High resolution distance measurement of laser-induced diffraction signals by digital signal processing

A diameter measurement method is presented offering an extremely good resolution, high signal-to-noise ratio and a high measuring rate. The measuring principle is based on the evaluation of the diffraction of a laser beam at fibers or thin wires for the determination of the diameter. The high accuracy of up to 0.1 /spl mu/m resolution and the robustness are obtained by using digital signal processing and with the aid of a signal processor. Signal processing methods are discussed for a laser-induced diffraction signal by using the fast Fourier transform. The measuring method was implemented on a signal processor board placed in a PC. The diffraction signal is generated by a measuring head, consisting of a semiconductor laser collimator and charged coupled device line scan camera. The measuring head and evaluation unit are applicable as a complete measuring system for quality assurance in the production of fibers and thin wires. Experimental results are presented.<
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