Endoscope and endoscope objective lens

Abstract

The present invention relates to the technical field of endoscopes, and in particular to an endoscope objective lens. In an optical system of the endoscope objective lens, a first lens, a second lens, a diaphragm, a third lens and a fourth lens are sequentially arranged from an image side to an object side along an optical axis, wherein the first lens and the fourth lens have negative focal power, the second lens and the third lens have positive focal power, the height h11 of chief rays on the object-side surface of the first lens and the height h42 of chief rays on the image-side surface of the fourth lens satisfy: 0.65≤h11 / h42≤1.35, and / or the effective optical diameter D11 of the object-side surface of the first lens and the effective optical diameter D42 of the image-side surface of the fourth lens satisfy: 0.75≤D11 / D42≤1.25, so that the first lens and the fourth lens can be approximately symmetrical, and paths through which light passes in the two lenses which are approximately symmetrical can also be approximately symmetrical, so that part of aberrations can be mutually offset, thereby reducing the difficulty of aberration correction, and reducing the sensitivity to tolerances on optical surfaces.

Description

Endoscope and endoscope objective lens Technical Field

[0001] The present invention relates to the technical field of endoscopes, and in particular to an objective lens of an endoscope. Background Art

[0002] Endoscopes, with their small size and direct imaging capabilities, are now widely used across various industries. Endoscopes can be inserted into the patient's body without or with minimal invasion, allowing for accurate diagnosis or treatment by viewing endoscopic images.

[0003] Since the natural openings of various parts of the human body are relatively small, even invasive openings need to be as small as possible. Therefore, endoscopes have strict size restrictions, especially for endoscopes used to observe the digestive tract, liver and gallbladder organs, bronchi, ears, nose and throat, urinary organs and uterus.

[0004] The diameter of the endoscope cannot be too large, and the corresponding size of the objective optical system at the front end of the endoscope cannot be too large either. When observing narrow, curved, strip-like organs such as the bladder and ureters, the insertion portion is usually bent more than 90 degrees to observe the organs. In this case, when the length of the objective optical system is shorter, the length from the front end of the endoscope to the curved portion can be shortened, and the endoscope can observe a wider range in the bag-like organs. The objective optical system of the endoscope not only needs to be small in size to enable the size of the front end of the endoscope to be smaller, but also the objective optical system of the endoscope is a wide-angle objective optical system, and the field of view angle of the endoscope objective is generally greater than or equal to 120 degrees. Due to the large field of view angle, the off-axis aberration of the field light at the edge of the endoscope objective is more difficult to correct, and the surface shape and position tolerance sensitivity of the optical elements in the objective lens are relatively large.

[0005] Summary of the Invention

[0006] The object of the present invention is to provide an endoscope objective lens for improving the problem of difficulty in correcting aberrations of current endoscope objective lenses.

[0007] Another object of the present invention is to provide an endoscope using the above-mentioned endoscope objective lens.

[0008] According to a first aspect, an embodiment provides an endoscope objective lens, including an objective optical system, wherein the objective optical system includes:

[0009] a first lens having negative optical power, wherein a portion of an image-side surface of the first lens close to the optical axis and away from an edge of the first lens is concave;

[0010] a second lens having positive optical power;

[0011] Aperture;

[0012] a third lens having positive optical power;

[0013] a fourth lens having negative optical power, wherein a portion of the object-side surface of the fourth lens close to the optical axis and away from an edge of the fourth lens is concave;

[0014] The first lens, the second lens, the aperture, the third lens and the fourth lens are arranged in sequence from the image side to the object side along the optical axis;

[0015] A chief ray height h11 on the object-side surface of the first lens and a chief ray height h42 on the image-side surface of the fourth lens satisfy: 0.65≤h11 / h42≤1.35, and / or an effective optical diameter D11 on the object-side surface of the first lens and an effective optical diameter D42 on the image-side surface of the fourth lens satisfy: 0.75≤D11 / D42≤1.25.

[0016] Furthermore, in one embodiment, the height h11 of the chief ray on the object-side surface of the first lens and the height h42 of the chief ray on the image-side surface of the fourth lens satisfy: 0.8≤h11 / h42≤1.2.

[0017] Furthermore, in one embodiment, the effective optical diameter D11 of the object side surface of the first lens and the effective optical diameter D42 of the image side surface of the fourth lens satisfy: 0.85≤D11 / D42≤1.15

[0018] Furthermore, in one embodiment, an effective optical diameter D11 of the object-side surface of the first lens and an imaging height imgH of the objective optical system satisfy: 0.8≤D11 / imgH≤1.42.

[0019] Furthermore, in one embodiment, an effective optical diameter D11 of the object-side surface of the first lens and an imaging height imgH of the objective optical system satisfy: 1.00≤D11 / imgH≤1.40.

