Shapiro and Shapiro
Variable magnification observation apparatus
 A variable magnification observation apparatus capable of changing the magnification thereof includes an optical fiber having an exit surface for emitting an illuminating light beam at an angle corresponding to a predetermined numerical aperture, an aperture stop member disposed near the exit surface of the optical fiber, a field stop member disposed at a predetermined distance from the aperture stop member, and a negative lens removably inserted in the optical path between the aperture stop member and the field stop member. 
Nippon Kogaku K. K.
G G
G02B G02B
additional inventional
Kinya
Kato