CN117492188A - Afocal zoom optical system and microscope imaging system - Google Patents

Abstract

The invention provides a afocal zoom optical system and a microscope imaging system, comprising: a front fixed lens group, a zoom lens group, a compensation lens group and a rear fixed lens group which are sequentially arranged along a light path from an object space to an image space; the distance between the front fixed lens group and the system entrance pupil is fixed, and the distance between the rear fixed lens group and the system exit pupil is fixed; the front fixed lens group has positive focal power, the variable power lens group has negative focal power, the compensation lens group has positive focal power, the rear fixed lens group has positive focal power, and the focal power of the second lens group is the largest. The afocal zoom optical system and the microscope imaging system realize large zoom ratio while correcting various aberrations, and are beneficial to expanding the application scene of the ultraviolet-visible microscope imaging system.

Description

Afocal zoom optical system and microscope imaging system

Technical Field

The invention relates to the technical field of optical lenses, in particular to a afocal zoom optical system and a microscope imaging system.

Background

With the rise of modern industry, in the fields of semiconductor industry, biological identification detection and the like, more and more application scenes need to realize high-precision detection by means of a microscopic imaging system. Meanwhile, the detection requirements are various, the visual field range is greatly changed, and the traditional fixed-magnification microscope system cannot realize free switching in different visual field ranges because of single visual field, so that certain limitation exists in application.

The infinite conjugate microscope system is mainly composed of a microscope objective and a tube lens, and the change of vertical magnification is realized by changing the focal length of the objective or the tube lens. The method comprises the steps that a switching type tube mirror structure is adopted, and the risk of losing an observation target exists in the process of switching the multiplying power; also, the need for several system magnifications means that a corresponding number of tube mirror systems with different focal lengths are required, which results in a larger lateral dimension of the complete set of optical systems; multiple tube mirrors with different focal lengths also add significant manufacturing costs. The problems can be significantly improved by using a set of optical systems to switch the system vertical axis magnification among multiple magnifications; the afocal system is used as a zoom mechanism and is added with an objective lens and a tube lens to form an infinite conjugate distance microscopic imaging system, but the afocal system is limited by insufficient choice of optical materials in the ultraviolet region and still generally adopts a structure form of transverse switching of the afocal system with various angle amplification rates.

Therefore, how to design an ultraviolet-visible afocal zoom optical system to match with a large NA high magnification microscopic system to realize a large zoom ratio and excellent image quality and expand the application scene of the large NA aperture high magnification ultraviolet-visible microscopic imaging system has become one of the problems to be solved by the technicians in the field.

It should be noted that the foregoing description of the background art is only for the purpose of providing a clear and complete description of the technical solution of the present invention and is presented for the convenience of understanding by those skilled in the art. The above-described solutions are not considered to be known to the person skilled in the art simply because they are set forth in the background of the invention section.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a afocal zoom optical system and a microscope imaging system, which are used for solving the problem of limited application scenarios of the ultraviolet-visible microscope imaging system in the prior art.

To achieve the above and other related objects, the present invention provides an afocal magnification-varying optical system suitable for ultraviolet and visible light bands, the afocal magnification-varying optical system comprising at least:

a front fixed lens group, a zoom lens group, a compensation lens group and a rear fixed lens group which are sequentially arranged along a light path from an object space to an image space; the distance between the front fixed lens group and the system entrance pupil is fixed, and the distance between the rear fixed lens group and the system exit pupil is fixed; the front fixed lens group has positive focal power, the variable power lens group has negative focal power, the compensation lens group has positive focal power, the rear fixed lens group has positive focal power, and the focal power of the second lens group is the largest.

Optionally, the angle magnification of the afocal variable magnification optical system varies with the movement of the variable magnification lens group and the compensation lens group on the optical axis;

when the variable magnification lens group and the compensation lens group move oppositely along the optical axis direction, the angle amplification rate of the afocal variable magnification optical system is changed from low power to high power; when the variable magnification lens group and the compensation lens group move oppositely along the optical axis direction, the angle amplification rate of the afocal variable magnification optical system is changed from high magnification to low magnification.

Optionally, the focal length of each lens group satisfies the following relation:

0.62<|f1/f3|<0.75，0.46<|f2/f3|<0.54，1.1<|f4/f3|<0.9；

wherein f1 is the focal length of the front fixed lens group, f2 is the focal length of the variable magnification lens group, f3 is the focal length of the compensation lens group, and f4 is the focal length of the rear fixed lens group.

Optionally, the distance between the front fixed lens group and the system entrance pupil satisfies the following relation:

0.3<|L1/L|<0.4；

the distance between the rear fixed lens group and the system exit pupil satisfies the following relationship:

0.15<|L5/L|<0.22；

wherein L is the total length of the afocal variable magnification optical system, L1 is the distance between the front fixed lens group and the system entrance pupil, and L5 is the distance between the rear fixed lens group and the system exit pupil.

