Abstract: A watermark embedder embeds a cryptographic key as a digital watermark into input host data and thereby generates key-embedded host data, and then provides it to a hash generator and a signature attacher. A hash generator generates a hash by putting the key-embedded host data into a one-way function, and provides the hash to an encryptor. The encryptor encrypts hash generated by the hash generator with the cryptographic key and thereby generates a digital signature. The signature attacher attaches the digital signature generated by the encryptor to the key-embedded host data generated by the watermark embedder, and outputs the signature-attached key-embedded host data.

Abstract: A grinding wheel having a tool portion formed by firmly fixing diamond grains to an end face of a cup-shaped core by brazing. A circumferentially continuous groove is formed in a substantially central portion of the end face of the core. The abrasive grains are firmly fixed to an end face portion excluding regions near an outer rim and near an inner rim of the end face and near the boundaries with the groove under the condition that, with respect to all the abrasive grains, skirts of a brazing material layer for holding the abrasive grains have a length one or more times an average grain size of the abrasive grains. The provision of the groove in the end face of the core can enhance the capability of ejecting chips that occur during machining; besides, chips can be captured in the groove to preclude the occurrence of scratches resulting from the chips.

Abstract: A six-segment holographic surface is divided into regions by dividing lines. A four-segment photodetection part is divided into four photodetection parts equal in area by a section line substantially parallel to the radial direction of an optical disk and a section line orthogonal thereto. A main light beam diffracted in the regions of the six-segment holographic surface are condensed as spots at positions apart from each other on opposite sides on a section line of the four photodetection parts, and the main beam diffracted in the regions is condensed as spots in the center of the photodetection parts of the four-segment photodetection part.

Abstract: A grinding wheel having a tool portion formed by firmly fixing diamond grains to an end face of a cup-shaped core by brazing. A circumferentially continuous groove is formed in a substantially central portion of the end face of the core. The abrasive grains are firmly fixed to an end face portion excluding regions near an outer rim and near an inner rim of the end face and near the boundaries with the groove under the condition that, with respect to all the abrasive grains, skirts of a brazing material layer for holding the abrasive grains have a length one or more times an average grain size of the abrasive grains. The provision of the groove in the end face of the core can enhance the capability of ejecting chips that occur during machining; besides, chips can be captured into the groove to preclude the occurrence of scratches resulting from the chips.

Abstract: In a captured image outputting system, an image shot by an image capturing device is, upon shooting the image thereby, instantaneously transmitted to a display control device of a display system via wireless communication. The display system instantaneously projects the received image on a projection screen. The display system is comprised of a display device and a display control device. A liquid crystal projector may serve as the display device whereas an optional device, for use in wireless communication, connected to image input terminals of the liquid crystal projector may serve as the display control device. A digital still camera may serve as the image capturing device capable of carrying out wireless communication.

Abstract: Digital cameras which improve operability in checking, storing, and editing shot images have not been satisfactory. A digital camera and a user terminal including a file server are connected over a network. When the digital camera is powered on, it automatically establishes a network connection with the file server in an activation process. When the digital camera shoots an image, this image is transmitted to the file server automatically upon completion of the encoding and compression of the image. When image reproduction is instructed from the digital camera, the image is downloaded from the file sever over the network and displayed on the digital camera.

Abstract: A grating surface of a diffraction grating diffracts a laser beam emitted from a semiconductor laser device in ±1st order directions. The grating surface is formed in a rectangular or elliptic shape in such dimensions that a light spot formed on an objective lens by ±1st order diffracted beams is located in an aperture of the objective lens and not displaced from the aperture even if the objective lens is horizontally moved in a tracking operation. A grating surface of another diffraction grating has a width smaller than the width of an overlap region of a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the ±1st direction, entering an objective lens and a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the −1st direction, entering the objective lens.

Abstract: A grating surface of a diffraction grating diffracts a laser beam emitted from a semiconductor laser device in ±1st order directions. The grating surface is formed in a rectangular or elliptic shape in such dimensions that a light spot formed on an objective lens by ±1st order diffracted beams is located in an aperture of the objective lens and not displaced from the aperture even if the objective lens is horizontally moved in a tracking operation. A grating surface of another diffraction grating has a width smaller than the width of an overlap region of a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the +1st direction, entering an objective lens and a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the −1st direction, entering the objective lens.

Abstract: A grating surface of a diffraction grating diffracts a laser beam emitted from a semiconductor laser device in ±1st order directions. The grating surface is formed in a rectangular or elliptic shape in such dimensions that a light spot formed on an objective lens by ±1st order diffracted beams is located in an aperture of the objective lens and not displaced from the aperture even if the objective lens is horizontally moved in a tracking operation. A grating surface of another diffraction grating has a width smaller than the width of an overlap region of a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the +1st direction, entering an objective lens and a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the −1st direction, entering the objective lens.

