Optical system of a confocal microscope

Abstract

This disclosure describes an optical system for a confocal microscope. The tube, along the optical axis of the confocal microscope from the object side to the light source side, sequentially includes 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. This disclosure combines aberration design theory, the principle of reasonable optical power allocation, and tolerance design concepts to modify and optimize the parameters of the tube's optical system. Through a reasonable optical structure setting, the illumination and detection imaging optical paths of the confocal microscope can share the tube. The parallel light path between the objective lens and the tube can be expanded to include other optical path components. By employing aberration-correcting design, it ensures clear imaging of the microscope system in the visible light range, with uniform and symmetrical sharpness on both sides of the image. Simultaneously, the arrangement and shape of each lens are optimized, giving the tube's optical system the characteristics of simple assembly and good tolerance performance.

Description

[0001] This application is a divisional application of the patent application filed on August 26, 2022, with application number 2022110300204, entitled "Optical System of Tube Lens for Confocal Microscope". Technical Field

[0002] This disclosure generally relates to an intelligent manufacturing equipment industry, and more specifically to an optical system for a confocal microscope. Background Technology

[0003] With the continuous development of microscopy technology in recent years, confocal microscopy has become one of the important technologies in the field of optical microscopy. It features high precision, high resolution, non-contact imaging, and unique axial tomographic scanning imaging characteristics, easily achieving three-dimensional image reconstruction. It has been widely used in micro-nano detection, precision measurement, and life science research. However, traditional confocal microscopes have drawbacks such as slow imaging speed and small field of view. The emergence of parallel scanning confocal microscopy has improved the measurement speed of traditional single-point confocal measurements.

[0004] In confocal microscopy, the optical system can generally be divided into illumination and detection / imaging paths, depending on its function. The illumination path directs light emitted from the light source through the confocal microscope's optical system onto the surface of the object being measured. The detection / imaging path uses a focusing imaging optical system to focus the light beam reflected from the sample at the focal plane of the objective lens onto the detector.

[0005] In parallel scanning confocal microscopy, in order to improve optical performance, the illumination optical path and the detection imaging optical path need to share a pinhole scanning system. In this case, the tube needs to be placed in the optical path between the objective lens and the beam splitter. That is, both the illumination optical path and the detection imaging optical path will pass through the tube. At this time, the existing tube cannot simultaneously meet the needs of the detection imaging optical path and the illumination optical path, that is, it cannot meet the optical path requirements of parallel scanning confocal microscopy. Summary of the Invention

[0006] This disclosure was made in view of the above-mentioned state of the prior art, and its purpose is to provide an optical system for a confocal microscope tube that can meet the dual-optical-path requirement of sharing the illumination optical path and the detection imaging optical path in a parallel scanning confocal microscope system.

[0007] Therefore, this disclosure provides an optical system for a confocal microscope's tube end, wherein the confocal microscope, along its optical axis from the object side to the light source side, sequentially includes an objective lens, the tube end, and a rotating disk. The tube end, along the optical axis from the object side to the light source side, sequentially includes 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 image back focal planes of the first lens group and the objective lens on the optical axis is defined as a first distance; the distance between the second lens group and the third lens group on the optical axis is defined as a second distance; the minimum distance between the light source position and the rotating disk on the optical axis is defined as a third distance; the absolute value of the ratio of the first distance to the focal length of the tube end is within a first preset range; and the third distance, the focal length of the third lens group, and the second distance satisfy the following condition: Where L3 represents the third distance, F3 represents the focal length of the third lens group, and L2 represents the second distance; the absolute value of the ratio of the focal length of the first lens group to the focal length of the tube mirror is within a second preset range. In this case, the present disclosure provides an appropriate position of the tube mirror 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 mirror and the objective lens. Simultaneously, it ensures that the light from the illumination path is focused by the tube mirror onto the back focal plane of the objective lens, so that the illumination path, after passing through the objective lens, uniformly illuminates the surface of the object being measured in parallel light. Furthermore, by rationally distributing the optical power of each lens group, aberration correction requirements are met and imaging quality is guaranteed. Thus, the illumination path and detection imaging path of the confocal microscope can share the tube mirror, fulfilling the dual-path requirement of sharing the tube mirror for both illumination and detection imaging paths.