Optionally, the front fixed lens group includes a first lens, a second lens and a third lens sequentially arranged from an object side to an image side; the first lens is a positive focal power biconvex lens, the second lens is a positive focal power biconvex lens, and the third lens is a negative focal power biconcave lens.

Optionally, the zoom lens group includes a fourth lens, a fifth lens and a sixth lens sequentially arranged from an object side to an image side; the fourth lens is a positive focal power meniscus lens, the fifth lens is a biconcave lens with negative focal power, the sixth lens is a meniscus lens with positive focal power, and the fifth lens and the sixth lens are glued.

Optionally, the compensation lens group includes a seventh lens and an eighth lens sequentially arranged from an object side to an image side; the seventh lens is a meniscus lens with negative focal power, and the eighth lens is a biconvex lens with positive focal power.

Optionally, the rear fixed lens group includes a ninth lens and a tenth lens sequentially disposed from an object side to an image side; the ninth lens is a meniscus lens with negative focal power, and the tenth lens is a biconvex lens with positive focal power.

More optionally, each lens is a spherical lens.

More optionally, the material of each lens has a near ultraviolet transmittance of not less than 70%.

Optionally, the afocal magnification-varying optical system has an operating wavelength range of 365nm to 487nm.

Optionally, the zoom ratio of the afocal zoom optical system satisfies: 1.75< M <2.5, wherein M is the magnification ratio of the afocal magnification-varying optical system.

Optionally, the afocal magnification-varying optical system further comprises a diaphragm disposed at the system entrance pupil for limiting a diameter of the system entrance pupil.

More optionally, the diameter of the system entrance pupil satisfies 6.35mm < D1<7.35mm, where D1 is the diameter of the system entrance pupil.

To achieve the above and other related objects, the present invention also provides a microscope imaging system including at least:

an objective lens, a tube lens and the afocal zoom optical system;

the objective lens is arranged at the object side of the afocal zoom optical system, and the pupil surface of the objective lens is overlapped with the entrance pupil of the afocal zoom optical system;

the tube mirror is arranged on the image side of the afocal zoom optical system, and the entrance pupil of the tube mirror coincides with the exit pupil of the afocal zoom optical system.

Optionally, the focal length of the tube mirror is a fixed value.

As described above, the afocal magnification-varying optical system and the microscopic imaging system of the present invention have the following advantageous effects:

1. compared with the scheme that zoom of the microscopic imaging system is realized by switching back and forth through a plurality of afocal systems inserted between the objective lens and the tube lens, the afocal zoom optical system provided by the invention has the advantages that the single afocal zoom optical system realizes switching of a plurality of zoom positions by moving the zoom lens group and the compensation lens group along the optical axis, so that focusing of the whole microscopic imaging system is realized, the application scene of the microscopic imaging system is expanded, and the afocal zoom optical system has better pupil and system image surface stability;

2. compared with the scheme of a plurality of afocal zoom systems, the afocal zoom optical system provided by the invention has fewer lens sheets, and the processing and manufacturing cost is obviously reduced.

3. All lenses in the afocal zoom optical system are spherical lenses, so that the afocal zoom optical system is convenient to process and detect, and has strong engineering realizability.

Drawings

Fig. 1 is a schematic diagram showing the structure of an afocal magnification-varying optical system according to the present invention.

Fig. 2 is a schematic view showing the structure of the afocal magnification-varying optical system of the present invention at different angular magnification positions.

Fig. 3 is a graph showing a modulation transfer function curve of the afocal magnification-varying optical system of the present invention at a high magnification.

Fig. 4 shows a schematic view of a spot array at a high magnification of the afocal magnification-varying optical system of the present invention.

Fig. 5 is a schematic diagram showing a modulation transfer function curve of the afocal magnification-varying optical system of the present invention at a medium magnification.

Fig. 6 shows a schematic view of a spot array at a medium magnification of the afocal magnification-varying optical system of the present invention.

Fig. 7 is a schematic diagram showing a modulation transfer function curve of the afocal magnification-varying optical system of the present invention at a low magnification.

Fig. 8 shows a schematic view of a point array at a low magnification of the afocal magnification-varying optical system of the present invention.

Fig. 9 shows a schematic structural diagram of a microscope imaging system according to the present invention.

Description of element reference numerals

1. Afocal zoom optical system

11. Front fixed lens group

12. Variable magnification lens group

13. Compensation lens group

14. Rear fixed lens group

1a first lens

1b second lens

1c third lens

1d fourth lens

1e fifth lens

1f sixth lens

1g seventh lens

1h eighth lens

1i ninth lens

1j tenth lens

2. Objective lens

3. Tube mirror

Detailed Description

Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.

Please refer to fig. 1-9. It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.

