A broadband miniature objective lens and imaging device

Abstract

This invention discloses a broadband miniature objective and imaging device. The objective, arranged along the optical axis from object to image, comprises: a positive optical power first lens (object concave, image convex, meniscus), a negative optical power second lens (meniscus), a positive optical power triplet lens group (composed of biconvex, biconcave, and biconvex lenses), and two biconvex positive optical power lenses. This invention utilizes only seven spherical lenses, and through a specific optical power configuration and proportional design, achieves diffraction-limited imaging with an image-side or tissue-side NA ≥ 0.5 and a field of view ≥ 240 μm within a broad spectral range of 480–860 nm, under extremely small outer diameter and length constraints. The miniature objective of this invention supports simultaneous high-resolution imaging with multicolor excitation and multichannel detection, enabling simultaneous observation of different fluorescent labels without changing the objective, making it particularly suitable for immersion imaging environments. Imaging devices constructed based on this objective can be widely applied in biomedical imaging fields such as endoscopy and confocal microscopy.

Description

Technical Field

[0001] This invention belongs to the field of biomedical imaging technology, specifically a broadband miniature objective and imaging device, which is suitable for applications such as multispectral confocal endoscopic imaging and biomedical microscopy. Background Technology

[0002] In the field of biomedical imaging, confocal endoscopic imaging technology based on imaging fiber bundles or single-fiber scanning has become an important tool for visualizing the microstructure of in vivo tissues due to its minimally invasive capabilities and subcellular resolution. This technology delivers the probe to the target area through natural cavities or minimally invasive incisions, using exogenous fluorescent markers to achieve in-situ tissue imaging, avoiding the invasive sampling of traditional biopsies, and enabling real-time acquisition of dynamic cell morphology information. This technology is not only indispensable in model animal imaging research but also demonstrates unique advantages in clinical applications such as early disease diagnosis, molecular marker detection, and treatment monitoring.

[0003] With the continuous advancement of fluorescent labeling technology, the development of targeted and specific fluorescent labels has provided new possibilities for the detection of specific diseases and early pathological analysis. Building upon this, multispectral endoscopic imaging systems, through the coordinated operation of multiple excitation wavelengths and detection channels, can simultaneously excite and distinguish different types of fluorescent labels. On the one hand, it can accurately acquire fluorescence emission spectral information at various points in space; on the other hand, it can simultaneously observe diverse cell types, functional states, and their interactions within the same tissue sample. By simultaneously detecting multiple biomarkers, the system can not only present the spatial morphological distribution of the sample but also achieve an organic combination of structural and functional imaging, thereby greatly expanding the application scope of confocal endoscopic imaging.

[0004] As the core optical component of a confocal endoscopic imaging system, the miniature objective lens performs the dual crucial functions of focusing excitation light and collecting fluorescence signals. In the excitation optical path, the miniature objective lens precisely focuses the excitation light output from the fiber bundle or single-mode fiber to a specific depth within the tissue, achieving optical sectioning through point-by-point scanning, thus laying the foundation for obtaining high-resolution tomographic images. In the probe optical path, the objective lens efficiently collects the fluorescence signal generated by the sample and returns it along the original path. Simultaneously, it works in conjunction with the probe pinhole to effectively block stray light outside the focal plane, thereby significantly improving image contrast and axial resolution.

[0005] However, existing technologies still face significant bottlenecks. Current mainstream miniature objectives typically optimize their optical structures for a single excitation wavelength, resulting in a limited effective spectral range and severely restricting the clinical application of multispectral confocal endoscopic imaging technology. As an attempt at improvement, patent CN119805714B discloses a multi-marker endoscopic imaging lens for the digestive tract, employing a seven-lens structure to achieve broad-spectral imaging of 488–860 nm. However, the sixth lens in this design is a bilateral aspherical lens. While aspherical lenses are advantageous for aberration correction, they face a series of engineering challenges in medical-grade miniature optical systems, including high mold costs for injection molding or precision molding, high processing difficulty, high testing costs, performance drift due to changes in aspherical surface shape under high and low temperature environments, and difficulty in ensuring batch consistency. Therefore, achieving a broad-spectrum, high numerical aperture, and miniaturized objective design while ensuring adaptability to immersion imaging environments using only spherical lenses remains a critical technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a broadband miniature objective lens to overcome the limitations of existing technologies. This miniature objective lens can simultaneously capture the endogenous biochemical characteristics and / or exogenous fluorescence signals of biological samples on a single imaging platform, achieving high-resolution, high-contrast multi-target simultaneous observation and imaging, thereby enabling the simultaneous and accurate identification of multiple components in complex biological samples.

