Microobjective

Abstract

The invention relates to the technical field of optical instruments, and discloses and provides a microscope objective which is at least suitable for a temperature environment of 50K-150K, and comprises a front group unit which at least comprises a first lens and a second lens which are sequentially arranged along a light path from front to back and is suitable for converging light and correcting spherical aberration; the middle group unit is arranged on the rear side of the light path of the front group unit and at least comprises a first middle group and a second middle group, the first middle group and the second middle group are sequentially and adjacently arranged front and back along the light path, and at least two lenses arranged at intervals are arranged in each middle group and are suitable for correcting chromatic aberration; the rear group unit is arranged on the rear side of the light path of the middle group unit and comprises at least two lenses which are arranged at intervals; each lens included in the front group unit, the middle group unit and the rear group unit is a single lens. According to the microscope objective lens, each lens is arranged to be a single lens, and in each unit and the whole microscope objective lens, a bonding lens is prevented from being arranged to realize combined connection, so that the problems of damage, falling or deflation in extreme environments such as low temperature and the like are avoided, and the application in the low-temperature environment is met.

Description

Technical Field

[0001] The invention relates to the technical field of optical instruments, and in particular to a microscope objective lens. Background Art

[0002] Visual imaging is an important research method in low-temperature imaging research in many fields, such as epoxy resin electrical tree growth and liquid nitrogen two-phase fluid dynamics.

[0003] However, conventional microscope objectives usually use double-cemented or triple-cemented lens groups to correct lens chromatic aberration in order to achieve excellent imaging effects. However, in low-temperature environments, cemented lenses may experience problems such as detachment and degassing, which will affect the imaging effect and structural life of the objective. Summary of the invention

[0004] In view of this, the present invention provides a microscope objective lens to solve the problem that the existing microscope objective lens is difficult to achieve effective detection in a low temperature environment.

[0005] In a first aspect, the present invention provides a microscope objective lens, which is at least suitable for a temperature environment of 50K to 150K, and comprises: a front group unit, comprising at least a first lens and a second lens arranged in sequence along an optical path, suitable for converging light and correcting spherical aberration; a middle group unit, arranged at the rear side of the optical path of the front group unit, comprising at least a first middle group and a second middle group, and arranged adjacent to each other in sequence along the optical path, each middle group being provided with at least two lenses arranged at intervals, suitable for correcting chromatic aberration; a rear group unit, arranged at the rear side of the optical path of the middle group unit, comprising at least two lenses arranged at intervals; each lens contained in the front group unit, the middle group unit and the rear group unit is a single lens.

[0006] Beneficial Effects

[0007] By arranging that each lens contained in the front unit group, the middle unit group and the rear unit group are all single lenses, it is avoided to arrange cemented lenses in each unit and the overall microscope objective to achieve combined connection, thereby avoiding the problems of damage, falling off or degassing in extreme environments such as low temperature, and meeting the application in low temperature environments. At the same time, by arranging the front unit group, the middle unit group and the rear unit group separately to achieve correction of spherical aberration, chromatic aberration and off-axis aberration, a separate lens is used to achieve achromatism, thereby ensuring that the microscope objective has sufficient observation accuracy.

[0008] In an optional embodiment, the first lens and the second lens are arranged as positive lenses and are arranged with arcs bent in the same direction, suitable for being concave toward the object to be observed, and jointly providing positive optical power.

[0009] In an optional implementation, the refractive index of the first lens is higher than that of the second lens; the first lens is made of a low Abbe number material, and the second lens is made of a high Abbe number material.

[0010] In an optional implementation, the middle group unit further includes a third middle group, and the third middle group is arranged at a rear side of the second middle group along the optical path.

[0011] In an optional embodiment, the first middle group includes a third lens, a fourth lens and a fifth lens, and are arranged in sequence along the optical path. The fourth lens is arranged as a negative lens, suitable for providing negative optical focal length, and the third lens and the fifth lens are arranged as positive lenses, suitable for providing positive optical focal lengths respectively; the refractive index of the fourth lens is higher than that of the third lens and the fifth lens, respectively, and is suitable for adjusting coma. The fourth lens is made of a low Abbe number material, and the third lens and the fifth lens are made of a high Abbe number material.

