Telecentric two-photon microscopy objective lens with large field of view, large numerical aperture and long working distance

Abstract

The present invention discloses a telecentric two-photon microscope objective lens with a large field of view, a large numerical aperture, and a long working distance, belonging to the field of novel two-photon microscope design. It sequentially includes, along the same optical axis: a diaphragm, a first lens group, a second lens group, and a third lens group; the first lens group includes a double-separated lens group with a negative focal power, which is used to correct the field curvature and coma of the two-color parallel light incident on the diaphragm; the second lens group includes a double-glued lens group with a positive focal power, which is used to expand and then combine the light beam emitted by the first lens group, thereby correcting the chromatic aberration of the light beam; the third lens group includes a single-lens group with a positive focal power, which is used to share the focal power of the combined light beam and ensure the telecentricity and long working distance of the light beam. The present invention can simultaneously achieve a large field of view, a large numerical aperture, and a relatively long back working distance, and has the advantages of high resolution, flat field in the whole field of view, high imaging quality, and long back working distance.

Description

Technical Field

[0001] The present invention belongs to the field of novel two-photon microscope design, and more specifically, relates to a telecentric two-photon microscope objective lens with a large field of view, a large numerical aperture, and a long working distance. Background Art

[0002] In recent years, with the development of medical technology, the demand for microscopic equipment has also evolved towards greater clarity, a wider field of view, and higher resolution. How to construct a microscope objective lens with a larger field of view and a larger numerical aperture has become a key research direction.

[0003] A two-photon microscope is a new technology that combines a laser scanning confocal microscope and two-photon excitation technology. Under high photon density conditions, fluorescent molecules simultaneously absorb two long-wavelength photons. After a very short time, known as the excited state lifetime, a photon with a shorter wavelength is emitted. The effect is the same as using a photon with a wavelength half that of the long wavelength to excite the fluorescent molecules. Two-photon microscopes have the advantages of strong penetration, low photobleaching and phototoxicity to samples, high light brightness, and high signal-to-noise ratio. However, the image plane diameter of existing microscope objectives and two-photon microscopes does not exceed 5 mm. For objectives that meet the numerical aperture conditions, their rear working distance is difficult to reach 10 mm. A small number of objectives that meet the requirements of a large field of view and a long working distance cannot achieve the required numerical aperture, resulting in insufficient resolution. For example, the far-field microscope objective lens model MUE12100 produced by Nikon Corporation of Japan has a working distance of 17.5 mm and a numerical aperture of only 0.3; while the model MUE12050 with a long working distance has a numerical aperture of 0.15 and cannot achieve high resolution. Another example is the Objective C Epiplan-Apochromat 5x / 0.2 DIC M27 model objective lens of Carl Zeiss AG of Germany, which has a working distance of 21.1 mm and a numerical aperture of 0.3; the Objective C Epiplan-Apochromat 10x / 0.4 DIC M27 model objective lens has a working distance of only 5.4 mm and a numerical aperture of 0.4. That is, existing two-photon microscopes for living biological cells cannot simultaneously achieve a large field of view, a large numerical aperture, and a long rear working distance. Summary of the Invention

[0004] Aiming at the defects and improvement requirements of the existing technology, the present invention provides a telecentric two-photon microscope objective lens with a large field of view, a large numerical aperture, and a long working distance, aiming to simultaneously achieve a large field of view, a large numerical aperture, and a long rear working distance.

[0005] To achieve the above object, the present invention provides a telecentric two-photon microscope objective lens with a large field of view, a large numerical aperture, and a long working distance, which sequentially includes along the same optical axis: a diaphragm, a first lens group, a second lens group, and a third lens group;

[0006] The first lens group includes a split lens group with negative optical power, which is used to correct the field curvature and coma of the dichromatic parallel light incident on the aperture;

[0007] The second lens group includes a doublet lens group with positive optical power, which is used to expand and then combine the light beam emitted by the first lens group, thereby correcting the chromatic aberration of the light beam;

[0008] The third lens group includes a single lens group with positive optical power, which is used to share the optical power of the combined light beam and ensure the telecentricity of the light beam.

[0009] Furthermore, the first lens group includes a first concave lens, a first biconvex lens, a first meniscus lens, and a second concave lens arranged in sequence along the optical axis;

[0010] The first concave lens and the first biconvex lens form a split lens group;

[0011] The first meniscus lens and the second concave lens form a split lens group.

