Abstract: An optical imaging device (PL), in particular an objective for semiconductor lithography, is provided with at least one system diaphragm. The system diaphragm comprises a multiplicity of mobile plates, which are rotatably mounted. The plates have a spherical curvature.

Abstract: An optical imaging device (PL), in particular an objective for semiconductor lithography, is provided with at least one system diaphragm. The system diaphragm comprises a multiplicity of mobile plates, which are rotatably mounted. The plates have a spherical curvature.

Abstract: A telescopic boom especially for deploying a solar array on a spacecraft comprises, instead of the usual compressed gas extender means or the known threaded rod and nut combination, a flexible member extending in the longitudinal direction of the boom and movable in that direction to pick up and extend the tubular boom sections one after another in sequence. The member may be an endless sprocket chain driven by an electric motor and entrained around a wheel mounted at a forward end of a pillar which extends inside the boom to a position near the outer end of the unextended boom, the chain having regularly spaced increased thickness link-plates for engaging matching abutment surfaces of the tubular sections to extend them. As one section comes to its fully extended position, it shifts the next to a position in which it too will be engaged by the chain.