Victor Company of Japan, Limited

Ntt Data Communications Systems Corporation

Universidad Politécnica De Madrid

Systems, LLC

Nit Data Communications Victor Company of Japan

Ntt Data Comm. Sys.

Kazutoshi Hirohashi

Yukinobu Ishigaki

Takaaki Takeda

Takeshi Nomoto

Keishi Ushijima

Yasuomi Namiki

Manabu Sakane

Yoshiaki Yunoki

Masahisa Sakai

Michio Kikuta

Akio Yoshikawa

Hiroshi Horii

Atsushi Sakamoto

Yoshiki Iwasaki

Shunichi Shichijo

Hisashige Fujiwara

Motoyasu Nagashima

Hideo Koike

Masamichi Satou

Francisco-José López-Hernández

Teruhiko Shinomiya

Kazuo Ichihara

Yoshitaka Sakurai

Juan-Carlos Minano-Dominguez

Susumu Katayama

Pablo Benitez-Giménez

Tetsuo Fukasawa

A rotary jointcapable of stably transmitting superfine images and high-speed data is provided. The rotary jointincludes a stationary partand a rotary partrotatable about an axis against the stationary partand transmits light signals between the stationary partand the rotary partThe rotary partincludes at least one light transmissive cylindrical memberarranged coaxially with the axis, a light emitting elementand a light receiving elementboth arranged on one end of the memberWhile, the stationary partincludes a light receiving elementopposed to the light emitting elementin the rotary partand a light emitting elementopposed to the light receiving elementin the rotary part

Rotary joint

The present invention provides a light source device that is safe for human eyes and whose switching is performed at high speed. The light source device comprises one or more laser light sources () for emitting a monochromatic or polychromatic light beam, a diffuser (), which may be transmissive, reflective, or a mixture thereof, for diffusing the light beam received directly from the laser light source or via an optical focusing system (), and an optical collimator (), which collimates the diffused light bundle emitted from the diffuser ().

Light source device

Interference between adjacent sections is prevented in an optical wireless communication system, in which a center device is capable of concurrently communicating through lines with a plurality of parent devices each disposed in one of the sections into which a communication area of the system is divided and each of the parent devices communicates with a plurality of child devices disposed in the same section where said parent device is disposed. The sections is grouped into some groups of sections which do not adjoin each other. Optical wireless communications are done only within one group of sections in each communication period. Some techniques for improving the effect of communication are disclosed.

Optical wireless communication system

A bi-directional optical wireless communication apparatus comprises a modulator outputting a narrow band signal whose center frequency is selected from N center frequencies, an optical transmitter transmitting an optical signal from the narrow band signal, an optical receiver for receiving N optical signals, N receiving circuits corresponding to the N center frequencies, a cancelling circuit for cancelling the optical signal received by the optical receiver via reflective object in received N optical signals using the narrow band signal in accordance with a magnitude of the optical signal received by the optical receiver, a frequency discriminator discriminating frequencies of the received N optical signals, and a control circuit. The frequency discriminator discriminates for an interval that the optical transmitter does not transmit the optical signal. Then, the modulating circuit continuously outputs a received signal from one of N receiving circuits corresponding to the discriminated frequency and the modulator modulates the narrow band signal to have a center frequency other than the discriminated frequency under control of the control circuit. The interval is repeated with a repetition randomly set interval.

Bi-directional optical wireless communication apparatus and method of

An optical wireless transmission system providing short-distance communication, such as for linking a personal computer to a LAN, utilizes direct baseband modulation of optical signals, but provides simultaneous bidirectional transmission of data between a pair of optical transmitting/receiving units while also enabling a data clock signal to be easily regenerated from a received optical signal. Effects of signal noise due to artificial illumination are eliminated by a suitable choice of transmission bandwidth, and bandpass filtering of a received data signal.