[0008] Furthermore, in the optical system of the tube lens according to this embodiment, the first lens group may optionally include at least one first lens. In this case, a specific optical power can be formed by using at least one first lens, which not only reduces the optical power borne by each first lens in the first lens group, but also ensures that the optical power formed by the combination of the first lenses meets the design requirements.

[0009] Furthermore, in the optical system of the tube lens according to this embodiment, optionally, the second lens group includes a cemented doublet lens, which comprises a second lens with positive optical power and a third lens with negative optical power, and the side of the cemented doublet lens facing the objective lens is convex. In this case, since the cemented 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 dispersed light rays and the lens shape are optimized for the three wavelengths of blue, green, and red, so that the focal length remains almost constant throughout the 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.

[0010] Furthermore, in the optical system of the tube lens according to this embodiment, optionally, the focal length of the second lens in the second lens group is greater than or equal to 40mm and less than or equal to 100mm; the focal length of the third lens in the second lens group is greater than or equal to -50mm and less than or equal to -20mm. In this case, since the second lens group consists of a positive-power lens and a negative-power lens forming a "positive-negative" structure, the second lens group has negative power, which meets the initial structural requirements of the optical system of the tube lens according to this embodiment and helps with system chromatic aberration correction.

[0011] Furthermore, in the optical system of the tube lens involved in this embodiment, optionally, the refractive index 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 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, the refractive index and Abbe coefficient of the second lens and the third lens have a certain difference, which is beneficial for the system's chromatic aberration correction.

[0012] Furthermore, 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 longitudinal 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 function of the tube lens is limited. Therefore, this embodiment specifies an appropriate position of the tube lens in the confocal microscope system, which satisfies the requirement that the tube lens and the objective lens have space for extended optical elements while taking into account the overall longitudinal height of the microscope.

[0013] Furthermore, in the optical system of the tube lens according to this embodiment, optionally, the third lens group includes a fourth lens located away from the light source and a fifth lens located close to the light source. In this case, the fourth and fifth lenses can be used together to form a specific optical power, enabling the lenses in the third lens group to bear a reasonable optical power, which in turn facilitates system aberration correction.

[0014] Furthermore, in the optical system of the tube lens according to this embodiment, optionally, the 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 bear 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 would increase system aberrations.

[0015] Furthermore, in the optical system of the tube mirror according to this embodiment, optionally, the second preset range is greater than 0.5 and less than 1. Thus, the first lens group provides a reasonable optical power in the optical system of the tube mirror.

[0016] Additionally, in the optical system of the tube lens according to this embodiment, optionally, the optical system of the tube lens is configured to focus light emitted from the light source onto the back focal plane of the objective lens, and is configured to receive parallel light emitted from the objective lens. In this case, the tube lens can focus light onto the back focal plane of the objective lens in the illumination optical path to achieve uniform illumination of the object surface, and the tube lens can receive parallel light emitted from the infinity conjugate image objective lens in the detection imaging optical path and focus it onto the pinhole of the turntable.

[0017] According to this disclosure, an optical system for a confocal microscope can be provided, which, in a parallel scanning confocal microscope system, enables the dual-optical-path requirement of sharing the illumination optical path and the detection imaging optical path within the same microscope. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing the illumination optical path of the tube mirror involved in this embodiment example.

[0019] Figure 2 This is a schematic diagram of the detection imaging optical path of the tube endoscope involved in this embodiment example.

[0020] Figure 3 This is a schematic diagram illustrating the first distance, second distance, and third distance involved in this embodiment example.

[0021] Figure 4This is a schematic diagram showing the arrangement of lens groups in a tube endoscope according to an example of this embodiment.

[0022] Figure 5 This is a dot diagram showing the optical system of the tube mirror involved in Embodiment 1.

[0023] Figure 6 This is a modulation function diagram of the optical system of the tube mirror involved in Embodiment 1.

[0024] Figure 7 This is a schematic diagram showing the illumination optical path of the tube mirror involved in Embodiment 2.

[0025] Figure 8 This is a schematic diagram of the detection imaging optical path of the tube endoscope involved in Example 2.

[0026] Figure 9 This is a schematic diagram illustrating the first distance, second distance, and third distance involved in Embodiment 2.

