Optical system of the tube lens of a confocal microscope

Abstract

The present disclosure describes an optical system for a tube lens of a confocal microscope. The tube lens includes, in order from the object side to the light source side along the optical axis of the confocal microscope, a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with positive optical power. The present disclosure combines aberration design theory, the principle of reasonable optical power distribution, and tolerance design concepts to modify parameters and optimize the design of the optical system of the tube lens. Through a reasonable optical structure setting, the illumination light path and detection imaging light path of the confocal microscope can share the tube lens. The parallel light path between the objective lens and the tube lens can be extended with other optical path components. By adopting an aberration-correcting design, the microscope system ensures clear imaging within the visible light range, with uniform and symmetrical clarity on both sides of the image. At the same time, the arrangement and external structure of each lens are optimized, making the optical system of the tube lens simple to assemble and have good tolerance performance.

Description

Technical Field

[0001] The present disclosure generally relates to an intelligent manufacturing equipment industry, and more particularly to an optical system of a tube lens of a confocal microscope. Background Art

[0002] With the continuous development of microscopy in recent years, confocal microscopy has become a key technology in the field of optical microscopy. Its high-precision, high-resolution, non-contact, and unique axial tomographic imaging features allow for easy three-dimensional image reconstruction, and it has been widely used in fields such as micro- and nano-detection, precision measurement, and life science research. However, traditional confocal microscopes suffer from slow imaging speeds and a small field of view. The emergence of parallel scanning confocal microscopy has significantly increased the measurement speed of single-point confocal measurements.

[0003] In a confocal microscope, the optical system can be generally divided into an illumination path and a detection and imaging path, depending on its function. The illumination path transmits light from a light source through the optical system of the confocal microscope onto the surface of the object being measured; the detection and imaging path focuses the light beam reflected from the object being measured at the focal plane of the objective lens onto the detector through the focusing and imaging optical system.

[0004] In a parallel scanning confocal microscope, in order to improve optical performance, the illumination light path and the detection imaging light path need to share a pinhole scanning system to improve optical performance. At this time, the tube lens needs to be set in the light path between the objective lens and the spectrometer, that is, the illumination light path and the detection imaging light path will pass through the tube lens. At this time, the existing tube lens cannot meet the requirements of the detection imaging light path and the illumination light path at the same time, that is, it cannot meet the optical path requirements of the parallel scanning confocal microscope. Summary of the Invention

[0005] The present disclosure is made in view of the above-mentioned state of the prior art, and its purpose is to provide an optical system of a tube lens of a confocal microscope, which can realize the dual optical path requirement of the illumination optical path and the detection imaging optical path sharing the tube lens in a parallel scanning confocal microscope system.

[0006] To this end, the present disclosure provides an optical system of a tube lens of a confocal microscope, wherein the confocal microscope includes an objective lens, the tube lens, and a turntable in order from the object side to the light source side along the optical axis of the confocal microscope, and is characterized in that: the tube lens includes a first lens group with positive focal power, a second lens group with negative focal power, and a third lens group with positive focal power in order from the object side to the light source side along the optical axis of the confocal microscope; the interval between the first lens group and the rear focal plane of the objective lens on the optical axis is set to a first distance; the second lens group and the third lens group are spaced apart on the optical axis. The distance between the light source and the turntable on the optical axis is set as a second distance; the minimum distance between the light source and the turntable on the optical axis is set as a third distance; the absolute value of the ratio of the first distance to the focal length of the tube lens is within a first preset range; the third distance, the focal length of the third lens group, and the second distance satisfy the following condition: -L3*F3 / (F3-L3)>L2, where L3 represents the third distance, F3 represents the focal length of the third lens group, and L2 represents the second distance; and the absolute value of the ratio of the focal length of the first lens group to the focal length of the tube lens is within a second preset range. In this case, the present disclosure provides an appropriate position for the tube lens in the confocal microscope system, ensuring that the overall longitudinal height of the microscope is within a reasonable range while allowing space for extended optical elements between the tube lens and the objective lens. Simultaneously, the illumination light path is focused by the tube lens onto the rear focal plane of the objective lens, so that after passing through the objective lens, the illumination light path is uniformly illuminated on the surface of the object being measured in the form of parallel light. Furthermore, by rationally allocating the focal power of each lens group, aberration correction requirements are met and imaging quality is guaranteed. Therefore, the illumination light path and the detection imaging light path of the confocal microscope can share the tube lens, thereby realizing the dual light path requirement of the illumination light path and the detection imaging light path sharing the tube lens.

[0007] Additionally, in the optical system of the tube lens according to this embodiment, the first lens group optionally includes at least one first lens. In this case, the at least one first lens can be used in combination to form a specific optical focal length, which not only reduces the optical focal length of each first lens in the first lens group but also ensures that the optical focal length formed by the combination of the first lenses meets design requirements.

[0008] In addition, in the optical system of the tube lens involved in this embodiment, optionally, the second lens group includes a doublet lens, the doublet lens includes a second lens with positive optical power and a third lens with negative optical power, and the side of the doublet lens facing the objective lens is convex. In this case, since the doublet lens is an achromatic lens formed by bonding a low-refractive-index positive-power lens and a high-refractive-index negative-power lens, during the design, the wavelength values ​​of the scattered different light rays 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. Therefore, the second lens group can be used in the entire visible light region with small chromatic aberration and spherical aberration.

