US5594713A — Optical pickup head apparatus

Claim 1

Independent Claim 290 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives said linearly polarized light beam emitted from said radiation light source, and converges the linearly polarized light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which is constituted by a pair of transparent substrates, a liquid crystal sandwiched between these transparent substrates, and a pair of transparent electrodes disposed between the liquid crystal and the transparent substrates, either of said transparent electrodes being formed with a hologram pattern; one of said two transparent substrates constituting the liquid crystal hologram being made by a dielectric substrate serving as one component of a Faraday rotator which rotates a polarized direction of said light beam by 45 degrees in a forward optical path leading from said radiation light source to said information medium and, further, rotates the polarized direction of said light beam by 45 degrees in a backward optical path leading from said information medium to said photodetector units; said liquid crystal hologram being applied a voltage in a reading-out operation of information signal higher than a voltage in a writing-in operation of the information signal, so that said light beam reflected from the information medium is diffracted in the liquid crystal hologram to generate ±1-order diffraction light beams; and said photodetectors sensing both of light quantities of said ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a subtraction between signals representing said light quantities so as to obtain the information signal.

Claim 2

Dependent Claim 290 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives said linearly polarized light beam emitted from said radiation light source, and converges the linearly polarized light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which is constituted by a pair of transparent substrates, a liquid crystal sandwiched between these transparent substrates, and a pair of transparent electrodes disposed between the liquid crystal and the transparent substrates, either of said transparent electrodes being formed with a hologram pattern; one of said two transparent substrates constituting the liquid crystal hologram being made by a dielectric substrate serving as one component of a Faraday rotator which rotates a polarized direction of said light beam by 45 degrees in a forward optical path leading from said radiation light source to said information medium and, further, rotates the polarized direction of said light beam by 45 degrees in a backward optical path leading from said information medium to said photodetector units; said liquid crystal hologram being applied a voltage in a reading-out operation of information signal higher than a voltage in a writing-in operation of the information signal, so that said light beam reflected from the information medium is diffracted in the liquid crystal hologram to generate ±1-order diffraction light beams; and said photodetectors sensing both of light quantities of said ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a subtraction between signals representing said light quantities so as to obtain the information signal.

Claim 3

Dependent Claim 217 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives a light beam emitted from said radiation light source, and converges the light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which includes a liquid crystal of which a molecular axis is uniformly aligned in parallel to a substrate of said liquid crystal; said liquid crystal hologram having a transparent substrate located closer to said information medium, said transparent substrate being made by a quarter wavelength plate which converts said linearly polarized light beam into a circular polarized light beam in a forward optical path leading from said radiation light source to said information medium and, to the contrary, restores thus converted circular polarized light beam into a linearly polarized light beam in a backward optical path leading from said information medium to said photodetector units; and said photodetector units sensing light quantities of ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a summation of signals representing said light quantities so as to obtain an information signal.

Claim 4

Dependent Claim 217 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives a light beam emitted from said radiation light source, and converges the light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which includes a liquid crystal of which a molecular axis is uniformly aligned in parallel to a substrate of said liquid crystal; said liquid crystal hologram having a transparent substrate located closer to said information medium, said transparent substrate being made by a quarter wavelength plate which converts said linearly polarized light beam into a circular polarized light beam in a forward optical path leading from said radiation light source to said information medium and, to the contrary, restores thus converted circular polarized light beam into a linearly polarized light beam in a backward optical path leading from said information medium to said photodetector units; and said photodetector units sensing light quantities of ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a summation of signals representing said light quantities so as to obtain an information signal.

Claim 5

Dependent Claim 197 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives the linearly polarized light beam emitted from said radiation light source, and converges the linearly polarized light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which includes a liquid crystal of which a molecular axis is uniformly aligned in parallel to a substrate of said liquid crystal; a Faraday rotator which rotates a polarized direction of said light beam by 45 degrees in a forward optical path leading from said radiation light source to said information medium and, further, rotates the polarized direction of said light beam by 45 degrees in a backward optical path leading from said information medium to said photodetector units; and said photodetector units sensing both of light quantities of ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a subtraction between signals representing said light quantities so as to obtain an information signal.

Claim 6

Dependent Claim 197 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives the linearly polarized light beam emitted from said radiation light source, and converges the linearly polarized light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which includes a liquid crystal of which a molecular axis is uniformly aligned in parallel to a substrate of said liquid crystal; a Faraday rotator which rotates a polarized direction of said light beam by 45 degrees in a forward optical path leading from said radiation light source to said information medium and, further, rotates the polarized direction of said light beam by 45 degrees in a backward optical path leading from said information medium to said photodetector units; and said photodetector units sensing both of light quantities of ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a subtraction between signals representing said light quantities so as to obtain an information signal.

Claim 7

Dependent Claim 215 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives said linearly polarized light beam emitted from said radiation light source, and converges the linearly polarized light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which includes a liquid crystal of which a molecular axis is uniformly aligned in parallel to a substrate of said liquid crystal; a transparent substrate constituting the liquid crystal hologram being made by a dielectric substrate serving as one component of a Faraday rotator which rotates a polarized direction of said light beam by 45 degrees in a forward optical path leading from said radiation light source to said information medium and, further, rotates the polarized direction of said light beam by 45 degrees in a backward optical path leading from said information medium to said photodetector units; and said photodetectors sensing both of light quantities of ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a subtraction between signals representing said light quantities so as to obtain an information signal.

