Abstract: In a device for performing measurements on at least partly transparent objects such as optical fibres a radiation beam is directed on the object. The radiation deflected by the object is imaged by means of a lens system (321, 322) on a radiation-sensitive detection system (330). As a result of refraction on interfaces between areas having a different refractive index (311, 312) in the object and between the object and the surroundings (315), dark or light bands corresponding to the projection of the interfaces are produced on the radiation-sensitive detection system (330). Thus measurements can be performed on the internal structure of the object.

Abstract: A lens having a spherical surface and an aspherical surface curved relative to each other to minimize coma for a large diffraction-limited field and a large numerical aperture.

Abstract: A solar collector includes a plurality of elongate parallel reflectors mounted for rotation about their respective longitudinal axes, together with mechanism coupled to the reflectors for simultaneously rotating the same. An elongate absorber is arranged parallel to the reflectors for collecting solar radiation focussed thereon by the reflectors. Tracking means including two solar sensor reservoirs containing a vaporizable/condensible liquid working medium is provided for rotation of the reflectors to control the focussing of solar radiation on the absorber.

Abstract: A pressing block for a phonograph or video record press in which ducts for cooling and heating media for the die are formed by a thin layer of a porous heat-conducting material provided between two thin metal sheets and bonded thereto. The assembly is connected on its side remote from the die to a supporting element of at least partially heat-insulating material.