Image Forming Lens System and Image Pickup Apparatus Using the Same

An image forming 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 image forming lens system does not include any other lens unit on the optical axis, and
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, and a second lens unit having a negative refractive power, and
• each of the first lens unit and the second lens unit includes a positive lens and a negative lens, and
• the second lens unit is a focusing lens unit, and
• the focusing lens unit moves toward an image side along the optical axis at the time of focusing operation from an object at infinity to an object at a close distance, and
• the rear lens unit includes a positive lens and a negative lens, and
• the second lens unit is the only lens unit that moves, in the front lens unit, and
• the following conditional expressions (2) and (3) are satisfied:
• 0≦|f/rG2b|<7.0 (2)
• 0.27<|ffo|/f<0.6 (3)
• where,
• f denotes a focal length of the image forming lens system at the time of focusing at an object at infinity,
• rG2b denotes a paraxial radius of curvature of a lens surface on the object side of the second lens unit, immediately before the object, and
• ffo denotes a focal length of the second lens unit.

An image forming 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 image forming lens system does not include any other lens unit on the optical axis, and
• the front lens unit includes in order from the object side to the image side, a first lens unit having a positive refractive power, and a second lens unit having a negative refractive power, and
• each of the first lens unit and the second lens unit includes a positive lens and a negative lens, and
• the second lens unit is a focusing lens unit, and
• the focusing lens unit moves toward an image side along the optical axis at the time of focusing operation from an object at infinity to an object at a close distance, and
• the rear lens unit includes a positive lens and a negative lens, and
• the second lens unit is the only lens unit that moves, in the front lens unit, and
• the focusing lens unit includes two lenses, and
• the following conditional expressions (2) and (3′) are satisfied:
• 0≦|f/rG2b|<7.0 (2)
• 0.12<|ffo|/f<0.4 (3′)
• where,
• f denotes a focal length of the image forming lens system at the time of focusing at an object at infinity,
• rG2b denotes a paraxial radius of curvature of a lens surface on the object side of the second lens unit, immediately before the object, and
• ffo denotes a focal length of the second lens unit.