Microscope tube lens and measuring equipment

Abstract

The invention provides a microscope tube lens and a measuring device. Wherein the microscope tube lens is sequentially provided with a first lens group with positive focal length, a second lens group with positive focal length and a third lens group with negative focal length from an object plane to an image plane along the optical axis direction. The first lens group is sequentially provided with a first lens with a positive focal length and a second lens with a negative focal length, the second lens group is provided with a third lens with a positive focal length, and the third lens group is sequentially provided with a fourth lens with a positive focal length and a fifth lens with a negative focal length. The focal length fc1 of the first lens group, the focal length fc2 of the second lens group, the focal length fc3 of the third lens group and the focal length f of the microscope tube lens meet the condition that fc1 / f is more than or equal to 0.69 and less than or equal to 0.75; 0.305 < = fc2 / f < = 0.34; 0.21 < = fc3 / f < = 0.23. According to the invention, the focal length of each lens group is reasonably distributed, and parameter modification and optimization design are carried out on the light path structure of the microscope tube lens, so that the large-view-field aberration elimination requirement is met, and the good flat field performance is maintained, thereby ensuring the imaging quality.

Description

Technical Field

[0001] The invention relates to the technical field of optical imaging, and in particular to a microscope tube lens and a measuring device. Background Art

[0002] Microscopic observation is an indispensable technology in the research process of life sciences. In fields such as tissue sectioning and pathological diagnosis, it is often necessary to detect a sample over a large range. A common practice is to use a high-NA, small-field-of-view imaging objective to image the sample multiple times, and then use related technologies to stitch the images of each sub-field of view to achieve high-resolution ultra-large-field-of-view image acquisition. The technology of stitching imaging is very mature and the system is relatively simple, but because the acquisition of each sub-field of view is discrete in time and space, more acquisition time is required, and more of this time is used for sample movement and objective lens focusing. This previous scanning method often requires a long sampling time.

[0003] Conventional optical microscopes are difficult to balance the size of the field of view and the resolution, which greatly limits microscopic imaging in large-field biological imaging applications. In order to improve the sampling time of a wide range of samples, objectives with a large field of view and high resolution have become the future development trend. In order to improve functionality and flexibility, modern microscopy technology often uses tube lenses in conjunction with infinity imaging objectives to form an infinitely long spatial distance for adding various functional accessories. The tube lens is placed behind the objective lens to converge the light beam. The traditional tube lens has a simple structure, a small corresponding field of view, and is lacking in aberration correction. When using a high-end objective lens with apochromatism and a large numerical aperture, if the residual aberration of the tube lens is too large, the resolution and analysis ability of the objective lens will not be reflected.

[0004] Chinese patent CN107831590A discloses a wide spectrum tube lens optical path structure for an infinity correction microscope, the spectrum correction range of the optical path structure is 435nm-685nm, and the optical path structure is composed of 6 lenses, which is different from the number of lenses used in this solution.

[0005] Chinese patent CN118818717A discloses a tube lens with a full field of view of 22.2 mm, an F number of 8.5, and a focal length of 124 mm. However, the lens has a large number of lenses and uses a high refractive index material with a refractive index of 1.92, which will affect the short-wave transmittance of the microscope system. Summary of the invention

[0006] The present invention provides a microscope tube lens and a measuring device, which at least solve one of the above technical problems.

[0007] To achieve the above object, the present invention proposes the following technical solutions: A microscope tube lens, which is provided with a first lens group with a positive focal length, a second lens group with a positive focal length, and a third lens group with a negative focal length in sequence from an object plane to an image plane along an optical axis direction; The first lens group sequentially includes a first lens having a positive focal length and a second lens having a negative focal length, the second lens group sequentially includes a third lens having a positive focal length, and the third lens group sequentially includes a fourth lens having a positive focal length and a fifth lens having a negative focal length; The focal length fc1 of the first lens group, the focal length fc2 of the second lens group, the focal length fc3 of the third lens group and the focal length f of the microscope tube lens satisfy the following conditions: 0.69≤fc1 / f≤0.75; 0.305≤fc2 / f≤0.34; 0.21≤|fc3 / f|≤0.23.

