A micro endoscope objective lens

Abstract

The present invention discloses a micro-endoscopic microscope objective lens, which belongs to the technical field of endoscopes and comprises an optical system, wherein the optical system comprises a first lens group, a second lens group, a third lens group and an imaging surface, which are sequentially arranged from the object side to the image side; wherein the first lens group has positive focal power, and its image side surface is a convex surface; the second lens group has positive focal power, its object side surface is a convex surface, and both its object side surface and image side surface are aspherical surfaces; the third lens group has negative focal power, its object side surface is a concave surface, its image side surface is a convex surface, and both its object side surface and image side surface are aspherical surfaces; light rays sequentially pass through the first lens group, the second lens and the third lens and are imaged on the imaging surface; the three-piece design greatly reduces the difficulty of processing and assembly, and can meet the requirements of reducing the size of the device and increasing the working distance of the device while ensuring the imaging quality.

Description

Technical Field

[0001] The invention belongs to the technical field of endoscopes, and in particular relates to a miniature endoscope microscope objective lens. Background Art

[0002] Microendoscopes are widely used in industrial and medical fields. For example, in the aerospace field, they are used for internal engine inspection and fuselage structure exploration (such as detecting cracks in turbine blades, fuel pipe blockages, etc.); in the medical field, they are used for early gastrointestinal cancer screening and optical biopsy.

[0003] With the continuous development of the application fields and scenarios of microendoscopes, the miniaturization of the micro-objective lens components at the front end of flexible fiber optic endoscopes has become increasingly prominent. Excessive optical length of the micromicroscope will lead to an excessively long rigid structure at the front end of the flexible endoscope, increasing the difficulty of passing the instrument through narrow or curved channels and reducing its operational flexibility in complex structures, thereby affecting the operator's ability to perform fine manipulation. At the same time, the increase in front end length increases the risk of accidental damage to the internal structure of the surrounding test object.

[0004] Existing micromicroscopes often use gradient refractive index (GRIN) lenses to achieve miniaturization. However, a single GRIN lens has poor aberration correction capabilities and is often used in combination. For example, a plano-convex lens combined with two GRIN lenses forms a micro-objective lens. The outer diameter is typically 0.2-2 mm, enabling micron-level resolution, but the working distance is less than 200 μm. Furthermore, the combination of GRIN lenses increases system length, resulting in excessively long rigid structures.

[0005] In addition to using GRIN lenses to design micro microscopes, lens combinations are also often used to design micro objective lenses. For example, a four-lens combination is used, in which one surface of the double-cemented lens is aspherical, and one surface of the convex lens is aspherical and the other surface is binary. The maximum aperture is 2.2mm, the total length of the system is 8.8mm, and the working distance is 300μm. However, this objective lens is difficult to process. Another example is the use of four spherical lenses. The outer diameter of the objective lens group is less than 1mm, and the total length of the optical system is less than 6mm. However, the working distance is only 40~80μm, which makes it difficult to see the deeper morphology of the endoscopic test object, and it will cause the endoscope to be used too close, increasing the risk of damage to the test object. Summary of the Invention

[0006] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a miniature endoscopic microscope objective lens, which can effectively shorten the mechanical size of the endoscopic microscope objective lens and increase the working distance of the microscope objective lens.

[0007] To achieve the above object, the present invention provides a micro-endoscopic microscope objective lens, which includes an optical system, wherein the optical system includes a first lens group, a second lens group, a third lens group, and an imaging surface, which are sequentially arranged from the object side to the image side;

[0008] The first lens group has positive optical power and its image side surface is convex;

[0009] The second lens group has positive refractive power, its object side surface is convex, and its object side surface and image side surface are both aspherical;

[0010] The third lens group has negative optical power, its object side surface is concave, its image side surface is convex, and both its object side surface and image side surface are aspherical;

[0011] The light is imaged on the imaging surface after passing through the first lens group, the second lens and the third lens in sequence.

