US Patent 6955644 Autoclavable endoscope

A rigid endoscope includes an outer housing subassembly that supports an optics subassembly. The outer body subassembly includes concentric tubes with optical fiber for providing object illumination. The optics subassembly includes a tubular sheath sealed at both ends. A compression spring is positioned between a proximal most relay lens element and a distal most eyepiece element. The spring exerts a distally acting force on the elements of an optical objective and relay lens system. It also produces a proximally directed force on optical elements in the eyepiece. This minimizes differential thermal expansion stresses during autoclaving operations.