[0008] Furthermore, the Abbe number of the first lens is less than 50, and the refractive index is 1.6±0.05; the Abbe number of the second lens is greater than 50, and the refractive index is 1.6±0.05; the Abbe number of the third lens is greater than 50, and the refractive index is 1.6±0.05.

[0009] Furthermore, an aperture stop is provided at 70-110 mm on the side of the first lens group facing the object plane.

[0010] Furthermore, the Abbe number of the fourth lens is less than 50, and the refractive index is 1.7±0.05; the Abbe number of the fifth lens is greater than 50, and the refractive index is 1.7±0.05.

[0011] Furthermore, the Abbe number of the fourth lens is less than 50, and the refractive index is 1.8±0.05; the Abbe number of the fifth lens is greater than 50, and the refractive index is 1.8±0.05.

[0012] Furthermore, a side of the first lens group facing the object plane is a convex surface.

[0013] Furthermore, the third lens group is meniscus-shaped.

[0014] Furthermore, the third lens is a meniscus lens.

[0015] Furthermore, the operating wavelength of the microscope tube lens is 436-656nm.

[0016] On the other hand, the present invention also provides a measuring device, comprising: The objective lens is used to converge the illumination light onto the surface of the object to be measured, receive the illumination light reflected by the surface of the object to be measured and emit parallel light; The microscope tube lens as described above is used to receive and focus the illumination light emitted by the objective lens so that it forms an actual image on the sensor.

[0017] The beneficial effects of the present invention are as follows: The present application proposes a microscope tube lens, which has a focal length of 200 mm and an operating band of 436-656 nm. By reasonably allocating the focal lengths of each lens group, the optical path structure of the microscope tube lens is parameter-modified and optimized to meet the requirements of large field of view and aberration elimination, and maintain good flatness to ensure imaging quality.

[0018] In addition, the microscope tube lens proposed in the present application has only five lenses and does not use high-refractive-index lenses in order to resolve the influence of high-refractive-index materials on the short-wave transmittance of the microscope tube lens.

[0019] The microscope tube lens proposed in the embodiment of the present application provides a position range of the aperture diaphragm while ensuring the imaging quality. In actual use, the position of the aperture diaphragm can be flexibly adjusted according to the size of the object to be measured, so as to facilitate actual operation. At the same time, the total length of the microscope tube lens proposed in the present application is 23.5 mm, which is convenient for installation and carrying.

[0020] In the present invention, each lens is a spherical lens, which is easy to process and reduces the production cost of the microscope tube lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the microscope tube lens of the present invention; Figure 2 is a field curvature / distortion diagram of Example 1 of the present invention; Figure 3 is an axial chromatic aberration diagram of Example 1 of the present invention; Figure 4 is a modulation transfer function curve diagram of embodiment 1 of the present invention; Figure 5 yes Figure 4 A partial enlarged view of Figure 6 is a field curvature / distortion diagram of embodiment 2 of the present invention; Figure 7 is an axial chromatic aberration diagram of Example 2 of the present invention; Figure 8 is a modulation transfer function curve diagram of embodiment 2 of the present invention; Fig. 9 yes Figure 8 A partial enlarged view of Among them, 1 is the first lens group; 101 is the first lens; 102 is the second lens; 2 is the third lens; 3 is the third lens group; 301 is the fourth lens; 302 is the fifth lens. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions 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 only part of the embodiments of the present invention, not all of the embodiments.

[0023] like Figure 1 As shown, an embodiment of the present application proposes a microscope tube lens, which is infinitely conjugate, and an aperture stop is provided at 70-110 mm on the side of the first lens group 1 facing the object plane, that is, the entrance pupil and the aperture stop are at the same position.

