A comparative investigation for flatness and parallelism measurement uncertainty evaluation using laser interferometry and image processing

Abstract

Optical flats and parallels are precisely polished surfaces, customarily used as reference standards for quality assurance of fabricated components in numerous industries. In-line with the quality control, reliable flatness and parallelism measurements of optical flats and parallels through appropriate measurement methodologies are immensely significant. The present study describes a comparative investigation for flatness measurement of an optical flat with an effective diameter of 150 mm and parallelism measurement of an optical parallel with an effective diameter of 30 mm, through laser interferometry and image processing using MATLAB, followed by measurement uncertainty evaluation for perceptive and subjective confirmation of the measurement process. Outgrowths of both the approaches have been contemplated to be in significant congruence; the flatness value observed using laser interferometry is 120.50±30 nm whereas the flatness value observed using image processing is 118±32 nm. The parallelism values using laser interferometry is 0.44±0.009 arc second and using image processing is 0.36±0.01 arc second.