Six groups of seven-piece micro immersion objectives

Abstract

The present invention discloses a six-group and seven-lens micro immersion objective lens, which includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in sequence from the object plane to the image plane. The third lens is a doublet lens; the S11 surface of the first lens is a plane, and the S12 surface bulges towards the image plane. The S21 surface of the second lens bulges towards the object plane, and the S22 surface bulges towards the image plane. The S31 surface of the third lens bulges towards the object plane, the S32 surface bulges towards the object plane, and the S33 surface bulges towards the image plane. The S41 surface and the S42 surface of the fourth lens both bulge towards the object plane. The S51 surface and the S52 surface of the fifth lens are both concave. The S61 surface of the sixth lens bulges towards the object plane, the S62 surface bulges towards the object plane or is a plane. The above composition and layout enable the numerical aperture of the objective lens to reach 0.8. Compared with the objective lens of the existing confocal system, the numerical aperture of the present application is larger, which can further improve the fluorescence collection efficiency, thereby significantly improving the recognition sensitivity for weak fluorescence targets.

Description

Technical Field

[0001] The present invention belongs to the field of confocal microendoscopes, and more specifically, relates to a six-group and seven-element miniature immersion objective lens. Background Art

[0002] A probe-type confocal microendoscope (pCLE) is a medical device that can enter the natural body cavities through channels such as gastroscopes and colonoscopes, and obtain local histological images to achieve the accurate diagnosis of micro-lesions, gastrointestinal diseases, and early gastrointestinal canceration. Because of its characteristics such as fast, accurate, and non-invasive, it may replace traditional endoscopic biopsies and pathological examinations in the near future and become the main means and device for the diagnosis of gastrointestinal diseases and early gastrointestinal canceration.

[0003] The miniature immersion objective lens is the core component of the probe-type confocal microendoscope (pCLE). In a confocal microendoscope, a laser is excited by a laser, and the end face of an optical fiber bundle is scanned through a laser scanning device and a coupling objective lens. After the laser is focused, it is injected into each core of the optical fiber bundle. At the other end of the optical fiber bundle, the injected laser is focused on the observed tissue through the miniature immersion objective lens. The observed object emits fluorescence under the excitation of the injected laser, and the miniature immersion objective lens collects the fluorescence signal from the tissue and returns along the original optical path. As the core component of the probe-type confocal microendoscope (pCLE), the miniature immersion objective lens will enter the instrument channels of endoscopes such as gastroscopes and colonoscopes. For general endoscopes such as gastroscopes and colonoscopes, the inner diameter of the instrument channel is between 2.8 - 3.8 mm. In order to be compatible with the instrument channels of different endoscopes, the mechanical outer diameter of the miniature immersion objective lens is preferably less than 2.8 mm. At the same time, considering the structure of the endoscope, the overall length of the miniature immersion objective lens is limited.

[0004] Currently, the numerical aperture of the current miniature immersion objective lens is generally less than 0.8. In practice, a larger numerical aperture can significantly improve the recognition sensitivity of weak signals. However, the design of the miniature immersion objective lens is restricted by various aspects such as length and outer diameter, so it is difficult to obtain a high-performance miniature immersion objective lens with a large numerical aperture. Summary of the Invention

[0005] In view of the above defects or improvement requirements of the prior art, the present invention provides a six-group and seven-element miniature immersion objective lens, aiming to solve the problem of obtaining a larger numerical aperture while keeping the outer diameter and length meeting clinical requirements.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided a six-group and seven-element miniature immersion objective lens, including a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from the object plane to the image plane, and the third lens is a doublet lens;

[0007] The surface S11 of the first lens is planar, the surface S12 bulges towards the image plane, the surface S21 of the second lens bulges towards the object plane, the surface S22 bulges towards the image plane, the surface S31 of the third lens bulges towards the object plane, the surface S32 bulges towards the object plane, the surface S33 bulges towards the image plane, the surfaces S41 and S42 of the fourth lens both bulge towards the object plane, the surfaces S51 and S52 of the fifth lens are both concave, and the surface S61 of the sixth lens bulges towards the object plane, the surface S62 bulges towards the object plane or is planar. The numerical aperture of the six-group seven-lens micro-immersion objective lens is 0.8.

