A nonintrusive instrument for measuring the volume flowrate of, and the speed of sound in, an arbitrary fluid in a pipe, tube or duct. The sound speed measured is that of a stationary fluid even though the measurement is made while the fluid may be flowing. These measurements are absolute in that they require no flow calibration, and they are independent of the composition of the fluid and its temperature. For a flowing, approximately perfect gas or gas mixture, given the average molecular weigh...

A wavelength calibration solution comprising from about 0.025 to about 0.140 molar neodymium and from about 0.135 to about 0.550 molar samarium, wherein the neodymium is present as a neodymium ionized constituent and the samarium is present as a samarium ionized constituent. A method for checking the wavelength accuracy of spectrometers or spectrophotometers of the type comprising measuring the absorbance (A) or percent transmittance (% T) of a wavelength calibration check solution versus a blan...

An optical coupler for a fiber optic communication system, which couples one band of wavelengths out of the fiber while allowing others to be carried further. This allows wavelength division multiplexing of different signals within a single fiber. The preferred embodiment of the invention is comprised of a waveguide having aperiodic corrugations in one wall and a Fabry-Perot type resonator enclosing the waveguide around the corrugations with its axis transverse thereto.

There is disclosed a multiple wavelength infrared spectrometer. It includes an optical chopper and a pendulum-like filter carrier which inserts a plurality of filters sequentially into the radiation beam. Filter changes occur during an opaque period of the chopper and each filter remains in place for a predetermined number of radiation pulses. The radiation passes through the sample and onto a detector which produces an electrical signal. An electronic circuit operates upon the signal so produce...

A device for calibrating a spectrophotometer or like device is disclosed. Spectrophotometers generally have an adjustable monochromator adapted to transmit a substantially monochromatic light beam through a sample cell. A detector measures the amount of light transmitted through the sample cell at different wavelengths to determine the composition of the sample. The present device comprises a probe adapted to be interposed in the light beam intermediate the monochromator and the detector in plac...

A system for measuring the complex degree of coherence of beams of optical radiation is disclosed. The system generally consists of a polarizer for preparing initially the state of the radiation field entering the device, a retarder oriented so as to divide the polarized beam into two orthogonally polarized components with a specific relative temporal retardation, and an electro-optic modulator which modulates the relative temporal phase shift as a function of time. The resultant beam is divided...

An improved multi-wavelength display system in which a multi-wavelength b source or sources are employed in combination with a multitude of waveguides in groups, one group for each wavelength, with image data responsive modulators to directly modulate said multi-wavelength beams and with a common rotary waveguide scanning means to produce a multi-wavelength facsimile display which could be color television, infrared or microwave displays according to the selected source or sources.

In dual wavelength equipment such as a combined read/write unit for an optical disc system, read light of wavelength .lambda..sub.1 is directed through an isolator and a combiner, is reflected from a target back through the combiner and, at the isolator is directed out of the incident beam path to photodetectors. Write light of wavelength .lambda..sub.2 is directed from a position off the read beam path to the combiner where it is re-directed into the read beam path and onto the target. The isol...

A wavelength selective laser in which an active dye cell is pumped, a dispersion apparatus inside the laser resonator is used to disperse differing emitted wavelengths along distinct feedback paths in the resonator, and an absorption dye cell inside the resonator is used to selectively transmit the wavelengths to be resonated through low-loss apertures provided therein in response to incident bleaching beams of radiation moving across the resonator cross section. By electronically scanning the b...

An avalanche photodetector useful at wavelengths as long as 1.7 microns with low noise is achieved. The crystal used includes successive layers of p-type indium phosphide, n-type indium phosphide, and n-type indium gallium arsenide. An appropriate total of fixed charges in the n-type indium phosphide and a graded bandgap heterointerface region are important for the improved results.