Achromatic coupling objective lens with large field of view and wide spectrum

Abstract

The present invention discloses a large-field-of-view wide-spectrum achromatic coupling objective lens, comprising a first lens group and a second lens group coaxially arranged from the object side to the image side; the first lens group has a negative focal length, and is composed of a first cemented lens and a second cemented lens coaxially arranged from the object side to the image side; the second lens group has a positive focal length, and is composed of a third cemented lens, a fourth cemented lens and a meniscus lens coaxially arranged from the object side to the image side. By adjusting the specific parameters of each lens group and each lens block, the numerical aperture of the coupling objective lens of the present invention is matched with the numerical aperture of the optical fiber bundle, and at the same time, the excitation light of 488nm and the fluorescence spectrum of 500~600nm are achromatically designed and other aberrations are balanced to improve the coupling efficiency and sensitivity of the system, the working distance reaches 6mm, and the imaging field reaches 1mm, realizing diffraction-limited imaging in a large field of view and a wide spectrum.

Description

Technical Field

[0001] The invention belongs to the technical field of endoscopic imaging, in particular to a large-viewing-field and wide-spectrum achromatic coupling objective lens for a confocal endoscope. Background Art

[0002] In the field of biomedical imaging, fiber-optic bundle-based confocal endoscopic imaging technology has attracted much attention because of its ability to provide high-resolution cellular-level morphological information. This technology uses fluorescent markers to perform non-invasive in situ imaging of in vivo tissues, avoiding the invasive operation of traditional biopsy sampling, and is therefore widely used in cell structure detection, protein expression analysis, and biomarker identification. However, the field of view (FOV) of existing systems at a resolution of 1~2μm is usually limited to 240~300μm. This limitation is not conducive to the observation and diagnosis of large-area lesions and increases the risk of false-negative diagnosis. Therefore, the development of imaging systems with larger FOVs is crucial to improving diagnostic accuracy.

[0003] In order to achieve imaging of larger tissue areas, an imaging fiber bundle with a larger FOV is required. For example, the use of Fujikura FIGH-50-1100N fiber bundle can extend the imaging FOV to 500μm while ensuring high-resolution imaging. However, as the imaging FOV increases, the FOV of the coupled objective lens at the front end of the fiber bundle also needs to be increased accordingly, which may lead to severe off-axis aberrations and a decrease in image quality. For this reason, the performance of the coupled objective lens used in the large-field confocal endoscopic imaging system and its matching with the optical parameters of the entire system become particularly critical. An ideal coupling objective lens must simultaneously meet the following key requirements: (1) it must be diffraction limited to ensure high coupling efficiency and image contrast; (2) the FOV must match that of the imaging system to avoid off-axis aberrations and image quality degradation; (3) the numerical aperture (NA) of the coupling objective lens should match the NA of the fiber bundle to avoid resolution loss and crosstalk; (4) it must have a sufficient working distance to accommodate the mechanical structure design of the fiber bundle connector; and (5) it must cover a wide spectral range of excitation light and fluorescence to ensure that higher light flux fluorescence can be detected to compensate for the loss of signal-to-noise ratio caused by short integration time in fast imaging.

[0004] Therefore, designing a new type of coupling objective lens can improve coupling efficiency and reduce crosstalk while ensuring high-quality imaging, and can adapt to the needs of fast and large-field imaging. This is of great significance for promoting the application of confocal endoscopic imaging technology in clinical diagnosis and biomedical research. Summary of the invention

[0005] The present invention aims to provide a large-field-of-view wide-spectrum achromatic coupling objective lens to break through the limitations of the prior art and achieve fast large-field-of-view confocal endoscopic imaging.

[0006] The technical solution to achieve the purpose of the present invention is: a large-field-of-view wide-spectrum achromatic coupled objective lens, the coupled objective lens comprising a first lens group and a second lens group coaxially arranged in sequence from the object side to the image side; the first lens group has a negative focal power, comprising a first cemented lens and a second cemented lens coaxially arranged in sequence from the object side to the image side; the second lens group has a positive focal power, comprising a third cemented lens, a fourth cemented lens and a meniscus lens coaxially arranged in sequence from the object side to the image side; the effective focal length of each lens and the effective focal length of the coupled objective lens satisfy:

[0007]

[0008] in, is the effective focal length of the first doublet lens, is the effective focal length of the second doublet lens, is the effective focal length of the third doublet lens, is the effective focal length of the fourth cemented lens, is the effective focal length of the meniscus lens, and f is the effective focal length of the coupled objective lens.

