KR102158985B1 - Lens system for endo-microscope probe - Google Patents

Abstract

Provided is a lens system for an endoscope probe. The lens system for the endoscope probe according to one embodiment of the present invention, in the lens system for the endoscope probe comprising a plurality of lenses arranged from an object side to an image side, comprises: a first lens having a flat object side and a convex image side; a second lens having the image side surface to be bonded; a third lens having the object side surface bonded to the second lens; a fourth lens having at least one aspherical surface; and a fifth lens having a convex object side and a flat image side.

Description

Lens system for endoscope probe {LENS SYSTEM FOR ENDO-MICROSCOPE PROBE}

The present invention relates to a lens system for an endoscope probe.

Endo-Microscope is a microscopic microscope that can be inserted into the human body, and refers to a microscope capable of early diagnosis of diseases by acquiring high-resolution images in cell units.

In recent years, research and development on an endoscope probe with a smaller size while maintaining high resolution performance is actively progressing. The endoscopic 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 such a medical endoscope is determined by the performance of the objective lens.

Accordingly, in order to maintain the performance of the lens mounted on the endoscope probe, several aspherical lenses are used. However, as several aspherical lenses are used, cost increases and productivity decreases.

Korean Patent Registration No. 10-1404611 (registered on May 30, 2014) Korean Patent Application Publication No. 2002-0035588 (published on May 11, 2002)

The present invention is to solve the above problems, and provides a lens system for an endoscope probe capable of constructing a lens system for a probe using only one aspherical lens.

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

A lens system for an endoscope probe according to an embodiment of the present invention for achieving the above object is a lens system for an endoscope probe including a plurality of lenses arranged from an object side to an image side, and has a flat object side surface and a convex image A first lens having a side surface; A second lens having an image side surface to be bonded; A third lens having an object side surface bonded to the second lens; A fourth lens having at least one aspherical surface; And a fifth lens having a convex object side surface and a flat image side surface.

In addition, a ratio of the absolute value of the radius of curvature of the fifth lens to the absolute value of the radius of curvature of the first lens may be 0.9 to 1.6.

In addition, a ratio of the Abbe number of the third lens to the Abbe number of the second lens may be 1.9 to 2.5.

In addition, a ratio of the distance between the image surface and the image side surface of the fifth lens may be 8.5 to 40.0 compared to the distance between the object surface and the object side surface of the first lens.

In addition, 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.

In addition, the second and third lenses are, when the image side of the second lens is concave, the object side of the third lens is convex, and when the image side of the second lens is convex, the object of the third lens The sides may be concave.

In addition, the fourth lens may have the aspherical surface toward the object side.

Other specific details of the present 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 endoscope probe using one aspherical lens, and imaging performance can be maximized so that the Modulation Transfer Function (MTF) is close to the diffraction limit. have.

1 is a view schematically showing a lens system for an endoscope probe according to an embodiment of the present invention.
2 is a view showing a lens system for an endoscope probe through which light rays pass through an optical axis according to a first numerical example of the present invention.
3 is a diagram showing MTF characteristics according to the first numerical example of FIG. 2.
4 is a diagram illustrating Optical Distortion according to the first numerical embodiment of FIG. 2.
5 is a view showing a lens system for an endoscope probe through which light rays pass based on an optical axis according to a second numerical example of the present invention.
6 is a diagram showing MTF characteristics according to the second numerical example of FIG. 5.
7 is a diagram illustrating Optical Distortion according to the second numerical embodiment of FIG. 5.
8 is a diagram showing a lens system for an endoscope probe through which light rays pass based on an optical axis according to a third numerical example of the present invention.
9 is a diagram showing MTF characteristics according to the third numerical example of FIG. 8.
10 is a diagram illustrating Optical Distortion according to the third numerical embodiment of FIG. 8.
11 is a view showing a lens system for an endoscope probe through which light rays pass based on an optical axis according to a fourth numerical example of the present invention.
12 is a diagram showing MTF characteristics according to the fourth numerical example of FIG. 11.
13 is a diagram illustrating Optical Distortion according to the fourth numerical embodiment of FIG. 11.
14 is a diagram showing a lens system for an endoscope probe through which light rays pass through an optical axis according to a fifth numerical example of the present invention.
15 is a diagram showing MTF characteristics according to the fifth numerical example of FIG. 14.
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 a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms different from each other, and only these embodiments make the disclosure of the present invention complete, and common knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those who have it, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

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

The terms used in the present specification are for describing exemplary embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used in the specification, "comprises" and/or "made of" a referenced component, step, operation and/or element is one or more of other elements, steps, operations and/or elements It does not exclude presence or addition.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings that can be 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 interpreted ideally or excessively unless explicitly defined specifically.

