Objective lens group, optical imaging system, and endoscope

Abstract

The utility model relates to an objective lens group, an optical imaging system and an endoscope. The objective lens group comprises a first cemented lens group, a second cemented lens group and a third cemented lens group, wherein the first cemented lens group sequentially comprises a first lens with negative focal power, a second lens with negative focal power, a fourth lens with positive focal power and a fifth lens with negative focal power from the object side to the image side along the optical axis; the second cemented lens group is arranged on the image side of the first cemented lens group and sequentially comprises a sixth lens with positive focal power, a seventh lens with negative focal power, an eighth lens with positive focal power, a ninth lens with negative focal power and a tenth lens with positive focal power from the object side to the image side along the optical axis; and an eleventh lens having a negative refractive power. By using the objective lens group and the optical imaging system, aberration such as distortion and chromatic aberration can be effectively corrected, and the endoscope has good imaging resolution and imaging quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of endoscopes, in particular to an objective lens group, an optical imaging system and an endoscope. BACKGROUND

[0002] An endoscope is a medical instrument capable of entering the inside of a patient for diagnosing or treating the inside of the patient, including various types of viewing scopes such as laparoscopes. Among them, a laparoscope usually includes an optical imaging system and a mechanical structure for supporting the optical imaging system. The optical imaging system usually includes an objective lens group, a rod lens group and an eyepiece group. The light collected by the objective lens group can be transmitted to the eyepiece group through the rod lens group and then be imaged on an image sensor. However, the imaging performance of the current laparoscope is not good, especially for ultra-high definition (4K) imaging, which is prone to distortion and chromatic aberration, affecting the comprehensiveness and accuracy of diagnosis and treatment. SUMMARY

[0003] Therefore, it is necessary to provide an objective lens group, an optical imaging system and an endoscope to solve the problem of poor imaging performance of the current laparoscope.

[0004] An objective lens group includes:

[0005] A first cemented lens group includes, in order from the object side to the image side along the optical axis, a first lens having a negative focal power, a second lens having a negative focal power, a fourth lens having a positive focal power, and a fifth lens having a negative focal power; and

[0006] A second cemented lens group is arranged on the image side of the first cemented lens group and includes, in order from the object side to the image side along the optical axis, a sixth lens having a positive focal power, a seventh lens having a negative focal power, an eighth lens having a positive focal power, a ninth lens having a negative focal power, a tenth lens having a positive focal power, and an eleventh lens having a negative focal power.

[0007] The objective lens group described above has a reasonable configuration of the focal power of each lens, cooperates with the design of the first lens to the fifth lens being cemented and the sixth lens to the eleventh lens being cemented, so that the light can be smoothly transitioned in the objective lens group, which is conducive to correcting aberrations such as distortion and chromatic aberration, reducing the aberration sensitivity and tolerance sensitivity of each lens in the objective lens group, thereby improving the imaging resolution and imaging quality of the objective lens group, which is conducive to improving the comprehensiveness and accuracy of diagnosis and treatment when applied to an endoscope, and also conducive to improving the molding yield and assembly yield of each lens.

[0008] In one of the embodiments, the first cemented lens group further includes a third deflection prism located between the second lens and the fourth lens along the optical axis, the third deflection prism being used for deflecting the optical path; and / or

[0009] The objective lens group further comprises an aperture stop, which is arranged between the third deflecting prism and the fourth lens.

[0010] In one of the embodiments, the object side surface of the first lens is convex, the image side surface of the first lens is concave, the image side surface of the second lens is concave, the image side surface of the fourth lens is convex, the object side surface of the fifth lens is concave, and the image side surface of the fifth lens is convex.

[0011] The object side surface and the image side surface of the sixth lens are both convex, the object side surface and the image side surface of the seventh lens are both concave, the object side surface and the image side surface of the eighth lens are both convex, the object side surface and the image side surface of the ninth lens are both concave, the object side surface and the image side surface of the tenth lens are both convex, and the object side surface of the eleventh lens is concave and the image side surface of the eleventh lens is convex.

[0012] In one of the embodiments, the objective lens group satisfies the following conditional expressions:

[0013] 2.99mm≤f(B01)≤4.04mm; and / or,

[0014] 34.67mm≤f(B02)≤46.91mm; and / or,

[0015] 1≤f(B02) / CT2≤1.5;

[0016] wherein f(B01) is the focal length of the first cemented lens group, f(B02) is the focal length of the second cemented lens group, and CT2 is the distance on the optical axis from the object side surface of the sixth lens to the image side surface of the eleventh lens.

