Development and validation of a surface profiling system for end of line monitoring of microstructured elastomer seals based on chromatic confocal microscopy

Abstract

Chromatic confocal surface profilometry has been a widespread technique in industrial applications for many years. Beside excellent resolution and speed, the contactless measuring capability make it ideal in applications where no physical contact is possible, (e.g. measurement of fluid levels), or where physical contact could damage the part to be inspected (e.g. high precision lenses or coatings). Since these systems rely on the spectral analysis of the reflected light, if the reflectance of the examined specimen is low, the measurement speed and accuracy can substantially degrade. In this paper, we present a high-intensity chromatic confocal surface profiling system based on an infrared superluminescent diode and custom designed optics. Due to its very small etendue, the superluminescent source allows orders of magnitude higher illumination intensity than conventional LED sources. We mounted the designed optics on a 5-axis precision positioning stage, which allows topography measurements along 5° of freedom on complex shaped samples, with a wide focus range (>350 μm) and a high scanning speed (>10 kHz). The paper presents the design procedure and the figures of merit of the device, and measurement results of microstructured elastomer samples are also shown.