[0009] Furthermore, the first cemented lens is a double cemented lens with positive optical power formed by cementing a first lens and a second lens, the first lens has a concave surface facing the object side and a concave surface facing the image side, the second lens has a convex surface facing the object side and a convex surface facing the image side, and the concave surface of the first lens facing the image side and the convex surface of the second lens facing the object side are cemented together.

[0010] Furthermore, the second cemented lens is a double cemented lens with negative optical power formed by cementing a third lens and a fourth lens, the third lens has a concave surface facing the object side and a concave surface facing the image side, the fourth lens has a convex surface facing the object side and a convex surface facing the image side, and the concave surface of the third lens facing the image side and the convex surface of the fourth lens facing the object side are cemented together.

[0011] Furthermore, the third cemented lens is a double cemented lens with positive optical power formed by cementing a fifth lens and a sixth lens, the fifth lens has a convex surface facing the object side and a concave surface facing the image side, the sixth lens has a convex surface facing the object side and a convex surface facing the image side, and the concave surface of the fifth lens facing the image side and the convex surface of the sixth lens facing the object side are cemented together.

[0012] Further, the fourth cemented lens is a double cemented lens with positive focal power formed by cementing a seventh lens and an eighth lens, the seventh lens has a convex surface facing the object side and a convex surface facing the image side, the eighth lens has a concave surface facing the object side and a concave surface facing the image side, and the convex surface of the seventh lens facing the image side and the concave surface of the eighth lens facing the object side are cemented together.

[0013] Furthermore, the meniscus lens is a single lens with positive optical power, which is convex toward the object side and concave toward the image side.

[0014] Furthermore, the diffraction-limited field of view of the coupling objective lens is ≥1 mm.

[0015] Furthermore, the coupling objective lens satisfies the following conditions:

[0016] ;

[0017] Where R is the radius of curvature of the lens surface closest to the image plane of the meniscus lens, is the effective focal length of the coupling objective lens, and NA is the image-side numerical aperture of the coupling objective lens.

[0018] Furthermore, the image-side numerical aperture NA satisfies:

[0019] .

[0020] Furthermore, the operating wavelength of the coupling objective lens is 488nm~600nm.

[0021] Compared with the prior art, the present invention has the following significant advantages:

[0022] (1) The coupled objective lens can provide a wider imaging range while maintaining high resolution, achieving rapid large-area tissue imaging at cellular resolution, and improving the accuracy and efficiency of diagnosis. At the same time, by optimizing the design of the coupled objective lens, the problems of off-axis aberration and image quality degradation caused by the increase in imaging FOV are overcome, which is crucial for the subsequent comprehensive assessment of the lesion area and improving the accuracy of targeted biopsy.

[0023] (2) The coupled objective lens is designed to be achromatic for the excitation light and the entire fluorescence spectrum to maintain high temporal resolution and high sensitivity, which is beneficial for shortening the observation time while improving the accuracy and detection rate of targeted biopsy.

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of a large-field-of-view wide-spectrum achromatic coupling objective lens in one embodiment.

[0026] Figure 2 FIG. 4 is a diagram of lateral chromatic aberration of a coupling objective lens provided in one embodiment.

[0027] Figure 3 The figure is a graph showing the relationship between the root mean square radius of the diffuse spot and the normalized field of view of a coupling objective lens provided in one embodiment.

[0028] Figure 4 The figure is a graph showing the relationship between the wavefront difference RMS value and the wavelength of a coupling objective lens provided in one embodiment.

[0029] Figure 5 FIG. 4 is a graph showing the relationship between the average Strehl Ratio and the field of view of a coupling objective lens provided in one embodiment. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0031] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0032] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0033] In one embodiment, in combination Figure 1 , provides a large-field-of-view wide-spectrum achromatic coupled objective lens, the coupled objective lens comprising a first lens group G1 and a second lens group G2 coaxially arranged from the object side to the image side; the first lens group G1 has a negative focal power, comprising a first cemented lens CL1 and a second cemented lens CL2 coaxially arranged from the object side to the image side; the second lens group G2 has a positive focal power, comprising a third cemented lens CL3, a fourth cemented lens CL4 and a meniscus lens L9 coaxially arranged from the object side to the image side; the effective focal length of each lens satisfies the effective focal length of the coupled objective lens:

[0034]

[0035] in, is the effective focal length of the first doublet lens, is the effective focal length of the second doublet lens, is the effective focal length of the third doublet lens, is the effective focal length of the fourth cemented lens, is the effective focal length of the meniscus lens (L9), and f is the effective focal length of the coupled objective lens.