[0017] In one of the embodiments, the object side surface and the image side surface of the first lens are aspherical; and / or,

[0018] The Abbe number of the seventh lens is smaller than the Abbe number of the sixth lens and the Abbe number of the eighth lens, the Abbe number of the ninth lens and the Abbe number of the eleventh lens are smaller than the Abbe number of the eighth lens, and the Abbe number of the tenth lens is smaller than the Abbe number of the ninth lens and the Abbe number of the eleventh lens.

[0019] An optical imaging system comprises, along the optical axis from the object side to the image side, an objective lens group according to any one of the above embodiments, a rod lens group, and an eyepiece group, the rod lens group is used to conduct at least part of the light rays emitted by the objective lens group to the eyepiece group, and the eyepiece group comprises a plurality of lenses with optical power and cemented together.

[0020] In one of the embodiments, the eyepiece group comprises, along the optical axis from the object side to the image side and in sequence and in sequence cemented, a fourteenth lens with negative optical power, a fifteenth lens with positive optical power, a sixteenth lens with negative optical power, a seventeenth lens with positive optical power, an eighteenth lens with negative optical power, a nineteenth lens with positive optical power, and a twentieth lens with positive optical power, the object side surface and the image side surface of the fourteenth lens are both concave, the object side surface and the image side surface of the fifteenth lens are both convex, the object side surface and the image side surface of the sixteenth lens are both concave, the object side surface and the image side surface of the seventeenth lens are both convex, the object side surface and the image side surface of the eighteenth lens are both concave, the object side surface of the nineteenth lens is convex, and the image side surface is concave, and the object side surface and the image side surface of the twentieth lens are both convex.

[0021] In one of the embodiments, the rod lens group comprises a plurality of relay lens groups arranged along the optical axis in sequence, the relay lens group comprises a third cemented lens group and a symmetrical lens group arranged on the image side of the third cemented lens group, the symmetrical lens group and the third cemented lens group are arranged in mirror symmetry about a plane perpendicular to the optical axis, the third cemented lens group comprises a twelfth lens with positive optical power and a thirteenth lens with negative optical power arranged on the image side of the twelfth lens, the object side surface and the image side surface of the twelfth lens are both convex, the object side surface of the thirteenth lens is concave, and the image side surface is convex.

[0022] In one of the embodiments, the optical imaging system satisfies the following conditional expression:

[0023] 18.74mm≤f(B03)≤25.36mm;

[0024] 1mm≤T3≤21.7mm, 1mm≤T4≤19.2mm;

[0025] f(B04)≤18.58mm;

[0026] 0.6≤f(B04) / CT4≤1;

[0027] 2.3mm≤f(object)≤3.4mm, 0.43mm≤D≤0.6mm;

[0028] wherein f(B03) is the focal length of the third cemented lens group, T3 is the air gap on the optical axis between the third cemented lens group and the symmetrical lens group in any one of the relay lens groups, T4 is the air gap on the optical axis between two adjacent relay lens groups, f(B04) is the focal length of the eyepiece group, CT4 is the distance on the optical axis from the object side surface of the fourteenth lens to the image side surface of the twentieth lens, f(object) is the focal length of the objective lens group, and D is the entrance pupil diameter of the optical imaging system; and / or,

[0029] The Abbe number of the fifteenth lens is smaller than the Abbe numbers of the fourteenth and sixteenth lenses, the Abbe number of the sixteenth lens is smaller than the Abbe numbers of the fourteenth and seventeenth lenses, the Abbe number of the eighteenth lens is smaller than the Abbe numbers of the seventeenth and nineteenth lenses, and the Abbe number of the nineteenth lens is smaller than the Abbe number of the seventeenth lens and larger than the Abbe number of the twentieth lens.

[0030] An endoscope comprising the optical imaging system as described in any of the above embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A structural diagram of the optical imaging system in some embodiments.

[0032] Figure 2 A structural diagram of the objective lens group in some embodiments.

[0033] Figure 3 A structural diagram of the rod lens group in some embodiments.

[0034] Figure 4 A structural diagram of the eyepiece lens group in some embodiments.

[0035] Figure 5 A modulation transfer function (MTF) curve of the optical imaging system in some embodiments.

[0036] Figure 6 A relative illuminance diagram of the optical imaging system in some embodiments.

[0037] Figure 7 A field curvature and distortion curve of the optical imaging system in some embodiments.

[0038] Figure 8 A spot diagram of the optical imaging system in some embodiments.

[0039] Figure 9 A lateral color curve of the optical imaging system in some embodiments.