[0012] As a further improvement of the present invention, the aspheric surface shape of the inner lens of the micro-endoscopic microscope objective lens satisfies:

[0013] (1)

[0014] in, Indicates the distance of the surface from the vertex in the direction of the optical axis. represents the curvature of the surface vertex, represents the conic coefficient of the quadratic surface, represents the distance from the optical axis to the surface, 、 、 and Represent the fourth-order, sixth-order, eighth-order and tenth-order surface coefficients respectively.

[0015] As a further improvement of the present invention, the second lens group satisfies:

[0016] (2)

[0017] in, is the effective aperture of the second lens group on the object side, is the distance from the object plane to the object side surface of the second lens group along the optical axis.

[0018] As a further improvement of the present invention, the optical system satisfies:

[0019] (3)

[0020] in, TTL is the total length of the optical system, i.e., the distance from the object side of the first lens group to the imaging surface along the optical axis; FFLis the working distance of the optical system, i.e., the distance from the object plane to the object side surface of the first lens group along the optical axis.

[0021] As a further improvement of the present invention, the optical system satisfies:

[0022] (4).

[0023] As a further improvement of the present invention, the optical system satisfies:

[0024] (5)

[0025] in, is the edge distance between the image-side surface of the first lens group and the object-side surface of the second lens group, It is the center distance between the image-side surface of the first lens group and the object-side surface of the second lens group, that is, the distance along the optical axis.

[0026] As a further improvement of the present invention, the optical system satisfies:

[0027] (6)

[0028] in, is the edge distance between the image-side surface and the object-side surface of the third lens group, is the center distance between the image-side surface and the object-side surface of the third lens group.

[0029] As a further improvement of the present invention, the optical system further satisfies:

[0030] (7)

[0031] (8)

[0032] (9)

[0033] (10)

[0034] in, R is the radius of curvature of all lenses in the lens group; is the center thickness of all lenses in the lens group; is the edge thickness of all lenses in the lens group; is the edge thickness of the spacing between all lenses in the lens group.

[0035] As a further improvement of the present invention, the first lens group includes a first lens; the second lens group includes a second lens; and the third lens group includes a third lens; or, the first lens group includes a fourth lens and a first lens arranged in sequence from the object side to the image side, the fourth lens is made of optical glass, the first lens is made of optical plastic, and the first lens group is composed of the fourth lens and the first lens cemented together.

[0036] As a further improvement of the present invention, the refractive index of the working environment between the object side and the object plane of the first lens group is 1.34;

[0037] and / or,

[0038] The first lens group, the second lens group and the third lens group are made of optical glass or optical plastic.

[0039] The above-mentioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0040] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0041] (1) The micro endoscope objective lens of the present invention greatly reduces the difficulty of processing and assembly through the three-piece design of the first lens group, the second lens group and the third lens group. The two convex lenses formed by the combination of the two convex lenses and the meniscus lens can realize the separation and correction of field curvature of positive and negative optical focal lengths. The spherical aberration can be well corrected by utilizing the coordination between the aspheric surfaces. At the same time, the tolerance sensitivity can be reduced by reasonably distributing the optical focal length while avoiding serious distortion.

[0042] (2) The effective diameter of the optical system of the micro-endoscopic microscope objective lens of the present invention can be shortened to 0.8 mm, the mechanical diameter can be shortened to 1.2 mm, and the total optical axis length can be shortened to 4.37 mm, which effectively shortens the length of the rigid part of the microprobe and reduces the difficulty for the operator to use the micro-endoscopic microscope objective lens to pass through narrow and curved channels. At the same time, the working distance of the micro-endoscopic microscope objective lens can be increased to 1000 μm, which increases the depth of the detection layer and correspondingly shortens the penetration depth of the microprobe, reducing the risk of the micro-endoscopic microscope objective lens scratching and damaging the object to be tested.

