Objective lens for cellular endomicroscope and cellular endomicroscope system

Abstract

An objective lens (100) for a cellular endomicroscope and a cellular endomicroscope system. The objective lens (100) comprises: a diaphragm (130) and a first lens group (110) and a second lens group (120) that are arranged on an object side and an image side, respectively, with respect to the diaphragm (130), wherein the number of lenses in the first lens group (110) and the number of lenses in the second lens group (120) are the same, and the positive and negative focal powers of a plurality of lenses in the first and second lens groups (110, 120) are symmetrically distributed with respect to the diaphragm. The objective lens (100), by means of the design of symmetrically distributed positive and negative focal powers, causes lateral aberrations (mainly coma, distortion, and lateral chromatic aberration) resulting from the lens group in the front to be at least partially offset by the lens group in the back.

Description

Objective lens for cell endoscope and cell endoscope system TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of optical lenses, and in particular to an objective lens for a cell endoscope and a cell endoscope system. BACKGROUND

[0002] A cell endoscope combines the functions of an endoscope and a microscope, and can perform high-resolution microscopic observation inside a living body and directly perform microscopic imaging on a living tissue. Through the cell endoscope, the structure of cells and the morphology of tissues can be clearly displayed, which is of great significance for disease diagnosis and treatment. For example, in the early diagnosis of tumors, the morphology and quantity of tumor cells can be directly observed through the cell endoscope, thereby improving the accuracy of diagnosis.

[0003] The key component of the cell endoscope for realizing magnification is an objective lens located at a head end. The outer diameter of a conventional gastroscope in clinical practice is within 10 mm. How to ensure that the imaging quality of the full field of view approaches the diffraction limit under the condition of limited size is a design difficulty. SUMMARY

[0004] Therefore, the present disclosure provides an objective lens for a cell endoscope and a cell endoscope system to improve imaging quality.

[0005] In a first aspect, an objective lens for a cell endoscope is provided, comprising:

[0006] a diaphragm; and

[0007] a first lens group and a second lens group disposed on the object side and the image side of the diaphragm, respectively,

[0008] wherein the first lens group and the second lens group have the same number of lenses, and the positive and negative signs of the refractive powers of the lenses in the first lens group and the second lens group are symmetrically distributed with respect to the diaphragm.

[0009] In some embodiments, the first lens group comprises first to third lenses arranged in sequence from the object side to the diaphragm, and the second lens group comprises fourth to sixth lenses arranged in sequence from the diaphragm to the image side.

[0010] In some embodiments, the first lens and the sixth lens are symmetrically distributed W-type or M-type lenses.

[0011] In some embodiments, the focal length f1 of the first lens has a focal length range of 10-20.

[0012] In some embodiments, the object-side numerical aperture NA of the objective lens satisfies the following expression:

[0013] 0.15 <= NA <= 0.55 (1A).

[0014] In some embodiments, the magnification m of the objective lens satisfies the following expression:

[0015] 0.5 <= m <= 2 (2A).

[0016] In some embodiments, the object-image conjugate distance L of the objective lens satisfies at least expression (3B) or (3C):

[0017] 0.4*f <= h <= 0.6*f (3A)

[0018] 3*f*f10 / f20 <= L <= 4*f*f10 / f20 (3B)

[0019] 5.5*h*f10 / f20 <= L <= 8.5*h*f10 / f20 (3C)

[0020] wherein h is the object half-height of the objective lens, f10 is the focal length of the first lens group, f20 is the focal length of the second lens group, and f is the focal length of the objective lens.

[0021] In some embodiments, the focal length f of the objective lens, the focal length f10 of the first lens group, and the focal length f20 of the second lens group satisfy at least one of the following expressions:

[0022] 2*f <= f10 <= 4*f (4A)

[0023] 1.3*f <= f20 <= 2.5*f (4B)

[0024] 0.7 <= f10 / f20 <= 2 (4C).

[0025] In some embodiments, the focal lengths f1, f2, f3, and f4 of the first lens, the second lens, the third lens, and the fourth lens, and the focal length f10 of the first lens group, and the focal length f20 of the second lens group satisfy at least one of the following expressions:

[0026] 1.5 <= f1 / f10 <= 2.8 (5A)

[0027] -0.8 <= f2 / f10 <= -0.4 (5B)

[0028] 0.37 <= f3 / f10 <= 0.57 (5C)

[0029] 0.5<= f4 / f20<=0.7 (5D).

[0030] In some embodiments, a ratio of a radius of curvature of the object side surface of the first lens to a focal length of the objective lens R11 / f, a ratio of a radius of curvature of the image side surface of the first lens to the focal length of the objective lens R12 / f, a ratio of a radius of curvature of the object side surface of the second lens to the focal length of the objective lens R21 / f, a ratio of a radius of curvature of the image side surface of the second lens to the focal length of the objective lens R22 / f, and a ratio of a radius of curvature of the object side surface of the third lens to the focal length of the objective lens R31 / f satisfy at least one of the following expressions:

[0031] 0.8<= R11 / f<=1.1 (6A)

[0032] 1.15<= R12 / f<=1.3 (6B)

[0033] -0.27<= R21 / f<= -0.2 (6C)

[0034] -0.5<= R22 / f<= -0.35 (6D)

[0035] 0.5<= R31 / f<=0.7 (6E).

