Single focal length lens system and image pickup apparatus using the same

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the rear lens unit includes a focusing lens unit having a negative refractive power which moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and a lens unit having a positive refractive power, and
• only the focusing lens unit moves in the optical axial direction at the time of focusing.

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the focusing lens unit is the only lens unit which moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the rear lens unit has a lens unit having a positive refractive power which is disposed on the image side of the focusing lens unit, immediately after the focusing lens unit, and which includes a positive lens and a negative lens.

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the rear lens unit includes an image-motion correcting lens unit, and
• the image-motion correcting lens unit moves in a direction different from a direction of the optical axis to reduce an image motion due to shaking of the single focal length lens system.

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the focusing lens unit satisfies the following conditional expression (10):
• 0.9<|(MGfoback)2×{(MGfo)2−1}|<3.50 (10)
• where,
• MGfo denotes a lateral magnification of the focusing lens unit in an arbitrary focused state, and
• MGfoback denotes a lateral magnification of the overall optical system between the focusing lens unit and the image plane, in an arbitrary focused state.

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the single focal length lens system includes an image-motion correcting lens unit which satisfies the following conditional expression (11):
• 2.00<|MGISback×(MGIS×1)|<7.50 (11)
• where,
• MGIS denotes a lateral magnification of the image-motion correcting lens unit in an arbitrary focused state, and
• MGISback denotes a lateral magnification of an overall optical system between the image-motion correcting lens unit and the image plane, in an arbitrary focused state.

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the total number of lenses included in the focusing lens unit is not more than two.

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the focusing lens unit consists of two lenses namely, a positive lens and a negative lens.

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the focusing lens unit has a negative refractive power, and
• a lens unit which does not move in the optical axial direction at the time of focusing is a lens unit having a positive refractive power of which, a position is fixed all the time, and
• the rear lens unit includes a image-motion correcting lens unit and the lens unit having a positive refractive power of which, the position is fixed all the time, and
• the image-motion correcting lens unit is disposed on the image side of the lens unit having a positive refractive power, of which, the position is fixed all the time, and moves in a direction different from a direction of the optical axis to reduce an image motion due to shaking of the single focal length lens system, and
• the lens unit having a positive refractive power of which, the position is fixed all the time, is disposed on the image side of the image-motion correcting lens unit.

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the following conditional expression (15) is satisfied:
• 0.023≦Dsfo/DLTL≦0.110 (15)
• where,
• Dsfo denotes a distance on the optical axis from the aperture stop up to a lens surface nearest to an object of the focusing lens unit,
• DLTL denotes a distance on the optical axis from a lens surface nearest to the object of the single focal length lens system up to an image plane, and
• both Dsfo and DLTL are distances at the time of focusing at an object at infinity.

A single focal length lens system comprising in order from an object side to an image side along an optical axis:

• a front lens unit having a positive refractive power;
• and
• a rear lens unit, wherein
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, and
• both the first lens unit and the second lens unit include a positive lens and a negative lens, and
• the rear lens unit includes in order from the object side to the image side, a focusing lens unit and a first predetermined lens unit, and
• the focusing lens unit moves along the optical axis at the time of focusing from an object at infinity to an object at a close distance, and
• the first predetermined lens unit has a refractive power having a sign different from a sign of a refractive power of the focusing lens unit, and does not move in an optical axial direction at the time of focusing, and
• the front lens unit does not include a lens which moves in the optical axial direction, and
• the rear lens unit does not include a lens which moves in the optical axial direction except at the time of focusing, and
• the following conditional expression (16) is satisfied:
• 0.2≦Dsfo/φs≦0.8 (16)
• where,
• Dsfo denotes the distance on the optical axis from the aperture stop up to a lens surface nearest to an object of the focusing lens unit, and is a distance at the time of focusing at an object at infinity, and
• Φs denotes a maximum diameter of the aperture stop.