[0008] Through the above technical solution, the composition and layout of the six-group seven-lens make the numerical aperture of the objective lens reach 0.8. Compared with the objective lens of the existing confocal system, the numerical aperture of this application is larger, which can further improve the fluorescence collection efficiency, thereby significantly improving the recognition sensitivity for weak fluorescence targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is the structural diagram of the six-group seven-lens micro-immersion objective lens in Embodiment 1;

[0010] Figure 2 is the chromatic root mean square radius diagram of Embodiment 1;

[0011] Figure 3 is the field curvature and chromatic dispersion diagram of Embodiment 1;

[0012] Figure 4 is the distortion curve diagram of Embodiment 1;

[0013] Figure 5 is the chromatic focal shift curve diagram of Embodiment 1;

[0014] Figure 6 is the structural diagram of the six-group seven-lens micro-immersion objective lens in Embodiment 2;

[0015] Figure 7 is the chromatic root mean square radius diagram of Embodiment 2;

[0016] Figure 8 is the field curvature and chromatic dispersion diagram of Embodiment 2;

[0017] Figure 9 The distortion curve diagram of Embodiment 2;

[0018] Figure 10 is the chromatic focal shift curve diagram of Embodiment 2.

[0019] In the figure, L1 is the first lens; L2 is the second lens; L3 is the third lens; L4 is the fourth lens; L5 is the fifth lens; L6 is the sixth lens. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be 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 invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] The present invention provides a six-group and seven-element micro immersion objective lens, which includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from the object plane to the image plane. The third lens is a doublet lens.

[0022] The S11 surface of the first lens is a plane, and the S12 surface bulges towards the image plane. The S21 surface of the second lens bulges towards the object plane, and the S22 surface bulges towards the image plane. The S31 surface of the third lens bulges towards the object plane, the S32 surface bulges towards the object plane, and the S33 surface bulges towards the image plane. The S41 surface and the S42 surface of the fourth lens both bulge towards the object plane. The S51 surface and the S52 surface of the fifth lens are both concave. The S61 surface of the sixth lens bulges towards the object plane, the S62 surface bulges towards the object plane or is a plane. The numerical aperture of the six-group and seven-element micro immersion objective lens is 0.8.

[0023] The fluorescence signal excited from the object side starts from the object plane, passes through the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 in sequence, and then forms an image on the image plane, and then forms an image on the photodetector along the image transmission fiber bundle, thereby realizing the detection of tissues. Specifically, the first lens L1 is a near-hemispherical lens. Such a configuration helps to capture light in a low-spherical aberration manner at a high numerical aperture. The marginal rays leaving the first lens L1 still diverge from the optical axis. Therefore, a second lens L2 with a positive focal power is placed after the first lens L1 to bend the light towards the optical axis. The third lens L3 is a doublet achromatic lens, which can further converge the large numerical aperture light emitted from the object plane.

[0024] Furthermore, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the sixth lens L6 all have positive focal powers, and the fifth lens L5 has a negative focal power. In the six-group and seven-element micro immersion objective lens, their focal lengths satisfy the following relationship: 1 < fL1 < 2; 3 < fL2 < 4; 3 < fL3 < 6; 3 < fL4 < 4; -2 < fL5 < -1; 1 < fL6 < 2; fL1, fL2, fL3, fL4, fL5, and fL6 are the equivalent focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens respectively.

[0025] Further, X1 = -1; X2 ≥ 0; X31 < -1; 0 < X32 < 1; X4 > 1; -1 < X5 < 0; X6 ≥ 1; X1, X2, X4, X5, and X6 are the shape factors of the first lens, the second lens, the fourth lens, the fifth lens, and the sixth lens, respectively; X31 and X32 are the shape factors of the two lenses that make up the third lens from the object plane to the image plane.

[0026] The cooperation of these parameters enables the numerical aperture of the six-group and seven-lens micro-immersion objective lens to reach 0.8. While keeping the outer diameter and length meeting the clinical requirements, through optimizing the layout, a larger numerical aperture is obtained, further improving the fluorescence collection efficiency, and thus significantly enhancing the recognition sensitivity for weak fluorescence targets.

[0027] Furthermore, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all spherical lenses, and the sixth lens is an aspherical lens. Finally, the asphericity of the sixth lens is used to correct the Petzval field curvature and correct other remaining aberrations of the entire lens to improve the imaging quality.

[0028] Specifically, the S31 surface of the third lens is the aperture stop surface. The first lens L1 is a plano-convex lens, and the refractive index and Abbe number of its material are 1.833:40.8 respectively. Its curvature is C, |C| < 1. Under the condition of balancing the object-space numerical aperture and the difficulty of aberration correction, the smaller |C| is, the better. Preferably, |C| = 0.8 is taken in the six-group and seven-lens micro-immersion objective lens of the present invention.

