Abstract: An optical information recording method includes the following steps. A converting step is converting a light beam into an information beam carrying information by using a spatial beam modulator. A focusing step is focusing the information beam on an optical information recording medium including an information recording layer. An irradiating step is irradiating the optical information recording medium with a reference beam and the information beam so that the reference beam and the information beam intersect with each other on the information recording layer by using an optical component. A rotating step is rotating the optical information recording medium or the optical component by using a drive unit for performing angle-multiplex recording. A management information recording step is recording management information at two or more relative angles having an angle interval smaller than twice at least a first null angle.

Abstract: An optical information recording/reproducing apparatus includes a spatial light modulator that converts an irradiation beam emitted from a light source to a single information beam that carries information; an optical system that causes the single information beam to be collected on an optical-information recording medium including an information recording layer capable of recording the information as hologram by using interference fringes produced due to interference between the single information beam and a plurality of reference beams, and causes each of the reference beams to be irradiated to the optical-information recording medium from mutually different directions so as to intersect with the single information beam in the information recording layer; and a controller that controls to cause the light source to emit the irradiation beam and performs angular multiplexing recording of the information in the information recording layer while controlling to drive either one of the optical-information recordi

Abstract: An image pickup lens includes, in order from an object side to an image side, an aperture stop, a first lens element having a positive refractive power, a second lens element having a negative refractive power and a biconcave shape, a third lens element having a positive refractive power and a meniscus shape whose concave surface faces the object side, and a fourth lens element having a negative refractive power. In the image pickup lens, the following conditional expressions are satisfied, 0.20<f/|f2|<0.9 ?d1??d2>25 where f denotes the focal length of the entire lens system, f2 denotes the focal length of the second lens element, ?d1 denotes the Abbe number of the first lens element, and ?d2 denotes the Abbe number of the second lens element.

Abstract: According to one embodiment, an APC photodetector accepts a light beam branched from a light beam toward a recording medium by a branching mirror and detects intensity of a light beam supplied from a light source, a light quantity adjusting element adjusts the intensity of the light beam, and the intensity of the light beam incident to the APC photodetector is changed in a continuous manner or a stepwise manner by the light quantity adjusting element. Therefore, when the single APC photodetector detects recording and reproducing light beams, the recording and reproducing light beams can fall within a dynamic range of the APC photodetector.

Abstract: According to one embodiment, an optical head device provides a signal processing circuit which sets a control amount to move an objective lens so that a distance between the objective lens and a given recording layer of the an optical disc coincides with a focal position, an optical path length correction mechanism which corrects an influence of an aberration component producing an error in the focal distance, a thickness difference detection circuit which finds an amount of correction to be made by the optical path length, and an aberration correction circuit which generates a correction signal to correct the influence of the aberration component producing the error in the focal distance detected by the thickness difference detection circuit, and supplies the correction signal to the optical path length correction mechanism.

Abstract: According to an embodiment of the optical head unit includes two or more light sources, an objective lens which condenses the light beam having the predetermined wavelength output from each of the light sources to a recording layer of a recording medium, and captures a light beam reflected on the recording layer, a polarization control element arranged between the light sources and the objective lens, to optimize directions of polarization of the light beam having the predetermined wavelength output from the light source and the light beam reflected on the recording layer, in accordance with the wavelength thereof, on the basis of a voltage to be applied, a photodetector which receives the reflected light beam captured by the objective lens and outputs a predetermined signal, and a polarization controller which varies the direction of polarization set by the polarization control element, in accordance with the output of the photodetector, the fluctuations of the signals recorded and/or reproduced in each wave

Abstract: According to one embodiment, an optical head unit according to an embodiment of the invention, a reflected beam guided to a detection area of a photodetector is changed in the image forming characteristic by a liquid crystal element, which is placed between an object lens and a collimator lens, and provided with a controllable diffraction index, according to a spherical aberration amount corresponding to a thickness error in a protection layer of an optical disc and a comatic aberration amount corresponding to a disc tilt of an optical disc.

Abstract: According to one embodiment, an optical pick up apparatus according to an embodiment of the invention has an object lens which captures a light beam reflected on a recording surface of an optical disc, a polarization control element which divides a light beam captured by the object lens into a predetermined number of beams, and diffracts each divided beam in a predetermined direction, a photodetector which detects a light beam divided and diffracted by the polarization control element for each divided component, and a signal processor which calculates a tilt component along the radial direction of am optical disc, in an output of the photodetector, as a difference between a signal component indicating a change in the distance from the object lens to an optical disc, and a signal component indicating a position in the radial direction of a string of signal components recorded in an optical disc.

Abstract: According to one embodiment, an optical head unit of the invention combines preferably and simplifies a diffraction pattern of a diffraction element to guide a reflected laser beam divided into a predetermined number to a photodetector, in order to provide an optical head unit and an optical disc apparatus which provide a stable reproducing signal irrespectively of the standards of recording media, when reproducing information from a recording medium of optional standard. By using the combined and simplified diffraction pattern, the optical head unit easily provides outputs usable to detect first, second and third signals used to detect a tracking error when reproducing information recorded on an optical disc from a reflected laser beam from an optical disc, a fourth signal used to detect a focus error, and a fifth signal used to detect a spherical aberration compensating component.

