Measurement of cylindrical objects by laser telemetry: a generalization to a randomly tilted cylinder

The generalization of a new method for robust noncontact diameter determination of cylindrical objects is studied. The principle is based on laser telemetry under structured lighting, where laser planes create lines on the object under test, which are observed by a charge-coupled device camera. The calculation is performed by means of what we call the "three-tangent method" which was proved as the most reliable one taking into account the particular characteristics of the curves. So far, the object was assumed standing perpendicularly to the camera plane; we extend the method to the diameter measurement of cylinders randomly tilted in regard to this plane. Experimental results obtained on a pre-prototype setup are given. A general accuracy of about 1% for cylindrical objects of 10 to 30 cm in diameter is claimed for distances up to 2 m.