Afocal systems, also known as telescopic systems, are often used for measuring, expanding beams, zooming, etc. as an important configuration in optical systems. The simplest afocal system consists of a front group lens and a rear group lens, the focal length of the front group lens being f _{Front part} The focal length of the rear group lens is f _{Rear part (S)} For both of these configurations, the image side focal point of the front lens group coincides with the object side focal point of the rear lens group, i.e., the optical interval Δ= 0, so that the parallel light is emitted as parallel light after entering the afocal system, and the angle expansion ratio γ=f of the afocal system _{Front part} /f _{Rear part (S)} . Whether a plurality of switchable afocal systems with different angle amplification ratios are combined with a subsequent fixed-focus tube lens or a single afocal system is combined with the subsequent fixed-focus tube lens, the switchable afocal systems can be combined into a complete zoom tube lens system, and compared with the method that the tube lens independently realizes focal length change (two design ideas are adopted, one is to switch the whole tube lens or a part of the tube lens to realize zoom, and the other is to continuously zoom), the design method has the following advantages: the image space telecentric light path needs an entrance pupil to be positioned at the front focal plane of the system, and if the tube lens independently realizes zooming, the image space light can be telecentric only at a certain zooming position; however, for the composite system of the afocal zoom system and the fixed-focus tube lens, as the zoom process of the whole system is realized by changing the angle amplification rate gamma of the afocal system, the pupil plane position of the fixed-focus tube lens is always kept constant, the system is overturned in the whole zoomThe image telecentricity can be kept all the time in the process, which is important for industrial measurement and is also helpful for improving the uniformity of the illumination of the image plane of the system.

The zoom afocal system is realized by a zoom system, and the structure form can adopt three-component structures of a fixed group, a zoom group and a compensation group and four-component structures of a front fixed group, a zoom group, a compensation group and a rear fixed group. For the three-component structure, when the variable-magnification group moves relative to the fixed group, the equivalent focal lengths of the variable-magnification group and the fixed group are continuously changed, so that a new focus is generated, and when the compensation group moves along with the variable-magnification group, the new focus is stabilized at the focus of the compensation group. The three-component zoom afocal system can adopt structural forms of positive-negative-positive, negative-positive-negative and the like; for the four-component structure, the front fixed group, the zoom group and the compensation group form a zoom system, when the zoom group and the compensation group move relative to the fixed group, the image plane position is kept unchanged and stabilized on the front focal plane of the rear fixed group, and the angle amplification rate of the whole afocal system can be changed. The front fixed group, the zoom group and the compensation group of the four-component zoom afocal system are the front group, so that the incident parallel light is imaged on the front focal plane of the rear group (rear fixed group), and the conjugate distance of the system is kept unchanged. The four-component afocal zoom system can be divided into a positive-group compensation structure of "positive-negative-positive" and a negative-group compensation structure of "positive-negative-positive" according to the optical power of the compensation group. Since the front fixed group focal length of the positive group compensation is larger, and the secondary spectrum at high power is mainly determined by the front fixed group focal length, the positive group compensation is smaller relative to the secondary spectrum of the latter.

It should be noted that the ultraviolet afocal optical system and the visible afocal optical system have great differences in design structure, application scene and materials used. The visible light afocal zoom system with large zoom ratio includes the first lens group, the second lens group, the diaphragm, the third lens group, the fourth lens group and the fifth lens group arranged from the object side to the image side, and the visible light afocal zoom system structure has great difference from the ultraviolet afocal zoom system structure, and forms a zoom microscope lens with the front microscope objective, and realizes great zoom ratio under the condition of sacrificing image quality. However, in order to fully exert the resolution of the ultraviolet microscopic system, the ultraviolet microscopic imaging system has practical application value only under high magnification; furthermore, when a afocal magnification-varying optical system is inserted as an intermediate member between the objective lens and the tube lens of an infinite conjugate microscope system, the entrance pupil and the exit pupil of the afocal magnification-varying system are necessarily located at both ends of the optical system, and the entrance pupil coincides with the pupil of the microscope objective lens, and the exit pupil coincides with the tube lens, and for such pupil-pupil system, it is necessary to consider correcting both aberration and pupil aberration, which is a problem that the pupil-pupil system must consider; in addition, one of the factors limiting the design of ultraviolet optical systems is the low ultraviolet transmittance of conventional optical materials below 400nm, and the optical materials commonly used in ultraviolet optical systems include calcium fluoride (CaF 2), ultraviolet fused silica (UVFS), and some i-ray (365 nm wavelength) optical glasses. The refractive index of the materials is generally low, and the choice is small, so that a certain difficulty exists in designing and manufacturing the ultraviolet zooming system.

Based on the above, the invention provides a afocal zoom optical system, which is suitable for ultraviolet light and visible light wave bands (the working wave band of the system is 365nm-487nm as an example), realizes large zoom ratio while correcting various aberrations, and is beneficial to expanding the application scene of an ultraviolet-visible microscopic imaging system.