[0012] Furthermore, the focal lengths of the first concave lens, the first biconvex lens, the first meniscus lens, and the second concave lens respectively satisfy:

[0013] -100mm ≤ f2 ≤ -80mm, 100mm ≤ f3 ≤ 110mm

[0014] 200mm ≤ f4 ≤ 250mm, -130mm ≤ f5 ≤ -110mm

[0015] Among them, f2, f3, f4, and f5 respectively represent the focal lengths of the first concave lens, the first biconvex lens, the first meniscus lens, and the second concave lens.

[0016] Furthermore, the distances between the aperture, the first concave lens, the first biconvex lens, the first meniscus lens, and the second concave lens satisfy:

[0017] 8mm ≤ d0 ≤ 12mm, 0 ≤ d1 ≤ 4mm, 0 ≤ d2 ≤ 4mm, 0 ≤ d3 ≤ 4mm;

[0018] Among them, d0, d1, d2, and d3 respectively represent the distances between the aperture along the optical axis and the adjacent lenses of the second concave lens.

[0019] Furthermore, the second lens group includes a first doublet lens, a single lens group, and a second doublet lens arranged in sequence along the optical axis;

[0020] The first doublet lens is used to expand the light beam emitted by the first lens group to correct the chromatic aberration of the light beam;

[0021] The single lens group is used to combine the expanded light beams;

[0022] The second doublet lens is used to correct the chromatic aberration of the combined light beams again.

[0023] Further, the first doublet lens includes a first biconcave lens and a second biconvex lens along the optical axis;

[0024] The single lens group includes a third biconvex lens and a second meniscus lens along the optical axis;

[0025] The second doublet lens includes a fourth biconvex lens and a second biconcave lens along the optical axis.

[0026] Further, the focal lengths of the first biconcave lens, the second biconvex lens, the third biconvex lens, the second meniscus lens, the fourth biconvex lens, and the second biconcave lens respectively satisfy:

[0027] -180mm ≤ f6 ≤ -160mm, 120mm ≤ f7 ≤ 130mm, 190mm ≤ f8 ≤ 210mm,

[0028] 220mm ≤ f9 ≤ 240mm, 150mm ≤ f 10 ≤ 160mm, -90mm ≤ f 11 ≤ -80mm,

[0029] wherein, f6, f7, f8, f9, f 10 and f 11 respectively represent the focal lengths of the first biconcave lens, the second biconvex lens, the third biconvex lens, the second meniscus lens, the fourth biconvex lens, and the second biconcave lens.

[0030] Further, the distances between the first lens group, the first biconcave lens, the second biconvex lens, the third biconvex lens, the second meniscus lens, the fourth biconvex lens, and the second biconcave lens satisfy:

[0031] 4mm ≤ d4 ≤ 8mm, d5 = 0, 0 ≤ d6 ≤ 1mm, 6mm ≤ d7 ≤ 10mm, 6mm ≤ d8 ≤ 10mm, d9 = 0;

[0032] wherein, d4, d5, d6, d7, d8, and d9 respectively represent the distances between adjacent lenses from the first lens group to the second biconcave lens along the optical axis.

[0033] Further, the third lens group includes a third meniscus lens, a fourth meniscus lens, and a fifth meniscus lens arranged in sequence along the optical axis.

[0034] Further, the focal lengths of the third meniscus lens, the fourth meniscus lens, and the fifth meniscus lens respectively satisfy:

[0035] 100mm ≤ f 12 ≤ 110mm, -70mm ≤ f 13 ≤ -60mm, 50mm ≤ f 14 ≤ 60mm

[0036] Wherein, f 12 , f 13 and f 14 respectively represent the focal lengths of the third meniscus lens, the fourth meniscus lens, and the fifth meniscus lens.

[0037] Generally speaking, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0038] (1) For the micro objective lens of the present invention, the designed first lens group includes a double-separated lens group structure with negative optical power, which provides great freedom for the regulation of the dichromatic parallel light beam incident on the aperture, undertakes most of the correction pressure of field curvature and coma, and enables the realization of the function of a large field of view and flat field; the second lens group includes a double-glued structure with positive optical power, expands and then combines the light rays passing through the field of view, and undertakes the correction of chromatic aberration; the third lens group includes a single lens group with positive optical power to undertake the optical power of the light beam combination, so that the path through which the light rays are focused is longer, leaving a longer back focal length; the mutual cooperation of the optical powers of the three lens groups makes the overall focal length of the objective lens consistent with the aperture of the aperture, ensuring a high numerical aperture. Through simulation experiments, assuming the focal length of the micro objective lens of the present invention is f, the numerical aperture is NA, the entrance pupil diameter is D, and the back focal length is BFL, then the micro objective lens of the present invention can achieve: 40mm ≤ D ≤ 50mm, 0.4 ≤ NA ≤ 0.6, 40mm ≤ f ≤ 50mm, 10mm ≤ BFL ≤ 15mm, that is, it has a large field of view, a large numerical aperture, and a long working distance at the same time.

