.5 V is supplied to the electrode 61, 2.6 V to the electrode 63, 1.8 V to the electrode 65, and 2.7 V to the electrode 66, and is supplied to the electrodes 62 and 64.
- Set signals 1 to 6 so that no voltage is supplied.
- the effective pupil on the phase correction element moves rightward according to the shift of the lens.
- the maximum position of the phase change is also determined by the lens position.
- the wavefront aberration shown in FIG. 10 could be corrected because it can move so as to follow the shift.
- 1.5 V is applied to the electrode 61.
- Signals 1 to 6 were set so that 2.4 V was supplied to electrode 62, 1.6 V to electrode 64, 2.7 V to electrode 66, and no voltage was supplied to electrode 6665. As in the right direction, the wavefront aberration could be corrected.
- the maximum value of the lens shift amount in this example is 0.4 mm, and the distance between the metal electrodes 62 and 63 and the metal electrode 6 is adjusted so that the wavefront aberration can be corrected even when the lens shift amount is the maximum value.
- the distance between 4, 65 was 0.6 mm. This interval is preferably set to about 70 to 80% of the lens shift amount to be considered.
- the voltage supplied to the metal electrodes 62 to 65 may be changed as appropriate, and the tilt and lens shift of the optical disk are continuously performed. Correction of wavefront aberration could be performed.
- the optical head device in this example even when the objective moves, the coma aberration generated due to the tilt of the optical disk can be satisfactorily corrected.
- the conventional phase correction element with split electrodes light scattering in the split area was suppressed, resulting in a 3% improvement in transmittance.
- the optical head device of the present example includes a phase correction element that corrects spherical aberration caused by uneven thickness of an optical disk. If the thickness of the objective lens deviates from the design value, spherical aberration will occur and the signal reading accuracy will decrease.
- a phase correction element for correcting this spherical aberration was incorporated as the phase correction element 4 of the optical head device in FIG. However, the phase correction element control circuit 10 is improved for the phase correction element of this example.
- phase correction element of this example is the same as that shown in FIG. 2, and only the electrode patterns described below are different. Therefore, the same manufacturing method and constituent materials as those of Example 1 were used for the phase correction element.
- the principle of correcting spherical aberration by the phase correction element of the present example will be described below.
- Figure 3 shows an optical system with an objective lens with an NA of 0.65 and a light source wavelength of 0.4 ⁇ , where the optical disc thickness is 0.33 mm thicker than the designed value of 0.6 mm. It is a figure which shows the wavefront aberration (spherical aberration) which arises.
- the optical disk is thicker than the design value, the phase of the center of the effective pupil and the phase of the peripheral portion of the effective pupil are advanced in the middle part sandwiched between them, and when the thickness is thin, the phase is delayed.
- Fig. 13 shows the electrode pattern of the phase correction element in this example.
- the hatched portions in FIG. 13 are one continuous transparent electrode 80 formed of the ITO film, and the thick line portions are the metal electrodes 81 to 83.
- the metal electrodes 81 to 83 are connected to external signal sources by metal wirings 84, respectively, and can supply any voltage from signals 1 to 3, respectively.
- the material and manufacturing method of the electrode pattern are the same as those in Example 1 as described above.
- the transparent electrode 80 around the metal wiring portions connected to the metal electrodes 82 and 83 is removed by etching. .
- the outer diameters of the metal electrodes 81 and 82 in FIG. 13 were 4 mm and 3 mm, respectively, the width was 100 / zm, and the diameter of the metal electrode 83 was 200 im.
- the electrode facing the electrode with three power supply parts is composed of one continuous transparent electrode with one power supply part, and always has a potential of 0 V. ing.
- FIG. 14 shows a phase change generated by the phase correction element.
- FIG. 14 also shows the phase change in units of nm in the same manner as FIG. 11, and the center part and the outer part of the circle have a phase change of 0 nm and a region where the phase change is 100 nm is in the middle part.
- a plurality of solid circles are contour lines, and one contour line represents 20 nm inside the region of -100 nm, and approximately 60 nm outside.
- the transparent electrode 80 generates a voltage distribution according to the voltage of each metal electrode. As described above, as a result of the voltage distribution causing a substantial refractive index distribution of the liquid crystal, the phase correction element can generate a concentric phase change shown in FIG.
- the phase change generated by the phase correction element also has a form in which the sign of FIG. 14 is reversed, so that the spherical aberration can be canceled.
