Abstract: A diode-pumped solid-state laser oscillator optically pumps a laser medium. The oscillator has at least one pumping light source that emits light in a predetermined wavelength band, and a laser medium that absorbs light in the wavelength band. In the wavelength band, the optical absorption index of the laser medium increases with an increase in wavelength, and the optical radiation energy of the light source decreases with an increase in wavelength. Thus, with respect to wavelength changes, an increase in the optical absorption index is cancelled out by a decrease in the radiation energy, making the stability of the laser output less dependent on the temperature of the optical pumping medium or laser medium.

Abstract: A method for decoding a digital signal includes receiving a multiple-bit digital signal that includes information to be transmitted; arraying bit strings of the received multiple-bit digital signal to thereby generate a received signal image as a two-dimensional image; arraying all types of predetermined proper signals used for signals transmitted and bit strings of patterns including errors each derived from each proper signal to thereby generate a different two-dimensional image and disposing a set of received signal patterns, each comprised of an arbitrary proper signal and a group of two-dimensional images of patterns having the arbitrary proper signal added with an error, in a state that enables identification of each proper signal to thereby generate a received signal pattern image; using optical signal processing to evaluate a coefficient of correlation between the received signal image and the received signal pattern image to thereby obtain a correlation projection image in which depth and brightness

Abstract: A phase modulation method and apparatus use a plurality of phase modulators disposed in series to phase-modulate light from a source laser. Modulation by the phase modulators is used to produce phase shifts in the optical signal, with modulation by the first phase modulator producing phase shifts of 0 degrees or 2&phgr; degrees, and modulation by the n-th phase modulator producing phase shifts of 0 degrees or 2n×&phgr; degrees. Here, &phgr; degrees is a predetermined phase level and n is an integer than two and not more than the number of phase modulators. The method is also used to detect and control transmission errors.

Abstract: A method and apparatus are provided that make it possible to speedily measure, and obtain images of, the three-dimensional distribution of electric fields in integrated circuits, using electro-optic sampling. The sampling is performed using a plurality of electric field sensors, each comprising an electro-optic crystal layer, a light-reflecting layer that is in close contact with the electro-optic crystal layer, and a separation layer that is in close contact with the reflection layer, separating the reflection layer from the object to be measured.

Abstract: A low-noise optical frequency converter uses a predetermined microwave electric signal to modulate an input light wave and output a light wave that includes a first-order upper-sideband or lower-sideband and a third-order lower-sideband or upper-sideband. The frequency converter modulates a light wave identical to the input light wave with a signal having a frequency that is three times that of the microwave signal, to form a first light wave having a first-order lower-sideband or upper-sideband. The first light wave is mixed with a second light wave having a first-order upper-sideband or lower-sideband and a third-order lower-sideband or upper-sideband, with a phase of the third-order lower-sideband or upper-sideband reversed to a phase of the first light wave, thereby suppressing third-order sidebands.

Abstract: A variable-optical-delay apparatus with a single wavelength converter and optical loop path has an optical modulator able to adjust the delay time according to the input optical signal. The variable-optical-delay apparatus has an optical input section and an optical output section, an optical filter and a wavelength shifter able to adjust an amount by which a wavelength of an input optical signal is shifted disposed on an optical path extending from the input section to the output section. The input optical signal is output from the output section after passing the wavelength shifter a number of times that is determined according to the input optical signal. A resonant type optical modulator can be used that is set between filters, or set between a filter and a reflector. Part of an optical path from the input section to the output section is in the form of an optical loop, an optical modulator is provided on the optical loop.

Abstract: A diode-pumped solid-state laser oscillator optically pumps a laser medium. The oscillator has at least one pumping light source that emits light in a predetermined wavelength band, and a laser medium that absorbs light in the wavelength band. In the wavelength band, the optical absorption index of the laser medium increases with an increase in wavelength, and the optical radiation energy of the light source decreases with an increase in wavelength. Thus, with respect to wavelength changes, an increase in the optical absorption index is cancelled out by a decrease in the radiation energy, making the stability of the laser output less dependent on the temperature of the optical pumping medium or laser medium.

Abstract: A laser oscillator comprises a laser medium, an optical excitation laser diode that irradiates the laser medium with light, a polarizer disposed on an optical path of the laser medium at a first end thereof, a first Porro prism disposed with the optical path coinciding with a point on a ridgeline thereof and with the ridgeline parallel or perpendicular to a plane of incidence of the polarizer, and a second Porro prism disposed on the optical path of the laser medium at a second end thereof with the optical path coinciding with a point on a ridgeline thereof. An angle formed by the two ridgelines of the first and second Porro prisms is a predetermined angle other than 0 degrees, 90 degrees, 60 degrees, 45 degrees and 36 degrees, 30 degrees.

Abstract: An optical modulation apparatus includes an optical signal input section, an optical signal propagation path, an optical modulator that modulates the phase of optical signals in at least two of a plurality of optical paths, and a wavelength selective filter that selectively reflects and transmits. Optical signals input via the input section are divided into a plurality of optical paths at a branching point and phase modulated by the phase modulator, that divides the optical path into a plurality of optical paths. Light transmitted by the filter is output via the output section, while light reflected by the filter travels back along the optical path and is again phase modulated by the phase modulator combined at the branching point and output from the input section as an intensity modulated optical signal.

