Endoscope and objective lens system thereof

Abstract

The objective lens system has a first observation state and a second observation state, the magnification of the objective lens system in the first observation state is smaller than that of the objective lens system in the second observation state, and the field angle of the objective lens system in the first observation state is larger than that of the objective lens system in the second observation state. The objective lens system comprises a first lens group, a diaphragm, a second lens group, a third lens group and a fourth lens group which are sequentially arranged from the object side to the image side along the optical axis, the positions of the first lens group and the fourth lens group are kept unchanged when the observation state is switched, and the second lens group and the third lens group respectively move along the optical axis for focusing. According to the objective lens system, the observation states with different magnifications can be switched, and the focal lengths of the lens groups of the objective lens system are symmetrically distributed in a negative-positive-positive-negative manner, so that the aberration of the objective lens system in various observation states can be well corrected under the condition that a small number of lenses are used by the objective lens system.

Description

Technical Field

[0001] The present invention relates to the technical field of endoscopes, and particularly to an endoscope and an objective lens system thereof. Background Art

[0002] Endoscopes have gradually become an important means for diagnosing lesions in body cavities. Ordinary endoscopes have a low magnification ratio, and using such endoscopes can only observe the area where the lesion tissue is located. Therefore, it is only possible to find the area where the lesion tissue is located through the endoscope, and then cut off the lesion tissue through an instrument for detection outside the body. By using an endoscope with multiple magnification ratios, the position where the lesion tissue is located can be found by first observing in the low magnification mode, and then the fine structures such as the cell nuclei of the lesion tissue can be observed in the high magnification mode, and relatively accurate optical biopsy can be directly completed in the body. In addition, in a mode with a high enough magnification ratio, more accurate resection surgery can be performed on the lesion tissue. However, for existing endoscopes that can switch between multiple magnification modes, the objective lens systems used have the disadvantages of a large number of lenses, too long overall optical length, and large aberration. Summary of the Invention

[0003] The object of the present invention is to provide an objective lens system for an endoscope, which can switch between observation states with different magnification ratios, and the objective lens system can well correct the aberration in various observation states with a relatively small number of lenses. The present invention also provides an endoscope.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] An objective lens system for an endoscope has a first observation state and a second observation state. The magnification ratio of the objective lens system in the first observation state is less than that in the second observation state, and the field angle of view of the objective lens system in the first observation state is greater than that in the second observation state. The objective lens system includes a first lens group, a diaphragm, a second lens group, a third lens group, and a fourth lens group arranged in sequence from the object side to the image side along the optical axis. The focal lengths of the first lens group and the fourth lens group are both negative, and the focal lengths of the second lens group and the third lens group are both positive;

[0006] During the switching process of the objective lens system between the first observation state and the second observation state, the positions of the first lens group and the fourth lens group along the optical axis remain unchanged, and the second lens group and the third lens group move along the optical axis respectively for focusing;

[0007] The objective lens system satisfies the following conditional expressions: w1≥65°, |β2|≥2.33;

[0008] Wherein, w1 represents the semi-field angle of the objective lens system in the first observation state, and β2 represents the transverse magnification of the objective lens system in the second observation state.

[0009] Optionally, during the switching process of the objective lens system between the first observation state and the second observation state, the aperture moves synchronously with the second lens group.

[0010] Optionally, the following conditional formula is also satisfied: 0.01 ≤ △d 1ST / f1 ≤ 2.95, 0.14 ≤ △d 34 / f1 ≤ 3.50;

[0011] Wherein, f1 represents the focal length of the objective lens system in the first observation state, and △d 1ST represents the distance between the first lens group and the aperture along the optical axis, and △d 34 represents the distance between the third lens group and the fourth lens group along the optical axis.

[0012] Optionally, during the switching process of the objective lens system between the first observation state and the second observation state, the second lens group and the third lens group move in the same direction.

[0013] Optionally, the objective lens system further has a third observation state;

[0014] The magnification of the objective lens system in the third observation state is between the magnification in the first observation state and the magnification in the second observation state;

[0015] The field angle of the objective lens system in the third observation state is between the field angle in the first observation state and the field angle in the second observation state.

[0016] Optionally, during the sequential switching process of the objective lens system between the first observation state, the third observation state, and the second observation state, the distance between the second lens group and the third lens group along the optical axis first increases and then decreases.

[0017] Optionally, during the switching process of the objective lens system for observing states, the back working distance of the objective lens system remains unchanged.

[0018] Optionally, both the second lens group and the third lens group include cemented lenses.