[0012] In an optional embodiment, the second middle group includes a sixth lens and a seventh lens, respectively, and the third middle group includes an eighth lens and a ninth lens, respectively, and the sixth lens, the seventh lens, the eighth lens and the ninth lens are arranged in sequence along the optical path, the sixth lens and the eighth lens are arranged as negative lenses, suitable for providing negative optical focal length, and the seventh lens and the ninth lens are arranged as positive lenses, suitable for providing positive optical focal length; the refractive index of the sixth lens is greater than that of the seventh lens, and the refractive index of the eighth lens is greater than that of the ninth lens, the sixth lens and the eighth lens are respectively composed of low Abbe number materials, and the seventh lens and the ninth lens are composed of high Abbe number materials.

[0013] In an optional embodiment, the rear group unit is arranged in a symmetrical double Gaussian structure, including a tenth lens, an eleventh lens, a twelfth lens and a thirteenth lens distributed in sequence along the optical path, the eleventh lens and the twelfth lens are arranged as negative lenses, suitable for providing negative optical focal length, and the tenth lens and the thirteenth lens are arranged as positive lenses, suitable for providing positive optical focal length.

[0014] In an optional implementation, the refractive index of the thirteenth lens is greater than that of the tenth lens, the eleventh lens and the twelfth lens; the thirteenth lens and the eleventh lens are respectively made of low Abbe number materials, and the tenth lens and the twelfth lens are made of high Abbe number materials;

[0015] In an optional implementation, the focal length of the microscope objective is fx, the focal length of the first lens is f1, 4.1≤f1 / fx≤4.5; the focal length of the second lens is f2, 6.7≤f2 / fx≤7.1;

[0016] In an optional embodiment, the focal length of the front group unit is fa, 2.3≤fa / fx≤2.7, the focal length of the first middle group is fb, 6.5≤fb / fx≤6.9, the focal length of the second middle group is fc, 12.8≤fc / fx≤14.2, the focal length of the third middle group is fd, 50≤fd / fx≤54, and the focal length of the rear group unit is fe, -7.9≤fe / fx≤-7.5.

[0017] In an optional embodiment, 3.9 mm≤fx≤4.1 mm.

[0018] In an optional implementation, the aperture of the microscope objective lens is NA, 0.8≤NA≤0.9.

[0019] In an optional implementation, the object field of view of the microscope objective is B, 0≤B≤0.4mm; and / or the distance between the first lens and the object to be observed is C, C≥1.6mm.

[0020] In an optional implementation, the thirteenth lens is an aspherical lens, the ninth lens is an aspherical lens, and the fifth lens is an aspherical lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic diagram of the structure and optical path of a microscope objective lens according to an embodiment of the present invention;

[0023] Figure 2 for Figure 1 Schematic diagram of light aberration curve of microscope objective lens shown;

[0024] Figure 3 for Figure 1 Schematic diagram of wavefront aberration curve of microscope objective shown;

[0025] Figure 4 for Figure 1 Schematic diagram of the MTF curve of the microscope objective shown;

[0026] Figure 5 for Figure 1 Schematic diagram of the axial aberration curve of the microscope objective shown;

[0027] Figure 6 for Figure 1 Schematic diagram of field curvature and distortion curve of microscope objective shown;

[0028] Description of reference numerals:

[0029] 1. Front unit group; 11. First lens; 12. Second lens; 2. First middle group; 21. Third lens; 22. Fourth lens; 23. Fifth lens; 3. Second middle group; 31. Sixth lens; 32. Seventh lens; 4. Third middle group; 41. Eighth lens; 42. Ninth lens; 5. Back unit group; 51. Tenth lens; 52. Eleventh lens; 53. Twelfth lens; 54. Thirteenth lens. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0031] like Figure 1-Figure 6 In a first aspect, the present invention provides a microscope objective lens. In this embodiment, the microscope objective lens is suitable for a temperature environment of 50K to 150K. Preferably, the temperature environment can be provided by immersing the microscope objective lens in liquid nitrogen or the like. It can be understood that the operating environment temperature of the microscope objective lens can also be higher than 150K or lower than 50K.