[0040] REFERENCE NUMERALS:

[0041] 100, optical imaging system; 110, objective group; 111, first cemented lens group; 1, first lens; 2, second lens; 3, third deflecting prism; 4, fourth lens; 5, fifth lens; 112, second cemented lens group; 6, sixth lens; 7, seventh lens; 8, eighth lens; 9, ninth lens; 10, tenth lens; 11, eleventh lens; 120, rod lens group; 121, third cemented lens group; 12, twelfth lens; 13, thirteenth lens; 122, symmetrical lens group; 130, eyepiece group; 14, fourteenth lens; 15, fifteenth lens; 16, sixteenth lens; 17, seventeenth lens; 18, eighteenth lens; 19, nineteenth lens; 20, twentieth lens; 21, first protective element; 22, second protective element. DETAILED DESCRIPTION

[0042] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, a lot of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many different ways other than those described herein, and one of ordinary skill in the art can make similar improvements without departing from the spirit of the present application, and therefore the present application is not limited to the specific embodiments disclosed below.

[0043] In the description of the present application, it should be understood that if there are terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0044] In addition, if the terms "first", "second" appear, these terms are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features referred to. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, if the term "a plurality of" appears, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0045] In the present application, unless specifically defined otherwise, if there is any appearance of the terms "mount", "connect", "connection", "fixed", and the like, these terms should be interpreted broadly. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically defined. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0046] In the present application, unless specifically defined otherwise, if there is any appearance of the terms "mount", "connect", "connection", "fixed", and the like, these terms should be interpreted broadly. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically defined. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0047] It should be noted that if an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there can be a middle element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there can be a middle element. If present, the terms "vertical", "horizontal", "up", "down", "left", "right", and similar expressions used in the present application are for illustrative purposes only and do not represent the only implementation.

[0048] Please refer to Figure 1 , Figure 1 The structural schematic diagram of the optical imaging system 100 in some embodiments of the present application is shown. The optical imaging system 100 provided by the present application can be used in medical instruments, for example, in any applicable endoscope such as a laparoscope. When the insertion part of the endoscope is inserted into the patient's body, the optical imaging system 100 can collect images of the lesion area, so as to facilitate the doctor to diagnose or treat the lesion area. The endoscope can also include a housing, and the optical imaging system 100 is arranged in the housing, which can be understood as the support structure of the optical imaging system 100. In combination with Figure 2 、 Figure 3 and Figure 4As shown in some embodiments, the optical imaging system 100 comprises, along the optical axis from the object side to the image side, an objective lens group 110, a rod lens group 120 and an eyepiece lens group 130 in sequence, the objective lens group 110 is configured to collect and adjust light, the rod lens group 120 is configured to transmit the light collected by the objective lens group 110 to the eyepiece lens group 130, and the eyepiece lens group 130 is configured to transmit the light adjusted by the eyepiece lens group 130 to an imaging surface.

[0049] Further, in combination with Figure 1 and Figure 2 As shown in some embodiments, the objective lens group 110 comprises a first cemented lens group 111 and a second cemented lens group 112 arranged on the image side of the first cemented lens group 111, the first cemented lens group 111 comprises, along the optical axis from the object side to the image side, a first lens 1 with negative refractive power, a second lens 2 with negative refractive power, a fourth lens 4 with positive refractive power, and a fifth lens 5 with negative refractive power, and the first lens 1, the second lens 2, the fourth lens 4 and the fifth lens 5 are cemented in sequence. The second cemented lens group 112 comprises, along the optical axis from the object side to the image side, a sixth lens 6 with positive refractive power, a seventh lens 7 with negative refractive power, an eighth lens 8 with positive refractive power, a ninth lens 9 with negative refractive power, a tenth lens 10 with positive refractive power, and an eleventh lens 11 with negative refractive power, and the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, the tenth lens 10 and the eleventh lens 11 are cemented in sequence.

[0050] In some embodiments, the object side surface of the first lens 1 is convex, the image side surface is concave, the image side surface of the second lens 2 is concave, the image side surface of the fourth lens 4 is convex, the object side surface of the fifth lens 5 is concave, and the image side surface is convex; the object side surface and the image side surface of the sixth lens 6 are both convex, the object side surface and the image side surface of the seventh lens 7 are both concave, the object side surface and the image side surface of the eighth lens 8 are both convex, the object side surface and the image side surface of the ninth lens 9 are both concave, the object side surface and the image side surface of the tenth lens 10 are both convex, the object side surface of the eleventh lens 11 is concave, and the image side surface is convex.