[0020] Furthermore, in one embodiment, the chief ray heights of the two surface edge fields of view of the first lens are h11 and h12, respectively, the average of h11 and h12 is H1, the focal length of the first lens is f1, the chief ray heights of the two surface edge fields of view of the fourth lens are h41 and h42, respectively, the average of h41 and h42 is H4, and the focal length of the fourth lens is f4, then the objective optical system satisfies: 1≤(H1 / f1) / (H4 / f4)≤2.

[0021] Furthermore, in one embodiment, the combined focal length of the second lens and the third lens as a group of lenses is F23, and the focal length of the objective optical system is f, then the objective optical system satisfies: 0.7≤F23 / f≤1.2.

[0022] Furthermore, in one embodiment, the object-side surface of the second lens is a convex surface; and the image-side surface of the third lens is a convex surface.

[0023] Furthermore, in one embodiment, the number of lenses with optical power in the objective optical system is four.

[0024] According to a second aspect, an embodiment provides an endoscope, comprising an endoscope objective lens as described in any embodiment of the first aspect.

[0025] According to the endoscope objective lens of the above embodiment, in the optical system of the endoscope objective lens, the first lens, the second lens, the aperture, the third lens and the fourth lens are arranged in sequence from the image side to the object side along the optical axis, and the first lens and the fourth lens have negative optical power, a portion of the image side surface of the first lens close to the optical axis and away from the edge of the first lens is a concave surface, a portion of the object side surface of the fourth lens close to the optical axis and away from the edge of the fourth lens is a concave surface, the second lens and the third lens have positive optical power, and a chief ray height h11 on the object side surface of the first lens and a chief ray height h42 on the image side surface of the fourth lens satisfy: 0.65≤ h11 / h42≤1.35, and / or the effective optical diameter D11 of the object-side surface of the first lens and the effective optical diameter D42 of the image-side surface of the fourth lens satisfy the following: 0.75≤D11 / D42≤1.25, so that the aperture in the objective optical system is located between the second lens and the third lens, and the positive and negative relationships of the focal powers of the lenses located at symmetrical positions on either side of the aperture are symmetrical; in addition, the object-side surface of the first lens and the image-side surface of the fourth lens are approximately symmetrical in shape; and the positions of light rays passing through the optical surfaces of the two approximately symmetrical lenses, particularly the first lens and the fourth lens, are approximately symmetrical. The above-mentioned approximately symmetrical characteristics can give the entire optical system a certain degree of symmetry. By using the characteristic that the signs of some aberrations generated by the imaging light rays passing through the approximately symmetrical surfaces in the optical system are opposite, some aberrations can be offset, thereby reducing the difficulty of aberration correction and improving imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic structural diagram of an objective optical system in a first embodiment;

[0027] FIG2 is a graph showing the imaging diffraction MTF when the objective optical system in FIG1 is used;

[0028] FIG3 is a schematic structural diagram of an objective optical system in a second embodiment;

[0029] FIG4 is a graph showing the imaging diffraction MTF when the objective optical system in FIG3 is used;

[0030] FIG5 is a schematic structural diagram of an objective optical system in a third embodiment;

[0031] FIG6 is a graph showing the imaging diffraction MTF when the objective optical system in FIG5 is used;

[0032] FIG7 is a schematic structural diagram of an objective optical system in a fourth embodiment;

[0033] FIG8 is a graph showing the imaging diffraction MTF when the objective optical system in FIG7 is used;

[0034] FIG9 is a schematic structural diagram of an objective optical system in a fifth embodiment;

[0035] FIG10 is a graph showing the imaging diffraction MTF when the objective optical system in FIG9 is used;

[0036] FIG11 is a schematic structural diagram of an objective optical system in a sixth embodiment;

[0037] FIG12 is a graph showing the imaging diffraction MTF when the objective optical system in FIG11 is used;

[0038] FIG13 is a schematic structural diagram of an objective optical system in a seventh embodiment;

[0039] FIG14 is a graph showing the imaging diffraction MTF when the objective optical system in FIG13 is used;

[0040] FIG15 is a schematic structural diagram of an objective optical system in an eighth embodiment;

[0041] FIG16 is a graph showing the imaging diffraction MTF when the objective optical system in FIG15 is used;

[0042] FIG17 is a schematic structural diagram of an objective optical system in a ninth embodiment;

[0043] FIG18 is a graph showing the imaging diffraction MTF when the objective optical system in FIG17 is used.

