| 摘要 |
An inner focus lens system comprises, in order from an object side to an image side, a first lens unit, an aperture stop, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power, wherein the first lens unit has at least one negative lens and at least one positive lens, the second lens unit has at least one negative lens and at least one positive lens, the third lens unit has at least one negative lens, the fourth lens unit has at least one positive lens, at the time of focusing on an object at a short distance from an object at infinity, the third lens unit moves to an image side so as to lengthen a distance to the second lens unit and to shorten a distance to the fourth lens unit, and the following conditional expression (1) is satisfied:;−6<f3/f<−1 (1). |
| 主权项 |
1. An inner focus lens system comprising, in order from an object side to an image side,
a first lens unit, an aperture stop, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power, wherein a total number of lens units in the inner focus lens system is four, which is the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit, wherein the first lens unit has at least one negative lens and at least one positive lens, the second lens unit has at least one negative lens and at least one positive lens, the third lens unit has at least one negative lens, the fourth lens unit has at least one positive lens, at a time of focusing on an object at a short distance from an object at infinity, the third lens unit moves to the image side so as to lengthen a distance to the second lens unit and to shorten a distance to the fourth lens unit, wherein an F number of the inner focus lens system is 2 or less, and wherein an exit surface of the first lens unit and an incidence surface of the second lens unit are concave toward an aperture stop aperture stop side. |
