CN207473186U - A Small Aperture Optical System Used in Endoscope - Google Patents

Abstract

The utility model relates to a small-aperture optical system for an endoscope. From the object plane to the image plane, a first lens (1), a filter (2), a fixed aperture (3), a second lens (4), a third lens (5), a fourth lens (6), and a chip protection glass (7) are sequentially arranged. The endoscope optical system satisfies the following relationships: 1<|fb/f|<1.8;0.7<|fa/f|<0.9;|f‑fw|<0.008;0.69<|R1+R2|/|R1‑R2|<1. The endoscope optical system of the utility model has a consistent optimal imaging object distance in the human body and in the air.

Description

A Small Aperture Optical System Used in Endoscope

【Technical field】

The utility model patent relates to a medical device, in particular to a small-diameter optical system for an endoscope.

【Background technique】

With the rapid development of science and technology, the medical industry has also made great progress, and the technology of using endoscope for inspection and using endoscope for minimally invasive surgery has gradually developed and matured. As an optical instrument, the endoscope can enter the body through the natural channel of the human body to image the lesion, and can directly observe the lesion in the organ. At present, most endoscopes have large calibers, and the process of entering the human body is relatively painful, and it is not convenient to inspect the lesion with narrow channels; The range is very short, which greatly reduces the detection effect of the endoscope

Because there is above-mentioned problem, it is necessary to propose solution to it, and the utility model just makes under such background.

【Content of utility model】

The technical problem to be solved by the utility model is to provide a small-diameter optical system for endoscopes for the above-mentioned deficiencies in the prior art, and the diameter of the endoscope lens using this optical system can be reduced to 2.0mm, which just It means that the pain of patient examination can be greatly reduced. At the same time, the object distance range of the endoscope optical system of the utility model can be clearly imaged is 5-60 mm, which can be applied to the lesion inspection of a large cavity. In addition, the utility model's internal The scope optical system has the same optimal imaging object distance in the human body and in air.

In order to achieve the above object, the utility model adopts the following technical solutions:

A small-aperture optical system for endoscopes, including a front group G1 composed of a first lens 1, a rear group G2 composed of three lenses, a filter near the front group, and a fixed diaphragm near the rear group And chip protection glass, wherein the rear group includes the second lens 4, the third lens 5 and the fourth lens 6 arranged in sequence from the object plane side to the image plane side, when the endoscope optical system works in the air, its front group The equivalent focal length is fb, the equivalent focal length of the rear group is fa, and the total equivalent focal length is f; the endoscope optical system is inside the human body (the "inside the human body" mentioned below refers to human organs or organs with interstitial fluid) When working in the cavity), the total equivalent focal length is fw; R1 is the radius of curvature of the object side of the first lens, and R2 is the radius of curvature of the image side of the first lens. The endoscope optical system satisfies the following relationship:

1<|fb/f|<1.8 (1)

0.7<|fa/f|<0.9 (2)

|f-fw|<0.008 (3)

0.69<|R1+R2|/|R1-R2|<1 (4)

The first lens 1 of above-mentioned endoscopic optical system is a negative lens, and its image plane side is a concave surface, the second lens 4 is a positive lens, and its image plane side is a convex surface, and the third lens 5 is a positive lens, and its image plane side is Convex, the fourth lens 6 is a negative lens, the object plane side of which is concave; at least three of them are plastic aspheric lenses.

In order to control the aperture of the endoscope optical system while widening the angle of view, the power of the first lens is negative, and the image side is concave.

During the production process of medical endoscopes, the image quality evaluation is generally carried out in the air environment, but the actual use environment is in the human body. Due to the different refractive index of the object space in the two media, the optical quality of many endoscopes in the air is different. There is a big difference between the parameters and the optical parameters of the actual working environment. The object side of the first lens of the endoscope optical system is made into a slightly concave shape, which reduces the influence of the difference in the refractive index of the object space medium on the total focal length of the system, thereby ensuring that the endoscope optical system has a similar equivalent in the air and in the human body. The focal length ensures that the endoscope optical system has the same optimal imaging object distance in the air and the human body, and ensures the consistent depth of field effect in the air and the human body.

By satisfying the relational expression (4), it is ensured that during operation, dirt will not gather on the surface of the first lens because the object side of the first lens is too concave, resulting in unclear image quality when the endoscope works in the human body.