[0044] List of feature names corresponding to the figure marks in the figure: 1. First lens; 11. Object side surface; 12. Image side surface; 2. Second lens; 21. Object side surface; 22. Image side surface; 3. Third lens; 31. Object side surface; 32. Image side surface; 4. Fourth lens; 41. Object side surface; 42. Image side surface; 5. Aperture; 6. Filter; 61. Object side surface; 62. Image side surface; 7. Image sensor glass; 71. Object side surface; 72. Image side surface. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below by means of specific embodiments in conjunction with the accompanying drawings. Similar elements in different embodiments are numbered with associated similar elements. In the following embodiments, many detailed descriptions are provided to enable the present application to be better understood. However, those skilled in the art will readily appreciate that some of the features may be omitted in different circumstances, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification. This is to avoid the core portion of the present application being overwhelmed by excessive descriptions, and for those skilled in the art, it is not necessary to describe these related operations in detail. They will fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0046] In addition, the features, operations, or characteristics described in the specification may be combined in any appropriate manner to form various embodiments. Furthermore, the steps or actions in the method description may be reordered or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various sequences in the specification and drawings are provided solely for the purpose of clearly describing a particular embodiment and are not intended to be mandatory, unless otherwise specified.

[0047] The serial numbers assigned to components herein, such as "first," "second," etc., are used solely to distinguish the objects being described and do not convey any sequential or technical meaning. References to "connection" and "coupling" herein, unless otherwise specified, include both direct and indirect connections (couplings).

[0048] The field of view angle of an endoscope objective lens is generally greater than or equal to 120 degrees, so the objective optical system of an endoscope is a wide-angle objective optical system. Due to the large field of view angle, the off-axis aberrations caused by the marginal light rays of the endoscope objective lens are difficult to correct. To address this problem, the present application provides an endoscope objective optical system with a nearly symmetrical structure. Through the nearly symmetric optical surfaces and the positions of light rays on the optical surfaces, some aberrations can be offset. Therefore, this structure is beneficial for aberration correction, especially for coma, distortion, and lateral chromatic aberration. The following is a detailed introduction to the structure of the endoscope objective lens.

[0049] In some embodiments, please refer to Figures 1 to 16, the endoscope objective includes an objective optical system, the objective optical system includes a first lens 1, a second lens 2, an aperture, a third lens 3 and a fourth lens 4, and the first lens 1, the second lens 2, the aperture, the third lens 3 and the fourth lens 4 are arranged in sequence from the image side to the object side along the optical axis of the objective optical system.

[0050] In some embodiments, considering the need for low cost, the number of lenses with optical power in the objective optical system is four, and the aperture is located in the middle of the four lenses to make the objective structure approximately symmetrical.

[0051] In some embodiments, for a wide-angle objective lens, in order to increase the angle of the optical principal ray at its edge, the first lens 1 has a negative optical power. Specifically, the image-side surface 12 of the first lens 1 close to the optical axis of the objective optical system and away from the edge of the first lens 1 is concave.

[0052] The first lens 1 can adopt any feasible lens shape. For example, in one embodiment, the first lens 1 is a meniscus lens. In another embodiment, the first lens 1 is a plano-concave lens, whose object-side surface 11 is a flat surface and the image-side surface 12 is a concave surface.

[0053] In some embodiments, based on a similar symmetrical structure, the fourth lens 4 of the objective optical system is approximately symmetrical with the first lens 1, the fourth lens 4 also has negative optical power, and the object side surface 41 of the fourth lens 4 is close to the optical axis of the objective optical system and away from the edge of the fourth lens 4 is concave.

[0054] Specifically, in some embodiments, the fourth lens 4 is a meniscus lens, and the object-side surface 41 thereof is a concave surface.

[0055] In some embodiments, the first lens element 1 and the fourth lens element 4 both have negative optical power, and the second lens element 2 and the third lens element 3 both have positive optical power. This provides the entire objective optical system with positive optical power for imaging. In one embodiment, the image-side surface 32 of the third lens element 3 is convex.

[0056] In some embodiments, the objective optical system satisfies at least one of the following two conditions:

[0057] Condition 1: The height h11 of the chief ray on the object-side surface 11 of the first lens element 1 and the height h42 of the chief ray on the image-side surface 42 of the fourth lens element 4 satisfy the following relationship: 0.65≤h11 / h42≤1.35.

[0058] Condition 2: an effective optical diameter D11 of the object-side surface 11 of the first lens element 1 and an effective optical diameter D42 of the image-side surface 42 of the fourth lens element 4 satisfy the following relationship: 0.75≤D11 / D42≤1.25.

[0059] The objective optical system satisfies conditions 1 and / or 2, thus ensuring approximately symmetrical heights for light rays passing through the first lens element 1 and the fourth lens element 4. This facilitates correction of aberrations and reduces sensitivity to optical surface tolerances. The principal ray of the marginal field of view is positioned approximately at the same height on the object-side surface 11 of the first lens element 1 as on the image-side surface 42 of the fourth lens element 4, ensuring approximately symmetrical heights for the light rays. The effective optical diameter of the object-side surface 11 of the first lens element 1 is approximately the same as that of the image-side surface 42 of the fourth lens element 4, further ensuring approximately symmetrical heights for the light rays.

