TELEPHOTO LENS SYSTEM

摘要

PROBLEM TO BE SOLVED: To obtain a telephoto lens system capable of highly precisely inspecting an object at a finite distance, performing an image processing, and also, capable of obtaining a stable resolution performance with less focal movement when the wavelength of a light source is visible light and when the light is the mixture of visible light and near infrared light. SOLUTION: Regarding the telephoto lens system constituted of four groups, that is, a 1st lens group having positive power, a 2nd lens group having positive power, a 3rd lens group having negative power and a 4th lens group having positive power in order from an object side, the system is constituted of six or less lenses as a whole, the 1st lens group is constituted of a positive/negative or negative/positive doublet, and the telephoto lens system satisfies the following conditional expression (1). (1) 0