Metrological detection photo-electric system - uses optical assembly with three diffraction gratings with specified geometrical inter-relationships

摘要

The optical location system is based upon six main components; a lamp source (1), a convergent lens (2), three linear diffraction gratings (3, 4, 5) in a mutually parallel arrangement, and a photocell (6). The spacings of the diffraction gratings (3, 4, 5) are respectively equivalent to three light frequencies (f1, f2, f3). The geometrical arrangements are such that distances (U, V) between the first/second and second/third gratings are related by f2/f1 = V(U + V). Similar expressions relate the effective apertures. Alternative geometrical arrangements include angled mirror reflectors. The photocell forms part of an electronic circuit and may also have a periodic structure, including semi-conductors, for the detection of Moire fringes.