[0060] That is to say, in the objective optical system of the present application, in addition to the approximately symmetrical structures of the first lens 1 and the fourth lens 4, the heights through which the light passes through the first lens 1 and the fourth lens 4 having an approximately symmetrical relationship are also approximately symmetrical.

[0061] It should be noted that, in the present application, the object side of the objective optical system can be understood as the side of the objective optical system facing the object, for example, the side facing the lesion area, and the image side of the objective optical system can be understood as the side on which the imaging surface of the objective optical system is located. Similarly, the image side of the lens is the side of the lens facing the imaging surface of the objective optical system, and the object side is the side of the lens facing the object.

[0062] In some embodiments, parameters are further optimized so that the chief ray height h11 on the object-side surface 11 of the first lens element 1 and the chief ray height h42 on the image-side surface 42 of the fourth lens element 4 satisfy the following relationship: 0.8 ≤ h11 / h42 ≤ 1.2. In some other embodiments, h11 / h42 can satisfy 0.65 ≤ h11 / h42 ≤ 0.85, or can alternatively satisfy 1.2 ≤ h11 / h42 ≤ 1.35.

[0063] In some embodiments, parameters are further optimized so that the effective optical diameter D11 of the object-side surface 11 of the first lens element 1 and the effective optical diameter D42 of the image-side surface 42 of the fourth lens element 4 satisfy the following relationship: 0.85 ≤ D11 / D42 ≤ 1.15. In other embodiments, D11 / D42 may satisfy the following relationship: 0.75 ≤ D11 / D42 ≤ 0.85, or may alternatively satisfy the following relationship: 1.15 ≤ D11 / D42 ≤ 1.25.

[0064] Furthermore, the end of the endoscope head includes components such as the endoscope objective lens, imaging module, lighting element, instrument channel, water vapor channel and structural support element. In general, the size of the endoscope head end and the instrument channel size are preferably determined by clinical needs. The imaging module includes an image sensor, and the size of the image sensor is determined by the clinical needs for image clarity and pixel number, and the remaining space at the head end. The larger the image sensor size, the better the image quality is generally. Therefore, when designing an endoscope, the best practice is that the size of the entire imaging module can be determined by the upper limit of the size of the selected image sensor and its attached circuit board, that is, the diameter of the endoscope objective lens must be less than or equal to the size of the image sensor and its attached circuit board. When the image sensor packaging process and the objective lens structural component process are determined, this means that there is a certain correspondence between the diameter of the endoscope objective lens optical system and the effective photosensitive surface of the image sensor (that is, the image surface size).

[0065] The ratio of the effective optical diameter D11 of the object side surface 11 of the first lens 1 to the imaging height imgH of the optical system is D11 / imgH. If D11 / imgH is too small, the effective optical diameter of the first lens 1 is too small, and the imaging light beam is too concentrated on the first lens 1. Because the optical surface of the objective lens (i.e., the object side surface 11 of the first lens 1) is easily contaminated by foreign objects when the endoscope is used on the human body, objective lens contaminants can affect image quality. When the imaging light beam is too concentrated on the first lens 1, contaminant particles affect more of the imaging light beam, and the contaminants have a significant impact on image quality. At the same time, considering the constraints of h11 / h42 and / or D11 / D42, if D11 / imgH is too small, the maximum effective optical diameter of the fourth lens 4 is also too small. In this case, the light beam is too concentrated on the image side surface 42 of the fourth lens 4, increasing tolerance sensitivity and placing excessively high demands on the surface processing and assembly accuracy of the fourth lens 4. If D11 / imgH is too large, the effective optical diameter of the lens will be too large, and the final diameter of the objective lens will be larger than the packaging size of the image sensor, resulting in a larger module size, which is not conducive to minimizing the diameter direction of the objective lens. In one embodiment, the relationship between the effective optical diameter D11 of the object side surface 11 of the first lens 1 in the objective optical system and the imaging height imgH (i.e., image height) of the optical system satisfies the following conditions: 0.8≤D11 / imgH≤1.42. When D11 / imgH is within this range, the objective optical system is less affected by contaminants and has lower tolerance sensitivity. Furthermore, in one embodiment, 1.00≤D11 / imgH≤1.40. In some other embodiments, depending on the needs of use, without considering the above factors, D11 / imgH can also be less than 0.8 or greater than 1.42.

[0066] Furthermore, in some embodiments, to further optimize the objective lens size and image quality, the principal ray heights at the edges of the two surfaces of the first lens 1 are h11 and h12, respectively, with the average of h11 and h12 being H1. The focal length of the first lens 1 is f1. The principal ray heights at the edges of the two surfaces of the fourth lens 4 are h41 and h42, respectively, with the average of h41 and h42 being H4. The focal length of the fourth lens 4 is f4. In this way, the objective lens optical system satisfies the following: 1 ≤ (H1 / f1) / (H4 / f4) ≤ 2. H1 / f1 and H4 / f4, to a certain extent, characterize the lens's ability to refract light. When the difference between the two is small, light symmetry in the objective lens is improved, which facilitates wide-angle performance, shortens the objective lens length, provides higher relative illumination at the edges of the field of view, and makes distortion correction easier. In some other embodiments, (H1 / f1) / (H4 / f4) can also be less than 1 or greater than 2.