Abstract: A transmission method with compensation for fading distortion or frequency offset distortion in digital communications using pilot signals, comprises the steps of: receiving modulated radiofrequency signals, demodulating the digital signals carried by said radiofrequency signals, extracting pilot signals from the received radiofrequency signals or demodulated digital signals, finding a spectrum of the extracted pilot signals, finding fading components or frequency-offset components from said spectrum, and using one of these components to compensate the received radiofrequency signal or estimate the original digital signal from the demodulated digital signals.

Abstract: A method of solving magnetoencephalographic and electroencephalographic inverse problems provides better grouping of moments of equivalent current dipoles than conventional methods. Locations of dipoles are fixed based on information using fMRI or the like. The magnitudes and orientations of the dipole moments are adjusted to fit magnetic fields produced by the dipoles to encephalographically measured data. The method also includes grouping the dipoles in two stages, using the correlation coefficient of the magnitudes of the dipole moments as a criterion.

Abstract: An ionosonde includes a signal-transmitting section for transmitting to an ionosphere pulsed radio waves whose frequency is scanned; a signal-receiving section that includes a loop antenna system for measuring intensity of a magnetic field Hz of pulsed radio waves reflected by the ionosphere, a first dipole antenna system for measuring intensity of an electric field Ex orthogonal to the magnetic field Hz and a second dipole antenna system for measuring intensity of an electric field Ey orthogonal to the magnetic field Hz and electric field Ex; and a signal-processing section using values obtained at the signal-receiving section to obtain a cosine (nx, ny) of an arrival direction {right arrow over (n)} of the reflected radio waves in accordance with relationship nx=(HzNx*−ExHz*)Z/(ExEy*−EyEx*) and relationship ny=(HzEy*−EyHz*)Z/(ExEy*−EyEx*), wherein Z stands for intrinsic impedance.

Abstract: An apparatus for retrieving and presenting digital data, includes a network that includes data archives containing digital data, a terminal that can be connected to the network, a retrieval device that retrieves digital data, using a database of digital data retrieval information including information added to each group of digital data that can be provided over the network, and a communication quality determination device that determines a quality of communication between the terminal and a data archive containing digital data extracted by the retrieval device based on search conditions specified by a user via the terminal. Digital data sorted into an order in accordance with a priority specified by the user is downloaded to a user terminal.

Abstract: A method for controlling a hyper-redundant manipulator including a plurality of links coupled by joints by determining the shape the manipulator takes when the end of the manipulator is moved to a target position, includes modeling each link as an elastic body having a natural length and a suitable modulus of elasticity that enables the elastic body to stretch and contract, simulating the overall shape of the manipulator when the end has been moved to the target position with the joints locked at a freezed angle and the joints are unlocked to return each link to its natural length, and moving the manipulator end to the target position by controlling each joint angle to match the simulation outcome.

Abstract: An optical frequency converter that can use a low-amplitude, high-frequency signal for converting a wide range of optical frequencies. The optical frequency converter includes a device for modulating a lightwave of a preset frequency with a modulation signal to generate a group of sidebands thereof, a device for selecting sidebands from among the group of sidebands, and a device for changing modulation signal frequencies and selecting specific sidebands.

Abstract: A local-area communication system includes a private branch exchange that controls links between outside lines and the local area; wireless base-stations distributed within the local system area, each connected to the exchange; a portable card terminal capable of long-range wireless communication with the wireless base-stations, the portable card terminal having stored therein a unique ID number and being capable of short-range wireless communication in the local area; auxiliary telephone terminals located within the local area capable of short-range wireless communication with the portable card terminal and which can send and receive speech signals, and a portable card terminal box that is connected to the exchange. The card box can recharge the card terminal and transmit the ID information to the exchange.

Abstract: A method for acquiring azimuth information is provided in which first and second planar patch antennas (11a, 11b) are disposed so that their sky coverage areas partially overlap to form a common area (2), thereby dividing the antenna sky coverage area into a first area (1), third area (3) and common second area 2, and an azimuth is limited utilizing azimuths acquired in the respective areas and the angle between the two antennas. As a result, azimuth limitation information can be effectively acquired even at a location where the sky is severely blocked and satellite information can be adequately acquired only at a small range of sky visibility.

Abstract: A method for acquiring azimuth information enables acquisition of azimuth information by receiving signals transmitted by GPS satellites using only a single antenna.

Abstract: A GPS receiver includes an antenna unit, a GPS receiver unit, a result output unit, a data transmitting unit, a data receiving unit, a data processing unit for carrying out calculation on data containing a strength value of each received GPS satellite signal to limit or determine an azimuth of a measurement direction, and a use mode control switch.

Abstract: A resonance type optical modulator includes an optical path having electro-optical effect characteristics, a modulation electrode formed along the optical path for applying an electric field to the optical path, a common electrode formed in opposition to the modulation electrode, a feeding line that is connected to the modulation electrode and stubs connected to the feeding line, wherein the feeding line, stubs and common electrode are provided on one side of a region that is divided by the modulation electrode.