[0036] In some embodiments, a ratio of the focal length of the objective lens to a radius of curvature of the image side surface of the third lens f / R32, and a ratio of the focal length of the objective lens to a radius of curvature of the object side surface of the fourth lens f / R41 satisfy at least one of the following expressions:

[0037] -0.3<= f / R32 <=0.3 (7A)

[0038] -0.3<= f / R41 <=0.3 (7B).

[0039] In some embodiments, a ratio of a radius of curvature of the image side surface of the fourth lens to the focal length of the objective lens R42 / f, a ratio of a radius of curvature of the object side surface of the fifth lens to the focal length of the objective lens R51 / f, and a ratio of a radius of curvature of the image side surface of the fifth lens to the focal length of the objective lens R52 / f satisfy at least one of the following expressions:

[0040] -0.55 <= R42 / f<= -0.4 (8A)

[0041] 0.35<=R51 / f<=0.45(8B)

[0042] 0.2<=R52 / f<=0.3(8C).

[0043] In some embodiments, the sag of the image side and object side of the second lens Sag22 and Sag21 at least satisfy one of the following expressions:

[0044] 0.014 <= (Sag21*f2*m) / (f10*L) <= 0.02 (9A)

[0045] -0.85<= Sag22 / Sag21 <= -0.65 (9B)

[0046] wherein L is the object-image conjugate distance of the objective lens, f2 is the focal length of the second lens, f10 is the focal length of the first lens group, and m is the magnification of the lens.

[0047] In some embodiments, the Abbe number of the plurality of lenses in the first lens group and the second lens group is symmetrically distributed with respect to the stop.

[0048] In some embodiments, the Abbe number of the first lens, the third lens, the fourth lens and the sixth lens ranges from 50 to 80, and the Abbe number of the second lens and the fifth lens ranges from 15 to 40.

[0049] In some embodiments, the refractive index of the plurality of lenses in the first lens group and the second lens group is symmetrically distributed with respect to the stop.

[0050] In some embodiments, the refractive index of the first lens, the third lens, the fourth lens and the sixth lens ranges from 1.48 to 1.79, and the refractive index of the second lens and the fifth lens ranges from 1.56 to 1.86.

[0051] In some embodiments, the working distance of the objective lens is less than 10 mm, the length of the objective lens is less than 200 mm, and the radial dimension of the objective lens is less than 100 mm.

[0052] In some embodiments, the optical power of the first lens to the third lens is positive, negative, and positive in sequence, and the optical power of the fourth lens to the sixth lens is positive, negative, and positive in sequence.

[0053] In some embodiments, further comprising: at least one first intermediate lens between the second lens and the third lens, and at least one second intermediate lens between the fourth lens and the fifth lens.

[0054] In some embodiments, the optical powers of the first lens to the third lens are positive, negative, and positive in sequence, the optical powers of the fourth lens to the sixth lens are positive, negative, and positive in sequence, the at least one first intermediate lens has a positive optical power type, and the at least one second intermediate lens has a positive optical power type.

[0055] In some embodiments, the plurality of lenses in the first lens group and the second lens group are double-sided aspheric lenses.

[0056] In some embodiments, further comprising: a glass cover plate arranged between the object side and the first lens group, and a filter arranged between the image side and the second lens group.

[0057] In a second aspect, the embodiments of the present disclosure provide a cell microscopy system, comprising the objective lens described in any one of the above embodiments, and an image sensor connected to the objective lens.

[0058] According to the objective lens for cell microscopy provided by the embodiments of the present disclosure, the symmetry design of the positive and negative optical powers on both sides of the stop makes the off-axis aberrations (mainly coma, distortion, and off-axis chromatic aberration) generated by the front lens group at least partially offset by the rear lens group, thereby improving the imaging quality of the objective lens. BRIEF DESCRIPTION OF DRAWINGS

[0059] The above and other objects, features and advantages of the present application will become more apparent from the following description of the embodiments of the present application, taken in conjunction with the accompanying drawings, in which:

[0060] FIG. 1 is a schematic diagram of an objective lens according to a first embodiment of the present disclosure;

[0061] FIG. 2 is a schematic diagram of an objective lens according to a second embodiment of the present disclosure;

[0062] FIG. 3 is a schematic diagram of an objective lens according to a third embodiment of the present disclosure;

[0063] FIG. 4 is a schematic diagram of an objective lens according to a fourth embodiment of the present disclosure;

[0064] FIG. 5 is a schematic diagram of an objective lens according to a fifth embodiment of the present disclosure;

[0065] FIG. 6 is a schematic diagram of the modulation transfer function (MTF) corresponding to the optical lens of the symmetric structure;

[0066] FIG. 7 is a schematic diagram of the thru-focus MTF of the optical lens of the symmetric structure;

[0067] FIG. 8 is a schematic diagram of the distortion corresponding to the field of view of the optical lens of the symmetric structure. DETAILED DESCRIPTION

[0068] For a better understanding of the present disclosure, various aspects of the present disclosure will be described in more detail below with reference to the accompanying drawings. It is to be understood that the detailed description is merely descriptive of exemplary embodiments of the present disclosure and is not intended in any way to limit the scope of the present disclosure. Throughout the specification, like reference numerals refer to like elements.

[0069] In this document, the first, second, etc. expressions are only used to distinguish features, components, entities, parts, etc. targets, and do not represent any limitation on the described targets. When the terms "include", "contain" and / or "have" are described, it means that the described target exists, but does not exclude the existence of other non-mentioned targets.