[0051] The above objective lens group 110, the optical power of each lens can be reasonably configured, and the design of the first lens 1 to the fifth lens 5 is glued, and the sixth lens 6 to the eleventh lens 11 is glued, so that the light can be smoothly transitioned in the objective lens group 110, which is beneficial to correct aberrations such as distortion, chromatic aberration, etc., reduce the aberration sensitivity and tolerance sensitivity of each lens in the objective lens group 110, thereby improving the imaging resolution and imaging quality of the objective lens group 110, and when applied to an endoscope, it is beneficial to improve the comprehensiveness and accuracy of diagnosis and treatment, and also beneficial to improve the molding yield and assembly yield of each lens. The setting of the two groups of glued prisms is also beneficial to improve the compactness of the structure of the objective lens group 110, which is beneficial to compress the axial size of the objective lens group 110. Specifically, the negative optical power and surface shape design of the first lens 1 and the second lens 2 cooperate to bend and converge the light rays with large angles, which is beneficial to reduce the effective aperture of the lens, thereby facilitating the small head design of the endoscope, reducing the damage to the patient by the endoscope, and also beneficial to suppress the aberrations such as distortion of large angle, and improve the imaging quality of the objective lens group 110. In addition, it is also beneficial to reduce the burden of the second lens 2 and each lens on the image side for deflecting light rays, reduce the aberration sensitivity and tolerance sensitivity of the objective lens group 110, reduce the surface shape complexity of each lens, and improve the molding yield of each lens. The optical power and surface shape of each lens on the image side of the second lens 2 cooperate to smoothly transition the light, correct aberrations such as distortion, chromatic aberration, etc., reduce the aberration sensitivity, and improve the imaging quality.

[0052] In some embodiments, the first glued lens group 111 further includes a third deflection prism 3 located between the second lens 2 and the fourth lens 4 along the optical axis, and the two sides of the third deflection prism 3 are glued with the second lens 2 and the fourth lens 4 respectively. The third deflection prism 3 is used to deflect the light path, so that the light collected by the first lens 1 and the second lens 2 can be deflected by a certain angle and then shot to each lens on the image side, which is beneficial to expand the viewing angle of the objective lens group 110 to adapt to different shooting angles. It should be noted that in Figure 1 and Figure 2 In the above embodiments, the third deflection prism 3 is represented by a flat glass, and in fact, the third deflection prism 3 can be composed of one or more prisms, and the third deflection prism 3 can deflect the light path by one or more reflections. The deflection angle of the third deflection prism 3 includes but is not limited to 0°, 30°, 70°, etc., so that the objective lens group 110 can have a corresponding viewing angle. When the viewing angle of the objective lens group 110 is 0°, the third deflection prism 3 can adopt a flat glass.

[0053] In some embodiments, the object side surface of the second lens 2 is planar, and the object side surface of the fourth lens 4 is planar, and the object side surface of the fourth lens 4 can be attached to and glued with the image side surface of the third deflecting prism 3, thereby facilitating the abutting, positioning and fixing design of the lenses in the objective lens group 110, and facilitating the improvement of the assembly yield and structural reliability of the objective lens group 110.

[0054] In some embodiments, the objective lens group 110 further comprises an aperture stop, which is arranged between the third deflecting prism 3 and the fourth lens 4, for example, on the image side surface of the third deflecting prism 3. The design of the aperture stop in front can reasonably control the light path of the light in combination with the power and surface type design of each lens, thereby facilitating the reduction of the aperture of the optical imaging system 100 and improving the structural compactness of the optical imaging system 100, so as to facilitate the reduction of the maximum insertion width of the endoscope when the optical imaging system 100 is applied to the endoscope, and the harm to the patient.

[0055] In some embodiments, the object side surface and the image side surface of the first lens 1 are aspherical surfaces, and the aspherical lens is used as the first lens 1. The surface type of the first lens 1 has higher design flexibility in the direction perpendicular to the axial direction, can adapt to different field angles, effectively suppresses the aberrations such as distortion at large angles, improves the imaging quality of the objective lens group 110, and meets the requirements of doctors on the imaging reality. In some embodiments, the object side surface and the image side surface of each lens in the optical imaging system 100 except the first lens 1 can be spherical surfaces, which is conducive to reducing the design and forming difficulty of each lens, and also conducive to compressing the radial size of the optical imaging system 100.

[0056] In some embodiments, the Abbe number of the seventh lens 7 is smaller than the Abbe number of the sixth lens 6 and the eighth lens 8, the Abbe number of the ninth lens 9 and the eleventh lens 11 is smaller than the Abbe number of the eighth lens 8, and the Abbe number of the tenth lens 10 is smaller than the Abbe number of the ninth lens 9 and the eleventh lens 11. By matching the Abbe number of each lens in the second glued lens group 112, in combination with the power and surface type design of each lens in the second glued lens group 112, the correction effect of chromatic aberration is improved, thereby improving the imaging quality of the objective lens group 110. In some embodiments, the Abbe number of the sixth lens 6 is 61, the Abbe number of the seventh lens 7 is 26, the Abbe number of the eighth lens 8 is 55, the Abbe number of the ninth lens 9 is 32, the Abbe number of the tenth lens 10 is 28, and the Abbe number of the eleventh lens 11 is 39.

