Abstract: An apparatus for the non-contacting measurement of rod-shaped objects contains a telecentric, F-theta-corrected objective which comprises two catadioptric elements. The first catadioptric element is a Mangin mirror and the second catadioptric element is a plane plate mirror-coated at the front, while a third optical element is a meniscus lens. The use of catadioptric elements permits a simplified and inexpensive form of construction which is also compact, as a result of which objects with large dimensions can be measured quickly and accurately. Such an apparatus serves, in particular, for the continuous control of the production of filament-shaped objects.

Abstract: An optical objective for the infra-red wave band, comprising front and rear simple positive lens elements each made of Germanium, said elements being axially spaced by a distance S lying between 0.8F and 1.2F, the rear surfaces of said elements being plane or convex to the front with radii of curvature greater than 10F and the front surface of each element being convex to the front with a radius of curvature less than the radius of curvature of its rear surface.