| Bausch & Lomb Metrogon |
(in Fairchild K-22 Aerial Camera Replacement Lens cone)
image by Dirk HR Spennemann (Image rights)
The Metrogon is an extra-wide field photographic lens used extensively by the US military for use in aerial photography. The design is by Bausch & Lomb based on the Topogon design by Zeiss. It is composed of a double-Gauss design with an extremely curved meniscus to provide a 90° field of view. The lens is symmetrical front to back. The two outer positive elements are of high index crown glass while the two inner negative elements are of a high index flint glass. The lens was used in Fairchild K17C, KA3, K-22, T-11, KC-1, KC-1B, and KC-9A aerial cameras.