[0019] Optionally, the first lens group includes a first lens, a second lens, and a third lens. The focal length of the first lens is negative, and the combined focal length of the second lens and the third lens is positive.

[0020] An endoscope includes the objective lens system described in any one of the above.

[0021] As can be seen from the above technical solutions, an objective lens system for an endoscope provided by the present invention has a first observation state and a second observation state. The magnification in the first observation state is less than that in the second observation state, and the field of view angle in the first observation state is greater than that in the second observation state. The objective lens system includes a first lens group, a diaphragm, a second lens group, a third lens group, and a fourth lens group arranged in sequence from the object side to the image side along the optical axis. During the switching process between the first observation state and the second observation state of the objective lens system, the positions of the first lens group and the fourth lens group along the optical axis remain unchanged, and the second lens group and the third lens group move along the optical axis respectively for focusing. Among them, the field of view of the objective lens system in the first observation state is larger, and the semi-field of view angle in the first observation state satisfies w1≥65°, enabling the objective lens system to perform large-field observation; the magnification in the second observation state of the objective lens system is larger, and the transverse magnification in the second observation state satisfies |β2|≥2.33, enabling the objective lens system to perform high-magnification observation. Therefore, the objective lens system of the present invention can switch between different magnification observation states and can achieve large-field observation and high-magnification observation. Moreover, the focal lengths of the first lens group and the fourth lens group are both negative, and the focal lengths of the second lens group and the third lens group are both positive. The focal lengths of each lens group of the present objective lens system are distributed symmetrically as negative, positive, positive, negative, which can enable the objective lens system to well correct the aberrations in various observation states with a relatively small number of lenses.

[0022] An endoscope provided by the present invention can achieve the above beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 FIG. 15 is a schematic structural diagram of an objective lens system in the first observation state provided in the first embodiment;

[0025] Figure 2 For Figure 1 FIG. 21 is a schematic structural diagram of the objective lens system in the third observation state shown in FIG. 21;

[0026] Figure 3 For Figure 1 FIG. 27 is a schematic structural diagram of the objective lens system in the second observation state shown in FIG. 27;

[0027] Figure 4 Schematic diagram of spot focusing when the objective lens system of the first embodiment is in each observation state;

[0028] Figure 5 Schematic structural diagram of an objective lens system provided in the second embodiment in the first observation state;

[0029] Figure 6 For Figure 5 Schematic structural diagram of the objective lens system shown in the third observation state;

[0030] Figure 7 For Figure 5 Schematic structural diagram of the objective lens system shown in the second observation state;

[0031] Figure 8 Schematic diagram of spot focusing when the objective lens system of the second embodiment is in each observation state.

[0032] Reference numerals in the accompanying drawings of the specification include:

[0033] G1 - First lens group, G2 - Second lens group, G3 - Third lens group, G4 - Fourth lens group, L1 - First lens, L2 - Second lens, L3 - Third lens, L4 - Fourth lens, L5 - Fifth lens, L6 - Sixth lens, L7 - Seventh lens, L8 - Eighth lens, L9 - Protective glass, ST - Diaphragm, O - Object plane, 12 - Image plane, w1 - Chief ray of central field of view, w2 - Chief ray of marginal field of view. Specific embodiments

[0034] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Endoscopes have gradually become an important means for diagnosing diseases in body cavities. For example, with the improvement of living standards, the incidence of digestive tract malignant tumors is increasing day by day, and endoscopes are widely used in digestive tract examinations. Due to the low magnification of ordinary endoscopes, only the area where the lesion tissue is located can be observed using such endoscopes. Therefore, the area where the lesion tissue is located can only be found through the endoscope, and then the lesion tissue is cut off by an instrument for detection outside the body. By using an endoscope with multiple magnification ratios, the location of the lesion tissue can be found first by observing in the low magnification mode, and then the fine structures such as the cell nuclei of the lesion tissue can be observed using the high magnification mode, and relatively accurate optical biopsy can be directly completed in the body. In addition, in a mode with a high enough magnification, more accurate resection surgery can be performed on the lesion tissue. However, for the existing endoscopes that can switch between multiple magnification modes, the objective lens systems used have the disadvantages of a large number of lenses, too long optical total length, and large aberration. In view of this, the present invention provides an endoscope and its objective lens system, which can switch between different magnification observation states, and can correct the aberration in various observation states well while using a smaller number of lenses in the objective lens system.

