Inner focus lens system and image pickup apparatus using the same
AssigneeOlympus Imaging Corp.
InventorMasaru Morooka
Life of this patent
Estimating the term…
Abstract
An inner focus lens system comprises, in order from an object side to an image side, a first lens unit, an aperture stop, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power. The first lens unit has at least one negative lens and at least one positive lens, the second lens unit has at least one negative lens and at least one positive lens, the third lens unit has at least one negative lens, and the fourth lens unit has at least one positive lens. When focusing on an object at a short distance from an object at infinity, the third lens unit moves to lengthen a distance to the second lens unit and to shorten a distance to the fourth lens unit.
Claims40
An inner focus lens system comprising, in order from an object side to an image side,
- a first lens unit,
- an aperture stop,
- a second lens unit having a positive refractive power,
- a third lens unit having a negative refractive power, and
- a fourth lens unit having a positive refractive power,
- wherein a total number of lens units in the inner focus lens system is four, which is the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit,
- wherein the first lens unit has at least two negative lenses and at least one positive lens,
- the second lens unit has at least one negative lens and at least one positive lens,
- the third lens unit has at least one negative lens,
- the fourth lens unit has at least one positive lens,
- at a time of focusing on an object at a short distance from an object at infinity, the third lens unit moves to the image side so as to lengthen a distance to the second lens unit and to shorten a distance to the fourth lens unit, and
- the following conditional expression (1) is satisfied:
- −6<f3/f<−1 (1)
- where f3 is a focal length of the third lens unit, and
- f is a focal length of the inner focus lens system at the time of focusing on the object at infinity.
An inner focus lens system comprising, in order from an object side to an image side,
- a first lens unit,
- an aperture stop,
- a second lens unit having a positive refractive power,
- a third lens unit having a negative refractive power, and
- a fourth lens unit having a positive refractive power,
- wherein a total number of lens units in the inner focus lens system is four, which is the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit,
- wherein the first lens unit has at least one negative lens and at least one positive lens,
- the second lens unit has at least one negative lens and at least one positive lens,
- the third lens unit has at least one negative lens,
- the fourth lens unit has at least one positive lens,
- at a time of focusing on an object at a short distance from an object at infinity, the third lens unit moves to the image side so as to lengthen a distance to the second lens unit and to shorten a distance to the fourth lens unit,
- an F number of the inner focus lens system is 2 or less,
- a half angle of view of a light beam incident at a maximum image height position through a center of the aperture stop exceeds 30°, and
- the following conditional expression (1) is satisfied:
- −6<f3/f<−1 (1)
- where f3 is a focal length of the third lens unit, and
- f is a focal length of the inner focus lens system at the time of focusing on the object at infinity.
An inner focus lens system comprising, in order from an object side to an image side,
- a first lens unit,
- an aperture stop,
- a second lens unit having a positive refractive power,
- a third lens unit having a negative refractive power, and
- a fourth lens unit having a positive refractive power,
- wherein a total number of lens units in the inner focus lens system is four, which is the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit,
- wherein the first lens unit has at least one negative lens and at least one positive lens,
- the second lens unit has at least one negative lens and at least one positive lens,
- the third lens unit has at least one negative lens,
- the fourth lens unit has at least one positive lens,
- at a time of focusing on an object at a short distance from an object at infinity, the third lens unit moves to the image side so as to lengthen a distance to the second lens unit and to shorten a distance to the fourth lens unit,
- an exit surface of the first lens unit and an incidence surface of the second lens unit are concave toward an aperture stop side, and
- the following conditional expression (1) is satisfied:
- −6<f3/f<−1 (1)
- where f3 is a focal length of the third lens unit, and
- f is a focal length of the inner focus lens system at the time of focusing on the object at infinity.
Dependencies are inferred from the claim text.