Abstract: Refractometer for measuring the refractive index of a medium (2), using the limiting angle method. A source (4) illuminates a source slit (5) which has as its image with respect to an optical system (S) one of the parallel and regularly spaced slits (5') of a grille (6) fixed perpendicular to the optical axis each of the slits (5') corresponding to an angle of incidence of the optical beam on a prism (3). Turning of a rhombohedron causes the image (5') of the source slit (5) on the grille (6) to be successively on each of the slits (5') of the grille (6). The pupil (L.sub.1), located in the plane of the source, is conjugate with the exit face (8) of the prism (3) and remains stationary when the image (5') of the source slit (5) is moved over the grille (6).

Abstract: Apparatus for guiding aircraft to predetermined parking locations, comprising an optical assembly centered on a reference point, and adapted to provide the pilot in the moving aircraft with two images of a reference point located on the aircraft. When the two images are superimposed, the aircraft has reached the desired location.

Abstract: An optical observation instrument including on the one hand a mounting in which are mounted a convergent objective lens and a convergent eyepiece and on the other hand a disc formed of optical fibers arranged so as to reverse the image given by the objective lens and connected to the mounting by way of an articulation and held in a stable position, the front face of this disc being substantially at the focus of this objective lens.

Abstract: A laser generator (1,2,3) is arranged to generate successive pairs of pulses. Two light receivers (10,11) in the vicinity of the laser generator receive echos of the pulses as reflected from a target and a processing circuit (15) calculates the component of wind speed blowing across the laser axis between the laser generator and the target. The device can be combined with laser ranging means and used for artillery control.

Abstract: Apparatus for conducting firing adapted to the aiming of a cannon movable bearing and in elevation around a turning axis as a function of aim values given by a firing table corresponding to the cannon and other parameters of firing. The apparatus comprises a telescopic sight with an optical deviator element for displacement of the line of sight, the optical deviator element being mounted on a support coupled in bearing and in elevation with the cannon and being subjected to the action of a cam whose profile is determined by the aim values from the firing table and which is coupled to a motor controlled by a rangefinder device whose transmission and reception beams are connected in bearing and in elevation to the axis of the observation scope of the telescope.