[0032] The microscope objective lens comprises: a front unit group 1, a middle unit group and a rear unit group 5. Definition: along the observation direction, the side relatively close to the object to be observed is the front side of the optical path, and the side relatively far from the object to be observed is the rear side of the optical path.

[0033] The front group unit 1 at least includes a first lens 11 and a second lens 12 arranged in sequence along the optical path, which are suitable for converging light and correcting spherical aberration. The middle group unit is arranged at the rear side of the optical path of the front group unit 1, and at least includes a first middle group 2 and a second middle group 3, which are arranged adjacent to each other in sequence along the optical path, and each middle group is provided with at least two lenses arranged at intervals, which are suitable for correcting chromatic aberration; the rear group unit 5 is arranged at the rear side of the optical path of the middle group unit, and includes at least two lenses arranged at intervals, which are suitable for correcting positive off-axis aberration.

[0034] Preferably, each lens included in the front group unit 1, the middle group unit and the rear group unit 5 is a single lens. In this embodiment, the single lens can be matched with the external structure such as the lens barrel by means of snap-fit, sealed abutment, interference fit, magnetic attraction, threaded fit, etc., avoiding the connection with the adjacent lens or external structure by means of bonding.

[0035] By arranging that each lens contained in the front unit group 1, the middle unit group and the rear unit group 5 are all single lenses, each unit and the overall microscope objective lens avoids the need to set a cemented lens to achieve a combined connection, thereby avoiding the problems of damage, falling off or degassing in extreme environments such as low temperature, and meeting the application requirements in low-temperature environments. At the same time, by separately arranging the front unit group 1, the middle unit group and the rear unit group 5 to achieve correction of spherical aberration, chromatic aberration and off-axis aberration, separate lenses are used to achieve achromatism, thereby ensuring that the microscope objective lens has sufficient observation accuracy.

[0036] Preferably, the front group unit 1 only includes a first lens 11 and a second lens 12 which are sequentially arranged along the optical path. As a convertible embodiment, the front group unit 1 may also include three lenses.

[0037] In the embodiment, the first lens 11 and the second lens 12 are arranged as positive lenses and are arranged to be curved in the same direction, suitable for being concave toward the object to be observed, and jointly providing positive optical power.

[0038] The first lens 11 and the second lens 12 in the front group unit 1 are both positive lenses to provide optical power for the entire objective lens, which can converge the light on the object side, reduce the light divergence angle, correct spherical aberration, and prepare for the correction of chromatic aberration by the middle group.

[0039] The refractive index of the first lens 11 is higher than that of the second lens 12. In addition, the first lens 11 is made of a low Abbe number material, and the second lens 12 is made of a high Abbe number material. In this embodiment, the low Abbe number material refers to a material whose Abbe number is equal to or lower than 50; the high Abbe number material refers to a material whose Abbe number is higher than 50.

[0040] By setting the front unit group 1 to include only two lenses, not only can the material usage be reduced and the cost be saved, but also, by combining the size settings of the refractive index and Abbe number of the two lenses, the axial volume can be shorter and the processing cost can be lowered while ensuring the imaging effect of the front unit group 1, thereby further reducing the difficulty of assembly.

[0041] Preferably, the middle group unit further comprises a third middle group 4, and the third middle group 4 is arranged along the optical path at intervals behind the second middle group 3. As a convertible implementation, the third middle group 4 may also not be provided.