Hereinafter, the present invention will be described in more detail according to the accompanying drawings.

1 is a view showing an optical path diagram of a lens system for an endoscope probe according to an embodiment of the present invention.

Referring to FIG. 1, the lens system 100 for an endoscope probe includes a plurality of lenses arranged from the object side O to the image side I, and the first to fifth lenses L1 to L5 are It may be sequentially arranged along the optical axis 105 from the object side (O) to the image side (I). The light rays sequentially pass through the first to fifth lenses L1 to L5. Although not shown in the drawing, a stop, 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 located, and an image side may indicate a direction in which an image plane (IMG) is formed. Hereinafter, the object-side surface may represent a lens surface in the direction in which the object is located, and the image-side surface may represent a lens surface in the direction in which the image surface is located.

The first lens L1 may have an image side surface 2 that is convex toward the image side I. Further, the first lens L1 may have an object side surface 1 that is flat toward the object side O. Therefore, the first lens L1 may be a plano-convex lens.

The second lens L2 may have an image-side surface 4 bonded to it, and the third lens L3 may have an object-side surface 4 bonded to the second lens L2. That is, the image-side surface 4 of the second lens L2 and the object-side surface 4 of the third lens L3 become a bonding surface. Accordingly, the second lens L2 and the third lens L3 may be bonded to each other to form one bonded lens.

At this time, when the image-side surface 4 of the second lens L2 is concave, the object-side surface 4 of the third lens L3 is convex, and the image-side surface 4 of the second lens L2 is convex. The object side surface 4 of the third lens L3 may be concave. The image-side surface 4 of the second lens L2 and the object-side surface 4 of the third lens L3 may be completely bonded to each other.

Further, the object-side surface 3 of the second lens L2 may be one of a flat shape, a concave shape, or a convex shape. More specifically, when the image-side surface 4 of the second lens L2 is concave, the object-side surface 3 of the second lens L2 may have a flat shape or a concave shape. In addition, when the image side surface 4 of the second lens L2 is convex, the object side surface 3 of the second lens L2 may have a flat shape or a convex shape.

In addition, the image-side surface 5 of the third lens L3 may be one of a flat shape, a concave shape, or a convex shape. More specifically, when the object side surface 4 of the third lens L3 is concave, the image side surface 5 of the third lens L3 may have a flat shape or a concave shape. In addition, when the object side surface 4 of the third lens L3 is convex, the image side surface 5 of the third lens L3 may have a flat shape or a convex shape.

The fourth lens L4 may have at least one aspherical surface. Preferably, the fourth lens L4 may have an aspherical surface toward the object side O. That is, in the fourth lens L4, the object-side surface 6 may be an aspherical surface, and the image-side surface 7 may be an aspherical surface or a spherical surface.

The fifth lens L5 may have an object side surface 8 that is convex toward the object side O. In addition, the fifth lens L5 may have an image side surface 9 that is flat toward the image side I. Therefore, the fifth lens L5 may be a plano-convex lens.

The lens system 100 for an endoscope probe according to an embodiment of the present invention may satisfy the following Conditional Expressions 1 to 3.

<Conditional Expression 1>

은 제1 렌즈(L1)의 곡률반경이며,

는 제5 렌즈(L5)의 곡률반경이다. 따라서, 제1 렌즈(L1)의 곡률반경의 절대값 대비하여 제5 렌즈(L5)의 곡률반경의 절대값의 비가 0.7보다 크고, 1.5보다 작다.From here,

Is the radius of curvature of the first lens L1,

Is a radius of curvature of the fifth lens L5. Accordingly, the ratio of the absolute value of the radius of curvature of the fifth lens L5 to the absolute value of the radius of curvature of the first lens L1 is greater than 0.7 and less than 1.5.