Optical wireless data transmission system and optical wireless data

An optical radio communication system comprising a first light transmitting system and a second light transmitting system. Each of said first and second light transmitting system comprising a transmitting means and a receiving means. Said transmitting means comprising a light emitting element positioned in a region including and surrounding a focal point of a first parabolic reflector for emitting light beams, said first parabolic reflector having an inner reflective surface for reflecting said light beams emitted from said light emitting element, and a means for driving said light emitting element with a signal to be transmitted. Said receiving means comprising a second parabolic reflector having an inner reflective surface for reflecting incident light beams, a light receiving element positioned in a region including and surrounding a focal point of said second parabolic reflector for receiving light beams reflected by said second parabolic reflector to output signals, and means for taking out information from said signals outputted from said light receiving element. In this optical radio communication system, broadband signals such as Manchester coded signals are directly transmitted on optical radio.

Optical radio transmission system and a method for adjusting optical

An optical radio system includes a host device, an end device, and a repeater. The host device and the end device communicate with each other via the repeater by use of optical radio. The repeater includes a section for receiving a first light signal from one of the host device and the end device, a section for converting the received first light signal into a first electric signal, a section for frequency-converting the first electric signal into a second electric signal, and a section for generating a second light signal in response to the second electric signal and transmitting the generated second light signal. The repeater also includes a section for demodulating one of the first electric signal and the second electric signal into a baseband signal, a section for detecting a quality of the baseband signal, and a section for enabling transmission of the second light signal only when the detected quality of the baseband signal is equal to or greater than a predetermined quality.

Optical radio repeater with signal quality detection

A repeater for packet data optical communication between terminal devices includes a first section and a second section. The first section includes a first device for receiving a first optical signal transmitted from a terminal device and for converting the first optical signal into a first electric signal, a second device for frequency-converting the first electric signal to a second electric signal, and a third device for converting the second electric signal into a second optical signal and for transmitting the second optical signal. The second section includes a fourth device for receiving a third optical signal and for converting the third optical signal into a third electric signal, a fifth device for frequency-converting the third electric signal to a fourth electric signal, and a sixth device for converting the fourth electric signal into a fourth optical signal and for transmitting the fourth optical signal to a terminal device.

Repeater system

A rotary head type magnetic recording and reproducing apparatus comprises a circuit for recording and reproducing a signal on and from a magnetic recording medium by rotary heads, a circuit for obtaining a frequency modulated (FM) audio signal by frequency-modulating a carrier by an audio signal which is to be recorded, a circuit for generating a frequency drift detection signal having a constant frequency which does not exist within a frequency range occupied by the FM audio signal, a circuit for obtaining a frequency multiplexed signal by frequency-multiplexing the FM audio signal and the detection signal, a circuit for separating the FM audio signal and the detection signal from the signal reproduced by the rotary heads, a demodulating circuit for obtaining an audio signal by frequency-demodulating the separated FM audio signal, a detecting circuit for frequency-demodulating the separated detection signal and for detecting a frequency drift component, a circuit for forming a frequency drift correction signal responsive to the output of the detecting circuit, and a circuit for correcting a frequency drift component in the output audio signal of the demodulating circuit by the correction signal.

Audio magnetic recording and/or reproducing apparatus utilizing

In a quarternary differential PSK demodulator, a QPSK input signal is applied to first and second synchronous detectors to which carriers with a 90-degree phase difference therebetween are respectively applied from a voltage-controlled oscillator. A first double-balanced phase detector multiplies the outputs from the synchronous detectors. A second phase detector squares the output of the second synchronous detector. A third double-balanced phase detector provides multiplication of the outputs of the first and second double-balanced phase detectors to generate an output having four times the frequency of the outputs of the synchronous detectors to cancel the information carried by the input PSK signal. A loop filter converts the output of the third phase detector to a DC phase control signal to be applied to the voltage-controlled oscillator.