Abstract: A six-segment holographic surface is divided into regions by dividing lines. A four-segment photodetection part is divided into four photodetection parts equal in area by a section line substantially parallel to the radial direction of an optical disk and a section line orthogonal thereto. A main light beam diffracted in the regions of the six-segment holographic surface are condensed as spots at positions apart from each other on opposite sides on a section line of the four photodetection parts, and the main beam diffracted in the regions is condensed as spots in the center of the photodetection parts of the four-segment photodetection part.

Abstract: A grating surface of a diffraction grating diffracts a laser beam emitted from a semiconductor laser device in ±1st order directions. The grating surface is formed in a rectangular or elliptic shape in such dimensions that a light spot formed on an objective lens by ±1st order diffracted beams is located in an aperture of the objective lens and not displaced from the aperture even if the objective lens is horizontally moved in a tracking operation. A grating surface of another diffraction grating has a width smaller than the width of an overlap region of a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the +1st direction, entering an objective lens and a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the −1st direction, entering the objective lens.

Abstract: First and second photodiodes are arranged on the upper surface of a stem, returned light beams diffracted in the + 1st order by a transmission type holographic optical element are received by the first photodiode, while returned light beams diffracted in the − 1st order are received by the second photodiode. The first photodiode has a plurality of light receiving regions, and respectively outputs a reproducing signal, a focus error signal and a tracking error signal on the basis of the returned light beams. On the other hand, the second photodiode has a single light receiving region, and outputs a reproducing signal on the basis of the returned light beams.

Abstract: A grating surface of a diffraction grating diffracts a laser beam emitted from a semiconductor laser device in ±1st order directions. The grating surface is formed in a rectangular or elliptic shape in such dimensions that a light spot formed on an objective lens by ±1st order diffracted beams is located in an aperture of the objective lens and not displaced from the aperture even if the objective lens is horizontally moved in a tracking operation. A grating surface of another diffraction grating has a width smaller than the width of an overlap region of a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the +1st direction, entering an objective lens and a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the −1st direction, entering the objective lens.

Abstract: A transmission-type holographic optical element has a four-segment holographic surface divided into four regions of equal areas by virtual dividing lines which are perpendicular to each other. The first dividing line is at an angle with respect to the track direction of an optical disk and the second dividing line is at an angle with respect to the radial direction of the optical disk before tracking phase adjustment. The first dividing line coincides with the track direction of the optical disk and the second dividing line coincides with the radial direction of the optical disk after tracking phase adjustment. A four-segment photodetection part is divided into four photodetection parts of equal areas by a dividing line substantially parallel to the radial direction of the optical disk and a dividing line perpendicular thereto.

Abstract: A semiconductor laser device is mounted on the side of one end surface on lead frame in a recess of an insulating molding member, a three-beam generating diffraction grating is disposed in the center, and a transmission type holographic optical element is disposed on the side of the other end surface. After a flexible circuit board is fixed to the lower surfaces of leads and the lead frame, a photodiode for a signal detection is mounted on the surface of the flexible circuit board, and is so folded upward as to be perpendicular to the upper surface of the lead frame. The insulating molding member is mounted on the one end surface of the insulating molding member through a circular screw through a hole and an elliptic screw through a hole by screws.

Abstract: An optical pickup device has a case constructed by joining a lower frame member and an upper frame member. A semiconductor laser device, a three-beam generating diffraction grating, a transmission type holographic optical element, and a reflecting mirror are arranged in the lower frame member. A lead frame is arranged in the lower frame member. The semiconductor laser device is arranged on the lead frame through a heat sink, to emit laser light in a horizontal direction. A photodiode and the lead frame are arranged in the upper frame member. The photodiode has a light receiving surface parallel to the direction of light emission from the semiconductor laser device, and is mounted on the lead frame. The laser light emitted from the semiconductor laser device passes through the three-beam generating diffraction grating and the transmission type holographic optical element, and is then bent upward and introduced into an optical recording medium.

Abstract: An optical pickup apparatus includes a semiconductor laser generating a light having a short wavelength for reproduction of a high-density information recording medium and a semiconductor laser outputting a light for reproduction of an information recording medium with low recording density. A three-beam generating diffraction grating, a transmission type holographic optical element and a condenser lens are disposed in the light path in which the laser lights from the semiconductor lasers propagate toward the recording surface of an information recording medium. The laser light emitted from each semiconductor laser is transmitted through the three-beam generating diffraction grating and divided into three beams and then transmitted through the transmission type holographic optical element and passed through the condenser lens to reach the recording surface of the information recording medium.

Abstract: A semiconductor laser device comprises: a semiconductor laser including laser resonators for emitting laser beams forward and backward oppositely along a plurality of parallel axes; a photodetector including a plurality of photodetector elements for detecting intensities of the laser beams emitted backward; and a waveguide located between the semiconductor laser and the photodetector for guiding the backward emitted laser beams to the corresponding ones of the photodetector elements, the waveguide including a plurality of guide grooves for guiding the backward emitted laser beams.