[0024] The microscope tube lens proposed in the embodiment of the present application proposes a position range of the aperture diaphragm while ensuring the imaging quality. In actual use, the position of the aperture diaphragm can be flexibly adjusted according to the size of the object to be measured to facilitate actual operation.

[0025] Hereinafter, the microscope tube lens involved in this embodiment will be described in detail with reference to the accompanying drawings. Example 1

[0026] The microscope tube lens is provided with a first lens group 1 with a positive focal length, a second lens group with a positive focal length, and a third lens group 3 with a negative focal length in sequence from the object plane to the image plane along the optical axis direction.

[0027] The focal length fc1 of the first lens group, the focal length fc2 of the second lens group, the focal length fc3 of the second lens group and the focal length f of the microscope tube lens satisfy the following conditions: 0.69≤fc1 / f≤0.72; 0.305≤fc2 / f≤0.34; 0.21≤|fc3 / f|≤0.23.

[0028] The focal length is equal to the difference between the image-side beam convergence and the object-side beam convergence, and is used to characterize the ability of an optical system to deflect light.

[0029] According to the above relationship, when the focal length of the first lens group 1 is too large, the aberration of the microscope tube will be aggravated and the imaging quality will be reduced; when the focal length of the first lens group 1 is too small, it will affect the focal length distribution of other lens groups in the microscope tube, which will lead to the complexity of the focal length distribution design of the entire microscope tube.

[0030] Therefore, in the microscope tube, the focal length of each lens group is reasonably allocated to meet the aberration elimination requirements of the microscope tube and ensure the imaging quality. In addition, the microscope tube has a reasonable tolerance, which is convenient for assembly and improves the tolerance performance of the microscope tube.

[0031] Along the optical axis from the object plane to the image plane, the first lens group 1 is sequentially provided with a first lens 101 with a positive focal length and a second lens 102 with a negative focal length, the second lens group is provided with a third lens 2 with a positive focal length, and the third lens group 3 is sequentially provided with a fourth lens 301 with a positive focal length and a fifth lens 302 with a negative focal length.

[0032] The side of the first lens group 1 facing the object plane is convex; the third lens 2 is a meniscus lens; and the third lens group 3 is a meniscus lens.

[0033] In the first lens group 1 , the first lens 101 is a meniscus lens, and the second lens 102 is a plano-convex lens; in the third lens group 3 , the fourth lens 301 is a plano-convex lens, and the fifth lens 302 is a meniscus lens.

[0034] The first lens group 1 is composed of a first lens 101 and a second lens 102. The first lens group 1 is an achromatic lens composed of a low refractive index positive focal length lens (first lens) and a high refractive index negative focal length lens (second lens) cemented together.

[0035] In the design of the first lens group 1, the wavelength values ​​of the dispersed light and the lens shape are optimized for the three wavelengths of blue, green and red, so that the focal length remains almost unchanged in the entire visible spectrum, achieving the smallest possible chromatic aberration. In addition to chromatic aberration, spherical aberration is also well corrected. As a result, the first lens group not only compresses the inclination angle and aperture of the incident light beam, but also has smaller chromatic aberration and spherical aberration when used in the entire visible light region.

[0036] In addition, in the present application, the third lens 2 is used to compress the inclination angle and aperture of the incident light beam, and works together with the first lens group 1 to correct the field curvature.

[0037] The third lens group 3 is an achromatic lens composed of a low refractive index positive focal length lens (fourth lens) and a high refractive index negative focal length lens (fifth lens). At the same time, it works together with the first lens group 1 and the third lens 2 to compress the aperture of the incident light beam and achieve field curvature correction.

[0038] The Abbe number of the first lens 101 is less than 50, and the refractive index is 1.6±0.05; the Abbe number of the second lens 102 is greater than 50, and the refractive index is 1.6±0.05.

