Endoscope objective lens

Abstract

The endoscope objective lens sequentially comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens from an object side to an image side along an optical axis, the second lens has negative focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface; the third lens has positive focal power, the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a convex surface; a liquid zoom lens; the fourth lens has positive focal power, the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; the fifth lens has negative focal power, and the object side surface of the fifth lens is a concave surface; the sixth lens has positive focal power, the object side surface of the sixth lens is a convex surface, and the image side surface of the sixth lens is a convex surface; the seventh lens has negative focal power; the objective lens of the endoscope meets the condition that (CT1 + CT3) / SAG72 is larger than or equal to 2 and smaller than or equal to 3.5.

Description

Technical Field

[0001] This invention relates to the field of optical elements, and more specifically, to an endoscope objective. Background Technology

[0002] Endoscopes are an essential tool in modern medical diagnosis, and their imaging quality has a significant impact on surgical quality. In recent years, with the increasing demand for high-definition imaging, low-light performance, and NIR / SWIR band imaging in minimally invasive surgery, traditional miniaturized objectives still have shortcomings in terms of light throughput, image quality stability, and manufacturing consistency. Furthermore, to meet surgical needs, endoscopes often need to be adaptable to different working distances, thus requiring zoom functionality. Traditional endoscopes typically achieve zooming through mechanical structures. Limited by the probe diameter, mechanical zoom components (such as moving lens groups) not only struggle to achieve efficient focal length adjustment but also increase system complexity, power consumption, and reliability risks, further limiting the miniaturization of endoscopes and the improvement of imaging quality. Summary of the Invention

[0003] To address the challenge of balancing miniaturization and image quality when adjusting the focal length of existing endoscopes, an endoscope objective lens is provided.

[0004] This invention provides an endoscope objective lens, which, along the optical axis from the object side to the image side, sequentially comprises: a first lens having optical power; a second lens having negative optical power, wherein the object side of the second lens is convex and the image side of the second lens is concave; a third lens having positive optical power, wherein both the object side and the image side of the third lens are convex; a liquid zoom lens; a fourth lens having positive optical power, wherein both the object side and the image side of the fourth lens are convex; a fifth lens having negative optical power, wherein the object side of the fifth lens is concave; a sixth lens having positive optical power, wherein both the object side and the image side of the sixth lens are convex; and a seventh lens having negative optical power.

[0005] The endoscope objective lens satisfies: 2≤(CT1+CT3) / SAG72≤3.5; where CT1 is the center thickness of the first lens, CT3 is the center thickness of the third lens, and SAG72 is the sagitta of the image-side surface of the seventh lens.

[0006] The beneficial effects of this invention are as follows:

[0007] The endoscope objective of this invention uses a seven-lens architecture and achieves zoom by introducing a liquid zoom lens between the third and fourth lenses, avoiding the use of a mechanical zoom structure, thereby contributing to miniaturization.

[0008] This seven-lens architecture not only allows the objective distance of the endoscope to cover a range of at least 15mm-1000mm, but also maintains high image quality throughout the focal length variation process, meeting the needs of endoscope use during surgery. By controlling the endoscope objective to meet the condition 2≤(CT1+CT3) / SAG72≤3.5, the diameter of the endoscope objective can also be effectively controlled, thereby further meeting the miniaturization requirements. Attached Figure Description

[0009] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0010] Figure 1 This is a schematic diagram of the endoscope objective lens in Embodiment 1 of the present invention;

[0011] Figure 1a This is the MTF curve of the endoscope objective lens in Embodiment 1 of the present invention at an object distance of 50 mm;

[0012] Figure 1b This is an axial spherical aberration curve of the endoscope objective lens in Embodiment 1 of the present invention when the object distance is 50 mm;

[0013] Figure 1c This is the astigmatism curve of the endoscope objective lens in Embodiment 1 of the present invention at an object distance of 50 mm;

[0014] Figure 1d This is a distortion diagram of the endoscope objective lens in Embodiment 1 of the present invention at an object distance of 50 mm;