[0036] An objective lens system provided in this embodiment has a first observation state and a second observation state. The magnification of the objective lens system in the first observation state is less than that in the second observation state, and the field angle of view of the objective lens system in the first observation state is greater than that in the second observation state. The objective lens system includes a first lens group, a diaphragm, a second lens group, a third lens group, and a fourth lens group arranged in sequence from the object side to the image side along the optical axis. The focal lengths of the first lens group and the fourth lens group are both negative, and the focal lengths of the second lens group and the third lens group are both positive;

[0037] During the switching process of the objective lens system between the first observation state and the second observation state, the positions of the first lens group and the fourth lens group along the optical axis remain unchanged, and the second lens group and the third lens group move along the optical axis respectively for focusing;

[0038] The objective lens system satisfies the following conditional expressions: w1≥65°, |β2|≥2.33;

[0039] Wherein, w1 represents the semi-field angle of view of the objective lens system in the first observation state, and β2 represents the transverse magnification of the objective lens system in the second observation state.

[0040] The focal length of the first lens group is negative, that is, f G1 <0, f G1represents the focal length of the first lens group. Thus, the first lens group can couple large-angle light from the object side into the aperture, enabling the objective lens system to have a larger field of view. Additionally, it can make the large-angle light from the object side have a longer back working distance, allowing the subsequent moving lens group to have a larger position change space and a wider position change range.

[0041] The focal length of the second lens group is positive, i.e., f G2 > 0, f G2 represents the focal length of the second lens group. Thus, the aberrations generated by the second lens group can participate in correcting the aberrations generated by the first lens group.

[0042] The focal length of the third lens group is positive, i.e., f G3 > 0, f G3 represents the focal length of the third lens group. The third lens group uses a positive lens group, so that the aberrations it generates can participate in correcting the aberrations generated by the first lens group, and can reduce the aberration burden of the second lens group. For a lens group, the greater the aberration burden, the greater the curvature of the lenses in the lens group, and then it is more difficult to manufacture and assemble precisely. Therefore, using the positive third lens group to reduce the aberration burden of the second lens group can make the second lens group easier to manufacture and assemble.

[0043] The focal length of the fourth lens group is negative, i.e., f G4 < 0, f G4 represents the focal length of the fourth lens group, which can effectively reduce the incident angle of the chief ray on the image plane, resulting in smaller off-axis aberrations under a large aperture. Additionally, the fourth lens group is a fixed lens group, which uses a negative lens group to compensate for the negative axial aberrations caused by the large position changes of the second lens group and the third lens group, enabling the second lens group and the third lens group to have a wider aberration change space to achieve a wider position change range of the moving lens group. And it can also correct the off-axis aberrations generated by the second lens group and the third lens group with positive focal lengths. Additionally, using a negative lens group for the fourth lens group can increase the back working distance of the objective lens system. The back working distance of the objective lens system refers to the distance from the lens closest to the image plane in the objective lens system to the image plane. The back working distance of the objective lens system is usually used as the tolerance compensation amount during the assembly process. A larger back working distance of the objective lens system helps make the objective lens system easier to assemble.

[0044] Therefore, the focal lengths of the lens groups of this objective lens system are distributed in a negative-positive-negative-positive symmetry, which can well correct the system aberrations in various observation states with as few lenses as possible, resulting in fewer lenses and helping to reduce the overall optical length.

[0045] Adapted to the change of object distance, the second lens group and the third lens group are respectively moved along the optical axis for focusing. The magnification of the objective lens system in the first observation state is small and the field of view angle is large. The objective lens system in the first observation state can focus on distant objects. The magnification of the objective lens system in the second observation state is large and the field of view angle is small. The objective lens system in the second observation state can focus on nearby objects. Therefore, the objective lens system of this embodiment can switch between observation states with different magnifications and can be applied to an endoscope to switch the observation state according to the inspection requirements. The semi-field of view angle of the objective lens system in the first observation state satisfies w1≥65°, enabling the objective lens system to perform large-field observation. The transverse magnification of the objective lens system in the second observation state satisfies |β2|≥2.33, enabling the objective lens system to perform high-magnification observation. Therefore, the objective lens system of this embodiment can switch between different observation states and can achieve large-field observation and high-magnification observation.

[0046] In some embodiments, during the switching process of the objective lens system between the first observation state and the second observation state, the aperture moves synchronously with the second lens group, which helps to correct the off-axis aberration generated after the positions of the second lens group and the third lens group change, and also helps to increase the change range of the focal length to achieve high-magnification imaging.