[0036] In some embodiments, the first cemented lens CL1 is a double cemented lens with positive optical power formed by cementing a first lens L1 and a second lens L2, wherein the first lens L1 has a concave surface facing the object side and a concave surface facing the image side, and the second lens L2 has a convex surface facing the object side and a convex surface facing the image side, and the concave surface of the first lens L1 facing the image side and the convex surface of the second lens L2 facing the object side are cemented together.

[0037] In some embodiments, the second cemented lens CL2 is a doublet lens with negative optical power formed by cementing a third lens L3 and a fourth lens L4, wherein the third lens L3 has a concave surface facing the object side and a concave surface facing the image side, the fourth lens L4 has a convex surface facing the object side and a convex surface facing the image side, and the concave surface of the third lens L3 facing the image side and the convex surface of the fourth lens L4 facing the object side are cemented together.

[0038] In some embodiments, the third cemented lens CL3 is a double cemented lens with positive optical power formed by cementing a fifth lens L5 and a sixth lens L6, the fifth lens L5 has a convex surface facing the object side and a concave surface facing the image side, the sixth lens L6 has a convex surface facing the object side and a convex surface facing the image side, and the concave surface of the fifth lens L5 facing the image side and the convex surface of the sixth lens L6 facing the object side are cemented together.

[0039] In some embodiments, the fourth cemented lens CL4 is a doublet lens with positive refractive power formed by cementing a seventh lens L7 and an eighth lens L8, the seventh lens L7 has a convex surface facing the object side and a convex surface facing the image side, the eighth lens L8 has a concave surface facing the object side and a concave surface facing the image side, and the convex surface of the seventh lens L7 facing the image side and the concave surface of the eighth lens L8 facing the object side are cemented together.

[0040] In some embodiments, the meniscus lens L9 is a single lens with positive optical power that is convex facing the object side and concave facing the image side.

[0041] In some embodiments, the diffraction limited field of view of the coupled objective lens is ≥ 1 mm.

[0042] In some embodiments, the coupling objective lens satisfies the following conditions:

[0043]

[0044] Where R is the radius of curvature of the lens surface of the meniscus lens L9 closest to the image plane, is the effective focal length of the coupling objective lens, and NA is the image-side numerical aperture of the coupling objective lens.

[0045] In some embodiments, the image-side numerical aperture NA satisfies:

[0046] .

[0047] In some embodiments, the coupling objective lens operates at a wavelength of 488 nm to 600 nm.

[0048] As a specific example, in one of the embodiments, the present invention is further verified and explained.

[0049] The specific parameters of each lens in the large-field-of-view wide-spectrum achromatic coupling objective lens of the present invention are shown in Table 1.

[0050]

[0051] The relationship between the effective focal length of each lens of the above-mentioned coupling objective lens and the effective focal length of the coupling objective lens is: ,in, is the effective focal length of the first cemented lens CL1, is the effective focal length of the second cemented lens CL2, is the effective focal length of the third cemented lens CL3, is the effective focal length of the fourth cemented lens CL4, is the effective focal length of the meniscus lens L9, and f is the effective focal length of the coupling objective lens. This relationship satisfies , The relationship between the curvature radius R of the mirror surface of the meniscus lens L9 closest to the image plane, the effective focal length of the coupling objective lens, and the image-side numerical aperture of the coupling objective lens is: ,satisfy Therefore, it is possible to achromatize the excitation light and the fluorescence signal and balance other aberrations at the same time while maintaining a long working distance.

[0052] Figure 2 : is a lateral chromatic aberration diagram of the coupling objective lens provided by an embodiment of the present invention, the abscissa is the normalized field of view, and the ordinate represents the lateral chromatic aberration value, in μm. It can be seen that the maximum lateral chromatic aberration is 0.2 μm, which is less than the single fiber diameter of the optical fiber bundle of 2 μm.

[0053] Figure 33 is a curve diagram showing the relationship between the root mean square radius of the diffuse spot and the normalized field of view of the coupling objective lens provided in an embodiment of the present invention. It can be seen that in the entire field of view, the root mean square radius of the diffuse spot is smaller than the radius of the Airy disk (shown by the dotted line in the figure), and is smaller than the core distance of the image transmission fiber bundle of 3.3um. Therefore, the coupling objective lens in this embodiment, while ensuring the working distance of 6mm, has a good match between its numerical aperture and the numerical aperture of the optical fiber, which can ensure that only one optical fiber is injected at a time, achieving the highest possible coupling efficiency and the least crosstalk, thereby obtaining the highest image contrast.

