Optical system for the measurement of the surface topography of additively manufactured parts

Abstract

Additive manufacturing (AM) is now regularly used for customised fabrication of parts with complex shapes and geometries. However, the large range of relevant scales, high slopes, step-like transitions, undercuts, alternation between dark and overly bright regions and other complex features present on the surfaces, in particular of metal additive parts, represent a significant challenge for current optical measurement technologies. Measuring surfaces with such complex features requires high numerical aperture (NA) optics, and state-of-the-art systems commonly include optics that can only reliably acquire surface topographies over a small field of view (FOV), typically tens or hundreds of micrometers. Such measurements are often insufficient for practical applications. Here, we present an optical system that features a large NA ($\gt$0.3) and a wide FOV $2.9\,\times\,2.9$ mm, capable of measuring AM parts in a single measurement, without the need for lateral stitching to increase the FOV. The proposed system exhibits optical properties that provide facility for large-field, high-resolution measurement of industrially-produced additively manufactured parts.