Abstract: An optical system includes, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having positive refractive power, a third lens unit, a fourth lens unit having positive refractive power, and a fifth lens unit having negative refractive power. During focusing from infinity to a close distance, a distance between adjacent lens units changes and the second lens unit and the fourth lens unit move toward the object side. At least one of the second lens unit and the fourth lens unit includes two or more lenses. The first lens unit includes two or more negative lenses. A predetermined inequality is satisfied.

Abstract: A control apparatus for processing image data acquired through an imaging optical system and an image sensor acquires first information corresponding to a magnification that is different according to an image height and second information corresponding to a magnification that is constant regardless of the image height, the first information and the second information being associated with the imaging optical system, and processes the image data using the first information and the second information to reduce image point movement at an out-of-focus position of the imaging optical system.

Abstract: An imaging optical system, which images an image on one conjugate surface of an enlargement side conjugate surface and a reduction side conjugate surface onto the other conjugate surface, includes, in order from the reduction side conjugate surface to the enlargement side conjugate surface, a refractive optical system and a reflective optical system. The refractive optical system forms an intermediate real image at an intermediate imaging position inside the refractive optical system. The reflective optical system includes a convex mirror disposed closest to the enlargement side conjugate surface. The predetermined conditional expression is satisfied.

Abstract: An imaging optical system, which images an image on one conjugate surface of an enlargement side conjugate surface and a reduction side conjugate surface onto the other conjugate surface, includes, in order from the reduction side conjugate surface to the enlargement side conjugate surface, a refractive optical system and a reflective optical system. The refractive optical system forms an intermediate real image at an intermediate imaging position inside the refractive optical system. The reflective optical system includes a convex mirror disposed closest to the enlargement side conjugate surface. The predetermined conditional expression is satisfied.

Abstract: A zoom optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a first optical group, and a second optical group having a zoom function. The second optical group includes, in order from the enlargement conjugate side to the reduction conjugate side, a lens unit B21 with positive refractive power, a lens unit B22 with positive refractive power, and a lens unit B23 with positive refractive power. The lens units B21 and B22 move with a distance therebetween changed at the time of zooming. A predetermined relationship between a focal length fR of the second optical group in a wide-angle end and a focal length fB22 of the lens unit B22 is satisfied.

Abstract: A zoom optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a first optical group, and a second optical group having a zoom function. The second optical group includes, in order from the enlargement conjugate side to the reduction conjugate side, a lens unit B21 with positive refractive power, a lens unit B22 with positive refractive power, and a lens unit B23 with positive refractive power. The lens units B21 and B22 move with a distance therebetween changed at the time of zooming. A predetermined relationship between a focal length fR of the second optical group in a wide-angle end and a focal length fB22 of the lens unit B22 is satisfied.