As shown in fig. 1, the afocal magnification-varying optical system 1 of the present invention includes: a front fixed lens group 11, a variable magnification lens group 12, a compensation lens group 13 and a rear fixed lens group 14 which are arranged in order along the optical path from the object side to the image side. Wherein, the distance L1 between the front fixed lens group 11 and the system entrance pupil is fixed, and the front fixed lens group 11 has positive focal power. The variable power lens group 12 is used for realizing a variable power function, has negative focal power, and the focal power of the variable power lens group 12 is the largest (the largest absolute value) among the four lens groups; the variable magnification lens group 12 is movable along the optical axis between the front fixed lens group 11 and the compensation lens group 13, i.e., the distance L2 between the front fixed lens group 11 and the variable magnification lens group 12 is variable, and is adaptively adjusted according to the variable magnification ratio. The compensation lens group 13 is used for compensation and has positive focal power; the compensation lens group 13 can move along the optical axis between the variable power lens group 12 and the rear fixed lens group 14, namely, the distance L3 between the variable power lens group 12 and the compensation lens group 13 is not fixed, the distance L4 between the compensation lens group 13 and the rear fixed lens group 14 is not fixed, and the adjustment is carried out according to actual needs. The distance L5 between the rear fixed lens group 14 and the system exit pupil is fixed, and the rear fixed lens group 14 has positive optical power.

Specifically, in the present embodiment, the distance L1 of the front fixed lens group 11 from the system entrance pupil satisfies: 0.3< |L1/L| <0.4; the distance L5 between the rear fixed lens group 14 and the system exit pupil satisfies: 0.15< |L5/L| <0.22. Where L is the total length of the afocal magnification-varying optical system 1. The entrance pupil of the afocal magnification-varying optical system of the present invention is located at the far front end of the system, and the exit pupil is located at the far rear end of the system.

The power values of the front fixed lens group 11, the variable power lens group 12, the compensation lens group 13 and the rear fixed lens group 14 are set according to actual needs, and the positive and negative relationships defined by the present invention and the maximum power of the variable power lens group are satisfied, which is not described in detail herein.

Specifically, in the present embodiment, the focal length of the front fixed lens group 11 is f1, the focal length of the variable magnification lens group 12 is f2, the focal length of the compensation lens group 13 is f3, and the focal length of the rear fixed lens group 14 is f4; the focal length of each lens group satisfies the following relation: 0.62< |f1/f3| <0.75,0.46< |f2/f3| <0.54,1.1< |f4/f3| <0.9; the specific values of the focal lengths of the lens groups are set according to actual requirements.

Specifically, as shown in fig. 1, in the present embodiment, the front fixed lens group 11 includes a first lens 1a, a second lens 1b, and a third lens 1c, which are disposed in order from the object side to the image side; the first lens 1a is a positive-power biconvex lens, the second lens 1b is a positive-power biconvex lens, and the third lens 1c is a negative-power biconcave lens.

Specifically, as shown in fig. 1, in the present embodiment, the magnification-varying lens group 12 includes a fourth lens 1d, a fifth lens 1e, and a sixth lens 1f, which are disposed in order from the object side to the image side; the fourth lens 1d is a positive power meniscus lens, the fifth lens 1e is a biconcave lens with negative power, the sixth lens 1f is a meniscus lens with positive power, and the fifth lens 1e and the sixth lens 1f are cemented to form a cemented lens.

Specifically, as shown in fig. 1, in the present embodiment, the compensation lens group 13 includes a seventh lens 1g and an eighth lens 1h, which are disposed in order from the object side to the image side; the seventh lens 1g is a meniscus lens with negative focal power, the eighth lens 1h is a biconvex lens with positive focal power, and the seventh lens 1g and the eighth lens 1h form a pair of positive and negative lenses, which can be used for eliminating residual chromatic aberration.

Specifically, as shown in fig. 1, in the present embodiment, the rear fixed lens group 14 includes a ninth lens 1i and a tenth lens 1j disposed in order from the object side to the image side; the ninth lens 1i is a meniscus lens with negative focal power, the tenth lens 1j is a biconvex lens with positive focal power, and the ninth lens 1i and the tenth lens 1j also form a pair of positive and negative lenses in the same way, so that residual chromatic aberration can be further eliminated.