[0007] The technical solution to achieve the purpose of this invention is as follows: On the one hand, a broadband miniature objective lens is provided, wherein the following are arranged sequentially along the optical axis from the object side to the image side:

[0008] The first lens group, with positive optical power, is used to collect light rays from a large field of view and to perform preliminary correction of system aberrations;

[0009] A second lens group with positive optical power is used to correct at least axial chromatic aberration, transverse chromatic aberration, and spherical aberration by combining and configuring the optical power of the lenses.

[0010] A third lens group with positive optical power is used to further compress the beam and match the image-side numerical aperture requirements through an optimized combination of high refractive index / low dispersion materials, while constraining the overall length of the optical system.

[0011] The optical power of the first lens group, the second lens group and the third lens group satisfies a specific relationship, enabling the miniature objective lens to achieve diffraction-limited imaging quality in a wide spectral range of 480nm to 860nm, while maintaining the miniaturized structural features.

[0012] All lenses in the miniature objective are spherical lenses.

[0013] Furthermore, the first lens group with positive optical power includes a first lens and a second lens arranged sequentially along the optical axis from the object side to the image side; wherein, the first lens has positive optical power and the second lens has negative optical power; the object side of the first lens is concave and the image side is convex, forming a meniscus shape; the object side of the second lens is convex and the image side is concave, forming a meniscus shape.

[0014] Furthermore, the second lens group with positive optical power includes a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side to the image side along the optical axis. The third lens, the fourth lens, and the fifth lens are cemented together to form a cemented triplet lens. The object side and the image side of the third lens and the fifth lens are convex, forming a biconvex shape. The object side and the image side of the fourth lens are concave, forming a biconcave shape.

[0015] Furthermore, the third lens group with positive optical power includes a sixth lens and a seventh lens arranged sequentially from the object side to the image side along the optical axis. The object side and the image side of the sixth lens and the seventh lens are convex, forming a biconvex shape.

[0016] Furthermore, the effective focal lengths of each lens in the miniature objective satisfy the following proportional condition:

[0017] 11 < f3 / f 345 <1.5;

[0018] 0.5 < f4 / f 345 <0.7;

[0019] 1.2 < f5 / f 345 <1.4;

[0020] Where f3 to f5 represent the effective focal lengths of the third to fifth lenses, respectively. 345 This is the effective focal length of the cemented triplet lens.

[0021] Furthermore, the effective focal length of each lens in the miniature objective lens satisfies:

[0022] 4.5mm < f1 < 4.8mm;

[0023] -12mm < f2 < -11.3mm;

[0024] 2.3mm < f 345 <2.8mm;

[0025] 3.2mm < f6 < 3.5mm;

[0026] 0.7mm < f7 < 1.1mm;

[0027] In the formula, f1, f2, f6 and f7 represent the effective focal lengths of the first lens, the second lens, the sixth lens and the seventh lens, respectively.

[0028] Furthermore, the sixth lens satisfies the following condition:

[0029] 1.9 < Nd6 < 2;

[0030] 30 < νd6 < 35;

[0031] In the formula, Nd6 and νd6 are the refractive index and Abbe number of the sixth lens, respectively.

[0032] Furthermore, the optical performance indicators of the miniature objective lens meet at least one of the following conditions: image-side numerical aperture NA ≥ 0.5; image-side field of view FOV ≥ 240 μm; working distance WD ≤ 100 μm; total optical length TTL ≤ 9 mm ≤ TTL ≤ 12 mm; and optical lens mechanical outer diameter ≤ 2 mm.

[0033] Furthermore, the miniature objective is a liquid immersion objective, and the image-side immersion medium of the liquid immersion objective is physiological saline or deionized water.

[0034] On the other hand, an imaging device is provided that includes the broadband miniature objective lens.

[0035] Compared with the prior art, the significant advantages of this invention are:

[0036] (1) Compared with existing solutions that include aspherical or more lenses, the present invention consists of only seven spherical lenses, which completely avoids the industry pain points such as the difficulty in processing aspherical lenses and the high testing cost, significantly reducing manufacturing costs and mass production difficulty, and is particularly suitable for medical imaging equipment that requires mass production.

[0037] (2) This invention employs a synergistic optimization design of a triple-cemented lens and front and rear lens groups, combined with a reasonable combination of high refractive index / low dispersion materials, to achieve diffraction-limited imaging in an ultra-wide spectral range of 480nm to 860nm. This allows a single objective lens to be compatible with multiple fluorescent dyes simultaneously, supports simultaneous incident multicolor excitation light sources and high-resolution synchronous detection of multi-channel fluorescence signals, and enables multi-label synchronous observation of complex biological samples without changing the objective lens.

