STUDY OF THE INFLUENCE OF DEFOCUSED LASER MARKING PROCESS BY MELTING ON SAMPLES OF STEEL
The studies relate to the process of laser marking by melting on the samples of structural steel. The zone of Raleigh for fiber laser was determined. The theoretical dependences of the diameter of the working spot from defocusing and diameter of the radiation falling on the lens were received. Experiments were realized with 50G structural steel. The dependence of contrast of marking from defocusing for two power densities was determined. Working intervals were determined for studied magnitudes for visual perception of the marking.
 Н. Гоголева, Application of Lasers in Science, Technique and Medicine [In Russian: Применение лазеров в науке, технике, медицине], ETU Leti, St. Petersburg 2007, 4–5.
 Н. Ангелов, Optimization of the Process of Marking with Laser Radiation of the Samples of Tool Steel [In Bulgarian: Оптимизация на процеса маркиране с лазерно лъчение на образци от инструментална стомана], doctorac thesis, Technical Univeristy Gabrovo, 2011, 09, 13–14. http://www.tugab.bg/images/stories/2011/petrov/avtoreferat_01b.pdf
 Л. Лазов, Н. Ангелов, Key Factors De-termining the Quality of Marking the Metals and Alloys [In Bulgarian: Основни фактори, определящи качеството на маркировката на метали и сплави], International Conference AM-TEH’07, Gabrovo 2007, Vol. I, 102–107.
 30W/40W G3.1 Pulsed Fiber Laser, SPI Lasers, Ltd. 2010, Document No: SM-S00177_B 100907, ,p. 66