[0027] Figure 10 This is a schematic diagram showing the arrangement of lens groups in the tube endoscope involved in Embodiment 2.

[0028] Figure 11 This is a dot diagram showing the optical system of the tube mirror involved in Embodiment 2.

[0029] Figure 12 This is a modulation function diagram of the optical system of the tube mirror involved in Embodiment 2. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that the terms "first," "second," "third," and "fourth," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. 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 not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices. In the following description, the same reference numerals are used for the same parts, and repeated descriptions are omitted. Additionally, the accompanying drawings are merely schematic diagrams, and the scale of the dimensions of the parts or the shape of the parts may differ from the actual figures.

[0032] The embodiments of this disclosure propose an optical system for a confocal microscope tube, which, in a parallel scanning confocal microscope system, enables the dual-optical-path requirement of sharing the tube for both the illumination optical path and the detection imaging optical path.

[0033] Based on the required optical characteristics of the tube, this invention first selects the initial structure of the tube of a confocal microscope. This initial structure is a three-element imaging (Cook three-element imaging) system, with a positive optical power lens group set on each side of the negative optical power lens group. Combining aberration design theory, the principle of reasonable optical power distribution, and the concept of tolerance design, the selected initial structure is modified and optimized to obtain an optical system for the tube of a confocal microscope.

[0034] Optical power can be equal to the difference between the image-side beam convergence and the object-side beam convergence. Optical power can be used to characterize the ability of an optical system to deflect light rays. Optical power can be the ratio of image-side refractive index to image focal length or the ratio of object-side refractive index to object focal length.

[0035] In parallel scanning confocal microscopy systems, the tube can be used in conjunction with the objective lens. Through a well-designed optical structure, the illumination and imaging optical paths can share the tube, fulfilling the dual-path requirement of using the same tube for both illumination and imaging. In the illumination path, the tube focuses light onto the rear focal plane of the objective, achieving uniform illumination of the object surface. In the imaging path, the tube receives the parallel light emitted from the objective. The parallel light path between the objective and the tube can be expanded with other optical components, such as filters, beam splitters, and polarizers, while ensuring high-quality microscopic imaging. This allows for more flexible microscope configuration and effective control over the microscope's size. Changing the spacing between the objective and the tube does not affect the overall optical system of the microscope, nor does it alter the magnification. Furthermore, depending on different design requirements, optical systems with suitable magnification and working distances can be constructed by replacing objectives with different focal lengths. Due to the characteristics of parallel confocal microscopes, this disclosure addresses the aberrations introduced by the rotating disk in parallel confocal microscopes by optimizing the parameters of each lens in the microscope tube and employing an aberration-correcting design to ensure clear imaging of the microscope system in the visible light range, with uniform and symmetrical sharpness on both sides of the image. This disclosure optimizes the arrangement and shape of each lens, giving the optical system of the microscope tube a reasonable power distribution and a reasonable tolerance range, thus providing the characteristics of convenient assembly and good tolerance performance.

[0036] In some examples, the parallel confocal microscopes involved in this disclosure may also be referred to as confocal microscopes or microscopes.

[0037] The optical system of the tube mirror according to this embodiment will be described in detail below with reference to the accompanying drawings.

[0038] Figure 1 This is a schematic diagram showing the illumination optical path of the endoscope 2 according to this embodiment example. Figure 2 This is a schematic diagram of the detection imaging optical path of the endoscope 2 involved in this embodiment example. Figure 3 This is a schematic diagram illustrating the first distance L1, the second distance L2, and the third distance L3 involved in this embodiment example. Figure 4 This is a schematic diagram showing the arrangement of the lens group in the tube mirror 2 involved in this embodiment example.

[0039] This disclosure describes the initial structure of a confocal microscope's tube mirror 2, selected based on the desired optical characteristics. Combining aberration design theory, the principle of reasonable optical power allocation, and tolerance design concepts, the selected initial structure is modified and optimized to obtain an optical system for the tube mirror of a confocal microscope. The following first introduces the components of each lens group in the tube mirror 2, followed by the conditions that the structural parameters of each lens group in the tube mirror 2 must meet. Finally, specific data from two embodiments are provided to illustrate the imaging effect of the tube mirror's optical system.

