KR102455585B1 - Lens system for endo-microscope probe - Google Patents

Abstract

The present invention proposes a lens system for an endo-microscope probe. The lens system for an endo-microscope probe according to an embodiment of the present invention, which is a lens system for an endo-microscope probe including a plurality of lenses arranged from an object side to an image side, comprises: a first lens (L1) having a flat object side surface and a convex image side surface; a second lens (L2) having an object side (O) with a radius of curvature in a convex shape and an image side (I) with a radius of curvature in a concave shape; a third lens (L3) having both sides with a radius of curvature in a convex shape; a fourth lens (L4) having an object side (O) with a radius of curvature in a convex shape and an image side (I) with a radius of curvature in a concave shape; and a fifth lens (L5) having an object side with a radius of curvature in a concave shape and an image side with a radius of curvature in a convex shape, wherein the first lens (L1) is a glass lens, and the remaining second lens (L2) to the fifth lens (L5) are made of plastic lenses capable of injection molding. Therefore, provided is a lens system for an endo-microscope probe, wherein mass production is facilitated.

Description

LENS SYSTEM FOR ENDO-MICROSCOPE PROBE

The present invention relates to a lens system for an endoscopy probe designed to be suitable for mass production and to have imaging performance close to the diffraction limit.

Endo-Microscope is a microscopic microscope that can be inserted into the human body. Recently, research and development on endoscopy probes that are miniaturized in size while maintaining high-resolution performance are being actively conducted. The endoscope probe is equipped with an objective lens to observe polyps formed in organs such as the esophagus and large intestine, and it can be said that the performance of the medical endoscope is determined by the performance of the objective lens.

In such an objective lens for an endoscope probe, a plurality of lenses are used in a form in which they are properly arranged. However, most of the lenses currently used use a glass lens whose main material is glass. Therefore, there is a problem that mass production is difficult.

Of course, a method of replacing some of the glass lenses with plastic lenses has also been proposed, but when the plastic lenses are used, it is difficult to correct chromatic aberration because the two lenses cannot be used in a form in which the effective surfaces are bonded to each other. This fundamentally limits the use of plastic lenses.

Republic of Korea Patent No. 10-1404611 (Registered on May 30, 2014) Republic of Korea Patent Publication No. 2002-0035588 (published on Nov. 11, 2002)

An object of the present invention is to solve the above problems, and only one of the lenses used in the objective lens for the probe uses a glass lens and the rest uses a plastic lens to facilitate mass production. Provides a lens system.

Another object of the present invention is to provide a lens system for an endoscope probe, which solves a problem of chromatic aberration that may occur when a plastic lens is used for an objective lens for a probe, thereby bringing imaging performance close to the diffraction limit.

Another object of the present invention is to provide a lens system for an endoscopy probe that minimizes distortion while maintaining a small size for insertion into the human body.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A lens system for an endoscopy probe according to an embodiment of the present invention for achieving the above object is a lens system for an endoscopy probe comprising a plurality of lenses arranged from an object side to an image side, a flat object side surface and a convex image side surface having a first lens (L1); a second lens (L2) having a convex radius of curvature on the object side and a concave radius of curvature on the image side; a third lens (L3) having both sides of the convex radius of curvature; a fourth lens (L4) having an object side having a convex radius of curvature and an image side having a concave radius of curvature; and a fifth lens L5 having a concave radius of curvature on the object side and a convex radius of curvature on the image side.

According to the present invention, the ratio of the absolute value of the radius of curvature of the first lens L1 to the radius of curvature of the object-side convex surface of the second lens L2 may be greater than 1.8 and less than 7.0.

According to the present invention, the sum of Abbe constants for the third lens L3 and the fourth lens L4 is divided by the sum of Abbe constants for the second lens L2 and the fifth lens L5. When , the ratio may be greater than 2.0 and less than 2.7.

According to the present invention, the ratio of the distance between the image side surface of the fifth lens L5 from the image plane to the distance between the object side surfaces of the first lens L1 may be greater than 10.0 and less than 20.0.

According to the present invention, the angle of the chief ray incident on the upper surface may be 0 degrees or more and less than 2 degrees based on the optical axis.

According to the present invention, the ratio of the effective focal length (EFL) of the entire lens system divided by the diameter of the lens may be greater than 1.4 and less than 10.0.

