The performance of bags-of-tasks in large-scale distributed systems

An illuminating unit for endoscopes includes a light guide member and a cover glass disposed forwardly of the light exiting end face of the light guide member and located within an illumination window which is formed in the distal end of the endoscope. The cover glass has an entry and an exit surface through which light passes, at least one of said surfaces being formed with a surface configuration comprised of a plurality of coaxial concave lens portions having different radii of curvature, each concave coaxial lens portion having a radius of curvature which is less than that of the surrounding lens portion. The aforesaid surface configuration may be formed upon either the entry or exit surface of the cover glass or both of said surfaces. In the two former cases, the remaining one of the entry and exit surfaces may be provided with a concave lens surface having a uniform radius of curvature.