[0070] The core idea of various embodiments of the present disclosure is that the lenses on both sides of the diaphragm are symmetrically distributed according to the positive and negative of the optical power, the Abbe value, the refractive index and other parameters, so that the aberration (mainly coma, distortion, lateral chromatic aberration) generated by the front lens (or lens group) can be offset by the rear lens (or lens group), thereby improving the imaging quality of the objective lens. Before the various embodiments of the present disclosure are described in detail below with reference to the accompanying drawings and embodiments, the related terms and optical concepts of the present disclosure will be introduced.

[0071] The objective lens is a lens group composed of several lenses. The purpose of lens combination is to overcome the imaging defects of a single lens and improve the optical quality of the objective lens.

[0072] Optical power represents the degree of convergence or divergence of light rays by a lens (or lens group). When the focal length is positive, the optical power is positive; when the focal length is negative, the optical power is negative.

[0073] In this document, the surface of the lens close to the object side is called the object side surface, and the surface close to the image side is called the image side surface. When it is indicated that the object side surface or the image side surface of the lens is convex, it means that the object side surface or the image side surface of the lens is convex near the center of the majority of the area. When it is indicated that the object side surface or the image side surface of the lens is concave, it means that the object side surface or the image side surface of the lens is concave near the center of the majority of the area.

[0074] Figure 1 is a schematic diagram of an objective lens according to a first embodiment of the present disclosure. Referring to the diagram shown, the objective lens 100 includes a diaphragm 130 and lens groups 110 and 120 disposed on the object side and the image side, respectively, with respect to the diaphragm 130.

[0075] The lens group 110 includes lenses 111, 112 and 113, and the lens group 120 includes lenses 121, 122 and 123. The optical centers of the lenses are located on the same straight line (i.e., the optical axis). The positive and negative powers of the lenses 111, 112 and 113 of the lens group 110 are symmetrically distributed with respect to the diaphragm 130 as compared with the positive and negative powers of the lenses 121, 122 and 123 of the lens group 120. For example, the powers of the lenses 113, 112 and 111 are positive, negative and positive, respectively, and the powers of the lenses 121, 122 and 123 are also positive, negative and positive, respectively. For another example, if the powers of the lenses 113, 112 and 111 are negative, negative and positive, respectively, the powers of the lenses 121, 122 and 123 are also negative, negative and positive, respectively.

[0076] Hereinafter, two lenses in the two lens groups which are symmetric in the positive and negative powers with respect to the diaphragm are referred to as a lens pair.

[0077] In some embodiments, a plurality of lens pairs in the lens group 110 and the lens group 120 are aspherical lenses. FIG. 1 shows an example in which all the three lens pairs in the lens group 110 and the lens group 120 are aspherical lenses.

[0078] In some embodiments, the surface types of at least one lens pair in the lens group 110 and the lens group 120 are the same. The surface types include the surface types of positive power lenses and the surface types of negative power lenses. The surface types of positive power lenses include biconvex, plano-convex and meniscus convex, and the surface types of negative power lenses include biconcave, plano-concave and meniscus concave. FIG. 1 shows an example in which the surface types of the three lens pairs in the lens group 110 and the lens group 120 are the same. In FIG. 1, the surface types of the lenses 111 and 123 are plano-convex, the surface types of the lenses 112 and 122 are meniscus concave, and the surface types of the lenses 113 and 121 are both plano-convex or meniscus convex.

[0079] The adjacent surfaces of at least one pair of adjacent lenses in the lens group 110 and the lens group 120 are complementary in shape, for example, the image side surface of the lens 111 is convex or flat, and the object side surface of the lens 112 is concave. In other embodiments, the adjacent surfaces of at least one pair of adjacent lenses in the lens group 110 and the lens group 120 are the same in shape, for example, the image side surface of the lens 112 is convex, and the object side surface of the lens 113 is convex.

[0080] In some embodiments, the curvature difference (the difference in the curvature of the surfaces) of the corresponding surfaces of at least one lens pair in the lens group 110 and the lens group 120 is less than a first predetermined value. FIG. 1 shows an example in which the curvatures of the corresponding surfaces of two lens pairs in the lens group 110 and the lens group 120 are the same.

[0081] In some embodiments, the lens 111 and the lens 123 are symmetrically distributed W-type or M-type lenses. The W-type or M-type lens refers to a lens in which one curved surface is convex in the center and concave at the edge, or the center is concave and the edge is convex, similar to a W or M. As shown in the figure, the object side of the lens 111 and the image side of the lens 123 are similar to a W or M.

[0082] In some embodiments, the objective lens 100 includes a glass cover 150 and a filter 140. The glass cover 150 is arranged between the object side and the lens 111, so that the cell endoscope can be directly placed on the observed surface for imaging. The filter 140 is arranged between the lens 123 and the image sensor on the image side, for filtering out infrared light, preventing infrared light from reaching the imaging surface of the optical lens and affecting normal imaging; at the same time, the filter can switch between the visible light band and the infrared light band, and the optical lens can be designed for visible light and infrared light respectively, forming two complementary imaging information.

[0083] In some embodiments, the magnification of the objective lens 100 ranges from 0.5 to 2. Figure 1 shows that the magnification of the objective lens 100 is 1, that is, the ratio of the imaging height to the actual observed object height is 1:1.