<Conditional Expression 2>

는 제2 렌즈(L2)의 아베수이며,

는 제3 렌즈(L3)의 아베수이다. 따라서, 제2 렌즈(L2)의 아베수의 절대값 대비하여 제3 렌즈(L3)의 아베수의 절대값의 비가 1.5보다 크고, 3.0보다 작다.From here,

Is the Abbe number of the second lens L2,

Is the Abbe number of the third lens L3. Accordingly, the ratio of the absolute value of the Abbe number of the third lens L3 to the absolute value of the Abbe number of the second lens L2 is greater than 1.5 and less than 3.0.

<Conditional Expression 3>

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

는 제5 렌즈(L5)의 상측면(9)에서 상면(IMG)까지의 거리이다. 여기에서, 물체면(OBJ)는 렌즈계(100)가 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(9) 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 9 of the fifth lens L5 to the image surface IMG. Here, the object plane OBJ is a part where the lens system 100 directly contacts the skin, and the image plane IMG is a part where an image is formed. Therefore, the ratio of the distance between the image surface (IMG) and the image side surface (9) of the fifth lens (L5) compared to the distance between the object surface (OBJ) and the object side surface (1) of the first lens (L1) is greater than 10.0 , Less than 20.0.

In addition, it is preferable that the angle of the principal ray incident on the image surface IMG is 0 degrees or more and less than 2 degrees based on the optical axis 105. This is because the size of the lens system can be minimized when an image is formed on the image surface IMG by allowing the principal rays to travel substantially parallel.

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 main ray angle is aligned almost horizontally with the optical axis, the size of the lens system does not need to be increased, and thus it can be applied as an objective lens for probes in an endoscope microscope.

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

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

Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Effective focal length 6.92 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 7.210 7.215 6.820 6.390 7.220 TTL 7.986 7.995 7.990 7.990 7.996

Here, the effective focal length is the focal length of the lens system, and the design wavelength is the design wavelength. In addition, NA(O) is NA (Numerical Aperture) on the object side, and NA(I) is NA on the image side. In addition, 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 from the center of the incident surface of the object surface to the center of the exit surface of the image surface. The surface number OBJ represents the surface of the object in which the lens system directly contacts the skin, and the surface number IMG represents the image surface on which the image is formed.

Surface numbers 1 and 2 denote an object-side surface and an image-side surface of the first lens L1, respectively. Surface number 3 is the object side surface of the second lens L2, and surface number 4 is the bonding surface of the second and third lenses L2 and L3, which is the image side surface of the second lens L2 and the third lens L3. The object side and surface number 5 denote the image side of the third lens L3. Surface numbers 6 and 7 denote an object-side surface and an image-side surface of the fourth lens L4, respectively. Surface numbers 8 and 9 denote an object-side surface and an image-side surface of the fifth lens L5, respectively.

Therefore, the OAL is the thickness, distance from surface numbers 1 to 8. In addition, the TTL is the thickness and distance from the surface number OBJ to 9.

In addition, the ASP of the radius of curvature represents an aspherical surface, and the unit of the distance in the 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 in the direction of the optical axis from the vertex of the lens,

Is the curvature at the apex of the lens (the reciprocal of the radius of curvature),

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

Is the conic constant. And,

,

,

,

,

Etc. are aspheric coefficients.

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

Referring to FIG. 2, the first and fifth lenses L1 and L5 are plano-convex lenses. Further, the abutting lens to which the second and third lenses L2 and L3 are joined is a convex lens in which the object side surface 3 is slightly convex. In addition, the fourth lens L4 is an aspherical lens having both surfaces aspheric.

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

Cotton number Radius of curvature Thickness, distance Refractive index (nd) Abbe number (Vd) OBJ -12.501 (ASP) 0.060 1.333 55.72 One Infinity 1.620 1.883 40.76 2 -1.100 0.620 - - 3 8.770 0.800 1.847 23.78 4 1.250 0.900 1.729 54.67 5 -2.450 0.100 - - 6 0.893(ASP) 1.240 1.492 57.47 7 0.411(ASP) 0.980 - - 8 1.050 0.950 1.620 36.35 9 Infinity 0.716 - - IMG Infinity 0.000 - -

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

Cotton number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 6 0.89 -0.28 -0.01 -0.01 - - 7 -0.39 -0.08 -0.82 - - -

3 and 4, MTF characteristics and Optical Distortion according to the first numerical embodiment are all within a satisfactory range. In FIG. 3, a solid line is a tangential direction, and a dotted line is a radial direction. FIG. 5 is a view showing a lens system for an endoscope probe through which light rays pass through an optical axis according to a second numerical example of the present invention. 6 is a diagram showing MTF characteristics according to the second numerical example 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 and fifth lenses L1 and L5 are plano-convex lenses. Further, the abutting lens to which the second and third lenses L2 and L3 are joined is a convex lens in which the object side surface 3 is slightly convex. In addition, the fourth lens L4 is an aspherical lens having both surfaces aspheric.

