Endoscope with longitudinal compensation capability in response to thermal stress

1. Field of the Invention An endoscope has an outer tube that is joined to an optical head having an observation element at its end, which elements are sealingly fitted forming a first module element. An inner tube sealingly fitted together with a housing containing optical elements form a second module element having the optical components hermetically closed. The second module element is disposed in the first module element having its distal ends rigidly and sealingly fitted together. The housing of the second module elements extends into said optical head of that first module element and is supported therein allowing relative movement between housing and optical head when thermally stressed.