Since many industrial materials have micro or submicro structures on the surface or subsurface, utrahigh-resolution is required in the inspection of these materials. Ultrahigh-resolution optical coherence tomography uses broadband light sources to achieve axial image resolutions on the scale of a few microns. We have been investigating an ultrahigh-resolution spectral-domain optical coherence tomography (SD-OCT) system using supercontinuum sources (SC) in free space. The effective SC spectrum has a full width at half maximum of 230 nm centered around 665 nm, and the imaging setup has an ultrahigh axial resolution of 0.9 µm in air, and a lateral resolution of 3.9 µm, with the system measurement range being 0.6 mm in axial direction. At a 50 µm axial position, the sensitivity can be 63 dB with 28600 axial scans per second at 2048 pixels per axial scan. Images of polystyrene microspheres solution with an average diameter of 5 µm and different sizes of industrial abrasive papers are presented to illustrate the performance of the system.
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