[0047] In some embodiments, the objective lens system of the present invention also satisfies the following conditional expressions:

[0048] 0.01≤△d 1ST / f1≤2.95, 0.14≤△d 34 / f1≤3.50;

[0049] Wherein, f1 represents the focal length of the objective lens system in the first observation state, and △d 1ST represents the distance between the first lens group and the aperture along the optical axis, and △d 34 represents the distance between the third lens group and the fourth lens group along the optical axis. If △d 1ST / f1 exceeds its corresponding lower limit, it will cause position interference between the first lens group and the aperture in space. If it exceeds the corresponding upper limit, it will cause the objective lens system to be large-sized and the aberration to be difficult to correct well. If △d 34 / f1 exceeds its corresponding lower limit, it will cause position interference between the third lens group and the fourth lens group in space. If it exceeds the corresponding upper limit, it will cause the objective lens system to be large-sized and the aberration to be difficult to correct well.

[0050] In some embodiments, during the switching process of the objective lens system between the first observation state and the second observation state, the moving directions of the second lens group and the third lens group are the same, that is, the second lens group and the third lens group move in the same direction, which can reduce the design difficulty of the mechanical structure for controlling the movement of the second lens group and the third lens group and is beneficial to the operation of state switching.

[0051] In some embodiments, the objective lens system further has a third observation state; the magnification of the objective lens system in the third observation state is between the magnification in the first observation state and the magnification in the second observation state; the field angle of view of the objective lens system in the third observation state is between the field angle of view in the first observation state and the field angle of view in the second observation state. Then, this objective lens system can switch between at least three observation states with different magnifications.

[0052] The first observation state m1 can be regarded as the normal state. The semi-field angle w1 of the objective lens system in the first observation state satisfies: w1≥65°. When applied to an endoscope, it can ensure that the operator can easily find the target site.

[0053] The second observation state m2 can be regarded as the microscopic state. The transverse magnification β2 of the objective lens system in the second observation state satisfies: |β2|≥2.33. When applied to an endoscope, it can ensure that the operator observes the fine structure of the target site. For example, when this objective lens system is paired with an electronic display system with a magnification of 222 times (or 214 times), the object-side target can be magnified 520 times (or 500 times), and it can ensure that the operator observes fine characteristic structures such as cell nuclei with a size in the μm range.

[0054] The third observation state m3 is an intermediate state. When the objective lens system is in this observation state, it can meet the observation requirements between the first observation state m1 and the second observation state m2. For example, it can be used to assist the operator in narrowing the target to be observed in the second observation state m2, or it can also be used to observe a target slightly larger than the target that can be clearly observed in the second observation state m2.

[0055] In some embodiments, the objective lens system may include multiple third observation states. The field angle of view and magnification of the objective lens system in each third observation state are different respectively. The number of third observation states that the objective lens system can be in can be 1 to 10.

[0056] In some embodiments, during the sequential switching process of the objective lens system among the first observation state, the third observation state, and the second observation state, the distance between the second lens group and the third lens group along the optical axis is always changing. Further, the distance between the second lens group and the third lens group along the optical axis first increases and then decreases. This can make full use of the space reserved for the movement of the lens group, and is conducive to aberration compensation, so that the aberrations in various observation states are well corrected. Thus, it helps to reduce the overall optical length of the objective lens system and the length of the objective lens system under the condition of achieving the same zoom range.

[0057] In some embodiments, during the switching of the observation state of the objective lens system, the back working distance of the objective lens system remains unchanged, that is, the distance from the lens closest to the image plane in the fourth lens group to the image plane remains unchanged. The structural tolerances of the optical system will deteriorate its image quality. Then, the back working distance of the objective lens system remains unchanged in various observation states, which can reduce the structural tolerances of the objective lens system and reduce the deterioration of the system image quality.

[0058] In some embodiments, both the second lens group and the third lens group include cemented lenses. The second lens group and the third lens group are movable lens groups. Compared with using separate lenses, they can remain stable during movement, reduce the precision requirements for the control mechanism, and help reduce the introduction of aberrations during movement.

[0059] In some embodiments, the first lens group may include a first lens, a second lens, and a third lens. The second lens group may include a fourth lens and a fifth lens. The third lens group may include a sixth lens and a seventh lens. The fourth lens group may include an eighth lens. In this embodiment, the objective lens system includes eight lenses, and it can also correct aberrations well with as few lenses as possible. In this embodiment, the focal length of the first lens is negative, and the combined focal length of the second lens and the third lens is positive. Thus, the negative aberrations generated by the second lens and the third lens can participate in correcting the large positive aberrations generated by the first lens group, enabling the objective lens system to obtain a better imaging effect.

[0060] In some embodiments, the first lens group may include a first lens and a second lens. The second lens group may include a fourth lens and a fifth lens. The third lens group may include a sixth lens and a seventh lens. The fourth lens group may include an eighth lens. In this embodiment, the objective lens system includes seven lenses, using fewer lenses and making the objective lens length smaller.

