<title>Optoelectronic feedback system for measuring the shape of large format objects</title>

Abstract

A portable feedback opticoelectronic system for measuring the shape of large-format objects is presented. It is based on the projection of phase-shifted interference fringes on the measured surface with subsequent digital processing of the interference patterns. The density and orientation of the projected fringes are set by an adjustable Michelson's interferometer, utilizing a phase-shifting mirror with three-point suspension and low-voltage control (0-12 V). The opticoelectronic feedback determines the value of the phase steps and monitors the level of the tolerable vibration noise. The system also includes a measurement CCD camera with high resolution and a personal computer with the relevant software for the measurements. Laser light sources in the visible and near-JR region with a power of up to 10 W in continuous mode can be used. Narrow-band interference filters with high transmittance make possible measurements under normal, daylight illumination ofthe working premises. When powerful lasers are used (for example, 10 W CW Ar laser at 488 nm) the mirrors should have dielectric coatings. The interferometer is sealed and underpressure with an inert gas (Ar) is maintained in it in order to protect the optical elements against dust, burning and coherent noise. A description is made of the design, operating procedures, theoretical background and experimental results from measurements of real objects in working conditions.