An ultra-long endoscope

Abstract

This invention proposes an ultra-long endoscope, belonging to the field of endoscopy. It solves the problem that existing endoscopes cannot guarantee image quality while meeting length requirements by combining an ultra-long objective lens with an ultra-long relay system. The objective lens includes a biconcave lens, a first Hopkins rod lens, a first cemented doublet lens group, a second cemented doublet lens group, and a single lens, arranged sequentially along the light incident direction. The relay system includes an odd number of optical image-shifting lens groups arranged sequentially along the optical axis. Each optical image-shifting lens group includes two symmetrical optical glass lens groups, each comprising a separately arranged third Hopkins rod lens, a fourth Hopkins rod lens, and a cemented doublet lens group. The cemented doublet lens group includes a cemented positive lens and a second negative lens. This design can meet the endoscope's working length requirements while reducing the cumulative effect of axial aberrations caused by unit stacking.

Description

Technical Field

[0001] This invention belongs to the field of endoscopy technology, and in particular relates to an ultra-long endoscope. Background Technology

[0002] Endoscopic optical systems are used to acquire high-resolution images, helping doctors observe the internal conditions of the human body. These systems must ensure clear imaging while also being adaptable to confined spaces and small dimensions. The optical system includes an objective lens system, a relay system, an eyepiece system, and an optical adapter. The objective lens system is used to acquire images, the relay system is used to transmit images and control the overall length of the endoscopic optical system to adapt to different medical scenarios, and the eyepiece system is used for magnified observation.

[0003] Medical endoscopes have strict requirements for working length. Traditional endoscope objectives are generally short, with relay systems handling image transmission to achieve the required working length. Each image transmission group in the relay system has axial aberrations. When multiple image transmission groups are installed together, the multiplication effect of axial aberrations such as field curvature and astigmatism becomes more significant, resulting in a decrease in the overall image quality of the combined system. The manufacturing process of rod endoscopes requires an aspect ratio ≥1:7, which strictly limits the length of a single rod endoscope. This creates a core contradiction: traditional single-unit image transmission systems are limited by the single rod endoscope length threshold. To maintain the aspect ratio specification, multiple image transmission units need to be connected in series to achieve the target length, but the stacking of units will cause a cumulative effect of axial aberrations. Currently, existing medical endoscopes generally cannot achieve the target working length using only an objective lens and a single optical image-transfer lens group. Summary of the Invention

[0004] In view of this, in order to solve the problem that existing medical endoscopes cannot achieve the target working length by using only an objective lens and a single optical image-rotating lens group, this invention proposes an ultra-long endoscope.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An ultra-long endoscope, comprising:

[0007] The objective lens includes a biconcave structure lens, a first Hopkins rod lens, an aperture, a first cemented doublet lens group, a second cemented doublet lens group, and a single lens arranged sequentially along the incident direction of light. The first cemented doublet lens group includes a first lens and a second lens cemented together and fixed. The second cemented doublet lens group includes a second Hopkins rod lens and a first negative lens cemented together and fixed.

[0008] The relay system includes an odd number of optical image-spinning lens groups arranged sequentially along the optical axis. Each optical image-spinning lens group includes two symmetrically arranged optical glass lens groups with an aperture stop between them, forming a 1:1 dual telecentric image-spinning system. Each optical glass lens group includes a third Hopkins rod lens, a fourth Hopkins rod lens, and a third cemented doublet lens group, which are separately arranged. The third cemented doublet lens group includes a positive lens and a second negative lens that are cemented together. The third Hopkins rod lens, the fourth Hopkins rod lens, the positive lens, and the second negative lens are arranged sequentially along the incident light direction.

[0009] As a preferred embodiment of the aforementioned ultralong endoscope, the first Hopkins rod lens has convex surfaces on both sides; in the first cemented doublet lens group, the end face of the first lens near the object side is convex and the end face near the image side is concave, and both end faces of the second lens are convex; in the second cemented doublet lens group, the end face of the second Hopkins rod lens near the object side is concave and the end face near the image side is convex, and both end faces of the first negative lens are concave; both end faces of the single lens are convex.