[0061] In the above embodiments, it may be that the fourth lens and the fifth lens are cemented, and the sixth lens and the seventh lens are cemented. Compared with using separate lenses, they can remain stable during movement, reducing the precision requirements for the control mechanism.

[0062] The following uses specific embodiments to elaborate on this objective lens system in detail.

[0063] Embodiment 1

[0064] Please refer to Figures 1 to 3 , Figure 1 which is a schematic structural diagram of an objective lens system provided for the first embodiment in the first observation state. Figure 2 For Figure 1 the schematic structural diagram of the objective lens system shown in the third observation state. Figure 3 For Figure 1Schematic structural diagram of the objective lens system in the second observation state. As Figures 1 to 3 shown, the objective lens system of this embodiment includes a first lens group G1, a diaphragm ST, a second lens group G2, a third lens group G3, and a fourth lens group G4 arranged in sequence from the object side to the image side along the optical axis. Among them, the focal length f of the first lens group G1 G1 < 0, and it includes a first lens L1, a second lens L2, and a third lens L3. The first lens L1 can specifically be a negative plano-concave lens with its concave surface facing the image side. The combined focal length of the second lens L2 and the third lens L3 is positive. In this way, the negative aberration generated by the second lens L2 and the third lens L3 can participate in correcting the large positive aberration generated by the first lens group G1. The focal length f of the second lens group G2 G2 > 0, and it includes a first cemented lens composed of a fourth lens L4 and a fifth lens L5. The focal length f of the third lens group G3 G3 > 0, and it includes a second cemented lens composed of a sixth lens L6 and a seventh lens L7. The focal length f of the fourth lens group G4 G4 < 0, and it includes an eighth lens L8. A protective glass L9 is arranged on the side of the image plane 12 of the objective lens system close to the fourth lens group G4. When the objective lens is installed with the imaging device, the imaging device is arranged at the image plane 12 of this objective lens system, and the protective glass L9 is used to protect the imaging device from damage.

[0065] The basic data of the objective lens system in this embodiment are shown in Table 1. Among them, each lens has an object side facing the object and an image side facing the image. The object plane O is the plane where the object-side target is located. Surfaces 1 and 2 are the object side and the image side of the first lens L1 respectively. Surfaces 3 and 4 are the object side and the image side of the second lens L2 respectively. Surfaces 5 and 6 are the object side and the image side of the third lens L3 respectively. Surface 7 is the diaphragm plane. Surface 8 is the object side of the fourth lens L4. Surface 9 is the image side of the fourth lens L4 and at the same time is the object side of the fifth lens L5. Surface 10 is the image side of the fifth lens L5. Surface 11 is both the object side and the image side of the sixth lens L6. Surface 12 is the image side of the sixth lens L6 and at the same time is the object side of the seventh lens L7. Surface 13 is the image side of the seventh lens L7. Surfaces 14 and 15 are the object side and the image side of the eighth lens L8 respectively. Surfaces 16 and 17 are the object side and the image side of the protective glass L9 respectively. Surface 18 is the image plane 12 of this objective lens system. The refractive index and Abbe number corresponding to the rows where surfaces 1, 3, 5, 8, 9, 11, 12, 14, 16 are located are the refractive index and Abbe number of the materials of L1, L2, L3, L4, L5, L6, L7, L8, L9 respectively. The unit of the radius of curvature, thickness, or interval is millimeter.

[0066] Table 1

[0067]

[0068]

[0069] For combined reference Figures 1 to 3 As shown, when the objective lens system is changed from the first observation state m1 to the third observation state m3, both the second lens group G2 and the third lens group G3 move toward the object side, and the moving directions of the two are the same. When the objective lens system continues to change from the third observation state m3 to the second observation state m2, both the second lens group G2 and the third lens group G3 continue to move toward the object side. During this process, the distance between the second lens group G2 and the third lens group G3 along the optical axis first increases and then decreases. When the objective lens system is changed from the second observation state m2 to the first observation state m1, it can be carried out according to the reverse process of the above process. During the process of the objective lens system sequentially switching each observation state, the moving directions of the second lens group G2 and the third lens group G3 are the same, which can reduce the design difficulty of the mechanical structure for controlling the movement of the second lens group G2 and the third lens group G3, and is beneficial to the operation of state switching. And the distance between the second lens group G2 and the third lens group G3 along the optical axis first increases and then decreases, which can make full use of the space reserved for the movement of the moving lens group, and helps to reduce the overall optical length of the objective lens system and the length of the objective lens system under the condition of achieving the same zoom range. Among them, the aperture stop ST moves synchronously with the second lens group G2, which helps to correct the off-axis aberration generated after the positions of the second lens group G2 and the third lens group G3 change, and also helps to increase the change range of the focal length to achieve high-magnification imaging. And the back working distance of the objective lens system remains unchanged, which can reduce the structural tolerance of the objective lens system and reduce the degradation of the system image quality.

