| 摘要 |
An image forming optical system includes in order from an object side to an image surface, a first lens group having a positive refracting power, a second lens group having a negative refracting power, and a third lens group having a positive refracting power. At the time of zooming from a wide angle end to a telephoto end, a distance between the first lens group and the second lens group increases, and a distance between the second lens group and the third lens group decreases. The first lens group has a cemented lens which includes a first lens element E1, a second lens element E2, and a third lens element E3. In the cemented lens, the first lens element E1 is cemented to a surface on one side of the second lens element E2, and the third lens element E3 is cemented to another surface of the second lens element E2. The first lens element E1 is a negative lens, and the second lens element E2 is a positive lens. The image forming optical system satisfies predetermined conditional expressions. |
