Abstract: A variable optical filter comprises a first polarizer, a first phase difference element operable to generate a phase difference, a variable Faraday rotator operable to impart a variable Faraday rotation, a second phase difference element operable to generate a phase difference, and a second polarizer, wherein said polarizers, said variable Faraday rotator, and said phase difference elements are arranged in the mentioned order along the optical axis, and wherein when the angles formed by the optic axes of said first and second phase difference elements and the transmitted polarization azimuth of the first polarizer are assumed respectively to be ?1 and ?2, these ?1 and ?2 are set to different angles.

Abstract: A small-sized magnetic field generator which is suitable for mass production and provides better output stability. A plurality of coils are formed on a non-magnetic insulating material by depositing at least one layer of conductive film in a spiral pattern. A hollow is made in the center of each coil, so that a plurality of main magnetic cores are arranged on the insulating substrate, with their ends fit into those hollows. By supplying appropriate electrical signals to drive the coils individually, their combined magnetic field can be controlled to have an arbitrary distribution. This combined magnetic field is applied to a magneto-optical target device held on the insulating material.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: An optical filter including first and second polarizers, a Faraday rotator and a birefringent element operating together to filter light with a changeable optical transmittance versus wavelength characteristic curve. The curve has specific characteristics.

Abstract: The present invention has an object to provide a manufacturing method of readily realizing an optical filter having a flat transmission characteristic and a superior cutoff characteristic relative to adjacent bands. To this end, with the manufacturing method of the present invention, a band-pass filter consisting of a dielectric multilayer coating is formed on one plane of a transparent substrate, and an antireflection coating is formed on the other plane of the substrate. The substrate is then divided into a plurality of segments, and adjacent two segments are selected and adhered to each other by a transparent adhesive with band-pass filter surfaces of these segments facing to each other, while interposing a glass spacer between the band-pass filter surfaces, to thereby obtain an optical filter.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: A small-sized magnetic field generator which is suitable for mass production and provides better output stability. A plurality of coils are formed on a non-magnetic insulating material by depositing at least one layer of conductive film in a spiral pattern. A hollow is made in the center of each coil, so that a plurality of main magnetic cores are arranged on the insulating substrate, with their ends fit into those hollows. By supplying appropriate electrical signals to drive the coils individually, their combined magnetic field can be controlled to have an arbitrary distribution. This combined magnetic field is applied to a magneto-optical target device held on the insulating material.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: The present invention relates to a tunable optical filter having a variable wavelength characteristic of transmittance. The tunable optical filter includes first and second polarizers each having a transmission axis determining a polarization axis of transmitted polarized light, a birefringent element having an optic axis determining a phase difference given between two orthogonal components of transmitted polarized light, and a Faraday rotator for giving a variable Faraday rotation angle to transmitted polarized light. The birefringent element and the Faraday rotator are provided between the first and second polarizers.

Abstract: The present invention relates to an optical attenuator comprising first and second attenuator units cascaded on an optical path, and a control circuit connected to the first and second attenuator units. Each of the first and second attenuator units includes a Faraday rotator provided on the optical path. The Faraday rotator generates a Faraday rotation angle given as a function of wavelength. Each of the first and second attenuator units further includes polarizing unit for generating an attenuation determined by the Faraday rotation angle on the optical path. The control circuit, for example, controls the Faraday rotation angle in each of the first and second attenuator units so that a wavelength characteristic of attenuation in the first attenuator unit is substantially canceled by a wavelength characteristic of attenuation in the second attenuator unit.

Abstract: An optical filter having a changeable optical transmittance versus wavelength characteristic curve to variably filter a light. The curve maintains a fixed optical transmittance at a specific wavelength as the curve is changed. The optical filter includes a Faraday rotator having a variable Faraday rotation angle, to change the optical transmittance versus wavelength characteristic curve.