[0010] As a preferred embodiment of the aforementioned ultralong endoscope, the relationship between half the height of the objective image (IH) and the focal length (f) of the objective lens is 0.6 ≤ IH / f ≤ 0.7; the relationship between half the height of the objective image (IH) and the distance (TTL) on the optical axis from the object side surface of the biconcave lens to the imaging surface of the objective lens is 0.015 ≤ IH / TTL ≤ 0.03; the relationship between the center thickness (d1) of the first Hopkins rod lens and the focal length (f) of the objective lens is 8 ≤ d1 / f ≤ 15; the relationship between the center thickness (d2) of the second Hopkins rod lens and the focal length (f) of the objective lens is 8 ≤ d2 / f ≤ 13; and the effective focal length (f) of the biconcave lens... L1 The relationship with the focal length f of the objective lens is 0.8 ≤ |f L1 / f|≤1.2; The relationship between the effective focal length of the first Hopkins rod lens and the focal length f of the objective lens is 6≤|f L2 / f|≤9;The overall effective focal length f of the first cemented doublet lens group 34 The relationship with the focal length f of the objective lens is 2.2 ≤ |f 34 / f|≤3.8; the overall effective focal length f of the second cemented doublet lens group 56 The relationship between the objective lens and its focal length f is 1 ≤ |f 56 / f|≤2; Effective focal length f of a single lens L7 The relationship with the focal length f of the objective lens is 3.5 ≤ |f L7 / f|≤5.0; The relationship between the aperture number FNO of the objective lens and the distance TTL from the object side of the biconcave lens to the imaging plane of the objective lens on the optical axis is 0.08≤FNO / TTL≤0.12; The range of the working distance L of the objective lens is 3≤L≤8.

[0011] As a preferred embodiment of the aforementioned ultralong endoscope, the distance between the biconcave lens and the first Hopkins rod lens is 0.2mm to 8.0mm; the distance between the first Hopkins rod lens and the first cemented doublet lens group is 0.8mm to 8.0mm; the distance between the first cemented doublet lens group and the second cemented doublet lens group is 0.2mm to 0.4mm; and the distance between the second cemented doublet lens group and the single lens is 0.3mm to 0.5mm.

[0012] As a preferred embodiment of the aforementioned ultra-long endoscope, both sides of the third Hopkins rod lens are convex, the end face of the fourth Hopkins rod lens near the object side is concave, and the end face near the image side is convex. The surfaces of the positive lens and the second negative lens that are close to each other are cemented surfaces, which are flat.

[0013] As a preferred embodiment of the aforementioned ultra-long endoscope, the radius of curvature of the end face of the third Hopkins rod lens near the object side ranges from 20mm to 40mm, and the radius of curvature of the end face near the image side ranges from -80mm to -400mm; the radius of curvature of the end face of the fourth Hopkins rod lens near the object side ranges from -80mm to -400mm, and the radius of curvature of the end face near the image side ranges from -30mm to -60mm; the radius of curvature of the end face of the positive lens near the object side ranges from 4mm to 8mm; and the radius of curvature of the end face of the second negative lens near the image side ranges from 3mm to 8mm.

[0014] As a preferred embodiment of the aforementioned ultralong endoscope, the thickness range of the third and fourth Hopkins rod lenses is 20mm to 40mm, the thickness range of the positive lens is 0.5mm to 2.5mm, and the thickness range of the second negative lens is 0.5mm to 2mm.

[0015] As a preferred embodiment of the aforementioned ultralong endoscope, the refractive index of the material of the third Hopkins rod lens ranges from 1.72 to 2.20, the refractive index of the material of the fourth Hopkins rod lens ranges from 1.65 to 2.10, the refractive index of the material of the positive lens ranges from 1.44 to 1.80, and the refractive index of the material of the second negative lens ranges from 1.44 to 1.80.

[0016] As a preferred embodiment of the aforementioned ultralong endoscope, the material of the third Hopkins rod lens is H-ZLAF96; the material of the fourth Hopkins rod lens is H-ZLAF89L or H-ZLAF89LA; the material of the positive lens is H-LAK52, H-LAK11 or H-LAK7A; and the material of the second negative lens is F1 or F4.

[0017] As a preferred embodiment of the aforementioned ultra-long endoscope, the total length of the objective lens and a set of optical image-rotating lenses is 200mm to 240mm within a 3.8mm aperture.