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

Cotton number Radius of curvature Thickness, distance Refractive index (nd) Abbe number (Vd) OBJ -12.501 (ASP) 0.060 1.333 55.72 One Infinity 1.620 1.883 40.76 2 -1.100 0.600 - - 3 15.330 0.800 1.847 23.78 4 1.290 1.000 1.729 54.67 5 -2.410 0.100 - - 6 0.955(ASP) 1.240 1.620 60.37 7 0.434(ASP) 0.905 - - 8 1.060 0.950 1.620 36.35 9 Infinity 0.720 - - IMG Infinity 0.000 - -

Table 5 below shows the coefficients for the aspherical surface of the lens system for an endoscope probe according to the second numerical example.

Cotton number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 6 -0.24 -0.9E-03 -0.6E-03 - - - 7 -0.28 -0.09 -0.75 - - -

6 and 7, MTF characteristics and Optical Distortion according to the second numerical example are all within a satisfactory range. FIG. 8 is a diagram showing a light ray passing through the optical axis according to the third numerical example of the present invention. It is a diagram showing a lens system for an endoscope probe. In addition, FIG. 9 is a diagram showing MTF characteristics according to the third numerical example of FIG. 8. And, FIG. 10 is a diagram showing distortion aberration according to the third numerical example of FIG. 8.

Referring to FIG. 8, the first and fifth lenses L1 and L5 are plano-convex lenses. Further, a contact lens joined by the second and third lenses L2 and L3 is a lens in which the object side surface 3 is slightly concave and the image side surface 5 is convex. In addition, the fourth lens L4 is a lens having an aspherical surface only on one surface of the object side surface 6.

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

Cotton number Radius of curvature Thickness, distance Refractive index (nd) Abbe number (Vd) OBJ -12.501 (ASP) 0.060 1.333 55.72 One Infinity 1.620 1.883 40.76 2 - -1.080 0.100 - - 3 -5.310 0.700 1.847 23.78 4 1.440 1.000 1.804 46.57 5 -2.790 0.100 - - 6 0.842 (ASP) 1.240 1.497 81.59 7 0.540 1.160 - - 8 1.260 0.900 1.640 60.21 9 Infinity 1.110 - - IMG Infinity 0.000 - -

Table 7 below shows the coefficients for the aspherical surface of the lens system for an endoscope probe according to the third numerical example.

Cotton number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 6 -0.37 -5.1E-03 -0.1E-02 - - -

9 and 10, both MTF characteristics and Optical Distortion according to the third numerical example are within a satisfactory range. FIG. 11 shows a light beam passing through the optical axis according to the fourth numerical example of the present invention. It is a diagram showing a lens system for an endoscope probe. In addition, FIG. 12 is a diagram showing MTF characteristics according to the fourth numerical example 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 and fifth lenses L1 and L5 are plano-convex lenses. Further, a contact lens joined by the second and third lenses L2 and L3 is a lens in which the object side surface 3 is slightly concave and the image side surface 5 is convex. In addition, the fourth lens L4 is a lens having an aspherical surface only on one surface of the object side surface 6.

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

Cotton number Radius of curvature Thickness, distance Refractive index (nd) Abbe number (Vd) OBJ -12.501 (ASP) 0.040 1.333 55.72 One Infinity 1.620 1.883 40.76 2 - -1.090 0.100 - - 3 -2.230 0.700 1.847 23.78 4 1.850 1.000 1.804 46.57 5 -2.110 0.100 - - 6 0.918(ASP) 1.240 1.497 81.59 7 0.660 0.730 - - 8 1.640 0.900 1.640 60.21 9 Infinity 1.560 - - IMG Infinity 0.000 - -

Table 9 below shows the coefficients for the aspherical surface of the lens system for an endoscope probe according to the fourth numerical example.

