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Title: Method and apparatus for precision laser micromachining

A method and apparatus for micromachining and microdrilling which results in a machined part of superior surface quality is provided. The system uses a near diffraction limited, high repetition rate, short pulse length, visible wavelength laser. The laser is combined with a high speed precision tilting mirror and suitable beam shaping optics, thus allowing a large amount of energy to be accurately positioned and scanned on the workpiece. As a result of this system, complicated, high resolution machining patterns can be achieved. A cover plate may be temporarily attached to the workpiece. Then as the workpiece material is vaporized during the machining process, the vapors condense on the cover plate rather than the surface of the workpiece. In order to eliminate cutting rate variations as the cutting direction is varied, a randomly polarized laser beam is utilized. A rotating half-wave plate is used to achieve the random polarization. In order to correctly locate the focus at the desired location within the workpiece, the position of the focus is first determined by monitoring the speckle size while varying the distance between the workpiece and the focussing optics. When the speckle size reaches a maximum, the focus is located at the firstmore » surface of the workpiece. After the location of the focus has been determined, it is repositioned to the desired location within the workpiece, thus optimizing the quality of the machined area.« less
Inventors:
 [1];  [2];  [3]
  1. (San Ramon, CA)
  2. (Pleasanton, CA)
  3. (Danville, CA)
Issue Date:
OSTI Identifier:
872980
Assignee:
United States Enrichment Corporation (Bethesda, MD) LLNL
Patent Number(s):
US 6057525
Application Number:
08/926657
Contract Number:
W-7405-ENG-48
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Country of Publication:
United States
Language:
English
Subject:
method; apparatus; precision; laser; micromachining; microdrilling; results; machined; superior; surface; quality; provided; near; diffraction; limited; repetition; rate; pulse; length; visible; wavelength; combined; speed; tilting; mirror; suitable; beam; shaping; optics; allowing; amount; energy; accurately; positioned; scanned; workpiece; result; complicated; resolution; machining; patterns; achieved; cover; plate; temporarily; attached; material; vaporized; process; vapors; condense; eliminate; cutting; variations; direction; varied; randomly; polarized; utilized; rotating; half-wave; achieve; random; polarization; correctly; locate; focus; desired; location; position; determined; monitoring; speckle; size; varying; distance; focussing; reaches; maximum; located; repositioned; optimizing; wavelength laser; desired location; pulse length; repetition rate; laser beam; cover plate; diffraction limited; polarized laser; machining process; surface quality; accurately positioned; near diffraction; visible wavelength; accurately position; wave plate; speed precision; precision laser; /219/