It should be noted that, the front fixed lens group 11 and the variable magnification lens group 12 bear larger optical power, which is determined by the structural characteristics of the positive group compensation four-component afocal variable magnification system, and the secondary spectrum at high magnification is mainly introduced by the variable magnification lens group, so the front fixed lens group and the variable magnification lens group are relatively complex in structure. The number, the types and the arrangement positions of the lenses contained in each lens group are not limited to the embodiment, and the combination mode capable of meeting the focal length relation and the aberration compensation of each lens group is applicable to the invention; the zoom lens group bears larger focal power and has larger light ray folding angle, and can be realized by other lens combination modes, but other combination modes can be more complex than the combination modes provided by the embodiment; the compensating lens group and the rear fixed lens group are required to meet the achromatic requirement; and are not described in detail herein. Because the refractive index of the ultraviolet optical material is generally low, the front fixed lens group, the variable magnification lens group, the compensating lens group and the rear fixed lens group obtained by adopting the lens combination of the embodiment have the advantages that the focal power separation (increasing the number of lenses) reduces the surface curvature of the lens, and the balance of system aberration is facilitated. In this embodiment, each lens is a spherical lens, and air spaces are formed between each lens, and in actual use, each lens may be configured as an aspherical lens as required, and the space between each lens may also use other light-transmitting media, which is not limited to this embodiment.

As shown in fig. 1, as another implementation manner of the present invention, the afocal magnification-varying optical system 1 further includes a diaphragm (not shown in the drawing) disposed at the system entrance pupil for limiting the diameter of the system entrance pupil. In this embodiment, the diameter D1 of the system entrance pupil satisfies 6.35mm < D1<7.35mm, including but not limited to 6.8mm.

As shown in fig. 1, the zoom ratio m=m2/M1 of the afocal zoom optical system 1 of the present invention, where M1 is the minimum angular magnification of the afocal zoom optical system 1 of the present invention, and M2 is the maximum angular magnification of the afocal zoom optical system 1 of the present invention; in the present embodiment, the variable magnification ratio M of the afocal variable magnification optical system 1 of the present invention satisfies: 1.75< M <2.5, as an example, m=2.

The imaging performance of the afocal zoom optical system 1 reaches the diffraction limit, pupil aberration is well corrected, the working wavelength range is 365nm-487nm, and the maximum incident parallel light angle of view is 5.71 degrees, so that the application scene of the ultraviolet-visible microscopic imaging system is favorably expanded. Because the working band range of the afocal zoom optical system 1 of the present invention is wider, the short wave end reaches near ultraviolet, and the transmittance of the conventional optical material in the ultraviolet band is lower, so in order to fully utilize 365nm spectral energy, in this embodiment, optical materials with higher near ultraviolet transmittance are selected to prepare each lens, and as an example, the material of each lens has a near ultraviolet transmittance of not less than 70% (e.g., 75%, 80%, 85%, 90%, 95%), including but not limited to calcium fluoride glass, PSK50, I-wire glass PBM18Y, I-wire glass BAL35Y, I-wire glass H-FK71, I-wire glass F4GTI, and I-wire glass H-K9LGT, which are not described herein in detail.

The performance of the afocal magnification-varying optical system 1 of the present invention will be described below with reference to a specific example.

In this specific example, the afocal magnification-varying optical system 1 has an operating wavelength range of 365nm to 487nm, an entrance pupil diameter of 6.8mm, a maximum object field of view of 4.3 degrees, three magnifications of 1, 1.5 and 2, a maximum compatible na=0.85, and an object field of view of 0.6 mm.

Specifically, the angle-magnification of the afocal magnification-varying optical system 1 of the present invention varies with the movement of the magnification-varying lens group 12 and the compensation lens group 13 on the optical axis, and different angle-magnification is achieved by moving the magnification-varying lens group 12 and the compensation lens group 13 along the optical axis; the variable magnification lens group 12 and the compensation lens group 13 move back to back along the optical axis direction, the angular magnification is changed from low power to high power, and the variable magnification lens group 12 and the compensation lens group 13 move towards each other along the optical axis direction, so that the angular magnification is changed from high power to low power. As shown in fig. 2, the uppermost afocal magnification-varying optical system 1 has a magnification of 1 magnification; the intermediate afocal variable magnification optical system 1 has a magnification of 1.5 times, with respect to the uppermost afocal variable magnification optical system 1, in which the variable magnification lens group 12 moves toward the object space and the compensation lens group 13 moves toward the image space (i.e., moves back to back); the lowermost afocal magnification-varying optical system 1 has a magnification of 2-fold angle, wherein the magnification-varying lens group 12 is further moved toward the object space and the compensation lens group 13 is further moved toward the image space (i.e., moved back to back) with respect to the intermediate afocal magnification-varying optical system 1.