- the optical head device of this example As described above, by using the optical head device of this example, spherical aberration caused by unevenness in the thickness of the optical disk was successfully corrected. In addition, compared to the conventional phase correction element with split electrodes, light scattering in the split area was suppressed, resulting in a 3% improvement in transmittance. Further, since the optical head device can be operated with a smaller number of external signal sources than before, an optical head device can be manufactured at low cost.
- the optical head device of this example includes a phase correction element that corrects both spherical aberration caused by uneven thickness of the optical disc and coma caused by tilt of the optical disc.
- This phase correction element was incorporated as the phase correction element 4 of the optical head device in FIG.
- the phase correction element control circuit 10 is improved for the phase correction element of this example.
- the element structure of the phase correction element of this example is the same as that shown in FIG. 2, and the electrode patterns and materials described below are different.
- the electrode pattern similar to that of Example 2 shown in FIG. 13 is formed as the electrode 24a in FIG. 2, and the spherical aberration can be corrected.
- a GZO film was used as a material for one continuous transparent electrode 80 in FIG. 13, and chromium was used for the metal electrodes 8:! To 83.
- the metal electrodes 81 and 82 are annular bodies and are arranged concentrically with each other.
- the sheet resistance of the GZO film is 100 k ⁇ and the sheet resistance of chromium is 1 ⁇ .
- the divided electrodes 91-95 are formed as shown in FIG. 15, so that coma aberration can be corrected.
- an ITO film was formed on a glass substrate by sputtering, and a pattern was formed using photolithography and etching techniques.
- the bold line in Fig. 15 shows the gap between the split electrodes. In this part, no voltage was applied because the ITO film was removed by the etching technique.
- the width of the gap between the divided electrodes was 5 ⁇ m.
- a rectangular AC wave signal having a frequency of lk Hz and a duty ratio of 12 was applied as signals to be input to the divided electrodes 91 to 95 and the metal electrodes 81 to 83.
- the phase of the AC signal is aligned in the split electrodes 91-95 and the metal electrodes 81-83, but the phase is shifted 180 ° between the split electrodes 91-95 and the metal electrodes 81-83. I have.
- the effective voltage V nm (E) for driving the liquid crystal molecules 28 is [V n (M) ⁇ V m (D)] rms , and the rms of the difference between V n (M) and V m (D) is obtained.
- Value the square root of the time average of the square of the amplitude.
- the frequency and duty ratio are 12 and the phase is 180. Since it is a shifted rectangular AC wave, the effective voltage V nm (E) simply matches the absolute value of the difference
- the applied voltages V n (M) and V m (D) differ depending on the aberration distribution to be corrected.
- a fixed voltage is applied to the metal electrodes 81 and 83 for spherical aberration correction, and a voltage corresponding to the thickness unevenness of the optical disk is applied to the metal electrode 82.
- V 2 (M) 0.5 to 1.5 V was applied.
- the effective voltage V nm (E) is always 2 V rms for the metal electrodes 81 and 83, and changes in the range of 1.5 to 2.5 V for the metal electrode 81 according to the thickness unevenness of the optical disk. .
- the effective voltage also changed continuously due to the continuous potential distribution generated between the metal electrodes as in Example 2, so that a phase change as shown in FIG. 14 could be obtained.
- the effective voltage V nm (E) is always 2 V rms at the split electrode 93, and 1.5 to 2.5 at the split electrodes 91, 92, 94, and 95 depending on the tilt amount of the optical disk. Changes up to 5 V. As a result, a potential distribution equal to the electrode pattern shown in FIG. 15 was generated, and a similar phase change was obtained.
- a fixed voltage of 1 V is applied to the dividing electrode 93 and the metal electrodes 81 and 83, and the dividing electrodes 91, 92, 94 and 95 are 0.5 in accordance with the tilt amount of the optical disk.
- a voltage of 0.5 to 1.5 V is applied to the metal electrode 82 in accordance with the thickness unevenness of the optical disk.
- the electrodes for coma aberration correction were divided electrodes, but in contrast to this, as in Example 1, one continuous electrode for coma aberration was used as a metal electrode serving as a power supply unit, and further for spherical aberration.
- the electrode may be a concentric divided electrode.