[0039] (2) Preferably, the first lens group includes two double-separated lens groups, which can better correct the field curvature and coma of the light rays in the field of view and ensure the realization of a large field of view and flat field.

[0040] (3) Preferably, the second lens group includes a first double-glued lens, a single lens group, and a second double-glued lens, which perform multiple chromatic aberration corrections on the two passing beams to ensure a high quality of the light beam.

[0041] (4) Preferably, the micro objective lens designed by the present invention includes at most 13 spherical lenses, which has great processability and low processing cost, and is more conducive to engineering.

[0042] (5) The present invention simultaneously has the advantages of a two-photon microscope. When focusing the photons of the pulsed laser, the photon density at the focal point of the objective lens is the highest. Two-photon excitation only occurs at the focal point of the objective lens, eliminating the need for a confocal pinhole, improving the fluorescence detection efficiency. The working wavelength band is relatively narrow, using near-infrared wavelengths, which is easier to save the number of lenses compared to the visible light band.

[0043] In summary, the microscopic objective lens designed in the present invention is an infinity conjugate telecentric two-photon microscopic objective optical system with a large field of view, a large numerical aperture, and a long working distance. It has the advantages of high resolution, flat field across the entire field of view, high imaging quality, and a long back working distance, and can be applied to the detection of biological mouse brain cells. Brief Description of the Drawings

[0044] Figure 1 It is a schematic structural diagram of a two-photon microscopic objective with a large field of view, a large numerical aperture, and a long working distance provided by an embodiment of the present invention.

[0045] Figure 2 It is a transfer function diagram of a two-photon microscopic objective with a large field of view, a large numerical aperture, and a long working distance provided by an embodiment of the present invention.

[0046] Figure 3 It is a field curvature diagram of a two-photon microscopic objective with a large field of view, a large numerical aperture, and a long working distance provided by an embodiment of the present invention.

[0047] Figure 4 It is a spot diagram of a two-photon microscopic objective with a large field of view, a large numerical aperture, and a long working distance provided by an embodiment of the present invention.

[0048] Figure 5 It is an energy encirclement circle diagram of a two-photon microscopic objective with a large field of view, a large numerical aperture, and a long working distance provided by an embodiment of the present invention.

[0049] In all the drawings, the same reference numerals are used to represent the same elements or structures, where:

[0050] 1 - diaphragm, 2 - first concave lens, 3 - first biconvex lens, 4 - first meniscus lens, 5 - second concave lens, 6 - first biconcave lens, 7 - second biconvex lens, 8 - third biconvex lens, 9 - second meniscus lens, 10 - fourth biconvex lens, 11 - second biconcave lens, 12 - third meniscus lens, 13 - fourth meniscus lens, 14 - fifth meniscus lens, 15 - image plane. Detailed Embodiments

[0051] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0052] In the present invention, the terms "first", "second", etc. in the present invention and the accompanying drawings are used to distinguish similar objects and do not have to be used to describe a specific order or sequence.

[0053] As Figure 1 shown, the telecentric two-photon microscope objective lens with a large field of view, large numerical aperture and long working distance of the present invention includes a diaphragm 1, a first lens group, a second lens group and a third lens group along the same optical axis;

[0054] The first lens group includes a double-separated lens group with a negative focal power, which is used to correct the field curvature and coma of the two-color parallel light incident on the diaphragm 1;

[0055] The second lens group includes a double-glued lens group with a positive focal power, which is used to expand and then combine the beam passing through the first lens group, and further correct the chromatic aberration of the beam;

[0056] The third lens group includes a single-lens group with a positive focal power, which is used to share the focal power of the combined light and ensure the telecentricity of the beam.