[0015] Figure 1e This is the MTF curve of the endoscope objective lens in Embodiment 1 of the present invention when the object distance is 15mm;

[0016] Figure 1f This is the MTF curve of the endoscope objective lens in Embodiment 1 of the present invention at an object distance of 1000mm;

[0017] Figure 2 This is a schematic diagram of the endoscope objective lens in Embodiment 2 of the present invention;

[0018] Figure 2a This is the MTF curve of the endoscope objective lens in Embodiment 2 of the present invention at an object distance of 50 mm;

[0019] Figure 2b This is an axial spherical aberration curve of the endoscope objective lens in Embodiment 2 of the present invention when the object distance is 50 mm;

[0020] Figure 2c This is the astigmatism curve of the endoscope objective lens in Embodiment 2 of the present invention at an object distance of 50 mm;

[0021] Figure 2d This is a distortion diagram of the endoscope objective lens in Embodiment 2 of the present invention at an object distance of 50 mm;

[0022] Figure 2e This is the MTF curve of the endoscope objective lens in Embodiment 2 of the present invention when the object distance is 15mm;

[0023] Figure 2f This is the MTF curve of the endoscope objective lens in Embodiment 2 of the present invention at an object distance of 1000mm;

[0024] Figure 3 This is a schematic diagram of the endoscope objective lens in Embodiment 3 of the present invention;

[0025] Figure 3a This is the MTF curve of the endoscope objective lens in Embodiment 3 of the present invention at an object distance of 50 mm;

[0026] Figure 3b This is an axial spherical aberration curve of the endoscope objective lens in Embodiment 3 of the present invention when the object distance is 50 mm;

[0027] Figure 3c This is the astigmatism curve of the endoscope objective lens in Embodiment 3 of the present invention at an object distance of 50 mm;

[0028] Figure 3d This is a distortion diagram of the endoscope objective lens in Embodiment 3 of the present invention at an object distance of 50 mm;

[0029] Figure 3e This is the MTF curve of the endoscope objective lens in Embodiment 3 of the present invention when the object distance is 15mm;

[0030] Figure 3f This is the MTF curve of the endoscope objective lens in Embodiment 3 of the present invention at an object distance of 1000mm. Detailed Implementation

[0031] To better understand the invention, various aspects of the invention will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of the invention and are not intended to limit the scope of the invention in any way. Throughout the specification, the same reference numerals refer to the same elements.

[0032] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of the invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0033] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not drawn strictly to scale.

[0034] In this paper, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region.

[0035] It should also be understood that the terms "comprising," "including," and / or "having," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when describing embodiments of the invention, the word "may" is used to mean "one or more embodiments of the invention." And the term "exemplary" is intended to refer to an example or illustration.

[0036] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense, unless expressly so defined herein.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] The features, principles and other aspects of the present invention will be described in detail below.

[0039] According to an exemplary embodiment of the present invention, an endoscope objective lens sequentially includes, along the optical axis from the object side to the image side, a first lens having optical power, a second lens having negative optical power, a third lens having positive optical power, a liquid zoom lens, a fourth lens having positive optical power, a fifth lens having negative optical power, a sixth lens having positive optical power, and a seventh lens having negative optical power.

[0040] The second lens has a convex object-side surface and a concave image-side surface; the third lens has a convex object-side surface and a convex image-side surface; the fourth lens has a convex object-side surface and a convex image-side surface; the fifth lens has a concave object-side surface; and the sixth lens has a convex object-side surface and a convex image-side surface.

[0041] The endoscope objective lens satisfies: 2≤(CT1+CT3) / SAG72≤3.5; where CT1 is the center thickness of the first lens, CT3 is the center thickness of the third lens, and SAG72 is the sagitta of the image-side surface of the seventh lens.

[0042] According to an exemplary embodiment of the present invention, the endoscope objective lens, in a seven-lens architecture, achieves zoom by introducing a liquid zoom lens between the third and fourth lenses, avoiding the use of a mechanical zoom structure, thereby contributing to miniaturization.