[0009] Additionally, in the optical system of the tube lens of this embodiment, optionally, the focal length of the second lens in the second lens group is greater than or equal to 40 mm and less than or equal to 100 mm; and the focal length of the third lens in the second lens group is greater than or equal to negative 50 mm and less than or equal to negative 20 mm. In this case, since the second lens group comprises a positive-power lens and a negative-power lens, forming a "positive-negative" structure, the second lens group has negative power, meeting the initial structural requirements of the optical system of the tube lens of this embodiment and facilitating system chromatic aberration correction.

[0010] Furthermore, in the optical system of the tube lens according to this embodiment, optionally, the refractive index of the material of the second lens is greater than or equal to 1.5 and less than or equal to 1.6, and the Abbe coefficient of the second lens is greater than or equal to 60 and less than or equal to 70; the refractive index of the material of the third lens is greater than or equal to 1.6 and less than or equal to 1.7, and the Abbe coefficient of the third lens is greater than or equal to 30 and less than or equal to 50. In this case, there is a certain difference between the material refractive index and Abbe coefficient of the second lens and the third lens, thereby facilitating system chromatic aberration correction.

[0011] In addition, in the optical system of the tube lens involved in this embodiment, optionally, the first preset range is greater than 0.5 and less than 1.0. In this case, when the absolute value of the ratio of the first distance to the focal length of the tube lens is greater than or equal to the upper limit of the first preset range, the overall structure of the microscope will become longer, affecting the vertical height of the entire system; when the absolute value of the ratio of the first distance to the focal length of the tube lens is less than or equal to the lower limit of the first preset range, the distance between the tube lens and the objective lens is too short, making it inconvenient to insert other extended optical elements, and the role and function of the tube lens are limited. Therefore, this embodiment stipulates the appropriate position of the tube lens in the confocal microscope system, while ensuring that the tube lens and the objective lens have space for extended optical elements, taking into account the overall vertical height of the microscope.

[0012] Additionally, in the optical system of the tube lens of this embodiment, the third lens group optionally includes a fourth lens located away from the light source and a fifth lens located closer to the light source. In this case, the fourth and fifth lenses can be combined to form a specific optical power, enabling the lenses in the third lens group to have a reasonable optical power, thereby facilitating system aberration correction.

[0013] Additionally, in the optical system of the tube lens according to this embodiment, optionally, a ratio of the focal length of the fourth lens to the focal length of the fifth lens is within a third preset range, wherein the third preset range is greater than or equal to 1 and less than or equal to 2. In this case, the fourth lens and the fifth lens in the third lens group each have a reasonable optical power, thereby avoiding uneven distribution of optical power between the fourth lens and the fifth lens in the third lens group, which could increase system aberrations.

[0014] In addition, in the optical system of the tube lens according to this embodiment, optionally, the second preset range is greater than 0.5 and less than 1. Thus, the first lens group has a reasonable optical power in the optical system of the tube lens.

[0015] In addition, in the optical system of the tube lens involved in this embodiment, the optical system of the tube lens is optionally configured to focus light emitted by a light source on the rear-image focal plane of the objective lens, and to receive parallel light emitted by the objective lens. In this case, the tube lens can focus light on the rear-image focal plane of the objective lens in the illumination optical path to achieve uniform illumination of the object surface, and can also receive parallel light emitted by the infinite conjugate image objective lens in the detection imaging optical path and focus the parallel light onto the pinhole of the rotating disk.

[0016] According to the present disclosure, an optical system of a tube lens of a confocal microscope can be provided, which can realize the dual light path requirement of the illumination light path and the detection imaging light path sharing the tube lens in a parallel scanning confocal microscope system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram showing an illumination light path of a tube lens according to this embodiment example.

[0018] Figure 2 Schematic diagram showing the detection imaging optical path of the tube lens involved in this embodiment example.

[0019] Figure 3 Schematic diagram showing the first distance, the second distance, and the third distance involved in this embodiment example.

[0020] Figure 4Schematic diagram showing the arrangement of lens groups in the tube lens involved in this embodiment example.

[0021] Figure 5 1 is a spot diagram showing the optical system of the tube lens according to Example 1.

[0022] Figure 6 1 is a diagram showing the modulation function of the optical system of the tube lens according to Example 1.

[0023] Figure 7 Schematic diagram showing the illumination light path of the tube lens according to Example 2.

[0024] Figure 8 Schematic diagram showing the detection imaging optical path of the tube lens involved in Example 2.

[0025] Figure 9 Schematic diagram showing the first distance, the second distance and the third distance involved in Example 2.

[0026] Figure 10 Schematic diagram showing the arrangement of lens groups in the tube lens involved in Example 2.

[0027] Figure 11 1 is a spot diagram showing the optical system of the tube lens according to Example 2.