[0029] Embodiment 1

[0030] Figure 1 As the structural diagram of this embodiment, as a specific embodiment of the present invention, the materials are represented in the form of "refractive index: Abbe number", and the parameters of each lens are shown in Table 1:

[0031] Table 1

[0032]

[0033] That is, the S11 surface of the first lens L1 is a plane, the full aperture of light passing through is 0.38 mm, the radius of curvature of the S12 surface is -1.33 mm, the full aperture of light passing through is 1.53 mm, the material of the first lens L1 is represented as 1.88:39.2 in the form of "refractive index: Abbe number", the central thickness is 1.39 mm, and the central thickness between the two adjacent surfaces and the second lens L2 is 0.10 mm;

[0034] The curvature radius of the S21 surface of the second lens L2 is 3.31 mm, the full aperture of light transmission is 1.84 mm, the curvature radius of the S22 surface is -9.13 mm, the full aperture of light transmission is 1.87 mm, the material of the second lens L2 is expressed as "refractive index: Abbe number" as 1.79:47.5, the central thickness is 0.55 mm, and the central thickness between the two adjacent surfaces with the third lens L3 is 0.10 mm;

[0035] The curvature radius of the S31 surface of the third lens L3 is 4.16 mm, the full aperture of light transmission is 1.87 mm, the curvature radius of the S32 surface is 1.33 mm, the full aperture of light transmission is 1.85 mm, the curvature radius of the S33 surface is -26.51 mm, the full aperture of light transmission is 1.84 mm. The third lens L3 is composed of two lenses glued together successively from the object surface to the image surface, with the materials expressed as "refractive index: Abbe number" as 1.92:18.9 and 1.95:32.3 respectively. The central thicknesses of the two lenses are 0.40 mm and 0.62 mm in sequence, and the central thickness between the two adjacent surfaces of the third lens L3 and the fourth lens L4 is 0.10 mm;

[0036] The curvature radius of the S41 surface of the fourth lens L4 is 1.44 mm, the full aperture of light transmission is 1.78 mm, the curvature radius of the S42 surface is 4.00 mm, the full aperture of light transmission is 1.60 mm, the material of the fourth lens L4 is expressed as "refractive index: Abbe number" as 1.64:60.2, the central thickness is 0.50 mm, and the central thickness between the two adjacent surfaces with the fifth lens L5 is 0.27 mm;

[0037] The curvature radius of the S51 surface of the fifth lens L5 is -2.54 mm, the full aperture of light transmission is 1.53 mm, the curvature radius of the S52 surface is 1.81 mm, the full aperture of light transmission is 1.45 mm, the material of the fifth lens L5 is expressed as "refractive index: Abbe number" as 1.81:25.4, the central thickness is 0.40 mm, and the central thickness between the two adjacent surfaces with the sixth lens L6 is 0.38 mm;

[0038] The curvature radius of the S61 surface of the sixth lens L6 is 1.03 mm, the full aperture of light transmission is 1.78 mm, the S62 surface bulges towards the object surface, the curvature radius is 15.10 mm, the full aperture of light transmission is 0.74 mm, the material of the sixth lens L6 is expressed as "refractive index: Abbe number" as 1.81:41.0, the central thickness is 1.03 mm, and the central thickness between the S62 surface and the image surface is 0.12 mm.

[0039] Among them, the surfaces marked with "type" as "even" are even aspherical surfaces, and their aspherical equations are as follows:

[0040]

[0041] The aspherical lens coefficients are shown in Table 2.

[0042] Table 2

[0043]

[0044] As Figure 2 shown, it is the chromatic RMS radius map of the focused spot in this embodiment. It can be seen from the figure that within the entire field of view, the chromatic RMS radius of the focused spot is about 1.2um. This indicates that the solution described in the present invention can maximize the coupling efficiency of the optical signal and increase the contrast of the confocal image. As Figure 3 shown, the field curvature in the entire field of view is less than 15um in both the meridional and sagittal directions, and the astigmatism is less than 5um, meeting the design requirements and having excellent imaging performance. As Figure 4 shown, the distortion within the entire field of view is less than 5%, which is less than the limit that the human eye can recognize, meeting the design requirements. As Figure 5 shown, within the designed wavelength range, the focal shift range is about 1.2um, which is much less than the focal shift value of 4.2um under the diffraction limit. This indicates that the six-group and seven-element miniaturized immersion objective lens described in the present invention well corrects chromatic aberration and significantly improves the collection and imaging performance of broadband fluorescence.

