The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 01, 1994
Filed:
Apr. 21, 1992
David Fink, Los Angeles, CA (US);
Hughes Aircraft Company, Los Angeles, CA (US);
Abstract
Frequency modulated radar transmitters with a repetitive linear increase in frequency with time, referred to as 'frequency chirps', are required for many radar applications. The present invention provides a simple way of obtaining such a chirped frequency modulation for a laser radar transmitter or the like. The principle is to translate an optical wedge in the direction of its wedge gradient at constant velocity across the optical path of a laser resonator. The resulting increase or decrease in the effective optical length of the resonator causes frequency chips. In a first embodiment of the present invention, a rotating phase plate on the face of a rotating wheel with the added phase varying linearly with angular position around the wheel is placed within a laser's resonator cavity to tune the optical pathlength of the cavity and thereby the longitudinal mode of the resonator to produce the chirp. This embodiment can be used in either a reflective or a transmissive mode. In a second embodiment of the present invention, the outer peripheral rim of a spiral wheel having a spirally increasing or decreasing radius is used, whereby the rim functions as a mirror, is disposed within the laser resonator. Rotating the wheel changes the optical pathlength of the resonator and causes the longitudinal modes of the resonator to tune so as to generate the required chirp sequence. Lastly, various systems are proposed for eliminating various types of errors in the system as well as for generating both up-chirps and down-chirps sequentially and/or simultaneously.