Abstract: Optical viewing or projection device, comprising at least two objectives (L.sub.1 L.sub.2) whose optical axes (x.sub.1 x'.sub.1 ; x.sub.2 x'.sub.2) are parallel to a general axis of symmetry (xx') of the device, endowed with a focusing system permitting the formation of images or viewing in a fixed reference plane (P'.sub.0), by means of simultaneous translation of the objectives in parallel to the general axis of symmetry, and comprising means for reducing the parallax produced by the objectives, the means for reducing the parallax including a system of parallel-faced plates (M.sub.1 M.sub.2) which has the general axis of symmetry (xx') of the optical device as its axis of symmetry, wherein a parallel-faced plate is placed between each objective (L.sub.1, L.sub.2) and the fixed reference plane (P'.sub.

Abstract: The invention relates to a crucible for the growth of epitaxial layers of chemical compounds formed from several chemical elements by means of epitaxial growth from the liquid phase comprising an elongated support (72), on which a movable part (73) slides longitudinally, the elongated support comprising at least one recess for accommodating a substrate (76) on which is to be deposited at least one epitaxial layer, the movable part comprising at least one cavity (77) receiving a mother source (79) formed from initial epitaxy materials, the cavity having on the surface adjoining the elongated support a lower opening whose dimensions correspond to the dimensions of the substrate (76) present therein.

Abstract: A gamma camera (1), has a scintillation block with an entrance window (10) constituted by a mechanically stiff supporting structure which very slightly absorbs X and gamma rays. The entrance window (10) supporting the scintillation block (3) may be constituted by a honeycomb structure of a light material.