- the electrode patterns for coma correction in the radial (radius) direction and coma correction in the tangential (tangential) direction of the optical disk may be combined in pairs, and spherical aberration and astigmatism, and coma and astigmatism may be combined. May be paired with each other. In each case, two types of aberration and wavefront change can be corrected simultaneously.
- both coma caused by the tilt of the optical disk and spherical aberration caused by the thickness unevenness of the optical disk could be simultaneously corrected.
- light scattering in the divided area was suppressed, resulting in a 5% improvement in transmittance.
- the optical head device could be manufactured at low cost because it could be operated with a smaller number of external signal sources than before.
- the optical head device of this example corrects spherical aberration caused by uneven thickness of the optical disk.
- Phase correction element This phase correction element was incorporated as the phase correction element 4 of the optical head device in FIG. However, the phase correction element control circuit 10 is improved for the phase correction element of this example.
- phase correction element of this example is the same as that shown in FIG. 2, and only the electrode patterns described below are different. Therefore, the same manufacturing method and constituent materials as those of Example 1 were used for the phase correction element.
- the electrode 24a in FIG. 2 includes divided electrodes 101, 102, and 103, and power supply sections 104 and 105 formed on the divided electrode 103.
- the material of the divided electrodes 101 to: I03 is a GZS film
- the material of the power supply units 104 and 105 is an ITO film.
- GZS and ITO sheet resistances are 10 ⁇ 0 k ⁇ noro and 10 k ⁇
- an ITO film was formed on a glass substrate by a sputtering method, and power supply units 104 and 105 were formed by using a photolithography and etching technique.
- an ITO film is formed by a sputtering method, and the split electrodes 10 :! ⁇ 103 were formed.
- the division interval was 5 m as in Example 3.
- Signals 1 to 4 in FIG. 16 are signals applied to the divided electrodes 101 and 102 and the power supply units 104 and 105, respectively, and are generated by the phase correction element control circuit 10.
- the wiring for signal 1 is illustrated as passing through the split electrode 102.
- the split electrode 102 is patterned so that both are insulated by etching.
- the electrode 24b in FIG. 2 was a single continuous electrode formed of an ITO film.
- the applied signal is a rectangular AC wave signal with a frequency of 1 kHz and a duty ratio of 1/2, and the signal phase is the same for all of the split electrodes 101 and 102 and the power supply units 104 and 105. ing.
- the opposing electrode 24b is fixed to the common voltage (for example, 0V) of the phase correction element control circuit.
- the potential distribution of the entire phase correction element generated as described above is a step-like distribution in which the potential is constant inside divided electrodes 101 and 102, and a distribution that continuously changes inside divided electrode 103. .
- As a result of such a phase change it was possible to correct spherical aberration and obtain a good reproduction signal even on an optical disc having uneven thickness.
- the optical head device can be operated with a smaller number of external signal sources than in the past, and the optical head device can be manufactured at low cost.
- the number of split electrodes is reduced as compared with the conventional complementary element, so light scattering in the split area is reduced and the transmittance is improved by 3%. did.
- the optical head device of this example includes a phase correction element that corrects spherical aberration caused by uneven thickness of an optical disk. If the thickness of the optical disc deviates from the designed value, the objective lens generates spherical aberration, and the signal reading accuracy is reduced.
- the phase correction element for correcting this spherical aberration was incorporated as the phase correction element 4 of the optical head device in FIG. However, the phase correction element control circuit 10 is improved for the phase correction element of this example.
- the element structure of the phase correction element of this example is the same as that shown in FIG.
- the principle of correcting spherical aberration by the phase correction element of this example will be described below.
- the NA of the objective lens in the optical head device of this example was 0.95, and the wavelength of the light source was 0.4 ⁇ m. This occurs when the thickness of the optical disk is 0.03 mm thicker than the design value of 0.6 mm.
- Wavefront aberration spherical aberration
- the electrode pattern of the phase correction element in this example is as shown in FIG. 7, and the equivalent circuit is as shown in FIG.
- the hatched portions in FIG. 7 are the transparent electrodes 40 formed of a GZO film, and the thick line portions (annular bodies) are the power supply portions 41, 42, 43, and 44 formed by etching a chromium thin film.
- the power supply is connected to signals 1 and 2 as external signal sources by wiring of the same chromium thin film formed on the same substrate surface.
- the power supply section 42 is connected to the signal 1 by a thin film resistor 45 formed on the same substrate surface.