Quarternary differential PSK demodulator

In a noise reduction circuit, a sampling pulse is generated for opening a switch in time-coincident relationship with a signal portion which is affected by a noise impulse. During tracking modes the signal is passed through the switch to a junction between a capacitor and a noninverting amplifier to charge the capacitor to the level of the signal. During a sampling mode the switch is open to block the signal. A feedback circuit having plural time constant values is connected between the output and input of the amplifier to provide primary and secondary differentiation of the output signal of the amplifier. The feedback circuit is disabled during tracking modes to enable the amplifier to linearly amplify the voltage developed across the capacitor and is enabled during the sampling mode to differentiate the voltage that occurred immediately before the switch is turned off for application to the input of the amplifier for linearly interpolating the noise-affected portion of the signal.

Noise reduction by linear interpolation using a dual function amplifier

In a noise reduction circuit for reception of stereophonic FM signals in which the demodulated signal is chopped at twice the pilot frequency for separation between left- and right-channel signals, the demodulated signal is sampled by a first sample-and-hold circuit in response to the output of the noise detector to store that portion of the signal which appeared immediately prior to the occurrence of an impulse noise. The demodulated signal is also sampled by a second sample-and-hold circuit at a frequency twice the pilot frequency to eliminate a noise which might arise due to the chopping of the demodulated signal. A signal is derived from the outputs of the first and second sample-and-hold circuits that indicates the slope ratio of the demodulated signal at the moment that occurred immediately prior to the impulse noise. The slope ratio signal is applied to a linear integrator to generate a compensating voltage which is summed with the signal sampled by the first sample-and-hold circuit at the level which occurred immediately prior to the occurrence of the impulse noise.

Noise reduction for stereophonic FM signals by high-speed sampling and

In a noise reduction circuit, a sampling pulse is generated for operating a switch in time-coincident relationship with the portion of a signal which is affected by a noise impulse. The signal, applied to an input terminal, is normally passed through the switch to a junction between a capacitor and a noninverting amplifier and is blocked when the switch opens in response to the sampling pulse. A differentiator is connected in a feedback circuit from the output of the noninverting amplifier to the input thereof. The differentiator is disabled when the switch remains closed and when the switch opens in response to the sampling pulse it begins differentiating a voltage which occurred immediately prior to the detection of the noise and supplies it to the capacitor to linearly interpolate the portion of the information signal which is disrupted by the noise impulse.

An analog audio signal having a high frequency preemphasis is applied to a sampling pulse generator (2) which generates a sampling pulse in response to an impulse noise introduced to the signal and also to a sample-hold and deemphasis circuit (5; 50) which deemphasizes the audio signal when impulse noise is nonexistent and holds the signal in the presence of the sampling pulse. A differentiator (6) derives a signal representative of the slope ratio of the analog signal from the deemphasized signal. A sample-and-hold circuit (7) samples the slope ratio signal in response to the sampling pulse and applies it to a charging and discharging circuit (8; 503) which performs linear charging and discharging of the capacitor (55; 505) at a rate variable as a function of the sampled signal to reconstruct the portion of the signal lost during the sampling period.

Impulse noise reduction by linear interpolation having a deemphasis

An analog audio signal is applied to a sampling pulse generator (2) which generates a sampling pulse in response to an impulse noise introduced to the signal and also to a first sample-and-hold circuit (5, 6, 7) which tracks the waveform of the audio signal when impulse noise is nonexistent and holds the signal in the capacitor (6) in response to the sampling pulse. A nonlinear transfer circuit (10) is provided to eliminate white noise contained in the analog signal from the first sample-and-hold circuit and feeds its output to a differentiator (11) to derive a signal representative of the slope ratio of the analog signal. A second sample-and-hold circuit (12) samples the slope ratio signal in response to the sampling pulse and applies the sampled signal to a bidirectional constant current source (8) which provides constant current charging and discharging of the capacitor (6) to linearly vary the voltage sampled by the first sample-and-hold circuit (12).

Growing community of inventors

Yokohama, Japan

Kazutoshi Hirohashi