Characterization of high-reflectance diffuse coatings for 3D- printed optics

Low-cost diffuse reflectance coatings were characterized for use on 3D-printed optical assemblies. Barium sulfate (BaSO 4) and titanium dioxide (TiO 2) suspensions were deposited on polylactic acid (PLA) substrates through a multilayer drop-casting process with an acrylic binder, and compared to commercial white paints and Spectralon ® standards. Hemispherical reflectance was measured using an integrating sphere over the 300 nm to 1000 nm range, while angular scattering was assessed from −85°to 85°using a collimated xenon source. BaSO 4 achieved the highest broadband performance, with a mean hemispherical reflectance of 98.9 % and a mean angular deviation of 6.3 % from the ideal cosine law. TiO 2 showed slightly lower reflectance (96.6 %) and stronger angular directionality, consistent with its smoother and glossier surface finish. Commercial acrylic coatings exhibited markedly lower reflectance (70 % to 86 %) and large deviations from cosine behaviour, while office paper provided good diffusivity but insufficient spectral uniformity. The results demonstrate that a simple BaSO 4-based coating can deliver stable, broadband, and highly diffuse reflectance when applied to 3D-printed substrates, enabling the fabrication of low-cost optical diffusers and reflectance references for custom laboratory setups.