[0028] Figure 12 3 is a diagram showing the modulation function of the optical system of the tube lens according to the second embodiment. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", "third" and "fourth" in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices. In the following description, the same symbols are given to the same components, and repeated descriptions are omitted. In addition, the drawings are only schematic diagrams, and the ratio of the sizes of the components to each other or the shapes of the components may be different from the actual ones.

[0031] The embodiments of the present disclosure provide an optical system of a tube lens of a confocal microscope, which can realize the dual optical path requirement of the illumination optical path and the detection imaging optical path sharing the tube lens in a parallel scanning confocal microscope system.

[0032] The present invention first selects an initial structure of a tube lens for a confocal microscope based on the required optical properties of the tube lens. The initial structure is a three-piece imaging (Cook three-piece imaging) system, in which a positive power lens group is disposed on either side of a negative power lens group. In combination with aberration design theory, the principle of reasonable power distribution, and tolerance design concepts, the selected initial structure is parameter-modified and optimized, thereby obtaining an optical system for the tube lens of a confocal microscope.

[0033] Optical power can be equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam. Optical power can be used to characterize the ability of an optical system to deflect light. Optical power can be the ratio of the image-side refractive index to the image focal length or the ratio of the object-side refractive index to the object focal length.

[0034] In a parallel scanning confocal microscope system, a tube lens can be used in conjunction with an objective lens. Through a reasonable optical structure setting, the illumination optical path and the detection imaging optical path can share the tube lens, which can meet the dual optical path requirements of the illumination optical path and the detection imaging optical path sharing the tube lens. In the illumination optical path, the tube lens can focus light on the rear focal plane of the objective lens to achieve uniform illumination of the object surface. In the detection imaging optical path, the tube lens receives the parallel light emitted by the objective lens. The parallel light path between the objective lens and the tube lens can be extended with other optical path components, such as filters, beam splitters, polarizers, etc., and can ensure the quality of microscopic imaging, making the configuration of the microscope more flexible while effectively controlling the size of the microscope. Changing the distance between the objective lens and the tube lens will not affect the overall optical system of the microscope, nor will it change the magnification, and will not affect the optical system. At the same time, according to different design requirements, an optical system with suitable magnification and working distance can be constructed by replacing objective lenses with different focal lengths. Due to the characteristics of parallel confocal microscopy, this disclosure addresses the aberrations introduced by the rotating disk within the microscope by optimizing the parameters of each lens in the tube lens. This design employs an aberration-correcting design to ensure clear imaging within the visible light range, with uniform and symmetrical clarity on both sides of the image. This disclosure also optimizes the arrangement and external structure of each lens, resulting in a tube lens optical system with a reasonable distribution of optical power and a reasonable tolerance range, enabling easy assembly and excellent tolerance performance.

[0035] In some examples, the parallel confocal microscope referred to in the present disclosure may also be referred to as a confocal microscope or a microscope.

[0036] Hereinafter, the optical system of the tube lens according to this embodiment will be described in detail with reference to the accompanying drawings.

[0037] Figure 1 Schematic diagram showing the illumination light path of the tube lens 2 according to the present embodiment. Figure 2 1 is a schematic diagram showing the detection imaging optical path of the tube lens 2 according to the embodiment of the present invention. Figure 3 Schematic diagram showing a first distance L1, a second distance L2 and a third distance L3 involved in this embodiment example, Figure 4 FIG. 1 is a schematic diagram showing the arrangement of lens groups in the tube lens 2 according to the embodiment.

[0038] This disclosure selects an initial structure for a confocal microscope tube lens 2 based on the desired optical properties of the tube lens 2. Incorporating aberration design theory, principles for rational optical power distribution, and tolerance design concepts, the selected initial structure is parameter-modified and optimized, thereby resulting in an optical system for the tube lens of a confocal microscope. The following first introduces the components of each lens group in the tube lens 2, followed by the conditions that must be met by the structural parameters of each lens group in the tube lens 2. Finally, specific data from two examples are provided to illustrate the imaging effects of the tube lens optical system.

[0039] In some examples, a confocal microscope may include, in order from the object side to the light source side, an objective lens 1, a tube lens 2, a rotating disk 3, and a beam splitter 4. Tube lens 2 may include, in order from the object side to the light source side, a first lens group TG1 with positive optical power, a second lens group TG2 with negative optical power, and a third lens group TG3 with positive optical power. In this case, the initial structure is a three-piece imaging system (Cook three-piece imaging), with a positive optical power lens group placed on either side of the negative optical power lens group. This structure provides sufficient degrees of freedom to correct system aberrations.

[0040] In some examples, the initial structure of the optical design can also be determined by the PW method.

[0041] In some examples, the objective lens 1 can be an infinite conjugate microscope objective lens. In this case, the light scattered from the sample to be measured is a parallel beam after passing through the objective lens 1, and is focused and imaged on the S10 surface of the turntable 3 by the tube lens 2. This design will not affect the overall optical system of the microscope, nor will it change the magnification, and will not affect the optical system even if the interval between the objective lens 1 and the tube lens 2 is changed. At the same time, according to different design requirements, an optical system with a suitable magnification and working distance can be constructed by replacing objective lenses 1 with different focal lengths. In addition, it is convenient to extend other optical path components between the objective lens 1 and the tube lens 2, such as filters, dichroic prisms, polarizers, etc., and can ensure the quality of microscopic imaging, thereby making the configuration of the microscope more flexible and effectively controlling the volume of the microscope. In some examples, other optical path components that can be extended include any one or more combinations of filters, dichroic prisms, and polarizers.