[0084] Figure 2 is a schematic diagram of an objective lens according to a second embodiment of the present disclosure. Referring to the figure, the objective lens 200 is still a 3+3 lens group. In the objective lens 200, the lens group 210 and the lens group 220 are arranged on the object side and the image side of the stop 230 respectively, and the positive and negative of the optical power of the lenses 211, 212 and 213 of the lens group 210 and the positive and negative of the optical power of the lenses 221, 222 and 223 of the lens group 220 are symmetrically distributed with respect to the stop 230.

[0085] In this embodiment, the optical power of the lenses 213, 212 and 211 is positive, negative and positive respectively, and the optical power of the lenses 221, 222 and 223 is also positive, negative and positive.

[0086] In this embodiment, the surface types of at least one lens pair of the lens group 210 and the lens group 220 are the same. Figure 2 shows an example in which the surface types of two lens pairs in the lens group 210 and the lens group 220 are the same. In Figure 2, the surface type of the lens 211 is plano-convex, the surface type of the lens 223 is crescent convex, the surface types of the lenses 212 and 222 are crescent concave, and the surface types of the lenses 213 and 221 are biconvex or plano-convex.

[0087] In the present embodiment, the curvature difference between the object side surface of the lens 211 and the image side surface of the lens 223 is greater than the curvature difference between the lens 212 and the corresponding surface of the lens 222, and is also greater than the curvature difference between the lens 213 and the corresponding surface of the lens 221. Moreover, in the figure, the object side surface of the lens 211 and the image side surface of the lens 223 are convex in the center and concave at the edges, and the sag is less than a predetermined value.

[0088] In the present embodiment, the objective lens 200 comprises a glass cover 250 and a filter 240. The filter 240 is arranged between the lens 223 and the image side. The glass cover 250 is arranged between the object side and the lens 211.

[0089] In the present embodiment, the symmetry of the objective lens deviates from that of the figure 1, especially the lens pair composed of the lens 211 and the lens 223. The shape of the lens 211 is basically the same as that of the lens 111 in the figure 1, but the curvature of the corresponding surface of the lens 223 is greater than that of the lens 123, but the thickness is less than that of the lens 123. Thus, the present embodiment adjusts the magnification of the objective lens 200 by adjusting the surface curvature and thickness of the lens 223, and the magnification of the objective lens 200 is 1.5.

[0090] Figure 3 is a schematic diagram of an objective lens provided by the third embodiment of the present disclosure. Referring to the figure, the objective lens 300 is still a 3+3 lens group. In the objective lens 300, the lens group 310 and the lens group 320 are arranged on the object side and the image side with respect to the stop 330 respectively, and the positive and negative of the refractive powers of the lenses 311, 312 and 313 of the lens group 310 and the positive and negative of the refractive powers of the lenses 321, 322 and 323 of the lens group 320 are symmetrically distributed with respect to the stop 330.

[0091] In the present embodiment, the refractive powers of the lenses 313, 312 and 311 are positive, negative and positive respectively, and the refractive powers of the lenses 321, 322 and 323 are also positive, negative and positive respectively.

[0092] In the present embodiment, the surface types of at least one lens pair of the lens group 310 and the lens group 320 are the same. Figure 3 shows an example in which the surface types of three lens pairs in the lens group 310 and the lens group 320 are the same. In figure 3, the surface type of the lens 311 and the surface type of the lens 323 are both plano-convex, the surface types of the lenses 312 and 322 are both crescent concave, and the surface types of the lenses 313 and 321 are both bi-convex or plano-convex.

[0093] In the present embodiment, the objective lens 300 comprises a glass cover 350 and a filter 340. The filter 340 is arranged between the lens 323 and the image side. The filter 340 is, for example, an infrared cut filter (IR-cut filter). The glass cover 350 is arranged between the object side and the lens 311.

[0094] In the embodiment, the symmetry of the objective lens also deviates from that of FIG. 1, especially the lens pair composed of the lens 312 and the lens 322 deviates greatly in symmetry. In fact, the greater the deviation is, the more serious the loss of symmetry is when non-negative one-time imaging is performed. Thus, the embodiment adjusts the magnification of the objective lens 300 by deviating from the symmetry, and the magnification of the objective lens 300 is 0.66.

[0095] It should be understood that in the lens group composed of three lenses, the first positive lens close to the object or the image side is used to obtain large-angle incident light rays, slow down the light turning trend, and reduce the aberration correction difficulty of the subsequent optical system, then the second negative lens is used to diverge the entering light rays, slow down the light turning trend to further flatten the overstepping, and then the third lens close to the stop is used to converge the entering light rays, so that the aperture light rays close to parallel pass through the stop in each field of view, which is beneficial to the compact radial size and forms the symmetrical architecture.

[0096] FIG. 4 is a schematic diagram of an objective lens provided by a fourth embodiment of the present disclosure. Referring to the diagram, the objective lens 400 is a 4+4 lens group, in which the lens group 410 and the lens group 420 are arranged on the object side and the image side of the stop 430 respectively, and the positive and negative of the optical power of the lenses 411 to 414 of the lens group 410 and the positive and negative of the optical power of the lenses 421 to 424 of the lens group 420 are symmetrically distributed with respect to the stop 430.

[0097] In the embodiment, the optical power of the lenses 411 to 414 is positive, negative, positive, and positive respectively, and the optical power of the lenses 421 to 424 is also positive, negative, positive, and positive respectively. In other embodiments, the optical power of the lenses 411 to 414 and the optical power of the lenses 421 to 424 are designed to be positive, negative, negative, and positive.