[0043] (3) The micro-endoscopic microscope objective lens of the present invention only includes three lens groups in the entire device, with a small number of components and a simple structure, which greatly shortens the total optical axis length. It can meet the requirements of a diameter less than 2 mm, an optical system total axis length less than 8 mm, and a working distance greater than 400 μm while ensuring the imaging quality, and reduces the difficulty of lens packaging, and has good application prospects and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 is a cross-sectional view of the micro-microscope objective optical system in Example 1 of the present invention;

[0046] Figure 2 is a point diagram of the micro-microscope objective optical system in Example 1 of the present invention;

[0047] Figure 3 is an MTF diagram of the micro-microscope objective optical system in Example 1 of the present invention;

[0048] Figure 4 is a field curvature distortion diagram of the micro-microscope objective optical system in Example 1 of the present invention;

[0049] Figure 5 is a cross-sectional view of the micro-microscope objective optical system in Example 2 of the present invention;

[0050] Figure 6 is a point diagram of the micro-microscope objective optical system in Example 2 of the present invention;

[0051] Figure 7 is an MTF diagram of the micro-microscope objective optical system in Example 2 of the present invention;

[0052] Figure 8 is a field curvature distortion diagram of the micro-microscope objective optical system in Example 2 of the present invention;

[0053] Figure 9 is a cross-sectional view of the micro-microscope objective optical system in Example 3 of the present invention;

[0054] Figure 10 is a point diagram of the micro-microscope objective optical system in Example 3 of the present invention;

[0055] Figure 11 is an MTF diagram of the micro-microscope objective optical system in Example 3 of the present invention;

[0056] Figure 12 3 is a field curvature distortion diagram of the micro-microscope objective optical system in Example 3 of the present invention;

[0057] Figure 13 is a cross-sectional view of the micro-microscope objective optical system in Example 4 of the present invention;

[0058] Figure 14is a point diagram of the micro-microscope objective optical system in Example 4 of the present invention;

[0059] Figure 15 is an MTF diagram of the micro-microscope objective optical system in Example 4 of the present invention;

[0060] Figure 16 is a field curvature distortion diagram of the micro-microscope objective optical system in Example 4 of the present invention;

[0061] Figure 17 is a cross-sectional view of the micro-microscope objective optical system in Example 5 of the present invention;

[0062] Figure 18 is a point diagram of the micro-microscope objective optical system in Example 5 of the present invention;

[0063] Figure 19 is an MTF diagram of the micro-microscope objective optical system in Example 5 of the present invention;

[0064] Figure 20 is a field curvature distortion diagram of the micro-microscope objective optical system in Example 5 of the present invention;

[0065] Figure 21 is a cross-sectional view of the micro-microscope objective optical system in Example 6 of the present invention;

[0066] Figure 22 is a point diagram of the micro-microscope objective optical system in Example 6 of the present invention;

[0067] Figure 23 is an MTF diagram of the micro-microscope objective optical system in Example 6 of the present invention;

[0068] Figure 24 is a field curvature distortion diagram of the micro-microscope objective optical system in Example 6 of the present invention;

[0069] Figure 25 is a cross-sectional view of a micro-microscope objective optical system in Example 7 of the present invention;

[0070] Figure 26 is a point diagram of the micro-microscope objective optical system in Example 7 of the present invention;

[0071] Figure 27 is an MTF diagram of the micro-microscope objective optical system in Example 7 of the present invention;

[0072] Figure 28 3 is a field curvature distortion diagram of the micro-microscope objective optical system in Example 7 of the present invention.

[0073] In all the drawings, the same reference numerals represent the same technical features, specifically: 1. First lens group; L11, first lens; L12, fourth lens; S11, first object-side surface; S12, first image-side surface; S13, cemented surface; 2. Second lens group; L21, second lens; S21, second object-side surface; S22, second image-side surface; 3. Third lens group; L31, third lens; S31, third object-side surface; S32, third image-side surface; S4, imaging surface; S5, object surface. DETAILED DESCRIPTION

[0074] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0075] In the description of the present invention, it should be understood that, unless otherwise expressly specified and limited, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0076] Furthermore, unless otherwise expressly specified or limited, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise expressly specified or limited.