- Feeders 41 to 44 have a width of 100 m, feeders 42, 43, and 44 have diameters of 0.5, 1.5, and 2.2 mm, respectively, and feeder 41 has a circular shape with a diameter of 50 ⁇ .
- the patterns of the electrodes and the power supply section were formed as follows. First, a chromium film was deposited on a glass substrate by a sputtering method, and unnecessary portions were removed by an etching technique to form a power supply portion and wiring. Next, after depositing an ITO film by a sputtering method, a thin film resistor 45 was formed by an etching technique.
- a GZO film was deposited by a sputtering method, and a transparent electrode 40 was formed by an etching technique.
- the sheet resistance of each part was 1 ⁇ for the feeder, 100 k ⁇ for the electrode, and 300 ⁇ for the thin-film resistance.
- the electrode resistance values between the power supply units corresponding to the resistances R ⁇ R ⁇ and R 3 in Fig. 8 were 50, 28, and 20 kQ, respectively.
- a thin film resistor (linear resistor) with a resistance value of 5.48 was formed by bending a line with a width of 30 jum and a length of 55 mm three times.
- FIG. 7 shows the phase change generated by the phase correction element in nm units. Same as Example 2.
- the phase change in the middle region is about 1 O Onm.
- a plurality of solid circles are contour lines, and one contour line represents 20 nm inside the intermediate region of —100 nm, and approximately 30 nm outside.
- a voltage distribution is generated in the transparent electrode 40 (FIG. 7) according to the voltage of the power supply unit.
- the voltage distribution in the transparent electrode 40 shown in FIG. 7 causes a substantial refractive index distribution of the liquid crystal.
- the phase correction element can generate concentric phase changes shown in FIG.
- the optical disk thickness is thin by 0.03 mm, 2.
- OV is applied to the power supply units 41 and 44 and 2.3
- the phase change generated by the phase correction element becomes a form in which the sign of FIG. 14 is reversed, so that spherical aberration can be canceled.
- the spherical aberration shown in FIG. 14 can be corrected by providing the thin film resistor 45 so that a desired voltage can be obtained and supplying an appropriate voltage to the power supply units 41, 43, and 44.
- the optical head device of the present example includes a phase correction element that corrects both spherical aberration caused by uneven thickness of an optical disc and coma caused by tilt of the optical disc.
- This phase correction element was incorporated as the phase correction element 4 of the optical head device in FIG.
- the phase correction element control circuit 10 is improved for the phase correction element of the present example.
- the element structure of the phase correction element of this example is the same as that shown in FIG. 2, and the electrode patterns and materials described below are different.
- the electrode 24a in FIG. 2 is composed of divided electrodes 51, 52, and 55, feed portions 53 and 54 formed on the divided electrode 55, and thin film resistors 56 and 57.
- the thin film resistors 56 and 57 are schematically shown, and the actual shape is linear or the like so as to obtain a desired resistance value.
- the material of the split electrodes 51, 52, and 55 was a GZS film, and the material of the power supply parts 53 and 54 and the thin-film resistors 56 and 57 were an ITO film.
- the sheet resistances of the GZS film and the ITO film were 1000 and 10 kQZ, respectively.
- an ITO film was formed on a glass substrate by a sputtering method, and power supply portions 53 and 54 and thin film resistors 56 and 57 were formed by using a photolithography technique and an etching technique. Feeding
- the width of the parts 53 and 54 was 50 ⁇ .
- a GZS film was formed by a sputtering method, and divided electrodes 51, 52, and 55 were formed by using a photolithography technique and an etching technique.
- the division interval between the division electrodes was 5 ⁇ m.
- Signals 1 and 2 in FIG. 17 are signals applied to the split electrode 51, the power supply unit 54, and the power supply unit 53, respectively, and are generated by the phase correction element control circuit 10.
- the electrode 24b is formed with divided electrodes 91 to 95 as shown in FIG. 15 similarly to Example 3, and can correct coma aberration.
- an ITO film was formed on a glass substrate by a sputtering method, and a pattern was formed by photolithography and etching.
- the thick line in FIG. 15 indicates the gap between the divided electrodes, and no voltage is applied to this portion because the ITO film has been removed by etching.
- the width of the gap between the divided electrodes was 5 m.