[0045] Embodiment 2

[0046] Figure 6 This is the structural diagram of this embodiment. As a specific embodiment of the present invention, the materials are represented in the form of "refractive index: Abbe number", and the parameters of each lens are shown in Table 3:

[0047] Table 3

[0048]

[0049] That is, the S11 surface of the first lens L1 is a plane, the full aperture of light passing through is 0.37mm, the curvature radius of the S12 surface is -1.25mm, the full aperture of light passing through is 1.56mm, the material of the first lens L1 is represented by "refractive index: Abbe number" as 1.88:39.2, the central thickness is 1.54mm, and the central thickness between the two adjacent surfaces of the second lens L2 is 0.10mm;

[0050] The curvature radius of the S21 surface of the second lens L2 is 4.46mm, the full aperture of light passing through is 1.76mm, the curvature radius of the S22 surface is -4.46mm, the full aperture of light passing through is 1.79mm, the material of the second lens L2 is represented by "refractive index: Abbe number" as 1.79:54.7, the central thickness is 0.54mm, and the central thickness between the two adjacent surfaces of the third lens L3 is 0.10mm;

[0051] The radius of curvature of the S31 surface of the third lens L3 is 4.58 mm, the full aperture of light transmission is 1.74 mm, the radius of curvature of the S32 surface is 1.25 mm, the full aperture of light transmission is 1.61 mm, the radius of curvature of the S33 surface is -9.84 mm, the full aperture of light transmission is 1.62 mm. The third lens L3 is composed of two lenses glued together in sequence from the object surface to the image surface. The materials are represented by "refractive index: Abbe number" as 1.78:25.7 and 1.73:54.7 respectively. The central thicknesses of the two lenses are 0.40 mm and 0.72 mm in sequence. The central thickness between two adjacent surfaces of the third lens L3 and the fourth lens L4 is 0.10 mm;

[0052] The radius of curvature of the S41 surface of the fourth lens L4 is 1.43 mm, the full aperture of light transmission is 1.62 mm, the radius of curvature of the S42 surface is 2.21 mm, the full aperture of light transmission is 1.27 mm. The material of the fourth lens L4 is represented by "refractive index: Abbe number" as 1.73:54.7, the central thickness is 0.80 mm, and the central thickness between two adjacent surfaces of the fourth lens L4 and the fifth lens L5 is 0.25 mm;

[0053] The radius of curvature of the S51 surface of the fifth lens L5 is -3.54 mm, the full aperture of light transmission is 1.21 mm, the radius of curvature of the S52 surface is 1.25 mm, the full aperture of light transmission is 1.14 mm. The material of the fifth lens L5 is represented by "refractive index: Abbe number" as 1.78:25.7, the central thickness is 0.40 mm, and the central thickness between two adjacent surfaces of the fifth lens L5 and the sixth lens L6 is 0.48 mm;

[0054] The radius of curvature of the S61 surface of the sixth lens L6 is 0.94 mm, the full aperture of light transmission is 1.62 mm, the S62 surface is a plane, the full aperture of light transmission is 1.03 mm. The material of the sixth lens L6 is represented by "refractive index: Abbe number" as 1.81:41.0, the central thickness is 1.69 mm, and the central thickness between the S62 surface and the image surface is 0.40 mm.

[0055] Among them, the surfaces marked with "type" as "even" are even aspherical surfaces, and their aspherical equations are as follows:

[0056]

[0057] The aspherical lens coefficients are shown in Table 4.

[0058] Table 4

[0059]

[0060] Such as Figure 7As shown, it is the map of the chromatic root mean square radius of the focused spot in this embodiment. It can be seen from the figure that within the entire field of view, the chromatic root mean square radius of the focused spot is about 1.2um, which indicates that the solution described in the present invention can maximize the coupling efficiency of the optical signal and increase the contrast of the confocal image. As Figure 8 shown, the field curvature in the entire field of view is less than 5um both in the meridional direction and the sagittal direction, and the astigmatism is less than 5um, meeting the design requirements and having excellent imaging performance. As Figure 9 shown, the distortion within the entire field of view is less than 5%, which is less than the limit that the human eye can recognize, meeting the design requirements. As Figure 10 shown, within the designed wavelength range, the focal shift range is about 2.0um, which is much smaller than the focal shift value of 5.0um under the diffraction limit. This indicates that the six-group and seven-element miniaturized immersion objective lens described in the present invention well corrects chromatic aberration and significantly improves the collection and imaging performance of broadband fluorescence.

