Endoscope image pickup optical system

• US 6,905,462 B1
• Filed: 09/06/2000
• Issued: 06/14/2005
• Est. Priority Date: 09/08/1999
• Status: Expired due to Term

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: Homma, Hiroyuki, Konno, Sayaka
• Primary Examiner(s): Leubecker, John P.
• Application Number:
  US10/070,278
• Time in Patent Office: 1,742 Days
• Field of Search: 600/176, 600/160, 600/167, 600/109, 359/363, 359/753, 359/798, 359/809, 348/65, 348/71, 348/340, 348/794
• US Class Current: 600/176
• CPC Class Codes: G02B 23/243 Objectives for endoscopes
• CPC Class Codes: G02B 23/2484 Arrangements in relation to a camera or imaging device processing or control of video signals generated by an endoscope H04N23/60, H04N23/70
• CPC Class Codes: G02B 9/12 having three components only
• CPC Class Codes: H04N 23/555 for picking-up images in sites, inaccessible due to their dimensions or hazardous conditions, e.g. endoscopes or borescopes

Abstract

An endoscope optical system is capable of obtaining favorable endoscopic images at all times by overcoming the conventional disadvantages that diagnosis is hindered by image quality disturbance due to the increase in pixel density resulting from the reduction in pixel pitch of solid-state image pickup devices and also due to the conventional arrangement of an objective front optical element in an optical system having a short focal length or in an optical system having a large F-number. In an image pickup apparatus using a monochromatic high-density solid-state image pickup device in which the average pixel pitch (H+V)/2 of the pixel pitch H in the horizontal direction and the pixel pitch V in the vertical direction with respect to the monitor scanning line is not more than 4.65 μm, or using an interline type color high-density solid-state image pickup device in which the average pixel pitch (H+V)/2 is not more than 3.1 μm, the volume V₁ of an air layer between a plane-parallel plate (F1) closest to the object side in the image pickup optical system and a piano-concave negative lens (L1) satisfies the following condition:
V₁<4 mm³  (1)

Claims

1. An endoscope image pickup optical system in an image pickup apparatus using a monochromatic high-density solid-state image pickup device in which an average pixel pitch (H+V)/2 of a pixel pitch H in a horizontal direction and a pixer pitch V in a vertical direction with respect to a monitor scanning line is not more than 4.65 μ

m, or using an interline type color high-density solid-state image pickup device in which an average pixel pitch (H+V)/2 is not more than 3.1 μ

m,

wherein a volume V₁ of an air layer between an optical element closest to an object side in the image pickup optical system and a second optical element immediately subsequent to said optical element toward an image side satisfies the following condition;

V₁<

4 mm³ 

 

(1).

2. An endoscope image pickup optical system according to claim 1, wherein a distance d along an optical axis from an image-side surface of the optical element closest to the object side in the image pickup optical system to an object-side surface of the second optical element immediately subsequent to said optical element toward the image side satisfies the following condition:

d<

l mm 

 

(2)

and when the optical element closest to the object side in the image pickup optical system is a lens having a concave surface directed toward the image side or a plano-concave lens cemented to a plane-parallel plate, a volume V₂ of an approximately spherically cut portion (hereinafter referred to as “

spherical segment volume”

) on a concave surface side of the lens satisfies the following condition;

V₂<

1.5 mm³ 

 

(3).

3. An endoscope image pickup optical system according to claim 2, wherein a foremost optical element is a negative lens having, in order from an object side thereof, a plane surface and a concave surface directed toward the image side.

4. An endoscope image pickup optical system according to claim 3, wherein a focal length of the image pickup optical system is not more than 2.2 mm.

5. An endoscope image pickup optical system according to claim 3, wherein an F-number of the image pickup optical system is not less than 3.5.

6. An endoscope image pickup optical system according to claim 2, wherein a focal length of the image pickup optical system is not more than 2.2 mm.

7. An endoscope image pickup optical system according to claim 2, wherein an F-number of the image pickup optical system is not less than 3.5.

8. An endoscope image pickup optical system according to claim 1, wherein a focal length of the image pickup optical system is not more than 2.2 mm.

9. An endoscope image pickup optical system according to claim 1, wherein an F-number of the image pickup optical system is not less than 3.5.

10. An endoscope image pickup optical system in an image pickup apparatus using a monochromatic high-density solid-state image pickup device in which an average pixel pitch (H+V)/2 of a pixel pitch H in a horizontal direction and a pixel pitch V in a vertical direction with respect to a monitor scanning line is not more than 4.65 μ

m, or using an interline type color high-density solid-state image pickup device in which an average pixel pitch (H+V)/2 is not more than 3.1 μ

m,

wherein when a length from a center of a viewing window to an edge thereof on an object-side surface of an optical element closest to an object side in the image pickup optical system is denoted by φ and

a maximum ray height of rays within a visual field on the object-side surface of said optical element from an optical axis of an objective optical system is denoted by h, a minimum margin Y(=φ

−

h) for the length to the edge of the objective window with respect to the ray height satisfies the following conditions;

1.0 mm<

φ

<

3.5 mm 

 

(4)

0.12 mm<

Y<

0.6 mm 

 

(5).

11. An endoscope image pickup optical system according to claim 10, wherein a focal length of the image pickup optical system is not more than 2.2 mm.

12. An endoscope objective optical system according to claim 10, wherein an F-number of the image pickup optical system is not less than 3.5.

13. An image pickup optical system in an image pickup apparatus using a monochromatic high-density solid-state image pickup device in which an average pixel pitch (H+V)/2 of a pixel pitch H in a horizontal direction and a pixel pitch V in a vertical direction with respect to a monitor scanning line is not more than 6 μ

m, or using a color high-density sold-state image pickup device in which an average pixel pitch (H+V)/2 is not more than 3 μ

m,

wherein an optical element closest to an object side in the image pickup optical system uses a material having a Knoop hardness of not less than 800.

14. An image pickup optical system according to claim 13, wherein a focal length of the image pickup optical system is not more than 2.2 mm.

15. An image pickup optical system according to claim 14, wherein a foremost optical element is a negative lens having, in order from an object side thereof, a plane surface and a concave surface directed toward an image side thereof.

16. An image pickup optical system according to claim 15, wherein a material of the optical element closest to the object side is sapphire.

17. An image pickup optical system according to claim 14, wherein a material of the optical element closest to the object side is sapphire.

18. An objective optical system according to claim 13, wherein an F-number of the image pickup optical system is not less than 3.5.

19. An image pickup optical system according to claim 18, wherein a foremost optical element is a negative lens having, in order from an object side thereof, a plane surface and a concave surface directed toward an image side thereof.

20. An image pickup optical system according to claim 19, wherein a material of the optical element closest to the object side is sapphire.

21. An image pickup optical system according to claim 18, wherein a material of the optical element closest to the object side is sapphire.

22. An image pickup optical system according to claim 13, wherein a material of the optical element closest to the object side is sapphire.