The above-mentioned endoscope optical system makes full use of the large gap between the first lens and the fixed diaphragm, and places the flat filter IR between the first lens and the fixed diaphragm, effectively reducing the total length of the optical system; on the other hand, Arranging flat glass between the first lens and the fixed diaphragm can effectively reduce the light height of the external field of view, which is beneficial to the reduction of the aperture of the endoscope optical system.

The above-mentioned endoscope optical system satisfies the following relationship:

1<CTo/TTL<6 (5)

Wherein, CTo is the optimal imaging object distance of the optical system; TTL is the axial distance from the object side of the first lens of the endoscope optical system to the imaging plane.

The object distance of the above-mentioned endoscope optical system is finite, and the formula (5) is mainly to balance the resolution of the near view and the distant view of the above-mentioned endoscope optical system. When the optimal imaging object distance of the optical system is lower than the lower limit, the resolution of the distant view When the optimal imaging object distance of the optical system exceeds the upper limit, the resolution of the close-up becomes worse.

The above-mentioned endoscope optical system satisfies the following relationship:

30<|Vd3-Vd4|<50 (6)

Wherein, Vd3 is the Abbe number of the third lens of the optical system; Vd4 is the Abbe number of the fourth lens of the optical system.

The chromatic aberration of magnification is corrected by reasonably selecting the materials of the third lens and the fourth lens. When the difference between the Abbe numbers of the two lenses is lower than the lower limit or exceeds the upper limit, the chromatic aberration of magnification is large, and color smear will appear on the screen.

The above-mentioned endoscope optical system satisfies the following relationship:

1.5<TTL/ImgH<3.5 (7)

Wherein, TTL is the axial distance from the object side of the first lens of the optical system to the imaging plane; ImgH is the maximum image height of the optical system.

When the relational expression (7) is lower than the lower limit, it is difficult to limit the aperture while ensuring the image quality of the endoscope optical system. When the relational expression (7) exceeds the upper limit, the total length of the endoscope optical system will be too long. It is not conducive to the miniaturization of the endoscope.

The above-mentioned endoscope optical system satisfies the following relationship when working in the air:

0.5<T12/f<0.9 (8)

0.04<Tst2/f<0.06 (9)

0.4<T4i/f<1.2 (10)

Wherein, T12 is the on-axis distance between the image side of the first lens of the optical system and the object side of the second lens; Tst2 is the on-axis distance from the fixed diaphragm of the optical system to the object side of the second lens; T4i is the fourth The axial distance from the image side of the lens to the image plane.

Equations (8) and (9) jointly balance the front and rear structures of the fixed diaphragm, which is beneficial to correct the astigmatism and distortion of the endoscope optical system, and also contributes to the correction of chromatic aberration of magnification. Equation (10) mainly controls the back focal length of the endoscope optical system. When T4i/f is lower than the lower limit, the focusing space of the endoscope lens will not be enough. When T4i/f exceeds the upper limit, it will lead to The total length of the entire optical system is too long.

The above-mentioned endoscope optical system satisfies the following relationship:

0.11<CT1/∑CT<0.17 (11)

0.17<CT2/∑CT<0.3 (12)

0.18<CT3/∑CT<0.36 (13)

0.19<CT4/∑CT<0.41 (14)

Among them, ΣCT is the total thickness of the first lens, second lens, third lens, and fourth lens of the optical system on the optical axis; CT1 is the thickness of the first lens of the optical system on the optical axis, and CT2 is the thickness of the first lens of the optical system. The thickness of the second lens of the optical system on the optical axis, CT3 is the thickness of the third lens of the optical system on the optical axis, and CT4 is the thickness of the fourth lens of the optical system on the optical axis.

When CT1/∑CT is the lower limit, the center of the concave lens becomes thinner. On the one hand, the surface accuracy will be relatively poor during the injection molding process. On the other hand, the strength of the lens will decrease, and it will not be resistant to collisions and drops; When CT is the upper limit, the light height will increase, and the lens aperture will also increase accordingly.

Formulas (13) and (14) mainly correct chromatic aberration of magnification and axial chromatic aberration. In addition, the image side of the third lens is convex, and the object side of the fourth lens is concave, which is beneficial to suppress the astigmatism of the endoscope optical system and spherical aberration correction.

The above-mentioned endoscope optical system satisfies the following relationship when working in the air:

0.61<|f2/f|<1.03 (15)

0.82<|f3/f|<1.72 (16)

0.69<|f4/f|<1.2 (17)

Wherein, f2 is the equivalent focal length of the second lens; f3 is the equivalent focal length of the third lens; f4 is the equivalent focal length of the fourth lens.