[0054] Figure 4 3 is a curve diagram of the relationship between the wavefront difference RMS value and the wavelength of the coupled objective lens provided in an embodiment of the present invention. It can be seen that in the spectral range of 488nm~600nm, the wavefront difference RMS value is smaller than the diffraction-limited wavefront difference value (shown by the solid line in the figure), which proves the achromatic effect.

[0055] Figure 5 3 is a curve diagram of the relationship between the average Strehl Ratio and the field of view of the coupling objective provided in an embodiment of the present invention. It can be seen that the average Strehl Ratio of each field of view is greater than 0.8 (as shown by the solid line in the figure), which satisfies the Strehl criterion, and the diffraction-limited field of view reaches 1 mm.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions are also considered to be within the scope of protection of the present invention.

Claims

1. A large-field-of-view wide-spectrum achromatic coupling objective lens, characterized in that: The coupling objective lens comprises a first lens group (G1) and a second lens group (G2) coaxially arranged in sequence from the object side to the image side; the first lens group (G1) has negative focal power and comprises a first cemented lens and a second cemented lens coaxially arranged in sequence from the object side to the image side; the second lens group (G2) has positive focal power and comprises a third cemented lens, a fourth cemented lens and a meniscus lens (L9) coaxially arranged in sequence from the object side to the image side; the coupling objective lens comprises a total of 9 lenses, and the effective focal length of each lens satisfies the effective focal length of the coupling objective lens: ； in, is the effective focal length of the first doublet lens, is the effective focal length of the second doublet lens, is the effective focal length of the third doublet lens, is the effective focal length of the fourth cemented lens, is the effective focal length of the meniscus lens (L9), and f is the effective focal length of the coupled objective lens; The first cemented lens is a double cemented lens with positive focal power formed by cementing a first lens (L1) and a second lens (L2); the first lens (L1) has a concave surface facing the object side and a concave surface facing the image side; the second lens (L2) has a convex surface facing the object side and a convex surface facing the image side; the concave surface of the first lens (L1) facing the image side and the convex surface of the second lens (L2) facing the object side are cemented together; The second cemented lens is a double cemented lens with negative optical power formed by cementing a third lens (L3) and a fourth lens (L4), wherein the third lens (L3) has a concave surface facing the object side and a concave surface facing the image side, and the fourth lens (L4) has a convex surface facing the object side and a convex surface facing the image side, and the concave surface of the third lens (L3) facing the image side and the convex surface of the fourth lens (L4) facing the object side are cemented together; The third cemented lens is a double cemented lens with positive focal power formed by cementing a fifth lens (L5) and a sixth lens (L6), wherein the fifth lens (L5) has a convex surface facing the object side and a concave surface facing the image side, and the sixth lens (L6) has a convex surface facing the object side and a convex surface facing the image side, and the concave surface of the fifth lens (L5) facing the image side and the convex surface of the sixth lens (L6) facing the object side are cemented together; The fourth cemented lens is a double cemented lens with positive focal power formed by cementing a seventh lens (L7) and an eighth lens (L8), wherein the seventh lens (L7) has a convex surface facing the object side and a convex surface facing the image side, and the eighth lens (L8) has a concave surface facing the object side and a concave surface facing the image side, and the convex surface of the seventh lens (L7) facing the image side and the concave surface of the eighth lens (L8) facing the object side are cemented together; The meniscus lens (L9) is a single lens with positive optical power, which is convex toward the object side and concave toward the image side.

2. The large-field-of-view wide-spectrum achromatic coupling objective lens according to claim 1, characterized in that: The diffraction-limited field of view of the coupling objective lens is ≥1 mm.

3. The large-field-of-view wide-spectrum achromatic coupling objective lens according to claim 1, characterized in that: The coupling objective lens meets the following conditions: ； Where R is the radius of curvature of the lens surface of the meniscus lens (L9) closest to the image plane, is the effective focal length of the coupling objective lens, and NA is the image-side numerical aperture of the coupling objective lens.

4. The large-field-of-view wide-spectrum achromatic coupling objective lens according to claim 3, characterized in that: The image-side numerical aperture NA satisfies: 。 5. The large-field-of-view wide-spectrum achromatic coupling objective lens according to claim 1, characterized in that: The working wavelength of the coupling objective lens is 488nm~600nm.

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