Patent ID: 7869139
Filing Date: 2011-01-11
Classification: G02B

Abstract:
1. An imaging optical system comprising: a. an optical housing; b. an objective lens system disposed at one end of the optical housing and having a focal plane; and c. a modular afocal variator disposed within the optical housing in optical series with the objective lens system, wherein the modular afocal variator comprises a first positive lens system, a central negative lens system, and a second positive lens system, where the central negative lens system is positioned between the first and second positive lens systems and is able to be moved continuously towards and away from the first positive lens system and towards and away from the second positive lens system, wherein the modular afocal variator is positioned so that the distance between the first positive lens system and the focal plane is 66% (±15%) of the focal length of the first positive lens system, and the distance between the second positive lens system and the focal plane is 100% (±15%) of the absolute value of the focal length of the central negative lens system, and wherein the modular afocal variator provides focus to the optical system while maintaining essentially constant magnification throughout the focal translation.