[0042] The setting of the third center group 4 can not only cooperate with the first center group 2 and the second center group 3 to achieve the effect of correcting the chromatic aberration of the entire system, but also assist the rear group unit 5, and improve the off-axis aberration correction capability of the rear group unit 5 by adjusting the distance between the two.

[0043] In this embodiment, the first middle group 2 includes a third lens 21, a fourth lens 22 and a fifth lens 23, which are arranged in sequence along the optical path; the fourth lens 22 is arranged as a negative lens, suitable for providing negative optical power, and the third lens 21 and the fifth lens 23 are arranged as positive lenses, suitable for providing positive optical power respectively.

[0044] When the focal length is the same and a "negative-positive-negative" structure is used, the positive lens in the middle needs to bear a larger focal length, the surface shape is steeper, the light incident angle is large, the processing difficulty is high, and the difficulty of subsequent anti-reflection film coating is increased. The first middle group 2 adopts a "positive-negative-positive" structure of focal length. The focal length is shared by two positive lenses, which can make light transmission smoother and reduce the difficulty of lens processing.

[0045] In this embodiment, the refractive index of the fourth lens 22 is higher than that of the third lens 21 and the fifth lens 23, respectively, and is suitable for adjusting coma; the fourth lens 22 is made of a low Abbe number material, and the third lens 21 and the fifth lens 23 are made of a high Abbe number material.

[0046] The second middle group 3 includes a sixth lens 31 and a seventh lens 32, respectively, and the third middle group 4 includes an eighth lens 41 and a ninth lens 42, respectively. The sixth lens 31, the seventh lens 32, the eighth lens 41 and the ninth lens 42 are sequentially arranged in a front-to-back manner along the optical path; the sixth lens 31 and the eighth lens 41 are arranged as negative lenses, suitable for providing negative optical power, and the seventh lens 32 and the ninth lens 42 are arranged as positive lenses, suitable for providing positive optical power;

[0047] Compared with the first middle group 2, the second middle group 3 and the third middle group 4 are located at a relatively gentle position of the optical path, and do not need to provide a large optical power. To ensure the best aberration correction effect, the principle of alternating positive and negative lenses should be followed. At the same time, the seventh lens 32 and the eighth lens 41 adjacent to the two are also alternately arranged as positive and negative lenses to achieve the effect of chromatic aberration correction. Further, since the ninth lens 42 of the third middle group 4 is close to the tenth lens 51 of the rear group unit 5, in order to improve the off-axis aberration correction capability of the rear group unit 5, there is a lens in the rear group unit 5 that cooperates with the tenth lens 51 to form a symmetrical structure. In order to meet the need of the rear group unit 5 to correct off-axis chromatic aberration, the tenth lens 51 has a lower refractive index than its symmetrical lens, so the optical power of the tenth lens 51 is relatively low. In order to supplement the optical power, the ninth lens 42 needs to be set as a positive lens to further supplement it, and then the positive and negative forms of other lenses in the second middle group 3 and the third middle group 4 can be confirmed respectively.

[0048] In this embodiment, the refractive index of the sixth lens 31 is greater than that of the seventh lens 32, and the refractive index of the eighth lens 41 is greater than that of the ninth lens 42; the sixth lens 31 and the eighth lens 41 are respectively made of low Abbe number materials, and the seventh lens 32 and the ninth lens 42 are respectively made of high Abbe number materials.

[0049] Preferably, the rear group unit 5 is arranged in a symmetrical double Gaussian structure, including a tenth lens 51, an eleventh lens 52, a twelfth lens 53 and a thirteenth lens 54 sequentially distributed along the optical path. The eleventh lens 52 and the twelfth lens 53 are arranged as negative lenses, suitable for providing negative optical power, and the tenth lens 51 and the thirteenth lens 54 are arranged as positive lenses, suitable for providing positive optical power.

[0050] When the numerical aperture is large, the asymmetric structure will affect the correction effect of coma. By setting the rear group unit 5 to be a symmetrical double Gaussian structure, the effect of correcting off-axis aberrations such as coma is further provided.

