Imaging lens and imaging apparatus
View Patent ↗An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. An object-side surface of the second lens is concave, and an object-side surface of the third lens is concave. A predetermined conditional formula about a combined focal length of the fourth lens and the fifth lens is satisfied.
1. An imaging lens substantially consisting of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side,
wherein an image-side surface of the second lens has a shape having negative refractive power at a center and weaker negative refractive power at an effective diameter edge, compared with the center, and
wherein an image-side surface of the third lens has a shape having positive refractive power at a center and weaker positive refractive power at an effective diameter edge, compared with the center, and
wherein an Abbe number of a material of the third lens for d-line is less than or equal to 30 and a refractive index of the material is lower than or equal to 1.75, and
wherein the following conditional formula (22) is satisfied:
−30 <f 23 /f <−3 (22), where
f 23 : a combined focal length of the second lens and the third lens, and
f: a focal length of an entire system.
2. An imaging lens substantially consisting of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side,
wherein an object-side surface of the third lens has a shape having negative refractive power at a center and stronger negative refractive power at an effective diameter edge, compared with the center, and
wherein an Abbe number of a material of the third lens for d-line is less than or equal to 30 and a refractive index of the material is lower than or equal to 1.75, and
wherein the following conditional formula (22) is satisfied:
−30 <f 23 /f <−3 (22), where
f 23 : a combined focal length of the second lens and the third lens, and
f: a focal length of an entire system.
3. An imaging lens substantially consisting of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side,
wherein an object-side surface of the second lens is concave, and
wherein an object-side surface of the third lens is concave, and
wherein the following conditional formula (23-4) is satisfied:
7.8≦ f 45/ f< 25 (23-4), where
f 45 : a combined focal length of the fourth lens and the fifth lens, and
f: a focal length of an entire system.
4. An imaging apparatus comprising:
the imaging lens, as defined in claim 3 , mounted thereon.
5. The imaging lens, as defined in claim 3 , wherein the following conditional formula (19) is satisfied:
1<( D 4 +D 5)/ f <6 (19), where
D 4 : an air space between the second lens and the third lens on an optical axis,
D 5 : a center thickness of the third lens, and
f: a focal length of an entire system.
6. The imaging lens, as defined in claim 5 , wherein the following conditional formula (19-1) is satisfied:
1.4<( D 4 +D 5)/ f <5.5 (19-1), where
D 4 : an air space between the second lens and the third lens on an optical axis,
D 5 : a center thickness of the third lens, and
f: a focal length of an entire system.
7. The imaging lens, as defined in claim 5 , wherein the following conditional formula (19-3) is satisfied:
1.9<( D 4 +D 5)/ f <4.4 (19-3), where
D 4 : an air space between the second lens and the third lens on an optical axis,
D 5 : a center thickness of the third lens, and
f: a focal length of an entire system.
8. The imaging lens, as defined in claim 3 , wherein the following conditional formula (20) is satisfied:
−1 <f/R 5<1 (20), where
f: a focal length of an entire system, and
R 5 : a curvature radius of an object-side surface of the third lens.
9. The imaging lens, as defined in claim 8 , wherein the following conditional formula (20-2) is satisfied:
−0.5 <f/R 5<0.5 (20-2), where
f: a focal length of an entire system, and
R 5 : a curvature radius of an object-side surface of the third lens.
10. The imaging lens, as defined in claim 8 , wherein the following conditional formula (20-3) is satisfied:
−0.2 <f/R 5<0.2 (20-3), where
f: a focal length of an entire system, and
R 5 : a curvature radius of an object-side surface of the third lens.
11. The imaging lens, as defined in claim 3 , wherein the following conditional formula (21) is satisfied:
−3 <f/R 3<3 (21), where
f: a focal length of an entire system, and
R 3 : a curvature radius of an object-side surface of the second lens.
12. The imaging lens, as defined in claim 11 , wherein the following conditional formula (21-2) is satisfied:
−2.0 <f/R 3<1.5 (21-2), where
f: a focal length of an entire system, and
R 3 : a curvature radius of an object-side surface of the second lens.
13. The imaging lens, as defined in claim 11 , wherein the following conditional formula (21-3) is satisfied:
−1.5 <f/R 3<1.0 (21-3), where
f: a focal length of an entire system, and
R 3 : a curvature radius of an object-side surface of the second lens.
14. The imaging lens, as defined in claim 3 , wherein the following conditional formula (22-1) is satisfied:
−25 <f 23 /f <−4 (22-1), where
f 23 : a combined focal length of the second lens and the third lens, and
f: a focal length of an entire system.
15. The imaging lens, as defined in claim 3 , wherein the following conditional formula (22-2) is satisfied:
−20 <f 23 /f <−5 (22-2), where
f 23 : a combined focal length of the second lens and the third lens, and
f: a focal length of an entire system.
16. The imaging lens, as defined in claim 3 , where a stop is arranged between the third lens and the fourth lens.