| 摘要 |
This zoom optical system is formed from, arranged in order from the object side, a first lens group having negative refractive power and other lens groups, and when magnification is varied, the spacing between each of the lens groups changes. The first lens group is disposed closest to the object side and has a first negative lens, which has a diffraction optical element on the image side lens surface and a positive lens disposed more to the image side than the first negative lens. Furthermore, the glass material used in the positive lens satisfies the following conditional equations. nu1p <= 35 Delta (thetag, F) >= 0.007 Here, nu1p is the Abbe's number the basis of which is the d line for the glass material used in the positive lens of the first lens group, and Delta (thetag, F) is the deviation in the partial variance ratio from a standard line for glass material used in the positive lens when a straight line joining glass type A and glass type B forms the standard line in a graph that has the Abbe's number of which the basis is the d line as the horizontal axis and the partial variance ratio (thetag, F) = (ng - nF)/(nF - nC) as the vertical axis. Moreover, the Abbe's number nud for the glass type A and glass type B and the partial variance ratio (thetag, F)) are the following values. Glass type A: nud = 60.49, (thetag, F) = 0.5436 Glass type B: nud = 36.26, (thetag, F) = 0.5828 |