Claim 8

Dependent Claim 215 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives said linearly polarized light beam emitted from said radiation light source, and converges the linearly polarized light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which includes a liquid crystal of which a molecular axis is uniformly aligned in parallel to a substrate of said liquid crystal; a transparent substrate constituting the liquid crystal hologram being made by a dielectric substrate serving as one component of a Faraday rotator which rotates a polarized direction of said light beam by 45 degrees in a forward optical path leading from said radiation light source to said information medium and, further, rotates the polarized direction of said light beam by 45 degrees in a backward optical path leading from said information medium to said photodetector units; and said photodetectors sensing both of light quantities of ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a subtraction between signals representing said light quantities so as to obtain an information signal.

Claim 9

Dependent Claim 268 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives said linearly polarized light beam emitted from said radiation light source, and converges the linearly polarized light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which is constituted by a pair of transparent substrates, a liquid crystal sandwiched between these transparent substrates, and a pair of transparent electrodes disposed between the liquid crystal and the transparent substrates, either of said transparent electrodes being formed with a hologram pattern; a Faraday rotator which rotates a polarized direction of said light beam by 45 degrees in a forward optical path leading from said radiation light source to said information medium and, further, rotates the polarized direction of said light beam by 45 degrees in a backward optical path leading from said information medium to said photodetector units; said liquid crystal hologram being applied a voltage in a reading-out operation of information signal higher than a voltage in a writing-in operation of the information signal, so that said light beam reflected from the information medium is diffracted in the liquid crystal hologram to generate ±1-order diffraction light beams; and said photodetectors sensing both of light quantities of said ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a subtraction between signals representing said light quantities so as to obtain the information signal.

Claim 10

Dependent Claim 268 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives said linearly polarized light beam emitted from said radiation light source, and converges the linearly polarized light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted at the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which is constituted by a pair of transparent substrates, a liquid crystal sandwiched between these transparent substrates, and a pair of transparent electrodes disposed between the liquid crystal and the transparent substrates, either of said transparent electrodes being formed with a hologram pattern; a Faraday rotator which rotates a polarized direction of said light beam by 45 degrees in a forward optical path leading from said radiation light source to said information medium and, further, rotates the polarized direction of said light beam by 45 degrees in a backward optical path leading from said information medium to said photodetector units; said liquid crystal hologram being applied a voltage in a reading-out operation of information signal higher than a voltage in a writing-in operation of the information signal, so that said light beam reflected from the information medium is diffracted in the liquid crystal hologram to generate ±1-order diffraction light beams; and said photodetectors sensing both of light quantities of said ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a subtraction between signals representing said light quantities so as to obtain the information signal.

Claim 11

Dependent Claim 199 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives a light beam emitted from said radiation light source, and converges the light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted from the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which includes a liquid crystal of which a molecular axis is uniformly aligned in parallel to a substrate of said liquid crystal; a quarter wavelength plate which converts said linearly polarized light beam into a circular polarized light beam in a forward optical path leading from said radiation light source to said information medium and, to the contrary, restores thus converted circular polarized light beam into a linearly polarized light beam in a backward optical path leading from said information medium to the photodetector units; and said photodetector units sensing both of light quantities of ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a summation of signals representing said light quantities so as to obtain an information signal.

Claim 12

Dependent Claim 199 words

An optical pickup head apparatus comprising: a radiation light source emitting a linearly polarized light beam; an imaging optics which receives a light beam emitted from said radiation light source, and converges the light beam to a small spot on an information medium; photodetector units including a plurality of photodetectors which receive the light beam being reflected and diffracted from the information medium and output electric signals in accordance with received light quantities; a liquid crystal hologram which includes a liquid crystal of which a molecular axis is uniformly aligned in parallel to a substrate of said liquid crystal; a quarter wavelength plate which converts said linearly polarized light beam into a circular polarized light beam in a forward optical path leading from said radiation light source to said information medium and, to the contrary, restores thus converted circular polarized light beam into a linearly polarized light beam in a backward optical path leading from said information medium to the photodetector units; and said photodetector units sensing both of light quantities of ±1-order diffraction light beams emitted from the liquid crystal hologram and calculating a summation of signals representing said light quantities so as to obtain an information signal.

Claim 13

Dependent Claim 30 words

An optical pickup head in accordance with claim 6 in which an alternating-current component of a calculated result obtained from said photodetector units is used for obtaining the information signal.

Claim 14

Dependent Claim 49 words

An optical pickup head apparatus in accordance with claim 6 in which said +1-order diffraction light beam emitted from the liquid crystal hologram converges in front of, a corresponding photodetector unit, and its conjugate -1-order diffraction light beam is a spherical wave having a focal point behind the photodetector.

Claim 15

Dependent Claim 56 words

An optical pickup head apparatus in accordance with claim 6 in which a hologram surface is dissected into several regions, and a tracking error signal is obtained by receiving diffraction light beams emitted from two of said regions by the photodetector unit and calculating a difference signal corresponding to a difference between two diffraction light beams.

Claim 16

Dependent Claim 26 words

An optical pickup head apparatus in accordance with claim 6 further comprising a collimator lens disposed between the liquid crystal hologram and the radiation light source.

Claim 17

Dependent Claim 31 words

An optical pickup head apparatus in accordance with claim 6 in which the imaging optics and the liquid crystal hologram are assembled in a holder so as to be shifted together.

Claim 18

Dependent Claim 29 words

An optical pickup head apparatus in accordance with claim 6 in which the radiation light source and the photodetector units are mounted close with each other as a unit.

Claim 19

Dependent Claim 44 words

An optical pickup head apparatus in accordance with claim 6 in which optical components including the radiation light source, the imaging optics, the photodetector units, the liquid crystal hologram and the quarter wavelength plate are assembled as a unit by an optical system holder.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2000-01-14	2000-07-15	2001-01-14	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2004-01-14	2004-07-15	2005-01-14	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2008-01-14	2008-07-15	2009-01-14	$7700.00	Window Closed / Lapsed

Optical pickup head apparatus

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