- the output waveform of the phase correction element control circuit is a rectangular AC wave signal having a frequency of l kHz and a duty ratio of 1 to 2, and the AC signal has the same phase in the electrodes 24a and 24b, and the electrode 24a And the electrode 24b have opposite phases (180 ° phase difference).
- V nm (E) for driving the liquid crystal molecules 28 is [V n (S) ⁇ V m (D)] rms , and the rms of the difference between V n (S) and V m (D) Value (the square root of the time average of the square of the amplitude).
- the effective voltage V nm (E) is simply the absolute value of the difference IV n (S) — V m (D) I Matches.
- the applied voltages V n (S) and V m (D) differ depending on the aberration distribution to be corrected.
- the effective voltage also changes continuously due to the continuous potential distribution generated between the metal electrodes as in Example 5, so that a phase change according to the electrode pattern can be obtained.
- a fixed voltage of 1 V was applied to the split electrode 93 for the coma aberration correcting electrode 24b.
- the effective voltage V nm (E) is always 2 V rms at the split electrode 93, and ranges from 1.5 to 2.5 V ras at the split electrodes 91, 92, 94, and 95, depending on the tilt amount of the optical disk. To change. As a result, a potential distribution equal to the shape of the electrode pattern shown in FIG. 15 was generated, and a phase change could be obtained.
- a fixed voltage of 1 V is applied to the split electrode 93 and the split electrode 51, and the power supply section 54, and the split electrodes 91, 92, 94, and 95 are set to 0.5 to 1.5 V in accordance with the tilt amount of the optical disk.
- 0.5 to 1.5 V is applied to the voltages of the signals 1 and 2 in FIG. 17 according to the thickness unevenness of the optical disk.
- the electrode for coma aberration correction is a divided electrode.
- the electrode for coma aberration is a metal electrode that is a power supply unit
- the electrode for spherical aberration is a concentric circle divided electrode.
- a pair of electrode patterns for radial coma aberration correction and tangential coma correction may be formed on each substrate, and the electrode patterns for correcting spherical aberration and astigmatism, and coma and astigmatism, respectively, may be formed. You can pair it. I Even in the case of displacement, two types of aberration and wavefront change can be corrected simultaneously. Industrial applicability
- the optical head device of the present invention by providing two or more power supply portions to at least one of the electrodes formed on each of the pair of substrates constituting the phase correction element, since the phase correction element can generate a continuous phase (wavefront) change in the light emitted from the light source, it is possible to efficiently correct the wavefront aberration generated due to the tilt of the optical disk, the unevenness of the optical disk thickness, etc. Small and good signal light can be obtained.
- the same aberration correction performance can be exerted with fewer signal sources than before.
- the wavefront aberration (mainly coma aberration) can be corrected without driving the phase compensating element integrally with the objective lens. Furthermore, spherical aberration caused by uneven thickness of the optical disk can be corrected.
- the effect of the present invention does not cause a large difference in the effect whether the electrode formed on the substrate is a single continuous electrode or divided into a plurality of electrodes as long as the requirements of the present invention are satisfied .
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- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Nonlinear Science (AREA)
- Geometry (AREA)
- Mathematical Physics (AREA)
- General Physics & Mathematics (AREA)
- Optical Head (AREA)
- Glass Compositions (AREA)
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT00956819T ATE452404T1 (de) | 1999-09-02 | 2000-08-30 | Optischer kopf |