[0057] Specifically, in the embodiment of the present invention, the first lens group includes a first concave lens 2, a first double-convex lens 3, a first meniscus lens 4 and a second concave lens 5 arranged in sequence along the optical axis. The first concave lens 2 and the first double-convex lens 3 form a double-separated lens group, and the first meniscus lens 4 and the second concave lens 5 form a second double-separated lens group. The structures of the two double-separated lens groups provide great freedom for the two-color parallel light incident on the diaphragm 1, and bear most of the correction pressure of the field curvature and coma, so that the function of a large field of view and flat field can be realized.

[0058] Specifically, in the embodiment of the present invention, the second lens group includes a first double-glued lens, a single-lens group and a second double-glued lens arranged in sequence along the optical axis; wherein, the first double-glued lens includes a first double-concave lens 6 and a second double-convex lens 7 along the optical axis, which are used to expand the beam passing through the first lens group and correct the chromatic aberration of the passing light; the single-lens group includes a third double-convex lens 8 and a second meniscus lens 9 along the optical axis, which are used to combine the expanded light; the second double-glued lens includes a fourth double-convex lens 10 and a second double-concave lens 11 along the optical axis, which are used to correct the chromatic aberration of the passing light again.

[0059] Specifically, in the embodiments of the present invention, the third lens group includes a third meniscus lens 12, a fourth meniscus lens 13, and a fifth meniscus lens 14 arranged in sequence along the optical axis. Three single lenses are used to share the optical power of the light beam combination, so that the path through which the light is focused is longer, leaving a longer back focal length.

[0060] Through the mutual cooperation of the optical powers of the above-mentioned first lens group, second lens group, and third lens group, the overall focal length of the objective lens designed by the present invention is approximately the same as the aperture of the diaphragm, ensuring a high numerical aperture. Let the focal length of the microscope objective of the present invention be f, the numerical aperture be NA, the entrance pupil diameter be D, and the back focal length be BFL. Finally, it can be achieved that: 40mm ≤ D ≤ 50mm, 0.4 ≤ NA ≤ 0.6, 40mm ≤ f ≤ 50mm, 10mm ≤ BFL ≤ 15mm, and the image plane width is 10 millimeters. The present invention can simultaneously achieve a large field of view, a large numerical aperture, and a long back working distance.

[0061] After the incident dichromatic parallel light passes through the diaphragm 1, the parallel light beam fills the entire entrance pupil of the microscope objective. After passing through the first lens group, second lens group, and third lens group in sequence, it is incident on the image plane 15. Among them, the first meniscus lens 4 is bent towards the diaphragm 1, and the second to fifth meniscus lenses are bent away from the diaphragm.

[0062] During use, biological cells enter the diaphragm 1 from the fifth meniscus lens 14 through the designed microscope objective, and form a microscopic device with a certain magnification through the subsequent Tube Lens combination. When designed, the incident dichromatic parallel light is focused on the image plane 15, that is, the object plane during use.

[0063] As a further design of the present invention, the distances, focal lengths, thicknesses, radii of curvature, and refractive indices between each lens are specifically designed.

[0064] Specifically, the distance between the diaphragm 1 and the first concave lens 2 is denoted as d0, the distance between the first concave lens 2 and the first biconvex lens 3 is denoted as d1, the distance between the first biconvex lens 3 and the first meniscus lens 4 is denoted as d2, the distance between the first meniscus lens 4 and the second concave lens 5 is denoted as d3, the distance between the second concave lens 5 and the first biconcave lens 6 is denoted as d4, the distance between the first biconcave lens 6 and the second biconvex lens 7 is denoted as d5, the distance between the second biconvex lens 7 and the third biconvex lens 8 is denoted as d6, the distance between the third biconvex lens 8 and the second meniscus lens 9 is denoted as d7, the distance between the second meniscus lens 9 and the fourth biconvex lens 10 is denoted as d8, the distance between the fourth biconvex lens 10 and the second biconcave lens 11 is denoted as d9, the distance between the second biconcave lens 11 and the third meniscus lens 12 is denoted as d 10 , the distance between the third meniscus lens 12 and the fourth meniscus lens 13 is denoted as d 11 , the distance between the fourth meniscus lens 13 and the fifth meniscus lens 14 is denoted as d12 , the distances respectively satisfy:

[0065] 8 mm ≤ d0 ≤ 12 mm;

[0066] 0 ≤ d1 ≤ 4 mm, 0 ≤ d2 ≤ 4 mm, 0 ≤ d3 ≤ 4 mm;

[0067] 4 mm ≤ d4 ≤ 8 mm, d5 = 0, 0 ≤ d6 ≤ 1 mm, 6 mm ≤ d7 ≤ 10 mm, 6 mm ≤ d8 ≤ 10 mm, d9 = 0;

[0068] 1 mm ≤ d 10 ≤ 5 mm, 1 mm ≤ d 11 ≤ 5 mm, 1 mm ≤ d 12 ≤ 5 mm.