[0077] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0078] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0079] Example:

[0080] See also Figures 1 to 28 The micro-endoscopic microscope objective lens in a preferred embodiment of the present invention includes an optical system, which includes a first lens group 1, a second lens group 2, and a third lens group 3, which are arranged in sequence from the object side to the image side along the optical axis, and an imaging surface S4. After light passes through the first lens group 1, the second lens group 2, and the third lens group 3 in sequence, it is imaged on the imaging surface S4.

[0081] Specifically, the first lens group 1 has positive refractive power, and is used to converge light transmitted from the object side and present the collected light to the second lens group 2.

[0082] More specifically, the side of the first lens group 1 close to the object plane is the first object-side surface S11, and the side close to the image plane is the first image-side surface S12, wherein the first object-side surface S11 is a spherical surface or a plane, and is further preferably a standard spherical surface and a convex surface to facilitate contact with tissue during endoscopic use; correspondingly, the first image-side surface S12 is a convex surface.

[0083] In actual configuration, the first lens group 1 may include only the first lens L11, or the first lens L11 may be cemented together with the fourth lens L12, which are arranged sequentially from the object side to the image side, to form the first lens group 1, with a cemented surface S13 formed between the fourth lens L12 and the first lens L11. Furthermore, the fourth lens L12 may be made of optical glass, while the first lens L11 may be made of optical plastic. The fourth lens L12 serves as a protective lens to prevent the first lens L11, which is made of optical plastic, from being scratched or absorbing water during endoscopic use.

[0084] Furthermore, the second lens group 2 has positive refractive power, and is used to further converge the light presented by the first lens group 1 and transmit it to the third lens group 3.

[0085] Specifically, the side of the second lens group 2 close to the object plane is the second object-side surface S21, and the side close to the image plane is the second image-side surface S22, wherein the second object-side surface S21 is a convex surface, and both the second object-side surface S21 and the second image-side surface S22 are aspherical surfaces.

[0086] Furthermore, the side of the third lens group 3 close to the object plane is the third object-side surface S31, and the side close to the image plane is the third image-side surface S32, wherein the third object-side surface S31 is a concave surface, the third image-side surface S32 is a convex surface, and both the third object-side surface S31 and the third image-side surface S32 are aspherical surfaces, forming a meniscus lens to correct field curvature, so as to cooperate with the second lens 2 to correct spherical aberration while adjusting the magnification.

[0087] Preferably, all aspheric surface shapes in the optical system of the present invention satisfy:

[0088] (1)

[0089] in, Indicates the distance of the surface from the vertex in the direction of the optical axis. represents the curvature of the surface vertex, represents the conic coefficient of the quadratic surface, represents the distance from the optical axis to the surface, 、 、 and Represent the fourth-order, sixth-order, eighth-order and tenth-order surface coefficients respectively.

[0090] Preferably, the second lens group 2 satisfies:

[0091] (2)

[0092] in, The effective light aperture of the second object side S21 is used as the effective light aperture of the micro endoscope microscope objective lens. It is the distance from the object plane S5 to the second object-side surface S21 along the optical axis, so that the working distance and the object-side numerical aperture of the optical system are reasonable, so that the second lens group 2 has better processing performance.

[0093] Preferably, the optical system of the present invention further satisfies:

[0094] (3)

[0095] in, TTL is the total length of the optical system, i.e., the distance from the first object-side surface S11 to the imaging surface S4 along the optical axis, FFL is the working distance of the optical system, that is, the distance from the object plane S5 to the first object-side surface S11 along the optical axis.

[0096] It is understandable that when TTL / FFLWhen the working distance is less than 4.2, each lens is too thin and has a large optical power, making it difficult to process and package the microscope. In addition, the working distance is too long, and the probability of light scattering from the object plane S5 to the first object side surface S11 increases, resulting in the microscope not being able to collect enough light for imaging. TTL / FFL When it is >9.9, the total length of the microscope's optical system is too long and the working distance is too short.

