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Objective lens for endoscope

A technology for endoscopes and objective lenses, applied in the field of objective lenses, can solve problems such as the difficulty in correcting chromatic aberration of magnification, and achieve good correction and good effects of chromatic aberration of magnification

Active Publication Date: 2009-04-15
FUJI PHOTO OPTICAL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, in a lens system with a long back focus, there are no optical components near the image plane, so correction of chromatic aberration of magnification is not easy
Although the objective lens for an endoscope described in Patent Document 1 has a sufficient back focus, there is still room for improvement in terms of correction of chromatic aberration of magnification

Method used

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  • Objective lens for endoscope
  • Objective lens for endoscope
  • Objective lens for endoscope

Examples

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Embodiment Construction

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0032] figure 1 A first configuration example of an objective lens for an endoscope according to an embodiment of the present invention is shown. This configuration example is the same as the first numerical example described later ( Figure 5 ) lens configuration correspondence. figure 2 A second configuration example is shown. This configuration example is the same as the second numerical example ( Figure 6 ) lens configuration correspondence. image 3 A third configuration example is shown. This configuration example is the same as the third numerical example ( Figure 7 ) lens configuration correspondence. Figure 4 A fourth configuration example is shown. This configuration example is the same as the fourth numerical example ( Figure 8 ) lens configuration correspondence. exist Figure 1 ~ Figure 4 In , the symbol Ri represents the radius o...

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Abstract

The invention provides an objective lens for endoscope, which can not only ensure the sufficient rear cut-off distance of a light path transformation prism is inserted on the image side, but also well correct ratio chromatism. The objective lens for endoscope with the rear cut-off distance (Bf) of an overall system longer than the length of 2.5 times of the synthesized focal length f of the overall system comprises the follows in order on the object side: a front divergent lens system (G1); an aperture stop (St) and a back convergent lens system (G2). A joint lens(L34) consisting of a third lens (L3) and a fourth lens (L4) is arranged on the image side, which is closest to the back convergent lens system (G2). The joint lens (L34) meets the following conditional expression:|Upsilon3-Upsilon4|*f<2> / (|RA|*(Bf+DA / n4)) is more than or equal to 9 ellipsis ellipsis In the conditional expression, Upsilon 3 is the Abbe number of a third lens (L3); Upsilon 4 is the Abbe number of a fourth lens (L4); RA is the radius of curvature of the joint face of the third lens (L3) and the fourth lens (L4); DA is the central thickness of the fourth lens (L4); n4 is the refractive index of the fourth lens (L4).

Description

technical field [0001] The present invention relates to an objective lens provided at the front end of an endoscope, and more particularly to an objective lens for an endoscope corresponding to an optical system having a long back focus such as an optical path conversion prism that can be disposed on the image surface side. Background technique [0002] Conventionally, an endoscope having a structure in which a solid-state imaging device such as a CCD (Charge Coupled Device) is arranged in parallel to the longitudinal direction at a front end portion is known. Figure 17 The outline of the objective optical system in this endoscope is shown. Such as Figure 17 As shown, the solid-state imaging device 200 is arranged at the front end of the endoscope so as to be parallel to the axial direction (longitudinal direction) Z. Furthermore, an optical path conversion prism 102 is interposed between the objective lens 100 and the solid-state imaging device 200 via a cover glass (cove...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G02B13/00
Inventor 宫野俊
Owner FUJI PHOTO OPTICAL CO LTD