| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact and thin imaging optical system that offers a desired back focus and superior imaging performance, and to provide an electronic image capturing device having the same.SOLUTION: An imaging optical system comprises a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power in an order from the object side, and is configured such that a distance between adjacent lens groups changes while zooming. The first lens group comprises either a negative lens and a positive lens, or a first negative lens, a second negative lens, and a positive lens. The second group comprises a first lens component and a second lens component, the first lens component comprises either a positive single lens or a cemented lens comprising a positive lens and a negative lens cemented together in a described order, and the second lens component has a cemented lens. The third lens group has a lens closest to an object side with a curvature of an image-side surface greater than that of an object-side surface, and consists of one or two lenses as a whole. The fourth lens group comprises a positive lens component.SELECTED DRAWING: Figure 1 |