In this specific example, the center-to-center distance from the system entrance pupil to the front surface of the first lens 1a (i.e., the distance L1 from the front fixed lens group 11 to the system entrance pupil) is set to 150mm from the object side to the image side along the light propagation direction. The radius of the front surface of the first lens 1a is set to 85.590mm, the radius of the rear surface of the first lens 1a is set to-101.800 mm, the center-to-center distance between the front surface and the rear surface of the first lens 1a is set to 6mm, and the center-to-center distance between the rear surface of the first lens 1a and the front surface of the second lens 1b is set to 0.200mm; the radius of the front surface of the second lens 1b is set to 54.893mm, and the radius of the rear surface of the second lens 1b is set to 73.877mm; the center-to-center distance between the front surface and the rear surface of the second lens 1b is set to 6mm, and the center-to-center distance between the rear surface of the second lens 1b and the front surface of the third lens 1c is set to 0.226mm; the radius of the front surface of the third lens 1c is set to be-64.876 mm, and the radius of the rear surface of the third lens 1c is set to be 116.206mm; the center-to-center distance between the front surface and the rear surface of the third lens 1c was set to 3.146mm, and the center-to-center distance between the rear surface of the third lens 1c and the front surface of the fourth lens 4 (i.e., the distance L2 between the front fixed lens group 11 and the variable magnification lens group 12) was set to 15.314mm, 20.244mm, and 27.260mm (corresponding to three different magnification positions of 1-fold, 1.5-fold, and 2-fold, respectively). The radius of the front surface of the fourth lens 1d is set to 22.694mm, and the radius of the rear surface of the fourth lens 1d is set to 22.332mm; the center-to-center distance between the front surface and the rear surface of the fourth lens 1d is set to 3.748mm, and the center-to-center distance between the rear surface of the fourth lens 1d and the front surface of the fifth lens 1e is set to 3.650mm; the radius of the front surface of the fifth lens 1e is set to be-185.566 mm, and the radius of the rear surface of the fifth lens 1e is set to be 18.759mm; the center-to-center distance between the front surface and the rear surface of the fifth lens 1e is set to 3.513mm; the radius of the front surface of the sixth lens 1f is set to 18.759mm, and the radius of the rear surface of the sixth lens 1f is set to 28.032mm; the center-to-center distance between the front surface and the rear surface of the sixth lens 1f is set to 3.853mm; the fifth lens 1e and the sixth lens 1f are cemented to form a first cemented lens group; the center-to-center distances between the rear surface of the sixth lens 1f and the front surface of the seventh lens 1g (i.e., the distance L3 between the variable magnification lens group 12 and the compensation lens group 13) were set to 90.330mm, 64.670mm, and 34.916mm (corresponding to three different magnification positions of 1-fold, 1.5-fold, and 2-fold, respectively). The front surface radius of the seventh lens 1g is set to 129.851mm, and the rear surface radius of the seventh lens 1g is set to 41.722mm; the center-to-center distance between the front surface and the rear surface of the seventh lens 1g was set to 6.000mm, and the center-to-center distance between the rear surface of the seventh lens 1g and the front surface of the eighth lens 1h was set to 5.215mm; the radius of the front surface of the eighth lens 1h is set to 51.597mm, and the radius of the rear surface of the eighth lens 1h is set to-85.090 mm; the center-to-center distance between the front surface and the rear surface of the eighth lens 1h is set to 7.467mm; the center-to-center distances between the rear surface of the eighth lens 1h and the front surface of the ninth lens 1i (i.e., the distance L4 between the compensation lens group 13 and the rear fixed lens group 14) are set to 15.145mm, 35.875mm and 58.614mm (corresponding to 1-fold, 1.5-fold and 2-fold three different magnification positions, respectively). The radius of the front surface of the ninth lens 1i is set to 77.480mm, and the radius of the rear surface of the ninth lens 1i is set to 33.355mm; the center-to-center distance between the front surface and the rear surface of the ninth lens 1i is set to 6.000mm, and the center-to-center distance between the rear surface of the ninth lens 1i and the front surface of the tenth lens 1j is set to 16.517mm; the radius of the front surface of the tenth lens 1j is set to 53.393mm, and the radius of the rear surface of the tenth lens 1j is set to-53.393 mm; the center-to-center distance between the front surface and the rear surface of the tenth lens 1j is set to 8mm, and the center distance between the rear surface of the tenth lens 1j and the system exit pupil (i.e., the distance L5 between the rear fixed lens group 14 and the system exit pupil) is set to 90.315mm.

In this specific example, the refractive index of the first lens 1a is set to 1.5575, and the dispersion coefficient is set to 67.283; the refractive index of the second lens 1b was set to 1.4338 and the dispersion coefficient was set to 94.996; the refractive index of the third lens 1c was set to 1.5955, and the dispersion coefficient was set to 38.767. The refractive index of the fourth lens 1d is set to 1.4565, and the dispersion coefficient is set to 90.274; the refractive index of the fifth lens 1e is set to 1.4997, and the dispersion coefficient is set to 62.072; the refractive index of the sixth lens 1f is set to 1.6201, and the dispersion coefficient is set to 36.431. The refractive index of the seventh lens 1g was set to 1.6483 and the dispersion coefficient was set to 33.841; the refractive index of the eighth lens 1h is set to 1.5891, and the dispersion coefficient is set to 61.233. The refractive index of the ninth lens 1i is set to 1.6201 and the dispersion coefficient is set to 36.431; the refractive index of the tenth lens 1j was set to 1.4338, and the dispersion coefficient was set to 67.283.