[0070] The key optical parameters of the objective lens system in this embodiment are shown in Table 2, where d0 is the axial distance between the object-side target and the vertex of the object side surface of the first lens L1, d6 is the axial distance between the vertex of the image side surface of the third lens L3 and the aperture plane, d 10 is the axial distance between the vertex of the image side surface of the fifth lens L5 and the vertex of the object side surface of the sixth lens L6, d 13 is the axial distance between the vertex of the image side surface of the seventh lens L7 and the vertex of the object side surface of the eighth lens L8, f is the focal length, w is the half field angle, the half field angle is the angle between the chief ray w2 of the marginal field and the chief ray w1 of the central field, the chief ray w1 of the central field is collinear with the optical axis of the objective lens system, the optical axis of the objective lens system is the central symmetry axis of all lenses, Fno is the f-number, β is the paraxial lateral magnification of the objective lens system, IH is the half image height, that is, the vertical axis distance between the chief ray w2 of the marginal field and the chief ray w1 of the central field on the image plane 12. The units of the focal length and the half image height are both millimeters.

[0071] Table 2

[0072]

[0073] It can be seen that the semi-field angle w1 of the first observation state m1 is as high as 70°. It can be seen that the field of view of the objective lens system in the first observation state m1 is very large, larger than the field of view angle of 40° - 60° of general endoscopes. The absolute value of the transverse magnification β of the second observation state m2 is as high as 2.47. When paired with an imaging device with a pixel size of 1.4μm and a common medical monitor of 27 inches (pixel size 0.3113mm), a magnification effect of 549 times on the object-side target can be achieved, where 2.47 * (0.3113 / 0.0014) ≈ 549.

[0074] In this embodiment, the conditional values of the objective lens system in each state are shown in Table 3, where, △d 1ST / f1 represents the ratio of the distance along the optical axis between the first lens group G1 and the aperture stop ST to the focal length of the objective lens system in the first observation state m1 when the aperture stop ST moves synchronously with the second lens group G2, △d 34 / f1 represents the ratio of the distance along the optical axis between the third lens group G3 and the fourth lens group G4 to the focal length of the objective lens system in the first observation state m1, f G1 represents the focal length of the first lens group G1, f G2 represents the focal length of the second lens group G2, f G3 represents the focal length of the third lens group G3, f G4 represents the focal length of the fourth lens group G4, f L23 represents the combined focal length of the second lens L2 and the third lens L3.

[0075] Table 3

[0076]

[0077] Reference can be made to Figure 4 , Figure 4 which is a schematic diagram of spot focusing when the objective lens system of the first embodiment is in each observation state. The upper figure shows the spot focusing situation at an image height of 0mm, and the lower figure shows the spot focusing situation at an image height of 1.045mm. It can be seen that the focused spots of the objective lens system at an image height of 0mm in each observation state are all contained within the Airy disk, and the focused spots of the objective lens system at an image height of 1.045mm in each observation state are all contained within the Airy disk. It can be seen that various aberrations of this optical system are well corrected, and the optical system is close to the diffraction limit and can be regarded as an ideal imaging system.

[0078] Embodiment 2

[0079] Please refer to Figures 5 to 7 , Figure 5 which is a schematic structural diagram of an objective lens system in the first observation state provided by the second embodiment, Figure 6 is Figure 5 a schematic structural diagram of the objective lens system shown in the third observation state,Figure 7 For Figure 5 the schematic structural diagram of the objective lens system shown in the second observation state. As Figures 5 to 7 shown, the objective lens system of this embodiment includes a first lens group G1, a diaphragm ST, a second lens group G2, a third lens group G3, and a fourth lens group G4 arranged in sequence from the object side to the image side along the optical axis. Among them, the focal length f G1 of the first lens group G1 < 0, and it includes a first lens L1 and a second lens L2. The first lens L1 is a negative plano-concave lens with the concave surface facing the image side, and the second lens L2 is a meniscus lens, and the surface vertices of both sides are on the right side of the center of the sphere. The focal length f G2 of the second lens group G2 > 0, and it includes a first cemented lens composed of a fourth lens L4 and a fifth lens L5; the focal length f G3 of the third lens group G3 > 0, and it includes a second cemented lens composed of a sixth lens L6 and a seventh lens L7; the focal length f G2 of the fourth lens group G4 < 0, and it includes an eighth lens L8. A protective glass L9 is arranged on the side of the image plane 12 of the objective lens system close to the fourth lens group G4. When the objective lens is installed with the imaging device, the imaging device is arranged on the image plane 12 of this objective lens system, and the protective glass L9 is used to protect the imaging device from damage.