[0040] In some examples, a confocal microscope may sequentially include an objective lens 1, a tube lens 2, a rotating disk 3, and a beam splitter 4 along the optical axis from the object side to the light source side. The tube lens 2 may sequentially include 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 along the optical axis of the confocal microscope from the object side to the light source side. In this case, the initial structure is a three-element imaging (Cook's three-element imaging) system, with a positive optical power lens group positioned on each side of the negative optical power lens group. Therefore, this structure provides sufficient degrees of freedom to correct system aberrations.

[0041] In some examples, the initial structure of the optical design can also be determined using the PW method.

[0042] In some examples, objective 1 can be an infinity conjugate microscope objective. In this case, the light scattered from the sample passes through objective 1 as a parallel beam, which is then focused and imaged on the S10 surface of the rotating disk 3 by the tube lens 2. This design does not affect the overall optical system of the microscope, nor does it change the magnification, even if the distance between objective 1 and tube lens 2 is changed. Furthermore, depending on different design requirements, an optical system with suitable magnification and working distance can be constructed by replacing objective 1 with different focal lengths. It also facilitates the expansion of other optical path components between objective 1 and tube lens 2, such as filters, beam splitters, polarizers, etc., while ensuring the quality of the microscopic image. This makes the microscope configuration more flexible and effectively controls its size. In some examples, other optical path components can be expanded, including any one or more combinations of filters, beam splitters, and polarizers.

[0043] 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 optical power and a plurality of first lenses 210 with negative optical power.

[0044] In some examples, the first lens 210 may be a biconvex lens, a plano-convex lens, or a concave-convex lens.

[0045] In some examples, when the first lens 210 can be a plano-convex lens or a concave-convex lens, its convex surface S1 can be close to the objective lens 1.

[0046] 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 is beneficial for the assembly of the tube lens 2.

[0047] 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 in conjunction with the first lens group TG1 and the third lens group TG3 to form a three-element imaging system.

[0048] In some examples, the second lens group TG2 may include a second lens 220 of positive optical power and a third lens 221 of negative optical power. In some examples, the second lens group TG2 may include a cemented doublet lens, which may include a second lens 220 of positive optical power and a third lens 221 of negative optical power.

[0049] In some examples, the surface S3 of the cemented doublet lens facing the objective lens 1 can be a convex surface.

[0050] 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 cemented doublet is an achromatic lens formed by bonding a low-refractive-index positive-power lens and a high-refractive-index negative-power lens. During design, the different wavelength values ​​and lens shape are optimized for the three wavelengths of blue, green, and red, with the focal length remaining almost constant throughout the visible spectrum to achieve the smallest possible chromatic aberration. In addition to chromatic aberration, spherical aberration is also well corrected. Therefore, the second lens group can be used throughout the visible light region with minimal chromatic and spherical aberration.

[0051] 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; the focal length of the third lens 221 in the second lens group TG2 can be greater than or equal to -50 mm and less than or equal to -20 mm. In this case, the second lens group TG2 consists of a positive power lens and a negative power lens forming a "positive-negative" structure. Thus, the second lens group TG2 can have a negative power, which meets the initial structural requirements of the optical system of the tube lens 2 according to this embodiment and helps with the system's chromatic aberration correction.

[0052] 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 40mm or slightly greater than or equal to 100mm. In this case, the focal length of the third lens 221 can be adjusted accordingly. In other words, the focal length of the second lens 220 can be matched with the focal length of the third lens 221 so that the second lens group TG2 forms a specific optical power.

[0053] 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, the refractive index and Abbe coefficient of the materials of the second lens 220 and the third lens 221 have a certain difference, which is beneficial to the chromatic aberration correction of the system.

[0054] 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 adjusted accordingly. 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 so that the second lens group forms a specific optical power.

[0055] 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 adjusted adaptively. In other words, the Abbe coefficient of the second lens 220 can be matched with the Abbe coefficient of the third lens 221 so that the second lens group TG2 has the function of system chromatic aberration correction.

[0056] In some examples, the third lens group TG3 may include a lens with positive optical power.