In this specific example, the material of the first lens 1a is PSK50, the materials of the second lens 1b and the tenth lens 1j are calcium fluoride glass, the material of the third lens 1c is I-wire glass PBM18Y, the material of the fourth lens 1d is I-wire glass H-FK71, the material of the fifth lens 1e is I-wire glass H-K9LGT, the material of the sixth lens 1F is I-wire glass F4GTI, the material of the seventh lens is SF12, and the material of the eighth lens 1H is I-wire glass BAL35Y.

In this specific example, the focal length f1 of the front fixed lens group 11 is set to 76.89mm, the focal length f2 of the variable magnification lens group 12 is set to-59.92 mm, the focal length f3 of the compensation lens group 13 is set to 115.12mm, and the focal length f4 of the rear fixed lens group 14 is set to 121.66mm.

Since the afocal magnification-varying optical system 1 of the present invention cannot be imaged alone, an ideal lens with a focal length f=200 mm was added as a tube lens after the afocal magnification-varying optical system 1 of the present invention in order to evaluate the image quality. A modulation transfer function curve (MTF) of the afocal magnification-varying optical system 1 of the present invention at a high magnification (2-fold) is shown in fig. 3, and a point chart of the afocal magnification-varying optical system 1 of the present invention at a high magnification (2-fold) is shown in fig. 4; as shown in fig. 5, the modulation transfer function curve of the afocal magnification-varying optical system 1 of the present invention at the intermediate magnification (1.5 times) is shown, and as shown in fig. 6, the spot diagram of the afocal magnification-varying optical system 1 of the present invention at the intermediate magnification (1.5 times) is shown; fig. 7 shows a modulation transfer function curve of the afocal magnification-varying optical system 1 of the present invention at a low magnification (1-fold), and fig. 8 shows a plot of points of the afocal magnification-varying optical system 1 of the present invention at a low magnification (1-fold). As can be seen from fig. 3 to 8, the diffraction limit cut-off frequency of the afocal magnification-varying optical system 1 of the present invention decreases with an increase in magnification, and the airy radius increases with an increase in magnification; the RMS radius of the point diagram of the full view field and the full magnification is basically smaller than one third of the Airy spot radius, and the MTF curve is close to the diffraction limit, so that the afocal magnification-varying optical system 1 has better image quality.

It should be noted that, specific parameters of the afocal zoom optical system 1 according to the present invention are set according to actual needs, and are not limited to the numerical values given in the above specific examples.

As shown in fig. 9, the present invention also provides a microscope imaging system including:

the invention relates to an afocal magnification-varying optical system 1, an objective lens 2 and a tube lens 3.

As shown in fig. 9, the objective lens 2 is disposed on the object side of the afocal variable magnification optical system 1 of the present invention, and the pupil plane of the objective lens 2 coincides with the entrance pupil of the afocal variable magnification optical system 1 of the present invention.

As shown in fig. 9, the tube mirror 3 is provided on the image side of the afocal variable magnification optical system 1 of the present invention, and the entrance pupil of the tube mirror 3 coincides with the exit pupil of the afocal variable magnification optical system 1 of the present invention. In the present embodiment, the focal length of the tube mirror 3 is set to a fixed value, including but not limited to 200mm.

Specifically, the afocal magnification-varying optical system 1 of the present invention is interposed as an intermediate member between the objective lens 2 and the tube lens 3, and achieves magnification variation of the entire system by changing the angular magnification of the incident parallel light and the outgoing parallel light; the afocal zoom optical system 1, the objective lens 2 and the tube lens 3 form an infinite conjugate distance microscopic imaging system, so that the microscopic imaging system can always keep the constant system image plane position and telecentricity, and the entrance pupil and the exit pupil of the afocal zoom optical system are kept external. The afocal magnification-varying optical system 1 of the invention is matched with a subsequent tube lens assembly and a front microscope objective lens to realize imaging, wherein the objective lens 2 and the tube lens 3 are components of an infinite conjugate microscopic imaging system well known in the industry, specific structures are not described in detail herein, and the afocal magnification-varying optical system 1 of the invention can be matched for imaging.

In summary, the present invention provides a afocal zoom optical system and a microscope imaging system, comprising: a front fixed lens group, a zoom lens group, a compensation lens group and a rear fixed lens group which are sequentially arranged along a light path from an object space to an image space; the distance between the front fixed lens group and the system entrance pupil is fixed, and the distance between the rear fixed lens group and the system exit pupil is fixed; the front fixed lens group has positive focal power, the variable power lens group has negative focal power, the compensation lens group has positive focal power, the rear fixed lens group has positive focal power, and the focal power of the second lens group is the largest. The afocal zoom optical system and the microscope imaging system realize large zoom ratio while correcting various aberrations, and are beneficial to expanding the application scene of the ultraviolet-visible microscope imaging system. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims (16)

1. An afocal zoom optical system suitable for ultraviolet and visible light bands, characterized in that it comprises at least:

a front fixed lens group, a zoom lens group, a compensation lens group and a rear fixed lens group which are sequentially arranged along a light path from an object space to an image space; the distance between the front fixed lens group and the system entrance pupil is fixed, and the distance between the rear fixed lens group and the system exit pupil is fixed; the front fixed lens group has positive focal power, the variable power lens group has negative focal power, the compensation lens group has positive focal power, the rear fixed lens group has positive focal power, and the focal power of the second lens group is the largest.