Both the second lens and the third lens are positive lenses. The use of two adjacent positive lenses can effectively correct spherical aberration and distortion. In addition, the reasonable distribution of the focal power of the third lens and the fourth lens can easily correct endoscopy. Magnification chromatic aberration and axial chromatic aberration of the mirror optical system.

The above-mentioned endoscope optical system satisfies the following relationship:

35<FNO·ImgH/βw<102 (18)

45<FNO·ImgH/β<125 (19)

Among them, FNO is the aperture value of the optical system; βw is the vertical axis magnification of the optical system placed in the human body; β is the vertical axis magnification of the optical system placed in the air.

When the relational expressions (18) and (19) are lower than the lower limit, the depth of field of the endoscope optical system will become worse, and when the relational expressions (18) and (19) exceed the upper limit, the depth of field of the endoscope optical system The vertical magnification will be too small, which is not conducive to finding tiny lesions during use.

The above-mentioned endoscope optical system satisfies the following relationship:

0.73<f tan(ω/2)/ImgH<1.16 (20)

0.28<fw tan(ωw/2)/ImgH<0.60 (21)

Among them, ω is the maximum viewing angle of the optical system placed in the air; fw is the total equivalent focal length of the optical system placed in the human body; ωw water is the maximum viewing angle of the optical system placed in the human body.

When the relational expressions (20) and (21) are lower than the lower limit, it will be unfavorable for the wide angle of the endoscope optical system. When the relational expressions (20) and (21) exceed the upper limit, the endoscope optical system The distortion is larger.

The beneficial effects of the utility model are:

1. The endoscope optical system of the utility model has a large field of view, and more than three of the four lenses are plastic lenses, so the cost is low, and can be widely used in disposable medical endoscopes. The endoscope optical The tolerance sensitivity of the endoscope objective lens constituted by the system is low, and it can be assembled with a simple metal lens barrel without steps and threads, which effectively reduces the lens aperture and improves the versatility of the lens. In addition, the endoscope optical system is in the The working focal length in the air and the human body has little change, and it can image clearly in a long range of object distance.

【Description of drawings】

FIG. 1 is a lens cross-sectional view of the overall structure of an endoscope optical system according to an embodiment of the present invention.

2 is a lens cross-sectional view of the overall structure of the endoscope optical system according to Embodiment 1 of the present invention.

FIG. 3 is an aberration graph of the endoscope optical system of FIG. 2 in air.

FIG. 4 is a graph showing aberrations of the endoscope optical system in FIG. 2 in a human body.

5 is a lens cross-sectional view of the overall structure of the endoscope optical system according to Embodiment 2 of the present invention.

FIG. 6 is an aberration graph of the endoscope optical system of FIG. 5 in air.

FIG. 7 is an aberration graph of the endoscope optical system in FIG. 5 in a human body.

8 is a lens cross-sectional view of the overall structure of the endoscope optical system according to Embodiment 3 of the present invention.

FIG. 9 is an aberration graph of the endoscope optical system of FIG. 8 in air.

FIG. 10 is an aberration graph of the endoscope optical system of FIG. 8 in a human body.

11 is a lens cross-sectional view of the overall structure of the endoscope optical system according to Embodiment 4 of the present invention.

FIG. 12 is an aberration graph of the endoscope optical system of FIG. 11 in air.

FIG. 13 is an aberration graph of the endoscope optical system of FIG. 11 in a human body.

【Detailed ways】

Below in conjunction with accompanying drawing, the utility model is described in further detail.

As shown in Figures 1 to 13, a small-aperture optical system for endoscopes is provided with a first lens 1, a filter 2, a second lens 4, and a third lens 5 in sequence from the object plane to the image plane. , the fourth lens 6, the grating 6, the chip protection glass 7, the first lens 1 constitutes the optical front group G1, the second lens 4, the third lens 5, and the fourth lens 6 constitute the optical rear group G2, and the endoscopic When the mirror optical system works in the air, the equivalent focal length of the optical front group G1 is fb, the equivalent focal length of the optical rear group G2 is fa, and the total equivalent focal length of the endoscope optical system is f; When working in vivo, the total equivalent focal length of the endoscopic optical system is fw; R1 is the object side curvature radius of the first lens 1, R2 is the image side curvature radius of the first lens 1, and the endoscopic optical system Satisfy the following relationship:

1<|fb/f|<1.8

0.7<|fa/f|<0.9

|f-fw|<0.008

0.69<|R1+R2|/|R1-R2|<1

The endoscope optical system formed according to the above conditions can be given appropriate focal length distribution from the first lens to the fourth lens, and can constitute a small-aperture optical system for endoscopes in which the optimal object distance in the human body and in the air are consistent. Moreover, the endoscope optical system can clearly image a wide range of object distances, and the endoscope camera system composed of the endoscope optical system can capture more lesion information. The endoscope optical system of the utility model has a large field of view angle, and more than three of the four lenses are plastic lenses, so the cost is low, and can be widely used in disposable medical endoscopes. The endoscope optical system consists of The tolerance sensitivity of the endoscope objective lens is low, and it can be assembled with a simple metal lens barrel without steps and threads, which effectively reduces the lens diameter and improves the versatility of the lens. In addition, the endoscope optical system is in the air and The working focal length in the human body changes little, and images can be clearly imaged within a longer object distance range.

As shown in Figures 1 and 2, in this embodiment, the first lens 1 is a negative lens with a concave image side, and the second lens 4 is a positive lens with a convex image side, so The third lens 5 is a positive lens, and its image plane side is a convex surface, and the fourth lens 6 is a negative lens, and its object plane side is a concave surface. The first lens 1, the second lens 4, the third lens 5, At least three of the fourth lenses 6 are plastic aspherical lenses.

As shown in Figures 1 and 2, in this embodiment, the endoscope optical system satisfies the following relational expression:

1<CTo/TTL<6

Wherein, CTo is the object distance of the endoscope optical system; TTL is the axial distance from the object side of the first lens of the endoscope optical system to the imaging plane.

As shown in Figures 1 and 2, in this embodiment, the endoscope optical system satisfies the following relational expression:

30<|Vd3-Vd4|<50

Wherein, Vd3 is the Abbe number of the third lens 5 of the endoscope optical system; Vd4 is the Abbe number of the fourth lens 6 of the endoscope optical system.

As shown in Figures 1 and 2, in this embodiment, the endoscope optical system satisfies the following relational expression:

1.5<TTL/ImgH<3.5

Wherein, TTL is the axial distance from the object side of the first lens 1 of the endoscope optical system to the imaging plane; ImgH is the maximum image height of the endoscope optical system.

As shown in Figure 1 and Figure 2, in this embodiment, the endoscope optical system satisfies the following relation when working in the air:

0.5<T12/f<0.9

0.04<Tst2/f<0.06

0.4<T4i/f<1.2

Among them, T12 is the axial separation distance between the first lens image side and the second lens object side of the endoscope optical system; Tst2 is the axial distance from the fixed diaphragm of the endoscope optical system to the second lens object side; T4i is the inner The on-axis distance from the image side to the image plane of the fourth lens of the scope optical system.

As shown in Figures 1 and 2, in this embodiment, the endoscope optical system satisfies the following relational expression:

0.11<CT1/∑CT<0.17

0.17<CT2/∑CT<0.3

0.18<CT3/∑CT<0.36

0.19<CT4/∑CT<0.41

Among them, ΣCT is the sum of the thicknesses of the first lens 1, the second lens 4, the third lens 5, and the fourth lens 6 on the optical axis of the endoscopic optical system; CT1 is the first lens 1 of the endoscopic optical system. The thickness of a lens 1 on the optical axis, CT2 is the thickness on the optical axis of the second lens 4 of the endoscope optical system, and CT3 is the thickness of the third lens 5 on the optical axis of the endoscope optical system, CT4 is the thickness of the fourth lens 6 on the optical axis of the endoscope optical system.

As shown in Figure 1 and Figure 2, in this embodiment, the endoscope optical system satisfies the following relation when working in the air:

0.61<|f2/f|<1.03

0.82<|f3/f|<1.72

0.69<|f4/f|<1.2

Wherein, f2 is the equivalent focal length of the second lens 4 ; f3 is the equivalent focal length of the third lens 5 ; f4 is the equivalent focal length of the fourth lens 6 .

As shown in Figures 1 and 2, in this embodiment, the endoscope optical system satisfies the following relational expression:

35<FNO·ImgH/βw<102

45<FNO·ImgH/β<125

Among them, FNO is the aperture value of the endoscope optical system; βw is the vertical axis magnification of the endoscope optical system placed in the human body; β is the vertical axis magnification of the endoscope optical system placed in air.

