ZOOM LENS

• Main Author: FUKAMI SEIJI
• Format: Patent
• Language: English
• Published: 17.01.1997
• Edition: 6
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

PURPOSE: To provide an inner focus four-group type zoom lens having excellent optical performance over the whole variable power range from the wide-angle end to the telescopic end and over an object distance from an object at infinity to an object at the short distance. CONSTITUTION: This zoom lens comprises, in order from the object side, a first group L1 of a positive refractive power fixed at the time of varying the power, a second group L2 of a negative refractive power for varying the power moving on the optical axis while interposing a lateral magnification: -1 times, a third group L3 of a positive or negative refractive power for correcting the fluctuation of an image plane by power variation and a fourth group L4 fixed during the power variation and having image forming action. The first group L1 comprises a eleventh group L11 having at least one positive lens and a negative refractive power as a whole, a twelfth group L12 having at least one positive lens, a combined lens and a positive refractive power as a whole, a 13th group L13 having a combined lens and a positive refractive power as a whole and focusing from an object at infinity to an object at the short distance is performed by moving the twelfth group L12 to the side of the image plane.