Cotton number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 6 -0.392 -0.008 -0.0015 - - -

12 and 13, MTF characteristics and Optical Distortion according to the fourth numerical example are all within a satisfactory range. FIG. 14 is a diagram illustrating that a light beam passes through an optical axis according to the fifth numerical example of the present invention. It is a diagram showing a lens system for an endoscope probe. Further, FIG. 15 is a diagram showing 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 and fifth lenses L1 and L5 are plano-convex lenses. In addition, a contact lens joined by the second and third lenses L2 and L3 is a lens having a flat object-side surface 3 and a convex image-side surface 5. In addition, the fourth lens L4 is a lens having an aspherical surface only on one surface of the object side surface 6.

Table 10 below shows specific data of each lens surface on the optical path according to the fifth numerical example.

Cotton number Radius of curvature Thickness, distance Refractive index (nd) Abbe number (Vd) OBJ -12.501 (ASP) 0.080 1.333 55.72 One Infinity 1.620 1.883 40.76 2 - -1.100 0.100 - - 3 Infinity 0.700 1.847 23.78 4 1.510 1.000 1.652 58.42 5 -2.170 0.100 - - 6 0.830(ASP) 1.240 1.497 81.59 7 0.500 1.560 - - 8 1.110 0.900 1.640 60.21 9 Infinity 0.696 - - IMG Infinity 0.000 - -

Table 11 below shows the coefficients for the aspherical surface of the lens system for an endoscope probe according to the fifth numerical example.

Cotton number

OBJ -1.80E+05 -5.24 1810 -4.03E+04 -1.04E+06 2.66E+07 6 -0.446 0.027 0.0057 0.0531 - -

15 and 16, both MTF characteristics and Optical Distortion are within a satisfactory range.

Tables 12 to 14 below show that the first to fifth embodiments satisfy the conditions of Conditional Formulas 1 to 3, respectively.

Conditional Expression 1 Embodiment 1 -1.100 1.05 0.955 Embodiment 2 -1.100 1.06 0.964 Embodiment 3 -1.080 1.26 1.167 Embodiment 4 -1.090 1.643 1.507 Embodiment 5 -1.10 1.11 1.009

Conditional Expression 2 Embodiment 1 23.78 54.67 2.299 Embodiment 2 23.78 54.67 2.299 Embodiment 3 23.78 46.57 1.960 Embodiment 4 23.78 46.57 1.960 Embodiment 5 23.78 58.42 2.460

Condition 3 Embodiment 1 0.060 0.716 11.93 Embodiment 2 0.060 0.720 12.00 Embodiment 3 0.060 1.110 18.50 Embodiment 4 0.040 1.560 39.00 Embodiment 5 0.080 0.696 8.70

By applying the lens system for the endoscope probe according to the embodiment of the present invention to the probe of the endoscope, it is possible to implement a microscopic endoscope with one aspherical lens while maintaining high resolution performance, and to achieve a reduction in cost and increase in productivity. 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 will be implemented in other specific forms without changing the technical spirit or essential features. You will understand that you can. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting.

L1: first lens
L2: second lens
L3: third lens
L4: fourth lens
L5: fifth lens

Claims (7)

A lens system for an endoscope probe comprising a plurality of lenses arranged from an object side to an image side,
A first lens having a flat object side and a convex image side;
A second lens having an image side to be bonded;
A third lens having an object side surface bonded to the second lens;
A fourth lens having at least one aspherical surface; And
It includes a fifth lens having a convex object side and a flat image side,
A lens system for an endoscope probe, wherein a ratio of the absolute value of the radius of curvature of the fifth lens to the absolute value of the radius of curvature of the first lens is 0.9 to 1.6. delete The method of claim 1,
A lens system for an endoscope probe, wherein a ratio of the Abbe number of the third lens to the Abbe number of the second lens is 1.9 to 2.5. The method of claim 1,
A lens system for an endoscope probe, wherein a ratio of a distance between an image surface and an image side surface of the fifth lens compared to a distance between an object surface and an object side surface of the first lens is 8.5-40.0. The method of claim 1,
A lens system for endoscope probes in which the angle of the chief ray incident on the image surface is 0 degrees or more and less than 2 degrees based on the optical axis. The method of claim 1,
The second and third lenses,
A lens system for an endoscope probe, wherein the object side surface of the third lens is convex when the image side surface of the second lens is concave, and the object side surface of the third lens is concave when the image side surface of the second lens is convex. The method of claim 1,
The fourth lens,
A lens system for an endoscope probe having the aspherical surface toward the object side.

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