title: Freeform manufacturing of a microoptical lens array on a steep curved substrate by use of a voice coil fast tool servo.
abstract: We report what is to our knowledge the first approach to diamond turn microoptical lens array on a steep curved substrate by use of a voice coil fast tool servo. In recent years ultraprecision machining has been employed to manufacture accurate optical components with 3D structure for beam shaping, imaging and nonimaging applications. As a result, geometries that are difficult or impossible to manufacture using lithographic techniques might be fabricated using small diamond tools with well defined cutting edges. These 3D structures show no rotational symmetry, but rather high frequency asymmetric features thus can be treated as freeform geometries. To transfer the 3D surface data with the high frequency freeform features into a numerical control code for machining, the commonly piecewise differentiable surfaces are represented as a cloud of individual points. Based on this numeric data, the tool radius correction is calculated to account for the cutting-edge geometry. Discontinuities of the cutting tool locations due to abrupt slope changes on the substrate surface are bridged using cubic spline interpolation.When superimposed with the trajectory of the rotationally symmetric substrate the complete microoptical geometry in 3D space is established. Details of the fabrication process and performance evaluation are described.
authors: Fraunhofer Institute for Applied Optics and Precision Engineering Albert-Einstein-Str. 7, 07745 Jena, Germany. sebastian.scheiding@iof.fraunhofer.de
authors: Sebastian
authors: S
authors: Scheiding
authors: Allen Y
authors: AY
authors: Yi
authors: Andreas
authors: A
authors: Gebhardt
authors: Lei
authors: L
authors: Li
authors: Stefan
authors: S
authors: Risse
authors: Ramona
authors: R
authors: Eberhardt
authors: Andreas
authors: A
authors: Tünnermann
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005246:Feedback; D007909:Lenses; D008280:Magnetics / Q000295:instrumentation*; D008904:Miniaturization