Hamamatsu-Photonics K.k.

Hamamatsu Photonics Kabushiki Kaisha

Akira Takeshima

Musubu Koishi

Yutaka Tsuchiya

Yoshihiko Mizushima

Hironori Takahashi

Yoshihisa Warashina

Akira Takahashi

Mitsunori Nishizawa

Koji Ichie

Kazuhiko Wakamori

Kouichi Shirakawa

Ichizo Ogawa

Morio Takeichi

Shinichirou Aoshima

In this system, reflected light from an electro-optic probe is detected by a photodetector, and only a voltage signal of a frequency which is an integral multiple of the fundamental frequency of the output voltage from the photodetector is detected. The frequency characteristics of the output voltage from the photodetector can be measured at a high speed and a high accuracy.

Voltage measuring using electro-optic material's change in refractive

An apparatus of this invention emits light onto an EO probe and detects the light reflected by the EO probe by using an MSM photodetector. The MSM photodetector is applied with a voltage of a frequency nf.sub.0 +.DELTA.f.

Voltage measurement system

An optical feedback photodetection apparatus of the present invention achieves high-speed response while minimizing noise to obtain a high S/N ratio and a wide dynamic range. In the apparatus, on the basis of a modulated drive signal from a drive signal output circuit, a semiconductor laser outputs a light beam modulated at a frequency f.sub.0 to irradiate an object to be measured through an optical system, and the light beam reflected by the object is fed back to the semiconductor laser through the optical system. The intensity of the light beam from the semiconductor laser having an optical amplification function varies due to the return light beam. A photoconductive light-receiving device to which a modulated voltage signal at the frequency f.sub.0 from a voltage application unit is applied receives the light beam from the semiconductor laser and having an intensity varying due to the return light beam, thereby performing synchronous detection. A modulated current signal flowing through the photoconductive light-receiving device is converted to a voltage signal by a current/voltage conversion unit, and the low-frequency component of the voltage signal is extracted.

Optical feedback photodetection apparatus

A photoconductive photodetector to which a modulation voltage signal having a predetermined frequency is applied receives a signal to be measured (I.sub.I) while adjusting the phase of a modulation signal by a phase shifter. A current-to-voltage conversion unit extracts a DC component of a current signal generated at the photoconductive photodetector in correspondence with the intensity of a predetermined frequency component of the signal to be measured (I.sub.I) as a voltage signal. The maximum value of DC voltage values (V.sub.O) obtained in every setting operation of a phase adjustment value is identified. The maximum value corresponds a case in which the modulation voltage signal and the predetermined frequency component of the signal to be measured (I.sub.I) are in phase. The intensity of the predetermined frequency component of the signal to be measured (I.sub.I) is calculated. As a result, a high-speed phenomenon can be measured with a high precision.

Synchronous signal detection apparatus with a photoconductive

An excitation light beam intensity-modulated and output from a light-sending unit is irradiated on a target measurement object. A scattered light beam or a reaction light beam is detected by a light-receiving unit through a wavelength selector. The light-receiving unit outputs a signal according to the product of a supplied modulation signal and the received light beam. A processing unit acquires data corresponding to the product value for each type of light, and calculates the decay characteristics of the reaction light beam on the basis of the acquisition result. In this manner, with a simple arrangement, the decay time of a fluorescence sample or the like is precisely measured in a wide frequency range.

Decay characteristic measuring apparatus

An optical frequency mixing apparatus is provided. Mixing of a frequency of an incident light intensity and a frequency (f.sub.3) of an AC signal generated by a signal generator, i.e., product calculation of the two signals is executed by a photoconductive photodetector of a photodetecting unit. This apparatus has a large allowance for unnecessary incident light such as background light and output characteristics having satisfactory linearity with respect to the incident light intensity, and can deeply set gain modulation. One of the frequency components of the sum and difference between the two signals, which is obtained as a result of product calculation, is selected and extracted using a frequency selector. As an incident optical signal, one optical signal whose light intensity has an AC component (frequency=f.sub.1) may be used. Alternatively, two optical signals whose light intensities have different frequencies (frequencies=f.sub.1 and f.sub.2) may be incident on substantially the same photodetecting area of the photoconductive photodetector.