According to the present invention, the distance from the object side to the upper side may be 10.0 mm or less.

According to the present invention, the diameter of the first lens (L1) to the fifth lens (L5) may be 2mm.

According to the present invention, the first lens L1 is a glass lens, and the second lens L2 to the fifth lens L5 are plastic lenses capable of injection molding.

Other specific details of the invention are included in the detailed description and drawings.

According to the present invention, cost reduction and productivity improvement can be achieved by configuring a lens system for an endoscopy probe using only one glass lens and the rest using plastic, and the MTF (Modulation Transfer Function) is close to the diffraction limit. Imaging performance can be maximized. In addition, it is possible to minimize distortion aberration while having a small size that can be inserted into the human body.

1 is a diagram schematically illustrating a lens system for an endoscope probe according to an embodiment of the present invention.
2 is a view illustrating a lens system for an endoscope probe through which light rays pass based on an optical axis according to a first numerical embodiment of the present invention.
FIG. 3 is a diagram illustrating MTF characteristics according to the first numerical embodiment of FIG. 2 .
FIG. 4 is a diagram illustrating optical distortion according to the first numerical embodiment of FIG. 2 .
5 is a view illustrating a lens system for an endoscopy probe through which light rays pass based on an optical axis according to a second numerical embodiment of the present invention.
FIG. 6 is a diagram illustrating MTF characteristics according to the second numerical embodiment of FIG. 5 .
FIG. 7 is a diagram illustrating optical distortion according to the second numerical embodiment of FIG. 5 .
8 is a view illustrating a lens system for an endoscopy probe through which light rays pass based on an optical axis according to a third numerical embodiment of the present invention.
9 is a diagram illustrating MTF characteristics according to the third numerical embodiment of FIG. 8 .
FIG. 10 is a diagram illustrating optical distortion according to the third numerical embodiment of FIG. 8 .
11 is a view illustrating a lens system for an endoscopy probe through which light rays pass based on an optical axis according to a fourth numerical embodiment of the present invention.
12 is a diagram illustrating MTF characteristics according to the fourth numerical embodiment of FIG. 11 .
13 is a diagram illustrating optical distortion according to the fourth numerical embodiment of FIG. 11 .
14 is a view illustrating a lens system for an endoscopy probe through which light rays pass based on an optical axis according to a fifth numerical embodiment of the present invention.
15 is a diagram illustrating MTF characteristics according to the fifth numerical example of FIG. 14 .
FIG. 16 is a diagram illustrating optical distortion according to the fifth numerical embodiment of FIG. 14 .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

Although first, second, etc. are used to describe various elements, components, and/or sections, it should be understood that these elements, components, and/or sections are not limited by these terms. These terms are only used to distinguish one element, component, or sections from another. Accordingly, it goes without saying that the first element, the first element, or the first section mentioned below may be the second element, the second element, or the second section within the spirit of the present invention.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural, unless specifically stated otherwise in the phrase. As used herein, "comprises" and/or "made of" refers to a referenced component, step, operation and/or element of one or more other components, steps, operations and/or elements. The presence or addition is not excluded.

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly defined in particular.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.
1 is a view showing an optical diagram of a lens system for an endoscope probe according to an embodiment of the present invention.

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Referring to FIG. 1 , the lens system 100 for an endoscopy probe includes a plurality of lenses arranged from an object side (O) to an image side (I), and a first lens (L1) to a fifth lens (L5) are They may be sequentially arranged along the optical axis 50 from the object side (O) to the upper side (I). The light beam sequentially passes through the first lens L1 to the fifth lens L5. Although not shown in the drawings, an diaphragm, a filter, and the like may be disposed on the upper side (I).

In this case, an object side may indicate a direction in which an object, which is a subject, is present, and an image side may indicate a direction in which an image plane (IMG) on which an image is formed. Hereinafter, the object-side surface may indicate a lens surface in a direction in which the object is present, and the image-side surface may indicate a lens surface in a direction in which the image surface is present.

The first lens L1 may have an object-side surface 1 that is flat toward the object side O and an image-side surface 2 that is convex toward the image side.

The second lens L2 may have a convex radius of curvature on the object side and a concave radius of curvature on the image side. The radius of curvature of the object-side surface 3 and the image-side surface 4 of the second lens L2 may be different from each other.

