Abstract: An image quality is improved although a medical stereomicroscope optical system and a medical observation apparatus are small and light. An objective optical system and a plurality of imaging optical systems are arranged in an order from an object side to an image side, and the imaging optical system has at least a single aspheric surface. Accordingly, a spherical aberration and a field curvature are improved, and the image quality is improved although the medical stereomicroscope optical system and a medical observation apparatus are small and light.

Abstract: An image quality is improved although a medical stereomicroscope optical system and a medical observation apparatus are small and light. An objective optical system and a plurality of imaging optical systems are arranged in an order from an object side to an image side, and the imaging optical system has at least a single aspheric surface. Accordingly, a spherical aberration and a field curvature are improved, and the image quality is improved although the medical stereomicroscope optical system and a medical observation apparatus are small and light.

Abstract: A zoom lens includes a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group which has negative refractive power and is configured with only a single lens, and a fifth lens group having positive refractive power, which are arranged in order from an object side to an image side. During zooming, at least the first lens group, the second lens group, the third lens group, and the fourth lens group are movable in an optical axis direction. Focusing from infinity to a close range is performed by the fourth lens group being moved in the optical axis direction. At least one of following conditional expressions (1) and (2) is satisfied. ?11.0<Fno—w×Y/{(1??4—w2)×?5—w2}<?7.0 and??(1) ?11.0<Fno—t×Y/{(1??4—t2)×?5—t2}<?7.

Abstract: There is provided an imaging apparatus including an image sensor that converts an optical image captured through a lens into an electrical signal, and a shutter that has blade members to be opened and closed at a time of photographing. Correction of shading that is generated by an operation of the shutter is performed on a basis of an elliptical shape, and the elliptical shape is inclined in a direction according to an operation direction of the blade members.

Abstract: A zoom lens includes a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group which has negative refractive power and is configured with only a single lens, and a fifth lens group having positive refractive power, which are arranged in order from an object side to an image side. During zooming, at least the first lens group, the second lens group, the third lens group, and the fourth lens group are movable in an optical axis direction. Focusing from infinity to a close range is performed by the fourth lens group being moved in the optical axis direction. At least one of following conditional expressions (1) and (2) is satisfied. ?11.0<Fno—w×Y/{(1??4—w2)×?5—w2}<?7.0 and??(1) ?11.0<Fno—t×Y/{(1??4—t2)×?5—t2}<?7.

Abstract: There is provided a zoom lens including, in order from an object side to an image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power. In zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group shortens, and a distance between the third lens group and the fourth lens group lengthens. The third lens group includes a single lens or a single cemented lens.

Abstract: There is provided a zoom lens including in order from an object side to an image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power. In zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group narrows, and a distance between the third lens group and the fourth lens group widens. The third lens group includes a single lens or a single cemented lens.

Abstract: There is provided an imaging apparatus including an image sensor that converts an optical image captured through a lens into an electrical signal, and a shutter that has blade members to be opened and closed at a time of photographing. Correction of shading that is generated by an operation of the shutter is performed on a basis of an elliptical shape, and the elliptical shape is inclined in a direction according to an operation direction of the blade members.

Abstract: There is provided a zoom lens including in order from an object side to an image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power. In zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group narrows, and a distance between the third lens group and the fourth lens group widens. The third lens group includes a single lens or a single cemented lens.

Abstract: There is provided a zoom lens including, in order from an object side to an image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power. In zooming from a wide-angle end to a telescopic end, the first lens group moves to the object side in a manner that a distance toward the second lens group shortens, and a distance between the third lens group and the fourth lens group lengthens. The third lens group includes a single lens or a single cemented lens.