[0057] 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 mirror 2 has multiple degrees of freedom. This facilitates the rational allocation of optical power among the multiple lenses to correct system aberrations.

[0058] In some examples, preferably, the third lens group TG3 may include a fourth lens 230 away from the light source and a fifth lens 231 closer to the light source.

[0059] In some examples, the fourth lens 230 can be a plano-convex lens, a biconvex lens, or a concave-convex lens, etc., that meets the preset optical power design requirements.

[0060] In some examples, the fifth lens 231 can also be a plano-convex lens, biconvex lens, or concave-convex lens, etc., which meet the preset optical power design requirements.

[0061] In some examples, spacer rings can be used to fix the lenses in the first lens group TG1.

[0062] In some examples, spacer rings can be used to fix the lenses in the second lens group TG2.

[0063] 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.

[0064] In some examples, an extended optical element may be disposed between the first lens group TG1 and the image back focal plane of objective lens 1. In some examples, the extended optical element may include any one or a combination of filters, beam splitters, polarizers, etc. Thus, the functionality of the parallel confocal microscope system can be extended without affecting the optical system, while effectively controlling the size of the parallel confocal microscope.

[0065] To meet the optical system design requirements of the telescope 2, the structural parameters of each lens group and each component lens of the telescope 2 need to meet preset requirements. To facilitate the explanation of the structural parameters of the telescope 2 and the conditional relationships between these parameters, this disclosure defines a first distance L1, a second distance L2, and a third distance L3. See [link to relevant documentation]. Figure 3 and Figure 4 The distance between the first lens group TG1 and the image back focal plane of objective lens 1 on the optical axis is defined as the first distance L1, see [reference]. Figure 3 In other words, the first distance L1 refers to the distance from the vertex of surface S1 of the first lens 210 to the back focal plane of the image of the objective lens 1. The interval between the second lens group TG2 and the third lens group TG3 on the optical axis is defined as the second distance L2, which means the distance between the vertices of two adjacent lens surfaces of the second lens group TG2 and the third lens group TG3. Figure 3 The distance between the vertex of surface S4 of the third lens 220 and the vertex of surface S5 of the fourth lens 230 is shown; the minimum distance between the light source position 12 and the turntable 3 on the optical axis is defined as the third distance L3, and this light source position is... Figure 3 The distance from position 12 along the optical axis to surface S10 of turntable 3 is the third distance L3.

[0066] In some examples, position 12 can also be the position where the light source is focused and imaged.

[0067] In this embodiment, the focal length of the first lens group TG1 is denoted by F1, the focal length of the second lens group TG2 is denoted by F2, and the focal length of the third lens group TG3 is denoted by F3. The focal length of the tube mirror 2 is denoted by F.

[0068] In some examples, as described above, the absolute value of the ratio of the first distance L1 to the focal length F of the lens 2 Within the first preset range.

[0069] In some examples, the first preset range can be greater than 0.5.

[0070] In some examples, the lower limit of the first preset range may be related to the extension component that needs to be positioned between the endoscope 2 and the objective lens 1. For example, the larger the space occupied by the extension component, the higher the lower limit of the first preset range can be.

[0071] In some examples, the first preset range may be less than 1.0.

[0072] In some examples, the upper limit of the first preset range can be related to the length of the tube 2 of the parallel confocal microscope; for example, the longer the tube 2 is, the higher the upper limit of the first preset range can be.

[0073] In some examples, the first preset range can be greater than 0.4 and less than 0.9; preferably, the first preset range can be greater than 0.5 and less than 1.0. Thus, this disclosure allows the microscope tube 2 to have an appropriate position in the confocal microscope system, satisfying the requirement that the microscope tube 2 and objective lens 1 have extended optical element space while also considering the overall longitudinal height dimension of the microscope.

[0074] In some examples, the following conditions need to be met between the third distance L3, the focal length F3 of the third lens group, and the second distance 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 meet the above conditions, the light rays of the illumination path converge inside the tube lens 2. The light rays of the illumination path cannot be focused on the back focal plane of the objective lens 1 through the tube lens 2. Therefore, after passing through the objective lens 1, the illumination path cannot uniformly illuminate the surface of the object being measured in the form of parallel light. Thus, this disclosure enables the light rays of the illumination path to be focused on the back focal plane of the objective lens 1 through the tube lens 2, so that after passing through the objective lens 1, the illumination path uniformly illuminates the surface of the object being measured in the form of parallel light.