Both sides of the third lens L3 may have convex radii of curvature. The object side surface 5 of the third lens L3 may have a convex shape to correspond to the concave image side surface 4 of the second lens L2 .

The fourth lens L4 may have a convex radius of curvature on the object side and a concave radius of curvature on the image side.

The fifth lens L5 may have a concave surface 9 toward the object side O. As shown in FIG. In addition, the fifth lens L5 may have a convex surface 10 toward the image side (I). Therefore, the fifth lens L5 may be a plano-convex lens.

The above-mentioned first lens L1 to fifth lens L5 are manufactured to have a diameter of 2 mm for insertion into the human body. Also, for mass production, only the first lens L1 is a glass lens, and a plastic lens is used for the second lens L2 to the fifth lens L5. Because plastic lenses can be manufactured by mold injection, mass production is possible faster than glass lenses. Here, the reason why only the first lens L1 is used as a glass lens is that it does not generate harmful substances as a lens directly in contact with the human body.

The lens system 100 for an endoscope probe according to an embodiment of the present invention may satisfy the following Conditional Expressions 1 to 4.

<Condition 1>

은 제1 렌즈(L1)의 곡률반경이며,

는 제2 렌즈(L2)에서 제1 렌즈(L1)와 마주보는 면의 곡률반경이다. 따라서, 제1 렌즈(L1)의 곡률반경의 절대값 대비하여 제2 렌즈(L2)의 곡률반경의 절대값의 비가 1.8보다 크고 7.0보다 작다.From here,

is the radius of curvature of the first lens (L1),

is the radius of curvature of the surface facing the first lens L1 in the second lens L2. Accordingly, the ratio of the absolute value of the radius of curvature of the second lens L2 to the absolute value of the radius of curvature of the first lens L1 is greater than 1.8 and less than 7.0.

<Condition 2>

는 제2 렌즈(L2)의 아베수,

는 제3 렌즈(L2)의 아베수,

는 제4 렌즈(L4)의 아베수,

는 제5 렌즈(L5)의 아베수이다. 따라서, 따라서, 제3 렌즈(L3)의 아베수와 제4 렌즈(L4)의 아베수의 합의 절대값 대비하여 제2 렌즈(L2)의 아베수와 제5 렌즈(L5)의 아베수의 합의 절대값의 비가 2.0보다 크고 2.7보다 작다.From here,

is the Abbe's number of the second lens L2,

is the Abbe number of the third lens L2,

is the Abbe's number of the fourth lens L4,

is the Abbe number of the fifth lens L5. Accordingly, the sum of the Abbe number of the second lens L2 and the Abbe number of the fifth lens L5 is compared to the absolute value of the sum of the Abbe number of the third lens L3 and the Abbe number of the fourth lens L4. The ratio of absolute values is greater than 2.0 and less than 2.7.

<Condition 3>

는 제1 렌즈(L1)의 물체측면(1)에서 물체면(OBJ)까지의 거리이며,

는 제5 렌즈(L5)의 상측면(10)에서 상면(IMG)까지의 거리이다. 여기에서, 물체면(OBJ)는 렌즈계가 피부에 직접 닿는 부분이며, 상면(IMG)은 상이 결상되는 부분이다. 따라서, 물체면(OBJ) 및 제1 렌즈(L1)의 물체측면(1) 사이의 거리 대비하여 상면 (IMG) 및 제5 렌즈(L5)의 상측면(10) 사이의 거리의 비가 10.0보다 크고 20.0보다 작다.From here,

is the distance from the object side surface 1 of the first lens L1 to the object surface OBJ,

is the distance from the image side surface 10 to the image surface IMG of the fifth lens L5. Here, the object plane OBJ is a part where the lens system directly contacts the skin, and the image plane IMG is a part on which an image is formed. Accordingly, the ratio of the distance between the image plane IMG and the image plane 10 of the fifth lens L5 to the distance between the object plane OBJ and the object plane 1 of the first lens L1 is greater than 10.0. less than 20.0.

<Condition 4>

유효초점거리,

렌즈 직경이다. 따라서 렌즈계 전체의 유효초점거리를 렌즈의 직경으로 나눈 비가 1.4 초과 10.0 미만이다. From here,

effective focal length,

is the lens diameter. Therefore, the ratio of the effective focal length of the entire lens system divided by the diameter of the lens is greater than 1.4 and less than 10.0.