[0057] In some embodiments, the objective lens group 110 satisfies the condition formula: 2.99mm≤f(B01)≤4.04mm, where f(B01) is the focal length of the first cemented lens group 111. When the above condition formula is satisfied, the focal length of the first cemented lens group 111 can be reasonably configured, and the power and surface profile of each lens in the first cemented lens group 111 are designed to enable the first cemented lens group 111 to effectively collect light while enabling the light to transition smoothly, thereby suppressing aberrations such as distortion, while also facilitating a reduction in the burden on the second cemented lens group 112 to deflect light, facilitating a reduction in the aberration sensitivity and tolerance sensitivity of each lens in the second cemented lens group 112, improving the imaging quality of the objective lens group 110, and facilitating a reduction in the surface profile complexity of each lens and improving the molding yield of each lens.

[0058] In some embodiments, the objective lens group 110 satisfies the condition formula: 34.67mm≤f(B02)≤46.91mm; 1≤f(B02) / CT2≤1.5; where f(B02) is the focal length of the second cemented lens group 112, and CT2 is the distance on the optical axis from the object side surface of the sixth lens 6 to the image side surface of the eleventh lens 11, i.e., the thickness of the second cemented lens group 112 on the optical axis. Satisfying the above condition formula enables the focal length of the second cemented lens group 112 and the ratio of the focal length of the second cemented lens group 112 to the central thickness to be reasonably configured, in combination with the power and surface profile of each lens in the second cemented lens group 112, to facilitate the smooth transition of light collected by the first cemented lens group 111 in the second cemented lens group 112, suppress the generation of aberrations such as distortion and chromatic aberration, thereby facilitating an improvement in the imaging quality of the objective lens group 110, while also facilitating a reduction in the axial size of the objective lens group 110 and facilitating the miniaturization design of the endoscope.

[0059] In combination with FIGS. 1A and 1B, Figure 1 and Figure 3 As shown in FIGS. 1A and 1B, in some embodiments, the rod lens group 120 includes a plurality of relay lens groups arranged in sequence along the optical axis, and the number of relay lens groups is odd, for example, the rod lens group 120 can include three relay lens groups. Each relay lens group includes a third cemented lens group 121 and a symmetrical lens group 122 arranged on the image side of the third cemented lens group 121, and the symmetrical lens group 122 is arranged in mirror symmetry with the third cemented lens group 121 about a plane perpendicular to the optical axis, and the third cemented lens group 121 and the symmetrical lens group 122 are arranged in sequence along the optical axis. Figure 1 and Figure 3Only one of the third cemented lens groups 121 and one of the symmetric lens groups 122 in the rod lens group 120 are shown. The symmetric third cemented lens groups 121 and symmetric lens groups 122 are arranged in the rod lens group 120 so that the magnification of the rod lens group 120 is -1, which can achieve equal-scale image transmission, and also can make the sizes of the off-axis aberrations such as the off-axis chromatic aberration, the coma, and the distortion of the third cemented lens groups 121 and the symmetric lens groups 122 equal, and the positive and negative signs opposite, which can offset each other, thereby reducing the aberration introduced by the rod lens group 120 in the image transmission process and improving the imaging quality of the optical imaging system 100. The reasonable arrangement of the rod lens group 120 is also conducive to controlling the effective aperture size of the optical imaging system 100 and the maximum insertion width of the endoscope, which can not only make the optical imaging system 100 have sufficient light quantity, but also be conducive to reducing the maximum insertion width of the endoscope, for example, making the maximum insertion width of the endoscope less than or equal to 10 mm, thereby reducing the harm to the patient.

[0060] In some embodiments, the third cemented lens group 121 includes a twelfth lens 12 with positive refractive power, and a thirteenth lens 13 with negative refractive power arranged on the image side of the twelfth lens 12. The object side surface and the image side surface of the twelfth lens 12 are both convex, the object side surface of the thirteenth lens 13 is concave, and the image side surface of the thirteenth lens 13 is convex. By reasonably configuring the refractive power and surface type of each lens in the rod lens group 120, the lenses in the third cemented lens group 121 and the symmetric lens group 122 have reasonable positive and negative combinations, which is conducive to reducing the Petzval sum and the spherical aberration, and improving the light energy transmission efficiency of the rod lens group 120, thereby improving the imaging quality and brightness of the optical imaging system 100.