[0038] (3) By configuring the optical power of positive-negative-positive (triplex)-positive-positive and limiting the focal length ratio within the triplex lens group, high-resolution imaging with image-side numerical aperture NA≥0.5 is achieved within a very small outer diameter and length limit. At the same time, the working distance WD≤100μm enables ultra-high resolution observation close to the tissue surface. It is also specially optimized for physiological saline or deionized water environment, making it very suitable for in situ in vivo imaging in the biomedical field.

[0039] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of a broadband miniature objective lens in one embodiment.

[0041] Figure 2 This is an MTF curve of a miniature objective lens provided in one embodiment.

[0042] Figure 3 This is a graph showing the relationship between the average Strehl ratio and wavelength for a miniature objective provided in one embodiment. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0044] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0045] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0046] In one embodiment, a broadband miniature objective lens is provided, comprising, sequentially arranged along the optical axis from the object side to the image side:

[0047] The first lens group, with positive optical power, is used to collect light rays from a large field of view and to perform preliminary correction of system aberrations;

[0048] A second lens group with positive optical power is used to correct at least axial chromatic aberration, transverse chromatic aberration, and spherical aberration by combining and configuring the optical power of the lenses.

[0049] A third lens group with positive optical power is used to further compress the beam and match the image-side numerical aperture requirements through an optimized combination of high refractive index / low dispersion materials, while constraining the overall length of the optical system.

[0050] The optical power of the first lens group, the second lens group and the third lens group satisfies a specific relationship, enabling the miniature objective lens to achieve diffraction-limited imaging quality in a wide spectral range of 480nm to 860nm, while maintaining the miniaturized structural features.

[0051] All lenses in the miniature objective are spherical lenses.

[0052] Furthermore, in one embodiment, combined with Figure 1 The first lens group with positive optical power includes a first lens L1 and a second lens L2 arranged sequentially from the object side to the image side along the optical axis; wherein, the first lens L1 has positive optical power and the second lens L2 has negative optical power; the object side of the first lens L1 is concave and the image side is convex, forming a meniscus shape; the object side of the second lens L2 is convex and the image side is concave, forming a meniscus shape.

[0053] The second lens group with positive optical power includes a third lens L3, a fourth lens L4, and a fifth lens L5 arranged sequentially from the object side to the image side along the optical axis. The third lens L3, the fourth lens L4, and the fifth lens L5 are cemented together to form a cemented triplet lens. The object side and the image side of the third lens L3 and the fifth lens L5 are convex, forming a biconvex shape. The object side and the image side of the fourth lens L4 are concave, forming a biconcave shape.

[0054] The third lens group with positive optical power includes a sixth lens L6 and a seventh lens L7 arranged sequentially from the object side to the image side along the optical axis. The object side of the sixth lens L6 and the seventh lens L7 are convex, and the image side is convex, forming a biconvex shape.

[0055] Preferably, in some embodiments, the effective focal lengths of the lenses in the miniature objective lens satisfy the following proportional conditions:

[0056] 11 < f3 / f 345 <1.5;

[0057] 0.5 < f4 / f 345 <0.7;

[0058] 1.2 < f5 / f 345 <1.4;

[0059] Where f3 to f5 represent the effective focal lengths of the third lens L3 to the fifth lens L5, respectively. 345 This is the effective focal length of the cemented triplet lens.

[0060] Preferably, in some embodiments, the effective focal length of each lens in the miniature objective lens satisfies:

[0061] 4.5mm < f1 < 4.8mm;

[0062] -12mm < f2 < -11.3mm;

[0063] 2.3mm < f 345 <2.8mm;

[0064] 3.2mm < f6 < 3.5mm;

[0065] 0.7mm < f7 < 1.1mm;

[0066] Where f1, f2, f6 and f7 represent the effective focal lengths of the first lens L1, the second lens L2, the sixth lens L6 and the seventh lens L7, respectively.

[0067] Preferably, in some embodiments, the sixth lens satisfies the following condition:

[0068] 1.9 < Nd6 < 2;

[0069] 30 < νd6 < 35;

[0070] In the formula, Nd6 and νd6 are the refractive index and Abbe number of the sixth lens, respectively.

[0071] The aforementioned high refractive index design helps reduce the angle of incidence of light on the lens surface, thereby reducing monochromatic aberrations such as spherical aberration and coma; combined with low dispersion characteristics, it can significantly reduce the focusing differences of light of different wavelengths, suppress chromatic aberration, and further correct advanced aberrations, thereby comprehensively improving image clarity and color fidelity.