2. The afocal magnification-varying optical system according to claim 1, wherein: the angle amplification rate of the afocal zoom optical system changes along with the movement of the zoom lens group and the compensation lens group on the optical axis;

when the variable magnification lens group and the compensation lens group move oppositely along the optical axis direction, the angle amplification rate of the afocal variable magnification optical system is changed from low power to high power; when the variable magnification lens group and the compensation lens group move oppositely along the optical axis direction, the angle amplification rate of the afocal variable magnification optical system is changed from high magnification to low magnification.

3. The afocal magnification-varying optical system according to claim 1, wherein: the focal length of each lens group satisfies the following relation:

0.62<|f1/f3|<0.75，0.46<|f2/f3|<0.54，1.1<|f4/f3|<0.9；

wherein f1 is the focal length of the front fixed lens group, f2 is the focal length of the variable magnification lens group, f3 is the focal length of the compensation lens group, and f4 is the focal length of the rear fixed lens group.

4. The afocal magnification-varying optical system according to claim 1, wherein: the distance between the front fixed lens group and the system entrance pupil satisfies the following relation:

0.3<|L1/L|<0.4；

the distance between the rear fixed lens group and the system exit pupil satisfies the following relationship:

0.15<|L5/L|<0.22；

wherein L is the total length of the afocal variable magnification optical system, L1 is the distance between the front fixed lens group and the system entrance pupil, and L5 is the distance between the rear fixed lens group and the system exit pupil.

5. The afocal magnification-varying optical system according to claim 1, wherein: the front fixed lens group comprises a first lens, a second lens and a third lens which are sequentially arranged from an object space to an image space; the first lens is a positive focal power biconvex lens, the second lens is a positive focal power biconvex lens, and the third lens is a negative focal power biconcave lens.

6. The afocal magnification-varying optical system according to claim 1, wherein: the zoom lens group comprises a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object space to an image space; the fourth lens is a positive focal power meniscus lens, the fifth lens is a biconcave lens with negative focal power, the sixth lens is a meniscus lens with positive focal power, and the fifth lens and the sixth lens are glued.

7. The afocal magnification-varying optical system according to claim 1, wherein: the compensating lens group comprises a seventh lens and an eighth lens which are sequentially arranged from an object space to an image space; the seventh lens is a meniscus lens with negative focal power, and the eighth lens is a biconvex lens with positive focal power.

8. The afocal magnification-varying optical system according to claim 1, wherein: the rear fixed lens group comprises a ninth lens and a tenth lens which are sequentially arranged from the object space to the image space; the ninth lens is a meniscus lens with negative focal power, and the tenth lens is a biconvex lens with positive focal power.

9. The afocal magnification-varying optical system according to any one of claims 5-8, wherein: each lens is a spherical lens.

10. The afocal magnification-varying optical system according to any one of claims 5-8, wherein: the material of each lens has a near ultraviolet transmittance of not less than 70%.

11. The afocal magnification-varying optical system according to claim 1, wherein: the working wavelength range of the afocal zoom optical system is 365nm-487nm.

12. The afocal magnification-varying optical system according to claim 1, wherein: the zoom ratio of the afocal zoom optical system satisfies the following conditions: 1.75< M <2.5, wherein M is the magnification ratio of the afocal magnification-varying optical system.

13. The afocal magnification-varying optical system according to claim 1, wherein: the afocal magnification-varying optical system further comprises a diaphragm disposed at the system entrance pupil for limiting a diameter of the system entrance pupil.

14. The afocal zoom optical system according to claim 1 or 13, wherein: the diameter of the system entrance pupil satisfies 6.35mm < D1<7.35mm, wherein D1 is the diameter of the system entrance pupil.

15. A microscope imaging system, the microscope imaging system comprising at least:

objective lens, tube lens and afocal magnification-varying optical system according to any one of claims 1-14;

the objective lens is arranged at the object side of the afocal zoom optical system, and the pupil surface of the objective lens is overlapped with the entrance pupil of the afocal zoom optical system;

the tube mirror is arranged on the image side of the afocal zoom optical system, and the entrance pupil of the tube mirror coincides with the exit pupil of the afocal zoom optical system.

16. The microscope imaging system according to claim 15, wherein: the focal length of the tube mirror is a fixed value.