[0018] Compared with existing technologies, the beneficial effects of the ultra-long endoscope provided by this invention are:

[0019] This invention provides an ultralong endoscope. The objective lens includes a biconcave lens, a first Hopkins rod lens, a first cemented doublet lens group, a second cemented doublet lens group, and a single lens, arranged sequentially along the light incident direction. The first cemented doublet lens group includes a first lens and a second lens cemented together. The second cemented doublet lens group includes a second Hopkins rod lens and a first negative lens cemented together. The first lens of the objective lens, facing the object being observed, is a biconcave lens, which increases the negative optical power of the first lens, thereby satisfying a larger field of view. The optical image-rotating lens group consists of two separate optical glass lens groups arranged symmetrically, with an aperture stop between them, forming a 1:1 dual telecentric image-rotating system. Each optical glass lens group has two Hopkins rods, designated as the third and fourth Hopkins rods, thus each optical image-transfer lens group has four Hopkins rods. The length of each optical image-transfer lens group is equivalent to the length of three traditional optical image-transfer lens groups. The length of the three optical image-transfer lens groups in this invention is sufficient to replace the length of five traditional optical image-transfer lens groups, significantly improving image quality, reducing unit stacking, and enabling ultra-long working lengths. The number of optical image-transfer lens groups used is selected as needed. By combining an ultra-long objective lens with an ultra-long relay system, the problem of existing endoscopes being unable to guarantee image quality while meeting length requirements is solved. Therefore, this ultra-long endoscope can guarantee image quality while meeting the design target working length, and also makes the designed objective lens as easy to manufacture and assemble as a Hopkins lens. Attached Figure Description

[0020] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0021] Figure 1 This is a schematic diagram of the structure of the ultra-long endoscope provided in Embodiment 1 of the present invention;

[0022] Figure 2 This is a schematic diagram of the structure of the ultra-long endoscope provided in Embodiment 2 of the present invention;

[0023] Figure 3This is a schematic diagram of the objective lens of the ultra-long endoscope provided in Embodiment 1 of the present invention;

[0024] Figure 4 This is a schematic diagram of the objective lens of the ultra-long endoscope provided in Embodiment 2 of the present invention;

[0025] Figure 5 This is a schematic diagram of the optical image-rotating lens group of the ultra-long endoscope provided in Embodiment 1 of the present invention;

[0026] Figure 6 This is a schematic diagram of the optical image-rotating lens group of the ultra-long endoscope provided in Embodiment 2 of the present invention;

[0027] Figure 7 This is a modulation transfer function (MTF) curve of Example 1 at a cutoff frequency of 100 lp / mm;

[0028] Figure 8 This is the modulation transfer function (MTF) curve of Example 2 at a cutoff frequency of 100 lp / mm.

[0029] In the picture:

[0030] 1. Third Hopkins bar lens; 2. Fourth Hopkins bar lens; 3. Positive lens; 4. Second negative lens; 5. Biconcave lens; 6. First Hopkins bar lens; 7. First lens; 8. Second lens; 9. Second Hopkins bar lens; 10. First negative lens; 11. Single lens. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0032] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0035] See Figure 1-8 This invention provides an ultra-long endoscope, which includes an objective lens and a relay system. The objective lens includes a biconcave lens 5, a first Hopkins rod lens 6, a first cemented doublet lens group, a second cemented doublet lens group, and a single lens 11 arranged sequentially along the light incident direction. An aperture is provided between the first Hopkins rod lens 6 and the first cemented doublet lens group. The first cemented doublet lens group includes a first lens 7 and a second lens 8 cemented together. The second cemented doublet lens group includes a second Hopkins rod lens 9 and a first negative lens 10 cemented together. The relay system includes an odd number of optical image-spinning lens groups arranged sequentially along the optical axis. Each optical image-spinning lens group includes two symmetrically arranged optical glass lens groups with an aperture stop between them, forming a 1:1 dual telecentric image-spinning system. Each optical glass lens group includes a third Hopkins rod lens 1, a fourth Hopkins rod lens 2, and a third cemented doublet lens group, which are separately arranged. The third cemented doublet lens group includes a positive lens 3 and a second negative lens 4 cemented together. The third Hopkins rod lens 1, the fourth Hopkins rod lens 2, the positive lens 3, and the second negative lens 4 are arranged sequentially along the incident light direction.