Abstract: The present invention relates to an optical attenuator comprising first and second attenuator units cascaded on an optical path, and a control circuit connected to the first and second attenuator units. Each of the first and second attenuator units includes a Faraday rotator provided on the optical path. The Faraday rotator generates a Faraday rotation angle given as a function of wavelength. Each of the first and second attenuator units further includes polarizing unit for generating an attenuation determined by the Faraday rotation angle on the optical path. The control circuit, for example, controls the Faraday rotation angle in each of the first and second attenuator units so that a wavelength characteristic of attenuation in the first attenuator unit is substantially canceled by a wavelength characteristic of attenuation in the second attenuator unit.

Abstract: An object of the invention is to provide a small size Faraday rotator which is easy to produce and enables reliable reduction of temperature dependence of the Faraday rotation angle, by defining the crystal orientation and arrangement order of each Faraday element when three or more Faraday elements are used. For this purpose, a Faraday rotator of the present invention comprises: a Faraday element section being composed of a plurality of Faraday elements, a permanent magnet for applying a magnetic field to each Faraday element in a parallel direction to an optical axis direction, and an electromagnet for applying a variable magnetic field in a perpendicular direction to the optical axis direction, wherein each Faraday element is arranged such that the crystal orientation of each is perpendicular to a light beam direction, and crystal orientations of adjacent Faraday elements are opposed to each other.

Abstract: The present invention aims at providing a variable optical attenuator to achieve the reduction of the wavelength-dependency of the entire device, by optimizing the magneto-optical system of the variable optical attenuator by deliberating the wavelength-dependency of Faraday rotation angles. To this end, the variable optical attenuator according to the present invention comprises: a Faraday rotator for providing a variable Faraday rotation angle; and a polarizer and an analyzer arranged in front of and behind the Faraday rotator, respectively, wherein the angle formed between the optical axis of the analyzer and the optical axis of the polarizer is set such that the Faraday rotation angle at which the wavelength-dependency of the optical attenuation amount of the variable optical attenuator becomes the maximum, is brought to be substantially 0°, to thereby reduce the wavelength-dependency of the optical attenuation amount at the aforementioned Faraday rotation angle.

Abstract: The present invention has an object to provide a manufacturing method of readily realizing an optical filter having a flat transmission characteristic and a superior cutoff characteristic relative to adjacent bands. To this end, with the manufacturing method of the present invention, a band-pass filter consisting of a dielectric multilayer coating is formed on one plane of a transparent substrate, and an antireflection coating is formed on the other plane of the substrate. The substrate is then divided into a plurality of segments, and adjacent two segments are selected and adhered to each other by a transparent adhesive with band-pass filter surfaces of these segments facing to each other, while interposing a glass spacer between the band-pass filter surfaces, to thereby obtain an optical filter.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: The present invention relates to a tunable optical filter having a variable wavelength characteristic of transmittance. The tunable optical filter includes first and second polarizers each having a transmission axis determining a polarization axis of transmitted polarized light, a birefringent element having an optic axis determining a phase difference given between two orthogonal components of transmitted polarized light, and a Faraday rotator for giving a variable Faraday rotation angle to transmitted polarized light. The birefringent element and the Faraday rotator are provided between the first and second polarizers.

Abstract: The present invention has an object to provide a manufacturing method of readily realizing an optical filter having a flat transmission characteristic and a superior cutoff characteristic relative to adjacent bands. To this end, with the manufacturing method of the present invention, a bandpass filter consisting of a dielectric multilayer coating is formed on one plane of a transparent substrate, and an antireflection coating is formed on the other plane of the substrate. The substrate is then divided into a plurality of segments, and adjacent two segments are selected and adhered to each other by a transparent adhesive with band-pass filter surfaces of these segments facing to each other, while interposing a glass spacer between the band-pass filter surfaces, to thereby obtain an optical filter.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: An &agr;-glucosidase inhibitor is described. It is comprised of an extract of Touchi selected from the group consisting of an extract of Touchi extracted with alcohol, an extract of Touchi extracted with a mixture of water and alcohol in a water to alcohol ratio of 1:5 to 5:1, and an extract of Touchi extracted with water at 100° C. to 140° C. The components in the extract which have a molecular weight of at least 3000 as determined by means of gel filtration or membrane filtration are at most 20% by weight and wherein the extract inhibits &agr;-glucosidase at least 90.4%.