Optical frequency mixing apparatus

Laser light from LD (laser diode) is guided through a fiber to be projected onto a reflector. A receiver detects a return beam of modulated light reflected by the object and outputs a signal reflecting a phase difference between the laser light and the modulation signal. The frequency of the modulation signal is changed based on the signal value so as to finally achieve phase lock. When the phase lock fixes the frequency of the modulation signal, the frequency always corresponds to a distance from LD to the reflector or a group index of a substance filling the optical path. Thus, the distance to the object or the group index of the substance filling the optical path at the time of phase lock can be determined in a simple manner and with a high accuracy, based on the output frequency at the time of phase lock.

Optical measuring apparatus

In phase difference detecting method, circuit, and apparatus of the present invention, a voltage signal having a predetermined frequency is applied to a photoconductive light-receiving device, and an optical signal is received by this photoconductive light-receiving device. A current generated upon reception of light and flowing in the photoconductive light-receiving device reflects a product value of the voltage signal and the optical signal, and contains a DC component according to a phase difference between the voltage signal and the component of the optical signal having the same intensity modulation frequency as that of the voltage signal. A time average value of the current flowing in the photoconductive light-receiving device or a voltage value obtained upon conversion of this current is generated, and only the DC component is extracted, thereby detecting the phase difference between the voltage signal and the component of the optical signal having the same intensity modulation frequency as that of the voltage signal.

Phase difference detecting method, circuit and apparatus

Times t.sub.1 and t.sub.2 required for two electromagnetic waves having different wavelengths to propagate from a reference point to a target point are measured. Necessary meteorological conditions along the path are also measured to determine refractivities N.sub.1 and N.sub.2 of the path for the two electromagnetic waves as:

Method and apparatus for distance measurement using electromagnetic waves

A deflecting voltage generating circuit comprising a voltage generating unit for generating a deflecting voltage and a voltage correcting unit for correcting the deflecting voltage generated by the voltage generating unit and applying the deflecting voltage thus corrected to deflecting electrodes of a streak tube, a sampling streak tube or the like. The voltage correcting unit is so designed that for a predetermined period from the time instant when the deflecting voltage changes, the deflecting voltage is not applied to the deflecting electrodes, and immediately after the lapse of the predetermined period the deflecting voltage is applied to the deflecting electrodes.

Deflecting voltage generating circuit

In a device for measuring the time interval between first and second optical pulses, the time interval between the first optical pulse and a first one of the train of reference optical clock pulses which is closest to the first optical pulse, and the time interval between the second optical pulse and a second one of the train of reference optical clock pulses which is closest to the second optical pulse are measured, and the time interval between the first and second optical pulses is calculated according to the time intervals thus measured and the time interval between the first and second reference optical clock pulses.

Time interval measuring device

A laser pulse train jitter measuring device includes a first optical path having a length set at a first value or a second value and a second optical path having a length variable between a first value and a second value. A laser beam is split into a first beam directed to the first optical path and a second beam directed to the second optical path. The split beams are recombined into a correlated beam and recorded as visible images so that jitter in the laser beam can be detected from the differences in the recordings when the first optical path has its first length while the second optical path is varied between the first value and the second value from when the first optical path has its second length while the second optical path is varied between the first value and the second value.

Laser pulse train jitter measuring device

An electron tube device for measuring light pulses generated at a high repetition rate which includes an electron tube, power supply device and deflection voltage generator. The electron tube has a photocathode, focusing electrode, deflection electrodes, slit electrode, dynodes and a collector electrode positioned within an evacuated envelope. The power supply device supplies voltages to the dynodes and to the focusing and slit electrodes, and the deflection voltage generator supplies deflection voltages to the deflection electrodes which successively change in phase with respect to light pulses impinging on the photocathode so that different portions of the light pulses can be successively sampled.

Instruments for measuring light pulses clocked at high repetition rate

An instrument for measuring light pulses generated at a high repetition rate comprising a streaking tube and optical means for directing the light pulses to a photocathode layer forming part of the streaking tube. A signal synchronized with the light pulses is combined with a control signal in a delay circuit having an output coupled to deflection electrodes in the streaking tube, electrons emitted from the photocathode being deflected by the voltage applied to the deflection electrodes and impinging on a phosphor layer to form a streaking image. A sampling means is positioned adjacent the phospher layer for picking up a portion of the streaking image and coupling it to a photoelectric multiplier tube. The outputs of the photomultiplier tube and the control signal are connected to an output device for displaying the photomultiplier output as a function of the control signal.

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Hamamatsu, Japan

Akira Takeshima