[0051] The refractive index of the thirteenth lens 54 is greater than that of the tenth lens 51, the eleventh lens 52 and the twelfth lens 53; the thirteenth lens 54 and the eleventh lens 52 are respectively made of low Abbe number materials, and the tenth lens 51 and the twelfth lens 53 are made of high Abbe number materials. Preferably, the eleventh lens 52 is made of special flint material.

[0052] Preferably, the focal length of the microscope objective is fx, the focal length of the first lens 11 is f1, 4.1≤f1 / fx≤4.5; the focal length of the second lens 12 is f2, 6.7≤f2 / fx≤7.1. Specifically, f1 / fx can be 4.1, 4.2, 4.3, 4.4 or 4.5, and f2 / fx can be 6.7, 6.8, 6.9, 7.0 or 7.1, etc.

[0053] It can be understood that f1 / fx can be less than 4.1 or greater than 4.5, and f1 / fx can be less than 6.7 or greater than 7.1.

[0054] Preferably, the focal length of the front group unit 1 is fa, 2.3≤fa / fx≤2.7, the focal length of the first middle group 2 is fb, 6.5≤fb / fx≤6.9, the focal length of the second middle group 3 is fc, 12.8≤fc / fx≤14.2, the focal length of the third middle group 4 is fd, 50≤fd / fx≤54, and the focal length of the rear group unit 5 is fe, -7.9≤fe / fx≤-7.5. Specifically, fa / fx can be 2.3, 2.4, 2.5, 2.6 or 2.7, fb / fx can be 6.5, 6.6, 6.7, 6.8 or 6.9, fc / fx can be 12.8, 13.0, 13.2, 13.4, 13.6, 13.8, 14.0 or 14.2, fd / fx can be 50, 51, 52, 53 or 54, and fe / fx can be -7.9, -7.8, -7.7, -7.6 or -7.5.

[0055] It can be understood that fa / fx can be less than 2.3 or greater than 2.7, fb / fx can be less than 6.5 or greater than 6.9, fc / fx can be less than 12.8 or greater than 14.2, fd / fx can be less than 50 or greater than 54, and fe / fx can be less than -7.9 or greater than -7.5.

[0056] Preferably, 3.9 mm ≤ fx ≤ 4.1 mm. Specifically, fx may be 3.9 mm, 3.95 mm, 4.00 mm, 4.05 mm or 4.1 mm.

[0057] It is understood that fx may be less than 3.9 mm or greater than 4.1 mm.

[0058] Preferably, the aperture of the microscope objective lens is NA, 0.8≤NA≤0.9, specifically, NA may be 0.8, 0.82, 0.84, 0.86, 0.88 or 0.9, etc.

[0059] It is understood that fx may be less than 0.8 or greater than 0.9.

[0060] In addition, preferably, the object field of the microscope objective is B, 0≤B≤0.4mm; specifically, B can be 0, 0.1mm, 0.2mm, 0.3mm or 0.4mm, etc. The distance between the first lens 11 and the object to be observed is C, C≥1.6mm, and C can be 1.6mm, 2.0mm, 2.4mm, 2.8mm, 3.2mm or larger. It can be understood that only one of 0≤B≤0.4mm and C≥1.6mm can be set.

[0061] It can be understood that B can be greater than 0.4 mm and C can be less than 1.6 mm.

[0062] like Figure 1 As shown in Table 1, preferably, the thirteenth lens 54 is an aspherical lens, the ninth lens 42 is an aspherical lens, and the fifth lens 23 is an aspherical lens. This arrangement is used to compensate for the aberration caused by the surface change caused by the large temperature difference. In addition, the other lenses in the microscope objective are preferably spherical structures.

