Abstract: Color selection means for color display tubes is provided comprising a curved mask and a rectangular frame supporting the mask, which frame comprises four parts. To realize a light and nevertheless rigid frame construction, at least two oppositely located frame parts are formed by folded pipes which each have a re-entrant wall with an edge following a curved path. The mask is clamped onto these edges so that the curvature of the edges determines the curvature of the mask.

Abstract: An apparatus for manufacturing an object having a relief structure on a surface thereof by pressing a first element provided with a negative of the relief structure against a second element to form the relief structure in the surface of the second element. The apparatus includes the first element and two pressure members having pressure surfaces facing each other and opposing both of the elements, the pressure members being moveable relative to each other in a direction transverse to the pressure surfaces.

Abstract: A method of manufacturing an object having a surface structure, the method employing pressure members (3, 5) which are movable relative to one another and which have facing pressure surfaces (23, 25). A first element (51) and a second element (53) having a relief on one surface are pressed against one another to provide the second element with a microstructure by cold deformation. During pressing use is made of a pressure body (27, 29) which is interposed between one of the pressure members and one of the elements and which is made of a material having a characteristic parameter equal to the quotient of the Poisson's ratio and the modulus of elasticity of the material, which parameter differs less from the corresponding parameter of the material of the relevant element than from the corresponding parameter of the material of the relevant pressure member.