[0042] In some examples, the first lens group TG1 may include at least one first lens 210. In some examples, the first lens group TG1 may include a plurality of first lenses 210. In some examples, the plurality of first lenses 210 may include a plurality of first lenses 210 with positive power and a plurality of first lenses 210 with negative power.

[0043] In some examples, first lens 210 may be a biconvex lens, a plano-convex lens, or a meniscus lens.

[0044] In some examples, when the first lens 210 may be a plano-convex lens or a meniscus lens, the convex surface S1 thereof may be close to the objective lens 1 side.

[0045] In some examples, preferably, the first lens 210 can be a positive-power plano-convex single lens 210 , with its convex surface S1 close to the objective lens 1 . In this case, the plano-convex shape design facilitates assembly of the tube lens 2 .

[0046] In some examples, the second lens group TG2 may include a third lens 221 with negative optical power. In this case, the third lens 221 with negative optical power can be used to form a three-piece imaging system in conjunction with the first lens group TG1 and the third lens group TG3.

[0047] In some examples, the second lens group TG2 may include a second lens 220 with positive power and a third lens 221 with negative power. In some examples, the second lens group TG2 may include a doublet lens including the second lens 220 with positive power and the third lens 221 with negative power.

[0048] In some examples, the surface S3 of the doublet lens facing the objective lens 1 can be a convex surface.

[0049] In some examples, the second lens 220 can be a positive-power biconvex single lens, and the third lens 221 can be a biconcave lens. In this case, the doublet is an achromatic lens formed by bonding a low-refractive-index positive-power lens to a high-refractive-index negative-power lens. During the design, the different wavelength values ​​and lens shape are optimized for the three wavelengths of blue, green, and red, so that the focal length remains almost unchanged throughout the visible spectrum, achieving the smallest possible chromatic aberration. In addition to chromatic aberration, spherical aberration is also well corrected. As a result, the second lens group can be used in the entire visible light region with minimal chromatic aberration and spherical aberration.

[0050] In some examples, the focal length of the second lens 220 in the second lens group TG2 can be greater than or equal to 40 mm and less than or equal to 100 mm; and the focal length of the third lens 221 in the second lens group TG2 can be greater than or equal to negative 50 mm and less than or equal to negative 20 mm. In this case, the second lens group TG2 is composed of one positive and one negative lens, forming a "positive-negative" structure. Thus, the second lens group TG2 can have negative power, meeting the initial structural requirements of the optical system of the tube lens 2 involved in this embodiment and facilitating system chromatic aberration correction.

[0051] It should be noted that the focal length of the second lens 220 in the second lens group TG2 can also be slightly less than 40 mm or slightly greater than or equal to 100 mm. In this case, the focal length of the third lens 221 can be adaptively adjusted. In other words, the focal length of the second lens 220 can be matched with the focal length of the third lens 221 to enable the second lens group TG2 to form a specific optical focal length.

[0052] In some examples, the refractive index of the material of the second lens 220 can be greater than or equal to 1.5 and less than or equal to 1.6, and the Abbe coefficient of the second lens 220 can be greater than or equal to 60 and less than or equal to 70. The refractive index of the material of the third lens 221 can be greater than or equal to 1.6 and less than or equal to 1.7, and the Abbe coefficient of the third lens 221 can be greater than or equal to 30 and less than or equal to 50. In this case, there is a certain difference in the refractive index and Abbe coefficient of the material of the second lens 220 and the third lens 221, which is beneficial for correcting system chromatic aberration.

[0053] It should be noted that the refractive index of the material of the second lens 220 in the second lens group TG2 can also be slightly less than 1.5 or slightly greater than or equal to 1.6. In this case, the refractive index of the material of the third lens 221 can be adaptively adjusted. In other words, the refractive index of the material of the second lens 220 can be matched with the refractive index of the material of the third lens 221 to enable the second lens group to form a specific optical power.

[0054] It should be noted that the Abbe coefficient of the second lens 220 in the second lens group TG2 can also be slightly less than 60 or slightly greater than or equal to 70. In this case, the Abbe coefficient of the third lens 221 can be adaptively adjusted. In other words, the Abbe coefficient of the second lens 220 can be coordinated with the Abbe coefficient of the third lens 221 so that the second lens group TG2 has the function of correcting systematic chromatic aberration.

[0055] In some examples, the third lens group TG3 may include one lens with positive refractive power.

[0056] In some examples, the third lens group TG3 may also include multiple lenses. In this case, since the third lens group TG3 includes multiple lenses, the optical system of the tube lens 2 has multiple degrees of freedom, which is conducive to the reasonable distribution of optical focal length among the multiple lenses to facilitate system aberration correction.

[0057] In some examples, preferably, the third lens group TG3 may include a fourth lens 230 far from the light source and a fifth lens 231 close to the light source.

[0058] In some examples, the fourth lens 230 can be a plano-convex lens, a biconvex lens, or a meniscus lens, etc., which can meet the preset optical power design requirements.

