Signal processing unit for laser tracer providing submicron-accuracy diameter measurement

The advent of the space age and, nanotechnology, together with consumer demand for the timely delivery of good quality products has resulted in greater emphasis being placed on instrumentation, in terms of accuracy, tolerance and speed. The authors look at the design of a stand-alone laser tracer signal processing unit that permits diameter measurements to be made on-line at selectable frequencies of up to 500 measurements per second. The system is of the noncontact type and can measure diameters up to 2·0000 mm with a resolution of 0.5 μm. It is shown that with two of these devices connected together, and by externally introducing a means of measuring the distance between the devices, diameters of up to 220·000 mm can be measured; however, the total system resolution is then limited by the resolution of the system that measures the distance between the devices. Suggestions are made as to how this system could be incorporated into an automatic inspection system for quality control