[0080] The basic data of the objective lens system in this embodiment are shown in Table 4. Among them, each lens has an object side facing the object and an image side facing the image. The object plane O represents the plane where the object-side target is located. Surfaces 1 and 2 are the object side and the image side of the first lens L1 respectively. Surfaces 3 and 4 are the object side and the image side of the second lens L2 respectively. Surface 5 is the diaphragm surface. Surface 6 is the object side of the fourth lens L4. Surface 7 is the image side of the fourth lens L4 and is also the object side of the fifth lens L5. Surface 8 is the image side of the fifth lens L5. Surface 9 is the object side of the sixth lens L6. Surface 10 is the image side of the sixth lens L6 and is also the object side of the seventh lens L7. Surface 11 is the image side of the seventh lens L7. Surfaces 12 and 13 are the object side and the image side of the eighth lens L8 respectively. Surfaces 14 and 15 are the object side and the image side of the protective glass L9 respectively. Surface 16 is the image plane. The refractive index and Abbe number corresponding to the rows where surfaces 1, 3, 6, 7, 9, 10, 12, and 14 are located are the refractive index and Abbe number of the materials of L1, L2, L4, L5, L6, L7, L8, and L9 respectively. The unit of the radius of curvature, thickness, or interval is millimeter.

[0081] Table 4

[0082]

[0083]

[0084] For reference, it can be combined withFigures 5 to 8 As shown, when the objective lens system is changed from the first observation state m1 to the third observation state m3, both the second lens group G2 and the third lens group G3 move toward the object side, and their moving directions are the same. When the objective lens system continues to change from the third observation state m3 to the second observation state m2, both the second lens group G2 and the third lens group G3 continue to move toward the object side. During this process, the distance between the second lens group G2 and the third lens group G3 along the optical axis first increases and then decreases. When the objective lens system is changed from the second observation state m2 to the first observation state m1, it can be carried out according to the reverse process of the above process. During the process of the objective lens system switching each observation state, the moving directions of the second lens group G2 and the third lens group G3 are the same, which can reduce the design difficulty of the mechanical structure for controlling the movement of the second lens group G2 and the third lens group G3, and is beneficial to the operation of state switching. And the distance between the second lens group G2 and the third lens group G3 along the optical axis first increases and then decreases, which can make full use of the space reserved for the movement of the moving lens group, and helps to reduce the overall optical length of the objective lens system and the length of the objective lens system under the condition of achieving the same zoom range. Among them, the aperture stop ST moves synchronously with the second lens group G2, which helps to correct the off-axis aberration generated after the positions of the second lens group G2 and the third lens group G3 are changed, and also helps to increase the change range of the focal length to achieve high-magnification imaging. And the back working distance of the objective lens system remains unchanged, which can reduce the structural tolerance of the objective lens system and reduce the degradation of the system image quality.

[0085] In this embodiment, the key optical parameters of the objective lens system are shown in Table 5. Among them, d0 is the axial distance between the object-side target and the vertex of the object side of the first lens L1, d4 is the axial distance between the vertex of the image side of the second lens L2 and the aperture plane, d8 is the axial distance between the vertex of the image side of the fifth lens L5 and the vertex of the object side of the sixth lens L6, and d 11 is the axial distance between the vertex of the image side of the seventh lens L7 and the vertex of the object side of the eighth lens L8. f is the focal length, w is the semi-field angle, Fno is the aperture number, β is the paraxial transverse magnification of the objective lens system, and IH is the semi-image height.

[0086] Table 5

[0087]

[0088] It can be seen that the semi-field angle w1 of the first observation state m1 is as high as 70°. It can be seen that the field of view of the objective lens system in the first observation state m1 is very large, which is larger than the field of view angle of 40°-60° of a general endoscope. The absolute value of the transverse magnification β of the second observation state m2 is as high as 2.46. When paired with an imaging device with a pixel size of 1.4μm and a common medical monitor of 27 inches (pixel size 0.3113mm), a magnification effect of 547 times can be achieved for the object-side target, where 2.46*(0.3113 / 0.0014)≈547. ​

[0089] In this embodiment, the conditional values of the objective lens system in various states are shown in Table 6, where Δd 1ST / f1 represents the ratio of the distance along the optical axis between the first lens group G1 and the aperture stop ST to the focal length of the objective lens system in the first observation state m1 when the aperture stop ST moves synchronously with the second lens group G2, and Δd 34 / f1 represents the ratio of the distance along the optical axis between the third lens group G3 and the fourth lens group G4 to the focal length of the objective lens system in the first observation state m1, and f G1 represents the focal length of the first lens group G1, and f G2 represents the focal length of the second lens group G2, and f G3 represents the focal length of the third lens group G3, and f G4 represents the focal length of the fourth lens group G4, and f L23 represents the combined focal length of the second lens L2 and the third lens L3.