[0036] In this ultra-long endoscope, the objective lens includes a biconcave lens 5, a first Hopkins rod lens 6, a first cemented doublet lens group, a second cemented doublet lens group, and a single lens 11 arranged sequentially along the light incident direction. The first cemented doublet lens group includes a first lens 7 and a second lens 8 cemented together. The second cemented doublet lens group includes a second Hopkins rod lens 9 and a first negative lens 10 cemented together. The first lens of the objective lens facing the object being observed is a biconcave lens 5, which increases the negative optical power of the first lens, thereby satisfying a larger field of view. The optical image-rotating lens group consists of two separate optical glass lens groups, which are symmetrically arranged and have an aperture stop between them, forming a 1:1 dual telecentric image-rotating system. Each optical glass lens group has two Hopkins rod lenses, designated as the third Hopkins rod lens 1 and the fourth Hopkins rod lens 2. Therefore, the length of each optical image-transfer lens group is equivalent to the length of three traditional optical image-transfer lens groups. The length of the three optical image-transfer lens groups in this invention is sufficient to replace the length of five traditional optical image-transfer lens groups, significantly improving image quality, reducing unit stacking, and enabling ultra-long working lengths. The number of optical image-transfer lens groups used is selected according to needs. By combining an ultra-long objective lens with an ultra-long relay system, the problem of existing endoscopes being unable to guarantee both image quality and length requirements is solved. Thus, this ultra-long endoscope can guarantee image quality while meeting the design target working length, and also allows the designed objective lens to be as easy to manufacture and assemble as Hopkins lenses.

[0037] Optionally, both sides of the first Hopkins rod lens 6 are convex; in the first cemented doublet lens group, the end face of the first lens 7 near the object side is convex and the end face near the image side is concave, and both end faces of the second lens 8 are convex; in the second cemented doublet lens group, the end face of the second Hopkins rod lens 9 near the object side is concave and the end face near the image side is convex, and both end faces of the first negative lens 10 are concave; both end faces of the single lens 11 are convex.

[0038] Optionally, the relationship between half the image height IH of the objective lens and the focal length f of the objective lens is 0.6 ≤ IH / f ≤ 0.7; the relationship between half the image height IH of the objective lens and the distance TTL from the object side surface of the biconcave lens 5 to the imaging surface of the objective lens on the optical axis is 0.015 ≤ IH / TTL ≤ 0.03; the relationship between the center thickness d1 of the first Hopkins rod lens and the focal length f of the objective lens is 8 ≤ d1 / f ≤ 15; the relationship between the center thickness d2 of the second Hopkins rod lens and the focal length f of the objective lens is 8 ≤ d2 / f ≤ 13; and the effective focal length f of the biconcave lens 5 is... L1 The relationship with the focal length f of the objective lens is 0.8 ≤ |f L1 / f|≤1.2; The relationship between the effective focal length of the first Hopkins rod lens and the focal length f of the objective lens is 6≤|f L2 / f|≤9;The overall effective focal length f of the first cemented doublet lens group 34 The relationship with the focal length f of the objective lens is 2.2 ≤ |f 34 / f|≤3.8; The relationship between the overall effective focal length f56 of the second cemented doublet and the focal length f of the objective lens is 1≤|f 56 / f|≤2; Effective focal length f of single lens 11 L7 The relationship with the focal length f of the objective lens is 3.5 ≤ |f L7 / f|≤5.0; The relationship between the aperture number FNO of the objective lens and the distance TTL from the object side surface of the biconcave lens 5 to the imaging surface of the objective lens on the optical axis is 0.08≤FNO / TTL≤0.12; The range of the working distance L of the objective lens is 3≤L≤8.

[0039] Optionally, the distance between the biconcave lens 5 and the first Hopkins rod lens is 0.2mm to 8.0mm; the distance between the first Hopkins rod lens and the first cemented doublet lens group is 0.8mm to 8.0mm; the distance between the first cemented doublet lens group and the second cemented doublet lens group is 0.2mm to 0.4mm; and the distance between the second cemented doublet lens group and the single lens 11 is 0.3mm to 0.5mm.

[0040] Optionally, both sides of the third Hopkins rod lens 1 are convex, the end face of the fourth Hopkins rod lens 2 near the object side is concave, and the end face near the image side is convex. The surfaces of the positive lens 3 and the second negative lens 4 that are close to each other are cemented surfaces, and the cemented surfaces are flat.

