Optical system and image pickup apparatus having the same

An optical system consisting of, in order from an object side to an image side, a front unit, an aperture stop, and a rear unit that has positive refractive power as a whole,

• wherein the rear unit includes a final lens that has positive refractive power disposed closest to an image plane in the rear unit, a first negative lens disposed to an object side in the final lens and a cemented lens disposed closest to the object side in the rear unit, wherein the cemented lens includes a second negative lens and a positive lens, and
• wherein the following inequalities are satisfied:
• 0.5
• <
• TTL
• /
• Φ
• ⁢
• i
• <
• 1.4
• ⁢
• 1.713
• ≦
• PNdave
• <
• 1.792
• ⁢
• 2.
• <
• Φ
• ⁢
• p
• /
• sk
• <
• 4.
• ⁢
• 0.1
• <
• fb
• /
• ❘
• "\[LeftBracketingBar]"
• fa
• ❘
• "\[RightBracketingBar]"
• ≦
• 0.607
• 1.6
• <
• Ndbp
• <
• 2.
• ⁢
• 0.
• <
• Ndbp
• -
• Ndbn
• <
• 0.4
• where TTL is a distance on an optical axis from a lens surface on the object side of a lens disposed closest to an object in the optical system to the image plane, Φi is a diameter of an image circle, PNdave is an average value of refractive indices for d-line of all positive lenses included in the optical system, Φp is an effective diameter of a lens surface on the image side of the final lens, sk is an air conversion length of a distance on the optical axis from the lens surface on the image side of the final lens to the image plane, fa is a focal length of the front unit, fb is a focal length of the rear unit, Ndbp is a refractive index of the positive lens for the d-line, and Ndbn is a refractive index of the negative lens for the d-line.

An image pickup apparatus comprising:

• an optical system;
• and
• an image sensor configured to receive an image formed by the optical system,
• wherein the optical system consists of, in order from an object side to an image side, a front unit, an aperture stop, and a rear unit that has positive refractive power as a whole,
• wherein the rear unit includes a final lens that has positive refractive power disposed closest to an image plane in the rear unit, a first negative lens disposed to the object side in the final lens and a cemented lens disposed closest to the object side in the rear unit, wherein the cemented lens includes a second negative lens and a positive lens, and
• wherein the following inequalities are satisfied:
• 0.5
• <
• TTL
• /
• Φ
• ⁢
• i
• <
• 1.4
• ⁢
• 1.713
• ≦
• PNdave
• <
• 1.792
• ⁢
• 2.
• <
• Φ
• ⁢
• p
• /
• sk
• <
• 4.
• ⁢
• 0.1
• <
• fb
• /
• ❘
• "\[LeftBracketingBar]"
• fa
• ❘
• "\[RightBracketingBar]"
• ≦
• 0.607
• ⁢
• 1.6
• <
• Ndbp
• <
• 2.
• ⁢
• 0.
• <
• Ndbp
• -
• Ndbn
• <
• 0.4
• where TTL is a distance on an optical axis from a lens surface on an object side of a lens disposed closest to an object in the optical system to the image plane, Φi is a diameter of an image circle, PNdave is an average value of refractive indices for d-line of all positive lenses included in the optical system, Φp is an effective diameter of a lens surface on the image side of the final lens, sk is an air conversion length of a distance on the optical axis from the lens surface on the image side of the final lens to the image plane, fa is a focal length of the front unit, fb is a focal length of the rear unit, Ndbp is a refractive index of the positive lens for the d-line, and Ndbn is a refractive index of the negative lens for the d-line.