| 摘要 |
A zoom lens is constituted by, in order from the object side to the image side: a positive first group which is fixed when changing magnification, a negative second lens group which moves when changing magnification, a negative third lens group which moves when changing magnification, and a positive fourth lens group which is fixed when changing magnification. The first lens group is constituted by a 1a lens of a negative meniscus shape, a positive 1b lens, and a positive 1c lens. The second lens group is constituted by a negative 2a lens, a biconcave 2b lens, a positive 2c lens, and a negative 2d lens. The third lens group is constituted by a negative 3a lens and a positive 3b lens. The fourth lens group includes a 4a lens, an aperture stop, and a positive 4b lens, which are consecutively provided from the most object side thereof. |
| 主权项 |
1. A zoom lens consisting of, in order from the object side to the image side:
a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a negative refractive power; and a fourth lens group having a positive refractive power; the first lens group and the fourth lens group being fixed when changing magnification; the second lens group moving from the object side to the image side when changing magnification from the wide angle end to the telephoto end; the third lens group moving to correct fluctuations in an image formation position caused by the movement of the second lens group; the first lens group consisting of, in order from the object side to the image side, a 1a lens of a negative meniscus shape with a concave surface toward the image side, a 1b lens having a positive refractive power, and a 1c lens having a positive refractive power and in which the surface thereof toward the object side has a radius of curvature with a smaller absolute value than the surface thereof toward the image side; the second lens group consisting of, in order from the object side to the image side, a 2a lens having a negative refractive power and in which the surface thereof toward the image side has a radius of curvature with a smaller absolute value than the surface thereof toward the object side, a 2b lens of a biconcave shape, a 2c lens having a positive refractive power and in which the surface thereof toward the object side has a radius of curvature with a smaller absolute value than the surface thereof toward the image side, and a 2d lens having a negative refractive power; the third lens group consisting of, in order from the object side to the image side, a 3a lens having a negative refractive power and in which the surface thereof toward the object side has a radius of curvature with a smaller absolute value than the surface thereof toward the image side, and a 3b lens having a positive refractive power and in which the surface thereof toward the object side has a radius of curvature with a smaller absolute value than the surface thereof toward the image side; and the fourth lens group comprises, consecutively in order from the most object side thereof, a 4a lens of a positive meniscus shape, a stop, and a 4b lens having a positive refractive power and in which the surface thereof toward the object side has a radius of curvature with a smaller absolute value than the surface thereof toward the image side. |