[0039] The refractive index and Abbe number of the first lens 101 and the second lens 102 have a certain difference, which is beneficial to the correction of system chromatic aberration. In addition, the refractive index of the first lens 101 provided in the present application can be matched with the refractive index of the second lens 102, and can be adjusted within a limited range according to actual needs, so that the first lens group 1 forms a specific focal length.

[0040] Similarly, the Abbe number of the first lens 101 provided in the present application can be matched with the Abbe number of the second lens 102 and adjusted within a limited range according to actual needs, so that the first lens group 1 has a system chromatic aberration correction function.

[0041] The Abbe number of the third lens 2 is greater than 50, and the refractive index is 1.6±0.05.

[0042] The Abbe number of the fourth lens 301 is less than 50, and the refractive index is 1.7±0.05; the Abbe number of the fifth lens 302 is greater than 50, and the refractive index is 1.7±0.05.

[0043] The refractive index and Abbe number of the fourth lens 301 and the fifth lens 302 have a certain difference, which is beneficial to the system chromatic aberration correction. In addition, the refractive index of the fourth lens 301 provided in the present application can be matched with the refractive index of the fifth lens 302, and can be adjusted within a limited range according to actual needs, so that the third lens group 3 forms a specific focal length.

[0044] Similarly, the Abbe number of the fourth lens 301 provided in the present application can be matched with the Abbe number of the fifth lens 302 and adjusted within a limited range according to actual needs, so that the third lens group 3 has a system chromatic aberration correction function.

[0045] In this embodiment, relevant parameters of each lens are shown in Table 1.

[0046] Table 1 Lens parameters

[0047] The lens parameters in Table 1 can achieve a field of view of 40 mm on the image side and clear imaging of light in the 436-656 nm band.

[0048] From the above lens parameters, it can be seen that the focal length of the microscope tube is 200 mm, the focal length of the first lens group 1 is 144 mm, the focal length of the third lens 2 is 68 mm, and the focal length of the third lens group 3 is -46 mm.

[0049] That is, fc1=144mm, fc2=68mm, fc3=-46mm, f=200mm; fc1 / f=144 / 200=0.72, satisfying 0.69≤fc1 / f≤0.72; fc2 / f=68 / 200=0.34, which satisfies 0.305≤fc2 / f≤0.34; fc3 / f=-46 / 200=-0.23, satisfying 0.21≤|fc3 / f|≤0.23.

[0050] Figure 2 The field curvature / distortion diagram of the microscope tube lens of this embodiment is shown. Figure 2 The horizontal axis of the left figure in the figure is the field curvature (mm), and the vertical axis is the normalized object height, which represents the field curvature value of the microscope tube lens of this embodiment; the black curve in the figure represents the meridian direction, and the red curve represents the sagittal direction. Figure 2 The horizontal axis of the right figure in is the distortion percentage, and the vertical axis is the normalized field of view, indicating the degree of distortion of the microscope tube in this embodiment.

[0051] Depend on Figure 2 It can be seen that the maximum value of the meridian field curvature of the microscope tube lens of this embodiment is 0.1029mm, the maximum value of the sagittal field curvature is 0.0544mm, and the field curvature is well corrected; the distortion of the microscope tube lens of this embodiment is less than 0.39%, indicating that the microscope tube lens of this embodiment has good imaging quality.

[0052] Figure 3 The axial chromatic aberration diagram of the microscope tube lens of this embodiment is shown, the horizontal axis is spherical aberration (mm), and the vertical axis is normalized aperture. Figure 3 It can be seen that the axial chromatic aberration curve of 436nm and the axial chromatic aberration curve of 656nm both overlap at the aperture of 0.3, indicating that the wavelengths of 436nm and 656nm achieve achromatism at the aperture of 0.3.

