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:
Jul. 23, 1991
Filed:
Mar. 27, 1989
Brian H Kolner, Woodside, CA (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
An optical time-domain reflectometry (OTDR) system comprises an oscillator, a phase shifter, an amplifier, an optical pulse generator, an integrated electro-optical circuit, a detector, a timer, a converter, and an output device. The OTDR system can be used to determine which surface of a photographic lens is impairing transmissivity the most. When the amplifier is enabled, a signal from the oscillator starts the timer and triggers the pulse generator. The timer is a time-to-digital circuit with analog interpolation. The resulting pulse is transmitted through the integrated electro-optical circuit and into the lens being evaluated. The strongest reflection from the lens is detected and the resulting detection signal stops the timer. The timed duration is expressed by the converter as a distance which can be used to identify the lens surface of interest. The result is displayed and/or stored on the output device. An electrical waveform from the oscillator is conveyed along a transmission line defined by electrodes of the integrated electro-optical circuit. This waveform introduces phase distortion in the optical pulse conveyed along an optical path of the integrated electro-optical circuit. The phase shifter is programmed so that these phase distortions are approximately quadratic over the pulse duration, so that the frequency of the pulse is 'swept' linearly. The integrated electro-optical circuit includes a dispersive grating which introduces time delay as a function of frequency. The combination of sweeping and dispersing results in a pulse which is compressed relative to its original form. The compressed pulse allows more precise identification of the surface causing the strongest reflection so that modern multi-element lenses can be effectively evaluated.