[0043] This seven-lens architecture not only allows the objective distance of the endoscope to cover a range of at least 15mm-1000mm, but also maintains high image quality throughout the focal length variation process, meeting the needs of endoscope use during surgery. By controlling the endoscope objective to meet the condition 2≤(CT1+CT3) / SAG72≤3.5, the diameter of the endoscope objective can also be effectively controlled, thereby further meeting the miniaturization requirements.

[0044] In some embodiments, the aperture stop is located between the third lens and the liquid zoom lens. This helps to reduce the aperture of the liquid zoom lens, facilitating the miniaturization of the endoscope objective.

[0045] In some embodiments, the first lens has a positive optical power, the object side of the first lens is a plane, and the image side of the first lens is a convex surface.

[0046] In some embodiments, the first lens has a negative optical power, the object side of the first lens is convex, and the image side of the first lens is concave.

[0047] In some embodiments, the image-side surface of the fifth lens is convex.

[0048] In some embodiments, the image-side surface of the fifth lens is concave.

[0049] In some embodiments, the object-side surface of the seventh lens is concave, and the image-side surface of the seventh lens is convex.

[0050] In some embodiments, the object-side surface of the seventh lens is convex, and the image-side surface of the seventh lens is concave.

[0051] In some embodiments, the object-side surface of the seventh lens is concave, and the image-side surface of the seventh lens is also concave.

[0052] In some embodiments, the fourth lens and the fifth lens are cemented together.

[0053] In some embodiments, the endoscope objective lens satisfies: SAG11 / SAG72 ≤ 1.5. Here, SAG11 is the sagitta of the object-side surface of the first lens, and SAG72 is the sagitta of the image-side surface of the seventh lens. By controlling SAG11 and SAG72, the manufacturability of the lens can be effectively controlled, which is beneficial for lens assembly.

[0054] In some embodiments, the endoscope objective lens satisfies: 0.5 ≤ (f2 + f6) / f ≤ 1.5. Here, f2 is the focal length of the second lens, f6 is the focal length of the sixth lens, and f is the focal length of the endoscope objective lens. This design can mitigate the deflection angle of light at the second and sixth lenses, effectively reducing the height of peripheral rays, facilitating miniaturization and reducing aberrations.

[0055] In some embodiments, the endoscope objective lens satisfies: 0.35 ≤ (T12 + T23) / (T56 + T67) ≤ 5.5. Wherein, T12 is the distance on the optical axis between the image-side surface of the first lens and the object-side surface of the second lens, T23 is the distance on the optical axis between the image-side surface of the second lens and the object-side surface of the third lens, T56 is the distance on the optical axis between the image-side surface of the fifth lens and the object-side surface of the sixth lens, and T67 is the distance on the optical axis between the image-side surface of the sixth lens and the object-side surface of the seventh lens. This design effectively reduces the lens's thickness sensitivity and facilitates field curvature correction.

[0056] In some embodiments, the endoscope objective lens satisfies: -8 ≤ (R11 + R14) / R12 ≤ -2. Wherein, R11 is the central radius of curvature of the object-side surface of the sixth lens, R14 is the central radius of curvature of the image-side surface of the seventh lens, and R12 is the central radius of curvature of the image-side surface of the sixth lens. This design facilitates matching the principal ray angle (CRA) of the endoscope objective lens, corrects the field curvature of the endoscope objective lens, and meets the imaging clarity requirements of various fields of view.

[0057] In some embodiments, the endoscope objective lens satisfies the following conditions: 0.35mm / V ≤ d0 / U ≤ 24mm / V and -3.8 ≤ d0 × φ0 ≤ 0.15; where d0 is the object distance of the endoscope objective lens, U is the driving voltage applied to the liquid zoom lens, and φ0 is the optical power of the liquid zoom lens. This not only allows the endoscope objective lens to achieve a large range of object distance variation but also ensures image quality during zooming.