[0059] In some examples, the fifth lens 231 may also be a plano-convex lens, a bi-convex lens, or a concave-convex lens, etc., which meet the preset optical power design requirements.

[0060] In some examples, spacer rings may be used to fix the lenses in the first lens group TG1 .

[0061] In some examples, spacer rings may be used to fix the lenses in the second lens group TG2.

[0062] In some examples, a spacer ring may be provided between the fourth lens 230 and the fifth lens 231. In this case, it is advantageous to use the spacer ring to fix the fourth lens 230 and the fifth lens 231.

[0063] In some examples, an expansion optical element may be disposed between the first lens group TG1 and the rear focal plane of the objective lens 1. In some examples, the expansion optical element may include any one of a filter, a beam splitter, and a polarizer, or a combination thereof. This allows for the expansion of the functionality of the parallel confocal microscopy system without affecting the optical system, while effectively controlling the size of the parallel confocal microscope.

[0064] In order to meet the requirements of the optical system design of the tube lens 2, the structural parameters of each lens group and each component lens of the tube lens 2 need to meet the preset requirements. In order to facilitate the description of the structural parameters of the tube lens 2 and the conditional relationship between the parameters, the present disclosure defines a first distance L1, a second distance L2 and a third distance L3. Figure 3 and Figure 4 The distance between the first lens group TG1 and the rear focal plane of the objective lens 1 on the optical axis is set to a first distance L1, see Figure 3 , that is, the first distance L1 refers to the distance from the vertex of the surface S1 of the first lens 210 to the rear focal plane of the objective lens 1. The interval between the second lens group TG2 and the third lens group TG3 on the optical axis is set to the second distance L2, that is, the second distance L2 refers to the distance between the two adjacent lens surface vertices between the second lens group TG2 and the third lens group TG3, that is, Figure 3 The distance between the vertex of the surface S4 of the third lens 220 and the vertex of the surface S5 of the fourth lens 230 shown in FIG. 1; the minimum distance between the light source position 12 and the turntable 3 on the optical axis is set to a third distance L3, and the light source position position is Figure 3 The position of position 12 in the image, along the optical axis, the distance from the position 12 to the S10 surface of the turntable 3 is the third distance L3.

[0065] In some examples, position 12 may also be the location of the focused imaging of the light source.

[0066] In this embodiment, the focal length of the first lens group TG1 is represented by F1, the focal length of the second lens group TG2 is represented by F2, the focal length of the third lens group TG3 is represented by F3, and the focal length of the tube lens 2 is represented by F.

[0067] In some examples, as described above, the absolute value L1 / F of the ratio of the first distance L1 to the focal length F of the tube lens 2 is within a first preset range.

[0068] In some examples, the first preset range may be greater than 0.5.

[0069] In some examples, the lower limit of the first preset range may be related to an extension component that needs to be disposed between the tube lens 2 and the objective lens 1. For example, if the space occupied by the extension component is larger, the lower limit of the first preset range may be higher.

[0070] In some examples, the first preset range may be less than 1.0.

[0071] In some examples, the upper limit of the first preset range may be related to the length of the tube lens 2 of the parallel confocal microscope. For example, the longer the length of the tube lens 2 is, the higher the upper limit of the first preset range may be.

[0072] In some examples, the first preset range may be greater than 0.4 and less than 0.9. Preferably, the first preset range may be greater than 0.5 and less than 1.0. Thus, the present disclosure can ensure that the tube lens 2 has an appropriate position in the confocal microscope system, while ensuring that the tube lens 2 and the objective lens 1 have an extended optical element space, while also taking into account the overall vertical height of the microscope.

[0073] In some examples, the third distance L3, the focal length F3 of the third lens group, and the second distance L2 need to satisfy the following condition: -L3*F3 / (F3-L3)>L2. In this case, if the relationship between the third distance L3, the focal length F3 of the third lens group, and the second distance L2 does not satisfy the above condition, the light of the illumination light path converges inside the tube lens 2, and the light of the illumination light path cannot be focused on the rear focal plane of the objective lens 1 through the tube lens 2, so that after the illumination light path passes through the objective lens 1, it cannot be uniformly irradiated on the surface of the object to be measured in the form of parallel light. Therefore, the present disclosure can make the light of the illumination light path focus on the rear focal plane of the objective lens 1 through the tube lens 2, so that after the illumination light path passes through the objective lens 1, it is uniformly irradiated on the surface of the object to be measured in the form of parallel light.

[0074] In some examples, an absolute value F1 / F of a ratio of the focal length F1 of the first lens group TG1 to the focal length F of the tube lens 2 is within a second preset range.

[0075] In some examples, the second preset range may be greater than 0.5.

[0076] In some examples, the second preset range may be less than 1.0.

[0077] In some examples, the upper and lower limits of the second preset range may be related to the optical power of the first lens group TG1. For example, when the optical power of the first lens group TG1 is too large, system aberrations may be exacerbated, and image quality may be degraded. In this case, the lower limit of the second preset range may need to be adjusted higher. In some examples, when the optical power of the first lens group TG1 is too small, the optical power distribution of other lens groups in the tube lens 2 may be affected, leading to complexity in the optical power distribution design of the entire tube lens 2. In this case, the upper limit of the second preset range may need to be adjusted lower.

