Conoscopic systems

Conoscopic holography was discovered in 1985 by Sirat and Psaltis. Two complementary techniques of measuring both distance and shape were developed. Conoscopy is a technique of incoherent interferometry. It is an active technique and requires the use of structured light projected on to the object. In the most simple case, a point is projected onto the object; this is the conoscopic probe. The other practical case is the projection of a line onto the object, this being the conoscopic profilometer. Conoscopic holography is a holographic technique. It is a passive technique which analyses the light coming naturally from the object. Conoscopic holography is more difficult to realize than conoscopy since it requires more sophisticated components. However, application test beds are under development. The two techniques were initially developed scientifically and technically at California Institute of Technology between 1984 and 1986 and then at ENST in France. The aim of this research was initially to understand the physical principles of conoscopy and conoscopic holography. The second step has been to demonstrate the efficiency of conoscopic holography as a two-dimensional and its basic feasibility as a three-dimensional imaging system. The third step has been to develop simple accurate rangefinding devices based on conoscopy