[0061] In combination Figure 1 and Figure 4 As shown in FIGS. 13 and 14, in some embodiments, the eyepiece group 130 includes, along the optical axis from the object side to the image side, a fourteenth lens 14 with negative refractive power, a fifteenth lens 15 with positive refractive power, a sixteenth lens 16 with negative refractive power, a seventeenth lens 17 with positive refractive power, an eighteenth lens 18 with negative refractive power, a nineteenth lens 19 with positive refractive power, and a twentieth lens 20 with positive refractive power. The object side surface and the image side surface of the fourteenth lens 14 are both concave, the object side surface and the image side surface of the fifteenth lens 15 are both convex, the object side surface and the image side surface of the sixteenth lens 16 are both concave, the object side surface and the image side surface of the seventeenth lens 17 are both convex, the object side surface and the image side surface of the eighteenth lens 18 are both concave, the object side surface of the nineteenth lens 19 is convex, and the image side surface of the nineteenth lens 19 is concave. The object side surface and the image side surface of the twentieth lens 20 are both convex. The fourteenth lens 14, the fifteenth lens 15, the sixteenth lens 16, the seventeenth lens 17, the eighteenth lens 18, the nineteenth lens 19, and the twentieth lens 20 are cemented in sequence.

[0062] In the above eyepiece group 130, the optical power and surface shape of each lens are reasonably configured, and the design of the cementing of each lens can smoothly transition the light collected by the objective lens group 110, so that the light is smoothly transitioned, which is beneficial to suppress aberrations such as distortion, chromatic aberration, and the like, and to improve the imaging quality. Among them, the alternating design of the positive and negative optical power of the fourteenth lens 14 to the twentieth lens 20, in cooperation with the surface shape design of each lens, is beneficial to control the trend of the light, balance the optical power proportion of each part of the eyepiece group 130, avoid excessive convergence or excessive divergence of the light, and is beneficial to correct various aberrations such as spherical aberration, chromatic aberration, and the like, and to improve the imaging quality of the eyepiece group 130. The positive optical power and double-convex surface shape design of the twentieth lens 20 cooperates with the optical power and surface shape design of the other lenses, which can effectively converge the light onto the imaging surface, is beneficial to improve the brightness and contrast of the imaging, and thus improves the imaging quality of the eyepiece group 130.

[0063] At the same time, through the reasonable configuration of the optical power and surface shape of each lens in the objective lens group 110 and the eyepiece group 130, the objective lens group 110 has negative distortion, and the eyepiece group 130 has positive distortion, which can offset the negative distortion of the objective lens group 110, which is beneficial to suppress the distortion of the optical imaging system 100, for example, to control the distortion of the optical imaging system 100 within -3.3%, thereby improving the imaging quality of the optical imaging system 100. The reasonable collocation of the objective lens group 110, the eyepiece group 130 and the rod lens group 120 can make the optical imaging system 100 correct the aberrations of the visible light band 435nm-656nm well, and can meet the high-definition imaging of the 1 / 1.8 inch image sensor.

[0064] In some embodiments, the Abbe number of the fifteenth lens 15 is smaller than the Abbe number of the fourteenth lens 14 and the sixteenth lens 16, the Abbe number of the sixteenth lens 16 is smaller than the Abbe number of the fourteenth lens 14 and the seventeenth lens 17, the Abbe number of the eighteenth lens 18 is smaller than the Abbe number of the seventeenth lens 17 and the nineteenth lens 19, and the Abbe number of the nineteenth lens 19 is smaller than the Abbe number of the seventeenth lens 17 and larger than the Abbe number of the twentieth lens 20. Through the collocation design of the Abbe number of each lens in the eyepiece group 130, in cooperation with the cementing design and the design of the optical power and surface shape of each lens in the eyepiece group 130, it is beneficial to improve the correction ability of the eyepiece group 130 to chromatic aberration, thereby improving the imaging quality of the optical imaging system 100. In some embodiments, the Abbe number of the fourteenth lens 14 is 70, the Abbe number of the fifteenth lens 15 is 24, the Abbe number of the sixteenth lens 16 is 36, the Abbe number of the seventeenth lens 17 is 70, the Abbe number of the eighteenth lens 18 is 28, the Abbe number of the nineteenth lens 19 is 56, and the Abbe number of the twentieth lens 20 is 39.

[0065] In some embodiments, the optical imaging system 100 satisfies the condition formula: f(B04)≤18.58 mm; 0.6≤f(B04) / CT4≤1; wherein f(B04) is the focal length of the eyepiece group 130, and CT4 is the distance on the optical axis from the object side surface of the fourteenth lens 14 to the image side surface of the twentieth lens 20, i.e., the thickness of the eyepiece group 130 on the optical axis. Satisfying the above condition formula, in combination with the reasonable configuration of the optical power and surface shape of each lens in the eyepiece group 130, the eyepiece group 130 can smoothly transition the light rays collected by the objective lens group 110, and inhibit the generation of various aberrations such as distortion, chromatic aberration, and the like, thereby being conducive to improving the imaging quality of the optical imaging system 100, while also being conducive to reducing the axial dimension of the eyepiece group 130, and being conducive to the miniaturization design of the endoscope.

