Analysis on the depth of focus in flying optics

Abstract

Based on a simplified model of Gaussian beam focusing, in which nontruncating, thin-lens, aberration-free, and on-axis optical systems are assumed and the thermal-lensing effect is neglected, a general and concise expression is derived to describe the variation of 1/e(2) radius of the focused beam as a function of input beam waist to lens spacing, lens-to-target plane spacing, input beam Rayleigh range, and focal length of lens. From this expression, we get the depth of focus (DOF) of flying optics with a fixed flying range, which is used as a merit function to determine the optimal solutions for system parameters. The results are very useful in the design and analysis of flying optics in laser material processing. Finally, a practical example describing the optimization of the output coupler for CO2 laser resonator is given. (C) 1998 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(98)02505-7].