[0058] In some embodiments, the endoscope objective lens satisfies the following condition: 1.5 ≤ ImgH / D ≤ 2.5. Where ImgH is half the diagonal length of the effective pixel area on the image plane, and D is the aperture diameter of the diaphragm. This design allows for a larger image plane while providing sufficient illumination for the system, thereby increasing the field of view and enhancing the optical system's ability to collect object-side information. This enables the system to obtain high-resolution, clear images at object distances ranging from 15mm to 1000mm.

[0059] Example 1:

[0060] like Figure 1 As shown, the endoscope objective lens in this embodiment includes, in sequence along the optical axis from the object side to the image side, a first lens L1 with positive optical power, a second lens L2 with negative optical power, a third lens L3 with positive optical power, an aperture stop STO, a liquid zoom lens E1, a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, a sixth lens L6 with positive optical power, and a seventh lens L7 with negative optical power.

[0061] The object-side surface S1 of the first lens L1 is a plane, and the image-side surface S2 of the first lens L1 is a convex surface.

[0062] The object-side surface S3 of the second lens L2 is convex, and the image-side surface S4 of the second lens L2 is concave.

[0063] The object-side surface S5 of the third lens L3 is convex, and the image-side surface S6 of the third lens L3 is convex.

[0064] The object-side surface S7 of the fourth lens L4 is convex, and the image-side surface S8 of the fourth lens L4 is convex.

[0065] The object-side surface S8 of the fifth lens L5 is concave, and the image-side surface S9 of the fifth lens L5 is convex.

[0066] The object-side surface S10 of the sixth lens L6 is convex, and the image-side surface S11 of the sixth lens L6 is convex.

[0067] The object-side surface S12 of the seventh lens L7 is concave, and the image-side surface S13 of the seventh lens L7 is convex.

[0068] Among them, the image side S8 of the fourth lens L4 and the object side S8 of the fifth lens L5 are cemented together.

[0069] Table 1 shows the optical parameters of the endoscope objective in Example 1.

[0070] Table 1

[0071]

[0072] In this embodiment, when d0=50mm, the radius of curvature corresponding to E1 is infinite; when d0=15mm, the radius of curvature corresponding to E1 is -8mm; when d0=150mm, the radius of curvature corresponding to E1 is 23.36mm; and when d0=1000mm, the radius of curvature corresponding to E1 is 15.8mm.

[0073] The above-mentioned aspherical surfaces S3-S13 can be limited by, but are not limited to, the following aspherical surface formulas:

[0074] ;

[0075] Where x is the distance vector from the vertex of the aspherical surface at a height h along the optical axis; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic coefficient; Ai is the i-th order correction coefficient of the aspherical surface. Table 2 gives the conic coefficient k and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, and A18 that can be used for each aspherical surface S3-S13 in Example 1.

[0076] Table 2

[0077]

[0078] like Figures 1a-1f As shown, the endoscope objective lens in this embodiment has high imaging quality when the object distance is in the range of 15mm-1000mm.

[0079] Example 2:

[0080] like Figure 2 As shown, the endoscope objective lens in this embodiment includes, in sequence along the optical axis from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with negative optical power, a third lens L3 with positive optical power, an aperture stop STO, a liquid zoom lens E1, a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, a sixth lens L6 with positive optical power, and a seventh lens L7 with negative optical power.

[0081] The object-side surface S1 of the first lens L1 is convex, and the image-side surface S2 of the first lens L1 is concave.

[0082] The object-side surface S3 of the second lens L2 is convex, and the image-side surface S4 of the second lens L2 is concave.

[0083] The object-side surface S5 of the third lens L3 is convex, and the image-side surface S6 of the third lens L3 is convex.

[0084] The object-side surface S7 of the fourth lens L4 is convex, and the image-side surface S8 of the fourth lens L4 is convex.

[0085] The object-side surface S9 of the fifth lens L5 is concave, and the image-side surface S10 of the fifth lens L5 is concave.

[0086] The object-side surface S11 of the sixth lens L6 is convex, and the image-side surface S12 of the sixth lens L6 is convex.

