Variable magnification optical system, and image pickup apparatus and image pickup optical system using the same

A variable magnification optical system in which, a magnification ratio varies from a low magnification end to a high magnification end, comprising:

• a first lens unit having a positive refractive power, which is disposed nearest to an object;
• and
• a second lens unit having a negative refractive power, which is disposed on an image side of the first lens unit;
• wherein
• a stop which is disposed on the object side of the second lens unit is included;
• and
• at a time of varying magnification, the second lens unit moves, and a distance between the first lens unit and the second lens unit changes, and
• a third lens unit is disposed on an image side of the second lens unit, and
• the following conditional expression (8) is satisfied:
• 0.15≦ΔG2max/DHIGi≦2 (8),
• where,
• ΔG2max denotes a maximum amount of movement from among amounts of movement of the second lens unit on the optical axis, and
• DHIGi denotes a distance on the optical axis from a lens surface nearest to the object in the third lens unit up to an image plane, at the high magnification end.

A variable magnification optical system in which, a magnification ratio varies from a low magnification end to a high magnification end, comprising:

• a first lens unit having a positive refractive power, which is disposed nearest to an object;
• and
• a second lens unit which is disposed on an image side of the first lens unit, wherein
• a conjugate length of the variable magnification optical system changes at the time of varying magnification, and
• a lens unit which moves at the time of varying magnification is included, and
• the following conditional expression (12) is satisfied:
• 0.01≦|Δiomax/Δmax|≦5 (12),
• where,
• Δiomax denotes a maximum amount of change from among amounts of change in the conjugate length, and
• Δmax denotes a maximum amount of movement from among amounts of movement of the lens unit which moves.

An image pickup apparatus comprising:

• an image pickup element;
• and
• a variable magnification optical system, wherein
• an optical image is formed on the image pickup element by the variable magnification optical system, and
• the variable magnification optical system is an optical system in which, a magnification ratio varies from a low magnification end to a high magnification end, and includes
• at least a first lens unit having a positive refractive power, which is disposed nearest to an object, and
• a second lens unit which is disposed on an image side of the first lens unit, and
• at the time of varying magnification, a distance between the first lens unit and the second lens unit is variable, and
• the following conditional expressions (14) and (15) are satisfied:
• 3000≦2×Y/p (14),
• and
• 0.08≦NAH (15),
• where,
• Y denotes a maximum image height in the overall variable magnification optical system,
• p denotes a pixel pitch of the image pickup element, and
• NAH denotes a numerical aperture on the object side of the variable magnification optical system at the high magnification end.