[0069] The focal length of the first concave lens 2 is denoted as f2, the focal length of the first biconvex lens 3 is denoted as f3, the focal length of the first meniscus lens 4 is denoted as f4, the focal length of the second concave lens 5 is denoted as f5, the focal length of the first biconcave lens 6 is denoted as f6, the focal length of the second biconvex lens 7 is denoted as f7, the focal length of the third biconvex lens 8 is denoted as f8, the focal length of the second meniscus lens 9 is denoted as f9, the focal length of the fourth biconvex lens 10 is denoted as f 10 , the focal length of the second biconcave lens 11 is denoted as f 11 , the focal length of the third meniscus lens 12 is denoted as f 12 , the focal length of the fourth meniscus lens 13 is denoted as f 13 , the focal length of the fifth meniscus lens 14 is denoted as f 14 , then the focal lengths between the lenses respectively satisfy:

[0070] -100 mm ≤ f2 ≤ -80 mm, 100 mm ≤ f3 ≤ 110 mm, 200 mm ≤ f4 ≤ 250 mm,

[0071] -130 mm ≤ f5 ≤ -110 mm, -180 mm ≤ f6 ≤ -160 mm, 120 mm ≤ f7 ≤ 130 mm,

[0072] 190 mm ≤ f8 ≤ 210 mm, 220 mm ≤ f9 ≤ 240 mm, 150 mm ≤ f 10 ≤ 160 mm,

[0073] -90 mm ≤ f 11 ≤ -80 mm, 100 mm ≤ f 12 ≤ 110 mm, -70 mm ≤ f 13 ≤ -60 mm,

[0074] 50 mm ≤ f 14 ≤ 60 mm.

[0075] Compared with the microscopic objective lens using complex curved surfaces, the lenses of the present invention are all spherical lenses, which have higher feasibility and are more conducive to engineering.

[0076] The radius of curvature Radius (mm), thickness Thickness (mm), and refractive index RefractiveIndex of each lens are as follows:

[0077] -51 ≤ r20 ≤ -49, 3.5 ≤ d20 ≤ 4.5,

[0078] -475 ≤ r21 ≤ -473, 1.5 ≤ d21 ≤ 2.5, 1.4 ≤ R2 ≤ 1.6;

[0079] 289 ≤ r30 ≤ 291, 12.5 ≤ d30 ≤ 13.5,

[0080] -138 ≤ r31 ≤ -136, 1.5 ≤ d31 ≤ 2.5, 1.8 ≤ R3 ≤ 2.0;

[0081] -148 ≤ r40 ≤ -146, 13.5 ≤ d40 ≤ 14.5,

[0082] -79 ≤ r41 ≤ -77, 1.5 ≤ d41 ≤ 2.5, 1.6 ≤ R4 ≤ 1.8;

[0083] -79 ≤ r50 ≤ -77, 10.5 ≤ d50 ≤ 11.5,

[0084] -300 ≤ r51 ≤ -298, 5.5 ≤ d51 ≤ 6.5, 1.8 ≤ R5 ≤ 2.0;

[0085] -153 ≤ r60 ≤ -151, 8.5 ≤ d60 ≤ 9.5,

[0086] 349 ≤ r61 ≤ 351, 13.5 ≤ d61 ≤ 14.5, 1.8 ≤ R6 ≤ 2.0;

[0087] 349 ≤ r70 ≤ 351, 13.5 ≤ d70 ≤ 14.5,

[0088] -112 ≤ r71 ≤ -110, 0 ≤ d71 ≤ 0.7, 1.8 ≤ R7 ≤ 2.0;

[0089] 136 ≤ r80 ≤ 138, 13.5 ≤ d80 ≤ 14.5,

[0090] -1074 ≤ r81 ≤ -1072, 7.5 ≤ d81 ≤ 8.5, 1.5 ≤ R8 ≤ 1.7;

