27 March 1997 Dynamic mask: new approach to laser engraving of halftone images
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Abstract
New approach to laser engraving of half tone images has been proposed and tested. Combining two basic approaches to laser engraving -- single pulse mask imaging and raster element construction by pack of laser pulses -- the new system constructs every individual raster element by imaging on the workpiece surface a dynamic mask of controlled size. The dynamic mask shape corresponds to the required raster element shape. This approach offers several important advantages over the conventional ones: (1) analog control of the mask shape provides gray level continuum, thus ensuring the image quality, unattainable by other means; (2) raster element marking by single laser pulse provides very good marking rate. It takes only one scan of the writing laser head to mark raster line. Much more powerful laser pulses can be used to engrave complete raster element by single pulse instead of its point-by-point construction by consecutive laser pulses; (3) the influence of laser beam quality parameters, such as beam divergence, and power instabilities on the gray level has been greatly reduced because raster element shape primarily depends on the mask shape and not on the power level and beam divergence. Dynamic mask system can be used both with cw and pulsed laser. Gray scale tones can be reproduced by the linear raster line width in the first case. Advantages of the new device have been demonstrated by engravings on stone, wood, etc. made with 50 W carbon-dioxide laser.
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Victor N. Kadan, Victor N. Kadan, Alexander S. Pekarik, Alexander S. Pekarik, Rafael V. Estrela Liopis, Rafael V. Estrela Liopis, } "Dynamic mask: new approach to laser engraving of halftone images", Proc. SPIE 2993, Lasers as Tools for Manufacturing II, (27 March 1997); doi: 10.1117/12.270019; https://doi.org/10.1117/12.270019
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