[0072] Through the above-mentioned optical power allocation and material selection, the focal position of each wavelength tends to be consistent, thereby achieving diffraction-limited imaging quality in a wide spectral range of 480 nm to 860 nm.

[0073] Preferably, in some embodiments, the optical performance indicators of the miniature objective lens meet at least one of the following conditions: image-side numerical aperture NA ≥ 0.5; image-side field of view FOV ≥ 240 μm; working distance WD ≤ 100 μm; total optical length TTL ≤ 9 mm ≤ TTL ≤ 12 mm; and optical lens mechanical outer diameter ≤ 2 mm.

[0074] Preferably, in some embodiments, the miniature objective is an immersion objective, and the image-side immersion medium is, but is not limited to, physiological saline or deionized water.

[0075] Here, through the immersion design, the refractive index environment of biological tissues can be effectively matched, reducing spherical aberration and improving imaging resolution within the working distance, making it particularly suitable for in vivo high-resolution imaging of living tissues.

[0076] In one embodiment, an imaging device is provided that includes the broadband miniature objective.

[0077] Here, the imaging device can be a biomedical imaging device such as an endoscope or a confocal microscopy imaging device.

[0078] As a specific example, the invention will be further verified and illustrated in one embodiment.

[0079] The specific parameters of each lens in the broadband miniature objective of this invention are detailed in Table 1.

[0080] Table 1. Specific parameters of each lens in the broadband miniature objective.

[0081]

[0082] The effective focal lengths of the aforementioned miniature objectives for each lens are: f1 = 4.66 mm, f2 = -11.47 mm, f3 = 1.22 mm, f4 = 0.65 mm, f5 = 1.28 mm, f6 = 0.65 mm, f7 = 0.65 mm, f8 = 0.65 mm, f9 = 0.65 mm, f1 ... 345 =2.44mm, f6=3.39mm, f7=0.81mm, where f1 to f7 are the effective focal lengths of the first lens L1 to the seventh lens L7, respectively. 345 This is the effective focal length of the cemented triplet lens. The above parameters satisfy the following conditions: , , .

[0083] Other key performance indicators of this objective lens include: refractive index of the sixth lens Nd6 = 1.953, Abbe number νd6 = 32.31 (satisfying 1.9 < Nd6 < 2; 30 < νd6 < 35); image-side numerical aperture NA = 0.55 (satisfying NA ≥ 0.5); image-side field of view FOV = 300 μm (satisfying FOV ≥ 240 μm); working distance WD = 100 μm (satisfying WD ≤ 100 μm); total length TTL = 9.95 mm (satisfying 9 mm ≤ TTL ≤ 12 mm); and mechanical outer diameters of each lens are 1.78 mm, 1.84 mm, 1.5 mm, 1.4 mm, and 1.2 mm (all ≤ 2 mm). Considering a standard housing thickness of 0.2 mm, the final probe outer diameter can be controlled within 2.6 mm. Based on a 2x image-to-object magnification (M=2) and an image-side field of view of 300μm, the objective lens has an object-side field of view of 600μm, which precisely matches the scanning range of an imaging fiber bundle or single-mode fiber with an imaging field of view of 600μm.

[0084] Figure 2 The modulation transfer function (MTF) curves of the broadband miniature objective lens provided in this embodiment are shown. The figures display the MTF curves for the center field of view (0 field of view), 0.7 field of view, and full field of view (1.0 field of view) at representative wavelengths of 480 nm, 550 nm, 660 nm, 780 nm, and 860 nm, respectively. As can be seen from the figures, the MTF values ​​for each field of view and wavelength are close to diffraction-limited, indicating that the present invention has good imaging resolution and contrast transfer performance over a wide spectral range.

[0085] Figure 3 The graph shows the relationship between the average Strehl ratio and wavelength for the broadband miniature objective provided in this embodiment. The horizontal axis represents wavelength (in nm), and the vertical axis represents the average Strehl ratio (dimensionless). The graph shows the average Strehl ratio variations for the central field of view (0 nm), 0.7 nm, and the full field of view (1.0 nm) within the spectral range of 480 nm to 860 nm. As can be seen from the graph, within the broadband spectral range of 480 nm to 860 nm, the average Strehl ratio for each field of view is greater than 0.8, satisfying the Rayleigh criterion (Strelhl ratio ≥ 0.8) for diffraction limitation, indicating that the present invention exhibits excellent imaging quality throughout the entire working wavelength range. The fluctuation of the average Strehl ratio for each field of view within the 480 nm to 860 nm range is less than 0.1, indicating good chromatic aberration correction.

