Measurement of the Actual Contact Area of Details by the Power of a Reflected Light Beam Directed to a Contact Surface Covered with a FilmArkadiy Titov, Anna Sandulyak, Mikhail Baharev and Alexander SandulyakITM Web Conf., 22 (2018) 01014DOI: https://doi.org/10.1051/itmconf/20182201014