[0067] Furthermore, the second lens 2 and the third lens 3 are positive-power lenses. Their primary function is to converge light. Stronger focal powers of the second lens 2 and the third lens 3 facilitate light convergence, thereby reducing the length of the objective lens and increasing wide-angle performance. Therefore, in some embodiments, the combined focal length of the second lens 2 and the third lens 3 as a group is F23, the focal length of the objective lens is f, and the objective optical system satisfies the following condition: 0.7 ≤ F23 / f ≤ 1.2. This reduces the length of the objective lens. If F23 / f is too large, the objective lens may become too long. If F23 / f is too small, aberration correction may be hindered, resulting in poor image quality. In other embodiments, where conditions permit, F23 / f may be less than 0.7, and may even be greater than 1.2.

[0068] Furthermore, in some embodiments, the object-side surface 21 of the second lens element 2 is convex; and the image-side surface 32 of the third lens element 3 is convex. This is more conducive to the symmetry of the objective optical system. In some embodiments, the second lens element 2 and the third lens element 3 can be biconvex lenses, i.e., biconvex lenses have both the object-side surface and the image-side surface 32 of the lens element 3 as convex surfaces. In some other embodiments, one of the object-side surface 21 of the second lens element 2 and the image-side surface 32 of the third lens element 3 is concave, or both are concave. In some other embodiments, one of the object-side surface 21 of the second lens element 2 and the image-side surface 32 of the third lens element 3 is convex.

[0069] Considering that excessive thickness of the first lens 1 will increase the length of the objective lens and reduce the effectiveness of the approximate symmetry of the objective lens structure, in some embodiments, the objective optical system satisfies the following condition: D11 / T1≥3.2, where D11 is the effective optical diameter of the object-side surface 11 of the first lens 1, and T1 is the center thickness of the first lens 1.

[0070] Based on the description of the above embodiment, the above embodiment will be described in more detail below in combination with more specific embodiments.

[0071] In the first embodiment, please refer to Figures 1 and 2. The left side is the object side, the right side is the image side, and IM is the image plane. From the object side to the image plane, the first lens 1, the second lens 2, the aperture 5, the third lens 3, the fourth lens 4, the filter 6, and the image sensor glass 7 are arranged in this order.

[0072] The filter 6 has an object side surface 61 and an image side surface 62, and the image sensor glass 7 has an object side surface 71 and an image side surface 72. In some embodiments, the filter 6 and the image sensor glass 7 are not required, and the objective optical system can be selected as needed to determine whether to use the filter 6 and the image sensor glass 7. Referring to Figure 1, the first lens 1 has a negative optical focal length, and its object side surface 11, i.e., the left side surface, is a plane, and the image side surface 12, i.e., the right side surface, is a concave surface. The second lens 2 has a positive optical focal length, and the object side surface 21 of the second lens 2 is a W-shaped surface, and the image side surface 22 is a convex surface. The third lens 3 has a positive optical focal length, and the third lens 3 is a biconvex lens, i.e., the object side surface 31 and the image side surface 32 of the third lens 3 are both convex surfaces. The fourth lens 4 has a negative optical focal length, and the object side surface 41 of the fourth lens 4 is a concave surface, and the image side surface 42 is a W-shaped surface.

[0073] Table 1 Structural data of the objective optical system in the first embodiment

[0074] This embodiment exhibits excellent imaging quality. Its MTF data is shown in Figure 2. Table 1 lists the curvature radius, thickness, refractive index, Abbe number, effective optical diameter, objective lens focal length f, field of view (FOV), F / F number, and total length (TTL) of each component in Example 1. Table 2 lists the aspheric surface data for each component.

[0075] Table 2 Aspheric surface data of the aspheric surface in the first embodiment

[0076] In the second embodiment, please refer to Figures 3 and 4 . The left side is the object side, the right side is the image side, and IM is the image plane. From the object side to the image plane, the first lens 1, the second lens 2, the aperture 5, the third lens 3, the fourth lens 4, the filter 6, and the image sensor glass 7 are arranged in order. In some embodiments, the filter 6 and the image sensor glass 7 are optional; whether or not the objective optical system uses the filter 6 and the image sensor glass 7 can be selected as needed. Referring to Figure 3 , the first lens 1 has negative optical power, with its object-side surface 11 (the left side) being flat and its image-side surface 12 (the right side) being concave. The second lens 2 has positive optical power, with its object-side surface 21 being a W-shaped surface and its image-side surface 22 being convex. The third lens 3 has positive optical power, with its object-side surface 31 being concave and its image-side surface 32 being convex. The fourth lens 4 has negative optical power, with its object-side surface 41 being concave and its image-side surface 42 being W-shaped.