[0078] In some examples, the second preset range may be greater than 0.75 and less than 0.98. Preferably, the second preset range may be greater than 0.5 and less than 1.0. Thus, in the optical system of the tube lens 2, by reasonably allocating the optical power of each lens group, the aberration correction requirements of the tube lens 2 are met and the imaging quality is guaranteed. In addition, the tube lens 2 has a reasonable tolerance, which facilitates assembly and improves the tolerance performance of the tube lens 2.

[0079] In some examples, a ratio F30 / F31 of the focal length F30 of the fourth lens 230 to the focal length F31 of the fifth lens 231 is within a third preset range.

[0080] In some examples, the third preset range may be greater than or equal to 1. In some examples, the third preset range may be less than or equal to 2.

[0081] In some examples, preferably, the third preset range is greater than or equal to 1 and less than or equal to 2. In this case, the fourth lens 230 and the fifth lens 231 in the third lens group TG3 each have a reasonable optical power, thereby avoiding uneven distribution of optical power between the fourth lens 230 and the fifth lens 231, which may increase system aberrations.

[0082] In this embodiment, the illumination light of the light source is incident on the S10 surface of the flat glass turntable 3 after passing through the beam splitter 4. After passing through the flat glass turntable 3, the illumination light is sequentially passed through the fifth lens 231, the fourth lens 230, the third lens 221, the second lens 220, and the first lens 210, and is finally focused on the rear focal plane of the infinite conjugate microscope objective lens 1. The illumination light is uniformly irradiated on the surface of the sample to be measured in the form of nearly parallel light, and the surface where the sample to be measured is the object focal plane of the infinite conjugate microscope objective lens 1; after being reflected by the sample surface, the illumination light enters the infinite conjugate microscope objective lens 1 again. The reflected light on the object focal plane of the infinite conjugate microscope objective lens 1 is emitted as parallel light after passing through the infinite conjugate microscope objective lens 1. The parallel light is incident on the tube lens 2, passes through the first lens 210, the second lens 220, the third lens 221, the fourth lens 230, the fifth lens 231, and the flat glass turntable 3 in sequence, and is focused and imaged on the S10 surface of the flat glass turntable 3.

[0083] In Example 1, on the optical axis, the distance between the light source position 12 and the S10 surface of the turntable 3 is 89.566 mm, that is, the third distance L3 is 89.566 mm.

[0084] In Example 1, the turntable 3 may be a flat glass with a thickness of 2 mm, the angle between the central axis of the turntable 3 and the optical axis of the tube lens 2 may be 10°, and the distance from the center of the turntable 3 to the optical axis may be 15 mm.

[0085] In Example 1, the focal length of the tube lens 2 may be 120 mm, the entrance pupil diameter of the tube lens 2 may be 20 mm, and the tube lens 2 may be matched with an infinite conjugate microscope objective lens 1 with a magnification of 10X to 100X.

[0086] In Example 1, the distance between the vertex of the lens surface S1 of the first lens 210 of the tube lens 2 closest to the object side and the rear focal plane of the infinite conjugate microscope objective 1, that is, the first distance L1, can be 90.435 mm.

[0087] In embodiment 1, the second distance L2 may be 96.48 mm.

[0088] The surface number, surface type, curvature radius, thickness (interface spacing), refractive index at a wavelength of 0.588 μm, Abbe coefficient, and lens number of each lens in Example 1 are shown in Table 1. The unit of curvature radius, thickness (interface spacing), and other lengths is generally "mm."

[0089] Table 1 Lens parameters of Example 1

[0090]

[0091]

[0092] Table 2 Condition values ​​of Example 1

[0093]

[0094] The descriptions of the first distance L1, the second distance L2, the third distance L3, the first preset range, the second preset range, the third preset range, the first lens group TG1, the second lens group TG2, the third lens group TG3, the fourth lens 230, and the fifth lens 231 can be found above.

[0095] The focal length of the first lens group TG1 is represented by F1, the focal length of the second lens group TG2 is represented by F2, the focal length of the third lens group TG3 is represented by F3, the focal length of the fourth lens 230 is represented by F30, the focal length of the fifth lens 231 is represented by F31, and the focal length of the tube lens 2 is represented by F.

[0096] As shown in Table 2, in the above-mentioned embodiment 1, the optical system of the tube lens 2 meets the optical system design conditions of the tube lens 2 disclosed in the present invention.

[0097] Figure 5 1 is a point diagram showing the optical system of the tube lens 2 according to Example 1. Figure 5 The light spot is concentrated within the range of the Airy disk, and the energy concentration is very high. The imaging result of the optical system of the tube lens 2 of this embodiment 1 is relatively ideal.

