System for reading information from two storage layers of an optical disk in different manners
AssigneeBrother Kogyo Kabushiki Kaisha
InventorsYutaka Hattori, Yukimasa Yoshida
Life of this patent
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Abstract
An information-reproducing system for reading information from a plurality of storage layers of an optical disk. The system includes a light source for irradiating the optical disk with a radiation, a first information-reproducing device for reading information from one of the plurality of storage layers, based on a change in an amount of the radiation reflected by the one storage layer, and a second information-reproducing device for reading information from another of the storage layers, based on a change in an angle of Kerr rotation of the radiation reflected by the above-indicated another storage layer.
Claims12
An information-reproducing system for reading information from two storage layers of an optical disk, the two storage layers being spaced from each other in a direction of thickness of the optical disk, wherein the information is based on a change in the Kerr rotation angle reflected by one of said two storage layers and on a change in an intensity of radiation reflected by the other of said two storage layers comprising:
- a single laser source for irradiating corresponding local areas of said two storage layers of said optical disk with a linearly polarized laser beam having a predetermined wavelength, such that said laser beam is partially reflected by a top one of said two storage layers and partially passes through the top one of said two storage layers, to irradiate the remaining storage layer;
- a half mirror disposed in a light path defined between said laser source and said optical disk, for reflecting the laser beam reflected by said two storage layers of the optical disk;
- a beam splitter for splitting the laser beam reflected by said half mirror, into a first beam and a second beam which have polarization planes perpendicular to each other;
- a first optical sensor and a second optical sensor which are operable to receive said first and second beams and produce first and second output signals, respectively;
- a differential amplifier operable to receive said first and second output signals from said first and second optical sensors, and amplify a difference between said first and second output signals, thereby producing an output signal indicative of said change in the angle of Kerr rotation of the radiation reflected by said one of said two storage layers of the optical disk;
- and
- an adder operable to add said first and second output signals from said first and second optical sensors, and produce an output signal indicative of said change in the intensity of the radiation reflected by said other storage layer of the optical disk.
An information-reproducing system for reading information from two storage layers of an optical disk, the two storage layers being spaced from each other in a direction of thickness of the optical disk, wherein the information is based on a change in the Kerr rotation angle reflected by one of said two storage layers and on a change in an intensity of radiation reflected by the other of said two storage layers, comprising:
- a first laser source for producing a first linearly polarized laser beam;
- an object lens for converging said first linear polarized laser beam on the one of said two storage layers of the optical disk;
- a first half mirror disposed in a light path between said first laser source and said object lens, for reflecting said first laser beam reflected by said one storage layer;
- a second half mirror disposed in the light path between said first laser source and said object lens;
- a second laser source for emitting a second linearly polarized laser beam toward said second half mirror such that said second laser beam is reflected by said second half mirror, transmitted along said light path and converged on the other of said two storage layers of the optical disk through said object lens, such that a portion of said other storage layer corresponding to a portion of said one storage layer irradiated by said first laser beam is irradiated by said second laser beam, said second laser beam having a wavelength different from that of said first laser beam, and a polarization plane perpendicular to that of said first laser beam, said first hair mirror also reflecting said second laser beam reflected by said other storage layer;
- a beam splitter for splitting each of said first and second laser beams respectively reflected by said two storage layers, into two beams whose polarization planes are perpendicular to each other;
- a first optical sensor and a second optical sensor which are operable to receive said two beams and produce first and second output signals, respectively;
- a differential amplifier operable to receive said first and second output signals from said first and second optical sensors, and amplify a difference between said first and second output signals, thereby producing an output signal indicative of said change in the angle of Kerr rotation of the first laser beam reflected by said one storage layer;
- and
- an adder operable to add said first and second output signals from said first and second optical sensors, and produce an output signal indicative of said change in the intensity of the second laser beam reflected by said other storage layer.
An information-reproducing system for reading information from two storage layers of an optical disk, the two storage layers being spaced from each other in a direction of thickness of the optical disk, wherein the information is based on a change in the Kerr rotation angle reflected by one of said two storage layers and on a change in an intensity of radiation reflected by the other of said two storage layers, comprising:
- a first laser source for producing a first linearly polarized laser beam;
- an object lens for converging said first linearly polarized laser beam on the one of said two storage layers of the optical disk;
- a half mirror disposed in a light path between said first laser source and said object lens, for reflecting said first laser beam reflected by said one storage layer;
- a first dichroic mirror disposed in said light path, between said first laser source and said half mirror;
- a second laser source for emitting a second linearly polarized laser beam toward said first dichroic mirror such that said second laser beam is reflected by said first dichroic mirror, transmitted along said light path and converged on the other of said two storage layers of the optical disk through said object lens, such that a portion of said other storage layer corresponding to a portion of said one storage layer irradiated by said first laser beam is irradiated by said second laser beam, said second laser beam having a wavelength different from that of said first laser beam, and a polarization plane perpendicular to that of said first laser beam, said first half mirror also reflecting said second laser beam reflected by said other storage layer;
- a second dichroic mirror for splitting each of said first and second laser beams respectively reflected by said two storage layers, into two beams whose polarization planes are perpendicular to each other;
- a first optical sensor and a second optical sensor which are operable to receive said two beams and produce first and second output signals, respectively;
- a differential amplifier operable to receive said first and second output signals from said first and second optical sensors, and amplify a difference between said first and second output signals, thereby producing an output signal indicative of said change in the angle of Kerr rotation of the first laser beam reflected by said one storage layer;
- and
- an adder operable to add said first and second output signals from said first and second optical sensors, and produce an output signal indicative of said change in the intensity of the second laser beam reflected by said other storage layer.
Dependencies are inferred from the claim text.