[0075] In some examples, the absolute value of the ratio of the focal length F1 of the first lens group TG1 to the focal length F of the tube lens 2. Within the second preset range.

[0076] In some examples, the second preset range can be greater than 0.5.

[0077] In some examples, the second preset range may be less than 1.0.

[0078] In some examples, the upper and lower limits of the second preset range may be related to the optical power borne by the first lens group TG1. For example, when the optical power borne by the first lens group TG1 is too large, it will exacerbate system aberrations and reduce image quality. In this case, the lower limit of the second preset range needs to be increased. In some examples, when the optical power borne by the first lens group TG1 is too small, it will affect the optical power allocation of other lens groups in the tube mirror 2, leading to increased complexity in the optical power allocation design of the entire tube mirror 2 optical system. In this case, the upper limit of the second preset range needs to be decreased.

[0079] In some examples, the second preset range can be greater than 0.75 and less than 0.98; preferably, the second preset range can be greater than 0.5 and less than 1.0. Thus, in the optical system of the tube lens 2, by rationally 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. Furthermore, the tube lens 2 has reasonable tolerances, facilitating assembly and improving its tolerance performance.

[0080] In some examples, the ratio of the focal length F30 of the fourth lens 230 to the focal length F31 of the fifth lens 231 is... Within the third preset range.

[0081] In some examples, the third preset range can be greater than or equal to 1. In some examples, the third preset range can be less than or equal to 2.

[0082] 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 bear a reasonable optical power, thereby avoiding uneven distribution of optical power between the fourth lens 230 and the fifth lens 231, which would increase system aberrations.

[0083] In this embodiment, the illumination light from 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 then passes through the fifth lens 231, the fourth lens 230, the third lens 221, the second lens 220, and the first lens 210 in sequence, and finally focuses on the back focal plane of the infinity conjugate microscope objective 1. The illumination light is uniformly irradiated on the surface of the sample under test in the form of near-parallel light. The surface of the sample under test is the object-side focal plane of the infinity conjugate microscope objective 1. After being reflected by the sample surface, the illumination light enters the infinity conjugate microscope objective 1 again. The reflected light located on the object-side focal plane of the infinity conjugate microscope objective 1 is emitted as parallel light after passing through the infinity conjugate microscope objective 1. The parallel light enters the tube mirror 2 and 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 on the S10 surface of the flat glass turntable 3 to form an image. In Example 1, the distance between the light source position 12 and the S10 surface of the turntable 3 on the optical axis is 89.566 mm, that is, the third distance L3 is 89.566 mm.

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

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

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

[0087] In Example 1, the second distance L2 can be 96.48 mm.

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

[0089] Table 1 Lens parameters for Example 1

[0090] Table 2 Conditional Values ​​for Example 1

[0091] 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.

[0092] 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.

[0093] As shown in Table 2, in the above embodiment 1, the optical system of the tube lens 2 meets the optical system design conditions of the tube lens 2 disclosed in this invention.

[0094] Figure 5This is a dot diagram showing the optical system of the tube lens 2 involved in Embodiment 1. See also Figure 5 The light spot is concentrated within the Airy disk area, and the energy concentration is very high. The imaging results of the optical system of the tube lens 2 in this embodiment 1 are quite ideal.

[0095] Figure 6 This is a modulation function diagram of the optical system of the tube lens 2 involved in Embodiment 1. See also... Figure 6 The optical system of tube mirror 2 exhibits good resolution and contrast in the low-frequency range, resulting in excellent image quality. However, its image quality decays slowly with increasing spatial frequency, indicating that the image quality of tube mirror 2 meets the requirements. Figure 6 The MTF1 curve is the diffraction limit diagram, representing the best contrast achievable by the optical system of tube lens 2 under aberration-free conditions. Figure 6 It can be seen that the MTF curve is close to the diffraction limit, indicating that the optical transmission efficiency is very high, which shows that the optimization result of the optical system of the tube lens 2 in Example 1 is quite ideal.