[0077] Table 3 Structural data of the objective optical system in the second embodiment

[0078] Table 4 Aspheric surface data of the aspheric surface in the second embodiment

[0079] This embodiment exhibits excellent imaging quality. Its MTF data is shown in Figure 4. Table 3 lists the curvature radius, thickness, refractive index, Abbe number, effective optical diameter, focal length f, field of view (FOV), F / F number, and total length (TTL) of each component in Example 1. Table 4 lists the aspheric surface data for each component.

[0080] In the third embodiment, please refer to Figures 5 and 6 . The left side is the object side, the right side is the image side, and IM is the image plane. From the object side to the image plane, the first lens 1, the second lens 2, the aperture 5, the third lens 3, the fourth lens 4, the filter 6, and the image sensor glass 7 are arranged in order. In some embodiments, the filter 6 and image sensor glass 7 are optional and can be selected as needed for the objective optical system.

[0081] Table 5 Structural data of the objective optical system in the third embodiment

[0082] Table 6 Aspheric surface data of the aspheric surface in the third embodiment

[0083] Referring to FIG5 , the first lens element 1 has negative power, with its object-side surface 11 (i.e., the left side surface) being flat, and its image-side surface 12 (i.e., the right side surface) being concave. The second lens element 2 has positive power, with its object-side surface 21 being concave, and its image-side surface 22 being convex. The third lens element 3 has positive power and is a biconvex lens, i.e., both its object-side surface 31 and its image-side surface 32 being convex. The fourth lens element 4 has negative power, with its object-side surface 41 being concave, and its image-side surface 42 being a W-shaped surface.

[0084] This embodiment exhibits excellent imaging quality. Its MTF data is shown in Figure 6. Table 5 lists the curvature radius, thickness, refractive index, Abbe number, effective optical diameter, focal length f, field of view (FOV), F / F number, and total length (TTL) of each component in Example 1. Table 6 lists the aspheric surface data for each component.

[0085] In the fourth embodiment, please refer to Figures 7 and 8 . The left side is the object side, the right side is the image side, and IM is the image plane. From the object side to the image plane, the following sequence is shown: first lens 1, second lens 2, aperture 5, third lens 3, fourth lens 4, filter 6, and image sensor glass 7. In some embodiments, filter 6 and image sensor glass 7 are optional; their use in the objective optical system can be selected as needed. Referring to Figure 7 , first lens 1 has negative optical power, with its object-side surface 11 (left side) being flat and its image-side surface 12 (right side) being concave. Second lens 2 has positive optical power, with its object-side surface 21 being a W-shaped surface and its image-side surface 22 being convex. Third lens 3 has positive optical power and is a biconvex lens, with both its object-side surface 31 and image-side surface 32 being convex. Fourth lens 4 has negative optical power, with its object-side surface 41 being concave and its image-side surface 42 being W-shaped. This embodiment exhibits excellent imaging quality. Its MTF data is shown in Figure 8. Table 7 lists the curvature radius, thickness, refractive index, Abbe number, effective optical diameter, focal length f, field of view (FOV), F / F number, and total length (TTL) of each component in Example 1. Table 8 lists the aspherical surface data for each component.

[0086] Table 7 Structural data of the objective optical system in the fourth embodiment

[0087] Table 8 Aspheric surface data of the aspheric surface in the fourth embodiment

[0088] In the fifth embodiment, referring to Figures 9 and 10 , the left side is the object side, the right side is the image side, and IM is the image plane. From the object side to the image plane, the first lens 1, the second lens 2, the aperture 5, the third lens 3, the fourth lens 4, the filter 6, and the image sensor glass 7 are arranged in order. In some embodiments, the filter 6 and the image sensor glass 7 are optional and can be selected as needed for the objective optical system.

[0089] Table 9 Structural data of the objective optical system in the fifth embodiment

[0090] Referring to FIG9 , the first lens element 1 has negative power, with its object-side surface 11 (i.e., its left side surface) being flat, and its image-side surface 12 (i.e., its right side surface) being concave. The second lens element 2 has positive power, with its object-side surface 21 being a W-shaped surface, and its image-side surface 22 being a convex surface. The third lens element 3 has positive power, with its object-side surface 31 being concave, and its image-side surface 32 being convex. The fourth lens element 4 has negative power, with its object-side surface 41 being concave, and its image-side surface 42 being a W-shaped surface.

[0091] This embodiment exhibits excellent imaging quality. Its MTF data is shown in Figure 10. Table 9 lists the curvature radius, thickness, refractive index, Abbe number, effective optical diameter, focal length f, field of view (FOV), F / F number, and total length (TTL) of each component in Example 1. Table 10 lists the aspheric surface data for each component.