[0053] Figure 4 The modulation transfer function (MTF) curve of the microscope tube lens of this embodiment is shown, which represents the system imaging contrast of different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the modulation degree. The solid line in the figure represents the meridian direction, and the dotted line represents the sagittal direction. Figure 5 for Figure 4 A partial enlarged view of .

[0054] The diffraction limit curve in the meridional direction completely coincides with the diffraction limit curve in the sagittal direction. The 0F curve in the meridional direction completely coincides with the 0F curve in the sagittal direction.

[0055] from Figure 4 and Figure 5 It can be seen that the trends of the MTF values ​​corresponding to multiple spatial frequencies in this embodiment are consistent with the trend of the diffraction limit curve (Diffraction limit), and the MTF values ​​corresponding to multiple spatial frequencies overlap with the diffraction limit curve, indicating that the microscope tube lens of this embodiment has good imaging quality. Example 2

[0056] Based on the microscope tube lens described in Example 1, the microscope tube lens proposed in this example realizes a field of view of 30 mm on the image side and can clearly image light in the 436-656 nm band.

[0057] The difference is that, in this embodiment, the Abbe number of the fourth lens is less than 50, and the refractive index is 1.8±0.05; the Abbe number of the fifth lens is greater than 50, and the refractive index is 1.8±0.05.

[0058] In this embodiment, relevant parameters of each lens are shown in Table 2.

[0059] Table 2 Lens parameters

[0060] From the above lens parameters, it can be seen that the focal length of the microscope tube is 200 mm, the focal length of the first lens group 1 is 138 mm, the focal length of the third lens 2 is 61 mm, and the focal length of the third lens group 3 is -42 mm.

[0061] That is, fc1=138mm, fc2=61mm, fc3=-42mm, f=200mm; fc1 / f=138 / 200=0.69, satisfying 0.69≤fc1 / f≤0.72; fc2 / f=61 / 200=0.305, which satisfies 0.305≤fc2 / f≤0.34; fc3 / f=-42 / 200=-0.21, satisfying 0.21≤|fc3 / f|≤0.23.

[0062] Figure 6 The field curvature / distortion diagram of the microscope tube lens of this embodiment is shown. Figure 6 The horizontal axis of the left figure in the figure is the field curvature (mm), and the vertical axis is the normalized field of view, which represents the field curvature value of the microscope tube lens of this embodiment; the red curve in the figure represents the sagittal direction, and the black curve represents the meridian direction. Figure 6 The horizontal axis of the right figure in is the distortion percentage, and the vertical axis is the normalized field of view, indicating the degree of distortion of the microscope tube in this embodiment.

[0063] Depend on Figure 6 It can be seen that the maximum value of the meridian field curvature of the microscope tube lens of this embodiment is 0.0601mm, the maximum value of the sagittal field curvature is 0.0401mm, and the field curvature is well corrected; the distortion of the microscope tube lens of this embodiment is less than 0.37%, indicating that the microscope tube lens of this embodiment has good imaging quality.

[0064] Figure 7 The axial chromatic aberration diagram of the microscope tube lens of this embodiment is shown, the horizontal axis is spherical aberration (mm), and the vertical axis is normalized aperture. Figure 7 It can be seen that the axial chromatic aberration curve of 436nm and the axial chromatic aberration curve of 656nm both overlap at an aperture of 0.707, indicating that the wavelengths of 436nm and 656nm achieve achromatism at an aperture of 0.707.

[0065] Figure 8 The modulation transfer function (MTF) curve of the microscope tube lens of this embodiment is shown, which represents the system imaging contrast of different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. The dotted line in the figure represents the sagittal direction, and the solid line represents the meridian direction. Fig. 9 for Figure 8 A partial enlarged view of .

[0066] The diffraction limit curve in the meridional direction completely coincides with the diffraction limit curve in the sagittal direction. The 0F curve in the meridional direction completely coincides with the 0F curve in the sagittal direction.