[0066] In some embodiments, the optical imaging system 100 satisfies the condition formula: 18.74 mm≤f(B03)≤25.36 mm; 1 mm≤T3≤21.7 mm, 1 mm≤T4≤19.2 mm; wherein f(B03) is the focal length of the third cemented lens group 121, T3 is the air gap on the optical axis between the third cemented lens group 121 and the symmetric lens group 122 in any conducting lens group, and T4 is the air gap on the optical axis between two adjacent conducting lens groups. When the above condition formula is satisfied, the focal length and spacing of the third cemented lens group 121 and the symmetric lens group 122 can be reasonably configured, so that the rod lens group 120 can smoothly conduct light rays and inhibit the introduction of aberrations in the image transmission process of the rod lens group 120, thereby improving the imaging quality of the optical imaging system 100, while also being conducive to compressing the axial dimension of the rod lens group 120.

[0067] Please refer again to Figure 1 In some embodiments, the optical imaging system 100 further includes a first protective element 21 arranged on the object side of the first lens 1 and a second protective element 22 arranged on the image side of the twentieth lens 20, and the first protective element 21 and the second protective element 22 each include but are not limited to a flat glass, and the first protective element 21 and the second protective element 22 can provide structural protection for the lenses in the objective lens group 110 and the eyepiece group 130.

[0068] In some embodiments, the entrance pupil diameter D of the optical imaging system 100 is 0.43 mm-0.6 mm, so that the optical imaging system 100 can have sufficient light intake to meet the high-quality imaging requirements, for example, the full-field contrast can be greater than 0.29 when the resolution satisfies 70 lp / mm. In some embodiments, the focal length f(object) of the objective lens group 110 is 2.3 mm-3.4 mm, which in combination with the design of the entrance pupil diameter can effectively improve the depth of field range of the optical imaging system 100, for example, the depth of field range of the optical imaging system 100 is improved to 10 mm-∞ (infinity), which can clearly image a larger range of subjects, and improve the comprehensiveness of diagnosis and treatment.

[0069] In some embodiments, the focal length of the eyepiece group 130 is less than or equal to 18.58mm, which forms a good match with the objective lens group 110, and can meet the full-screen imaging of a 1 / 1.8 inch image sensor, thereby improving the imaging quality of the optical imaging system 100. In some embodiments, the optical working distance of the optical imaging system 100 is 40mm, the working length is 315mm-325mm, and the field of view angle is greater than 80°, which is conducive to improving the shooting range of the optical imaging system 100, and is also conducive to improving the comprehensiveness of diagnosis and treatment.

[0070] Please refer to Figures 5-9 shown, Figure 5 is a modulation transfer function (MTF) curve of the optical imaging system 100 in some embodiments, Figure 6 is a relative luminance diagram of the optical imaging system 100 in some embodiments, Figure 7 is a field curvature and distortion curve of the optical imaging system 100 in some embodiments, Figure 8 is a spot column diagram of the optical imaging system 100 in some embodiments, Figure 9 is a lateral color curve of the optical imaging system 100 in some embodiments. By Figures 5-9 It can be seen that, under visible light (0.435um-0.656um), when the resolution of the optical imaging system 100 meets 70lp / mm, the full-field MTF value is greater than 0.31, and is close to the diffraction limit; the edge field relative luminance is greater than 90%, the field has no dark angle; the distortion is controlled within-3.3%, the picture has small deformation with the actual scene; the diffraction spot in the spot column diagram is smaller than the Airy disk, and the spot diameter is contained in the Airy disk, which is basically at the diffraction limit, the short-wave and long-wave chromatic aberrations are concentrated, and the optical imaging system 100 has good imaging quality and imaging brightness.

[0071] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present disclosure.

[0072] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. An objective lens group, characterized by comprising: The objective lens group comprises: a first cemented lens group comprising, along an optical axis from an object side to an image side, a first lens having negative refractive power, a second lens having negative refractive power, a fourth lens having positive refractive power, and a fifth lens having negative refractive power; and a second cemented lens group arranged on the image side of the first cemented lens group and comprising, along the optical axis from the object side to the image side, a sixth lens having positive refractive power, a seventh lens having negative refractive power, an eighth lens having positive refractive power, a ninth lens having negative refractive power, a tenth lens having positive refractive power, and an eleventh lens having negative refractive power. The first cemented lens group further comprises a third deflection prism arranged between the second lens and the fourth lens along the optical axis, the third deflection prism being used for deflecting the optical path; and / or 2. The objective lens group according to claim 1, characterized in that The objective lens group further comprises an aperture stop arranged between the third deflection prism and the fourth lens. The object side surface of the first lens is convex, and the image side surface of the first lens is concave; the image side surface of the second lens is concave; the image side surface of the fourth lens is convex; the object side surface of the fifth lens is concave, and the image side surface of the fifth lens is convex; 3. The objective lens group according to claim 1, characterized in that The object side surface and the image side surface of the sixth lens are both convex; the object side surface and the image side surface of the seventh lens are both concave; the object side surface and the image side surface of the eighth lens are both convex; the object side surface and the image side surface of the ninth lens are both concave; the object side surface and the image side surface of the tenth lens are both convex; the object side surface of the eleventh lens is concave, and the image side surface of the eleventh lens is convex. The objective lens group satisfies the following conditional expressions:

