Abstract: An objective for a camera defines an axis and includes an inner objective element and an outer objective element at least partially surrounding the inner objective element. The inner objective element and the outer objective element conjointly define an interface and are mounted so as to be rotatable relative to each other about the axis. A sealing system is disposed at the interface between the inner objective element and the outer objective element and the sealing system includes a plastic foil in contact engagement with the inner objective element and the outer objective element.

Abstract: An apparatus for the thermal compensation of an optical system is disclosed. The apparatus comprises a housing, at least one optical element adapted to be displaced relative to the housing, and at least one piston-and-cylinder unit positioned directly between the housing and the optical element. The piston-and-cylinder unit acts on the position of the optical element within the housing. It contains a fluid. The coefficients of volumetric thermal expansion of the piston, the cylinder and the fluid are selected such that for a predetermined change in temperature of the apparatus a defined relative displacement between the piston and the cylinder takes place which compensates the change of the optical properties of the optical system caused by the change in temperature. The fluid is a polymer system.