[0097] Preferably, the optical system of the present invention further satisfies:

[0098] (4)

[0099] when When the above conditions are met, the total length of the optical system is reasonable and the optical power distribution of the lens is appropriate, which is conducive to ensuring good processability and reducing the tolerance sensitivity during lens packaging.

[0100] Preferably, the optical system of the present invention further satisfies:

[0101] (5)

[0102] in, is the edge distance between the first image-side surface S12 and the second object-side surface S21, It is the center distance between the first image-side surface S12 and the second object-side surface S21, that is, the distance along the optical axis.

[0103] It is understandable that when When the first image side surface S12 and the second object side surface S21 have insufficient surface focal length, the subsequent surface focal length pressure is high, thereby reducing the processing and assembly performance of the microscope. When the curvature of the first image-side surface S12 or the second object-side surface S21 is too large, the lens is difficult to process.

[0104] Preferably, the optical system of the present invention further satisfies:

[0105] (6)

[0106] in, is the edge distance between the third image-side surface S32 and the third object-side surface S31, It is the center distance between the third image-side surface S32 and the third object-side surface S31 , so that the meniscus lens of the third lens group 3 has a reasonable thickness ratio, ensuring the machinability of the third lens group 3 .

[0107] Preferably, in order to ensure the machinability of the micro-microscope objective lens, the optical system of the present invention also meets the following requirements:

[0108] (7)

[0109] (8)

[0110] (9)

[0111] (10)

[0112] in, R is the radius of curvature of all lenses, is the center thickness of all lenses, is the edge thickness of all lenses, is the edge thickness of all lens spacings.

[0113] Preferably, the refractive index of the working environment of the micro-endoscopic microscope objective lens in the present invention, that is, the environment between the object plane S5 and the first object-side surface S11, is 1.34.

[0114] Example 1:

[0115] The first lens group 1 includes a first lens L11 made of H-ZLAF68N; the second lens group 2 includes a second lens L21 made of polymethyl methacrylate (PMMA); and the third lens group 3 includes a third lens L31 made of PMMA. The relevant parameters of each lens are shown in Table 1, and the distance relationship between the lens groups is shown in Table 2.

[0116]

[0117] It should be noted that the center-to-center spacing and edge-to-edge spacing in the above table refer to the distance between the current surface and the next surface. For example, the center thickness / spacing 0.63 mm corresponding to S5 represents the spacing between the object surface S5 and the first object-side surface S11, which is also the working distance of the microendoscopic microscope objective lens. For another example, the edge spacing corresponding to S11 represents the spacing between the first object-side surface S11 and the first image-side surface S12, which is also the edge thickness of the first lens group 1. The above notation is also applicable to the other specific embodiments described below.

[0118]

[0119] like Figure 1 As shown in , the effective light-clearance diameter of the micro-endoscopic microscope objective lens (the effective light-clearance diameter of the second object side S21) is 1 mm, the mechanical aperture (the outer diameter of the micro-endoscopic microscope objective lens) is 1.4 mm, the total axial length (TTL) is 5.56 mm, and the working distance is 630 μm.

[0120] The microscope objective lens in the above embodiment 1 is optically simulated. Figure 2 、 Figure 3 、 Figure 4From the dot plot, MTF plot and field curvature distortion plot, we can see that the imaging quality is good.

[0121] Example 2:

[0122] The first lens group 1 includes a first lens L11 made of PMMA; the second lens group 2 includes a second lens L21 made of PMMA; and the third lens group 3 includes a third lens L31 made of PMMA. The relevant parameters of each lens are shown in Table 3, and the distance relationship between the lens groups is shown in Table 4.

[0123]

[0124]

[0125] like Figure 5 As shown in , the effective aperture of the micro-endoscopic microscope objective lens is 0.8 mm, the mechanical aperture is 1.2 mm, the total axis length (TTL) is 4.55 mm, and the working distance is 500 μm.