[0087] The object-side surface S13 of the seventh lens L7 is convex, and the image-side surface S14 of the seventh lens L7 is concave.

[0088] Table 3 shows the optical parameters of the endoscope objective in Example 2.

[0089] Table 3

[0090]

[0091] In this embodiment, when d0=50mm, the radius of curvature corresponding to E1 is infinite; when d0=15mm, the radius of curvature corresponding to E1 is -9.235mm; when d0=150mm, the radius of curvature corresponding to E1 is 27.99mm; and when d0=1000mm, the radius of curvature corresponding to E1 is 19.22mm.

[0092] The aforementioned aspherical surfaces S1-S14 can be defined using the aspherical surface formula in Example 1. Table 4 shows the conic coefficient k and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, and A18 that can be used for the aspherical surfaces S1-S14 in Example 2.

[0093] Table 4

[0094]

[0095] like Figures 2a-2f As shown, the endoscope objective lens in this embodiment has high imaging quality when the object distance is in the range of 15mm-1000mm.

[0096] Example 3:

[0097] like Figure 3 As shown, the endoscope objective lens in this embodiment includes, in sequence along the optical axis from the object side to the image side, a first lens L1 with positive optical power, a second lens L2 with negative optical power, a third lens L3 with positive optical power, an aperture stop STO, a liquid zoom lens E1, a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, a sixth lens L6 with positive optical power, and a seventh lens L7 with negative optical power.

[0098] The object-side surface S1 of the first lens L1 is a plane, and the image-side surface S2 of the first lens L1 is a convex surface.

[0099] The object-side surface S3 of the second lens L2 is convex, and the image-side surface S4 of the second lens L2 is concave.

[0100] The object-side surface S5 of the third lens L3 is convex, and the image-side surface S6 of the third lens L3 is convex.

[0101] The object-side surface S7 of the fourth lens L4 is convex, and the image-side surface S8 of the fourth lens L4 is convex.

[0102] The object-side surface S8 of the fifth lens L5 is concave, and the image-side surface S9 of the fifth lens L5 is convex.

[0103] The object-side surface S10 of the sixth lens L6 is convex, and the image-side surface S11 of the sixth lens L6 is convex.

[0104] The object-side surface S12 of the seventh lens L7 is concave, and the image-side surface S13 of the seventh lens L7 is also concave.

[0105] Among them, the image side S8 of the fourth lens L4 and the object side S8 of the fifth lens L5 are cemented together.

[0106] Table 5 shows the optical parameters of the endoscope objective in Example 3.

[0107] Table 5

[0108]

[0109] In this embodiment, when d0=50mm, the radius of curvature corresponding to E1 is infinite; when d0=15mm, the radius of curvature corresponding to E1 is -8.34mm; when d0=150mm, the radius of curvature corresponding to E1 is 26.2mm; and when d0=1000mm, the radius of curvature corresponding to E1 is 17.71mm.

[0110] The aforementioned aspherical surfaces S3-S13 can be defined using the aspherical surface formula in Example 1. Table 6 provides the conic coefficient k and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, and A18 that can be used for the aspherical surfaces S3-S13 in Example 3.

[0111] Table 6

[0112]

[0113] like Figures 3a-3f As shown, the endoscope objective lens in this embodiment has high imaging quality when the object distance is in the range of 15mm-1000mm.

[0114] The optical parameters in Examples 1-3 are further shown in Table 7, where the unit of each parameter is mm.

[0115] Table 7

[0116]

[0117] The conditional expressions of each embodiment in Examples 1-3 satisfy Table 8.

[0118] Table 8

[0119]

[0120] Table 9 shows the correspondence between the object distance d0 of the endoscope objective lens, the driving voltage U applied to the liquid zoom lens, the optical power φ0 of the liquid zoom lens, d0 / U, and d0×φ0 in Examples 1-3. The units of d0 are mm, U is V, and φ0 is mm. -1 The unit of d0 / U is mm / V, and d0×φ0 is dimensionless.