In addition, it is preferable that the angle of the principal ray incident on the upper surface IMG is 0 degrees or more and less than 2 degrees with respect to the optical axis 50 . This is because the size of the lens system can be minimized when the chief ray is formed on the image plane IMG by allowing the chief ray to travel substantially in parallel.

On the other hand, since the endoscope has a small diameter and must be inserted into the human body, the size of the objective lens applied to the probe of the endoscope must also be small. When the angle of the chief ray is aligned almost horizontally with the optical axis, the size of the lens system does not need to be increased, so that it can be applied as an objective lens for a probe of an endoscope.

Hereinafter, detailed data of the lens system for an endoscope probe of the present invention will be described in each embodiment.

Table 1 below shows specific design data of the first to fifth numerical examples of the lens system for an endoscope probe.

first embodiment second embodiment third embodiment 4th embodiment 5th embodiment effective focal length 12.61 3.61 3.45 1.50 4.79 design wavelength 488 to 550 nm 488 to 550 nm 488 to 550 nm 488 to 550 nm 488 to 550 nm NA(O) 0.550 0.550 0.550 0.550 0.550 NA(I) 0.220 0.220 0.220 0.220 0.220 OAL 7.180 6.880 7.126 7.180 7.180 TTL 7.993 7.959 7.944 7.993 7.990

Here, the effective focal length is the focal length of the lens system, and the design wavelength is the design wavelength. Further, NA(O) is NA (Numerical Aperture) on the object side, and NA(I) is NA on the upper side. And, OAL is the distance from the center of the incident surface of the first lens L1 to the center of the exit surface of the fifth lens L5, and TTL is the distance from the center of the incident surface of the object surface to the center of the output surface of the image surface. is the street

Surface number OBJ denotes an object plane on which the lens system directly contacts the skin, and plane number IMG denotes an image plane on which an image is formed. Surface numbers 1 and 2 indicate an object-side surface and an image-side surface of the first lens L1, respectively. Surface numbers 3 and 4 indicate an object-side surface and an image-side surface of the second lens L2, respectively. Surface numbers 5 and 6 indicate the object-side surface and the image-side surface of the third lens L3. Surface numbers 7 and 8 indicate an object-side surface and an image-side surface of the fourth lens L4, respectively. Surface numbers 9 and 10 indicate an object-side surface and an image-side surface of the fifth lens L5, respectively.

Therefore, the OAL is the thickness and distance from face numbers 1 to 10. And, the TTL is the thickness and distance from the face number OBJ to 10.

In addition, ASP of the radius of curvature represents an aspherical surface, and the unit of distance in lens data is mm.

Aspheric data can be calculated by Equation 1 below.

는 렌즈의 정점으로부터 광축 방향으로의 거리이며,

는 렌즈의 정점에서의 곡률(곡률반경의 역수)이고,

는 광축에 수직한 방향으로의 거리이고,

는 코닉 상수(conic constant)이다. 그리고,

,

,

,

,

등은 비구면 계수이다. From here,

is the distance from the vertex of the lens in the direction of the optical axis,

is the curvature (reciprocal of the radius of curvature) at the vertex of the lens,

is the distance in the direction perpendicular to the optical axis,

is a conic constant. and,

,

,

,

,

etc. are aspheric coefficients.

2 is a view illustrating a lens system for an endoscope probe through which light rays pass based on an optical axis according to a first numerical embodiment of the present invention. In addition, FIG. 3 is a diagram illustrating MTF characteristics according to the first numerical embodiment of FIG. 2 . And, FIG. 4 is a diagram illustrating optical distortion according to the first numerical embodiment of FIG. 2 .

Referring to FIG. 2 , the first lens L1 may have an object-side surface 1 that is flat toward the object side O and an image-side surface 2 that is convex toward the image side. In the second lens L2, the object side O may have a convex radius of curvature, and the image side I may have a concave radius of curvature. The third lens L3 may have both side surfaces 5 and 6 having a convex radius of curvature. In the fourth lens L4, the object side O may have a convex radius of curvature, and the image side I may have a concave radius of curvature. The fifth lens L5 may have a concave surface 9 on the object side O and a convex surface 10 on the image side I. In addition, all of the first to fifth lenses L1 to L5 are disposed to be spaced apart from each other by a predetermined distance. In addition, only the first lens L1 is a glass lens, and the remaining second to fifth lenses L2 to L5 are plastic lenses that can be molded by injection molding.