[0126] The microscope objective lens in the above embodiment 2 is optically simulated. Figure 6 、 Figure 7 、 Figure 8 From the dot plot, MTF plot and field curvature distortion plot, we can see that the imaging quality is good.

[0127] Example 3:

[0128] The first lens group 1 includes a first lens L11 and a fourth lens L12. The first lens L11 is made of PMMA, and the fourth lens L12 is made of silicon dioxide (SILICA). The second lens group 2 includes a second lens L21, which is made of PMMA. The third lens group 3 includes a third lens L31, which is also made of PMMA. The relevant parameters of each lens are shown in Table 5, and the distance relationship between the lens groups is shown in Table 6.

[0129]

[0130]

[0131] like Figure 9 As shown in , the effective aperture of the micro-endoscopic microscope objective lens is 0.8 mm, the mechanical aperture is 1.2 mm, the total axis length (TTL) is 4.37 mm, and the working distance is 650 μm.

[0132] The microscope objective lens in the above embodiment 3 is optically simulated. Figure 10 、 Figure 11 、 Figure 12 From the dot plot, MTF plot and field curvature distortion plot, we can see that the imaging quality is good.

[0133] Example 4:

[0134] The first lens group 1 includes a first lens L11 and a fourth lens L12. The first lens L11 is made of PMMA, and the fourth lens L12 is made of silicon dioxide (SILICA). The second lens group 2 includes a second lens L21, which is made of PMMA. The third lens group 3 includes a third lens L31, which is also made of PMMA. The relevant parameters of each lens are shown in Table 7, and the distance relationship between the lens groups is shown in Table 8.

[0135]

[0136]

[0137] like Figure 13 As shown in , the effective aperture of the micro-endoscopic microscope objective lens is 0.8 mm, the mechanical aperture is 1.2 mm, the total axis length (TTL) is 4.62 mm, and the working distance is 650 μm.

[0138] The microscope objective lens in the above embodiment 4 is optically simulated. Figure 14 、 Figure 15 、 Figure 16 From the dot plot, MTF plot and field curvature distortion plot, we can see that the imaging quality is good.

[0139] Example 5:

[0140] The first lens group 1 includes a first lens L11 made of H-ZLAF68N; the second lens group 2 includes a second lens L21 made of H-K51; and the third lens group 3 includes a third lens L31 made of H-K51. The relevant parameters of each lens are shown in Table 9, and the distance relationships between the lens groups are shown in Table 10.

[0141]

[0142]

[0143] like Figure 17 As shown in , the effective aperture of the micro-endoscopic microscope objective lens is 1 mm, the mechanical aperture is 1.4 mm, the total axis length (TTL) is 5.63 mm, and the working distance is 630 μm.

[0144] The microscope objective lens in the above embodiment 5 is optically simulated. Figure 18 、 Figure 19 、 Figure 20 From the dot plot, MTF plot and field curvature distortion plot, we can see that the imaging quality is good.

[0145] Example 6:

[0146] The first lens group 1 includes a first lens L11, which is made of H-ZLAF68N; the second lens group 2 includes a second lens L21, which is made of PMMA; and the third lens group 3 includes a third lens L31, which is made of PMMA. The relevant parameters of each lens are shown in Table 11, and the distance relationship between the lens groups is shown in Table 12.

[0147]

[0148]

[0149] like Figure 21 As shown in , the effective aperture of the micro-endoscopic microscope objective lens is 0.9 mm, the mechanical aperture is 1.3 mm, the total axis length (TTL) is 4.45 mm, and the working distance is 1000 μm.

[0150] The microscope objective lens in the above embodiment 6 is optically simulated. Figure 22 、 Figure 23 、 Figure 24 From the dot plot, MTF plot and field curvature distortion plot, we can see that the imaging quality is good.

[0151] Example 7:

[0152] The first lens group 1 includes a first lens L11, which is made of H-ZLAF68N; the second lens group 2 includes a second lens L21, which is made of PMMA; and the third lens group 3 includes a third lens L31, which is made of PMMA. The relevant parameters of each lens are shown in Table 13, and the distance relationship between the lens groups is shown in Table 14.