[0092] Table 10 Aspheric surface data of the aspheric surface in the fifth embodiment

[0093] In the sixth embodiment, please refer to FIG. 11 and FIG. 12 , the left side is the object side, the right side is the image side, and IM is the image plane.

[0094] Table 11 Structural data of the objective optical system in the sixth embodiment

[0095] From the object side to the image plane, the first lens 1, the second lens 2, the aperture 5, the third lens 3, the fourth lens 4, the filter 6, and the image sensor glass 7 are arranged in order. In some embodiments, the filter 6 and the image sensor glass 7 are not required, and the use of the filter 6 and the image sensor glass 7 in the objective optical system can be selected as needed.

[0096] Table 12 Aspheric surface data of the aspheric surface in the sixth embodiment

[0097] Please refer to Figure 11. The first lens 1 has negative optical power, with its object side surface 11 (left side) being a flat surface and its image side surface 12 (right side) being a concave surface. The second lens 2 has positive optical power and is a biconvex lens, i.e., both the object side surface 21 and the image side surface 22 of the second lens 2 are convex surfaces. The third lens 3 has positive optical power and is a biconvex lens, i.e., both the object side surface 31 and the image side surface 32 of the third lens 3 are convex surfaces. The fourth lens 4 has negative optical power, with the object side surface 41 of the fourth lens 4 being a concave surface and the image side surface being a W-shaped surface. The imaging quality of this embodiment is good, and its MTF data is shown in Figure 12. Table 11 lists the data of the curvature radius, thickness, refractive index, Abbe number, effective optical diameter, focal length f of the objective lens, field of view angle FOV, F / number, and total length TTL of each element in Example 1. Table 12 lists the aspheric surface data of each element.

[0098] In the seventh embodiment, please refer to Figures 13 and 14 . The left side is the object side, the right side is the image side, and IM is the image plane. From the object side to the image plane, the first lens 1, the second lens 2, the aperture 5, the third lens 3, the fourth lens 4, the filter 6, and the image sensor glass 7 are arranged in order. In some embodiments, the filter 6 and the image sensor glass 7 are optional; the use of the filter 6 and the image sensor glass 7 in the objective optical system can be selected as needed. Referring to Figure 13 , the first lens 1 has negative optical power, with its object-side surface 11 (the left side) being flat and its image-side surface 12 (the right side) being concave. The second lens 2 has positive optical power and is a biconvex lens, meaning that both its object-side surface 21 and image-side surface 22 are convex. The third lens 3 has positive optical power and is a biconvex lens, meaning that both its object-side surface 31 and image-side surface 32 are convex. The fourth lens 4 has negative optical power, with its object-side surface 41 being concave and its image-side surface 42 being W-shaped. This embodiment exhibits excellent imaging quality. Its MTF data is shown in Figure 14. Table 13 lists the curvature radius, thickness, refractive index, Abbe number, effective optical diameter, objective lens focal length f, field of view (FOV), F / F number, and total length (TTL) of each component in Example 1. Table 14 lists the aspheric surface data for each component.

[0099] Table 13 Structural data of the objective optical system in the seventh embodiment

[0100] Table 14 Aspheric surface data of the aspheric surface in the seventh embodiment

[0101] In the eighth embodiment, please refer to Figures 15 and 16 . The left side is the object side, the right side is the image side, and IM is the image plane. From the object side to the image plane, the first lens 1, the second lens 2, the aperture 5, the third lens 3, the fourth lens 4, the filter 6, and the image sensor glass 7 are arranged in order. In some embodiments, the filter 6 and the image sensor glass 7 are optional; the use of the filter 6 and the image sensor glass 7 in the objective optical system can be selected as needed. Referring to Figure 15 , the first lens 1 has negative optical power, with its object-side surface 11 (i.e., the left side) being flat and its image-side surface 12 (i.e., the right side) being concave. The second lens 2 has positive optical power and is a biconvex lens, i.e., both its object-side surface 21 and image-side surface 22 are convex. The third lens 3 has positive optical power and is a biconvex lens, i.e., both its object-side surface 31 and image-side surface 32 are convex. The fourth lens 4 has negative optical power, with its object-side surface 41 being concave and its image-side surface 42 being a W-shaped surface. The imaging quality of this embodiment is good. Please refer to FIG16 for its MTF data.

[0102] Table 15 Structural data of the objective optical system in the eighth embodiment

[0103] Table 16 Aspheric surface data of the aspheric surface in the eighth embodiment

[0104] Table 15 lists the data of the curvature radius, thickness, refractive index, Abbe number, effective optical diameter, focal length f of the objective lens, field of view angle FOV, F / number and total length TTL of each component in Example 1. Table 16 lists the aspherical surface data of each component.

