Patent ID: 6795247
Filing Date: 2004-09-21
Classification: G02B

Abstract:
An optical instrument for observation comprising, in order from the object side:an objective lens system having positive refractive power; an erecting optical system; and an ocular lens system having positive refractive power; whereinan anti-vibration mechanism is used to maintain the erecting optical system at an orientation in space that is stabilized so as to prevent image degradation due to vibrations of the optical instrument for observation; and the erecting optical system is an erecting prism that is constructed so as to satisfy the following Condition (1): 0.25<L/foâˆ’sin &ohgr;<0.5â€ƒâ€ƒCondition (1) whereL is the distance from the lens element surface nearest the object side of the objective lens system to the erecting prism, fo is the focal length of the objective lens system, and &ohgr; is the maximum angle of rotation of the erecting prism relative to the optical axis of the optical instrument for observation in order to maintain the spatial orientation of the erecting prism substantially constant in space when correcting for sudden changes in orientation of the optical axis.