[0098] Figure 6 1 is a diagram showing the modulation function of the optical system of the tube lens 2 according to Example 1. Figure 6 The optical system of tube lens 2 has good resolution and contrast in the low frequency band, and the imaging quality is very good. However, as the spatial frequency increases, its attenuation process is very slow, indicating that the image quality of tube lens 2 meets the requirements. Figure 6 The MTF1 curve is a diffraction limit graph, which shows the best contrast that the optical system of tube lens 2 can achieve under the condition of no aberration. Figure 6 It can be seen that the MTF curve is close to the diffraction limit and the optical transmission efficiency is very high, which shows that the optimization result of the optical system of the tube lens 2 of Example 1 is relatively ideal.

[0099] Figure 7 is a schematic diagram showing the illumination light path of the tube lens 2 involved in Example 2, Figure 8 Schematic diagram showing the detection imaging optical path of the tube lens 2 involved in Example 2, Figure 9 is a schematic diagram showing the first distance L1, the second distance L2 and the third distance L3 involved in Example 2, Figure 10 Schematic diagram showing the arrangement of lens groups in the tube lens 2 involved in Example 2.

[0100] In the second embodiment, on the optical axis, the distance between the light source position 12 and the S10 surface of the turntable 3 is 89.566 mm, that is, the third distance L3 is 89.566 mm.

[0101] In Example 2, the turntable 3 may be a flat glass with a thickness of 2 mm, the angle between the central axis of the turntable 3 and the optical axis of the tube lens 2 may be 10°, and the distance from the center of the turntable 3 to the optical axis may be 15 mm.

[0102] In Example 2, the focal length of the tube lens 2 may be 120 mm, the entrance pupil diameter of the tube lens 2 may be 20 mm, and the tube lens 2 may be matched with an infinite conjugate microscope objective lens 1 with a magnification of 10X to 100X.

[0103] In Example 2, the distance between the vertex of the lens surface S1 of the first lens 210 of the tube lens 2 closest to the object side and the rear focal plane of the infinite conjugate microscope objective lens 1, that is, the first distance L1, is 90.435 mm.

[0104] In Example 2, the second distance L2 is 91.85 mm.

[0105] Table 3 shows the surface number, surface type, curvature radius, thickness (interface spacing), refractive index at a wavelength of 0.588 μm, Abbe coefficient, and lens number of each lens in Example 2. The unit of curvature radius, thickness (interface spacing), and other lengths is generally "mm."

[0106] Table 3 Lens parameters of Example 2

[0107]

[0108] Table 4 Conditional values ​​of Example 2

[0109]

[0110] The descriptions of the first distance L1, the second distance L2, the third distance L3, the first preset range, the second preset range, the third preset range, the first lens group TG1, the second lens group TG2, the third lens group TG3, the fourth lens 230, and the fifth lens 231 can be found above.

[0111] The focal length of the first lens group TG1 is represented by F1, the focal length of the second lens group TG2 is represented by F2, the focal length of the third lens group TG3 is represented by F3, the focal length of the fourth lens 230 is represented by F30, the focal length of the fifth lens 231 is represented by F31, and the focal length of the tube lens 2 is represented by F.

[0112] As shown in Table 4, in the above-mentioned embodiment 2, the optical system of the tube lens 2 meets the optical system design conditions of the tube lens 2 disclosed in the present invention.

[0113] Figure 11 1 is a point diagram showing the optical system of the tube lens 2 according to Example 2. Figure 11 The light spot is concentrated within the range of the Airy disk, and the energy concentration is very high. The imaging result of the optical system of the tube lens 2 of this embodiment 2 is relatively ideal.

[0114] Figure 12 1 is a diagram showing the modulation function of the optical system of the tube lens 2 according to Example 2. Figure 12 The optical system of tube lens 2 has good resolution and contrast in the low frequency band, and the imaging quality is very good. However, as the spatial frequency increases, its attenuation process is very slow, indicating that the image quality of tube lens 2 meets the requirements. Figure 12 The MTF2 curve is a diffraction limit graph, which shows the best contrast that the optical system of tube lens 2 can achieve under the condition of no aberration. Figure 12It can be seen that the MTF curve is close to the diffraction limit and the optical transmission efficiency is very high, which shows that the optimization result of the optical system of the tube lens 2 of Example 2 is relatively ideal.

[0115] It should be noted that although Figures 1-4 , Figure 7-10 The first lens 210, the second lens 220, the third lens 221, the fourth lens 230, and the fifth lens 231 are shown as biconvex lenses, plano-convex lenses, or doublet lenses, but the present disclosure is not limited thereto. The first lens 210, the second lens 220, the third lens 221, the fourth lens 230, and the fifth lens 231 can be any lens type that meets the preset optical focal length design requirements. In other words, the first lens 210, the second lens 220, the third lens 221, the fourth lens 230, and the fifth lens 231 can be lens types that meet the design requirements of the optical system of the tube lens 2 of the present disclosure regarding optical focal length, focal length, material refractive index, and Abbe coefficient.