[0061] According to the parameters in the above two embodiments, the data shown in Tables 5 and 6 are obtained, where WFno. is the working F-number.

[0062] Table 5

[0063]

[0064] Table 6

[0065]

[0066] L1 represents the first lens, L2 represents the second lens, L31 represents one lens of the third lens close to the object plane, L32 represents one lens of the third lens close to the image plane, L4 represents the fourth lens, L5 represents the fifth lens, and L6 represents the sixth lens.

[0067] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A six-group and seven-piece micro-immersion objective lens, characterized in that, It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from the object surface to the image surface. The third lens is a doublet lens; The S11 surface of the first lens is a plane, and the S12 surface bulges towards the image surface. The S21 surface of the second lens bulges towards the object surface, and the S22 surface bulges towards the image surface. The S31 surface of the third lens bulges towards the object surface, the S32 surface bulges towards the object surface, and the S33 surface bulges towards the image surface. The S41 surface and the S42 surface of the fourth lens both bulge towards the object surface. The S51 surface and the S52 surface of the fifth lens are both concave. The S61 surface of the sixth lens bulges towards the object surface, the S62 surface bulges towards the object surface or is a plane. The numerical aperture of the six-group and seven-piece micro immersion objective lens is 0.8; The six-group and seven-piece micro immersion objective lens satisfies: 1 < fL1 < 2; 3 < fL2 < 4; 3 < fL3 < 6; 3 < fL4 < 4; -2 < fL5 < -1; 1 < fL6 < 2; fL1, fL2, fL3, fL4, fL5, and fL6 are the equivalent focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens respectively; X1 = -1; X2 ≥ 0; X31 < -1; 0 < X32 < 1; X4 > 1; -1 < X5 < 0; X6 ≥ 1; X1, X2, X4, X5, and X6 are the shape factors of the first lens, the second lens, the fourth lens, the fifth lens, and the sixth lens respectively; X31 and X32 are the shape factors of the two lenses that make up the third lens from the object surface to the image surface.

2. The six-group seven-element micro-immersion objective lens according to claim 1, wherein The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all spherical lenses, and the sixth lens is an aspherical lens.

3. The six-group and seven-element micro-immersion objective lens according to claim 2, wherein The S31 surface of the third lens is the aperture stop surface.

4. The six-group and seven-element micro-immersion objective lens according to claim 2, wherein, The curvature of the first lens is C, and |C| < 1.

5. The six-group seven-element micro-immersion objective lens according to claim 2, characterized in that, The S11 surface of the first lens is a plane, the full aperture of light passing through is 0.38 mm, the radius of curvature of the S12 surface is -1.33 mm, the full aperture of light passing through is 1.53 mm, the refractive index of the material of the first lens is 1.88, the Abbe number is 39.2, the central thickness of the first lens is 1.39 mm, and the central thickness between the two adjacent surfaces and the second lens is 0.10 mm; The radius of curvature of the S21 surface of the second lens is 3.31 mm, the full aperture of light passing through is 1.84 mm, the radius of curvature of the S22 surface is -9.13 mm, the full aperture of light passing through is 1.87 mm, the refractive index of the material of the second lens is 1.79, the Abbe number is 47.5, the central thickness of the second lens is 0.55 mm, and the central thickness between the two adjacent surfaces and the third lens is 0.10 mm; The curvature radius of the S31 surface of the third lens is 4.16 mm, the full aperture for light transmission is 1.87 mm, the curvature radius of the S32 surface is 1.33 mm, the full aperture for light transmission is 1.85 mm, the curvature radius of the S33 surface is -26.51 mm, the full aperture for light transmission is 1.84 mm. The third lens is composed of two lenses glued together in sequence from the object surface to the image surface. The refractive index of the material of one lens is 1.92 and the Abbe number is 18.9, and the refractive index of the material of the other lens is 1.95 and the Abbe number is 32.