[0153]

[0154]

[0155] like Figure 25 As shown in , the effective aperture of the micro-endoscopic microscope objective lens is 0.8 mm, the mechanical aperture is 1.2 mm, the total axis length (TTL) is 4.4 mm, and the working distance is 450 μm.

[0156] The optical simulation of the microscope objective lens in the above embodiment 7 is carried out. Figure 26 、 Figure 27 、 Figure 28 From the dot plot, MTF plot and field curvature distortion plot, we can see that the imaging quality is good.

[0157] The micro-endoscopic microscope objective lens of the present invention only includes three lens groups in the entire device, has a small number of components and a simple structure, greatly shortens the total optical axis length, can meet the requirements of reducing the device size and increasing the working distance of the device while ensuring imaging quality, and has good application prospects and promotion value.

[0158] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A micro endoscope objective lens, characterized in that: The optical system comprises a first lens group, a second lens group, a third lens group and an imaging surface, which are sequentially arranged from the object side to the image side; The first lens group has positive refractive power, and the image side surface of the lens closest to the image side is convex; The second lens group has positive optical power and includes a second lens; the object side surface of the second lens is convex, and both the object side surface and the image side surface are aspherical; The third lens group has negative optical power and includes a third lens; the object-side surface of the third lens is concave, the image-side surface is convex, and both the object-side surface and the image-side surface are aspherical; The light is imaged on the imaging surface after passing through the first lens group, the second lens and the third lens in sequence; The optical system satisfies: （3） in, TTL is the total length of the optical system, i.e., the distance along the optical axis from the object side surface of the lens closest to the object side of the first lens group to the imaging surface; FFL The working distance of the optical system is the distance from the object plane to the object side surface of the lens closest to the object side of the first lens group along the optical axis.

2. The micro endoscope objective lens according to claim 1, characterized in that: The aspheric surface shape of the inner lens of the micro-endoscopic microscope objective lens satisfies: （1） in, Indicates the distance of the surface from the vertex in the direction of the optical axis. represents the curvature of the surface vertex, represents the conic coefficient of the quadratic surface, represents the distance from the optical axis to the surface, 、 、 and Represent the fourth-order, sixth-order, eighth-order and tenth-order surface coefficients respectively.

3. The micro endoscope objective lens according to claim 1, wherein: The second lens group satisfies: （2） in, is the effective aperture of the second lens on the objective side, is the distance from the object plane to the object side surface of the second lens along the optical axis.

4. The micro endoscope objective lens according to claim 1, wherein: The optical system satisfies: （4） in, TTL is the total length of the optical system, i.e., the distance along the optical axis from the object side surface of the lens closest to the object side of the first lens group to the imaging surface; is the effective clear aperture of the second lens on the objective side.

5. The micro endoscope objective lens according to claim 1, wherein: The optical system satisfies: （5） in, is the edge distance between the image-side surface of the lens closest to the image side of the first lens group and the object-side surface of the second lens, It is the center distance between the image-side surface of the lens closest to the image side of the first lens group and the object-side surface of the second lens, that is, the distance along the optical axis.

6. The micro endoscope objective lens according to claim 1, characterized in that: The optical system satisfies: （6） in, is the edge distance between the image-side surface and the object-side surface of the third lens, is the center distance between the image-side surface and the object-side surface of the third lens.

7. The micro endoscope objective lens according to any one of claims 1 to 6, characterized in that: The first lens group includes a first lens; or the first lens group includes a fourth lens and a first lens arranged in sequence from the object side to the image side, the fourth lens is made of optical glass, the first lens is made of optical plastic, and the first lens group is composed of the fourth lens and the first lens cemented together.

8. The micro endoscope objective lens according to any one of claims 1 to 6, characterized in that: The refractive index of the working environment between the object side surface and the object plane of the lens closest to the object side of the first lens group is 1.34; and / or, The first lens group, the second lens group and the third lens group are made of optical glass or optical plastic.

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