[0041] Optionally, the radius of curvature of the end face of the third Hopkins rod lens 1 near the object side ranges from 20mm to 40mm, and the radius of curvature of the end face near the image side ranges from -80mm to -400mm; the radius of curvature of the end face of the fourth Hopkins rod lens 2 near the object side ranges from -80mm to -400mm, and the radius of curvature of the end face near the image side ranges from -30mm to -60mm; the radius of curvature of the end face of the positive lens 3 near the object side ranges from 4mm to 8mm; and the radius of curvature of the end face of the second negative lens 4 near the image side ranges from 3mm to 8mm.

[0042] Optionally, the thickness range of the third Hopkins bar lens 1 and the fourth Hopkins bar lens 2 is 20mm to 40mm, the thickness range of the positive lens 3 is 0.5mm to 2.5mm, and the thickness range of the second negative lens 4 is 0.5mm to 2mm.

[0043] Optionally, the refractive index of the material of the third Hopkins bar lens 1 is in the range of 1.72 to 2.20, the refractive index of the material of the fourth Hopkins bar lens 2 is in the range of 1.65 to 2.10, the refractive index of the material of the positive lens 3 is in the range of 1.44 to 1.80, and the refractive index of the material of the second negative lens 4 is in the range of 1.44 to 1.80.

[0044] Optionally, the material of the third Hopkins rod lens 1 is H-ZLAF96; the material of the fourth Hopkins rod lens 2 is H-ZLAF89L or H-ZLAF89LA; the material of the positive lens 3 is H-LAK52, H-LAK11 or H-LAK7A; and the material of the second negative lens 4 is F1 or F4.

[0045] Optionally, the total length of the objective lens and a set of optical image-rotating lenses is 200mm to 240mm at a diameter of 3.8mm.

[0046] Example 1: By connecting the objective lens to a single optical image-rotating lens group, a length of 220mm can be achieved with an aperture of 3.8mm, which can be used in laparoscopy. Figure 4 The graph shows the modulation transfer function (MTF) curve for this embodiment at a cutoff frequency of 100 lp / mm. It can be seen that the MTF is ≥ 0.39 across the entire field of view.

[0047] Example 2: The objective lens can be connected to a single optical image-rotating lens group to achieve a length of 200mm with a diameter of 3.8mm, which can be used for laparoscopy. Figure 5 The graph shows the modulation transfer function (MTF) curve for this embodiment at a cutoff frequency of 100 lp / mm. It can be seen that the MTF is ≥ 0.4 across the entire field of view.

[0048] Obviously, the above-disclosed embodiments of the present invention are merely illustrative of the invention. The embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. It is neither necessary nor possible to exhaustively describe all embodiments herein.

Claims

1. An ultra-long endoscope, characterized in that, include: The objective lens includes a biconcave structure lens (5), a first Hopkins rod lens (6), a first cemented doublet lens group, a second cemented doublet lens group, and a single lens (11) arranged sequentially along the incident direction of light. An aperture is provided between the first Hopkins rod lens (6) and the first cemented doublet lens group. The first cemented doublet lens group includes a first lens (7) and a second lens (8) cemented together. The second cemented doublet lens group includes a second Hopkins rod lens (9) and a first negative lens (10) cemented together. The relay system includes an odd number of optical image-spinning lens groups arranged sequentially along the optical axis. Each optical image-spinning lens group includes two symmetrically arranged optical glass lens groups with an aperture stop between them, forming a 1:1 dual telecentric image-spinning system. The optical glass lens groups include a third Hopkins rod lens (1), a fourth Hopkins rod lens (2), and a third cemented doublet lens group, which are arranged separately. The third cemented doublet lens group includes a positive lens (3) and a second negative lens (4) cemented together. The third Hopkins rod lens (1), the fourth Hopkins rod lens (2), the positive lens (3), and the second negative lens (4) are arranged sequentially along the incident light direction. Both sides of the first Hopkins rod lens (6) are convex; in the first cemented doublet lens group, the end face of the first lens (7) near the object side is convex and the end face near the image side is concave, and both end faces of the second lens (8) are convex; in the second cemented doublet lens group, the end face of the second Hopkins rod lens (9) near the object side is concave and the end face near the image side is convex, and both end faces of the first negative lens (10) are concave; both end faces of the single lens (11) are convex. Both sides of the third Hopkins rod lens (1) are convex. The end face of the fourth Hopkins rod lens (2) near the object side is concave and the end face near the image side is convex. The surfaces of the positive lens (3) and the second negative lens (4) that are close to each other are cemented surfaces, which are flat.

