Abstract: A testing device is provided for performing four-point fatigue strength tests of a sample by applying alternating bending stresses to the sample. The device includes four rotary joints. Each rotary joint includes a pair of individual, spaced-apart rollers so that a sample can be guided between the individual rollers of the respective pairs of rollers. Each roller is rotatable about its own longitudinal axis. First and second plates are adapted to be fixed in a force introducing machine so that they are relatively movable toward and away from one another. Four holders are provided, each for supporting a respective one of the rotary joints. Two of the holders are mounted to the first plate, with the third and fourth holders being disposed between the two holders and being mounted to the second plate. Each holder mounts its rotary joint so that the individual rollers of the rotary joint are rotatable about a common rotation axis.

Abstract: Variable focus lens systems having a fixed divergent lens element, a movable convergent lens component, and a basic objective lens group having a fixed lens element and a movable lens component, the movable lens component of the basic objective lens group being coupled to the convergent lens component for movement therewith in the same direction but over a proportionally lesser distance.

Abstract: An objective of variable focal length affording an aperture ratio of about 1:1.0 to 1:1.4 for narrow film projectors and microscopes comprising at least six lens members separated by air spaces, characterized by the following construction and arrangement of the lens members:A. a first lens member confronting the longer conjugate or the projection screen, respectively, said first lens member having dispersing power and the surface thereof with the larger radius of curvature confronts the film or the shorter conjugate respectively;B. a second displaceably arranged lens member having collective power and containing outer surfaces of approximately the same radii of curvature;C. a third collecting lens member having differently curved outer surfaces, wherein the surface confronting the shorter conjugate or the film, respectively, possesses the larger radius of curvature and separated from the lens surface of the following fourth lens member by a small air space;D.

Abstract: A wide-angle objective composed of six components separated by air spaces and located three at the object side and three at the image side of a diaphragm, said six lens components taken in consecutive order from the side of the object comprising: a first lens component with dispersing refractive power; a second lens component which follows an air space composed of a dispersing meniscus lens component curved towards the object side; a third lens component which follows a small air space and possessing a collecting refractive power and having a strongly convex curved outer surface facing the object side; a fourth lens component which follows the diaphragm space, said fourth lens component having a collecting refractive power; a fifth lens component comprising a meniscus lens component which is curved towards the image and assembled preferably from at least one dispersing and collecting lens; a sixth lens component with dispersing power which follows an air space and composed of at least one meniscus lens member