Diffractive optic with the aperture and a variable focal length and the laser cutting device with this optical system

摘要

The invention concerns an optical device for focusing a light beam, comprising: a Fourier diffractive element (2, 14), for separating an incident beam (6) into n beams (10-1, 10-2, 10-3, 10-4, 10-5, 18, 20), along n directions symmetrical relative to an optical axis (AA', BB'); a diffractive element (4, 22) comprising n components (4-1, 4-2, ..., 4-8) for re-focusing the n beams on the optical axis, each of said n components comprising a continuous series of Fresnel lenses with different focal lengths. Such an optical device can be integrated into a laser cutting device.