[0091] -93 ≤ r90 ≤ -91, 12.5 ≤ d90 ≤ 13.5,

[0092] 257 ≤ r91 ≤ 259, 7.5 ≤ d91 ≤ 8.5, 1.5 ≤ R9 ≤ 1.7;

[0093] 76 ≤ r100 ≤ 78, 11.5 ≤ d100 ≤ 12.5,

[0094] -187 ≤ r101 ≤ -185, 6.5 ≤ d101 ≤ 7.5, 1.5 ≤ R10 ≤ 1.7;

[0095] -187 ≤ r110 ≤ -185, 6.5 ≤ d110 ≤ 7.5,

[0096] 85 ≤ r111 ≤ 87, 2.5 ≤ d111 ≤ 3.5, 1.8 ≤ R11 ≤ 2.0;

[0097] 37 ≤ r120 ≤ 39, 11.5 ≤ d120 ≤ 12.5,

[0098] 78 ≤ r121 ≤ 80, 0.5 ≤ d121 ≤ 1.5, 1.5 ≤ R12 ≤ 1.7;

[0099] 37 ≤ r130 ≤ 39, 11.5 ≤ d130 ≤ 12.5,

[0100] 18 ≤ r131 ≤ 20, 1.5 ≤ d131 ≤ 2.5, 1.8 ≤ R13 ≤ 2.0;

[0101] 23 ≤ r140 ≤ 25, 12.5 ≤ d140 ≤ 13.5,

[0102] 35 ≤ r141 ≤ 37, 9.5 ≤ d141 ≤ 10.5, 1.8 ≤ R14 ≤ 2.0;

[0103] Among them, r20, r21, d20, d21, and R2 respectively represent the front curvature radius, rear curvature radius, center thickness of the lens, air thickness (i.e., the air distance between the lenses), and refractive index of the first concave lens 2;

[0104] r30, r31, d30, d31, and R3 respectively represent the front curvature radius, rear curvature radius, center thickness of the lens, air thickness, and refractive index of the first biconvex lens 3;

[0105] r40, r41, d40, d41, and R4 respectively represent the front curvature radius, rear curvature radius, center thickness of the lens, air thickness, and refractive index of the first meniscus lens 4;

[0106] r50, r51, d50, d51, and R5 respectively represent the front curvature radius, rear curvature radius, center thickness of the lens, air thickness, and refractive index of the second concave lens 5;

[0107] r60, r61, d60, d61, and R6 respectively represent the front curvature radius, rear curvature radius, central thickness of the lens, air thickness, and refractive index of the first biconcave lens 6;

[0108] r70, r71, d70, d71, and R7 respectively represent the front curvature radius, rear curvature radius, central thickness of the lens, air thickness, and refractive index of the second biconvex lens 7;

[0109] r80, r81, d80, d81, and R8 respectively represent the front curvature radius, rear curvature radius, central thickness of the lens, air thickness, and refractive index of the third biconvex lens 8;

[0110] r90, r91, d90, d91, and R9 respectively represent the front curvature radius, rear curvature radius, central thickness of the lens, air thickness, and refractive index of the second meniscus lens 9;

[0111] r100, r101, d100, d101, and R10 respectively represent the front curvature radius, rear curvature radius, central thickness of the lens, air thickness, and refractive index of the fourth biconvex lens 10;

[0112] r110, r111, d110, d111, and R11 respectively represent the front curvature radius, rear curvature radius, central thickness of the lens, air thickness, and refractive index of the second biconcave lens 11;

[0113] r120, r121, d120, d121, and R12 respectively represent the front curvature radius, rear curvature radius, central thickness of the lens, air thickness, and refractive index of the third meniscus lens 12;

[0114] r130, r131, d130, d131, and R13 respectively represent the front curvature radius, rear curvature radius, central thickness of the lens, air thickness, and refractive index of the fourth meniscus lens 13;

[0115] r140, r141, d140, d141, and R14 respectively represent the front curvature radius, rear curvature radius, central thickness of the lens, air thickness, and refractive index of the fifth meniscus lens 14.

[0116] In this embodiment, the following structural parameters shown in Table 1 are used for simulation, and the obtained simulation structure is as Figures 2 - 5 shown.

[0117] Table 1 Curvature Radius, Thickness, and Refractive Index of Each Lens

[0118]

[0119] Note: The thickness in the same row as the refractive index represents the central thickness of the lens.

[0120] From the structural parameters in Table 1, it can be known that the back working distance of the large field of view, large numerical aperture, and long working distance two-photon microscopy objective lens shown in the present invention is 10 mm, and the image plane size is 10 mm.

