Abstract

GRIN rods are now used in the manufacture of small endoscopes. A common design for the penetrating optics of these instruments is an objective with a cover glass followed by a relay of one of more periods all cemented together into a monolithic optical train. Such an endoscope has its entrance aperture within the objective, which makes it impossible to use with them the most common line-of-sight prisms. It has been discovered that these systems have an entrance tunnel with the shape of a hyperboloid of one sheet. By a variation of the length of the objective it is possible to adjust the position and scale of this tunnel. In particular, it is possible to move the hyperboloid uplight so that its waist coincides with the narrow apertures of the most common line-of-sight prism so that vignetting is eliminated or at least minimized.

© 1992 Optical Society of America