[0096] Figure 7 This is a schematic diagram showing the illumination optical path of the tube lens 2 involved in Embodiment 2. Figure 8 This is a schematic diagram of the detection imaging optical path of the tube endoscope 2 involved in Example 2. Figure 9 This is a schematic diagram illustrating the first distance L1, the second distance L2, and the third distance L3 involved in Embodiment 2. Figure 10 This is a schematic diagram showing the arrangement of the lens group in the tube mirror 2 involved in Embodiment 2.

[0097] In Example 2, the distance between the light source position 12 and the S10 surface of the turntable 3 on the optical axis is 89.566 mm, that is, the third distance L3 is 89.566 mm.

[0098] In embodiment 2, the turntable 3 can be a flat glass plate with a thickness of 2mm, the angle between the central axis of the turntable 3 and the optical axis of the tube lens 2 can be 10°, and the distance from the center of the turntable 3 to the optical axis can be 15mm.

[0099] In Example 2, the focal length of the tube lens 2 can be 120mm. The entrance pupil diameter of the tube lens 2 can be 20mm; the tube lens 2 can be matched with an infinity conjugate microscope objective 1 with a magnification of 10X to 100X.

[0100] In Example 2, the distance L1 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 back focal plane of the conjugate microscope objective 1 at infinity is 90.435 mm.

[0101] In Example 2, the second distance L2 is 91.85 mm.

[0102] Table 3 shows the surface number, surface type, radius of curvature, thickness (surface spacing), refractive index at wavelength 0.588 μm, Abbe number, and lens number for each lens in Example 2. The units for radius of curvature, thickness (surface spacing), and other lengths are generally "mm".

[0103] Table 3 Lens parameters for Example 2

[0104] Table 4. Conditional values ​​for Example 2

[0105] 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.

[0106] 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.

[0107] As shown in Table 4, in the above embodiment 2, the optical system of the tube lens 2 meets the optical system design conditions of the tube lens 2 disclosed in this invention.

[0108] Figure 11 This is a dot diagram showing the optical system of the tube lens 2 involved in Embodiment 2. See also Figure 11 The light spot is concentrated within the Airy disk area, and the energy concentration is very high. The imaging results of the optical system of the tube lens 2 in this embodiment 2 are quite ideal.

[0109] Figure 12 This is a modulation function diagram of the optical system of the tube lens 2 involved in Embodiment 2. See also... Figure 12 The optical system of tube mirror 2 exhibits good resolution and contrast in the low-frequency range, resulting in excellent image quality. However, its image quality decays slowly with increasing spatial frequency, indicating that the image quality of tube mirror 2 meets the requirements. Figure 12 The MTF2 curve is a diffraction-limited diagram, representing the best contrast achievable by the optical system of tube lens 2 under aberration-free conditions. Figure 12 It can be seen that the MTF curve is close to the diffraction limit, indicating that the optical transmission efficiency is very high, which shows that the optimization result of the optical system of the tube lens 2 in Example 2 is quite ideal.

[0110] It should be noted that, although Figures 1-4 , Figures 7-10The first lens 210, the second lens 220, the third lens 221, the fourth lens 230, and the fifth lens 231 are manifested as biconvex lenses, plano-convex lenses, or cemented doublet lenses, but this disclosure is not limited to these. 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 power 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 this disclosure regarding optical power, focal length, material refractive index, and Abbe coefficient.

[0111] In summary, this disclosure provides an optical system for the confocal microscope's tube end 2. In this optical system, based on the required optical characteristics of the tube end 2, the present invention first selects an initial structure for the confocal microscope's tube end, which is a three-element imaging system. A positive optical power lens group is set on each side of the negative optical power lens group. Combining aberration design theory, the principle of reasonable optical power allocation, and tolerance design concepts, the selected initial structure is modified and optimized, thereby obtaining an optical system for the confocal microscope's tube end. In this optical system, this disclosure provides an optical system for the tube end 2, which can be used in conjunction with the objective lens 1 in a parallel confocal microscope system. Through a reasonable optical structure setting, the illumination and detection imaging optical paths of the parallel confocal microscope can share the tube end. In the illumination optical path, the tube lens can focus light onto the back focal plane of objective lens 1, achieving uniform illumination of the object surface. In the detection imaging optical path, the tube lens receives the parallel light emitted from objective lens 1. The parallel light optical path between objective lens 1 and tube lens 2 can be extended with other optical path insertion expansion components, while ensuring the quality of microscopic imaging. Due to the characteristics of parallel confocal microscopes, this disclosure optimizes the parameters of each lens in the tube lens to address the aberrations introduced by the turntable, and adopts an aberration-correcting design to ensure clear imaging of the microscopic system in the visible light range, with uniform and symmetrical clarity on both sides of the image. At the same time, the arrangement and shape of each lens are optimized, giving the optical system of the tube lens the characteristics of reasonable tolerance range, simple assembly, and good tolerance performance.

