Patent ID: 6377399
Filing Date: 2002-04-23
Classification: G02B

Abstract:
An image stabilizing optical system for observation comprising in order from an object-side to an eyepiece-side:an objective lens system including a first lens group having positive refractive power, a second lens group having negative refractive power and an erecting prism system; and an eyepiece lens system, wherein said objective lens system forming an erected image, the erected image being formed on the eyepiece-side of the erecting prism system, said eyepiece lens system magnifying said erected image to be observed and having positive refractive power as a whole, the first lens group includes at least one positive lens and one negative lens, and comprises one composite lens composed of two lenses cemented together and one positive simple lens, in this order from the object side, the second lens group consists of one negative lens and adjoins said erecting prism system from the object-side; and said second lens group is moved in a direction substantially perpendicular to an optical axis, thereby deviating the image so as to stabilize the image, and wherein the following expressions are satisfied: 0.25&lE;f1/f&lE;0.75; 0.05&lE;D/f&lE;0.6; 0.2&lE;D/f1&lE;0.8; 40&lE;&ngr;d2, â€ƒand âˆ’2.2&lE;f2/f1&lE;âˆ’0.25, â€ƒwhere f is a focal length of the objective lens system, f1 is a focal length of the first lens group, f2 is a focal length of the second lens group of the objective lens system, D is a distance between principle points of the first lens group and the second lens group, and &ngr;d2 is the Abbe number for the d-line of the negative lens of the second lens group.