Optical system and optical apparatus having the same
An optical system includes, in order from an object side to an image side, a first lens unit of a positive refractive power, an aperture diaphragm, and a second lens unit of a positive refractive power. The first lens unit includes, in order from the object side to the image side, a cemented lens Lp 1 made by joining a first lens of a positive refractive power and a second lens of a negative refractive power with each other, and a third lens of a positive refractive power which has a meniscus shape. The predetermined conditions are satisfied.
1. An optical system comprising, in order from an object side to an image side, a first lens unit of a positive refractive power, an aperture diaphragm, and a second lens unit of a positive refractive power,
wherein the first lens unit includes, in order from the object side to the image side, a cemented lens Lp 1 made by joining a first lens of a positive refractive power and a second lens of a negative refractive power with each other, and a third lens of a positive refractive power which has a meniscus shape,
wherein the following conditional expressions are satisfied:
0.030<( n 11− n 12)
0.20<( νd 11 /νd 12)<1.30
−10.0 <fp 1 /f<− 0.2
where n 11 and νd 11 are a refractive index and an Abbe number of a material of the first lens, n 12 and νd 12 are a refractive index and an Abbe number of a material of the second lens, fp 1 is a focal length of the cemented lens Lp 1 , and f is a focal length of an entire optical system.
2. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.8<BF/ f< 1.5
where BF is a back focus in a focus upon an infinitely distant object of the optical system.
3. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.8 <f 1 a/f< 25.0
where f 1 a is a focal length of the first lens unit.
4. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.50 <Ltot /BF<0.72
where BF is a back focus in a focus upon an infinitely distant object of the optical system, and Ltot is an effective lens length of the optical system.
5. The optical system according to claim 1 , wherein the second lens unit includes, in order from the object side to the image side, a cemented lens Lp 2 made by joining a fourth lens of a negative refractive power and a fifth lens of a positive refractive power with each other, and a sixth lens of a positive refractive power which has a meniscus shape.
6. The optical system according to claim 5 , wherein the following expressions are satisfied:
−0.10<( n 22− n 21)<0.15
1.20<( νd 22 /νd 21)<2.50
where n 21 and νd 21 are a refractive index and an Abbe number of a material of the fourth lens, and n 22 and νd 22 are a refractive index and an Abbe number of a material of the fifth lens.
7. The optical system according to claim 5 , wherein the following expressions are satisfied:
1.00 <f 1 b/f< 1.40
−5.00 <fp 2 /f<− 0.20
where f 1 b is a focal length of the second lens unit, and fp 2 is a focal length of the cemented lens unit Lp 2 .
8. An optical system according to claim 1 , forming an image on a photoelectric conversion element.
9. An optical apparatus comprising:
an optical system; and
a photoelectric conversion element configured to receive light of an image formed by the optical system,
wherein the optical system includes, in order from an object side to an image side, a first lens unit of a positive refractive power, an aperture diaphragm, and a second lens unit of a positive refractive power,
wherein the first lens unit includes, in order from the object side to the image side, a cemented lens Lp 1 made by joining a first lens of a positive refractive power and a second lens of a negative refractive power with each other, and a third lens of a positive refractive power which has a meniscus shape,
wherein the following conditional expressions are satisfied:
0. 030<( n 11− n 12)
0. 20<(νd11/νd 12)<1.30
−10.0<fp1/f<−0.2
where n 11 and νd 11 are a refractive index and an Abbe number of a material of the first lens, n 12 and νd 12 are a refractive index and an Abbe number of a material of the second lens, fp 1 is a focal length of the cemented lens Lp 1 , and f is a focal length of an entire optical system.