SIGNAL-PROCESSING UNIT FOR LASER TRACER PROVIDING SUBMICRON-ACCURACY DIAMETER MEASUREMENT

The advent of the space age and, more recently, nanotechnology, togeth er with consumer demand for the timely delivery of good quality produc ts has resulted in greater emphasis being placed on instrumentation, i n terms of accuracy, tolerance and speed. This paper looks at the desi gn of a stand-alone laser tracer signal processing unit that permits d iameter measurements to be made on-line at selectable frequencies of u p to 500 measurements per second. The system is of the non-contact typ e and can measure diameters up to 2.0000 mm with a resolution of 0.5 m um. It is shown that with two of these devices connected together, and by externally introducing a means of measuring the distance between t he devices, diameters of up to 220-000 mm can be measured; however the total system resolution is then limited by the resolution of the syst em that measures the distance between the devices. Suggestions are mad e as to how this system could be incorporated into an automatic inspec tion system for quality control.