Variable magnification optical system and imaging apparatus

A variable magnification optical system comprising:

• as groups having powers, only five groups consisting of, in order from an object side to an image side along an optical path, a first group that has a positive power, a second group that has a positive power, a third group that has a negative power, a fourth group that has a positive power, and a fifth group that has a positive power,
• wherein the first group is an optical element that has a power positioned closest to the object side on the optical path, and includes a first mirror that has a concave reflective surface facing toward the object side and a second mirror that reflects light, which is directed from the first mirror toward the object side, toward the image side and that has a convex reflective surface facing toward the image side,
• an intermediate image is formed in the optical path between the first group and the second group,
• the second group, the third group, and the fourth group are refractive optical systems,
• a stop is disposed between the third group and the fourth group,
• during changing magnification from a wide angle end to a telephoto end, the first mirror, the second mirror, the second group, the stop, and the fifth group remain stationary with respect to an image plane, the third group moves to the image side, and the fourth group moves to the object side, and
• assuming that
• an average of partial dispersion ratios of all positive lenses in the second group between a g line and an F line is θgF2P, and
• an average of partial dispersion ratios of all negative lenses in the second group between the g line and the F line is θgF2N,
• Conditional Expression (8) is satisfied, which is represented by
• −0.15<θgF2P−θgF2N<−0.005 (8).

A variable magnification optical system comprising:

• as groups having powers, only five groups consisting of, in order from an object side to an image side along an optical path, a first group that has a positive power, a second group that has a positive power, a third group that has a negative power, a fourth group that has a positive power, and a fifth group that has a positive power,
• wherein the first group is an optical element that has a power positioned closest to the object side on the optical path, and includes a first mirror that has a concave reflective surface facing toward the object side and a second mirror that reflects light, which is directed from the first mirror toward the object side, toward the image side and that has a convex reflective surface facing toward the image side,
• an intermediate image is formed in the optical path between the first group and the second group,
• the second group, the third group, and the fourth group are refractive optical systems,
• a stop is disposed between the third group and the fourth group,
• during changing magnification from a wide angle end to a telephoto end, the first mirror, the second mirror, the second group, the stop, and the fifth group remain stationary with respect to an image plane, the third group moves to the image side, and the fourth group moves to the object side,
• the first group remains stationary with respect to the image plane during changing magnification, and
• assuming that
• a focal length of the variable magnification optical system at the telephoto end is fT, and
• a focal length of the first group is f1,
• Conditional Expression (1-1) is satisfied, which is represented by
• 1<|fT/f1|<2.5 (1-1).