Showing papers by "Pietro Ferraro published in 1996"

A reflective grating interferometer for measuring the refractive index of liquids

Abstract: A simple and compact interferometric system, which makes use of a reflective-type diffraction grating, has been developed for measuring the refractive index of liquids. This paper describes the details of the system, which is easy to align and compact, and a series of measurements performed on liquids. An analysis of the accuracy of the method is presented, which is proven to be within one part in .

Measurement of 3D position of large objects by laser scanning system to aid the fabrication process of composite aerospace components

Abstract: Istituto di Cibernetica del C.N.R., Via Toiano 6, Arco Felice (NA) 80072 ItalyABSTRACTOptical scanning systems can be used for measuring the 3D position of objects. In the case of large objects large errors canoccurs depending from the area to be covered by the laser scanning system and from the accuracy obtainable on angularposition of driven rotating mirrors. A numerical simulation has been performed to evaluate errors in a case of large objects(2mx2m). This is a typical situation that is encuntered when a scanning laser system is applied to aid the fabricationprocess of composite materials for aircraft components. Criteria used to perform the numerical simulation are describedand results are reported for a number of cases could be met in a real applications.Keywords: optical scanners. tridimensional position measurements, optical metrology, composite materials.1. INTRODUCTIONA variety of fabrication processes in different fields of applications ranging from textile to aerospace industry requiretracing of reference lines on the surface of a tool, to accomplish various operations such as cutting, positioning, drilling,etc. Tracing operations are usually performed by using handhold templates. In the aerospace industiy, expecially in thefabrication process of components made of composite materials, the positioning of different layers is a time consumingoperation which usually requires a precision of about 3 mm on the surface plane. In this case, a scanning laser system canbe used to project temporarily visible reference lines according to the engineering requirements, thus saving costs andimproving the automation degree of the process. Commercially available laser scanning systems can be connected to theComputer Aided Design (CAD) systems to receive directly the coordinates data of the project. If the position of the toolsurface with respect to the reference frame of the scanning laser head is known in advance, the projection of the reference