Table 2 below shows specific data of each lens surface on the optical path according to the first numerical embodiment.

face number radius of curvature curvature thickness, distance refractive index (nd) Abbesu (Vd) OBJ -12.501 Concave (aspherical) 0.060 1.333 55.72 One Infinity plane 0.900 1.883 40.76 2 -1.090 convex (spherical) 0.260 - - 3 +3.440 Convex (aspherical) 0.800 1.633 23.35 4 +0.789 concave (aspherical) 0.100 5 +0.945 Convex (aspherical) 1.100 1.509 56.60 6 -1.048 Convex (aspherical) 0.920 7 +0.945 Convex (aspherical) 1.000 1.531 55.90 8 +2.235 Concave (aspherical) 0.400 9 -0.795 Concave (aspherical) 1.700 1.633 23.35 10 -1.172 Convex (aspherical) 0.753 IMG Infinity plane 0.000 - -

Table 3 below shows the coefficients for the aspherical surface of the lens system for the endoscope probe according to the first numerical embodiment.

face number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 3 0.00 -0.83 -1.73 5.50 -19.10 0.00 4 0.00 -1.00 -0.48 2.58 -3.79 0.00 5 0.00 -0.57 -0.13 0.74 -0.79 0.00 6 0.00 -0.18 0.46 -0.45 0.30 0.00 7 0.00 -0.50 0.05 0.13 -0.31 0.00 8 0.00 -1.92 4.17 5.40 3.29 0.00 9 0.00 -3.00 13.22 -31.51 33.58 0.00 10 0.00 -1.45 7.08 10.37 25.81 0.00

3 and 4 , both the MTF characteristics and the optical distortion according to the first numerical example are within satisfactory ranges. In FIG. 3 , a solid line is a tangential direction, and a dotted line is a radial direction.

5 is a view illustrating a lens system for an endoscopy probe through which light rays pass based on an optical axis according to a second numerical embodiment of the present invention. Also, FIG. 6 is a diagram illustrating MTF characteristics according to the second numerical embodiment of FIG. 5 . And, FIG. 7 is a diagram illustrating optical distortion according to the second numerical embodiment of FIG. 5 .

Referring to FIG. 5 , the first lens L1 may have an object-side surface 1 that is flat toward the object side O and an image-side surface 2 that is convex toward the image side. In the second lens L2, the object side O may have a convex radius of curvature, and the image side I may have a concave radius of curvature. The third lens L3 may have both side surfaces 5 and 6 having a convex radius of curvature. In the fourth lens L4, the object side O may have a convex radius of curvature, and the image side I may have a concave radius of curvature. The fifth lens L5 may have a concave surface 9 on the object side O and a convex surface 10 on the image side I. The first to fifth lenses L1 to L5 are all arranged to be spaced apart from each other by a predetermined distance. In addition, only the first lens L1 is a glass lens, and the remaining second to fifth lenses L2 to L5 are plastic lenses that can be molded by injection molding.

Table 4 below shows specific data of each lens surface on the optical path according to the second numerical example.

face number radius of curvature curvature thickness, distance refractive index (nd) Abbesu (Vd) OBJ -12.501 Concave (aspherical) 0.060 1.333 55.72 One Infinity plane 0.900 1.923 20.88 2 -1.090 convex (spherical) 0.260 - - 3 +6.202 Convex (aspherical) 0.800 1.633 23.35 4 +0.753 Concave (aspherical) 0.100 5 +0.892 Convex (aspherical) 1.100 1.509 56.60 6 -0.964 Convex (aspherical) 0.660 7 +1.904 Convex (aspherical) 1.000 1.531 55.90 8 +1.103 Concave (aspherical) 0.360 9 -0.866 Concave (aspherical) 1.700 1.633 23.35 10 -1.111 Convex (aspherical) 1.019 IMG Infinity plane 0.000 - -

Table 5 below shows the coefficients for the aspheric surface of the lens system for the endoscope probe according to the second numerical embodiment.

face number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 3 0.00 -1.01 -2.37 8.85 -23.88 0.00 4 0.00 -1.27 -0.18 2.39 -4.79 0.00 5 0.00 -0.52 -0.17 0.86 -1.07 0.00 6 0.00 -0.07 0.60 -0.49 0.49 0.00 7 0.00 -0.43 0.29 0.28 -0.19 0.00 8 0.00 -2.06 3.03 4.72 5.70 0.00 9 0.00 -2.58 4.42 -3.28 10.54 0.00 10 0.00 -0.98 2.99 6.31 6.07 0.00

6 and 7 , both MTF characteristics and optical distortion according to the second numerical example are within satisfactory ranges.