As shown in Figures 1 and 2, in this embodiment, the endoscope optical system satisfies the following relational expression:

0.73<f tan(ω/2)/ImgH<1.16

0.28<fw tan(ωw/2)/ImgH<0.60

Among them, ω is the maximum viewing angle of the endoscope optical system placed in the air; fw is the total equivalent focal length of the endoscope optical system placed in the human body; ωw is the maximum viewing angle of the endoscope optical system placed in the human body field angle.

The four embodiments of the endoscope optical system are described below with reference to FIGS. 656nm, 587nm, 486nm, where the left side of the aberration diagram is the axial spherical aberration diagram, the middle one is the astigmatism diagram, and the right one is the distortion diagram, and the S (solid line) and T (dotted line) in the astigmatism diagram represent the sagittal image plane and the meridional image plane, respectively.

Example 1:

The structure of the endoscope optical system of Embodiment 1 of the present utility model is shown in Fig. 2, and the aberration curve of the endoscope optical system of Embodiment 1 of the present utility model in air is shown in Fig. 3, in The aberration curve in the human body is shown in Fig. 4 .

Table 1 is the lens data table of Embodiment 1 of the endoscope optical system.

Table 1

Table 2 shows the range of the ratio of the aspheric sagittal height to the radius R of the first lens 1 and the second lens 4 in Embodiment 1 of the endoscope optical system.

Table 2

Table 3 shows the range of the ratio of the aspheric sagittal height to the radius R of the third lens 5 and the fourth lens 6 in Embodiment 1 of the endoscopic optical system.

table 3

Example 2:

The structure of the endoscope optical system of embodiment 2 of the present utility model is shown in Fig. 5, and the aberration curve of the endoscope optical system of embodiment 2 of the present utility model in air is shown in Fig. 6, in The aberration curve in the human body is shown in FIG. 7 .

Table 4 is the lens data table of Embodiment 2 of the endoscope optical system.

Table 4

Table 5 shows the range of the ratio of the aspheric sagittal height to the radius R of the first lens 1 and the second lens 4 of the second embodiment of the endoscopic optical system.

table 5

Table 6 shows the ratio range of the aspherical sagittal height to the radius R of the third lens 5 and the fourth lens 6 of the second embodiment of the endoscope optical system.

Table 6

Example 3:

The structure of the endoscope optical system of Embodiment 3 of the present invention is shown in FIG. 8 , and the aberration curve of the endoscope optical system of Embodiment 3 of the present invention in air is shown in FIG. 9 . The aberration curve in the human body is shown in FIG. 10 .

Table 7 is the lens data table of Embodiment 3 of the endoscope optical system.

Table 7

Table 8 shows the range of the ratio of the aspheric sagittal height to the radius R of the first lens 1 and the second lens 4 of the third embodiment of the endoscopic optical system.

Table 8

Table 9 shows the ratio range of the aspherical sagittal height to the radius R of the third lens 5 and the fourth lens 6 of the third embodiment of the endoscope optical system.

Table 9

Example 4:

The structure of the endoscope optical system of Embodiment 4 of the present invention is shown in FIG. 11 , and the aberration curve of the endoscope optical system of Embodiment 4 of the present invention in air is shown in FIG. 12 . The aberration curve in the human body is shown in FIG. 13 .

Table 10 is the lens data table of Embodiment 4 of the endoscope optical system.

Table 10

Table 11 shows the ratio range of the aspherical sagittal height to the radius R of the first lens 1 and the second lens 4 of Embodiment 4 of the endoscope optical system.

Table 11

Table 12 shows the range of the ratio of the aspheric sagittal height to the radius R of the third lens 5 and the fourth lens 6 in Embodiment 4 of the endoscope optical system.

Table 12

Claims (10)