3. The central thicknesses of the two lenses are 0.40 mm and 0.62 mm in sequence. The central thickness between the adjacent two surfaces of the third lens and the fourth lens is 0.10 mm; The curvature radius of the S41 surface of the fourth lens is 1.44 mm, the full aperture for light transmission is 1.78 mm, the curvature radius of the S42 surface is 4.00 mm, the full aperture for light transmission is 1.60 mm. The refractive index of the material of the fourth lens is 1.64 and the Abbe number is 60.

2. The central thickness of the fourth lens is 0.50 mm, and the central thickness between the adjacent two surfaces of the fourth lens and the fifth lens is 0.27 mm; The curvature radius of the S51 surface of the fifth lens is -2.54 mm, the full aperture for light transmission is 1.53 mm, the curvature radius of the S52 surface is 1.81 mm, the full aperture for light transmission is 1.45 mm. The refractive index of the material of the fifth lens is 1.81 and the Abbe number is 25.

4. The central thickness of the fifth lens is 0.40 mm, and the central thickness between the adjacent two surfaces of the fifth lens and the sixth lens is 0.38 mm; The curvature radius of the S61 surface of the sixth lens is 1.03 mm, the full aperture for light transmission is 1.78 mm. The S62 surface bulges towards the object surface, the curvature radius is 15.10 mm, the full aperture for light transmission is 0.74 mm. The refractive index of the material of the sixth lens is 1.81 and the Abbe number is 41.

0. The central thickness of the sixth lens is 1.03 mm, and the central thickness between the S62 surface and the image surface is 0.12 mm.

6. The six-group and seven-element micro-immersion objective lens according to claim 2, characterized in that, The S11 surface of the first lens is a plane, the full aperture for light transmission is 0.37 mm, the curvature radius of the S12 surface is -1.25 mm, the full aperture for light transmission is 1.56 mm. The refractive index of the material of the first lens is 1.88 and the Abbe number is 39.

2. The central thickness of the first lens is 1.54 mm, and the central thickness between the adjacent two surfaces of the first lens and the second lens is 0.10 mm; The curvature radius of the S21 surface of the second lens is 4.46 mm, the full aperture for light transmission is 1.76 mm, the curvature radius of the S22 surface is -4.46 mm, the full aperture for light transmission is 1.79 mm. The refractive index of the material of the second lens is 1.79 and the Abbe number is 54.

7. The central thickness of the second lens is 0.54 mm, and the central thickness between the adjacent two surfaces of the second lens and the third lens is 0.10 mm; The curvature radius of the surface S31 of the third lens is 4.58 mm, the full aperture of light transmission is 1.74 mm, the curvature radius of the surface S32 is 1.25 mm, the full aperture of light transmission is 1.61 mm, the curvature radius of the surface S33 is -9.84 mm, the full aperture of light transmission is 1.62 mm. The third lens is composed of two lenses glued together in sequence from the object surface to the image surface. The refractive index of the material of one lens is 1.78 and the Abbe number is 25.7, and the refractive index of the material of the other lens is 1.73 and the Abbe number is 54.

7. The central thicknesses of the two lenses are 0.40 mm and 0.72 mm in sequence. The central thickness between the adjacent two surfaces of the third lens and the fourth lens is 0.10 mm; The curvature radius of the surface S41 of the fourth lens is 1.43 mm, the full aperture of light transmission is 1.62 mm, the curvature radius of the surface S42 is 2.21 mm, the full aperture of light transmission is 1.27 mm. The refractive index of the material of the fourth lens is 1.73 and the Abbe number is 54.

7. The central thickness of the fourth lens is 0.80 mm, and the central thickness between the adjacent two surfaces of the fourth lens and the fifth lens is 0.25 mm; The curvature radius of the surface S51 of the fifth lens is -3.54 mm, the full aperture of light transmission is 1.21 mm, the curvature radius of the surface S52 is 1.25 mm, the full aperture of light transmission is 1.14 mm. The refractive index of the material of the fifth lens is 1.78 and the Abbe number is 25.

7. The central thickness of the fifth lens is 0.40 mm, and the central thickness between the adjacent two surfaces of the fifth lens and the sixth lens is 0.48 mm; The curvature radius of the surface S61 of the sixth lens is 0.94 mm, the full aperture of light transmission is 1.62 mm, the surface S62 is a plane, the full aperture of light transmission is 1.03 mm. The refractive index of the material of the sixth lens is 1.81 and the Abbe number is 41.

0. The central thickness of the sixth lens is 1.69 mm, and the central thickness between the surface S62 and the image surface is 0.40 mm.

Images