VARIABLE POWER OPTICAL SYSTEM HAVING VIBRATION-PROOF FUNCTION

摘要

PROBLEM TO BE SOLVED: To obtain a variable power optical system having a vibration-proof function which optically corrects the blur of a taken image when the variable power optical system is vibrated so as to obtain a still image. SOLUTION: The variable power optical system is constituted of four lens groups, that is, a 1st group fixed for variable power and focusing and having positive refractive power, a 2nd group having a variable power function and having negative refractive power, a 3rd group having positive refractive power and a 4th group having both a correcting function to correct an image surface fluctuated by the variable power and a focusing function and having positive refractive power in order from an object side. The 3rd group is constituted of a 31st group having negative refractive power and a 32nd group having positive refractive power. The 32nd group is moved in a perpendicular direction to an optical axis so as to correct the blur of the taken image when the variable power optical system is vibrated. When the focal distance of an entire system at a wide angle end is defined as fW and back focus at a wide angle end when removing an optical member having no refractive power from a final lens surface to an image forming surface is defined as bfW, they satisfy a condition of 3