Abstract: A light source (1) sends towards an object under test (5) a light beam (2) with such a size as to encompass the object (5). Past the object, the beam (2) is processed by an optical processing system (6), comprising a band-pass spatial filter (8) located in the Fourier Plane of a converging lens (7), the object (5) being located in the front focal plane of that lens. The filtered beam is collected by a detector (10) that generates an electrical signal representative of the intensity of the field distribution associated with that beam. A system (11) for processing the electrical signal comprises a band-pass filter (12) with temporal cut-off frequencies corresponding with the spatial cut-off frequencies of the spatial filter in the optical processing system (6) and obtains the value of the requested quantity form the electrical signal.

Abstract: Apparatus for measuring an object (4) with at least one rectilinear edge or profile (4a, 4b) parallel to a given direction (y), comprising: a laser source (1) which emits radiation (2, 2a) which impinges on the said edge or profile; a first cylindrical converging lens (5) the directrices of which are parallel to the direction (y), disposed downstream of the object (4); a spatial filter (6) disposed in the focal plane (A) of the first converging lens (5); a second converging lens (7) disposed downstream of the spatial filter (6); and photosensors (8) disposed in the focal plant (F) of the second converging lens (7).