8 is a view illustrating a lens system for an endoscopy probe through which light rays pass based on an optical axis according to a third numerical embodiment of the present invention. Also, FIG. 9 is a diagram illustrating MTF characteristics according to the third numerical embodiment of FIG. 8 . And, FIG. 10 is a diagram illustrating distortion aberration according to the third numerical embodiment of FIG. 8 .

Referring to FIG. 8 , the first lens L1 may have an object-side surface 1 that is flat toward the object side O and an image-side surface 2 that is convex toward the image side. The second lens L2 may have an object side surface 3 having a convex radius of curvature toward the object side O and an image side surface 4 concave toward the image side I. Both side surfaces 5 and 6 of the third lens L3 may have a convex radius of curvature. In the fourth lens L4, the object side O may have a convex radius of curvature, and the image side I may have a concave radius of curvature. The fifth lens L5 may have a concave surface 9 on the object side O and a convex surface 10 on the image side I. In addition, all of the first to fifth lenses L1 to L5 are disposed to be spaced apart from each other by a predetermined distance. In addition, only the first lens L1 is a glass lens, and the remaining second to fifth lenses L2 to L5 are plastic lenses that can be molded by injection molding.

Table 6 below shows specific data of each lens surface on the optical path according to the third numerical example.

face number radius of curvature curvature thickness, distance refractive index (nd) Abbesu (Vd) OBJ -12.501 Concave (aspherical) 0.060 1.333 55.72 One Infinity plane 0.900 1.713 53.89 2 -1.090 convex (spherical) 0.126 3 +2.032 Convex (aspherical) 0.800 1.633 23.35 4 +0.765 Concave (aspherical) 0.100 5 +0.893 Convex (aspherical) 1.100 1.509 56.60 6 -1.036 Convex (aspherical) 1.070 7 +1.014 Convex (aspherical) 1.000 1.531 55.90 8 +4.338 Concave (aspherical) 0.330 9 -0.762 Concave (aspherical) 1.700 1.633 23.35 10 -1.094 Convex (aspherical) 0.758 IMG Infinity plane 0.000 - -

Table 7 below shows coefficients for the aspheric surface of the lens system for endoscopy probes according to the third numerical example.

face number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 3 0.00 -0.78 -0.97 0.69 -7.13 0.00 4 0.00 -1.00 -0.59 2.55 -4.20 0.00 5 0.00 -0.56 -0.10 0.76 -0.97 0.00 6 0.00 -0.08 0.37 -0.33 0.39 0.00 7 0.00 -0.41 0.05 0.04 -0.26 0.00 8 0.00 -1.91 4.23 5.62 3.34 0.00 9 0.00 -7.09 14.02 -33.67 35.90 0.00 10 0.00 -1.43 7.49 21.11 25.30 0.00

9 and 10 , both MTF characteristics and optical distortion according to the third numerical example are within satisfactory ranges.

11 is a view illustrating a lens system for an endoscopy probe through which light rays pass based on an optical axis according to a fourth numerical embodiment of the present invention. Also, FIG. 12 is a diagram illustrating MTF characteristics according to the fourth numerical embodiment of FIG. 11 . And, FIG. 13 is a diagram illustrating optical distortion according to the fourth numerical embodiment of FIG. 11 .

Referring to FIG. 11 , the first lens L1 may have a flat object side surface 1 toward the object side O and an image side surface 2 convex toward the image side I. Referring to FIG. In the second lens L2, the object side O may have a convex radius of curvature, and the image side I may have a concave radius of curvature. Both side surfaces 5 and 6 of the third lens L3 may have a convex radius of curvature. In the fourth lens L4, the object side O may have a convex radius of curvature, and the image side I may have a concave radius of curvature. The fifth lens L5 may have a concave surface 9 on the object side O and a convex surface 10 on the image side I. In addition, all of the first to fifth lenses L1 to L5 are disposed to be spaced apart from each other by a predetermined distance. In addition, only the first lens L1 is a glass lens, and the remaining second to fifth lenses L2 to L5 are plastic lenses that can be molded by injection molding.