2. The ultra-long endoscope according to claim 1, characterized in that: The relationship between half the height of the objective image IH and the focal length f of the objective lens is 0.6 ≤ IH / f ≤ 0.7; the relationship between half the height of the objective image IH and the distance TTL from the object side surface of the biconcave lens (5) to the imaging surface of the objective lens on the optical axis is 0.015 ≤ IH / TTL ≤ 0.03; the relationship between the center thickness d1 of the first Hopkins rod lens and the focal length f of the objective lens is 8 ≤ d1 / f ≤ 15; the relationship between the center thickness d2 of the second Hopkins rod lens and the focal length f of the objective lens is 8 ≤ d2 / f ≤ 13; the effective focal length f of the biconcave lens (5) is... L1 The relationship with the focal length f of the objective lens is 0.8 ≤ |f L1 / f|≤1.2; Effective focal length f of the first Hopkins rod lens L2 The relationship between the objective lens's focal length f and the focal length f is 6 ≤ |f L2 / f|≤9;The overall effective focal length f of the first cemented doublet lens group 34 The relationship with the focal length f of the objective lens is 2.2 ≤ |f 34 / f|≤3.8; the overall effective focal length f of the second cemented doublet lens group 56 The relationship between the objective lens and its focal length f is 1 ≤ |f 56 / f|≤2;Effective focal length f of a single lens (11) L7 The relationship with the focal length f of the objective lens is 3.5 ≤ |f L7 / f|≤5.0; The relationship between the aperture number FNO of the objective lens and the distance TTL on the optical axis from the object side of the biconcave lens (5) to the imaging surface of the objective lens is 0.08≤FNO / TTL≤0.12; The range of the working distance L of the objective lens is 3 ≤L≤8.

3. The ultra-long endoscope according to claim 1, characterized in that: The distance between the biconcave lens (5) and the first Hopkins rod lens is 0.2mm to 8.0mm; the distance between the first Hopkins rod lens and the first cemented doublet lens group is 0.8mm to 8.0mm. The distance between the first cemented doublet lens group and the second cemented doublet lens group is 0.2mm~0.4mm; the distance between the second cemented doublet lens group and the single lens (11) is 0.3mm~0.5mm.

4. The ultra-long endoscope according to claim 2, characterized in that: The curvature radius of the end face of the third Hopkins rod lens (1) near the object side is 20mm to 40mm, and the curvature radius of the end face near the image side is -80mm to -400mm. The curvature radius of the end face of the fourth Hopkins rod lens (2) near the object side is -80mm to -400mm, and the curvature radius of the end face near the image side is -30mm to -60mm. The curvature radius of the end face of the positive lens (3) near the object side is 4mm to 8mm. The curvature radius of the end face of the second negative lens (4) near the image side is 3mm to 8mm.

5. The ultra-long endoscope according to claim 1, characterized in that: The thickness range of the third Hopkins bar lens (1) and the fourth Hopkins bar lens (2) is 20mm to 40mm, the thickness range of the positive lens (3) is 0.5mm to 2.5mm, and the thickness range of the second negative lens (4) is 0.5mm to 2mm.

6. The ultra-long endoscope according to claim 1, characterized in that: The refractive index of the material of the third Hopkins bar lens (1) is in the range of 1.72 to 2.20, the refractive index of the material of the fourth Hopkins bar lens (2) is in the range of 1.65 to 2.10, the refractive index of the material of the positive lens (3) is in the range of 1.44 to 1.80, and the refractive index of the material of the second negative lens (4) is in the range of 1.44 to 1.

80.

7. The ultra-long endoscope according to claim 1, characterized in that: The material of the third Hopkins bar lens (1) is H-ZLAF96; the material of the fourth Hopkins bar lens (2) is H-ZLAF89L or H-ZLAF89LA; the material of the positive lens (3) is H-LAK52, H-LAK11 or H-LAK7A; and the material of the second negative lens (4) is F1 or F4.

8. The ultra-long endoscope according to claim 1, characterized in that: The total length of the objective lens and a set of optical image-rotating lenses is 200mm to 240mm at a diameter of 3.8mm.

Images