EP00956819A EP1136993B1 (en) | 1999-09-02 | 2000-08-30 | Optical head |
US09/830,849 US7054253B1 (en) | 1999-09-02 | 2000-08-30 | Optical head |
DE60043531T DE60043531D1 (de) | 1999-09-02 | 2000-08-30 | Optischer kopf |
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP24928599 | 1999-09-02 | ||
JP11/249285 | 1999-09-02 | ||
JP2000196926A JP4915028B2 (ja) | 1999-09-02 | 2000-06-29 | 光ヘッド装置 |
JP2000/196926 | 2000-06-29 | ||
JP2000/245457 | 2000-08-14 | ||
JP2000245457A JP5005850B2 (ja) | 2000-08-14 | 2000-08-14 | 光ヘッド装置 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2001018801A1 true WO2001018801A1 (fr) | 2001-03-15 |
Family
ID=27333813
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2000/005889 WO2001018801A1 (fr) | 1999-09-02 | 2000-08-30 | Tete optique |
Country Status (6)
Country | Link |
---|---|
US (1) | US7054253B1 (ja) |
EP (1) | EP1136993B1 (ja) |
KR (1) | KR100740481B1 (ja) |
AT (1) | ATE452404T1 (ja) |
DE (1) | DE60043531D1 (ja) |
WO (1) | WO2001018801A1 (ja) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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US7427490B2 (en) | 2001-08-20 | 2008-09-23 | Biosite Incorporated | Diagnostic markers of stroke and cerebral injury and methods of use thereof |
US7839458B2 (en) | 2005-03-03 | 2010-11-23 | Citizen Holdings Co., Ltd. | Liquid crystal optical element having grouped concentric electrodes |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6690500B2 (en) * | 2000-06-30 | 2004-02-10 | Pioneer Corporation | Aberration correction apparatus and method |
JP3844460B2 (ja) * | 2002-08-05 | 2006-11-15 | パイオニア株式会社 | 空間光変調器 |
CN1685411B (zh) * | 2002-11-08 | 2010-06-09 | 西铁城控股株式会社 | 液晶光学元件和光学装置 |
JPWO2004079436A1 (ja) * | 2003-03-07 | 2006-06-08 | 旭硝子株式会社 | 光減衰器および光ヘッド装置 |
JP2005071424A (ja) * | 2003-08-28 | 2005-03-17 | Pioneer Electronic Corp | 収差補正装置および光学式記録媒体再生装置 |
US7406007B2 (en) * | 2003-09-02 | 2008-07-29 | Matsushita Electric Industrial Co., Ltd. | Optical disc apparatus and spherical aberration correction controlling apparatus |
JP2005122828A (ja) * | 2003-10-16 | 2005-05-12 | Pioneer Electronic Corp | 光ピックアップ装置および光学記録媒体再生装置 |
JP4300138B2 (ja) * | 2004-03-09 | 2009-07-22 | パイオニア株式会社 | 収差補正装置、並びに光ピックアップの制御装置、制御方法及び制御プログラム |
JP2006031771A (ja) * | 2004-07-13 | 2006-02-02 | Pioneer Electronic Corp | 収差補正素子、光ピックアップ及び情報機器 |
JP4215011B2 (ja) * | 2004-09-27 | 2009-01-28 | ソニー株式会社 | 光ピックアップ及びこれを用いた光ディスク装置 |
JP4609301B2 (ja) * | 2005-12-14 | 2011-01-12 | 船井電機株式会社 | 光ピックアップ装置 |
JP5452542B2 (ja) * | 2011-04-21 | 2014-03-26 | 株式会社日立メディアエレクトロニクス | 光ピックアップ装置および光ディスク装置 |
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- 2000-08-30 KR KR1020017005487A patent/KR100740481B1/ko not_active IP Right Cessation
- 2000-08-30 WO PCT/JP2000/005889 patent/WO2001018801A1/ja active Application Filing
- 2000-08-30 AT AT00956819T patent/ATE452404T1/de not_active IP Right Cessation
- 2000-08-30 US US09/830,849 patent/US7054253B1/en not_active Expired - Fee Related
- 2000-08-30 EP EP00956819A patent/EP1136993B1/en not_active Expired - Lifetime
- 2000-08-30 DE DE60043531T patent/DE60043531D1/de not_active Expired - Lifetime
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JPH0874033A (ja) * | 1994-09-02 | 1996-03-19 | Asahi Glass Co Ltd | 液晶表示用電極 |
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JPH10188332A (ja) * | 1996-07-23 | 1998-07-21 | Asahi Glass Co Ltd | 光ヘッド装置 |
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US7427490B2 (en) | 2001-08-20 | 2008-09-23 | Biosite Incorporated | Diagnostic markers of stroke and cerebral injury and methods of use thereof |
US7839458B2 (en) | 2005-03-03 | 2010-11-23 | Citizen Holdings Co., Ltd. | Liquid crystal optical element having grouped concentric electrodes |
Also Published As
Publication number | Publication date |
---|---|
US7054253B1 (en) | 2006-05-30 |
EP1136993A4 (en) | 2002-08-07 |
ATE452404T1 (de) | 2010-01-15 |
EP1136993A1 (en) | 2001-09-26 |
DE60043531D1 (de) | 2010-01-28 |
EP1136993B1 (en) | 2009-12-16 |
KR100740481B1 (ko) | 2007-07-19 |
KR20010099774A (ko) | 2001-11-09 |
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