[0098] In the embodiment, the surface types of at least one lens pair of the lens group 410 and the lens group 420 are the same. In FIG. 4, the surface type of the lens 411 and the surface type of the lens 424 are both plano-convex, the surface types of the lenses 412 and 423 are crescent concave, the surface types of the lenses 413 and 422 are crescent convex, the surface types of the lenses 414 and 421 are one of biconvex, crescent convex, and plano-convex, and the surface types of the lenses 414 and 421 can be the same or different.

[0099] In the embodiment, the objective lens 400 includes a glass cover 450 and a filter 440. The filter 440 is arranged between the lens 424 and the image side. The glass cover 450 is arranged between the object side and the lens 411.

[0100] Figure 5 is a schematic diagram of the objective lens provided in the fifth embodiment of this disclosure. Referring to the figure, the objective lens 500 is a 5+5 lens group. In the objective lens 500, lens group 510 and lens group 520 are respectively arranged on the object side and the image side relative to the aperture stop 530. The optical power positive and negative values ​​of lenses 511 to 515 of lens group 510 and lenses 525 to 521 of lens group 520 are symmetrically distributed with respect to the aperture stop 530.

[0101] In this embodiment, the optical powers of lenses 511 to 515 are positive, negative, negative, positive, and positive, respectively, and the optical powers of lenses 521 to 525 are also positive, positive, negative, negative, and positive, respectively.

[0102] In this embodiment, at least one lens pair of lens groups 510 and 520 has the same surface type. In FIG5, the surface type of lens 511 and lens 525 is plano-convex, the surface type of lens 512, lens 524, lens 513 and lens 523 is crescent-shaped concave, the surface type of lens 514 and lens 522 is crescent-shaped convex, and the surface type of lens 515 and lens 521 is one of biconvex, crescent-shaped convex and plano-convex. The surface types of lens 515 and lens 521 may be the same or different.

[0103] In this embodiment, the objective lens 500 further includes a cover glass 550 and a filter 540. The filter 540 is disposed between the lens 525 and the image side. The cover glass 550 is disposed between the object side and the lens 511.

[0104] Compared with the embodiments in Figures 1 to 3, the embodiments in Figures 4-5 have the advantage of slowing down the light deflection trend by using multiple intermediate lenses. Furthermore, the design of multiple intermediate lenses also helps to disperse and cancel transverse aberrations (mainly coma, distortion, and transverse chromatic aberration), resulting in higher imaging quality for the objective lens.

[0105] It should be understood that the various embodiments of this disclosure can be fabricated using a variety of materials and processes. The materials that can be used include aspherical plastics, glass, or glass-plastic hybrids, and the processes that can be used include wafer-level optics. In some embodiments, at least a portion of the lens is made of plastic. Compared to glass, plastics have poorer thermal stability and compressive strength; however, the biggest advantages of plastic aspherical lenses are their low cost, light weight, and ease of molding, making them suitable for disposable lens applications.

[0106] In some embodiments, the objective lens has a working distance of less than 10 mm, a length of less than 200 mm, and a radial dimension of less than 100 mm. For example, for intra-endoscopic applications, the objective lens may have a length of 10 mm and a radial dimension of 5 mm.

[0107] In some embodiments, the objective lens obtains a real image of the observed object on the image side corresponding to the object side.

[0108] In some embodiments, at least one aberration of the objective lens is offset due to the symmetric structure part, and the working distance of the objective lens is reduced due to the adoption of the double-sided aspherical lens.

[0109] Correspondingly, the disclosure also provides a cell microscopy system, which comprises the objective lens provided by the embodiments of the disclosure and an image sensor connected to the objective lens.

[0110] The numerical values and mutual relationship definitions of various parameters of the objective lens of the embodiments of the disclosure will be specifically introduced below. In the following, f represents the focal length of the objective lens, fi (i = 1, 2, 3,...) represents the focal length of the i th lens arranged in order from the object side to the image side, f10 and f20 respectively represent the focal length of the first lens group and the second lens group from the object side to the image side, Ri1 (i = 1, 2, 3,...) represents the radius of curvature of the object side surface of the i th lens arranged in order from the object side to the image side, Ri2 (i = 1, 2, 3,...) represents the radius of curvature of the image side surface of the i th lens arranged in order from the object side to the image side, Sagi1 (i = 1, 2, 3,...) represents the sag of the object side surface of the i th lens arranged in order from the object side to the image side, and Sagi2 (i = 1, 2, 3,...) represents the sag of the image side surface of the i th lens arranged in order from the object side to the image side.

[0111] In some embodiments, the numerical aperture NA of the objective lens on the object side satisfies the following expression:

[0112] 0.15 <= NA <= 0.55 (1A).

[0113] In some embodiments, the magnification m (image-object magnification) of the objective lens satisfies the following expression:

[0114] 0.5 <= m <= 2 (2A).

[0115] In some embodiments, the object half-height h of the objective lens satisfies the following expression:

[0116] 0.4*f <= h <= 0.6*f (3A).

[0117] In some embodiments, the object-image conjugate distance L of the objective lens satisfies expression (3B) or (3C):

[0118] 3*f*f10 / f20 <= L <= 4*f*f10 / f20 (3B)

[0119] 5.5*h*f10 / f20 <= L <= 8.5*h*f10 / f20 (3C).

