I-Tek, Inc.

John P Lindley

James Rieden

L Curtis Foster

Charles B Crumly

A system for detecting the presence of coherent radiation comprises an interference filter having a pair of partially-reflective mirrors. The spacing between the mirrors is varied in accordance with a sine function to change the transmission wavelength of the mirrors. A reference signal is developed which represents this periodic variation in the spacing of the mirrors. A photodetector on the output side of the filter detects radiation transmitted therethrough, yielding a detection signal in the presence of coherent radiation transmitted through the filter. An indicator responds to the signal output of the photodetector and to the reference signal to produce an identifying indication of the detected radiation.

Radiation discrimination system

An electro-optic system having an extended dynamic power range. The dynamic power range of a Bragg cell spectrum analyzer is expanded by unevenly splitting the radiation output of the Bragg cell with a beam splitter and directing a major portion of the radiation output to a first photodiode array and a minor portion of the radiation output to a second photodiode array. The first photodiode array is utilized to detect the output of the Bragg cell until it becomes sufficiently intense to saturate it. When the first photodiode array becomes saturated, the second photodiode array, which receives a minor amount of radiation from the Bragg cell, is utilized to detect the output of the Bragg cell. Detection with the first and second photodiode arrays allows the dynamic power detection range of the system to be expanded to include the combined detection ranges of the first and second photodiode arrays.

Electro-optic system with expanded power range

A sweeping spectrum analyzer for analyzing the frequency and amplitude of an input signal is comprised of a Bragg cell with a laser beam input and an accoustic signal input. An input signal is mixed with a sweep signal to produce a heterodyned signal within the acoustic bandwidth of the Bragg cell. The heterodyned signal is applied to the Bragg cell and results in deflection of a laser beam passing therethrough. The Bragg cell output is imaged onto a charge coupled photodetector array and fed to a shift register as clock pulses. The clock pulses are synchronized with the sweep signal frequency for transfer as one charge packet down a charge coupled array.

Sweeping spectrum analyzer

A Bragg cell spectrum analyzer in which the output of the Bragg cell is detected by a unique electro-optic system which allows the selection of any desired dynamic power detection range. As is known in the art, the output of a Bragg cell consists of a radiation spot or spots along a line in which the position of each spot along the line is related to the frequency of a component of the input signal to the Bragg cell, and the intensity of radiation of each spot is proportional to the strength of the component causing that spot. In the disclosed embodiment the output of the Bragg cell is directed upon a cylindrical lens system which expands each spot into a line of radiation. This results in a two dimensional pattern of lines with the position of each line being the same as the position of the radiation spot causing the line, and the intensity of radiation in each line being proportional to the intensity of radiation in the spot causing that line. The two dimensional pattern of radiation, consisting of spaced lines of radiation, is directed through a stepped density filter onto a two dimensional photodiode array. The photodiode array is utilized to detect the position of each line, which indicates the frequency of the input component causing that line, and is utilized to detect the number of photodiodes reaching saturation along the line, which indicates the strength of the component.

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Redwood City, CA, United States of America

John P Lindley