Non-contact diameter measuring method and apparatus

Abstract

A non-contact diameter measuring device measures the diameter of a stationary or rotating round object by measuring the difference in the angle of reflection of a light beam scanned along part of the circumference of the object. The scanning beam is repeatedly translated across the object and the angle of the reflected beam is detected at two locations using two angle-sensitive detector detects the position at which the scanning beam is retroreflected (i.e. pointing to the center of the object). The second detector is set at a fixed angle. The distance the beam has to translate across the object to generate the maximum output signal at the two angle sensitive detectors is inversely proportional to the diameter. The diameter is calculated from knowing this distance and the fixed angle between the two detectors. The main advantage of this method is that only a small part of the circumference is required to measure the diameter, thus a wide range of diameters can be covered by a single device.

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