Variable magnification optical system and control method thereof

A control method of a variable magnification optical system, the method comprising:

• causing a variable magnification optical device to form a subject image on an imaging surface of an imaging device by changing a magnification of the subject image according to a variable magnification amount;
• causing a variable magnification amount setting device to set a variable magnification amount of the variable magnification optical device;
• causing a shift mechanism to relatively slides the variable magnification optical device with respect to the imaging surface;
• causing a rotation mechanism to relatively rotates the variable magnification optical device around the imaging surface with the optical axis of the variable magnification optical device or the central axis of the imaging surface as a center;
• causing a position adjustment amount memory to stores position adjustment amounts using the shift mechanism and the rotation mechanism which correspond to at least two kinds of variable magnification amounts;
• causing a position adjustment amount calculating unit to calculates a position adjustment amount using at least one of the shift mechanism or the rotation mechanism which corresponds to the variable magnification amount set by the variable magnification amount setting device by using the position adjustment amounts stored in the position adjustment amount memory;
• causing a position adjustment mechanism controller to causes at least one of the shift mechanism or the rotation mechanism to adjust the positional relationship between the variable magnification optical device and the imaging surface by using the position adjustment amount calculated by the position adjustment amount calculating unit;
• causing a magnifying optical system to magnifies the subject image formed on the imaging surface of the imaging device;
• causing a determination unit to determines whether or not at least a part of the imaging surface is not included in a range of the subject image magnified by the magnifying optical system in a case where the positional relationship between the variable magnification optical device and the imaging surface is adjusted by at least one of the shift mechanism or the rotation mechanism by using the position adjustment amount calculated by the position adjustment amount calculating unit;
• and
• causing a position adjustment amount correcting unit to corrects the position adjustment amount calculated by the position adjustment amount calculating unit to a position adjustment amount with which the circumscribed circle of the imaging surface is included in the range of the subject image magnified by the magnifying optical system in a case where adjustment using at least one of the shift mechanism or the rotation mechanism is performed according to the fact that the determination unit determines that the at least a part of the imaging surface is not included in the range of the subject image magnified by the magnifying optical system.