Patent ID: 6226122
Filing Date: 2001-05-01
Classification: G02B

Abstract:
An observation optical system comprising, in order from an object side to an observation side, an objective optical system having a first lens unit of positive refractive power, a second lens unit of negative refractive power and a third lens unit of positive refractive power, an erect optical system, and an eyepiece optical system of positive refractive power for observing an object image formed through said objective optical system, wherein an air separation between said first lens unit and said second lens unit and an air separation between said second lens unit and said third lens unit are made variable to effect variation of magnification,wherein said observation optical system satisfies the following condition:0.8<.beta.t<1.3,where .beta.t is an overall lateral magnification in a telephoto end of said objective optical system excluding said first lens unit, andwherein said first lens unit consists of one cemented lens composed of, in order from the object side to the observation side, a positive lens and a negative lens cemented together.