[0121] Table 9

[0122]

[0123] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention is not limited to the specific combination of the above-described technical features, but also includes other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this invention.

Claims

1. An endoscope objective, characterized in that, Along the optical axis from the object side to the image side, the following are included in sequence: A first lens with optical power; A second lens with negative optical power, wherein the object side of the second lens is convex and the image side of the second lens is concave; A third lens with positive optical power, wherein the object-side surface of the third lens is convex and the image-side surface of the third lens is convex; Liquid zoom lens; A fourth lens with positive optical power, wherein the object-side surface of the fourth lens is convex and the image-side surface of the fourth lens is convex. A fifth lens with negative optical power, wherein the object side of the fifth lens is concave; A sixth lens with positive optical power, wherein the object-side surface of the sixth lens is convex and the image-side surface of the sixth lens is convex; A seventh lens with negative optical power; The endoscope objective lens satisfies: 2≤(CT1+CT3) / SAG72≤3.5; where CT1 is the center thickness of the first lens, CT3 is the center thickness of the third lens, and SAG72 is the sagitta of the image-side surface of the seventh lens.

2. The endoscope objective according to claim 1, characterized in that, The aperture stop is located between the third lens and the liquid zoom lens.

3. The endoscope objective according to claim 1, characterized in that, The first lens has a positive optical power, a flat object-side surface, and a convex image-side surface; or, the first lens has a negative optical power, a convex object-side surface, and a concave image-side surface; and / or... The image-side surface of the fifth lens is convex, or the image-side surface of the fifth lens is concave; and / or, The object-side surface of the seventh lens is concave, and the image-side surface of the seventh lens is convex; or, the object-side surface of the seventh lens is convex, and the image-side surface of the seventh lens is concave; or, the object-side surface of the seventh lens is concave, and the image-side surface of the seventh lens is concave.

4. The endoscope objective according to claim 1, characterized in that, The fourth lens and the fifth lens are cemented together.

5. The endoscope objective according to any one of claims 1-4, characterized in that, The endoscope objective lens satisfies: SAG11 / SAG72≤1.5; where SAG11 is the sagitta of the object-side surface of the first lens, and SAG72 is the sagitta of the image-side surface of the seventh lens.

6. The endoscope objective according to any one of claims 1-4, characterized in that, The endoscope objective lens satisfies: 0.5≤(f2+f6) / f≤1.5; where f2 is the focal length of the second lens, f6 is the focal length of the sixth lens, and f is the focal length of the endoscope objective lens.

7. The endoscope objective according to any one of claims 1-4, characterized in that, The endoscope objective lens satisfies: 0.35≤(T12+T23) / (T56+T67)≤5.5; where T12 is the distance on the optical axis between the image-side surface of the first lens and the object-side surface of the second lens, T23 is the distance on the optical axis between the image-side surface of the second lens and the object-side surface of the third lens, T56 is the distance on the optical axis between the image-side surface of the fifth lens and the object-side surface of the sixth lens, and T67 is the distance on the optical axis between the image-side surface of the sixth lens and the object-side surface of the seventh lens.

8. The endoscope objective according to any one of claims 1-4, characterized in that, The endoscope objective lens satisfies: -8≤(R11+R14) / R12≤-2; where R11 is the central radius of curvature of the object side of the sixth lens, R14 is the central radius of curvature of the image side of the seventh lens, and R12 is the central radius of curvature of the image side of the sixth lens.

9. The endoscope objective according to any one of claims 1-4, characterized in that, The endoscope objective lens satisfies the following conditions: 0.35mm / V≤d0 / U≤24mm / V and -3.8≤d0×φ0≤0.15; where d0 is the object distance of the endoscope objective lens, U is the driving voltage applied to the liquid zoom lens, and φ0 is the optical power of the liquid zoom lens.

10. The endoscope objective according to any one of claims 1-4, characterized in that, The endoscope objective lens satisfies the following condition: 1.5≤ImgH / D≤2.5; where ImgH is half the diagonal length of the effective pixel area on the image plane, and D is the aperture diameter.

Images