[0063] In this embodiment, the preferred microscope objective lens parameters are shown in the following table:

[0064] Table 1 Microscope objective parameters

[0065]

[0066]

[0067] Preferably, the first lens 11 and the second lens 12 are configured as positive meniscus lenses, which jointly provide positive focal power, and the surface facing the object plane is concave; the third lens 21 is configured as a biconvex positive lens, which provides positive focal power; the fourth lens 22 is configured as a negative meniscus lens, which provides negative focal power, and the surface facing the object plane is concave; the fifth lens 23 is a biconvex positive lens, which provides positive focal power; the sixth lens 31 is configured as a negative meniscus lens, which provides negative focal power, and the surface facing the object plane is convex; the seventh lens 32 is configured as a biconvex positive lens, which provides positive focal power. The eighth lens 41 is configured as a meniscus negative lens, providing negative optical focal length, and its surface facing the object plane is convex; the ninth lens 42 is configured as a biconvex positive lens, providing positive optical focal length; the tenth lens 51 is configured as a meniscus positive lens, providing positive optical focal length, and its surface facing the object plane is convex; the eleventh lens 52 is configured as a meniscus negative lens, providing negative optical focal length, and its surface facing the object plane is convex; the twelfth lens 53 is configured as a biconcave negative lens, providing negative optical focal length; the thirteenth lens 54 is a meniscus positive lens, providing positive optical focal length, and its surface facing the object plane is concave.

[0068] In addition, the first lens 11 mainly provides positive spherical aberration, negative coma, negative astigmatism, negative field curvature, and negative axial chromatic aberration; the second lens 12 mainly provides positive spherical aberration, positive coma, positive astigmatism, positive field curvature, and negative axial chromatic aberration; the third lens 21 mainly provides positive spherical aberration, positive coma, positive astigmatism, positive field curvature, and negative axial chromatic aberration; the fourth lens 22 mainly provides negative spherical aberration, negative coma, negative astigmatism, negative field curvature, and positive axial chromatic aberration; the fifth lens 23 mainly provides positive spherical aberration, positive coma, positive astigmatism, positive field curvature, and negative axial chromatic aberration; the sixth lens 31 mainly provides negative spherical aberration, positive coma, positive astigmatism, negative field curvature, and positive axial chromatic aberration; the seventh lens 32 mainly provides positive spherical aberration, positive coma, positive astigmatism, negative field curvature, and positive axial chromatic aberration. The eighth lens element 41 mainly provides negative spherical aberration, positive coma, negative astigmatism, negative field curvature, and positive axial chromatic aberration; the ninth lens element 42 mainly provides positive spherical aberration, negative coma, positive astigmatism, positive field curvature, and negative axial chromatic aberration; the tenth lens element 51 mainly provides positive spherical aberration, negative coma, positive astigmatism, positive field curvature, and negative axial chromatic aberration; the eleventh lens element 52 mainly provides negative spherical aberration, negative coma, negative astigmatism, negative field curvature, and positive axial chromatic aberration; the twelfth lens element 53 mainly provides negative spherical aberration, positive coma, negative astigmatism, negative field curvature, and positive axial chromatic aberration; the thirteenth lens element 54 mainly provides positive spherical aberration, negative coma, positive astigmatism, positive field curvature, and negative axial chromatic aberration.

[0069] When the microscope objective lens is in the above preferred range and preferred structure, it is as follows:

[0070] The aberration curve of the microscope objective lens 0° field of view is as follows Figure 2 As shown, Figure 2The horizontal coordinates Py and Px represent the normalized pupil position, and the vertical coordinates ey and ex represent the vertical axis aberration. The maximum value of the vertical coordinate is 2.5um, and the minimum value is -2.5um. The left curve corresponds to the aberration curve of the beam in the meridian direction, and the right curve corresponds to the aberration curve of the beam in the sagittal direction. Figure 2 The aberration curves of different colors correspond to wavelengths of 450nm, 486nm, 545nm, 587nm, and 640nm respectively. Figure 2 In the pupil range of 0 to 0.8, the light aberration value is between 0 and ±0.25um, in the pupil range of 0.8 to 0.9, the light aberration value is between ±0.25um and ±0.5um, and in the pupil range of 0.9 to 1.0, the light aberration value is between ±0.5um and ±2um. The overall aberration value is small, and the imaging quality is excellent.