[0086] This invention employs a synergistic optimization design of a triple-cemented lens and front and rear lens groups, combined with a suitable combination of high refractive index / low dispersion materials, to achieve diffraction-limited imaging over a broad spectral range of 480 nm to 860 nm without introducing aspherical elements. Benefiting from this broad spectral characteristic, the miniature objective proposed in this invention can simultaneously support high-resolution imaging with multicolor excitation and multichannel detection, allowing for simultaneous observation of different fluorescent labels without changing the objective lens, making it particularly suitable for immersion imaging environments. Furthermore, the imaging device proposed in this invention can be widely applied in biomedical imaging fields such as endoscopy and confocal microscopy.

[0087] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.

Claims

1. A broadband miniature objective lens, characterized in that, Along the optical axis from the object side to the image side, the following are arranged sequentially: The first lens group, with positive optical power, is used to collect light rays from a large field of view and to perform preliminary correction of system aberrations; A second lens group with positive optical power is used to correct at least axial chromatic aberration, transverse chromatic aberration, and spherical aberration by combining and configuring the optical power of the lenses. A third lens group with positive optical power is used to further compress the beam and match the image-side numerical aperture requirements through an optimized combination of high refractive index / low dispersion materials, while constraining the overall length of the optical system. The optical power of the first lens group, the second lens group and the third lens group satisfies a specific relationship, enabling the miniature objective lens to achieve diffraction-limited imaging quality in a wide spectral range of 480nm to 860nm, while maintaining the miniaturized structural features. All lenses in the miniature objective are spherical lenses.

2. The broadband miniature objective lens according to claim 1, characterized in that, The first lens group with positive optical power includes a first lens and a second lens arranged sequentially from the object side to the image side along the optical axis; wherein, the first lens has positive optical power and the second lens has negative optical power; the object side of the first lens is concave and the image side is convex, forming a meniscus shape; the object side of the second lens is convex and the image side is concave, forming a meniscus shape.

3. The broadband miniature objective lens according to claim 2, characterized in that, The second lens group with positive optical power includes a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side to the image side along the optical axis. The third lens, the fourth lens, and the fifth lens are cemented together to form a cemented triplet lens. The object side and the image side of the third lens and the fifth lens are convex, forming a biconvex shape. The object side and the image side of the fourth lens are concave, forming a biconcave shape.

4. The broadband miniature objective lens according to claim 3, characterized in that, The third lens group with positive optical power includes a sixth lens and a seventh lens arranged sequentially from the object side to the image side along the optical axis. The object side and the image side of the sixth lens and the seventh lens are convex, forming a biconvex shape.

5. The broadband miniature objective lens according to claim 4, characterized in that, The effective focal lengths of each lens in the miniature objective lens satisfy the following proportional condition: 11<f3 / f 345 <1.5; 0.5<f4 / f 345 <0.7; 1.2<f5 / f 345 <1.4; Where f3 to f5 represent the effective focal lengths of the third to fifth lenses, respectively. 345 This is the effective focal length of the cemented triplet lens.

6. The broadband miniature objective lens according to claim 5, characterized in that, The effective focal length of each lens in the miniature objective lens satisfies the following: 4.5mm < f1 < 4.8mm; -12mm < f2 < -11.3mm; 2.3mm<f 345 <2.8mm; 3.2mm < f6 < 3.5mm; 0.7mm < f7 < 1.1mm; In the formula, f1, f2, f6 and f7 represent the effective focal lengths of the first lens, the second lens, the sixth lens and the seventh lens, respectively.

7. The broadband miniature objective lens according to claim 6, characterized in that, The sixth lens satisfies the following condition: 1.9 < Nd6 < 2; 30 < νd6 < 35; In the formula, Nd6 and νd6 are the refractive index and Abbe number of the sixth lens, respectively.

8. The broadband miniature objective lens according to claim 7, characterized in that, The optical performance of the miniature objective lens meets at least one of the following conditions: image-side numerical aperture NA ≥ 0.5; image-side field of view FOV ≥ 240 μm; working distance WD ≤ 100 μm; total optical length TTL ≤ 9 mm ≤ TTL ≤ 12 mm; and optical lens mechanical outer diameter ≤ 2 mm.

9. The broadband miniature objective lens according to claim 8, characterized in that, The miniature objective is a liquid immersion objective, and the image-side immersion medium of the liquid immersion objective is physiological saline or deionized water.

10. An imaging device, characterized in that, It includes a broadband miniature objective as described in any one of claims 1 to 9.

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