Table 8 below shows specific data of each lens surface on the optical path according to the fourth numerical example.

face number radius of curvature curvature thickness, distance refractive index (nd) Abbesu (Vd) OBJ -12.501 Concave (aspherical) 0.060 1.333 55.72 One Infinity plane 0.900 1.883 40.76 2 - -1.090 convex (spherical) 0.260 3 +4.440 Convex (aspherical) 0.800 1.633 23.35 4 +0.797 Concave (aspherical) 0.100 5 +0.942 Convex (aspherical) 1.100 1.531 55.90 6 -1.087 Convex (aspherical) 0.920 7 +0.940 Convex (aspherical) 1.000 1.509 56.60 8 +2.508 Concave (aspherical) 0.400 9 -0.770 Concave (aspherical) 1.700 1.633 23.35 10 -1.139 Convex (aspherical) 0.753 IMG Infinity plane 0.000 - -

Table 9 below shows the coefficients for the aspheric surface of the lens system for the endoscope probe according to the fourth numerical embodiment.

face number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 3 0.00 -0.83 -1.31 0.27 -6.46 0.00 4 0.00 -1.92 -0.67 2.60 -3.51 0.00 5 0.00 -0.52 -0.16 0.72 -0.72 0.00 6 0.00 -0.16 0.45 -0.42 0.30 0.00 7 0.00 -0.51 0.07 0.14 -0.36 0.00 8 0.00 -1.92 4.30 5.82 3.67 0.00 9 0.00 -3.00 13.69 -35.47 43.22 0.00 10 0.00 -1.52 7.84 23.82 30.96 0.00

12 and 13 , both MTF characteristics and optical distortion according to the fourth numerical example are within satisfactory ranges.

14 is a view illustrating a lens system for an endoscopy probe through which light rays pass based on an optical axis according to a fifth numerical embodiment of the present invention. Also, FIG. 15 is a diagram illustrating MTF characteristics according to the fifth numerical example of FIG. 14 . And, FIG. 16 is a diagram illustrating optical distortion according to the fifth numerical embodiment of FIG. 14 .

Referring to FIG. 14 , the first lens L1 may have an object-side surface 1 that is flat toward the object side O and an image-side surface 2 that is convex toward the image side. In the second lens L2, the object side O may have a convex radius of curvature, and the image side I may have a concave radius of curvature. The third lens L3 may have both side surfaces 5 and 6 having a convex radius of curvature. In the fourth lens L4, the object side O may have a convex radius of curvature, and the image side I may have a concave radius of curvature. The fifth lens L5 may have a concave surface 9 on the object side O and a convex surface 10 on the image side I. In addition, all of the first to fifth lenses L1 to L5 are disposed to be spaced apart from each other by a predetermined distance. In addition, only the first lens L1 is a glass lens, and the remaining second to fifth lenses L2 to L5 are plastic lenses that can be molded by injection molding.
Table 10 below shows specific data of each lens surface on the optical path according to the fifth numerical example.

face number radius of curvature curvature thickness, distance refractive index (nd) Abbesu (Vd) OBJ -12.501 Concave (aspherical) 0.060 1.333 55.72 One Infinity plane 0.900 1.883 40.76 2 -1.090 convex (spherical) 0.260 3 +3.537 Convex (aspherical) 0.800 1.633 23.35 4 +0.786 Concave (aspherical) 0.100 5 +0.936 Convex (aspherical) 1.100 1.509 56.60 6 -1.042 Convex (aspherical) 0.920 7 +0.927 Convex (aspherical) 1.000 1.509 56.60 8 +2.232 Concave (aspherical) 0.400 9 -0.809 Concave (aspherical) 1.700 1.633 23.35 10 -1.180 Convex (aspherical) 0.750 IMG Infinity plane 0.000 - -

Table 11 below shows the coefficients for the aspheric surface of the lens system for endoscopy probes according to the fifth numerical example.