[0071] The wavefront aberration curve of the microscope objective lens at 0° field of view is as follows: Figure 3 As shown, Figure 3 The horizontal coordinates Py and Px represent the normalized pupil position, and the vertical coordinate w represents the wavefront aberration. The maximum value of the vertical coordinate is 0.3 times the wavelength, and the minimum value is -0.3 times the wavelength. The left curve corresponds to the wavefront aberration curve of the beam in the meridional direction, and the right curve corresponds to the wavefront aberration curve of the beam in the sagittal direction. Figure 3 The wavefront aberration curves of different colors correspond to wavelengths of 450nm, 486nm, 545nm, 587nm, and 640nm. The optical path difference in the pupil range of 0 to 0.5 is between 0 and ±0.12 times the wavelength, and the light aberration value in the pupil range of 0.5 to 1.0 is between ±0.12 and ±0.18 times the wavelength, and the overall optical path difference is small.

[0072] The MTF curve of the microscope objective is as follows: Figure 4 As shown, Figure 4 The horizontal axis is the spatial frequency, the unit is the number of line pairs per millimeter, and the vertical axis is the OTF modulus, which is the modulation transfer function MTF. The MTF curve is greater than 0.6 at 600lp / mm, greater than 0.4 at 1000lp / mm, and greater than 0.2 at 1600lp / mm. The overall value is close to the diffraction limit, indicating that the imaging quality is good.

[0073] The axial aberration curve of the microscope objective is as follows Figure 5 As shown, Figure 5 The horizontal axis is the system axial aberration, in mm, and the vertical axis is the normalized pupil coordinate. Figure 5 The wavefront aberration curves of different colors correspond to wavelengths of 450nm, 486nm, 545nm, 587nm, and 640nm. The axial chromatic aberration value at the main light position is 0.63um, which is less than λ / NA 2 , satisfying the apochromatic condition.

[0074] The field curvature and distortion curves of cryogenic microscope objectives are as follows: Figure 6 As shown, Figure 6 The left picture in the middle is the field curvature diagram. The horizontal axis is the field curvature value in um, and the vertical axis is the field of view in degrees. The field curvature curve of 545nm wavelength light meets The horizontal axis of the right figure is the percentage of distortion, and the vertical axis is the field of view, the unit is °, and the maximum distortion value of the edge field of view of 545nm wavelength light is <0.36%.

[0075] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A microscope objective lens, at least suitable for a temperature environment of 50K to 150K, characterized in that: include: The front group unit (1) comprises at least a first lens (11) and a second lens (12) which are arranged in sequence along the optical path, and are suitable for converging light and correcting spherical aberration; A middle group unit is arranged at the rear side of the optical path of the front group unit (1), comprising at least a first middle group (2) and a second middle group (3), and arranged adjacent to each other in sequence along the optical path, each middle group being provided with at least two lenses arranged at intervals, suitable for correcting chromatic aberration; A rear group unit (5), arranged at the rear side of the optical path of the middle group unit, comprises at least two lenses arranged at intervals, and is suitable for correcting off-axis chromatic aberration; Each lens included in the front group unit (1), the middle group unit and the rear group unit (5) is a single lens.

2. The microscope objective lens according to claim 1, characterized in that The first lens (11) and the second lens (12) are arranged as positive lenses and are arranged with arcs bent in the same direction, suitable for being concave toward the object to be observed, and jointly providing positive optical power.

3. The microscope objective lens according to claim 2, characterized in that: The refractive index of the first lens (11) is higher than that of the second lens (12); The first lens (11) is made of a material with a low Abbe number, and the second lens (12) is made of a material with a high Abbe number.

4. The microscope objective lens according to any one of claims 1 to 3, characterized in that: The middle group unit further comprises a third middle group (4), and the third middle group (4) is arranged at a distance along the optical path on the rear side of the second middle group (3).