[0112] Various embodiments of the invention have been described above in detail. Although these descriptions directly depict the above embodiments, it should be understood that modifications and / or variations to the specific embodiments shown and described herein will occur to those skilled in the art. Any such modifications or variations falling within the scope of this specification are also intended to be included herein. Unless specifically indicated, the inventors intend that the words and phrases in the specification and claims be given the common and customary meaning to those skilled in the art.

[0113] The above description of various embodiments of the invention known to the applicant at the time of filing this application is intended for illustrative and descriptive purposes. This description is not intended to be exhaustive, nor does it limit the invention to the exact forms disclosed, and many modifications and variations can be made based on the foregoing teachings. The described embodiments are intended 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 intended particular use. Therefore, the invention is not intended to be limited to the specific embodiments disclosed for implementing the invention.

[0114] While specific embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that variations and modifications can be made based on the teachings of the invention without departing from the invention and its broader aspects, and therefore the appended claims are intended to cover all such changes and modifications within the true spirit and scope of the invention. Those skilled in the art will understand that, in general, the terminology used in this invention is intended to be “open” terminology (e.g., the term “comprising” should be interpreted as “including but not limited to”, the term “having” should be interpreted as “at least having”, the term “comprising” should be interpreted as “including but not limited to”, etc.).

Claims

1. An optical system for a confocal microscope, the confocal microscope comprising an objective lens, a tube lens, and a rotating disk, characterized in that: The tube endoscope includes 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 arranged sequentially. The distance between the first lens group and the image back focal plane of the objective lens on the optical axis is defined as a first distance; the distance between the second lens group and the third lens group on the optical axis is defined as a second distance; and the minimum distance between the position of the light source and the turntable on the optical axis is defined as a third distance. The third distance, the focal length of the third lens group, and the second distance satisfy the following condition: Wherein, L3 is the third distance, F3 is the focal length of the third lens group, and L2 is the second distance; The absolute value of the ratio of the first distance to the focal length of the tube mirror is within a first preset range, and the absolute value of the ratio of the focal length of the first lens group to the focal length of the tube mirror is within a second preset range. The first preset range is related to the size of the space between the tube mirror and the objective lens, as well as the length of the tube mirror, and the second preset range is related to the optical power of the first lens group.

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

3. The optical system of the confocal microscope according to claim 1, characterized in that: The third lens group includes multiple lenses, including a fourth lens that is far from the light source and a fifth lens that is close to the light source.

4. The optical system of the confocal microscope according to claim 3, characterized in that: The 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.

5. The optical system of the confocal microscope according to claim 1, characterized in that: The second lens group includes a cemented doublet lens, which comprises a second lens with positive optical power and a third lens with negative optical power.

6. The optical system of the confocal microscope according to claim 5, characterized in that: The focal length of the second lens in the second lens group is greater than or equal to 40mm and less than or equal to 100mm; the focal length of the third lens in the second lens group is greater than or equal to -50mm and less than or equal to -20mm.

7. The optical system of the confocal microscope according to claim 5, 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 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.

8. The optical system of the confocal microscope according to claim 5 or 7, characterized in that: The Abbe coefficient of the second lens is greater than or equal to 60 and less than or equal to 70, and the Abbe coefficient of the third lens is greater than or equal to 30 and less than or equal to 50.

9. The optical system of the confocal microscope according to claim 1, characterized in that: The first preset range is greater than 0.5 and less than 1.

0.

10. The optical system of the confocal microscope according to claim 1, characterized in that: The second preset range is greater than 0.5 and less than 1.

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