[0121] As Figure 2 shown, the transfer function image in the embodiment of the present invention represents the resolution ability at different line pairs in the meridional plane and sagittal plane of each field of view and each wavelength in the optical system. The horizontal axis represents the resolvable line pairs, and the vertical axis represents the contrast. The higher the contrast, the better the imaging quality. It can be seen from the figure that the transfer function of the present invention is close to the diffraction limit and has excellent imaging quality.

[0122] As Figure 3 shown, the field curvature / distortion diagram of the optical system in the embodiment of the present invention represents the field curvature and distortion of the optical system within the full field of view. It can be seen from the figure that the two-photon microscopy objective lens of the present invention has a full field of view field curvature within ±5 μm, achieving a flat field for the full field of view, and at the same time having small distortion.

[0123] As Figure 4 shown, the spot size of the optical system in the embodiment of the present invention is the most intuitive index reflecting the optical performance, representing the spot size corresponding to the image plane of the full field of view. It can be seen from the figure that the point spread function of the present invention is also close to the diffraction limit. The RMS (root mean square) value of the point spread function of the microscopy objective lens for the full field of view is less than 1.30 μm, and the GEO (geometric value) of the point spread function for the full field of view is less than 3.01 μm. When designing the direction, the point spread function is made as small as possible to ensure good image quality during forward use.

[0124] As Figure 5 shown, the encircled energy of the optical system in the embodiment of the present invention represents the spot size corresponding to 80% of the energy encircled in each field of view and wavelength of the optical system. Similar to the point spread function, the smaller the spot corresponding to 80% of the encircled energy, the better the image quality. Through Figure 5 it can be known that the spots corresponding to 80% of the energy of each field of view and each wavelength of the two-photon microscope of the present invention are less than 1.5 μm.

[0125] That is, the large field of view, large numerical aperture, and long working distance two-photon microscopy objective lens shown in the present invention has high imaging quality, high resolution, and at the same time has a large numerical aperture.

[0126] Preferably, the materials of the 13 spherical lenses of the present invention are respectively:

[0127] The first concave lens 2 is an environmental crown glass;

[0128] The first double convex lens 3, the first meniscus lens 4, the second concave lens 5, the first double concave lens 6, the second double concave lens 11 and the fourth meniscus lens 13 are all environmentally friendly heavy flint glasses;

[0129] The second double convex lens 7 and the fifth meniscus lens 14 are environmentally friendly heavy lanthanum flint glasses;

[0130] The third double convex lens 8, the second meniscus lens 9, the fourth double convex lens 10 and the third meniscus lens 12 are all environmentally friendly heavy crown glasses.

[0131] For the two-photon microscopy objective optical system of the present invention, the lenses required for each lens group are all spherical lenses, and at most 13 spherical lenses are needed, with a relatively low manufacturing cost. At the same time, it has high resolution, high imaging quality, a long working distance, and is convenient for focusing. A phase plate can be inserted at the system aperture. In addition, the structure is simple, and different magnifications of microscopy equipment can be designed with different combinations of Tube Lenses.

[0132] For the two-photon microscopy objective designed by the present invention, by setting the double-separation lens group, the double-glued lens group and the single lens group, the field curvature and the remaining off-axis aberrations are corrected specifically. Finally, compared with the common microscopy objectives on the current market, the designed one realizes the characteristics of a large field of view, a large numerical aperture and a long back working distance at the same time.