5. The microscope objective lens according to claim 4, characterized in that: The first middle group (2) comprises a third lens (21), a fourth lens (22) and a fifth lens (23), which are arranged in sequence along the optical path, the fourth lens (22) being a negative lens and being suitable for providing negative optical power, and the third lens (21) and the fifth lens (23) being positive lenses and being suitable for providing positive optical power respectively; The refractive index of the fourth lens (22) is higher than that of the third lens (21) and the fifth lens (23), respectively, and is suitable for adjusting coma. The fourth lens (22) is made of a material with a low Abbe number, and the third lens (21) and the fifth lens (23) are made of a material with a high Abbe number.

6. The microscope objective lens according to claim 5, characterized in that: The second middle group (3) includes a sixth lens (31) and a seventh lens (32), and the third middle group (4) includes an eighth lens (41) and a ninth lens (42). The sixth lens (31), the seventh lens (32), the eighth lens (41) and the ninth lens (42) are sequentially arranged in a front-to-back manner along the optical path. The sixth lens (31) and the eighth lens (41) are arranged as negative lenses, suitable for providing negative optical power, and the seventh lens (32) and the ninth lens (42) are arranged as positive lenses, suitable for providing positive optical power. The refractive index of the sixth lens (31) is greater than that of the seventh lens (32), the refractive index of the eighth lens (41) is greater than that of the ninth lens (42), the sixth lens (31) and the eighth lens (41) are respectively made of a material with a low Abbe number, and the seventh lens (32) and the ninth lens (42) are made of a material with a high Abbe number.

7. The microscope objective lens according to claim 6, characterized in that: The rear group unit (5) is arranged in a symmetrical double Gaussian structure, comprising a tenth lens (51), an eleventh lens (52), a twelfth lens (53) and a thirteenth lens (54) sequentially distributed along the optical path, the eleventh lens (52) and the twelfth lens (53) being arranged in a negative lens configuration, suitable for providing negative optical power, and the tenth lens (51) and the thirteenth lens (54) being arranged in a positive lens configuration, suitable for providing positive optical power.

8. The microscope objective lens according to claim 7, characterized in that: The refractive index of the thirteenth lens (54) is greater than that of the tenth lens (51), the eleventh lens (52) and the twelfth lens (53); The thirteenth lens (54) and the eleventh lens (52) are respectively made of low Abbe number materials, and the tenth lens (51) and the twelfth lens (53) are made of high Abbe number materials.

9. The microscope objective lens according to any one of claims 5 to 8, characterized in that: The focal length of the microscope objective is fx, the focal length of the first lens (11) is f1, and 4.1≤f1 / fx≤4.5; The focal length of the second lens (12) is f2, 6.7≤f2 / fx≤7.

1.

10. The microscope objective lens according to claim 9, characterized in that: The focal length of the front group unit (1) is fa, 2.3≤fa / fx≤2.7, the focal length of the first middle group (2) is fb, 6.5≤fb / fx≤6.9, the focal length of the second middle group (3) is fc, 12.8≤fc / fx≤14.2, the focal length of the third middle group (4) is fd, 50≤fd / fx≤54, and the focal length of the rear group unit (5) is fe, -7.9≤fe / fx≤-7.

5.

11. The microscope objective lens according to claim 9, characterized in that: 3.9mm≤fx≤4.1mm.

12. The microscope objective lens according to claim 11, characterized in that: The aperture of the microscope objective lens is NA, 0.8≤NA≤0.

9.

13. The microscope objective lens according to claim 12, characterized in that: The object field of view of the microscope objective lens is B, 0≤B≤0.4mm; and / or the distance between the first lens (11) and the object to be observed is C, C≥1.6mm.

14. The microscope objective according to claim 7 or 8, characterized in that: The thirteenth lens (54) is an aspherical lens, the ninth lens (42) is an aspherical lens, and the fifth lens (23) is an aspherical lens.

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