| 摘要 |
PROBLEM TO BE SOLVED: To obtain an observation optical system in which little aberrations based on eccentricity arises when image blur is corrected by turning a lens group, and a lens group can be easily turned by small driving force. SOLUTION: The observation optical system has an objective OBJ, an erect prism P and an ocular OCL in order from an object side to an observation side, wherein the objective OBJ has a fixed lens group Lf which is immovable for vibration isolation and has positive refractive power, and a movable lens group Lr which rotates with an axis perpendicular to an optical axis as the axis of rotation to thereby displace the image forming position of the objective OBJ in a direction perpendicular to the optical axis and has negative refractive power in order from the object side to the observation side. The observation optical system satisfies a condition: 0.4<Lro/fo<0.55 when a distance from the lens surface on the observation side of the movable lens group Lr to the image forming surface of the objective OBJ is defined as Lro and the focal distance of the objective OBJ is defined as fo. COPYRIGHT: (C)2008,JPO&INPIT
|