[0133] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A telecentric two-photon microscopy objective lens with a large field of view, a large numerical aperture, and a long working distance, characterized in that, It successively includes, along the same optical axis: a diaphragm, a first lens group, a second lens group, and a third lens group; The first lens group is used to correct the field curvature and coma of the dichromatic parallel light incident on the diaphragm; The second lens group is used to expand and then combine the light beam emitted by the first lens group, thereby correcting the chromatic aberration of the light beam; The third lens group includes a single lens group with positive optical power, which is used to share the optical power of the combined light and ensure the telecentricity of the light beam; The first lens group includes a first concave lens (2), a first biconvex lens (3), a first meniscus lens (4), and a second concave lens (5) successively arranged along the optical axis; The first concave lens (2) and the first biconvex lens (3) form a double-separated lens group; The first meniscus lens (4) and the second concave lens (5) form a double-separated lens group with negative optical power; The focal lengths of the first concave lens (2), the first biconvex lens (3), the first meniscus lens (4), and the second concave lens (5) respectively satisfy: -100mm ≤ f2 ≤ -80mm, 100mm ≤ f3 ≤ 110mm 200mm ≤ f4 ≤ 250mm, -130mm ≤ f5 ≤ -110mm Wherein, f2, f3, f4, and f5 respectively represent the focal lengths of the first concave lens (2), the first biconvex lens (3), the first meniscus lens (4), and the second concave lens (5); The second lens group includes a first double-glued lens, a single lens group, and a second double-glued lens with positive optical power successively arranged along the optical axis; The first double-glued lens is used to expand the light beam emitted by the first lens group to correct the chromatic aberration of the light beam; The single lens group is used to combine the expanded light; The second double-glued lens is used to correct the chromatic aberration of the combined light again; The first double-glued lens includes a first double concave lens (6) and a second biconvex lens (7) along the optical axis; The single lens group includes a third biconvex lens (8) and a second meniscus lens (9) along the optical axis; The second double-glued lens includes a fourth biconvex lens (10) and a second double concave lens (11) along the optical axis; The focal lengths of the first double concave lens (6), the second biconvex lens (7), the third biconvex lens (8), the second meniscus lens (9), the fourth biconvex lens (10), and the second double concave lens (11) respectively satisfy: -180mm ≤ f6 ≤ -160mm, 120mm ≤ f7 ≤ 130mm, 190mm ≤ f8 ≤ 210mm, 220mm ≤ f9 ≤ 240mm, 150mm ≤ f 10 ≤ 160mm, -90mm ≤ f 11 ≤ -80mm, Among them, f6, f7, f8, f9, f 10 and f 11 respectively represent the focal lengths of the first biconcave lens (6), the second biconvex lens (7), the third biconvex lens (8), the second meniscus lens (9), the fourth biconvex lens (10) and the second biconcave lens (11).

2. The microscopy objective lens according to claim 1, characterized in that, Along the optical axis direction, the distances between the diaphragm, the first concave lens (2), the first biconvex lens (3), the first meniscus lens (4), and the second concave lens (5) satisfy: 8mm ≤ d0 ≤ 12mm, 0 ≤ d1 ≤ 4mm, 0 ≤ d2 ≤ 4mm, 0 ≤ d3 ≤ 4mm; Among them, d0 represents the distance between the diaphragm and the first concave lens (2), d1 represents the distance between the first concave lens (2) and the first biconvex lens (3), d2 represents the distance between the first biconvex lens (3) and the first meniscus lens (4), and d3 represents the distance between the first meniscus lens (4) and the second concave lens (5).

3. The microscopy objective lens according to claim 1, characterized in that, Along the optical axis direction, the distances between the first lens group, the first double concave lens (6), the second biconvex lens (7), the third biconvex lens (8), the second meniscus lens (9), the fourth biconvex lens (10), and the second double concave lens (11) satisfy: 4mm ≤ d4 ≤ 8mm, d5 = 0, 0 ≤ d6 ≤ 1mm, 6mm ≤ d7 ≤ 10mm, 6mm ≤ d8 ≤ 10mm, d9 = 0; Among them, d4 represents the distance between the first lens group and the first double concave lens (6), d5 represents the distance between the first double concave lens (6) and the second biconvex lens (7), d6 represents the distance between the second biconvex lens (7) and the third biconvex lens (8), d7 represents the distance between the third biconvex lens (8) and the second meniscus lens (9), d8 represents the distance between the second meniscus lens (9) and the fourth biconvex lens (10), and d9 represents the distance between the fourth biconvex lens (10) and the second double concave lens (11).

4. The microscopy objective lens according to claim 1, characterized in that, The third lens group includes a third meniscus lens (12), a fourth meniscus lens (13), and a fifth meniscus lens (14) arranged in sequence along the optical axis.

5. The microscopy objective lens according to claim 4, characterized in that, The focal lengths of the third meniscus lens (12), the fourth meniscus lens (13), and the fifth meniscus lens (14) respectively satisfy: 100mm ≤ f 12 ≤ 110mm, -70mm ≤ f 13 ≤ -60mm, 50mm ≤ f 14 ≤ 60mm Among them, f 12 , f 13 and f 14 respectively represent the focal lengths of the third meniscus lens (12), the fourth meniscus lens (13) and the fifth meniscus lens (14).

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