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:
Nov. 12, 1991
Filed:
Apr. 26, 1990
Thomas F Johnston, Jr, Auburn, CA (US);
Gerald H Williams, Meadow Vista, CA (US);
Coherent, Inc., Palo Alto, CA (US);
Abstract
A method and apparatus for determining the quality of a multimode laser beam (10). In the preferred embodiment, the apparatus includes a lens (32) for creating a transformed or imaged waist from the input beam. The location of the transformed beam waist and its diameter are then determined. These steps can be carried out by chopping the beam using a rotating hub (14) having apertures (36,38) for selectively passing the beam. Preferably, one of the apertures has a pair of 45.degree. knife edges (40,42). The transmission of the beam past the knife edge is monitored by a detector (30). In operation, the lens focal position is varied while the transmission of the beam past the knife edge is monitored in order to locate and measure the diameter of the transformed waist. The diameter of the beam at one other known location is measured. A processor then calculates beam quality by fitting these measurements to a mathematical model. Once the quality of the beam is calculated, the location of the original beam waist and its diameter can be derived. Once all of the beam parameters are derived, the propagation characteristics of the beam can be predicted. In the preferred embodiment, the transformed beam waist is located by taking incremental measurements of beam diameter, at both the front and rear planes of the hub, as the lens is moved a distance at least a great as the diameter of the hub. The diameter measurements are spliced together by the processor to provide an axial profile of the beam over a distance twice as large as the diameter of hub. This data can then be analyzed to find the minimum which corresponds to the location of the transformed beam waist.