[0120] In some embodiments, the Abbe values of the lenses on both sides of the stop are symmetrically distributed with respect to the stop.

[0121] In some embodiments, the Abbe values of the first lens, the third lens, the fourth lens and the sixth lens arranged in order from the object side to the image side are in the range of 50-80, and the Abbe values of the second lens and the fifth lens are in the range of 40-50 (including the endpoints).

[0122] In some embodiments, the refractive indices of the lenses on both sides of the stop are symmetrically distributed with respect to the stop.

[0123] In some embodiments, the refractive indices of the first lens, the third lens, the fourth lens and the sixth lens arranged in order from the object side to the image side are in the range of 1.48-1.79 (including the endpoints), and the refractive indices of the second lens and the fifth lens are in the range of 1.56-1.86 (including the endpoints).

[0124] In the above embodiments, the symmetric design of the refractive index and the dispersion high-low distribution on both sides of the stop makes the light rays diverge and converge within the limit, which is conducive to controlling the distortion and lateral chromatic aberration, and further eliminating the distortion and other aberrations.

[0125] In some embodiments, the image circle range of the objective lens (i.e. the diagonal line of the maximum field of view on the object side) is (0.8-1.2)*f / MAX(m, 1 / m), where MAX represents the maximum value, and m represents the magnification of the objective lens.

[0126] In some embodiments, the focal lengths f10 and f20 of the first lens group and the second lens group from the object side to the image side at least satisfy one of the following expressions:

[0127] 2*f <= f10 <=4*f (4A)

[0128] 1.3*f <= f20 <= 2.5*f (4B)

[0129] 0.7 <= f10 / f20 <= 2 (4C).

[0130] In some embodiments, the focal lengths f1, f2, f3 and f4 of the first lens, the second lens, the third lens and the fourth lens arranged in order from the object side to the image side, and the focal length f10 of the first lens group and the focal length f20 of the second lens group at least satisfy one of the following expressions:

[0131] 1.5<= f1 / f10<=2.8 (5A)

[0132] -0.8<= f2 / f10<=-0.4 (5B)

[0133] 0.37<= f3 / f10<=0.57 (5C)

[0134] 0.5<= f4 / f20<=0.7 (5D)。

[0135] In the above embodiments, by the specific distribution of the focal length (or optical power) of the two lens groups and / or the plurality of lenses from the object side to the image side, it is beneficial to control the distortion and aberration, and thus eliminate the distortion and aberration.

[0136] In some embodiments, the focal length f1 of the first lens has a focal length range of 10-20 (inclusive), that is, by designing the first lens as a large focal length lens, it is beneficial to subsequent lens aberration correction and miniaturization design of the objective length.

[0137] In some embodiments, the ratio of the radius of curvature of the object side surface of the first lens to the focal length of the objective lens R11 / f, the ratio of the radius of curvature of the image side surface of the first lens to the focal length of the objective lens R12 / f, the ratio of the radius of curvature of the object side surface of the second lens to the focal length of the objective lens R21 / f, the ratio of the radius of curvature of the image side surface of the second lens to the focal length of the objective lens R22 / f and the ratio of the radius of curvature of the object side surface of the third lens to the focal length of the objective lens R31 / f arranged in order from the object side to the image side at least satisfy one of the following expressions:

[0138] 0.8<= R11 / f<=1.1 (6A)

[0139] 1.15<= R12 / f<=1.3 (6B)

[0140] -0.27<= R21 / f<= -0.2 (6C)

[0141] -0.5<=R22 / f<= -0.35 (6D)

[0142] 0.5<= R31 / f<=0.7 (6E)。

[0143] In some embodiments, the ratio of the focal length of the objective lens to the radius of curvature of the image side surface of the third lens f / R32 arranged in order from the object side to the image side, and the ratio of the focal length of the objective lens to the radius of curvature of the object side surface of the fourth lens f / R41 satisfy the following expressions:

[0144] -0.3<= f / R32 <=0.3 (7A)

[0145] -0.3<= f / R41 <=0.3 (7B)。

[0146] In some embodiments, the ratio of the curvature radius of the image-side surface of the fourth lens to the focal length of the objective lens R42 / f, the ratio of the curvature radius of the object-side surface of the fifth lens to the focal length of the objective lens R51 / f, and the ratio of the curvature radius of the image-side surface of the fifth lens to the focal length of the objective lens R52 / f satisfy the following expression:

[0147] -0.55 <= R42 / f <= -0.4 (8A)

[0148] 0.35 <= R51 / f <= 0.45 (8B)

[0149] 0.2 <= R52 / f <= 0.3 (8C).

[0150] In the above embodiments, since the smaller the lens diameter, the more serious the optical distortion, therefore, through careful design of the aspherical lens surface, it is beneficial to the miniaturization design of the objective lens diameter, at the same time, the aspherical lens provides better optical performance through its complex surface design, which also helps to improve the imaging quality of the objective lens.

[0151] In some embodiments, the sagittal heights Sag21 and Sag22 of the object-side surface and the image-side surface of the second lens arranged in order from the object side to the image side satisfy the following expression:

[0152] 0.014 <= (Sag21*f2*m) / (f10*L) <= 0.02 (9A)

[0153] -0.85 <= Sag22 / Sag21 <= -0.65 (9B)

[0154] Wherein, L is the object-image conjugate distance of the objective lens.

