Image forming lens system and image pickup apparatus including the same

An image forming lens system comprising, in order from an object side to an 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,
• wherein:
• the first lens unit includes a front-side lens unit having a positive refractive power and a rear-side lens unit with an air space interposed therebetween in order from the object side,
• the second lens unit moves by changing respective air spaces on the object side and the image side at a time of focusing,
• the third lens unit includes a positive lens element,
• each lens element in the front-side lens unit is a lens element that satisfies following Conditional Expression (a),
• the rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit,
• the first rear-side lens unit includes a negative lens element and a positive lens element,
• the second rear-side lens unit includes a positive lens element,
• the front-side lens unit includes a diffractive lens component having a diffractive lens surface,
• the diffractive lens component has a positive refractive power, and
• following Conditional Expression (2) is satisfied:
• −0.7≤f/fLens (a)
• 0.1≤ΔGFFGR1/f≤0.5 (2)
• where
• f is a longest focal length of the entire image forming lens system at a time of focusing to a furthest distance,
• fLens is a focal length of each lens element in the front-side lens unit,
• ΔGFFGR1 is an on-axis distance from an object-side surface in the front-side lens unit to an object-side surface in the first rear-side lens unit,
• a lens component means a lens in which only two surfaces, namely, an object-side surface and an image-side surface are effective surfaces in contact with air, and
• a lens element is a lens having two effective transmission surfaces, namely, an object-side surface and an image-side surface and having no other effective transmission surface between the two effective transmission surfaces.

An image forming lens system comprising, in order from an object side to an 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,
• wherein:
• the first lens unit includes a front-side lens unit having a positive refractive power and a rear-side lens unit with an air space interposed therebetween in order from the object side,
• the second lens unit moves by changing respective air spaces on the object side and the image side at a time of focusing,
• the third lens unit includes a positive lens element,
• the rear-side lens unit includes a first rear-side lens unit and a second rear-side lens unit,
• the first rear-side lens unit includes a negative lens element and a positive lens element,
• the second rear-side lens unit includes a positive lens element,
• the front-side lens unit includes a positive lens component disposed closest to the object side and a diffractive lens component having a diffractive lens surface,
• the diffractive lens component is disposed closest to the image side in the front-side lens unit and includes a diffractive lens element closest to the image side, and
• following Conditional Expression (1-1) is satisfied:
• 0.015≤ΔGFGR1Do/f≤0.3 (1-1)
• where
• f is a longest focal length of the entire image forming lens system at a time of focusing to a furthest distance,
• ΔGFGR1Do is an on-axis air space from an image-side surface of the diffractive lens element to an object-side surface in the first rear-side lens unit,
• a lens component means a lens in which only two surfaces, namely, an object-side surface and an image-side surface are effective surfaces in contact with air, and
• a lens element is a lens having two effective transmission surfaces, namely, an object-side surface and an image-side surface and having no other effective transmission surface between the two effective transmission surfaces.

An image forming lens system comprising, in order from an object side to an 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,
• wherein:
• the first lens unit includes a front-side lens unit having a positive refractive power and a rear-side lens unit with an air space interposed therebetween in order from the object side,
• the second lens unit moves by changing respective air spaces on the object side and the image side at a time of focusing,
• the third lens unit includes a positive lens element,
• each lens element in the front-side lens unit is a lens element that satisfies following Conditional Expression (a),
• the front-side lens unit includes a positive lens component disposed closest to the object side and a diffractive lens component having a diffractive lens surface,
• the diffractive lens component is disposed closest to the image side in the front-side lens unit and includes a diffractive lens element closest to the image side, and
• following Conditional Expression (1-2) is satisfied:
• −0.7≤f/fLens (a)
• 0.02≤ΔGFGRDo/f≤0.3 (1-2)
• where
• f is a longest focal length of the entire image forming lens system at a time of focusing to a furthest distance,
• fLens is a focal length of each lens element in the front-side lens unit,
• ΔGFGRDo is an on-axis air space from an image-side surface of the diffractive lens element to an object-side surface in the rear-side lens unit,
• a lens component means a lens in which only two surfaces, namely, an object-side surface and an image-side surface are effective surfaces in contact with air, and
• a lens element is a lens having two effective transmission surfaces, namely, an object-side surface and an image-side surface and having no other effective transmission surface between the two effective transmission surfaces.

An image forming lens system comprising, in order from an object side to an 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,
• wherein:
• the first lens unit includes a front-side lens unit having a positive refractive power and a rear-side lens unit with an air space interposed therebetween in order from the object side,
• the second lens unit moves by changing respective air spaces on the object side and the image side at a time of focusing,
• the third lens unit includes a positive lens element,
• the front-side lens unit includes a positive lens component disposed closest to the object side and a diffractive lens component having a diffractive lens surface,
• the diffractive lens component is disposed closest to the image side in the front-side lens unit,
• the rear-side lens unit includes a positive lens and a negative lens,
• an air space between the diffractive lens component and the rear-side lens unit is largest of air spaces in the first lens unit,
• the image forming lens system further comprises an aperture stop disposed closer to the object side than the second lens unit to limit on-axis light flux, and
• following Conditional Expression (1-3) is satisfied:
• 0.01≤ΔGFDoGRmax/f≤0.2 (1-3)
• where
• f is a longest focal length of the entire image forming lens system at a time of focusing to a furthest distance,
• ΔGFDoGRmax is a largest on-axis air space of on-axis air spaces from an image-side surface of the diffractive lens component to an object-side surface in the rear-side lens unit,
• a lens component means a lens in which only two surfaces, namely, an object-side surface and an image-side surface are effective surfaces in contact with air, and
• a lens element is a lens having two effective transmission surfaces, namely, an object-side surface and an image-side surface and having no other effective transmission surface between the two effective transmission surfaces.