Endoscope objective lens and endoscope

• US 7,907,352 B2
• Filed: 04/08/2008
• Issued: 03/15/2011
• Est. Priority Date: 04/09/2007
• Status: Expired due to Fees

• Current Assignee: Fujinon Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujinon Corporation (Fujifilm Holdings Corporation)
• Inventors: Miyano, Hitoshi
• Primary Examiner(s): Martinez; Joseph
• Assistant Examiner(s): Greece; James R
• Application Number:
  US12/099,574
• Publication Number:
  US 20080249367A1
• Time in Patent Office: 1,071 Days
• Field of Search: 359/754, 359/749, 359/753, 359/762, 359751-752
• US Class Current: 359/754
• CPC Class Codes: G02B 23/243 Objectives for endoscopes

Abstract

An endoscope objective lens includes, in order from an object side, a negative first lens, a first cemented lens, an aperture diaphragm, a positive fourth lens and a second cemented lens. The negative first lens has a concave surface directed to an image side. The first cemented lens is formed by cementing a second lens and a third lens. One of the second and third lenses is positive and. The other is negative. The positive fourth lens includes a flat surface or a surface having a larger absolute value in radius of curvature, directed to the object side. The second cemented lens is formed by cementing a positive fifth lens and a negative sixth lens in order from the object side. The second cemented lens has a positive refractive power as a whole. The endoscope objective lens satisfies the following conditional expressions (1) and (2).

$\begin{array}{cc}\frac{f^2\times v_5-v_6}{R_A\times \left(\mathrm{Bf}+d_6/n_6\right)}>10& \left(1\right)\\ \mathrm{Bf}/f>2.5& \left(2\right)\end{array}$

Claims

1. An endoscope objective lens comprising, in order from an object side:

a negative first lens having a concave surface directed to an image side;

a first cemented lens formed by cementing a second lens and a third lens, one of the second and third lenses being positive and, the other being negative;

a stop;

a positive fourth lens including a flat surface or a surface having a larger absolute value in radius of curvature, directed to the object side; and

a second cemented lens formed by cementing a positive fifth lens and a negative sixth lens in order from the object side, the second cemented lens having a positive refractive power as a whole, wherein

the endoscope objective lens satisfies the following conditional expressions (1) and (2)

2. The endoscope objective lens according to claim 1, wherein the endoscope objective lens satisfies the following conditional expression (3):

1.00<

|d/f₁|<

2.00 

 

(3)

where d denotes an air-equivalent distance, on an optical axis, from an apex of the concave surface of the first lens on the image side to the stop, and

f₁ denotes a focal length of the first lens.

3. The endoscope objective lens according to claim 1, wherein the endoscope objective lens satisfies the following conditional expression (4):

0.95<

f/h<

1.05 

 

(4)

where h denotes a maximum image height.

4. The endoscope objective lens according to claim 2, wherein the endoscope objective lens satisfies the following conditional expression (4):

0.95<

f/h<

1.05 

 

(4)

where h denotes a maximum image height.

5. The endoscope objective lens according to claim 1, wherein the endoscope objective lens satisfies the following conditional expression (5):

15.0<

|ν

₂−

ν

₃| 

 

(5)

where ν

₂ is an Abbe number of the second lens, and ν

₃ is an Abbe number of the third lens.

6. The endoscope objective lens according to claim 3, wherein the endoscope objective lens satisfies the following conditional expression (5):

15.0<

|ν

₂−

ν

₃| 

 

(5)

where ν

₂ is an Abbe number of the second lens, and ν

₃ is an Abbe number of the third lens.

7. The endoscope objective lens according to claim 4, wherein the endoscope objective lens satisfies the following conditional expression (5):

15.0<

|ν

₂−

ν

₃| 

 

(5)

where ν

₂ is an Abbe number of the second lens, and ν

₃ is an Abbe number of the third lens.

8. An endoscope comprising the endoscope objective lens according to claim 1.

9. An endoscope comprising the endoscope objective lens according to claim 7.

10. An endoscope objective lens comprising, in order from an object side:

a negative first lens having a concave surface directed to an image side;

a first cemented lens formed by cementing a second lens and a third lens, one of the second and third lenses being positive and, the other being negative;

a stop;

a positive fourth lens including a flat surface or a surface having a larger absolute value in radius of curvature, directed to the object side; and

a second cemented lens formed by cementing a negative fifth lens and a positive sixth lens in order from the object side, the second cemented lens having a positive refractive power as a whole, wherein

the endoscope objective lens satisfies the following conditional expressions (1)′ and

(2)

11. The endoscope objective lens according to claim 10, wherein the endoscope objective lens satisfies the following conditional expression (3):

1.00<

|d/f₁|<

2.00 

 

(3)

where d denotes an air-equivalent distance, on an optical axis, from an apex of the concave surface of the first lens on the image side to the stop, and

f₁ denotes a focal length of the first lens.

12. The endoscope objective lens according to claim 10, wherein the endoscope objective lens satisfies the following conditional expression (4):

0.95<

f/h<

1.05 

 

(4)

where h denotes a maximum image height.

13. The endoscope objective lens according to claim 11, wherein the endoscope objective lens satisfies the following conditional expression (4):

0.95<

f/h<

1.05 

 

(4)

where h denotes a maximum image height.

14. The endoscope objective lens according to claim 10, wherein the endoscope objective lens satisfies the following conditional expression (5):

15.0<

|ν

₂−

ν

₃| 

 

(5)

where ν

₂ is an Abbe number of the second lens, and ν

₃ is an Abbe number of the third lens.

15. The endoscope objective lens according to claim 12, wherein the endoscope objective lens satisfies the following conditional expression (5):

15.0<

|ν

₂−

ν

₃| 

 

(5)

where ν

₂ is an Abbe number of the second lens, and ν

₃ is an Abbe number of the third lens.

16. The endoscope objective lens according to claim 13, wherein the endoscope objective lens satisfies the following conditional expression (5):

15.0<

|ν

₂−

ν

₃| 

 

(5)

where ν

₂ is an Abbe number of the second lens, and ν

₃ is an Abbe number of the third lens.

17. An endoscope comprising the endoscope objective lens according to claim 10.

18. An endoscope comprising the endoscope objective lens according to claim 16.

19. The endoscope objective lens according to claim 10, wherein the endoscope objective lens satisfies the following conditional expression (6′

);

ν

₅<

20 

 

(6′

).