[0105] In the ninth embodiment, referring to Figures 17 and 18 , the left side is the object side, the right side is the image side, and IM is the image plane. From the object side to the image plane, the first lens 1, the second lens 2, the aperture 5, the third lens 3, the fourth lens 4, the filter 6, and the image sensor glass 7 are arranged in order. In some embodiments, the filter 6 and the image sensor glass 7 are optional and can be selected as needed for the objective optical system.

[0106] Table 17 Structural data of the objective optical system in the ninth embodiment

[0107] Table 18 Aspheric surface data of the aspheric surface in the ninth embodiment

[0108] Referring to Figure 17 , the first lens 1 has negative optical power, with its object-side surface 11 (left side) being convex and its image-side surface 12 (right side) being concave. The second lens 2 has positive optical power and is a biconvex lens, meaning both its object-side surface 21 and image-side surface 22 are convex. The third lens 3 has positive optical power and is a biconvex lens, meaning both its object-side surface 31 and image-side surface 32 are convex. The fourth lens 4 has negative optical power, with its object-side surface 41 being concave and its image-side surface 42 being convex. This embodiment exhibits excellent imaging quality, as shown in Figure 18 for its MTF data. Table 17 lists the curvature radius, thickness, refractive index, Abbe number, effective optical diameter, focal length f, field of view (FOV), F / number, and total length (TTL) of each element in Example 1. Table 18 lists the aspheric surface data for each element.

[0109] The endoscope objective optical systems described in Examples 1 to 9 meet the data in Table 19 below. In some other embodiments, in addition to the data provided in Table 19, the endoscope objective optical system may also adopt any other feasible parameters while meeting the requirements. For example, in some other embodiments, D11 / imgH may be less than or equal to 1, and in some other embodiments, D11 / imgH may be greater than or equal to 1.34. In some other embodiments, (H1 / f1) / (H4 / f4) may be greater than 2. In some other embodiments, other parameters of the endoscope objective optical system, such as f, FOV, imgH, TTL, etc., may also be adjusted as needed while meeting the requirements.

[0110] Table 19 Data of endoscope objective optical system

[0111] In some embodiments of the endoscope, the endoscope includes an endoscope objective as described in any of the embodiments above.

[0112] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. Those skilled in the art can make several simple deductions, modifications or substitutions based on the concept of the present invention.

Claims

1. An endoscope objective lens, characterized in that: An objective optical system is included, wherein the objective optical system includes: A first lens, wherein the first lens has negative optical power, and a portion of an image-side surface of the first lens close to the optical axis and away from an edge of the first lens is a concave surface; a second lens having positive optical power; Aperture; a third lens having positive optical power; a fourth lens having negative optical power, wherein a portion of an object-side surface of the fourth lens close to the optical axis and away from an edge of the fourth lens is a concave surface; The first lens, the second lens, the aperture, the third lens and the fourth lens are arranged in sequence from the image side to the object side along the optical axis; A chief ray height h11 on the object side surface of the first lens and a chief ray height h42 on the image side surface of the fourth lens satisfy: 0.65≤h11 / h42≤1.35, and / or an effective optical diameter D11 on the object side surface of the first lens and an effective optical diameter D42 on the image side surface of the fourth lens satisfy: 0.75≤D11 / D42≤1.

25.

2. The endoscope objective lens according to claim 1, characterized in that A chief ray height h11 on the object-side surface of the first lens and a chief ray height h42 on the image-side surface of the fourth lens satisfy: 0.8≤h11 / h42≤1.

2.

3. The endoscope objective lens according to claim 1, characterized in that: An effective optical diameter D11 of the object-side surface of the first lens and an effective optical diameter D42 of the image-side surface of the fourth lens satisfy: 0.85≤D11 / D42≤1.

15.

4. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: An effective optical diameter D11 of the object side surface of the first lens and an imaging height imgH of the objective optical system satisfy: 0.8≤D11 / imgH≤1.

42.

5. The endoscope objective lens according to claim 4, characterized in that An effective optical diameter D11 of the object side surface of the first lens and an imaging height imgH of the objective optical system satisfy: 1.00≤D11 / imgH≤1.

40.

6. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The chief ray heights of the two surface edge fields of view of the first lens are h11 and h12 respectively, the average of h11 and h12 is H1, the focal length of the first lens is f1, the chief ray heights of the two surface edge fields of view of the fourth lens are h41 and h42 respectively, the average of h41 and h42 is H4, and the focal length of the fourth lens is f4, then the objective optical system satisfies: 1≤(H1 / f1) / (H4 / f4)≤2.

7. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The combined focal length of the second lens and the third lens as a group of lenses is F23, and the focal length of the objective optical system is f, then the objective optical system satisfies: 0.7≤F23 / f≤1.

2.

8. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The object side surface of the second lens is a convex surface; the image side surface of the third lens is a convex surface.

9. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The number of lenses having optical power in the objective optical system is four.

10. An endoscope, comprising the endoscope objective lens according to any one of claims 1 to 9.

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