Today’s high brilliance Laser sources cause huge thermal effects on optical components, affecting process stability. This paper shows the holistic approach to the improvement of objective lenses to minimum thermal effects as focus shift. A new approach to the transient simulation of thermal behavior, starting with FEM Analysis, analytical description of surface deformation and refraction index distribution resulting in transient plot of image quality changes by optics design simulation. Optics material selection and characterization of bulk material, surface and coating by newly developed measurement techniques is shown. The optimum setting of opto-mechanical design, material selection, surface finish and coating allows to produce lenses with focus shift by 0,05times the Rayleigh range @1064nm, 4kW multimode at reasonable price.