[0067] from Figure 8 and Fig. 9 It can be seen that the trends of the MTF values ​​corresponding to multiple spatial frequencies in this embodiment are consistent with the trend of the diffraction limit curve, and the MTF values ​​corresponding to multiple spatial frequencies overlap with the diffraction limit curve, indicating that the microscope tube lens of this embodiment has good imaging quality.

[0068] On the other hand, the present invention also provides a measuring device, comprising: The objective lens is used to converge the illumination light onto the surface of the object to be measured, receive the illumination light reflected by the surface of the object to be measured and emit parallel light; The microscope tube lens is used to receive and focus the illumination light emitted by the objective lens so that it forms an actual image on the sensor.

[0069] Preferably, an expansion optical element may be arranged between the first lens group and the rear focal plane of the objective lens.

[0070] In some examples, the extended optical element may include any one of a filter, a beam splitter, and a polarizer, or a combination of multiple thereof. Thus, other functions of the measuring device can be added by combining other extended optical elements without affecting the normal imaging of the microscope tube.

[0071] Working principle of the measuring device: The light source emits an illumination light, which is incident on the objective lens through the beam splitter. The objective lens converges the incident light onto the surface of the object to be measured. The illumination light reflected by the surface of the object to be measured enters the objective lens again. The objective lens emits parallel light, which is incident on the microscope tube lens and passes through the first lens group 1, the third lens 2, and the third lens group 3 in sequence, so that the parallel light is imaged on the sensor.

[0072] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A microscope tube lens, characterized in that: A first lens group with a positive focal length, a second lens group with a positive focal length, and a third lens group with a negative focal length are sequentially arranged along the optical axis from the object plane to the image plane; The first lens group sequentially includes a first lens having a positive focal length and a second lens having a negative focal length, the second lens group sequentially includes a third lens having a positive focal length, and the third lens group sequentially includes a fourth lens having a positive focal length and a fifth lens having a negative focal length; The focal length fc1 of the first lens group, the focal length fc2 of the second lens group, the focal length fc3 of the third lens group and the focal length f of the microscope tube lens satisfy the following conditions: 0.69≤fc1 / f≤0.75; 0.305≤fc2 / f≤0.34; 0.21≤|fc3 / f|≤0.

23.

2. The microscope tube lens according to claim 1, characterized in that: The Abbe number of the first lens is less than 50, and the refractive index is 1.6±0.05; the Abbe number of the second lens is greater than 50, and the refractive index is 1.6±0.05; the Abbe number of the third lens is greater than 50, and the refractive index is 1.6±0.

05.

3. The microscope tube lens according to claim 1, characterized in that: An aperture stop is arranged at 70-110 mm on the side of the first lens group facing the object plane.

4. The microscope tube lens according to claim 1, characterized in that: The Abbe number of the fourth lens is less than 50, and the refractive index is 1.7±0.05; the Abbe number of the fifth lens is greater than 50, and the refractive index is 1.7±0.

05.

5. The microscope tube lens according to claim 1, characterized in that: The Abbe number of the fourth lens is less than 50, and the refractive index is 1.8±0.05; the Abbe number of the fifth lens is greater than 50, and the refractive index is 1.8±0.

05.

6. The microscope tube lens according to claim 1, characterized in that: The side of the first lens group facing the object plane is a convex surface.

7. The microscope tube lens according to claim 1, characterized in that: The third lens group is meniscus shaped.

8. The microscope tube lens according to claim 1, characterized in that: The third lens is a meniscus lens.

9. The microscope tube lens according to claim 1, characterized in that: The working wavelength of the microscope tube lens is 436-656nm.

10. A measuring device, characterized in that: include: The objective lens is used to converge the illumination light onto the surface of the object to be measured, receive the illumination light reflected by the surface of the object to be measured and emit parallel light; The microscope tube lens as described in any one of claims 1 to 9 is used to receive and focus the illumination light emitted by the objective lens so that it forms an actual image on the sensor.

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