face number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 3 0.00 -0.85 -1.52 3.41 -14.87 0.00 4 0.00 -0.99 -0.50 2.57 -3.87 0.00 5 0.00 -0.56 -0.14 0.73 -0.80 0.00 6 0.00 -0.17 0.46 -0.45 0.33 0.00 7 0.00 -0.51 0.04 0.10 -0.37 0.00 8 0.00 -1.92 4.15 5.44 3.39 0.00 9 0.00 -3.00 13.12 -32.04 36.59 0.00 10 0.00 -1.45 7.12 20.72 25.82 0.00

15 and 16 , both the MTF characteristic and the optical distortion are within a satisfactory range.

The following shows that the first to fifth embodiments satisfy the conditions of Conditional Expressions 1 to 4, respectively.

face number

conditional expression 1 first embodiment -1.090 3.440 3.156 second embodiment -1.090 6.202 5.690 third embodiment -1.090 2.030 1.862 4th embodiment -1.090 4.440 4.073 5th embodiment -1.090 3.537 3.245

face number

condition 2 first embodiment 112.50 46.70 2.41 second embodiment 112.50 46.70 2.41 third embodiment 112.50 46.70 2.41 4th embodiment 112.50 46.70 2.41 5th embodiment 113.20 46.70 2.42

face number

conditional expression 3 first embodiment 0.060 0.753 12.55 second embodiment 0.060 1.019 16.98 third embodiment 0.060 0.758 12.63 4th embodiment 0.060 0.753 12.55 5th embodiment 0.060 0.750 12.50

face number

condition 4 first embodiment 2.00 12.61 6.31 second embodiment 2.00 3.61 1.81 third embodiment 2.00 3.45 1.73 4th embodiment 2.00 1.50 0.75 5th embodiment 2.00 4.79 2.40

In the lens system for an endoscopy probe according to an embodiment of the present invention, only the first lens in contact with the human body uses a glass lens, and the remaining second to fifth lenses use plastic lenses to enable mass production. and the imaging performance can be brought close to the diffraction limit.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains can realize that the present invention can be embodied in other specific forms without changing the technical spirit or essential features. you will be able to understand Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

L1: first lens
L2: second lens
L3: third lens
L4: fourth lens
L5: 5th lens

Claims (9)

A lens system for an endoscopy probe comprising a plurality of lenses arranged from an object side to an image side,
a first lens (L1) having a flat object side surface and a convex image side surface;
a second lens (L2) having a convex radius of curvature on the object side and a concave radius of curvature on the image side;
a third lens (L3) having both sides of the convex radius of curvature;
a fourth lens (L4) having an object side having a convex radius of curvature and an image side having a concave radius of curvature; and
A lens system for an endoscopy probe, characterized in that the object side has a concave radius of curvature and the image side includes a fifth lens (L5) having a convex radius of curvature. The method of claim 1,
The ratio of the radius of curvature of the object-side convex surface of the second lens (L2) to the absolute value of the radius of curvature of the first lens (L1) is greater than 1.8 and less than 7.0. The method of claim 1,
When the sum of Abbe constants for the third lens L3 and the fourth lens L4 is divided by the sum of Abbe constants for the second lens L2 and the fifth lens L5, the ratio exceeds 2.0 Lens system for endoscopy probes less than 2.7. The method of claim 1,
A lens system for an endoscopy probe in which the ratio of the distance between the image side surface of the fifth lens (L5) to the image plane compared to the distance between the object side surfaces of the first lens (L1) is greater than 10.0 and less than 20.0. The method of claim 1,
A lens system for endoscopy probes in which the angle of the chief ray incident on the image plane is 0 degrees or more and less than 2 degrees with respect to the optical axis. The method of claim 1,
A lens system for endoscopy probes in which the ratio of the effective focal length (EFL) of the entire lens system divided by the diameter of the lens is greater than 1.4 and less than 10.0. The method of claim 1,
A lens system for endoscopy probes with a distance from the object side to the image side of 10.0 mm or less. The method of claim 1,
The first lens (L1) to the fifth lens (L5) has a diameter of 2 mm for an endoscope probe lens system. The method of claim 1,
The first lens L1 is a glass lens,
The second lens (L2) to the fifth lens (L5) is a lens system for an endoscope probe, which is a plastic lens capable of injection molding.

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