Abstract: According to one embodiment, a diffraction pattern of a diffraction element, or a hologram polarization element, to guide a reflected laser beam divided into a predetermined number to a photodetector is combined preferably as one unit, in order to provide an optical head unit and an optical disc apparatus, which provides a stable reproducing signal, irrespectively of the standards of recording media, when reproducing information from a recording medium of optional standard. By using this diffraction pattern, it is possible to obtain outputs usable to detect first, second and third signals used to detect a tracking error when reproducing information recorded on an optical disc from a reflected laser beam from an optical disc, a fourth signal used to detect a focus error, and a fifth signal used to detect a disc tilt error and a spherical aberration compensating component.

Abstract: An optical head unit according to an embodiment of the invention includes a diffraction element which has a diffraction pattern capable of outputting a non-diffraction component, ±1st diffraction components, and an electric signal corresponding to the non-diffraction component, to the light-receiving surface of a photodetector which receives a reflected laser beam reflected on a recording layer of an optical disc and outputs a corresponding signal, as an signal at least for reproducing information recorded on the optical disc, and capable of outputting electric signals corresponding to the ±1st diffraction components for generating a focus error signal by a spot size method. The ratio of a component output as a non-diffraction component is increased to higher than the ratio of components output as ±1st diffraction components, and the signal to noise ratio of a reproduces signal is improved.

Abstract: According to one embodiment, an optical pickup according to the present invention has a servo circuit in which, when Tp is a track pitch of an optical disk, NA is the numerical aperture of an objective lens, and Fp is a detection range of a focus error, a focus detection range defined in a range of 2Tp/(NA×Fp)<0.6 is assigned. In this manner, it is possible to reduce the cases where focus control becomes unstable due to leakage of a track error signal into a focus error signal. Therefore, an optical disk recording and reproducing apparatus which is less likely to malfunction can be obtained by using this optical pickup.

Abstract: A fiber laser device contains a first optical fiber of a double-clad type in which optical resonance of an infrared laser light takes place inside a core with Pr3+and Yb3+added thereto to generate a light of a wavelength of about 630 nm, a second optical fiber of a double-clad type in which optical resonance of an infrared laser light takes place inside a core with Pr3+and Yb3+added thereto to generate a light of a wavelength of about 690 nm, and a third optical fiber in which optical resonance of the lights from the first and second optical fibers takes place inside a core with Tm3+added thereto to generate a light of a wavelength of about 450 nm, and the core diameter of the third optical fiber is made substantially equal to the spot diameters of the lights from the first and second optical fibers.

Abstract: A laser apparatus according to this invention includes an optical resonator, which has a mirror capable of enclosing light with a required output wavelength and light with a first non-required output wavelength able to increase the efficiency of generating the light with the required output wavelength, in an optical fiber, at both ends of an optical fiber added with ions capable of generating light with a required output wavelength, and damping or discharging light with a second non-required output wavelength to suppress generation of light with the required output wavelength, to outside.

Abstract: Light from a first excitation light source is incident on one facet of a first optical fiber. A core is doped with a first rare earth substance. A resonant section induces light resonance in the core to generate resonant light, thereby providing selected light at the other facet of the first optical fiber. An optical multi/demultiplexer reflects the light of the selected wavelength in a direction different from that of the first optical fiber. A second excitation light source supplies light to the resonant section of the first optical fiber via the optical multi/demultiplexer and the other facet of the first optical fiber. A second optical fiber guides the light of the selected wavelength from the optical multi/demultiplexer to an exterior.

Abstract: Among light emitted from a semiconductor laser, light emitted within a predetermined angle &thgr;x with respect to the z-axis in the direction of the slow axis (x-axis) is returned by a plane mirror to the semiconductor laser to enhance the intensity of the laser light emitted by the semiconductor device using external resonance.

Abstract: The present invention has the feature that, in a semiconductor laser apparatus having a negative electrode and a positive electrode sandwiching an active region (active region layer), and an optical resonance chamber which is defined by a high-reflecting mirror and an output mirror positioned at the both end portions thereof, the positive electrode and an oscillation optical axis which is the axis of the optical resonance chamber are made so as to be non-parallel.

Abstract: A fiber laser apparatus comprises a plurality of semiconductor lasers, and an optical fiber which beams emitted from the plurality of semiconductor lasers are caused to enter. The plurality of semiconductor lasers being so arranged that the emitted beams are almost parallel to one another in a slow-axis direction and the incidence angles of the emitted beams to the optical fiber differ from one another in a fast-axis direction.

Abstract: An up-conversion laser unit in which a semiconductor laser of high output power can be used as a pump light source and the wavelength of up-converted laser light is suitable for display. The light of infrared wavelength is generated by the pump light source, the generated light being inputted into a Pr3+ up-conversion laser to up-convert there into red light by Pr3+ ion. The up-converted red light is inputted into, as a pump light source, a Tm3+ up-conversion laser, there being up-converted into blue light by the Tm3+ ion. Thereby, efficient up-conversion into blue light is made possible.

Abstract: Light from a first excitation light source is incident on one facet of a first optical fiber. A core is doped with a first rare earth substance. A resonant section induces light resonance in the core to generate resonant light, thereby providing selected light at the other facet of the first optical fiber. An optical multi/demultiplexer reflects the light of the selected wavelength in a direction different from that of the first optical fiber. A second excitation light source supplies light to the resonant section of the first optical fiber via the optical multi/demultiplexer and the other facet of the first optical fiber. A second optical fiber guides the light of the selected wavelength from the optical multi/demultiplexer to an exterior.