Image forming optical system and image pickup apparatus using the same

An image forming optical system comprising, in order from an object side:

• a first lens unit having a positive refractive power;
• a second lens unit having a negative refractive power;
• a third lens unit having a positive refractive power;
• a fourth lens unit having a negative refractive power;
• and
• a rear-side lens unit which is disposed nearest to an image,
• wherein:
• at a time of focusing or at a time of zooming, a distance between the first lens unit and the second lens unit widens,
• the rear-side lens unit includes a positive lens and a negative lens,
• the first lens unit and the third lens unit, at all times, do not move in an optical axis direction,
• at a time of focusing from an object at a long distance to an object at a close distance, the fourth lens unit moves toward an image side,
• the third lens unit includes a positive lens and a negative lens,
• a motion blur correction lens unit is disposed in the third lens unit,
• a motion blur is corrected by the motion blur correction lens unit being moved in a direction perpendicular to an optical axis, and
• the following conditional expressions (2) and (3) are satisfied:
• 70.0≤vdFFp (2),
• 3.7≤LTL/fMF≤8.5 (3),
• where,
• fMF denotes a focal length of the third lens unit,
• LTL denotes a distance from a lens surface nearest to object up to an image plane, and
• vdFFp denotes Abbe's number which is the maximum among Abbe's numbers for positive lenses in the first lens unit.

An image forming optical system comprising, in order from an object side:

• a first lens unit having a positive refractive power;
• a second lens unit having a negative refractive power;
• a third lens unit having a positive refractive power;
• a fourth lens unit having a negative refractive power;
• and
• a rear-side lens unit which is disposed nearest to an image,
• wherein:
• at a time of focusing or at a time of zooming, a distance between the first lens unit and the second lens unit widens,
• the rear-side lens unit includes a positive lens and a negative lens,
• the first lens unit and the third lens unit, at all times, do not move in an optical axis direction,
• at a time of focusing from an object at a long distance to an object at a close distance, the fourth lens unit moves toward an image side,
• the third lens unit includes a positive lens and a negative lens,
• a motion blur correction lens unit is disposed in the third lens unit,
• a motion blur is corrected by the motion blur correction lens unit being moved in a direction perpendicular to an optical axis,
• the motion blur correction lens unit includes a positive lens and a negative lens, and
• the following conditional expressions (4) and (5) are satisfied:
• 1.5≤|LTL/fFB|≤9.5 (4),
• −2.5≤fMB/fR≤−0.15 (5),
• where,
• fFB denotes a focal length of the second lens unit,
• LTL denotes a distance from a lens surface nearest to object up to an image plane,
• fMB denotes a focal length of the fourth lens unit, and
• fR denotes a focal length of the rear-side lens unit.

An image forming optical system comprising, in order from an object side:

• a first lens unit having a positive refractive power;
• a second lens unit having a negative refractive power;
• a third lens unit having a positive refractive power;
• a fourth lens unit having a negative refractive power;
• and
• a rear-side lens unit which is disposed nearest to an image,
• wherein:
• at a time of focusing or at a time of zooming, a distance between the first lens unit and the second lens unit widens,
• the rear-side lens unit includes a positive lens and a negative lens,
• the first lens unit and the third lens unit, at all times, do not move in an optical axis direction,
• at the time focusing from an object at a long distance to an object at a close distance, the fourth lens unit moves toward an image side,
• the third lens unit includes a positive lens and a negative lens,
• a motion blur correction lens unit is disposed in the third lens unit,
• a motion blur is corrected by the motion blur correction lens unit being moved in a direction perpendicular to an optical axis,
• the third lens unit includes in order from the object side, an object-side sub unit and an image-side sub unit,
• the object-side sub unit includes a positive lens and a negative lens,
• the image-side sub unit includes the motion blur correction lens unit, and
• the motion blur correction lens unit includes a positive lens and a negative lens.