Observation instrument for at least one hidden marking

摘要

The observation instrument is used on a lens (L) under test, which is radiated with an illuminating light beam. The observation of the hidden marking of the lens (L), is facilitated by a shadow of the lens formed by the illumination light. The illuminating light is a collimated light beam. A screen (4) is arranged behind the lens (L), and the hidden marking of the lens is observed across the shadow of the lens, which is projected on the screen (4). Alignment facilities are provided for the alignment of the shadow on the hidden mark.