Improvement of the optical system in direct laser engraving to increase the resolution of printing plates

Abstract

At the present time the direct laser engraving (DLE) technology is the most economical and ecological one to produce flexographic printing plates. But small resolution caused by lasers with a wavelength of 10.6 μm led to insufficient quality of final print production. Thus an actual problem is the resolution increasing of DLE process, which will lead to increased quality of prints. The aim of this paper is to present the method of resolution increasing of direct engraving equipment. The calculation and design of an optical telescope intended to increase the resolution of the laser apparatus has been carried out. Testing of the performance of the telescopic system has been performed by calculating the distribution of the intensity of radiation in the focus of the optical system of the apparatus with and without a telescope with the help of a specialized application for optical designing, ZEMAX. A range of drawings and the simulation of a 3D model of the telescope have been done in the SolidWorks design application based on the conducted calculations of the optical system. The telescope then has been made and incorporated into the laser-optical system of the laser engraving device. The quality of focusing of the optical system before and after the modernization has been studied by engraving on a thermo sensitive film of a specially created test-scale that allows determining the convex caustic shape of the beam after its focusing by the optical system. During the comparative analysis of the laser engraving device before and after the optical system upgrade using a test image, it has been found that its technical parameters with respect to the resolution have been doubled.