[0155] In some embodiments, the object-side surface of the first lens arranged in order from the object side to the image side satisfies the following constraint: assuming Y-Z plane, after rotating 90°, z=f(y), its first derivative passes the Y axis three times.

[0156] In some embodiments, the image-side surface of the sixth lens arranged in order from the object side to the image side satisfies the following constraint: assuming Y-Z plane, after rotating 90°, z=f(y), its first derivative passes the Y axis three times.

[0157] It should be understood that, unless there is a contradiction, the parameter value relationship defined in two or more of the above embodiments can be combined into one embodiment.

[0158] Tables 1 to 3 below respectively give the parameter values under the objective lenses shown in Figures 1 to 3.

[0159] Table 1 Table 1

[0160] Table 2

[0161] Table 3

[0162] Figure 6 is a schematic diagram of the modulation transfer function (MTF) of the objective lens according to an embodiment of the present invention. The horizontal axis represents the spatial frequency (line pairs / mm, cycles / mm), and the vertical axis represents the sharpness or fidelity of image details, with a maximum value of 1, indicating that the image completely retains all the detailed features of the imaged object in space. As a natural low-pass filter, the MTF value gradually decreases as the spatial frequency increases. The highest point of the curve in this figure has a dashed line, representing the diffraction limit of this optical system, or the limiting optical imaging performance under ideal conditions. Taking the aforementioned spatial frequency as an example, at 200 line pairs / mm, the MTF is as high as about 0.6. Generally, an MTF of 0.3 or above indicates that objects at the corresponding spatial frequency can be clearly seen. Different curves represent different fields of view, or the normalized length obtained by connecting the center of the image to the four corners of the image. Different curves represent the fields of view corresponding to concentric circles drawn along this direction at different distances. Generally speaking, the MTF performance gradually decreases or decays the farther away from the center of the image.

[0163] As can be seen from the figure, the objective lens according to the embodiment of the present invention uses a double-sided aspherical lens to form a front and rear lens group symmetrical with respect to the aperture stop. Through the symmetrical design of the front and rear lens groups in terms of positive and negative optical power, Abbe value and refractive index, aberrations are corrected or compensated, achieving higher optical lens resolution than other methods (200 line pairs / mm corresponds to being able to see 2.5 micrometer details, and 400 line pairs / mm corresponds to being able to see 1.25 micrometer details).

[0164] Figure 7 is a schematic diagram of the Thru-focus optical transfer function (MTF) of the objective lens according to an embodiment of the present invention. This is the MTF before and after the optimal imaging plane at a fixed spatial frequency (this figure is 100 line pairs / mm (cycles / mm). Different curves represent different field sizes; the horizontal axis 0 represents the optimal imaging plane, and the horizontal axis represents the distance from the optimal imaging plane. As can be seen from the figure, the curves of all fields of view of the objective lens according to the embodiment of the present invention are quite concentrated, which means that when the image in the central area of ​​the image is the clearest, the image sharpness in the edge area is also the clearest, or in other words, the image sharpness in the center and the edge is synchronized.

[0165] Figure 8 is a schematic diagram of the distortion corresponding to the field of view of the objective lens according to an embodiment of the present invention. The vertical axis in the figure represents different fields of view (concentric circles with the center of the image as the center and a diagonal distance of 1.0), and the horizontal axis represents the distortion corresponding to different fields of view. As can be seen from the figure, the optical distortion of the objective lens according to the embodiment of the present invention is very small (the maximum value is about 0.02%, two ten-thousandths).

[0166] In summary, the optical lens provided according to the embodiments of this disclosure, by symmetrically arranging the front and rear lens groups relative to the aperture stop, and by symmetrically distributing the positive and negative optical power of the front and rear lens groups as well as the surface types of the object side and image side relative to the aperture stop, through this near-symmetrical structure design, allows several aberrations (mainly coma, distortion, and lateral chromatic aberration) caused by the lens or lens group in front of the aperture stop to be automatically canceled out by these aberrations caused by the lens or lens group behind, thereby achieving the ultimate requirement of ultra-high-definition imaging for the optical imaging system of the cell micro-endoscopy.

[0167] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0168] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Unless otherwise specified, the above embodiments and features can be combined with each other. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. An objective lens for a cellular microendoscope, comprising: a stop; and a first lens group and a second lens group disposed on an object side and an image side, respectively, with respect to the stop, wherein the first lens group and the second lens group have the same number of lenses, and the positive and negative signs of the refractive powers of the lenses in the first lens group and the second lens group are symmetrically distributed with respect to the stop.

2. The objective according to claim 1, wherein The first lens group comprises first to third lenses arranged in order from the object side to the stop, and the second lens group comprises fourth to sixth lenses arranged in order from the stop to the image side.

3. The objective according to claim 2, wherein The first lens and the sixth lens are symmetrically distributed W-type or M-type lenses.

4. The objective according to claim 2, wherein The focal length of the first lens ranges from 10 to 20.

5. The objective according to claim 1, wherein The numerical aperture NA of the objective lens on the object side satisfies the following expression: 0.15 <= NA <= 0.55 (1A).

6. The objective according to claim 1, wherein The magnification m of the objective lens satisfies the following expression: 0.5 <= m <= 2 (2A). 7.The objective lens of claim 2, wherein an object-image conjugate distance L of the objective lens satisfies at least one of the following expressions (3B) or (3C): 0.4*f <= h <= 0.6*f (3A) 3*f*f10 / f20 <= L <= 4*f*f10 / f20 (3B) 5.5*h*f10 / f20 <= L <= 8.5*h*f10 / f20 (3C) wherein h is an object half-height of the objective lens, f10 is a focal length of the first lens group, f20 is a focal length of the second lens group, and f is a focal length of the objective lens.

