| 摘要 |
PURPOSE:To make a zoom lens clear and the variable power attain the highest level, by constituting the lens with the 1st group having a positive power, 2nd group having a negative power, 3rd group having a negative power, and 4th group which is an image forming system, and specifically setting the relation between its combined focal length and the shorted focal length of the whole system. CONSTITUTION:From the object side the 1st group I having a focussing function and positive power, 2nd group II which is movable along the optical axis at the time of zooming and has a function that principally changes the focal length and negative power, 3rd group III which is movable along the optical axis at the time of zooming and has a function that pricipally maintains a focussing position constantly and negative power, and 4th group IV which is fixed at the time of zooming and is an image forming system are successively arranged. The combined focal length fA from the 1st group I to the front element of the 4th group IVand the shortest focal length fW of the whole system are set so that they satisfy a relation, -0.15<fW/fA<0.5.
|
