1. A device for processing material by focused electromagnetic radiation, comprising: - an electromagnetic radiation source, - optical components directing and focusing the radiation onto or into the material, - means for generating a pattern in the electromagnetic radiation beam, - at least partially reflective surface mounted on the beam path in front of the focus of focused radiation with the possibility of projecting onto it at least partially the specified pattern by at least parts of these optical components, at least one detector configured to receive a reflected, through the indicated surface, image of the pattern and generate electrical signals corresponding to the specified image, which contains information about the focus position, a computer configured to receive these electrical signals and programmed to process the specified image to generate an electrical signal depending on the focal position, and the control element divergence divergence installed on the beam path and configured to receive the indicated electrical signal generated by the computer and change the divergence of electromagnetic radiation in accordance with the specified signal. 2. The device according to claim 1, wherein said surface is installed at the place of exit of electromagnetic radiation from the device. The device according to claim 1, wherein the material to be processed is eye tissue, preferably a cornea. The device according to claim 1, in which the specified source is a laz1. Устройство для обработки материала посредством сфокусированного электромагнитного излучения, содержащее:- источник электромагнитного излучения,- оптические компоненты, направляющие и фокусирующие излучение на или в материал,- средство для генерирования паттерна в пучке электромагнитного излучения,- по меньшей мере частично отражающую поверхность, установленную на траектории пучка перед фокусом сфокусированного излучения с возможностью проецирования на нее, по меньшей мере, частично указанного паттерна