1. A small aperture optical system for endoscope, characterized in that: first lens (1), optical filter (2), fixed diaphragm (3), first lens (1) are arranged successively from object plane to image plane Two lenses (4), a third lens (5), a fourth lens (6), a chip protection glass (7), the first lens (1) constitutes an optical front group G1, the second lens (4), The third lens (5) and the fourth lens (6) form the optical rear group G2. When the endoscope optical system works in the air, the equivalent focal length of the optical front group G1 is fb, and the equivalent focal length of the optical rear group G2 is fa , the total equivalent focal length of the endoscope optical system is f; when the endoscope optical system works in the human body, the total equivalent focal length of the endoscope optical system is fw; R1 is the object of the first lens (1) Side curvature radius, R2 is the image side curvature radius of the first lens (1), and the endoscopic optical system satisfies the following relationship: 1<|fb/f|<1.8 0.7<|fa/f|<0.9 |f-fw|<0.008 0.69<|R1+R2|/|R1-R2|<1. 2. The small-aperture optical system for endoscope according to claim 1, characterized in that: the first lens (1) is a negative lens, and its image side is concave, and the second lens (4) ) is a positive lens whose image side is convex, the third lens (5) is a positive lens whose image side is convex, and the fourth lens (6) is a negative lens whose object side is concave, At least three of the first lens (1), second lens (4), third lens (5) and fourth lens (6) are plastic aspherical lenses. 3. The small-diameter optical system for endoscope according to claim 1 or 2, wherein the endoscope optical system satisfies the following relational expression: 1<CTo/TTL<6 Wherein, CTo is the object distance of the endoscope optical system; TTL is the axial distance from the object side of the first lens (1) of the endoscope optical system to the imaging plane. 4. The small-diameter optical system for endoscope according to claim 1 or 2, characterized in that: the endoscope optical system satisfies the following relational expression: 30<|Vd3-Vd4|<50 Wherein, Vd3 is the Abbe number of the third lens (5) of the endoscope optical system; Vd4 is the Abbe number of the fourth lens (6) of the endoscope optical system. 5. The small-diameter optical system for endoscope according to claim 1 or 2, characterized in that: the endoscope optical system satisfies the following relational expression: 1.5<TTL/ImgH<3.5 Wherein, TTL is the axial distance from the object side of the first lens (1) of the endoscope optical system to the imaging plane; ImgH is the maximum image height of the endoscope optical system. 6. The small-diameter optical system for endoscope according to claim 1 or 2, wherein the endoscope optical system satisfies the following relational expression when working in air: 0.5<T12/f<0.9 0.04<Tst2/f<0.06 0.4<T4i/f<1.2 Wherein, T12 is the on-axis separation distance between the image side of the first lens (1) of the endoscope optical system and the object side of the second lens (4); Tst2 is the fixed diaphragm (3) to the second lens (3) of the endoscope optical system 4) On-axis distance of the object side; T4i is the on-axis distance from the image side of the fourth lens (6) of the endoscope optical system to the image plane. 7. The small-aperture optical system for endoscope according to claim 1 or 2, characterized in that: the endoscope optical system satisfies the following relational expression: 0.11<CT1/∑CT<0.17 0.17<CT2/∑CT<0.3 0.18<CT3/∑CT<0.36 0.19<CT4/∑CT<0.41 Wherein, ΣCT is the thickness summation of the first lens (1), the second lens (4), the third lens (5) and the fourth lens (6) respectively on the optical axis of the endoscopic optical system; CT1 is The thickness of the first lens (1) of the endoscope optical system on the optical axis, CT2 is the thickness of the second lens (4) of the endoscope optical system on the optical axis, CT3 is the thickness of the endoscope optical system The thickness of the third lens (5) on the optical axis, CT4 is the thickness of the fourth lens (6) of the endoscope optical system on the optical axis. 8. The small-aperture optical system for endoscope according to claim 1 or 2, characterized in that: the endoscope optical system satisfies the following relational expression when working in air: 0.61<|f2/f|<1.03 0.82<|f3/f|<1.72 0.69<|f4/f|<1.2 Wherein, f2 is the equivalent focal length of the second lens (4); f3 is the equivalent focal length of the third lens (5); f4 is the equivalent focal length of the fourth lens (6). 9. The small-aperture optical system for endoscope according to claim 1 or 2, characterized in that: the endoscope optical system satisfies the following relational expression: 35<FNO·ImgH/βw<102 45<FNO·ImgH/β<125 Among them, FNO is the aperture value of the endoscope optical system; βw is the vertical axis magnification of the endoscope optical system placed in the human body; β is the vertical axis magnification of the endoscope optical system placed in air. 10. The small-aperture optical system for endoscope according to claim 1 or 2, characterized in that: the endoscope optical system satisfies the following relational expression: 0.73<f tan(ω/2)/ImgH<1.16 0.28<fw tan(ωw/2)/ImgH<0.60 Among them, ω is the maximum viewing angle of the endoscope optical system placed in the air; fw is the total equivalent focal length of the endoscope optical system placed in the human body; ωw is the maximum viewing angle of the endoscope optical system placed in the human body field angle.