4. The objective lens group according to claim 1, characterized in that, 2.99mm≤f(B01)≤4.04mm; and / or 34.67mm≤f(B02)≤46.91mm; and / or 1≤f(B02) / CT2≤1.5; wherein f(B01) is the focal length of the first cemented lens group, f(B02) is the focal length of the second cemented lens group, and CT2 is the distance from the object side surface of the sixth lens to the image side surface of the eleventh lens along the optical axis. The object side surface and the image side surface of the first lens are aspheric surfaces; and / or 5. The objective lens group according to claim 1, characterized in that, The Abbe number of the seventh lens is smaller than the Abbe number of the sixth lens and the Abbe number of the eighth lens, the Abbe number of the ninth lens and the Abbe number of the eleventh lens are smaller than the Abbe number of the eighth lens, and the Abbe number of the tenth lens is smaller than the Abbe number of the ninth lens and the Abbe number of the eleventh lens. The objective lens group comprises, along an optical axis from an object side to an image side, an objective lens group, a rod lens group, and an eyepiece group in sequence, the rod lens group is used for conducting at least part of the light rays emitted by the objective lens group to the eyepiece group, and the eyepiece group comprises a plurality of lenses having refractive power and being cemented.

6. An optical imaging system characterized by, ​ 7. The optical imaging system of claim 6, wherein, The eyepiece group comprises, along the optical axis from the object side to the image side and in sequence and in sequence cemented, a fourteenth lens with negative refractive power, a fifteenth lens with positive refractive power, a sixteenth lens with negative refractive power, a seventeenth lens with positive refractive power, an eighteenth lens with negative refractive power, a nineteenth lens with positive refractive power, and a twentieth lens with positive refractive power, the object side and the image side of the fourteenth lens are both concave, the object side and the image side of the fifteenth lens are both convex, the object side and the image side of the sixteenth lens are both concave, the object side and the image side of the seventeenth lens are both convex, the object side and the image side of the eighteenth lens are both concave, the object side of the nineteenth lens is convex, and the image side is concave, and the object side and the image side of the twentieth lens are both convex.

8. The optical imaging system of claim 7, wherein, The rod lens group comprises a plurality of transmission lens groups arranged along the optical axis in sequence, the transmission lens group comprises a third cemented lens group and a symmetrical lens group arranged on the image side of the third cemented lens group, the symmetrical lens group and the third cemented lens group are arranged in mirror symmetry about a plane perpendicular to the optical axis, the third cemented lens group comprises a twelfth lens with positive refractive power and a thirteenth lens with negative refractive power arranged on the image side of the twelfth lens, the object side and the image side of the twelfth lens are both convex, the object side of the thirteenth lens is concave, and the image side is convex.

9. The optical imaging system of claim 8, wherein, The optical imaging system satisfies the following conditional expressions: 18.74mm≤f(B03)≤25.36mm; 1mm≤T3≤21.7mm, 1mm≤T4≤19.2mm; f(B04)≤18.58mm; 0.6≤f(B04) / CT4≤1; 2.3mm≤f(object)≤3.4mm, 0.43mm≤D≤0.6mm; Wherein, f(B03) is the focal length of the third cemented lens group, T3 is the air gap between the third cemented lens group and the symmetrical lens group in any transmission lens group on the optical axis, T4 is the air gap between adjacent two transmission lens groups on the optical axis, f(B04) is the focal length of the eyepiece group, CT4 is the distance from the object side of the fourteenth lens to the image side of the twentieth lens on the optical axis, f(object) is the focal length of the objective lens group, and D is the entrance pupil diameter of the optical imaging system; and / or, The Abbe number of the fifteenth lens is smaller than the Abbe number of the fourteenth lens and the sixteenth lens, the Abbe number of the sixteenth lens is smaller than the Abbe number of the fourteenth lens and the seventeenth lens, the Abbe number of the eighteenth lens is smaller than the Abbe number of the seventeenth lens and the nineteenth lens, and the Abbe number of the nineteenth lens is smaller than the Abbe number of the seventeenth lens and greater than the Abbe number of the twentieth lens.

10. An endoscope characterized by comprising: An optical imaging system as claimed in any one of claims 6-9. An optical imaging system as claimed in any one of claims 6-9.

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