[0116] In summary, the present disclosure provides an optical system for a tube lens 2 of a confocal microscope. In the optical system for the tube lens 2 of the confocal microscope to which the present invention relates, the present disclosure first selects an initial structure of the tube lens of the confocal microscope based on the required optical characteristics of the tube lens 2. The initial structure is a three-piece imaging system, in which a positive optical power lens group is provided on each side of a negative optical power lens group. In combination with aberration design theory, a reasonable principle of optical power distribution, and a tolerance design concept, the selected initial structure is parameter-modified and optimized, thereby obtaining an optical system for the tube lens of the confocal microscope. In this optical system, the present disclosure provides an optical system for the tube lens. The tube lens 2 can be used in conjunction with the objective lens 1 in a parallel confocal microscope system. Through a reasonable optical structure setting, the illumination optical path and the detection imaging optical path of the parallel confocal microscope can share the tube lens. In the illumination optical path, the tube lens can focus the light on the rear focal plane of the objective lens 1 to achieve uniform illumination of the object surface. In the detection imaging optical path, the tube lens receives the parallel light emitted by the objective lens 1. The parallel light path between the objective lens 1 and the tube lens 2 can be extended to insert extension components, and the quality of microscopic imaging is guaranteed. Due to the characteristics of the parallel confocal microscope, the present invention optimizes the parameters of each lens of the tube lens for the aberration introduced by the turntable, adopts an aberration-eliminating design, and ensures that the microscope system has clear imaging in the visible light range and uniform and symmetrical clarity on both sides of the picture. At the same time, the arrangement and external structure of each lens are optimized, so that the optical system of the tube lens has the characteristics of reasonable tolerance range, simple assembly, and good tolerance performance.

[0117] Various embodiments of the present invention have been described above in the detailed description. Although this description directly describes the above-described embodiments, it should be understood that modifications and / or variations of the specific embodiments shown and described herein may occur to those skilled in the art. Any such modifications or variations that fall within the scope of this specification are intended to be included therein. Unless otherwise indicated, it is the inventor's intention that the words and phrases in the description and claims be given their ordinary and customary meanings as given to those skilled in the art.

[0118] The above description of various embodiments of the present invention known to the applicant at the time of filing this application has been presented and is intended for the purpose of illustration and description. This description is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teachings. The described embodiments serve to explain the principles of the invention and its practical application, and to enable others skilled in the art to utilize the invention in various embodiments and with various modifications suitable for the specific use contemplated. Therefore, it is intended that the invention is not limited to the specific embodiments disclosed for implementing the invention.

[0119] While particular embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that variations and modifications may be made based on the teachings of the present invention without departing from the invention and its broader aspects, and the appended claims are intended to cover within their scope all such changes and modifications that come within the true spirit and scope of the invention. It will be understood by those skilled in the art that, in general, the terms used in the present invention are generally intended to be "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "comprising" should be interpreted as "including but not limited to," etc.).

Claims

1. An optical system of a tube lens of a confocal microscope, comprising an objective lens, the tube lens, and a rotating disk in order from the object side to the light source side along the optical axis of the confocal microscope, characterized in that: The tube lens includes, from the object side to the light source side along the optical axis of the confocal microscope, a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with positive optical power; The distance between the first lens group and the rear focal plane of the objective lens on the optical axis is set to a first distance; the distance between the second lens group and the third lens group on the optical axis is set to a second distance; and the minimum distance between the position of the light source and the turntable on the optical axis is set to a third distance; An absolute value of a ratio of the first distance to the focal length of the tube lens is within a first preset range; The third distance, the focal length of the third lens group, and the second distance satisfy the following conditions: |-L3*F3 / (F3-L3)|>L2 Wherein L3 represents the third distance, F3 represents the focal length of the third lens group, and L2 represents the second distance; An absolute value of the ratio of the focal length of the first lens group to the focal length of the tube lens is within a second preset range, wherein the first preset range is greater than 0.5 and less than 1.0, and the second preset range is greater than 0.5 and less than 1.

2. The optical system of the tube lens according to claim 1, characterized in that: The first lens group includes at least one first lens.

3. The optical system of the tube lens according to claim 1, characterized in that: The second lens group includes a doublet lens, the doublet lens includes a second lens with positive optical power and a third lens with negative optical power, and the doublet lens has a convex surface facing the objective lens.

4. The optical system of the tube lens according to claim 3, characterized in that: The focal length of the second lens in the second lens group is greater than or equal to 40 mm and less than or equal to 100 mm; the focal length of the third lens in the second lens group is greater than or equal to negative 50 mm and less than or equal to negative 20 mm.

5. The optical system of the tube lens according to claim 3, characterized in that: The refractive index of the material of the second lens is greater than or equal to 1.5 and less than or equal to 1.6, and the Abbe coefficient of the second lens is greater than or equal to 60 and less than or equal to 70; the refractive index of the material of the third lens is greater than or equal to 1.6 and less than or equal to 1.7, and the Abbe coefficient of the third lens is greater than or equal to 30 and less than or equal to 50.

6. The optical system of the tube lens according to claim 1, wherein the third lens group includes a fourth lens far away from the light source and a fifth lens close to the light source.

7. The optical system of the tube lens according to claim 6, characterized in that: A ratio of the focal length of the fourth lens to the focal length of the fifth lens is within a third preset range, and the third preset range is greater than or equal to 1 and less than or equal to 2.

8. The optical system of the tube lens according to claim 1, characterized in that: The optical system of the tube lens is configured to focus the light emitted by the light source on the rear focal plane of the objective lens, and is configured to receive the parallel light emitted by the objective lens.

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