8. The objective according to claim 2, wherein The focal length f of the objective lens, the focal length f10 of the first lens group, and the focal length f20 of the second lens group satisfy at least one of the following expressions: 2*f <= f10 <=4*f (4A) 1.3*f <= f20 <= 2.5*f (4B) <= f10 / f20 <= 2 (4C).

9. The objective according to claim 2, wherein The focal lengths f1, f2, f3, and f4 of the first, second, third, and fourth lenses satisfy at least one of the following expressions with the focal length f10 of the first lens group and the focal length f20 of the second lens group: 1.5 <= f1 / f10 <= 2.8 (5A) -0.8 <= f2 / f10 <= -0.4 (5B) 0.37 <= f3 / f10 <= 0.57 (5C) 0.5 <= f4 / f20 <= 0.7 (5D).

10. The objective according to claim 2, wherein The ratio R11 / f of the radius of curvature of the object side surface of the first lens to the focal length of the objective lens, the ratio R12 / f of the radius of curvature of the image side surface of the first lens to the focal length of the objective lens, the ratio R21 / f of the radius of curvature of the object side surface of the second lens to the focal length of the objective lens, the ratio R22 / f of the radius of curvature of the image side surface of the second lens to the focal length of the objective lens, and the ratio R31 / f of the radius of curvature of the object side surface of the third lens to the focal length of the objective lens satisfy at least one of the following expressions: 0.8 <= R11 / f <= 1.1 (6A) 1.15 <= R12 / f <= 1.3 (6B) -0.27 <= R21 / f <= -0.2 (6C) -0.5 <= R22 / f <= -0.35 (6D) 0.5 <= R31 / f <= 0.7 (6E).

11. The objective according to claim 2, wherein The ratio of the focal length of the objective lens to the radius of curvature of the image side surface of the third lens f / R32, and the ratio of the focal length of the objective lens to the radius of curvature of the object side surface of the fourth lens f / R41 at least satisfy one of the following expressions: -0.3 <= f / R32 <= 0.3 (7A) -0.3 <= f / R41 <= 0.3 (7B).

12. The objective according to claim 2, wherein The ratio of the radius of curvature of the image side surface of the fourth lens to the focal length of the objective lens R42 / f, the ratio of the radius of curvature of the object side surface of the fifth lens to the focal length of the objective lens R51 / f, and the ratio of the radius of curvature of the image side surface of the fifth lens to the focal length of the objective lens R52 / f at least satisfy one of the following expressions: -0.55 <= R42 / f <= -0.4 (8A) 0.35 <= R51 / f <= 0.45 (8B) 0.2 <= R52 / f <= 0.3 (8C).

13. The objective according to claim 2, wherein The sag Sags of the image side surface and the object side surface of the second lens at least satisfy one of the following expressions: 0.014 <= (Sag21*f2*m) / (f10*L) <= 0.02 (9A) -0.85 <= Sag22 / Sag21 <= -0.65 (9B) Wherein, L is the object-image conjugate distance of the objective lens, f2 is the focal length of the second lens, f10 is the focal length of the first lens group, and m is the magnification of the lens.

14. The objective according to claim 1, wherein The Abbe number of the plurality of lenses in the first lens group and the second lens group is symmetrically distributed with respect to the stop.

15. The objective according to claim 2, wherein The Abbe number of the first lens, the third lens, the fourth lens and the sixth lens ranges from 50 to 80, and the Abbe number of the second lens and the fifth lens ranges from 15 to 40.

16. The objective according to claim 1, wherein The refractive index of the plurality of lenses in the first lens group and the second lens group is symmetrically distributed with respect to the stop.

17. The objective according to claim 2, wherein The refractive index of the first lens, the third lens, the fourth lens and the sixth lens ranges from 1.48 to 1.79, and the refractive index of the second lens and the fifth lens ranges from 1.56 to 1.

86.

18. The objective according to claim 1, wherein The working distance of the objective lens is less than 10 mm, the length of the objective lens is less than 200 mm, and the radial dimension of the objective lens is less than 100 mm.

19. The objective lens of claim 2, wherein the optical power of the first lens to the third lens is positive, negative, and positive in sequence, and the optical power of the fourth lens to the sixth lens is positive, negative, and positive in sequence.

20. The objective of claim 2, further comprising: At least one first intermediate mirror between the second lens and the third lens, and at least one second intermediate mirror between the fourth lens and the fifth lens.

21. The objective according to claim 18, wherein The optical powers of the first lens to the third lens are positive, negative, and positive in order, the optical powers of the fourth lens to the sixth lens are positive, negative, and positive in order, the optical power type of the at least one first intermediate lens is positive, and the optical power type of the at least one second intermediate lens is positive.

22. The objective according to claim 1, wherein The plurality of lenses in the first lens group and the second lens group are double-sided aspheric lenses.

23. The objective of claim 1, further comprising: A glass cover is arranged between the object side and the first lens group, and a filter is arranged between the image side and the second lens group.

24. A cellular microscopy system comprising the objective lens according to any one of claims 1 to 23, and an image sensor connected to the objective lens.

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