[0090] Table 6

[0091]

[0092] For reference Figure 8 , Figure 8 , is a schematic diagram of spot focusing when the objective lens system of the second embodiment is in each observation state. The upper figure shows the spot focusing at an image height of 0 mm, and the lower figure shows the spot focusing at an image height of 1.045 mm. It can be seen that the focused spots at an image height of 0 mm in each observation state of the objective lens system are all contained within the Airy disk, and the focused spots at an image height of 1.045 mm in each observation state of the objective lens system are all contained within the Airy disk. It can be seen that various aberrations of this optical system are well corrected, and the optical system is close to the diffraction limit and can be regarded as an ideal imaging system.

[0093] This embodiment also provides an endoscope, including the objective lens system as described in the above embodiment. Among them, for the detailed technical features and technical effects of this objective lens system, please refer to the introduction in the relevant part above, and will not be elaborated here. In addition, regarding other structural features in the endoscope, conventional solutions in the prior art can also be referred to, and will not be described in detail here.

[0094] The above has introduced in detail an objective lens system and an endoscope provided by the present invention. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. An objective lens system for an endoscope, having a first observation state and a second observation state, wherein the magnification of the objective lens system in the first observation state is smaller than the magnification in the second observation state, and the field of view angle of the objective lens system in the first observation state is larger than the field of view angle in the second observation state, characterized in that, The objective lens system includes a first lens group, a diaphragm, a second lens group, a third lens group, and a fourth lens group arranged in sequence from the object side to the image side along the optical axis. The focal lengths of the first lens group and the fourth lens group are both negative, and the focal lengths of the second lens group and the third lens group are both positive; During the switching process of the objective lens system between the first observation state and the second observation state, the positions of the first lens group and the fourth lens group along the optical axis remain unchanged, and the second lens group and the third lens group move along the optical axis respectively for focusing; The objective lens system satisfies the following conditional expressions: w1≥65°, |β2|≥2.33; Wherein, w1 represents the half field of view angle of the objective lens system in the first observation state, and β2 represents the lateral magnification of the objective lens system in the second observation state.

2. The objective lens system according to claim 1, wherein During the switching process of the objective lens system between the first observation state and the second observation state, the diaphragm moves synchronously with the second lens group.

3. The objective lens system according to claim 2, wherein It also satisfies the following conditional expression: 0.01 ≤ △d 1ST / f1 ≤ 2.95, 0.14 ≤ △d 34 / f1 ≤ 3.50; Among them, f1 represents the focal length of the objective lens system in the first observation state, and △d 1ST represents the distance between the first lens group and the diaphragm along the optical axis, and △d 34 represents the distance between the third lens group and the fourth lens group along the optical axis.

4. The objective lens system according to claim 1, characterized in that, During the switching process of the objective lens system between the first observation state and the second observation state, the moving directions of the second lens group and the third lens group are the same.

5. The objective lens system according to claim 4, wherein, The objective lens system further has a third observation state; The magnification of the objective lens system in the third observation state is between the magnification in the first observation state and the magnification in the second observation state; The field of view angle of the objective lens system in the third observation state is between the field of view angle in the first observation state and the field of view angle in the second observation state.

6. The objective lens system according to claim 5, characterized in that, During the sequential switching process of the objective lens system between the first observation state, the third observation state, and the second observation state, the distance between the second lens group and the third lens group along the optical axis first increases and then decreases.

7. The objective lens system according to any one of claims 1 to 6, characterized in that, During the switching process of the objective lens system for the observation state, the back working distance of the objective lens system remains unchanged.

8. The objective lens system according to any one of claims 1 to 6, characterized in that, Both the second lens group and the third lens group include cemented lenses.

9. The objective lens system according to any one of claims 1 to 6, characterized in that, The first lens group includes a first lens, a second lens, and a third lens. The focal length of the first lens is negative, and the combined focal length of the second lens and the third lens is positive.

10. An endoscope, characterized in that, Comprising the objective lens system according to any one of claims 1 to 9.

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