IMAGING LENS AND IMAGING APPARATUS

• US 20150131169A1
• Filed: 01/23/2015
• Published: 05/14/2015
• Est. Priority Date: 07/23/2012
• Status: Active Grant

• Current Assignee: Tianjin OFILM Opto Electronics Co., Ltd.
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: ASAMI, TARO
• Granted Patent: US 9,383,555 B2
• Time in Patent Office: Days
• US Class Current: 359/713
• CPC Class Codes: G02B 13/0045 having five or more lenses
• CPC Class Codes: G02B 13/04 Reversed telephoto objectives
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 9/62 having six components only

Abstract

An imaging lens consists essentially of six lenses in the following order from the object side: a negative first lens; a positive second lens; a negative third lens; a positive fourth lens; a positive fifth lens; and a negative sixth lens. An aperture stop is disposed more toward the object side than the image-side surface of the fourth lens. Conditional expression (4) is satisfied, where f is the focal length of the entire system, and f56 is the combined focal length of the fifth lens and the sixth lens:

f56/f<−6.4  (4).

Claims

1. An imaging lens consisting essentially of a first lens having a negative power, a second lens having a positive power, a third lens having a negative power, a fourth lens having a positive power, a fifth lens having a positive power, and a sixth lens having a negative power in this order from the object side, wherein

an aperture stop is disposed toward the object side than the image-side surface of the fourth lens,

the Abbe number of the material of the third lens with respect to the d-line is less than or equal to 30, and

the imaging lens satisfies conditional formula (4) below:

f56/f<

−

6.4 

 

(4),where

f;

the focal length of the entire system, and

f56;

the combined focal length of the fifth lens and the sixth lens.

2. The imaging lens of claim 1 that satisfies conditional formulas (5-1) and (6) below:

−

1.5<

f34/f56<

0.0 

 

(5-1)

0.0<

f34/f 

 

(6),where

f34;

the combined focal length of the third lens and the fourth lens, and

f56;

the combined focal length of the fifth lens and the sixth lens.

3. The imaging lens of claim 1, wherein materials of the third lens, the fourth lens, the fifth lens, and the sixth lens are plastics.

4. The imaging lens of claim 3 that satisfies conditional formula (7) below:

2.0<

f3456/f 

 

(7),where

f3456;

the combined focal length of the third lens, the fourth lens, the fifth lens, and the sixth lens.

5. The imaging lens of claim 1 that satisfies conditional formula (8) below:

0.9<

ν

d2/ν

d3 

 

(8),where

ν

d2;

the Abbe number of the material of the second lens with respect to the d-line, and

ν

d3;

the Abbe number of the material of the third lens with respect to the d-line.

6. The imaging lens of claim 1 that satisfies conditional formula (9) below:

−

2.5<

f3/f<

−

0.5 

 

(9),where

f;

the focal length of the entire system, and

f3;

the focal length of the third lens.

7. The imaging lens of claim 1, wherein the aperture stop is provided between the object-side surface of the second lens and the image-side surface of the fourth lens.

8. The imaging lens of claim 1 that satisfies conditional formula (10) below:

−

3.0<

f3/f4<

−

0.2 

 

(10),where

f3;

the focal length of the third lens, and

f4;

the focal length of the fourth lens.

9. The imaging lens of claim 1 that satisfies conditional formula (11) below:

0.2<

f12/f<

5.0 

 

(11),where

f;

the focal length of the entire system, and

f12;

the combined focal length of the first lens and the second lens.

10. The imaging lens of claim 1 that satisfies conditional formula (12) below:

(Nd1+Nd2+Nd3+Nd4+Nd5+Nd6)/6<

1.70 

 

(12),where

Nd1 through Nd6;

the refractive indices of the materials of the first lens through the sixth lens with respect to the d-line.

11. The imaging lens of claim 1, wherein the object-side surface of the fourth lens is an aspherical surface, both of the center and the edge of the effective diameter have positive powers, and the positive power at the edge of the effective diameter is weaker than that of the center.

12. The imaging lens of claim 1, wherein the Abbe number of the material of the first lens with respect to the d-line is greater than or equal to 40.

13. The imaging lens of claim 1, wherein the Abbe number of the material of the second lens with respect to the d-line is greater than or equal to 25.

14. The imaging lens of claim 1, wherein the Abbe number of the material of the fourth lens with respect to the d-line is greater than or equal to 40.

15. The imaging lens of claim 1, wherein the Abbe number of the material of the fifth lens with respect to the d-line is greater than or equal to 40.

16. The imaging lens of claim 1, wherein the Abbe number of the material of the sixth lens with respect to the d-line is less than or equal to 32.

17. The imaging lens of claim 1 that satisfies conditional formula (4-1) below:

f56/f<

−

7.0 

 

(4-1),where

f;

the focal length of the entire system, and

f56;

the combined focal length of the fifth lens and the sixth lens.

18. The imaging lens of claim 1 that satisfies conditional formula (4-2) below:

f56/f<

−

7.2 

 

(4-2),where

f;

the focal length of the entire system, and

f56;

the combined focal length of the fifth lens and the sixth lens.

19. The imaging lens of claim 1 that satisfies conditional formula (4-3) below:

−

50.0<

f56/f<

−

7.2 

 

(4-3),where

f;

the focal length of the entire system, and

f56;

the combined focal length of the fifth lens and the sixth lens.

20. An imaging apparatus comprising:

an imaging lens of claim 1.