Methods of resolution enhancement of laser diameter measuring instruments

•The implementation of diffraction and spectral analysis methods is presented.•The function suggested allows detecting boundaries of object׳s shadows.•The real-time detection algorithm is described for diffraction extreme values.•A method of improvement of resolution is shown on the basis of spectral analysis.

The paper presents the implementation of diffraction and spectral analysis methods allowing 1 μm resolution enhancement of optical instruments intended for measurements of such round wire materials as cables, wires, cords, etc. with diameters exceeding the wavelength (~0.5 mm and large). The transformation function suggested allows detecting geometrical boundaries of object׳s shadows that are used to calculate its diameter independently from its location in the gaging zone. The real-time detection algorithm is described for diffraction extreme values in the analog video signal produced by the charge-coupled device sensors. A method of additional improvement of resolution is shown on the basis of spectral analysis.